diff --git a/.cruft.json b/.cruft.json
index e3324c6..1292e75 100644
--- a/.cruft.json
+++ b/.cruft.json
@@ -1,6 +1,6 @@
 {
   "template": "https://github.com/sphinx-notes/template",
-  "commit": "80a61fa9abcd9474d8cfbc36d0bf5d41f99c916c",
+  "commit": "0b096cd7ecff1b28ee8c2887ba3321418be34b9a",
   "checkout": null,
   "context": {
     "cookiecutter": {
@@ -14,7 +14,8 @@
       "github_repo": "snippet",
       "pypi_name": "sphinxnotes-snippet",
       "pypi_owner": "SilverRainZ",
-      "_template": "https://github.com/sphinx-notes/template"
+      "_template": "https://github.com/sphinx-notes/template",
+      "_commit": "0b096cd7ecff1b28ee8c2887ba3321418be34b9a"
     }
   },
   "directory": null
diff --git a/.github/workflows/pages.yml b/.github/workflows/pages.yml
index 4b60562..0cf70c8 100644
--- a/.github/workflows/pages.yml
+++ b/.github/workflows/pages.yml
@@ -13,7 +13,7 @@ concurrency:
 
 jobs:
   pages:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
diff --git a/Makefile b/Makefile
index d1f5d08..c2786f4 100644
--- a/Makefile
+++ b/Makefile
@@ -21,8 +21,8 @@ view:
 
 .PHONY: clean
 clean:
-	$(MAKE) -C docs/ clean
-	$(RM) dist/
+	$(MAKE) -C docs/ clean | true
+	$(RM) dist/ | true
 
 .PHONY: clean
 fmt:
diff --git a/docs/_templates/confval.rst b/docs/_templates/confval.rst
deleted file mode 100644
index fbbaa4c..0000000
--- a/docs/_templates/confval.rst
+++ /dev/null
@@ -1,11 +0,0 @@
-
-:Type: :py:class:`{{ type }}`
-:Default: ``{{ default }}``
-{% if choice %}:Choices: {% for c in choice %}``{{ c }}`` {% endfor %}{% endif %}
-{% if versionadded %}:Version added: :version:`{{ versionadded }}`{% endif %}
-{% if versionchanged %}:Version changed:{% for i in range(0, versionchanged|count -1, 2)  %}
-   :version:`{{ versionchanged[i] }}`
-      {{ versionchanged[i+1] }}{% endfor %}{% endif %}
-
-{{ content }}
-
diff --git a/docs/_templates/example.rst b/docs/_templates/example.rst
deleted file mode 100644
index 18093e6..0000000
--- a/docs/_templates/example.rst
+++ /dev/null
@@ -1,31 +0,0 @@
-
-{% if style is not defined or style == 'tab' %}
-.. tab-set::
-
-   .. tab-item:: Result
-
-      {% for line in content %}{{ line }}
-      {% endfor %}
-
-   .. tab-item:: reStructuredText
-
-      .. code:: rst
-
-         {% for line in content %}{{ line }}
-         {% endfor %}
-{% elif style == 'grid'  %}
-.. grid:: 2
-
-   .. grid-item-card::  reStructuredText
-
-      .. code:: rst
-
-         {% for line in content %}{{ line }}
-         {% endfor %}
-
-   .. grid-item-card:: Result
-
-      {% for line in content %}{{ line }}
-      {% endfor %}
-{% endif %}
-
diff --git a/docs/_templates/version.rst b/docs/_templates/version.rst
deleted file mode 100644
index eac376e..0000000
--- a/docs/_templates/version.rst
+++ /dev/null
@@ -1,8 +0,0 @@
-
-:Date: :ref:`📅{{ date }} <any-version.date>`
-:Download: :tag:`{{ title }}`
-
-{% for line in content %}
-{{ line }}
-{% endfor %}
-
diff --git a/docs/conf.py b/docs/conf.py
index c7d27b2..18d2567 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -74,49 +74,6 @@
 
 # -- Extensions -------------------------------------------------------------
 
-#  
-extensions.append('sphinxnotes.any')
-from sphinxnotes.any import Schema, Field as F
-#
-version_schema = Schema('version',
-                        name=F(unique=True, referenceable=True, required=True, form=F.Form.LINES),
-                        attrs={'date': F(referenceable=True)},
-                        content=F(form=F.Form.LINES),
-                        description_template=open('_templates/version.rst', 'r').read(),
-                        reference_template='🏷️{{ title }}',
-                        missing_reference_template='🏷️{{ title }}',
-                        ambiguous_reference_template='🏷️{{ title }}')
-confval_schema = Schema('confval',
-                        name=F(unique=True, referenceable=True, required=True, form=F.Form.LINES),
-                        attrs={
-                            'type': F(),
-                            'default': F(),
-                            'choice': F(form=F.Form.WORDS),
-                            'versionadded': F(),
-                            'versionchanged': F(form=F.Form.LINES),
-                        },
-                        content=F(),
-                        description_template=open('_templates/confval.rst', 'r').read(),
-                        reference_template='⚙️{{ title }}',
-                        missing_reference_template='⚙️{{ title }}',
-                        ambiguous_reference_template='⚙️{{ title }}')
-example_schema = Schema('example',
-                        name=F(referenceable=True),
-                        attrs={'style': F()},
-                        content=F(form=F.Form.LINES),
-                        description_template=open('_templates/example.rst', 'r').read(),
-                        reference_template='📝{{ title }}',
-                        missing_reference_template='📝{{ title }}',
-                        ambiguous_reference_template='📝{{ title }}')
-#
-any_schemas = [
-    version_schema,
-    confval_schema,
-    example_schema,
-]
-primary_domain = 'any'
-# 
-
 extensions.append('sphinx.ext.extlinks')
 extlinks = {
     'issue': ('https://github.com/sphinx-notes/snippet/issues/%s', '💬%s'),
@@ -138,21 +95,21 @@
     'jinja': ('https://jinja.palletsprojects.com/en/latest/', None),
 }
 
-# 
 extensions.append('sphinxnotes.comboroles')
 comboroles_roles = {
     'parsed_literal': (['literal'], True),
 }
-#
 
-#
+extensions.append('sphinxnotes.project')
+primary_domain = 'any'
+
 # -- Eat your own dog food --------------------------------------------------
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 sys.path.insert(0, os.path.abspath('../src/sphinxnotes'))
-extensions.append('snippet.ext')
+extensions.append('snippet')
 
 # DOG FOOD CONFIGURATION START
 
@@ -163,4 +120,3 @@
 extensions.append('sphinxcontrib.asciinema')
 
 # DOG FOOD CONFIGURATION END
-#
diff --git a/docs/index.rst b/docs/index.rst
index b2f2962..c5067de 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -5,7 +5,7 @@
 sphinxnotes-snippet
 ===================
 
-.. |docs| image:: https://img.shields.io/github/deployments/sphinx-notes/snippet/github-pages
+.. |docs| image:: https://img.shields.io/github/deployments/sphinx-notes/snippet/github-pages?label=docs
    :target: https://sphinx.silverrainz.me/snippet
    :alt: Documentation Status
 
@@ -21,7 +21,11 @@ sphinxnotes-snippet
    :target: https://pypi.python.org/pypi/sphinxnotes-snippet
    :alt: PyPI Package Downloads
 
-|docs| |license| |pypi| |download|
+.. |github| image:: https://img.shields.io/badge/GitHub-181717?style=flat&logo=github&logoColor=white/
+   :target: https://github.com/sphinx-notes/snippet
+   :alt: GitHub Repository
+
+|docs| |license| |pypi| |download| |github|
 
 Introduction
 ============
diff --git a/pyproject.toml b/pyproject.toml
index c64582d..97c091c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
     "Topic :: Utilities",
 ]
 
-requires-python = ">=3.8"
+requires-python = ">=3.12"
 dependencies = [
     "Sphinx >= 4",
     "langid",
@@ -55,7 +55,7 @@ test = [
 ]
 docs = [
     "furo",
-    "sphinxnotes-any",
+    "sphinxnotes-project",
     "sphinx_design",
     "sphinx_copybutton",
     "sphinxcontrib-gtagjs",
diff --git a/src/sphinxnotes/snippet/__init__.py b/src/sphinxnotes/snippet/__init__.py
index 042d354..0fd7955 100644
--- a/src/sphinxnotes/snippet/__init__.py
+++ b/src/sphinxnotes/snippet/__init__.py
@@ -2,185 +2,35 @@
 sphinxnotes.snippet
 ~~~~~~~~~~~~~~~~~~~
 
-:copyright: Copyright 2020 Shengyu Zhang
+Sphinx extension entrypoint.
+
+:copyright: Copyright 2024 Shengyu Zhang
 :license: BSD, see LICENSE for details.
 """
 
-from __future__ import annotations
-from typing import List, Tuple, Optional, TYPE_CHECKING
-import itertools
-
-from docutils import nodes
-
-if TYPE_CHECKING:
-    from sphinx.environment import BuildEnvironment
-
-__version__ = '1.1.1'
-
-
-class Snippet(object):
-    """
-    Snippet is base class of reStructuredText snippet.
-
-    :param nodes: Document nodes that make up this snippet
-    """
-
-    #: docname where the snippet is located, can be referenced by
-    # :rst:role:`doc`.
-    docname: str
-
-    #: Source file path of snippet
-    file: str
-
-    #: Line number range of snippet, in the source file which is left closed
-    #: and right opened.
-    lineno: Tuple[int, int]
-
-    #: The original reStructuredText of snippet
-    rst: List[str]
-
-    #: The possible identifier key of snippet, which is picked from nodes'
-    #: (or nodes' parent's) `ids attr`_.
-    #:
-    #: .. _ids attr: https://docutils.sourceforge.io/docs/ref/doctree.html#ids
-    refid: Optional[str]
-
-    def __init__(self, *nodes: nodes.Node) -> None:
-        assert len(nodes) != 0
-
-        env: BuildEnvironment = nodes[0].document.settings.env
-        self.file = nodes[0].source
-        self.docname = env.path2doc(self.file)
-
-        lineno = [float('inf'), -float('inf')]
-        for node in nodes:
-            if not node.line:
-                continue  # Skip node that have None line, I dont know why
-            lineno[0] = min(lineno[0], _line_of_start(node))
-            lineno[1] = max(lineno[1], _line_of_end(node))
-        self.lineno = lineno
-
-        lines = []
-        with open(self.file, 'r') as f:
-            start = self.lineno[0] - 1
-            stop = self.lineno[1] - 1
-            for line in itertools.islice(f, start, stop):
-                lines.append(line.strip('\n'))
-        self.rst = lines
-
-        # Find exactly one ID attr in nodes
-        self.refid = None
-        for node in nodes:
-            if node['ids']:
-                self.refid = node['ids'][0]
-                break
-
-        # If no ID found, try parent
-        if not self.refid:
-            for node in nodes:
-                if node.parent['ids']:
-                    self.refid = node.parent['ids'][0]
-                    break
-
-
-class Text(Snippet):
-    #: Text of snippet
-    text: str
-
-    def __init__(self, node: nodes.Node) -> None:
-        super().__init__(node)
-        self.text = node.astext()
-
-
-class CodeBlock(Text):
-    #: Language of code block
-    language: str
-    #: Caption of code block
-    caption: Optional[str]
-
-    def __init__(self, node: nodes.literal_block) -> None:
-        assert isinstance(node, nodes.literal_block)
-        super().__init__(node)
-        self.language = node['language']
-        self.caption = node.get('caption')
-
-
-class WithCodeBlock(object):
-    code_blocks: List[CodeBlock]
-
-    def __init__(self, nodes: nodes.Nodes) -> None:
-        self.code_blocks = []
-        for n in nodes.traverse(nodes.literal_block):
-            self.code_blocks.append(self.CodeBlock(n))
-
-
-class Title(Text):
-    def __init__(self, node: nodes.title) -> None:
-        assert isinstance(node, nodes.title)
-        super().__init__(node)
-
-
-class WithTitle(object):
-    title: Optional[Title]
-
-    def __init__(self, node: nodes.Node) -> None:
-        title_node = node.next_node(nodes.title)
-        self.title = Title(title_node) if title_node else None
-
-
-class Section(Snippet, WithTitle):
-    def __init__(self, node: nodes.section) -> None:
-        assert isinstance(node, nodes.section)
-        Snippet.__init__(self, node)
-        WithTitle.__init__(self, node)
-
-
-class Document(Section):
-    def __init__(self, node: nodes.document) -> None:
-        assert isinstance(node, nodes.document)
-        super().__init__(node.next_node(nodes.section))
-
-
-################
-# Nodes helper #
-################
-
-
-def _line_of_start(node: nodes.Node) -> int:
-    assert node.line
-    if isinstance(node, nodes.title):
-        if isinstance(node.parent.parent, nodes.document):
-            # Spceial case for Document Title / Subtitle
-            return 1
-        else:
-            # Spceial case for section title
-            return node.line - 1
-    elif isinstance(node, nodes.section):
-        if isinstance(node.parent, nodes.document):
-            # Spceial case for top level section
-            return 1
-        else:
-            # Spceial case for section
-            return node.line - 1
-    return node.line
-
 
-def _line_of_end(node: nodes.Node) -> Optional[int]:
-    next_node = node.next_node(descend=False, siblings=True, ascend=True)
-    while next_node:
-        if next_node.line:
-            return _line_of_start(next_node)
-        next_node = next_node.next_node(
-            # Some nodes' line attr is always None, but their children has
-            # valid line attr
-            descend=True,
-            # If node and its children have not valid line attr, try use line
-            # of next node
-            ascend=True,
-            siblings=True,
-        )
-    # No line found, return the max line of source file
-    if node.source:
-        with open(node.source) as f:
-            return sum(1 for line in f)
-    raise AttributeError('None source attr of node %s' % node)
+def setup(app):
+    # **WARNING**: We don't import these packages globally, because the current
+    # package (sphinxnotes.snippet) is always resloved when importing
+    # sphinxnotes.snippet.*. If we import packages here, eventually we will
+    # load a lot of packages from the Sphinx. It will seriously **SLOW DOWN**
+    # the startup time of our CLI tool (sphinxnotes.snippet.cli).
+    #
+    # .. seealso:: https://github.com/sphinx-notes/snippet/pull/31
+    from .ext import (
+        SnippetBuilder,
+        on_config_inited,
+        on_env_get_outdated,
+        on_doctree_resolved,
+        on_builder_finished,
+    )
+
+    app.add_builder(SnippetBuilder)
+
+    app.add_config_value('snippet_config', {}, '')
+    app.add_config_value('snippet_patterns', {'*': ['.*']}, '')
+
+    app.connect('config-inited', on_config_inited)
+    app.connect('env-get-outdated', on_env_get_outdated)
+    app.connect('doctree-resolved', on_doctree_resolved)
+    app.connect('build-finished', on_builder_finished)
diff --git a/src/sphinxnotes/snippet/cache.py b/src/sphinxnotes/snippet/cache.py
index 5c5c4e3..78a2efa 100644
--- a/src/sphinxnotes/snippet/cache.py
+++ b/src/sphinxnotes/snippet/cache.py
@@ -1,4 +1,5 @@
-"""sphinxnotes.snippet.cache
+"""
+sphinxnotes.snippet.cache
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 :copyright: Copyright 2021 Shengyu Zhang
@@ -6,10 +7,9 @@
 """
 
 from __future__ import annotations
-from typing import List, Tuple, Dict, Optional
 from dataclasses import dataclass
 
-from . import Snippet
+from .snippets import Snippet
 from .utils.pdict import PDict
 
 
@@ -18,25 +18,25 @@ class Item(object):
     """Item of snippet cache."""
 
     snippet: Snippet
-    tags: List[str]
+    tags: str
     excerpt: str
-    titlepath: List[str]
-    keywords: List[str]
+    titlepath: list[str]
+    keywords: list[str]
 
 
-DocID = Tuple[str, str]  # (project, docname)
+DocID = tuple[str, str]  # (project, docname)
 IndexID = str  # UUID
-Index = Tuple[str, str, List[str], List[str]]  # (tags, excerpt, titlepath, keywords)
+Index = tuple[str, str, list[str], list[str]]  # (tags, excerpt, titlepath, keywords)
 
 
-class Cache(PDict):
-    """A DocID -> List[Item] Cache."""
+class Cache(PDict[DocID, list[Item]]):
+    """A DocID -> list[Item] Cache."""
 
-    indexes: Dict[IndexID, Index]
-    index_id_to_doc_id: Dict[IndexID, Tuple[DocID, int]]
-    doc_id_to_index_ids: Dict[DocID, List[IndexID]]
-    num_snippets_by_project: Dict[str, int]
-    num_snippets_by_docid: Dict[DocID, int]
+    indexes: dict[IndexID, Index]
+    index_id_to_doc_id: dict[IndexID, tuple[DocID, int]]
+    doc_id_to_index_ids: dict[DocID, list[IndexID]]
+    num_snippets_by_project: dict[str, int]
+    num_snippets_by_docid: dict[DocID, int]
 
     def __init__(self, dirname: str) -> None:
         self.indexes = {}
@@ -46,7 +46,7 @@ def __init__(self, dirname: str) -> None:
         self.num_snippets_by_docid = {}
         super().__init__(dirname)
 
-    def post_dump(self, key: DocID, items: List[Item]) -> None:
+    def post_dump(self, key: DocID, value: list[Item]) -> None:
         """Overwrite PDict.post_dump."""
 
         # Remove old indexes and index IDs if exists
@@ -55,7 +55,7 @@ def post_dump(self, key: DocID, items: List[Item]) -> None:
             del self.indexes[old_index_id]
 
         # Add new index to every where
-        for i, item in enumerate(items):
+        for i, item in enumerate(value):
             index_id = self.gen_index_id()
             self.indexes[index_id] = (
                 item.tags,
@@ -69,12 +69,12 @@ def post_dump(self, key: DocID, items: List[Item]) -> None:
         # Update statistic
         if key[0] not in self.num_snippets_by_project:
             self.num_snippets_by_project[key[0]] = 0
-        self.num_snippets_by_project[key[0]] += len(items)
+        self.num_snippets_by_project[key[0]] += len(value)
         if key not in self.num_snippets_by_docid:
             self.num_snippets_by_docid[key] = 0
-        self.num_snippets_by_docid[key] += len(items)
+        self.num_snippets_by_docid[key] += len(value)
 
-    def post_purge(self, key: DocID, items: List[Item]) -> None:
+    def post_purge(self, key: DocID, value: list[Item]) -> None:
         """Overwrite PDict.post_purge."""
 
         # Purge indexes
@@ -83,17 +83,17 @@ def post_purge(self, key: DocID, items: List[Item]) -> None:
             del self.indexes[index_id]
 
         # Update statistic
-        self.num_snippets_by_project[key[0]] -= len(items)
+        self.num_snippets_by_project[key[0]] -= len(value)
         if self.num_snippets_by_project[key[0]] == 0:
             del self.num_snippets_by_project[key[0]]
-        self.num_snippets_by_docid[key] -= len(items)
+        self.num_snippets_by_docid[key] -= len(value)
         if self.num_snippets_by_docid[key] == 0:
             del self.num_snippets_by_docid[key]
 
-    def get_by_index_id(self, key: IndexID) -> Optional[Item]:
+    def get_by_index_id(self, key: IndexID) -> Item | None:
         """Like get(), but use IndexID as key."""
         doc_id, item_index = self.index_id_to_doc_id.get(key, (None, None))
-        if not doc_id:
+        if not doc_id or item_index is None:
             return None
         return self[doc_id][item_index]
 
@@ -103,6 +103,6 @@ def gen_index_id(self) -> str:
 
         return uuid.uuid4().hex[:7]
 
-    def stringify(self, key: DocID, items: List[Item]) -> str:
+    def stringify(self, key: DocID, value: list[Item]) -> str:
         """Overwrite PDict.stringify."""
-        return key[1]
+        return key[1]  # docname
diff --git a/src/sphinxnotes/snippet/cli.py b/src/sphinxnotes/snippet/cli.py
index dcc732f..a52b17a 100644
--- a/src/sphinxnotes/snippet/cli.py
+++ b/src/sphinxnotes/snippet/cli.py
@@ -2,24 +2,30 @@
 sphinxnotes.snippet.cli
 ~~~~~~~~~~~~~~~~~~~~~~~
 
-:copyright: Copyright 2020 Shengyu Zhang
+Command line entrypoint.
+
+:copyright: Copyright 2024 Shengyu Zhang
 :license: BSD, see LICENSE for details.
 """
 
+# **NOTE**: Import new packages with caution:
+# Importing complex packages (like sphinx.*) will directly slow down the
+# startup of the CLI tool.
 from __future__ import annotations
 import sys
-import argparse
-from typing import List
+import os
 from os import path
+import argparse
+from typing import Iterable
 from textwrap import dedent
 from shutil import get_terminal_size
 import posixpath
 
 from xdg.BaseDirectory import xdg_config_home
 
-from . import __version__
+from .snippets import Document
 from .config import Config
-from .cache import Cache
+from .cache import Cache, IndexID, Index
 from .table import tablify, COLUMNS
 
 DEFAULT_CONFIG_FILE = path.join(xdg_config_home, 'sphinxnotes', 'snippet', 'conf.py')
@@ -38,14 +44,14 @@ def get_integration_file(fn: str) -> str:
     .. seealso::
 
        see ``[tool.setuptools.package-data]`` section of pyproject.toml to know
-        how files are included.
+       how files are included.
     """
     # TODO: use https://docs.python.org/3/library/importlib.resources.html#importlib.resources.files
     prefix = path.abspath(path.dirname(__file__))
     return path.join(prefix, 'integration', fn)
 
 
-def main(argv: List[str] = sys.argv[1:]):
+def main(argv: list[str] = sys.argv[1:]):
     """Command line entrypoint."""
 
     parser = argparse.ArgumentParser(
@@ -54,13 +60,17 @@ def main(argv: List[str] = sys.argv[1:]):
         formatter_class=HelpFormatter,
         epilog=dedent("""
                                      snippet tags:
-                                       d (document)          a reST document 
-                                       s (section)           a reST section
-                                       c (code)              snippet with code blocks
+                                       d (document)          a document
+                                       s (section)           a section
+                                       c (code)              a code block
                                        * (any)               wildcard for any snippet"""),
     )
     parser.add_argument(
-        '-v', '--version', action='version', version='%(prog)s ' + __version__
+        '--version',
+        # add_argument provides action='version', but it requires a version
+        # literal and doesn't support lazily obtaining version.
+        action='store_true',
+        help="show program's version number and exit",
     )
     parser.add_argument(
         '-c', '--config', default=DEFAULT_CONFIG_FILE, help='path to configuration file'
@@ -83,7 +93,14 @@ def main(argv: List[str] = sys.argv[1:]):
         help='list snippet indexes, columns of indexes: %s' % COLUMNS,
     )
     listparser.add_argument(
-        '--tags', '-t', type=str, default='*', help='list specified tags only'
+        '--tags', '-t', type=str, default='*', help='list snippets with specified tags'
+    )
+    listparser.add_argument(
+        '--docname',
+        '-d',
+        type=str,
+        default='**',
+        help='list snippets whose docname matches shell-style glob pattern',
     )
     listparser.add_argument(
         '--width',
@@ -106,6 +123,9 @@ def main(argv: List[str] = sys.argv[1:]):
     getparser.add_argument(
         '--file', '-f', action='store_true', help='get source file path of snippet'
     )
+    getparser.add_argument(
+        '--deps', action='store_true', help='get dependent files of document'
+    )
     getparser.add_argument(
         '--line-start',
         action='store_true',
@@ -120,7 +140,12 @@ def main(argv: List[str] = sys.argv[1:]):
         '--text',
         '-t',
         action='store_true',
-        help='get source reStructuredText of snippet',
+        help='get text representation of snippet',
+    )
+    getparser.add_argument(
+        '--src',
+        action='store_true',
+        help='get source text of snippet',
     )
     getparser.add_argument(
         '--url',
@@ -165,6 +190,16 @@ def main(argv: List[str] = sys.argv[1:]):
     # Parse command line arguments
     args = parser.parse_args(argv)
 
+    # Print version message.
+    # See parser.add_argument('--version', ...) for more detais.
+    if args.version:
+        # NOTE: Importing is slow, do it on demand.
+        from importlib.metadata import version
+
+        pkgname = 'sphinxnotes.snippet'
+        print(pkgname, version(pkgname))
+        parser.exit()
+
     # Load config from file
     if args.config == DEFAULT_CONFIG_FILE and not path.isfile(DEFAULT_CONFIG_FILE):
         print(
@@ -205,24 +240,62 @@ def _on_command_stat(args: argparse.Namespace):
         print(f'\t {v} snippets(s)')
 
 
+def _filter_list_items(
+    cache: Cache, tags: str, docname_glob: str
+) -> Iterable[tuple[IndexID, Index]]:
+    # NOTE: Importing is slow, do it on demand.
+    from sphinx.util.matching import patmatch
+
+    for index_id, index in cache.indexes.items():
+        # Filter by tags.
+        if index[0] not in tags and '*' not in tags:
+            continue
+        # Filter by docname.
+        (_, docname), _ = cache.index_id_to_doc_id[index_id]
+        if not patmatch(docname, docname_glob):
+            continue
+        yield (index_id, index)
+
+
 def _on_command_list(args: argparse.Namespace):
-    rows = tablify(args.cache.indexes, args.tags, args.width)
-    for row in rows:
+    items = _filter_list_items(args.cache, args.tags, args.docname)
+    for row in tablify(items, args.width):
         print(row)
 
 
 def _on_command_get(args: argparse.Namespace):
+    # Wrapper for warning when nothing is printed
+    printed = False
+
+    def p(*args, **opts):
+        nonlocal printed
+        printed = True
+        print(*args, **opts)
+
     for index_id in args.index_id:
         item = args.cache.get_by_index_id(index_id)
         if not item:
-            print('no such index ID', file=sys.stderr)
+            p('no such index ID', file=sys.stderr)
             sys.exit(1)
         if args.text:
-            print('\n'.join(item.snippet.rst))
+            p('\n'.join(item.snippet.text))
+        if args.src:
+            p('\n'.join(item.snippet.source))
         if args.docname:
-            print(item.snippet.docname)
+            p(item.snippet.docname)
         if args.file:
-            print(item.snippet.file)
+            p(item.snippet.file)
+        if args.deps:
+            if not isinstance(item.snippet, Document):
+                print(
+                    f'{type(item.snippet)} ({index_id}) is not a document',
+                    file=sys.stderr,
+                )
+                sys.exit(1)
+            if len(item.snippet.deps) == 0:
+                p('')  # prevent print nothing warning
+            for dep in item.snippet.deps:
+                p(dep)
         if args.url:
             # HACK: get doc id in better way
             doc_id, _ = args.cache.index_id_to_doc_id.get(index_id)
@@ -236,11 +309,15 @@ def _on_command_get(args: argparse.Namespace):
             url = posixpath.join(base_url, doc_id[1] + '.html')
             if item.snippet.refid:
                 url += '#' + item.snippet.refid
-            print(url)
+            p(url)
         if args.line_start:
-            print(item.snippet.lineno[0])
+            p(item.snippet.lineno[0])
         if args.line_end:
-            print(item.snippet.lineno[1])
+            p(item.snippet.lineno[1])
+
+        if not printed:
+            print('please specify at least one argument', file=sys.stderr)
+            sys.exit(1)
 
 
 def _on_command_integration(args: argparse.Namespace):
@@ -275,4 +352,13 @@ def _on_command_integration(args: argparse.Namespace):
 
 
 if __name__ == '__main__':
-    sys.exit(main())
+    # Prevent "[Errno 32] Broken pipe" error.
+    # https://docs.python.org/3/library/signal.html#note-on-sigpipe
+    try:
+        sys.exit(main())
+    except BrokenPipeError:
+        # Python flushes standard streams on exit; redirect remaining output
+        # to devnull to avoid another BrokenPipeError at shutdown.
+        devnull = os.open(os.devnull, os.O_WRONLY)
+        os.dup2(devnull, sys.stdout.fileno())
+        sys.exit(1)  # Python exits with error code 1 on EPIPE
diff --git a/src/sphinxnotes/snippet/ext.py b/src/sphinxnotes/snippet/ext.py
index e37fd23..178c98c 100644
--- a/src/sphinxnotes/snippet/ext.py
+++ b/src/sphinxnotes/snippet/ext.py
@@ -1,15 +1,15 @@
 """
-sphinxnotes.ext.snippet
+sphinxnotes.snippet.ext
 ~~~~~~~~~~~~~~~~~~~~~~~
 
-Sphinx extension for sphinxnotes.snippet.
+Sphinx extension implementation, but the entrypoint is located at __init__.py.
 
-:copyright: Copyright 2021 Shengyu Zhang
+:copyright: Copyright 2024 Shengyu Zhang
 :license: BSD, see LICENSE for details.
 """
 
 from __future__ import annotations
-from typing import List, Set, TYPE_CHECKING, Dict
+from typing import TYPE_CHECKING
 import re
 from os import path
 import time
@@ -26,7 +26,7 @@
     from collections.abc import Iterator
 
 from .config import Config
-from . import Snippet, WithTitle, Document, Section
+from .snippets import Snippet, WithTitle, Document, Section, Code
 from .picker import pick
 from .cache import Cache, Item
 from .keyword import Extractor
@@ -45,53 +45,38 @@ def extract_tags(s: Snippet) -> str:
         tags += 'd'
     elif isinstance(s, Section):
         tags += 's'
+    elif isinstance(s, Code):
+        tags += 'c'
     return tags
 
 
 def extract_excerpt(s: Snippet) -> str:
     if isinstance(s, Document) and s.title is not None:
-        return '<' + s.title.text + '>'
+        return '<' + s.title + '>'
     elif isinstance(s, Section) and s.title is not None:
-        return '[' + s.title.text + ']'
+        return '[' + s.title + ']'
+    elif isinstance(s, Code):
+        return '`' + (s.lang + ':').ljust(8, ' ') + ' ' + s.desc + '`'
     return ''
 
 
-def extract_keywords(s: Snippet) -> List[str]:
-    keywords = []
-    # TODO: Deal with more snippet
+def extract_keywords(s: Snippet) -> list[str]:
+    keywords = [s.docname]
     if isinstance(s, WithTitle) and s.title is not None:
-        keywords.extend(extractor.extract(s.title.text, strip_stopwords=False))
+        keywords.extend(extractor.extract(s.title, strip_stopwords=False))
+    if isinstance(s, Code):
+        keywords.extend(extractor.extract(s.desc, strip_stopwords=False))
     return keywords
 
 
-def is_document_matched(
-    pats: Dict[str, List[str]], docname: str
-) -> Dict[str, List[str]]:
-    """Whether the docname matched by given patterns pats"""
-    new_pats = {}
-    for tag, ps in pats.items():
+def _get_document_allowed_tags(pats: dict[str, list[str]], docname: str) -> str:
+    """Return the tags of snippets that are allowed to be picked from the document."""
+    allowed_tags = ''
+    for tags, ps in pats.items():
         for pat in ps:
             if re.match(pat, docname):
-                new_pats.setdefault(tag, []).append(pat)
-    return new_pats
-
-
-def is_snippet_matched(pats: Dict[str, List[str]], s: [Snippet], docname: str) -> bool:
-    """Whether the snippet's tags and docname matched by given patterns pats"""
-    if '*' in pats:  # Wildcard
-        for pat in pats['*']:
-            if re.match(pat, docname):
-                return True
-
-    not_in_pats = True
-    for k in extract_tags(s):
-        if k not in pats:
-            continue
-        not_in_pats = False
-        for pat in pats[k]:
-            if re.match(pat, docname):
-                return True
-    return not_in_pats
+                allowed_tags += tags
+    return allowed_tags
 
 
 def on_config_inited(app: Sphinx, appcfg: SphinxConfig) -> None:
@@ -108,11 +93,12 @@ def on_config_inited(app: Sphinx, appcfg: SphinxConfig) -> None:
 def on_env_get_outdated(
     app: Sphinx,
     env: BuildEnvironment,
-    added: Set[str],
-    changed: Set[str],
-    removed: Set[str],
-) -> List[str]:
+    added: set[str],
+    changed: set[str],
+    removed: set[str],
+) -> list[str]:
     # Remove purged indexes and snippetes from db
+    assert cache is not None
     for docname in removed:
         del cache[(app.config.project, docname)]
     return []
@@ -126,15 +112,18 @@ def on_doctree_resolved(app: Sphinx, doctree: nodes.document, docname: str) -> N
         )
         return
 
-    pats = is_document_matched(app.config.snippet_patterns, docname)
-    if len(pats) == 0:
-        logger.debug('[snippet] skip picking because %s is not matched', docname)
+    allowed_tags = _get_document_allowed_tags(app.config.snippet_patterns, docname)
+    if not allowed_tags:
+        logger.debug('[snippet] skip picking: no tag allowed for document %s', docname)
         return
 
     doc = []
     snippets = pick(app, doctree, docname)
+    tags = []
     for s, n in snippets:
-        if not is_snippet_matched(pats, s, docname):
+        # FIXME: Better filter logic.
+        tags.append(extract_tags(s))
+        if tags[-1] not in allowed_tags:
             continue
         tpath = [x.astext() for x in titlepath.resolve(app.env, docname, n)]
         if isinstance(s, Section):
@@ -150,17 +139,24 @@ def on_doctree_resolved(app: Sphinx, doctree: nodes.document, docname: str) -> N
         )
 
     cache_key = (app.config.project, docname)
+    assert cache is not None
     if len(doc) != 0:
         cache[cache_key] = doc
     elif cache_key in cache:
         del cache[cache_key]
 
     logger.debug(
-        '[snippet] picked %s/%s snippetes in %s', len(doc), len(snippets), docname
+        '[snippet] picked %s/%s snippets in %s, tags: %s, allowed tags: %s',
+        len(doc),
+        len(snippets),
+        docname,
+        tags,
+        allowed_tags,
     )
 
 
 def on_builder_finished(app: Sphinx, exception) -> None:
+    assert cache is not None
     cache.dump()
 
 
@@ -206,15 +202,3 @@ def _format_modified_time(timestamp: float) -> str:
     """Return an RFC 3339 formatted string representing the given timestamp."""
     seconds, fraction = divmod(timestamp, 1)
     return time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime(seconds)) + f'.{fraction:.3f}'
-
-
-def setup(app: Sphinx):
-    app.add_builder(SnippetBuilder)
-
-    app.add_config_value('snippet_config', {}, '')
-    app.add_config_value('snippet_patterns', {'*': ['.*']}, '')
-
-    app.connect('config-inited', on_config_inited)
-    app.connect('env-get-outdated', on_env_get_outdated)
-    app.connect('doctree-resolved', on_doctree_resolved)
-    app.connect('build-finished', on_builder_finished)
diff --git a/src/sphinxnotes/snippet/integration/binding.nvim b/src/sphinxnotes/snippet/integration/binding.nvim
index 6f05c5f..25f0f34 100644
--- a/src/sphinxnotes/snippet/integration/binding.nvim
+++ b/src/sphinxnotes/snippet/integration/binding.nvim
@@ -8,10 +8,10 @@
 " TODO: Support vim?
 
 function! g:SphinxNotesSnippetListAndView()
-  function! s:CallView(selection)
-    call g:SphinxNotesSnippetView(s:SplitID(a:selection))
+  function! ListAndView_CB(id)
+    call g:SphinxNotesSnippetView(a:id)
   endfunction
-  call g:SphinxNotesSnippetList(function('s:CallView'), 'ds')
+  call g:SphinxNotesSnippetList('"*"', function('ListAndView_CB'))
 endfunction
 
 " https://github.com/anhmv/vim-float-window/blob/master/plugin/float-window.vim
@@ -40,7 +40,7 @@ function! g:SphinxNotesSnippetView(id)
   " Press enter to return
   nmap <buffer> <CR> :call nvim_win_close(g:sphinx_notes_snippet_win, v:true)<CR>
 
-  let cmd = [s:snippet, 'get', '--text', a:id]
+  let cmd = [s:snippet, 'get', '--src', a:id]
   call append(line('$'), ['.. hint:: Press <ENTER> to return'])
   execute '$read !' . '..'
   execute '$read !' . join(cmd, ' ')
diff --git a/src/sphinxnotes/snippet/integration/binding.sh b/src/sphinxnotes/snippet/integration/binding.sh
index a07dd17..f831d58 100644
--- a/src/sphinxnotes/snippet/integration/binding.sh
+++ b/src/sphinxnotes/snippet/integration/binding.sh
@@ -3,10 +3,10 @@
 #
 # :Author: Shengyu Zhang
 # :Date: 2021-08-14
-# :Version: 20211114
+# :Version: 20240828
 
 function snippet_view() {
-  selection=$(snippet_list ds)
+  selection=$(snippet_list)
   [ -z "$selection" ] && return
 
   # Make sure we have $PAGER
@@ -18,18 +18,18 @@ function snippet_view() {
     fi
   fi
 
-  echo "$SNIPPET get --text $selection | $PAGER"
+  echo "$SNIPPET get --src $selection | $PAGER"
 }
 
 function snippet_edit() {
-  selection=$(snippet_list ds)
+  selection=$(snippet_list --tags ds)
   [ -z "$selection" ] && return
 
   echo "vim +\$($SNIPPET get --line-start $selection) \$($SNIPPET get --file $selection)"
 }
 
 function snippet_url() {
-  selection=$(snippet_list ds)
+  selection=$(snippet_list --tags ds)
   [ -z "$selection" ] && return
 
   echo "xdg-open \$($SNIPPET get --url $selection)"
diff --git a/src/sphinxnotes/snippet/integration/binding.vim b/src/sphinxnotes/snippet/integration/binding.vim
index 3b4539d..6225080 100644
--- a/src/sphinxnotes/snippet/integration/binding.vim
+++ b/src/sphinxnotes/snippet/integration/binding.vim
@@ -6,39 +6,40 @@
 " :Version: 20211114
 "
 
-function! g:SphinxNotesSnippetEdit(id)
-  let file = system(join([s:snippet, 'get', '--file', a:id, '2>/dev/null'], ' '))
-  let line = system(join([s:snippet, 'get', '--line-start', a:id, '2>/dev/null'], ' '))
+function g:SphinxNotesSnippetEdit(id)
+  let file = g:SphinxNotesSnippetGet(a:id, 'file')[0]
+  let line = g:SphinxNotesSnippetGet(a:id, 'line-start')[0]
   if &modified
-    execute 'tabedit ' . file
+    execute 'vsplit ' . file
   else
     execute 'edit ' . file
   endif
   execute line
 endfunction
 
-function! g:SphinxNotesSnippetListAndEdit()
-  function! s:CallEdit(selection)
-    call g:SphinxNotesSnippetEdit(s:SplitID(a:selection))
+function g:SphinxNotesSnippetListAndEdit()
+  function! ListAndEdit_CB(id)
+    call g:SphinxNotesSnippetEdit(a:id)
   endfunction
-  call g:SphinxNotesSnippetList(function('s:CallEdit'), 'ds')
+  call g:SphinxNotesSnippetList('ds', function('ListAndEdit_CB'))
 endfunction
 
-function! g:SphinxNotesSnippetUrl(id)
-  let url_list = systemlist(join([s:snippet, 'get', '--url', a:id, '2>/dev/null'], ' '))
+function g:SphinxNotesSnippetUrl(id)
+  let url_list = g:SphinxNotesSnippetGet(a:id, 'url')
   for url in url_list
     echo system('xdg-open ' . shellescape(url))
   endfor
 endfunction
 
-function! g:SphinxNotesSnippetListAndUrl()
-  function! s:CallUrl(selection)
-    call g:SphinxNotesSnippetUrl(s:SplitID(a:selection))
+function g:SphinxNotesSnippetListAndUrl()
+  function! ListAndUrl_CB(id)
+    call g:SphinxNotesSnippetUrl(a:id)
   endfunction
-  call g:SphinxNotesSnippetList(function('s:CallUrl'), 'ds')
+  call g:SphinxNotesSnippetList('ds', function('ListAndUrl_CB'))
 endfunction
 
 nmap <C-k>e :call g:SphinxNotesSnippetListAndEdit()<CR>
 nmap <C-k>u :call g:SphinxNotesSnippetListAndUrl()<CR>
+nmap <C-k>i :call g:SphinxNotesSnippetListAndInput()<CR>
 
 " vim: set shiftwidth=2:
diff --git a/src/sphinxnotes/snippet/integration/plugin.sh b/src/sphinxnotes/snippet/integration/plugin.sh
index 5b75e0a..3d24a91 100644
--- a/src/sphinxnotes/snippet/integration/plugin.sh
+++ b/src/sphinxnotes/snippet/integration/plugin.sh
@@ -3,15 +3,15 @@
 #
 # :Author: Shengyu Zhang
 # :Date: 2021-03-20
-# :Version: 20211114
+# :Version: 20240828
 
 # Make sure we have $SNIPPET
 [ -z "$SNIPPET"] && SNIPPET='snippet'
 
-# Arguments: $1: kinds
+# Arguments: $*: Extra opts of ``snippet list``
 # Returns: snippet_id
 function snippet_list() {
-  $SNIPPET list --tags $1 --width $(($(tput cols) - 2)) | \
+  $SNIPPET list --width $(($(tput cols) - 2)) "$@" | \
     fzf --with-nth 2..      \
         --no-hscroll        \
         --header-lines 1    \
diff --git a/src/sphinxnotes/snippet/integration/plugin.vim b/src/sphinxnotes/snippet/integration/plugin.vim
index cfe77f7..3cf01c5 100644
--- a/src/sphinxnotes/snippet/integration/plugin.vim
+++ b/src/sphinxnotes/snippet/integration/plugin.vim
@@ -8,24 +8,102 @@
 " NOTE: junegunn/fzf.vim is required
 
 let s:snippet = 'snippet'
+let s:width = 0.9
+let s:height = 0.6
 
-function! s:SplitID(row)
-  return split(a:row, ' ')[0]
-endfunction
-
-function! g:SphinxNotesSnippetList(callback, tags)
-  let l:width = 0.9
+" Use fzf to list all snippets, callback with argument id.
+function g:SphinxNotesSnippetList(tags, callback)
   let cmd = [s:snippet, 'list',
         \ '--tags', a:tags,
-        \ '--width', float2nr(&columns * l:width) - 2,
+        \ '--width', float2nr(&columns * s:width) - 2,
         \ ]
+
+  " Use closure keyword so that inner function can access outer one's
+  " localvars (l:) and arguments (a:).
+  " https://vi.stackexchange.com/a/21807
+  function! List_CB(selection) closure
+      let id = split(a:selection, ' ')[0]
+      call a:callback(id)
+  endfunction
+
   " https://github.com/junegunn/fzf/blob/master/README-VIM.md#fzfrun
   call fzf#run({
         \ 'source': join(cmd, ' '),
-        \ 'sink': a:callback,
+        \ 'sink': function('List_CB'),
         \ 'options': ['--with-nth', '2..', '--no-hscroll', '--header-lines', '1'],
-        \ 'window': {'width': l:width, 'height': 0.6},
+        \ 'window': {'width': s:width, 'height': s:height},
         \ })
 endfunction
 
-" vim: set shiftwidth=2:
+" Return the attribute value of specific snippet.
+function g:SphinxNotesSnippetGet(id, attr)
+    let cmd = [s:snippet, 'get', a:id, '--' . a:attr]
+    return systemlist(join(cmd, ' '))
+endfunction
+
+" Use fzf to list all attr of specific snippet,
+" callback with arguments (attr_name, attr_value).
+function g:SphinxNotesSnippetListSnippetAttrs(id, callback)
+    " Display attr -> Identify attr (also used as CLI option)
+    let attrs = {
+                \ 'Source':             'src',
+                \ 'URL':                'url',
+                \ 'Docname':            'docname',
+                \ 'Dependent files':    'deps',
+                \ 'Text':               'text',
+                \ 'Title':              'title',
+                \ }
+    let delim = '  '
+    let table = ['OPTION' . delim . 'ATTRIBUTE']
+    for name in keys(attrs)
+        call add(table, attrs[name] . delim . name)
+    endfor
+
+    function! ListSnippetAttrs_CB(selection) closure
+        let opt = split(a:selection, ' ')[0]
+        let val = g:SphinxNotesSnippetGet(a:id, opt)
+        call a:callback(opt, val) " finally call user's cb
+    endfunction
+
+    let preview_cmd = [s:snippet, 'get', a:id, '--$(echo {} | cut -d " " -f1)']
+    let info_cmd = ['echo', 'Index ID:', a:id]
+    call fzf#run({
+                \ 'source': table,
+                \ 'sink': function('ListSnippetAttrs_CB'),
+                \ 'options': [
+                \               '--header-lines', '1',
+                \               '--with-nth', '2..',
+                \               '--preview', join(preview_cmd, ' '),
+                \               '--preview-window', ',wrap',
+                \               '--info-command', join(info_cmd, ' '),
+                \            ],
+                \ 'window': {'width': s:width, 'height': s:height},
+                \ })
+endfunction
+
+function g:SphinxNotesSnippetInput(id)
+  function! Input_CB(attr, val) " TODO: became g:func.
+    if a:attr == 'docname' 
+      " Create doc reference.
+      let content = ':doc:`/' . a:val[0] . '`'
+    elseif a:attr == 'title'
+      " Create local section reference.
+      let content = '`' . a:val[0] . '`_'
+    else
+      let content = join(a:val, '<CR>')
+    endif
+    execute 'normal! i' . content
+  endfunction
+
+  call g:SphinxNotesSnippetListSnippetAttrs(a:id, function('Input_CB'))
+endfunction
+
+function g:SphinxNotesSnippetListAndInput()
+  function! ListAndInput_CB(id)
+    call g:SphinxNotesSnippetInput(a:id)
+  endfunction
+
+  call g:SphinxNotesSnippetList('"*"', function('ListAndInput_CB'))
+endfunction
+
+  " vim: set shiftwidth=2:
diff --git a/src/sphinxnotes/snippet/keyword.py b/src/sphinxnotes/snippet/keyword.py
index 6ff21d5..80d45f8 100644
--- a/src/sphinxnotes/snippet/keyword.py
+++ b/src/sphinxnotes/snippet/keyword.py
@@ -9,7 +9,6 @@
 """
 
 from __future__ import annotations
-from typing import List, Optional
 import string
 from collections import Counter
 
@@ -47,8 +46,8 @@ def __init__(self):
         )
 
     def extract(
-        self, text: str, top_n: Optional[int] = None, strip_stopwords: bool = True
-    ) -> List[str]:
+        self, text: str, top_n: int | None = None, strip_stopwords: bool = True
+    ) -> list[str]:
         """Return keywords of given text."""
         # TODO: zh -> en
         # Normalize
@@ -87,7 +86,7 @@ def normalize(self, text: str) -> str:
         text = text.replace('\n', ' ')
         return text
 
-    def tokenize(self, text: str) -> List[str]:
+    def tokenize(self, text: str) -> list[str]:
         # Get top most 5 langs
         langs = self._detect_langs(text)[:5]
         tokens = [text]
@@ -104,10 +103,10 @@ def tokenize(self, text: str) -> List[str]:
             new_tokens = []
         return tokens
 
-    def trans_to_pinyin(self, word: str) -> Optional[str]:
+    def trans_to_pinyin(self, word: str) -> str | None:
         return ' '.join(self._pinyin(word, errors='ignore'))
 
-    def strip_stopwords(self, words: List[str]) -> List[str]:
+    def strip_stopwords(self, words: list[str]) -> list[str]:
         stw = self._stopwords(['en', 'zh'])
         new_words = []
         for word in words:
@@ -115,5 +114,5 @@ def strip_stopwords(self, words: List[str]) -> List[str]:
                 new_words.append(word)
         return new_words
 
-    def strip_invalid_token(self, tokens: List[str]) -> List[str]:
+    def strip_invalid_token(self, tokens: list[str]) -> list[str]:
         return [token for token in tokens if token != '']
diff --git a/src/sphinxnotes/snippet/picker.py b/src/sphinxnotes/snippet/picker.py
index 9b2ac2a..ea1b4cf 100644
--- a/src/sphinxnotes/snippet/picker.py
+++ b/src/sphinxnotes/snippet/picker.py
@@ -15,7 +15,7 @@
 
 from sphinx.util import logging
 
-from . import Snippet, Section, Document
+from .snippets import Snippet, Section, Document, Code
 
 if TYPE_CHECKING:
     from sphinx.application import Sphinx
@@ -25,81 +25,73 @@
 
 def pick(
     app: Sphinx, doctree: nodes.document, docname: str
-) -> list[tuple[Snippet, nodes.section]]:
+) -> list[tuple[Snippet, nodes.Element]]:
     """
-    Pick snippets from document, return a list of snippet and the section
-    it belongs to.
+    Pick snippets from document, return a list of snippet and the related node.
+
+    As :class:`Snippet` can not hold any refs to doctree, we additionly returns
+    the related nodes here. To ensure the caller can back reference to original
+    document node and do more things (e.g. generate title path).
     """
     # FIXME: Why doctree.source is always None?
     if not doctree.attributes.get('source'):
-        logger.debug('Skipped document without source')
+        logger.debug('Skip document %s: no source', docname)
         return []
 
     metadata = app.env.metadata.get(docname, {})
     if 'no-search' in metadata or 'nosearch' in metadata:
-        logger.debug('Skipped document with nosearch metadata')
+        logger.debug('Skip document %s: have :no[-]search: metadata', docname)
         return []
 
-    snippets = []
-
-    # Pick document
-    toplevel_section = doctree.next_node(nodes.section)
-    if toplevel_section:
-        snippets.append((Document(doctree), toplevel_section))
-    else:
-        logger.warning('can not pick document without child section: %s', doctree)
-
-    # Pick sections
-    section_picker = SectionPicker(doctree)
-    doctree.walkabout(section_picker)
-    snippets.extend(section_picker.sections)
+    # Walk doctree and pick snippets.
 
-    return snippets
+    picker = SnippetPicker(doctree)
+    doctree.walkabout(picker)
 
+    return picker.snippets
 
-class SectionPicker(nodes.SparseNodeVisitor):
-    """Node visitor for picking code snippet from document."""
 
-    #: Constant list of unsupported languages (:class:`pygments.lexers.Lexer`)
-    UNSUPPORTED_LANGUAGES: list[str] = ['default']
+class SnippetPicker(nodes.SparseNodeVisitor):
+    """Node visitor for picking snippets from document."""
 
-    #: List of picked section snippets and the section it belongs to
-    sections: list[tuple[Section, nodes.section]]
+    #: List of picked snippets and the section it belongs to
+    snippets: list[tuple[Snippet, nodes.Element]]
 
-    _section_has_code_block: bool
-    _section_level: int
+    #: Stack of nested sections.
+    _sections: list[nodes.section]
 
-    def __init__(self, document: nodes.document) -> None:
-        super().__init__(document)
-        self.sections = []
-        self._section_has_code_block = False
-        self._section_level = 0
+    def __init__(self, doctree: nodes.document) -> None:
+        super().__init__(doctree)
+        self.snippets = []
+        self._sections = []
 
     ###################
     # Visitor methods #
     ###################
 
     def visit_literal_block(self, node: nodes.literal_block) -> None:
-        if node['language'] in self.UNSUPPORTED_LANGUAGES:
+        try:
+            code = Code(node)
+        except ValueError as e:
+            logger.debug(f'skip {node}: {e}')
             raise nodes.SkipNode
-        self._has_code_block = True
+        self.snippets.append((code, node))
 
     def visit_section(self, node: nodes.section) -> None:
-        self._section_level += 1
+        self._sections.append(node)
 
     def depart_section(self, node: nodes.section) -> None:
-        self._section_level -= 1
-        self._has_code_block = False
+        section = self._sections.pop()
+        assert section == node
 
+        # Always pick document.
+        if len(self._sections) == 0:
+            self.snippets.append((Document(self.document), node))
+            return
         # Skip non-leaf section without content
         if self._is_empty_non_leaf_section(node):
             return
-        # Skip toplevel section, we generate :class:`Document` for it
-        if self._section_level == 0:
-            return
-
-        # TODO: code block
-        self.sections.append((Section(node), node))
+        self.snippets.append((Section(node), node))
 
     def unknown_visit(self, node: nodes.Node) -> None:
         pass  # Ignore any unknown node
diff --git a/src/sphinxnotes/snippet/snippets.py b/src/sphinxnotes/snippet/snippets.py
new file mode 100644
index 0000000..f14661a
--- /dev/null
+++ b/src/sphinxnotes/snippet/snippets.py
@@ -0,0 +1,240 @@
+"""
+sphinxnotes.snippet.snippets
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Definitions of various snippets.
+
+:copyright: Copyright 2024 Shengyu Zhang
+:license: BSD, see LICENSE for details.
+"""
+
+from __future__ import annotations
+from typing import TYPE_CHECKING
+import itertools
+from os import path
+import sys
+from pygments.lexers.shell import BashSessionLexer
+
+from docutils import nodes
+
+if TYPE_CHECKING:
+    from sphinx.environment import BuildEnvironment
+
+
+class Snippet(object):
+    """
+    Snippet is structured fragments extracted from a single Sphinx document
+    (usually, also a single reStructuredText file).
+
+    :param nodes: nodes of doctree that make up this snippet.
+
+    .. warning::
+
+       Snippet will be persisted to disk via pickle, to keep it simple,
+       it CAN NOT holds reference to any doctree ``nodes``
+       (or even any non-std module).
+    """
+
+    #: docname where the snippet is located, can be referenced by
+    # :rst:role:`doc`.
+    docname: str
+
+    #: Absolute path to the source file.
+    file: str
+
+    #: Line number range of source file (:attr:`Snippet.file`),
+    #: left closed and right opened.
+    lineno: tuple[int, int]
+
+    #: The source text read from source file (:attr:`Snippet.file`),
+    # in Markdown or reStructuredText.
+    source: list[str]
+
+    #: Text representation of the snippet, usually generated form
+    # :meth:`nodes.Element.astext`.
+    text: list[str]
+
+    #: The possible identifier key of snippet, which is picked from nodes'
+    #: (or nodes' parent's) `ids attr`_.
+    #:
+    #: .. _ids attr: https://docutils.sourceforge.io/docs/ref/doctree.html#ids
+    refid: str | None
+
+    def __init__(self, *nodes: nodes.Element) -> None:
+        assert len(nodes) != 0
+
+        env: BuildEnvironment = nodes[0].document.settings.env  # type: ignore
+
+        file, docname = None, None
+        for node in nodes:
+            if (src := nodes[0].source) and path.exists(src):
+                file = src
+                docname = env.path2doc(file)
+                break
+        if not file or not docname:
+            raise ValueError(f'Nodes {nodes} lacks source file or docname')
+        self.file = file
+        self.docname = docname
+
+        lineno = [sys.maxsize, -sys.maxsize]
+        for node in nodes:
+            if not node.line:
+                continue  # Skip node that have None line, I dont know why
+            lineno[0] = min(lineno[0], _line_of_start(node))
+            lineno[1] = max(lineno[1], _line_of_end(node))
+        self.lineno = (lineno[0], lineno[1])
+
+        source = []
+        with open(self.file, 'r') as f:
+            start = self.lineno[0] - 1
+            stop = self.lineno[1] - 1
+            for line in itertools.islice(f, start, stop):
+                source.append(line.strip('\n'))
+        self.source = source
+
+        text = []
+        for node in nodes:
+            text.extend(node.astext().split('\n'))
+        self.text = text
+
+        # Find exactly one ID attr in nodes
+        self.refid = None
+        for node in nodes:
+            if node['ids']:
+                self.refid = node['ids'][0]
+                break
+
+        # If no ID found, try parent
+        if not self.refid:
+            for node in nodes:
+                if node.parent['ids']:
+                    self.refid = node.parent['ids'][0]
+                    break
+
+
+class Code(Snippet):
+    #: Language of code block
+    lang: str
+    #: Description of code block, usually the text of preceding paragraph
+    desc: str
+
+    def __init__(self, node: nodes.literal_block) -> None:
+        assert isinstance(node, nodes.literal_block)
+
+        self.lang = node['language']
+        if self.lang not in BashSessionLexer.aliases:  # TODO: support more language
+            raise ValueError(
+                f'Language {self.lang} is not supported',
+            )
+
+        self.desc = ''
+        # Use the preceding paragraph as descritpion. We usually write some
+        # descritpions before a code block. For example, The ``::`` syntax is
+        # a common way to create code block::
+        #
+        #   | Foo::       | <paragraph>
+        #   |             |     Foo:
+        #   |     Bar     | <literal_block xml:space="preserve">
+        #   |             |     Bar
+        #
+        # In this case, the paragraph "Foo:" is the descritpion of the code block.
+        # This convention also applies to the code, code-block, sourcecode directive.
+        if isinstance(para := node.previous_sibling(), nodes.paragraph):
+            # For better display, the trailing colon is removed.
+            # TODO: https://en.wikipedia.org/wiki/Colon_(punctuation)#Computing
+            self.desc += para.astext().replace('\n', ' ').rstrip(':：：︁︓﹕')
+        if caption := node.get('caption'):
+            # Use caption as descritpion.
+            # All of code-block, sourcecode and code directives have caption option.
+            # https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-code-block
+            self.desc += caption
+        if not self.desc:
+            raise ValueError(
+                f'Node f{node} lacks description: a preceding paragraph or a caption'
+            )
+
+        if isinstance(para, nodes.paragraph):
+            # If we have a paragraph preceding code block, include it.
+            super().__init__(para, node)
+            # Fixup text field, it should be pure code.
+            self.text = node.astext().split('\n')
+        else:
+            super().__init__(node)
+
+
+class WithTitle(object):
+    title: str
+
+    def __init__(self, node: nodes.Element) -> None:
+        if not (title := node.next_node(nodes.title)):
+            raise ValueError(f'Node f{node} lacks title')
+        self.title = title.astext()
+
+
+class Section(Snippet, WithTitle):
+    def __init__(self, node: nodes.section) -> None:
+        assert isinstance(node, nodes.section)
+        Snippet.__init__(self, node)
+        WithTitle.__init__(self, node)
+
+
+class Document(Section):
+    #: A set of absolute paths of dependent files for document.
+    #: Obtained from :attr:`BuildEnvironment.dependencies`.
+    deps: set[str]
+
+    def __init__(self, node: nodes.document) -> None:
+        assert isinstance(node, nodes.document)
+        super().__init__(node.next_node(nodes.section))
+
+        # Record document's dependent files
+        self.deps = set()
+        env: BuildEnvironment = node.settings.env
+        for dep in env.dependencies[self.docname]:
+            # Relative to documentation root -> Absolute path of file system.
+            self.deps.add(path.join(env.srcdir, dep))
+
+
+################
+# Nodes helper #
+################
+
+
+def _line_of_start(node: nodes.Node) -> int:
+    assert node.line
+    if isinstance(node, nodes.title):
+        if isinstance(node.parent.parent, nodes.document):
+            # Spceial case for Document Title / Subtitle
+            return 1
+        else:
+            # Spceial case for section title
+            return node.line - 1
+    elif isinstance(node, nodes.section):
+        if isinstance(node.parent, nodes.document):
+            # Spceial case for top level section
+            return 1
+        else:
+            # Spceial case for section
+            return node.line - 1
+    return node.line
+
+
+def _line_of_end(node: nodes.Node) -> int:
+    next_node = node.next_node(descend=False, siblings=True, ascend=True)
+    while next_node:
+        if next_node.line:
+            return _line_of_start(next_node)
+        next_node = next_node.next_node(
+            # Some nodes' line attr is always None, but their children has
+            # valid line attr
+            descend=True,
+            # If node and its children have not valid line attr, try use line
+            # of next node
+            ascend=True,
+            siblings=True,
+        )
+    # No line found, return the max line of source file
+    if node.source and path.exists(node.source):
+        with open(node.source) as f:
+            return sum(1 for _ in f)
+    raise AttributeError('None source attr of node %s' % node)
diff --git a/src/sphinxnotes/snippet/table.py b/src/sphinxnotes/snippet/table.py
index 26a8a70..8138573 100644
--- a/src/sphinxnotes/snippet/table.py
+++ b/src/sphinxnotes/snippet/table.py
@@ -7,7 +7,7 @@
 """
 
 from __future__ import annotations
-from typing import Iterator, Dict
+from typing import Iterable
 
 from .cache import Index, IndexID
 from .utils import ellipsis
@@ -17,8 +17,8 @@
 COLUMN_DELIMITER = '  '
 
 
-def tablify(indexes: Dict[IndexID, Index], tags: str, width: int) -> Iterator[str]:
-    """Create a table from sequence of cache.Index."""
+def tablify(indexes: Iterable[tuple[IndexID, Index]], width: int) -> Iterable[str]:
+    """Create a table from sequence of indices"""
 
     # Calcuate width
     width = width
@@ -41,10 +41,8 @@ def tablify(indexes: Dict[IndexID, Index], tags: str, width: int) -> Iterator[st
     yield header
 
     # Write rows
-    for index_id, index in indexes.items():
+    for index_id, index in indexes:
         # TODO: assert index?
-        if index[0] not in tags and '*' not in tags:
-            continue
         row = COLUMN_DELIMITER.join(
             [
                 index_id,  # ID
diff --git a/src/sphinxnotes/snippet/utils/ellipsis.py b/src/sphinxnotes/snippet/utils/ellipsis.py
index 11bfcc5..d46bda8 100644
--- a/src/sphinxnotes/snippet/utils/ellipsis.py
+++ b/src/sphinxnotes/snippet/utils/ellipsis.py
@@ -9,12 +9,11 @@
 """
 
 from __future__ import annotations
-from typing import List
 from wcwidth import wcswidth
 
 
 def ellipsis(
-    text: str, width: int, ellipsis_sym: str = '..', blank_sym: str = None
+    text: str, width: int, ellipsis_sym: str = '..', blank_sym: str | None = None
 ) -> str:
     text_width = wcswidth(text)
     if text_width <= width:
@@ -34,7 +33,7 @@ def ellipsis(
 
 
 def join(
-    lst: List[str],
+    lst: list[str],
     total_width: int,
     title_width: int,
     separate_sym: str = '/',
diff --git a/src/sphinxnotes/snippet/utils/pdict.py b/src/sphinxnotes/snippet/utils/pdict.py
index 59d293f..ef93a38 100644
--- a/src/sphinxnotes/snippet/utils/pdict.py
+++ b/src/sphinxnotes/snippet/utils/pdict.py
@@ -11,7 +11,7 @@
 from __future__ import annotations
 import os
 from os import path
-from typing import Dict, Optional, Iterable, TypeVar
+from typing import Iterator, TypeVar
 import pickle
 from collections.abc import MutableMapping
 from hashlib import sha1
@@ -21,16 +21,16 @@
 
 
 # FIXME: PDict is buggy
-class PDict(MutableMapping):
+class PDict(MutableMapping[K, V]):
     """A persistent dict with event handlers."""
 
     dirname: str
     # The real in memory store of values
-    _store: Dict[K, V]
+    _store: dict[K, V | None]
     # Items that need write back to store
-    _dirty_items: Dict[K, V]
+    _dirty_items: dict[K, V]
     # Items that need purge from store
-    _orphan_items: Dict[K, V]
+    _orphan_items: dict[K, V]
 
     def __init__(self, dirname: str) -> None:
         self.dirname = dirname
@@ -38,7 +38,7 @@ def __init__(self, dirname: str) -> None:
         self._dirty_items = {}
         self._orphan_items = {}
 
-    def __getitem__(self, key: K) -> Optional[V]:
+    def __getitem__(self, key: K) -> V:
         if key not in self._store:
             raise KeyError
         value = self._store[key]
@@ -65,7 +65,7 @@ def __delitem__(self, key: K) -> None:
         else:
             self._orphan_items[key] = value
 
-    def __iter__(self) -> Iterable:
+    def __iter__(self) -> Iterator:
         return iter(self._store)
 
     def __len__(self) -> int:
@@ -142,4 +142,4 @@ def post_purge(self, key: K, value: V) -> None:
         pass
 
     def stringify(self, key: K, value: V) -> str:
-        return key
+        return str(key)
diff --git a/src/sphinxnotes/snippet/utils/titlepath.py b/src/sphinxnotes/snippet/utils/titlepath.py
index 9231537..eaa6bc3 100644
--- a/src/sphinxnotes/snippet/utils/titlepath.py
+++ b/src/sphinxnotes/snippet/utils/titlepath.py
@@ -9,22 +9,21 @@
 """
 
 from __future__ import annotations
-from typing import List, TYPE_CHECKING
+from typing import TYPE_CHECKING
 
 from docutils import nodes
 
 if TYPE_CHECKING:
-    from sphinx.enviornment import BuilderEnviornment
+    from sphinx.environment import BuildEnvironment
 
 
 def resolve(
-    env: BuilderEnviornment, docname: str, node: nodes.Node
-) -> List[nodes.title]:
+    env: BuildEnvironment, docname: str, node: nodes.Element
+) -> list[nodes.title]:
     return resolve_section(node) + resolve_document(env, docname)
 
 
-def resolve_section(node: nodes.section) -> List[nodes.title]:
-    # FIXME: doc is None
+def resolve_section(node: nodes.Element) -> list[nodes.title]:
     titlenodes = []
     while node:
         if len(node) > 0 and isinstance(node[0], nodes.title):
@@ -33,10 +32,8 @@ def resolve_section(node: nodes.section) -> List[nodes.title]:
     return titlenodes
 
 
-def resolve_document(env: BuilderEnviornment, docname: str) -> List[nodes.title]:
-    """
-    .. note:: Title of document itself does not included in the returned list
-    """
+def resolve_document(env: BuildEnvironment, docname: str) -> list[nodes.title]:
+    """NOTE: Title of document itself does not included in the returned list"""
     titles = []
     master_doc = env.config.master_doc
     v = docname.split('/')