Initial Twitter client implementation to fetch user metadata (#86)

* Initial Twitter client implementation to fetch user metadata

* Use context in Twitter HTTP calls

Author: jeffyanta

pkg/twitter/client.go

@@ -0,0 +1,126 @@
+package twitter
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/pkg/errors"
+
+	"github.com/code-payments/code-server/pkg/metrics"
+)
+
+const (
+	baseUrl              = "https://api.twitter.com/2/"
+	getUserByIdUrl       = baseUrl + "users/"
+	getUserByUsernameUrl = baseUrl + "users/by/username/"
+
+	metricsStructName = "twitter.client"
+)
+
+type Client struct {
+	client   *http.Client
+	apiToken string
+}
+
+// NewClient returns a new Twitter client
+func NewClient(apiToken string) *Client {
+	return &Client{
+		client:   http.DefaultClient,
+		apiToken: apiToken,
+	}
+}
+
+// User represents the structure for a user in the Twitter API response
+type User struct {
+	ID              string        `json:"id"`
+	Username        string        `json:"username"`
+	Name            string        `json:"name"`
+	ProfileImageUrl string        `json:"profile_image_url"`
+	PublicMetrics   PublicMetrics `json:"public_metrics"`
+}
+
+// PublicMetrics are public metrics for a Twitter user
+type PublicMetrics struct {
+	FollowersCount int `json:"followers_count"`
+	FollowingCount int `json:"following_count"`
+	TweetCount     int `json:"tweet_count"`
+	LikeCount      int `json:"like_count"`
+}
+
+// GetUserById makes a request to the Twitter API and returns the user's information
+// by ID
+func (c *Client) GetUserById(ctx context.Context, id string) (*User, error) {
+	tracer := metrics.TraceMethodCall(ctx, metricsStructName, "GetUserById")
+	defer tracer.End()
+
+	user, err := c.getUser(ctx, getUserByIdUrl+id)
+	if err != nil {
+		tracer.OnError(err)
+	}
+	return user, err
+}
+
+// GetUserByUsername makes a request to the Twitter API and returns the user's information
+// by username
+func (c *Client) GetUserByUsername(ctx context.Context, username string) (*User, error) {
+	tracer := metrics.TraceMethodCall(ctx, metricsStructName, "GetUserByUsername")
+	defer tracer.End()
+
+	user, err := c.getUser(ctx, getUserByUsernameUrl+username)
+	if err != nil {
+		tracer.OnError(err)
+	}
+	return user, err
+}
+
+func (c *Client) getUser(ctx context.Context, fromUrl string) (*User, error) {
+	req, err := http.NewRequest("GET", fromUrl+"?user.fields=profile_image_url,public_metrics", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req = req.WithContext(ctx)
+
+	req.Header.Add("Authorization", "Bearer "+c.apiToken)
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected http status code: %d", resp.StatusCode)
+	}
+
+	var result struct {
+		Data   User           `json:"data"`
+		Errors []twitterError `json:"errors"`
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, err
+	}
+
+	if len(result.Errors) > 0 {
+		return nil, result.Errors[0].toError()
+	}
+	return &result.Data, nil
+}
+
+type twitterError struct {
+	Title  string `json:"title"`
+	Detail string `json:"detail"`
+}
+
+func (e *twitterError) toError() error {
+	return errors.Errorf("%s: %s", e.Title, e.Detail)
+}