tests/thirdparty: package metadata (#223)

Fetches third-party package metadata from Github.

internal/github/client.go

@@ -0,0 +1,107 @@
+// Package github provides a client for the Github REST API.
+package github
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"os"
+)
+
+// Client for the Github REST API.
+type Client struct {
+	client *http.Client
+	base   string
+	token  string
+}
+
+// Option configures a Github client.
+type Option func(*Client)
+
+// WithHTTPClient configures the HTTP client that should be used for Github API
+// requests.
+func WithHTTPClient(h *http.Client) Option {
+	return func(c *Client) { c.client = h }
+}
+
+// WithToken configures a Client with an authentication token for Github API
+// requests.
+func WithToken(token string) Option {
+	return func(c *Client) { c.token = token }
+}
+
+// WithTokenFromEnvironment configures a Client using the GITHUB_TOKEN
+// environment variable.
+func WithTokenFromEnvironment() Option {
+	return WithToken(os.Getenv("GITHUB_TOKEN"))
+}
+
+// NewClient initializes a client using the given HTTP client.
+func NewClient(opts ...Option) *Client {
+	c := &Client{
+		client: http.DefaultClient,
+		base:   "https://api.github.com",
+	}
+	for _, opt := range opts {
+		opt(c)
+	}
+	return c
+}
+
+// Repository gets information about the given Github repository.
+func (c *Client) Repository(ctx context.Context, owner, name string) (*Repository, error) {
+	// Build request.
+	u := c.base + "/repos/" + owner + "/" + name
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// Execute.
+	repo := &Repository{}
+	if err := c.request(req, repo); err != nil {
+		return nil, err
+	}
+
+	return repo, nil
+}
+
+func (c *Client) request(req *http.Request, payload interface{}) (err error) {
+	// Add common headers.
+	if c.token != "" {
+		req.Header.Set("Authorization", "Bearer "+c.token)
+	}
+	req.Header.Set("Accept", "application/vnd.github.v3+json")
+
+	// Execute the request.
+	res, err := c.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if errc := res.Body.Close(); errc != nil && err == nil {
+			err = errc
+		}
+	}()
+
+	// Check status.
+	if res.StatusCode != http.StatusOK {
+		return fmt.Errorf("http status %d: %s", res.StatusCode, http.StatusText(res.StatusCode))
+	}
+
+	// Parse response body.
+	d := json.NewDecoder(res.Body)
+
+	if err := d.Decode(payload); err != nil {
+		return err
+	}
+
+	// Should not have trailing data.
+	if d.More() {
+		return errors.New("unexpected extra data after JSON")
+	}
+
+	return nil
+}