1 files changed, 262 insertions, 0 deletions
diff --git a/internal/github/github.go b/internal/github/github.go
new file mode 100644
index 0000000..bf35a6a
--- /dev/null
+++ b/internal/github/github.go
@@ -0,0 +1,262 @@
+package github
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"time"
+)
+
+type Client struct {
+	*jsonClient
+}
+
+func NewClient() *Client {
+	jsonClient := newJSONClient(http.DefaultClient, "https://api.github.com")
+	return &Client{
+		jsonClient: jsonClient,
+	}
+}
+
+type Asset struct {
+	Name               string `json:"name"`
+	BrowserDownloadURL string `json:"browser_download_url"`
+}
+
+type Release struct {
+	ID          int       `json:"id"`
+	TagName     string    `json:"tag_name"`
+	PublishedAt time.Time `json:"published_at"`
+	TarballURL  string    `json:"tarball_url"`
+	ZipballURL  string    `json:"zipball_url"`
+	Assets      []Asset   `json:"assets"`
+}
+
+func intRef(v int) *int {
+	return &v
+}
+
+func (c *Client) ListReleases(owner string, project string) ([]Release, error) {
+	var resp []Release
+
+	_, err := c.jsonClient.Request(http.MethodGet, intRef(http.StatusOK), path.Join("repos", owner, project, "releases"), nil, &resp)
+	if err != nil {
+		return nil, err
+	}
+
+	return resp, nil
+}
+
+func (c *Client) DownloadAsset(w io.Writer, owner string, project string, asset *Asset) error {
+	resp, err := http.Get(asset.BrowserDownloadURL)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(w, resp.Body)
+	if err != nil {
+		return err
+	}
+	return nil
+
+}
+
+func (c *Client) DownloadRelease(
+	dirPath string,
+	org string,
+	project string,
+	release *Release,
+) error {
+	for _, asset := range release.Assets {
+		fp := path.Join(dirPath, path.Base(asset.Name))
+		f, err := os.Create(fp)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		resp, err := http.Get(asset.BrowserDownloadURL)
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(f, resp.Body)
+		if err != nil {
+			return err
+		}
+	}
+
+	fp := path.Join(dirPath, releaseSourceFileName(project, release.TagName, "tar.gz"))
+	if exist, err := isFileExist(fp); err != nil {
+		return fmt.Errorf("downloading tarball: %w", err)
+	} else if !exist {
+		f, err := os.Create(fp)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		resp, err := http.Get(release.TarballURL)
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(f, resp.Body)
+		if err != nil {
+			return err
+		}
+	}
+
+	fp = path.Join(dirPath, releaseSourceFileName(project, release.TagName, "zip"))
+	if exist, err := isFileExist(fp); err != nil {
+		return err
+	} else if !exist {
+		f, err := os.Create(fp)
+		if err != nil {
+			return fmt.Errorf("downloading zipball: %w", err)
+		}
+		defer f.Close()
+
+		resp, err := http.Get(release.ZipballURL)
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(f, resp.Body)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func releaseDownloads(
+	project string,
+	release *Release,
+) map[string]string {
+	files := make(map[string]string)
+
+	for _, asset := range release.Assets {
+		files[path.Base(asset.Name)] = asset.BrowserDownloadURL
+	}
+
+	fileName := releaseSourceFileName(project, release.TagName, "tar.gz")
+	files[fileName] = release.TarballURL
+
+	fileName = releaseSourceFileName(project, release.TagName, "zip")
+	files[fileName] = release.ZipballURL
+
+	return files
+}
+
+func (c *Client) download(dst string, src string) error {
+	resp, err := http.Head(src)
+	if err != nil {
+		return err
+	}
+
+	info, err := os.Stat(dst)
+	if !os.IsNotExist(err) && err != nil {
+		return err
+	}
+	if info != nil {
+		if info.Size() == resp.ContentLength {
+			return nil
+		}
+
+		err := os.Remove(dst)
+		if !os.IsNotExist(err) && err != nil {
+			return fmt.Errorf("could not remove '%s': %w", dst, err)
+		}
+	}
+
+	resp, err = http.Get(src)
+	if err != nil {
+		return err
+	}
+
+	f, err := os.Create(dst)
+	if err != nil {
+		return fmt.Errorf("creating '%s': %w", dst, err)
+	}
+	defer f.Close()
+
+	_, err = io.Copy(f, resp.Body)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Client) MirrorAssets(dst *url.URL, src *url.URL) error {
+	if src.Hostname() != "github.com" {
+		return fmt.Errorf("host must be github.com")
+	}
+	if dst.Scheme != "file:///" && dst.Scheme != "" {
+		return fmt.Errorf("unsupported destination scheme '%s'", dst.Scheme)
+	}
+
+	matches := regexp.MustCompilePOSIX("/(.*?)/(.*?)").FindAllStringSubmatch(src.Path, 1)
+	if len(matches) != 1 && len(matches[0]) != 2 {
+		return fmt.Errorf("must be a full path to the project")
+	}
+
+	owner := matches[0][1]
+	project := matches[0][2]
+
+	releases, err := c.ListReleases(owner, project)
+	if err != nil {
+		return fmt.Errorf("fetching list of releases: %w", err)
+	}
+
+	existingFiles := make(map[string]bool)
+
+	filepath.WalkDir(dst.Path, func(path string, _ os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		path, err = filepath.Abs(path)
+		if err != nil {
+			return err
+		}
+		existingFiles[path] = true
+
+		return nil
+	})
+	delete(existingFiles, dst.Path)
+
+	for _, release := range releases {
+		localDir := localReleaseFilePath(dst, release.TagName)
+		localDir, err = filepath.Abs(localDir)
+		if err != nil {
+			return err
+		}
+
+		err := os.MkdirAll(localDir, 0777)
+		if err != nil {
+			return fmt.Errorf("creating '%s': %w", localDir, err)
+		}
+		delete(existingFiles, localDir)
+
+		for fileName, srcURL := range releaseDownloads(project, &release) {
+			localFile := path.Join(localDir, fileName)
+			delete(existingFiles, localFile)
+
+			err := c.download(localFile, srcURL)
+			if err != nil {
+				return fmt.Errorf("downloading '%s': %w", srcURL, err)
+			}
+		}
+	}
+
+	for fp := range existingFiles {
+		_ = os.RemoveAll(fp)
+	}
+
+	return nil
+}