package gitrepo

import (
	"errors"
	"strings"

	"gitweb/internal/store"
)

// Locate finds whether the upspin path "<user><clean>" points into a bare git
// repository. It scans path prefixes from the user root downward and returns
// the shallowest prefix that is a bare repo (repos do not nest), along with the
// remaining path after it.
//
//   - user:  validated upspin user, e.g. "u@d.com"
//   - clean:  the cleaned remainder, always beginning with "/", e.g. "/proj.git/log/main"
//
// On a match it returns repoPath="u@d.com/proj.git", rest="log/main", found=true.
// found=false means no repo lies on this path and the caller should fall back to
// plain namespace browsing. A store error other than not-found is returned.
func Locate(st store.Store, user, clean string) (repoPath, rest string, found bool, err error) {
	trimmed := strings.Trim(clean, "/")
	var segs []string
	if trimmed != "" {
		segs = strings.Split(trimmed, "/")
	}

	// Candidates shallow -> deep: user, user/seg1, user/seg1/seg2, ...
	prefix := user
	for i := 0; ; i++ {
		ok, err := isRepo(st, prefix)
		if err != nil {
			return "", "", false, err
		}
		if ok {
			return prefix, strings.Join(segs[i:], "/"), true, nil
		}
		if i >= len(segs) {
			break
		}
		prefix = prefix + "/" + segs[i]
	}
	return "", "", false, nil
}

// isRepo reports whether prefix is a bare git repository: it must contain a
// HEAD file and an objects directory. Not-found on either means "not a repo".
func isRepo(st store.Store, prefix string) (bool, error) {
	headIsDir, err := st.Stat(prefix + "/HEAD")
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			return false, nil
		}
		return false, err
	}
	if headIsDir {
		return false, nil
	}
	objIsDir, err := st.Stat(prefix + "/objects")
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			return false, nil
		}
		return false, err
	}
	return objIsDir, nil
}