package git

import (
	"context"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"go.skia.org/infra/go/exec"
	"go.skia.org/infra/go/skerr"
	"go.skia.org/infra/go/sklog"
)

// Clone runs "git clone" into the given destination directory. Most callers
// should use NewRepo or NewCheckout instead.
func Clone(ctx context.Context, repoUrl, dest string, mirror bool) error {
	git, err := Executable(ctx)
	if err != nil {
		return skerr.Wrap(err)
	}
	if mirror {
		// We don't use a "real" mirror, since that syncs ALL refs,
		// including every patchset of every CL that gets uploaded. Instead,
		// we use a bare clone and then add the "mirror" config after
		// cloning. It would be equivalent to use --mirror and then update
		// the refspec to only sync the branches, but that would force the
		// initial clone step to sync every ref.
		if _, err := exec.RunCwd(ctx, ".", git, "clone", "--bare", repoUrl, dest); err != nil {
			return fmt.Errorf("Failed to clone repo: %s", err)
		}
		if _, err := exec.RunCwd(ctx, dest, git, "config", "remote.origin.mirror", "true"); err != nil {
			return fmt.Errorf("Failed to set git mirror config: %s", err)
		}
		if _, err := exec.RunCwd(ctx, dest, git, "config", "remote.origin.fetch", "refs/heads/*:refs/heads/*"); err != nil {
			return fmt.Errorf("Failed to set git mirror config: %s", err)
		}
		if _, err := exec.RunCwd(ctx, dest, git, "fetch", "--force", "--all"); err != nil {
			return fmt.Errorf("Failed to set git mirror config: %s", err)
		}
	} else {
		if _, err := exec.RunCwd(ctx, ".", git, "clone", repoUrl, dest); err != nil {
			return fmt.Errorf("Failed to clone repo: %s", err)
		}
	}
	return nil
}

// LogFromTo returns a string which is used to log from one commit to another.
// It is important to note that:
// - The results may include the second commit but will not include the first.
// - The results include all commits reachable from the first commit which are
//   not reachable from the second, ie. if there is a merge in the given
//   range, the results will include that line of history and not just the
//   commits which are descendants of the first commit. If you want only commits
//   which are ancestors of the second commit AND descendants of the first, you
//   should use LogLinear, but note that the results will be empty if the first
//   commit is not an ancestor of the second, ie. they're on different branches.
func LogFromTo(from, to string) string {
	return fmt.Sprintf("%s..%s", from, to)
}

// NormalizeURL strips everything from the URL except for the host and the path.
// A trailing ".git" is also stripped. The purpose is to allow for small
// variations in repo URL to be recognized as the same repo. The URL needs to
// contain a valid transport protocol, e.g. https, ssh.
// These URLs will all return 'github.com/skia-dev/textfiles':
//
//    "https://github.com/skia-dev/textfiles.git"
//    "ssh://git@github.com/skia-dev/textfiles"
//    "ssh://git@github.com:skia-dev/textfiles.git"
//
func NormalizeURL(inputURL string) (string, error) {
	// If the scheme is ssh we have to account for the scp-like syntax with a ':'
	const ssh = "ssh://"
	if strings.HasPrefix(inputURL, ssh) {
		inputURL = ssh + strings.Replace(inputURL[len(ssh):], ":", "/", 1)
	}

	parsedURL, err := url.Parse(inputURL)
	if err != nil {
		return "", skerr.Wrapf(err, "parsing inputURL")
	}

	host := parsedURL.Host
	// Trim trailing slashes and the ".git" extension.
	path := strings.TrimRight(strings.TrimSuffix(parsedURL.Path, ".git"), "/")
	path = "/" + strings.TrimLeft(path, "/:")
	return host + path, nil
}

// DeleteLockFiles finds and deletes Git lock files within the given workdir.
func DeleteLockFiles(ctx context.Context, workdir string) error {
	sklog.Infof("Looking for git lockfiles in %s", workdir)
	output, err := exec.RunCwd(ctx, workdir, "find", ".", "-name", "index.lock")
	if err != nil {
		return err
	}
	output = strings.TrimSpace(output)
	if output == "" {
		sklog.Info("No lockfiles found.")
		return nil
	}
	lockfiles := strings.Split(output, "\n")
	for _, f := range lockfiles {
		fp := filepath.Join(workdir, f)
		sklog.Warningf("Removing git lockfile: %s", fp)
		if err := os.Remove(fp); err != nil {
			return err
		}
	}
	return nil
}