package main

import (
	"context"
	"encoding/base64"
	"fmt"
	"io"
	"net/url"
	"os"
	"os/exec"
	"os/signal"
	"strings"

	"git.geekeey.de/actions/sdk"
)

func main() {
	action := &CheckoutAction{Action: sdk.New()}
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
	defer cancel()
	if err := action.Run(ctx); err != nil {
		action.Errorf("%s", err)
		os.Exit(1)
	}
}

type CheckoutAction struct {
	*sdk.Action
	repository string
	path       string
	reference  string
}

func (action *CheckoutAction) setup() error {
	var err error

	action.repository = action.GetInput("repository")
	if len(action.repository) == 0 {
		return fmt.Errorf("input 'repository': is empty") // something like '<server>/<owner>/<repo>.git'
	}

	action.path = action.GetInput("path")
	if len(action.path) == 0 {
		return fmt.Errorf("input 'path': is empty") // something like '.'
	}

	action.reference = action.GetInput("ref")
	if len(action.reference) == 0 {
		return fmt.Errorf("input 'ref': is empty") // something like 'HEAD'
	}
	return err
}

func (action *CheckoutAction) Run(ctx context.Context) error {
	if err := action.setup(); err != nil {
		return err
	}

	env := action.Context()
	server, err := url.Parse(env.ServerURL)
	if err != nil {
		return fmt.Errorf("invalid serevr url: %s", err)
	}

	shell := Shell{action: action.Action, args: [][]string{}}

	shell.Add("git", "config", "--global", "--add", "protocol.version", "2")
	shell.Add("git", "init", "-q", action.path)
	shell.Add("git", "-C", action.path, "config", "--local", "gc.auto", "0")
	if err := shell.Run(ctx, nil, nil); err != nil {
		return err
	}

	action.Noticef("Configuring git repository credentials")

	shell.Add("git", "-C", action.path, "config", "--local", "--add",
		fmt.Sprintf("url.%s.insteadof", server.String()), fmt.Sprintf("git@%s", server.Host))
	shell.Add("git", "-C", action.path, "config", "--local", "--add",
		fmt.Sprintf("url.%s.insteadof", server.String()), fmt.Sprintf("ssh://git@%s", server.Host))
	shell.Add("git", "-C", action.path, "config", "--local", "--add",
		fmt.Sprintf("url.%s.insteadof", server.String()), fmt.Sprintf("git://%s", server.Host))
	if err := shell.Run(ctx, nil, nil); err != nil {
		return err
	}

	enc := base64.StdEncoding
	header := fmt.Sprintf("Authorization: Basic %s", enc.EncodeToString(fmt.Appendf(nil, "x-access-token:%s", env.Token)))

	shell.Add("git", "-C", action.path, "config", "--local", "--add", fmt.Sprintf("http.%s.extraheader", env.ServerURL), header)
	if err := shell.Run(ctx, nil, nil); err != nil {
		return err
	}

	origin := "origin"

	shell.Add("git", "-C", action.path, "remote", "add", origin, action.repository)
	if err := shell.Run(ctx, nil, nil); err != nil {
		return err
	}

	shell.Add("git", "-C", action.path, "ls-remote", origin, action.reference)
	var stdout strings.Builder = strings.Builder{}
	if err := shell.Run(ctx, &stdout, nil); err != nil {
		return err
	}
	lines := strings.Split(stdout.String(), "\t")
	if len(lines) < 2 {
		return fmt.Errorf("git ls-remore resolved nothing")
	}
	sha := strings.TrimSpace(lines[0])
	ref := strings.TrimSpace(lines[1])

	var name string
	var ok bool
	if name, ok = strings.CutPrefix(ref, "refs/heads/"); ok {
		remote := fmt.Sprintf("refs/remotes/%s/%s", origin, name)
		branch := name

		action.Debugf("Checking out branch %s@%s", name, sha)

		shell.Add("git", "-C", action.path, "fetch", "--no-tags", "--prune", "--no-recurse-submodules", "--depth=1",
			origin, fmt.Sprintf("+%s:%s", sha, remote))
		shell.Add("git", "-C", action.path, "checkout", "--force", "-B", branch, remote)
	} else if name, ok = strings.CutPrefix(ref, "refs/pull/"); ok {
		remote := fmt.Sprintf("refs/remotes/pull/%s", name)

		action.Debugf("Checking out pull-request %s@%s", name, sha)

		var branch string
		if len(env.BaseRef) != 0 {
			branch = env.BaseRef
		} else if len(env.HeadRef) != 0 {
			branch = env.HeadRef
		} else {
			return fmt.Errorf("pull request can not find base ref for branch")
		}

		shell.Add("git", "-C", action.path, "fetch", "--no-tags", "--prune", "--no-recurse-submodules", "--depth=1",
			origin, fmt.Sprintf("+%s:%s", sha, remote))
		shell.Add("git", "-C", action.path, "checkout", "--force", "-B", branch, remote)
	} else if name, ok = strings.CutPrefix(ref, "refs/tags/"); ok {
		remote := fmt.Sprintf("refs/tags/%s", name)

		action.Debugf("Checking out tag %s@%s", name, sha)

		shell.Add("git", "-C", action.path, "fetch", "--no-tags", "--prune", "--no-recurse-submodules", "--depth=1",
			origin, fmt.Sprintf("+%s:%s", sha, remote))
		shell.Add("git", "-C", action.path, "checkout", "--force", remote)
	} else {
		action.Debugf("Checking out detached head %s", ref)

		shell.Add("git", "-C", action.path, "fetch", "--no-tags", "--prune", "--no-recurse-submodules", "--depth=1",
			origin, ref)
		shell.Add("git", "-C", action.path, "checkout", "--force", ref)
	}

	if err := shell.Run(ctx, nil, nil); err != nil {
		return err
	}

	return nil
}

type Shell struct {
	action *sdk.Action
	args   [][]string
}

func (sh *Shell) Add(args ...string) { sh.args = append(sh.args, args) }
func (sh *Shell) Run(ctx context.Context, stdout io.Writer, stderr io.Writer) error {
	for _, args := range sh.args {
		if sh.action != nil {
			sh.action.Debugf("exec: %s", strings.Join(args, " "))
		}
		cmd := exec.CommandContext(ctx, args[0], args[1:]...)
		cmd.Stdout = stdout
		cmd.Stderr = stderr
		if err := cmd.Run(); err != nil {
			return err
		}
	}
	sh.args = [][]string{}
	return nil
}