package worker

import (
	"bytes"
	"context"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// GitOperations provides git clone, commit, and push functionality
// for the build executor. It uses os/exec to run git commands.
type GitOperations struct {
	giteaToken string
	gitUser    string
	gitEmail   string
	logger     *slog.Logger
}

// GitOperationsConfig configures git operations.
type GitOperationsConfig struct {
	// GiteaToken is the token for HTTPS clone/push authentication.
	GiteaToken string

	// GitUser is the git commit author name.
	GitUser string

	// GitEmail is the git commit author email.
	GitEmail string

	Logger *slog.Logger
}

// NewGitOperations creates a new git operations helper.
func NewGitOperations(cfg GitOperationsConfig) *GitOperations {
	if cfg.GitUser == "" {
		cfg.GitUser = "rdev-worker"
	}
	if cfg.GitEmail == "" {
		cfg.GitEmail = "worker@threesix.ai"
	}
	if cfg.Logger == nil {
		cfg.Logger = slog.Default()
	}
	return &GitOperations{
		giteaToken: cfg.GiteaToken,
		gitUser:    cfg.GitUser,
		gitEmail:   cfg.GitEmail,
		logger:     cfg.Logger.With("component", "git-ops"),
	}
}

// CloneToTemp clones a repository to a temporary directory.
// Returns the clone directory and a cleanup function.
func (g *GitOperations) CloneToTemp(ctx context.Context, gitURL string) (string, func(), error) {
	tmpDir, err := os.MkdirTemp("", "rdev-build-*")
	if err != nil {
		return "", nil, fmt.Errorf("create temp dir: %w", err)
	}

	cleanup := func() {
		if err := os.RemoveAll(tmpDir); err != nil {
			g.logger.Warn("failed to cleanup temp dir", "dir", tmpDir, "error", err)
		}
	}

	// Inject token into clone URL for authentication
	authURL := g.injectToken(gitURL)

	if err := g.runGit(ctx, tmpDir, "clone", authURL, "."); err != nil {
		cleanup()
		return "", nil, fmt.Errorf("git clone: %w", err)
	}

	// Configure git user for commits
	if err := g.runGit(ctx, tmpDir, "config", "user.name", g.gitUser); err != nil {
		cleanup()
		return "", nil, fmt.Errorf("git config user.name: %w", err)
	}
	if err := g.runGit(ctx, tmpDir, "config", "user.email", g.gitEmail); err != nil {
		cleanup()
		return "", nil, fmt.Errorf("git config user.email: %w", err)
	}

	g.logger.Info("cloned repository", "url", gitURL, "dir", tmpDir)
	return tmpDir, cleanup, nil
}

// CommitAndPush stages all changes, commits, and optionally pushes.
// Returns the commit SHA and list of changed files.
func (g *GitOperations) CommitAndPush(ctx context.Context, dir, message string, push bool) (string, []string, error) {
	// Stage all changes
	if err := g.runGit(ctx, dir, "add", "-A"); err != nil {
		return "", nil, fmt.Errorf("git add: %w", err)
	}

	// Check if there are changes to commit
	status, err := g.runGitOutput(ctx, dir, "status", "--porcelain")
	if err != nil {
		return "", nil, fmt.Errorf("git status: %w", err)
	}
	if strings.TrimSpace(status) == "" {
		g.logger.Info("no changes to commit", "dir", dir)
		return "", nil, nil
	}

	// Get list of changed files
	diffOutput, err := g.runGitOutput(ctx, dir, "diff", "--cached", "--name-only")
	if err != nil {
		return "", nil, fmt.Errorf("git diff: %w", err)
	}
	var filesChanged []string
	for _, f := range strings.Split(strings.TrimSpace(diffOutput), "\n") {
		if f != "" {
			filesChanged = append(filesChanged, f)
		}
	}

	// Commit
	if err := g.runGit(ctx, dir, "commit", "-m", message); err != nil {
		return "", nil, fmt.Errorf("git commit: %w", err)
	}

	// Get commit SHA
	sha, err := g.runGitOutput(ctx, dir, "rev-parse", "HEAD")
	if err != nil {
		return "", nil, fmt.Errorf("git rev-parse: %w", err)
	}
	sha = strings.TrimSpace(sha)

	g.logger.Info("committed changes",
		"sha", sha,
		"files", len(filesChanged),
	)

	// Push if requested
	if push {
		if err := g.runGit(ctx, dir, "push"); err != nil {
			return sha, filesChanged, fmt.Errorf("git push: %w", err)
		}
		g.logger.Info("pushed changes", "sha", sha)
	}

	return sha, filesChanged, nil
}

// injectToken adds the Gitea token to an HTTPS git URL for authentication.
// Converts "https://git.example.com/org/repo.git" to
// "https://token@git.example.com/org/repo.git".
func (g *GitOperations) injectToken(gitURL string) string {
	if g.giteaToken == "" {
		return gitURL
	}
	// Handle https:// URLs
	if strings.HasPrefix(gitURL, "https://") {
		return "https://" + g.giteaToken + "@" + gitURL[len("https://"):]
	}
	if strings.HasPrefix(gitURL, "http://") {
		return "http://" + g.giteaToken + "@" + gitURL[len("http://"):]
	}
	return gitURL
}

// gitEnv returns a minimal environment for git subprocesses.
// Only PATH and HOME are inherited; all other host env vars are excluded
// to prevent credential or config leakage.
func gitEnv() []string {
	env := []string{"GIT_TERMINAL_PROMPT=0"}
	for _, key := range []string{"PATH", "HOME"} {
		if v := os.Getenv(key); v != "" {
			env = append(env, key+"="+v)
		}
	}
	return env
}

// runGit executes a git command in the given directory.
func (g *GitOperations) runGit(ctx context.Context, dir string, args ...string) error {
	cmd := exec.CommandContext(ctx, "git", args...)
	cmd.Dir = dir
	cmd.Env = gitEnv()

	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		// Redact token from error messages
		errMsg := g.redactToken(stderr.String())
		return fmt.Errorf("%s: %s", err, errMsg)
	}
	return nil
}

// runGitOutput executes a git command and returns its stdout.
func (g *GitOperations) runGitOutput(ctx context.Context, dir string, args ...string) (string, error) {
	cmd := exec.CommandContext(ctx, "git", args...)
	cmd.Dir = dir
	cmd.Env = gitEnv()

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		errMsg := g.redactToken(stderr.String())
		return "", fmt.Errorf("%s: %s", err, errMsg)
	}
	return stdout.String(), nil
}

// redactToken removes the Gitea token from log/error output.
func (g *GitOperations) redactToken(s string) string {
	if g.giteaToken == "" {
		return s
	}
	return strings.ReplaceAll(s, g.giteaToken, "[REDACTED]")
}

// EnsureGitDir verifies that the given path is a valid git repository.
func (g *GitOperations) EnsureGitDir(dir string) error {
	gitDir := filepath.Join(dir, ".git")
	info, err := os.Stat(gitDir)
	if err != nil {
		return fmt.Errorf("not a git repository: %w", err)
	}
	if !info.IsDir() {
		return fmt.Errorf("not a git repository: .git is not a directory")
	}
	return nil
}