package deploy

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

type Manager struct {
	deployRoot     string
	releaseRoot    string
	releasesToKeep int
	logger         *slog.Logger
}

func NewManager(deployRoot, releaseRoot string, releasesToKeep int, logger *slog.Logger) *Manager {
	return &Manager{
		deployRoot:     deployRoot,
		releaseRoot:    releaseRoot,
		releasesToKeep: releasesToKeep,
		logger:         logger,
	}
}

func (m *Manager) Deploy(ctx context.Context, username, project string, r io.Reader) (string, error) {
	releaseID := time.Now().UTC().Format("20060102T150405")

	m.logger.Info("starting deployment",
		slog.String("username", username),
		slog.String("project", project),
		slog.String("release_id", releaseID))

	tmpFile, err := os.CreateTemp("", fmt.Sprintf("deployer-upload-%s-%s-*.tar.gz", username, releaseID))
	if err != nil {
		return "", fmt.Errorf("failed to create temp file: %w", err)
	}
	defer os.Remove(tmpFile.Name())
	defer tmpFile.Close()

	written, err := io.Copy(tmpFile, r)
	if err != nil {
		return "", fmt.Errorf("failed to write tarball: %w", err)
	}

	m.logger.Debug("tarball saved to temp file",
		slog.String("path", tmpFile.Name()),
		slog.Int64("bytes", written))

	if _, err := tmpFile.Seek(0, 0); err != nil {
		return "", fmt.Errorf("failed to seek temp file: %w", err)
	}

	releasePath := filepath.Join(m.releaseRoot, username, project, releaseID)
	if err := os.MkdirAll(releasePath, 0755); err != nil {
		return "", fmt.Errorf("failed to create release directory: %w", err)
	}

	if err := m.extractTarball(tmpFile, releasePath); err != nil {
		os.RemoveAll(releasePath)
		return "", fmt.Errorf("failed to extract tarball: %w", err)
	}

	if err := m.lockdownPermissions(releasePath); err != nil {
		return "", fmt.Errorf("failed to set read-only permissions: %w", err)
	}

	deployPath := filepath.Join(m.deployRoot, username, project)
	deployParentDir := filepath.Dir(deployPath)
	if err := os.MkdirAll(deployParentDir, 0755); err != nil {
		return "", fmt.Errorf("failed to create deploy parent directory: %w", err)
	}

	relPath, err := filepath.Rel(deployParentDir, releasePath)
	if err != nil {
		return "", fmt.Errorf("failed to calculate relative path: %w", err)
	}

	tmpLink := deployPath + ".tmp." + releaseID
	if err := os.Symlink(relPath, tmpLink); err != nil {
		return "", fmt.Errorf("failed to create temporary symlink: %w", err)
	}

	if err := os.Rename(tmpLink, deployPath); err != nil {
		os.Remove(tmpLink)
		return "", fmt.Errorf("failed to swap symlink: %w", err)
	}

	m.logger.Info("deployment successful",
		slog.String("username", username),
		slog.String("project", project),
		slog.String("release_id", releaseID))

	if err := m.cleanupOldReleases(username, project); err != nil {
		m.logger.Warn("failed to cleanup old releases",
			slog.String("error", err.Error()))
	}

	return releaseID, nil
}

func (m *Manager) extractTarball(r io.Reader, destDir string) error {
	gzr, err := gzip.NewReader(r)
	if err != nil {
		return fmt.Errorf("failed to create gzip reader: %w", err)
	}
	defer gzr.Close()

	tr := tar.NewReader(gzr)

	for {
		header, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return fmt.Errorf("failed to read tar header: %w", err)
		}

		if err := validateTarPath(header.Name); err != nil {
			return err
		}

		cleanName := filepath.Clean(header.Name)
		if cleanName == "." || cleanName == ".." {
			continue
		}

		target := filepath.Join(destDir, cleanName)

		if !strings.HasPrefix(target, filepath.Clean(destDir)+string(os.PathSeparator)) {
			return fmt.Errorf("path traversal detected: %s", header.Name)
		}

		switch header.Typeflag {
		case tar.TypeDir:
			if err := os.MkdirAll(target, 0755); err != nil {
				return fmt.Errorf("failed to create directory: %w", err)
			}
		case tar.TypeReg:
			if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
				return fmt.Errorf("failed to create parent directory: %w", err)
			}

			f, err := os.OpenFile(target, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.FileMode(header.Mode))
			if err != nil {
				return fmt.Errorf("failed to create file: %w", err)
			}

			if _, err := io.Copy(f, tr); err != nil {
				f.Close()
				return fmt.Errorf("failed to write file: %w", err)
			}
			f.Close()
		}
	}

	return nil
}

func validateTarPath(path string) error {
	clean := filepath.Clean(path)
	
	parts := strings.Split(clean, string(filepath.Separator))
	for _, part := range parts {
		if part == ".." {
			return fmt.Errorf("path contains '..' component which is not allowed: %s", path)
		}
	}

	if filepath.IsAbs(path) {
		return fmt.Errorf("absolute paths not allowed: %s", path)
	}

	return nil
}

func (m *Manager) lockdownPermissions(root string) error {
	return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			if err := os.Chmod(path, 0550); err != nil {
				return fmt.Errorf("failed to chmod directory %s: %w", path, err)
			}
		} else {
			if err := os.Chmod(path, 0440); err != nil {
				return fmt.Errorf("failed to chmod file %s: %w", path, err)
			}
		}

		return nil
	})
}

func (m *Manager) cleanupOldReleases(username, project string) error {
	releasesDir := filepath.Join(m.releaseRoot, username, project)

	entries, err := os.ReadDir(releasesDir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("failed to read releases directory: %w", err)
	}

	var releases []os.DirEntry
	for _, entry := range entries {
		if entry.IsDir() {
			releases = append(releases, entry)
		}
	}

	if len(releases) <= m.releasesToKeep {
		return nil
	}

	sort.Slice(releases, func(i, j int) bool {
		return releases[i].Name() > releases[j].Name()
	})

	for i := m.releasesToKeep; i < len(releases); i++ {
		oldReleasePath := filepath.Join(releasesDir, releases[i].Name())
		m.logger.Info("removing old release",
			slog.String("path", oldReleasePath))
		if err := os.RemoveAll(oldReleasePath); err != nil {
			m.logger.Warn("failed to remove old release",
				slog.String("path", oldReleasePath),
				slog.String("error", err.Error()))
		}
	}

	return nil
}