package bundle

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

func WriteBundle(opts WriteBundleOptions) (Manifest, error) {
	root, err := cleanBundleRoot(opts.Root)
	if err != nil {
		return Manifest{}, err
	}
	if opts.ID == "" {
		return Manifest{}, fmt.Errorf("id is required")
	}
	if len(opts.Files) == 0 {
		return Manifest{}, fmt.Errorf("files is required")
	}

	parent := filepath.Dir(root)
	if err := os.MkdirAll(parent, 0o755); err != nil {
		return Manifest{}, fmt.Errorf("create bundle parent: %w", err)
	}
	if !opts.Overwrite {
		if _, err := os.Lstat(root); err == nil {
			return Manifest{}, fmt.Errorf("bundle root %q already exists", root)
		} else if !errors.Is(err, os.ErrNotExist) {
			return Manifest{}, fmt.Errorf("stat bundle root: %w", err)
		}
	}

	tempRoot, err := os.MkdirTemp(parent, "."+filepath.Base(root)+"-*.tmp")
	if err != nil {
		return Manifest{}, fmt.Errorf("create bundle temp root: %w", err)
	}
	removeTemp := true
	defer func() {
		if removeTemp {
			_ = os.RemoveAll(tempRoot)
		}
	}()

	paths, err := copyBundleFiles(tempRoot, opts.Files)
	if err != nil {
		return Manifest{}, err
	}
	manifest, err := BuildManifest(BuildOptions{
		Root:    tempRoot,
		ID:      opts.ID,
		Created: opts.Created,
		Files:   paths,
	})
	if err != nil {
		return Manifest{}, err
	}
	if err := WriteManifest(tempRoot, manifest, WriteManifestOptions{}); err != nil {
		return Manifest{}, err
	}
	if err := ValidateBundle(tempRoot, manifest); err != nil {
		return Manifest{}, err
	}

	if err := promoteBundleRoot(tempRoot, root, opts.Overwrite); err != nil {
		return Manifest{}, err
	}
	removeTemp = false
	return manifest, nil
}

func cleanBundleRoot(root string) (string, error) {
	if root == "" {
		return "", fmt.Errorf("root is required")
	}
	return filepath.Clean(root), nil
}

func copyBundleFiles(root string, files []BundleFile) ([]string, error) {
	paths := make([]string, 0, len(files))
	seen := make(map[string]struct{}, len(files))
	for index, file := range files {
		if file.SourcePath == "" {
			return nil, fmt.Errorf("files[%d].source_path is required", index)
		}
		if err := ValidateSourcePath(file.Path); err != nil {
			return nil, fmt.Errorf("files[%d].path: %w", index, err)
		}
		if _, exists := seen[file.Path]; exists {
			return nil, fmt.Errorf("files[%d].path duplicates %q", index, file.Path)
		}
		seen[file.Path] = struct{}{}
		if err := copyBundleFile(root, file); err != nil {
			return nil, fmt.Errorf("files[%d]: %w", index, err)
		}
		paths = append(paths, file.Path)
	}
	return paths, nil
}

func copyBundleFile(root string, file BundleFile) error {
	info, err := os.Lstat(file.SourcePath)
	if err != nil {
		return fmt.Errorf("stat source %q: %w", file.SourcePath, err)
	}
	if !info.Mode().IsRegular() {
		return fmt.Errorf("source %q must be a regular file", file.SourcePath)
	}
	destination := filepath.Join(root, filepath.FromSlash(file.Path))
	if err := os.MkdirAll(filepath.Dir(destination), 0o755); err != nil {
		return fmt.Errorf("create destination directory: %w", err)
	}

	source, err := os.Open(file.SourcePath)
	if err != nil {
		return fmt.Errorf("open source %q: %w", file.SourcePath, err)
	}
	defer source.Close()

	mode := info.Mode().Perm()
	if mode == 0 {
		mode = 0o600
	}
	target, err := os.OpenFile(destination, os.O_WRONLY|os.O_CREATE|os.O_EXCL, mode)
	if err != nil {
		return fmt.Errorf("create destination %q: %w", file.Path, err)
	}
	if _, err := io.Copy(target, source); err != nil {
		_ = target.Close()
		return fmt.Errorf("copy to destination %q: %w", file.Path, err)
	}
	if err := target.Close(); err != nil {
		return fmt.Errorf("close destination %q: %w", file.Path, err)
	}
	return nil
}

func promoteBundleRoot(tempRoot, root string, overwrite bool) error {
	if !overwrite {
		if _, err := os.Lstat(root); err == nil {
			return fmt.Errorf("bundle root %q already exists", root)
		} else if !errors.Is(err, os.ErrNotExist) {
			return fmt.Errorf("stat bundle root: %w", err)
		}
		if err := os.Rename(tempRoot, root); err != nil {
			return fmt.Errorf("promote bundle root: %w", err)
		}
		return nil
	}
	if _, err := os.Lstat(root); errors.Is(err, os.ErrNotExist) {
		if err := os.Rename(tempRoot, root); err != nil {
			return fmt.Errorf("promote bundle root: %w", err)
		}
		return nil
	} else if err != nil {
		return fmt.Errorf("stat bundle root: %w", err)
	}

	backupRoot, err := reserveSiblingPath(filepath.Dir(root), "."+filepath.Base(root)+"-backup-*.tmp")
	if err != nil {
		return err
	}
	if err := os.Rename(root, backupRoot); err != nil {
		return fmt.Errorf("move existing bundle root: %w", err)
	}
	if err := os.Rename(tempRoot, root); err != nil {
		restoreErr := os.Rename(backupRoot, root)
		if restoreErr != nil {
			return fmt.Errorf("promote bundle root: %w; restore existing bundle root: %v", err, restoreErr)
		}
		return fmt.Errorf("promote bundle root: %w", err)
	}
	_ = os.RemoveAll(backupRoot)
	return nil
}

func reserveSiblingPath(parent, pattern string) (string, error) {
	path, err := os.MkdirTemp(parent, pattern)
	if err != nil {
		return "", fmt.Errorf("reserve backup path: %w", err)
	}
	if err := os.Remove(path); err != nil {
		return "", fmt.Errorf("reserve backup path: %w", err)
	}
	return path, nil
}