package runtimebundle

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"strings"

	toml "github.com/pelletier/go-toml"
)

type Manifest struct {
	Version       string   `toml:"version"`
	URL           string   `toml:"url"`
	SHA256        string   `toml:"sha256"`
	BundleRoot    string   `toml:"bundle_root"`
	RequiredPaths []string `toml:"required_paths"`
}

func LoadManifest(path string) (Manifest, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return Manifest{}, err
	}
	var manifest Manifest
	if err := toml.Unmarshal(data, &manifest); err != nil {
		return Manifest{}, err
	}
	manifest.BundleRoot = strings.TrimSpace(manifest.BundleRoot)
	manifest.URL = strings.TrimSpace(manifest.URL)
	manifest.SHA256 = strings.ToLower(strings.TrimSpace(manifest.SHA256))
	for i, required := range manifest.RequiredPaths {
		manifest.RequiredPaths[i] = filepath.Clean(strings.TrimSpace(required))
	}
	sort.Strings(manifest.RequiredPaths)
	if len(manifest.RequiredPaths) == 0 {
		return Manifest{}, fmt.Errorf("runtime bundle manifest %s has no required_paths", path)
	}
	return manifest, nil
}

func Bootstrap(ctx context.Context, manifest Manifest, manifestPath, outDir string) error {
	if manifest.URL == "" {
		return fmt.Errorf("runtime bundle manifest %s has no url; publish a runtime bundle and update the manifest", manifestPath)
	}
	if manifest.SHA256 == "" {
		return fmt.Errorf("runtime bundle manifest %s has no sha256", manifestPath)
	}
	manifestDir := filepath.Dir(manifestPath)
	parentDir := filepath.Dir(outDir)
	if err := os.MkdirAll(parentDir, 0o755); err != nil {
		return err
	}

	workDir, err := os.MkdirTemp(parentDir, ".runtime-bundle-*")
	if err != nil {
		return err
	}
	defer os.RemoveAll(workDir)

	archivePath := filepath.Join(workDir, "bundle.tar.gz")
	if err := downloadArchive(ctx, resolveSource(manifestDir, manifest.URL), archivePath); err != nil {
		return err
	}
	sum, err := fileSHA256(archivePath)
	if err != nil {
		return err
	}
	if sum != manifest.SHA256 {
		return fmt.Errorf("runtime bundle checksum mismatch: got %s want %s", sum, manifest.SHA256)
	}

	extractDir := filepath.Join(workDir, "extract")
	if err := extractTarGz(archivePath, extractDir); err != nil {
		return err
	}

	bundleDir := extractDir
	if manifest.BundleRoot != "" {
		bundleDir = filepath.Join(extractDir, manifest.BundleRoot)
	}
	if err := ValidateBundle(bundleDir, manifest.RequiredPaths); err != nil {
		return err
	}

	stageDir := filepath.Join(workDir, "stage")
	if err := os.Rename(bundleDir, stageDir); err != nil {
		return err
	}

	if err := os.RemoveAll(outDir); err != nil {
		return err
	}
	if err := os.Rename(stageDir, outDir); err != nil {
		return err
	}
	return nil
}

func ValidateBundle(bundleDir string, requiredPaths []string) error {
	for _, rel := range requiredPaths {
		if rel == "." || strings.HasPrefix(rel, "..") {
			return fmt.Errorf("invalid required bundle path: %s", rel)
		}
		if _, err := os.Stat(filepath.Join(bundleDir, rel)); err != nil {
			return fmt.Errorf("runtime bundle missing %s", rel)
		}
	}
	return nil
}

func Package(runtimeDir, outArchive string, manifest Manifest) (string, error) {
	if err := ValidateBundle(runtimeDir, manifest.RequiredPaths); err != nil {
		return "", err
	}
	if err := os.MkdirAll(filepath.Dir(outArchive), 0o755); err != nil {
		return "", err
	}
	file, err := os.Create(outArchive)
	if err != nil {
		return "", err
	}
	defer file.Close()

	hash := sha256.New()
	multi := io.MultiWriter(file, hash)
	gz := gzip.NewWriter(multi)
	defer gz.Close()
	tw := tar.NewWriter(gz)
	defer tw.Close()

	for _, rel := range manifest.RequiredPaths {
		if err := addPathToArchive(tw, runtimeDir, manifest.BundleRoot, rel); err != nil {
			return "", err
		}
	}
	if err := tw.Close(); err != nil {
		return "", err
	}
	if err := gz.Close(); err != nil {
		return "", err
	}
	return hex.EncodeToString(hash.Sum(nil)), nil
}

func addPathToArchive(tw *tar.Writer, runtimeDir, bundleRoot, rel string) error {
	srcPath := filepath.Join(runtimeDir, rel)
	info, err := os.Lstat(srcPath)
	if err != nil {
		return err
	}
	archiveName := rel
	if bundleRoot != "" {
		archiveName = filepath.Join(bundleRoot, rel)
	}
	if info.IsDir() {
		header, err := tar.FileInfoHeader(info, "")
		if err != nil {
			return err
		}
		header.Name = filepath.ToSlash(archiveName) + "/"
		if err := tw.WriteHeader(header); err != nil {
			return err
		}
		entries, err := os.ReadDir(srcPath)
		if err != nil {
			return err
		}
		for _, entry := range entries {
			childRel := filepath.Join(rel, entry.Name())
			if err := addPathToArchive(tw, runtimeDir, bundleRoot, childRel); err != nil {
				return err
			}
		}
		return nil
	}

	header, err := tar.FileInfoHeader(info, "")
	if err != nil {
		return err
	}
	header.Name = filepath.ToSlash(archiveName)
	if err := tw.WriteHeader(header); err != nil {
		return err
	}
	file, err := os.Open(srcPath)
	if err != nil {
		return err
	}
	defer file.Close()
	_, err = io.Copy(tw, file)
	return err
}

func resolveSource(manifestDir, source string) string {
	parsed, err := url.Parse(source)
	if err == nil && parsed.Scheme != "" {
		return source
	}
	if filepath.IsAbs(source) {
		return source
	}
	return filepath.Join(manifestDir, source)
}

func downloadArchive(ctx context.Context, source, dst string) error {
	switch {
	case strings.HasPrefix(source, "http://"), strings.HasPrefix(source, "https://"):
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, source, nil)
		if err != nil {
			return err
		}
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			return err
		}
		defer resp.Body.Close()
		if resp.StatusCode != http.StatusOK {
			return fmt.Errorf("download runtime bundle: %s", resp.Status)
		}
		return writeFileFromReader(dst, resp.Body)
	case strings.HasPrefix(source, "file://"):
		parsed, err := url.Parse(source)
		if err != nil {
			return err
		}
		return copyFile(parsed.Path, dst)
	default:
		return copyFile(source, dst)
	}
}

func writeFileFromReader(dst string, reader io.Reader) error {
	file, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer file.Close()
	_, err = io.Copy(file, reader)
	return err
}

func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()
	return writeFileFromReader(dst, in)
}

func extractTarGz(archivePath, outDir string) error {
	if err := os.MkdirAll(outDir, 0o755); err != nil {
		return err
	}
	file, err := os.Open(archivePath)
	if err != nil {
		return err
	}
	defer file.Close()
	gz, err := gzip.NewReader(file)
	if err != nil {
		return err
	}
	defer gz.Close()
	tr := tar.NewReader(gz)
	for {
		header, err := tr.Next()
		if err == io.EOF {
			return nil
		}
		if err != nil {
			return err
		}
		name := filepath.Clean(header.Name)
		if name == "." || strings.HasPrefix(name, "..") || filepath.IsAbs(name) {
			return fmt.Errorf("invalid archive entry: %s", header.Name)
		}
		target := filepath.Join(outDir, name)
		switch header.Typeflag {
		case tar.TypeDir:
			if err := os.MkdirAll(target, os.FileMode(header.Mode)); err != nil {
				return err
			}
		case tar.TypeReg, tar.TypeRegA:
			if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
				return err
			}
			file, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR|os.O_TRUNC, os.FileMode(header.Mode))
			if err != nil {
				return err
			}
			if _, err := io.Copy(file, tr); err != nil {
				file.Close()
				return err
			}
			if err := file.Close(); err != nil {
				return err
			}
		default:
			return fmt.Errorf("unsupported archive entry type: %s", header.Name)
		}
	}
}

func fileSHA256(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()
	hash := sha256.New()
	if _, err := io.Copy(hash, file); err != nil {
		return "", err
	}
	return hex.EncodeToString(hash.Sum(nil)), nil
}