// Package updatepackage reads the exact repack ZIP format currently emitted by deploy.
package updatepackage

import (
	"archive/zip"
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"strings"

	"yms-daemon/internal/filestore"
)

const (
	manifestName         = "artifact-selection.json"
	backendArtifactKind  = "BACKEND"
	nativeArtifactType   = "native"
	maximumManifestBytes = 1 << 20
)

// BackendNativePackage is an opened repack ZIP containing one exact native backend artifact.
type BackendNativePackage struct {
	archive       *zip.ReadCloser
	artifactEntry *zip.File

	PackagePath   string
	PackageSHA256 string
	CustomerCode  string
	VersionID     string
	ArtifactID    int64
	FileName      string
	Identity      filestore.Identity
}

// OpenBackendNative validates the ZIP structure and selects one explicitly declared native backend artifact.
func OpenBackendNative(packagePath string) (*BackendNativePackage, error) {
	if err := validateAbsoluteRegularFile(packagePath, "update package"); err != nil {
		return nil, err
	}
	packageDigest, err := hashFile(packagePath)
	if err != nil {
		return nil, err
	}

	archive, err := zip.OpenReader(packagePath)
	if err != nil {
		return nil, fmt.Errorf("open update package ZIP %s: %w", packagePath, err)
	}
	closeOnError := func(cause error) (*BackendNativePackage, error) {
		return nil, errors.Join(cause, archive.Close())
	}

	entries, err := validateEntries(archive.File)
	if err != nil {
		return closeOnError(err)
	}
	manifestEntry, found := entries[manifestName]
	if !found {
		return closeOnError(errors.New("update package is missing artifact-selection.json"))
	}
	manifest, err := decodeManifest(manifestEntry)
	if err != nil {
		return closeOnError(err)
	}
	selected, err := selectNativeBackend(manifest.BackendArtifacts)
	if err != nil {
		return closeOnError(err)
	}
	if err := validateRootFileName(selected.FileName); err != nil {
		return closeOnError(fmt.Errorf("invalid backendArtifacts.fileName: %w", err))
	}
	artifactEntry, found := entries[selected.FileName]
	if !found {
		return closeOnError(fmt.Errorf("native backend artifact declared by backendArtifacts.fileName is missing: %s", selected.FileName))
	}
	if artifactEntry.FileInfo().IsDir() {
		return closeOnError(fmt.Errorf("native backend artifact is not a file: %s", selected.FileName))
	}
	identity := filestore.Identity{
		Size:   int64(artifactEntry.UncompressedSize64),
		SHA256: selected.SHA256,
	}
	if err := identity.Validate(); err != nil {
		return closeOnError(fmt.Errorf("invalid backendArtifacts.sha256: %w", err))
	}

	return &BackendNativePackage{
		archive:       archive,
		artifactEntry: artifactEntry,
		PackagePath:   packagePath,
		PackageSHA256: packageDigest,
		CustomerCode:  manifest.CustomerCode,
		VersionID:     manifest.VersionID,
		ArtifactID:    selected.ID,
		FileName:      selected.FileName,
		Identity:      identity,
	}, nil
}

// Close releases the opened ZIP file.
func (p *BackendNativePackage) Close() error {
	if p == nil || p.archive == nil {
		return nil
	}
	archive := p.archive
	p.archive = nil
	p.artifactEntry = nil
	return archive.Close()
}

// ExtractArtifact writes the selected JAR to destination and verifies size and SHA-256 before publishing it.
func (p *BackendNativePackage) ExtractArtifact(destination string) error {
	if p == nil || p.archive == nil || p.artifactEntry == nil {
		return errors.New("native backend update package is not open")
	}
	if !filepath.IsAbs(destination) || filepath.Clean(destination) != destination {
		return errors.New("native backend extraction destination must be a clean absolute path")
	}
	parent := filepath.Dir(destination)
	if err := os.MkdirAll(parent, 0o750); err != nil {
		return fmt.Errorf("create native backend extraction directory: %w", err)
	}
	parentInfo, err := os.Lstat(parent)
	if err != nil {
		return fmt.Errorf("inspect native backend extraction directory: %w", err)
	}
	if !parentInfo.IsDir() || parentInfo.Mode()&os.ModeSymlink != 0 {
		return fmt.Errorf("native backend extraction parent is not a direct directory: %s", parent)
	}

	source, err := p.artifactEntry.Open()
	if err != nil {
		return fmt.Errorf("open native backend artifact %s: %w", p.FileName, err)
	}
	temporary, err := os.CreateTemp(parent, ".backend-jar-*")
	if err != nil {
		_ = source.Close()
		return fmt.Errorf("create native backend extraction file: %w", err)
	}
	temporaryPath := temporary.Name()
	defer os.Remove(temporaryPath)
	if err := temporary.Chmod(0o640); err != nil {
		_ = source.Close()
		_ = temporary.Close()
		return fmt.Errorf("set native backend extraction permissions: %w", err)
	}

	digest := sha256.New()
	written, copyErr := io.Copy(io.MultiWriter(temporary, digest), source)
	closeSourceErr := source.Close()
	if err := errors.Join(copyErr, closeSourceErr); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("extract native backend artifact: %w", err)
	}
	if written != p.Identity.Size {
		_ = temporary.Close()
		return fmt.Errorf("native backend artifact size mismatch: got %d, want %d", written, p.Identity.Size)
	}
	actualDigest := hex.EncodeToString(digest.Sum(nil))
	if !strings.EqualFold(actualDigest, p.Identity.SHA256) {
		_ = temporary.Close()
		return fmt.Errorf("native backend artifact SHA-256 mismatch: got %s, want %s", actualDigest, p.Identity.SHA256)
	}
	if err := temporary.Sync(); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("flush native backend extraction file: %w", err)
	}
	if err := temporary.Close(); err != nil {
		return fmt.Errorf("close native backend extraction file: %w", err)
	}
	if err := os.Rename(temporaryPath, destination); err != nil {
		return fmt.Errorf("publish native backend extraction file: %w", err)
	}
	return syncDirectory(parent)
}

type artifactSelectionManifest struct {
	CustomerCode        string             `json:"customerCode"`
	CustomerDisplayName *string            `json:"customerDisplayName"`
	VersionID           string             `json:"versionId"`
	Items               []string           `json:"items"`
	BackendArtifacts    []manifestArtifact `json:"backendArtifacts"`
	FrontendArtifacts   []manifestArtifact `json:"frontendArtifacts"`
	NodeSSRArtifacts    []manifestArtifact `json:"nodeSsrArtifacts"`
	Remark              *string            `json:"remark"`
}

type manifestArtifact struct {
	ID           int64   `json:"id"`
	VersionCode  *string `json:"versionCode"`
	ArtifactKind string  `json:"artifactKind"`
	Type         string  `json:"type"`
	SelectedType string  `json:"selectedType"`
	Platform     *string `json:"platform"`
	FileName     string  `json:"fileName"`
	FilePath     *string `json:"filePath"`
	SHA256       string  `json:"sha256"`
	ImageRef     *string `json:"imageRef"`
}

func decodeManifest(entry *zip.File) (artifactSelectionManifest, error) {
	if entry.FileInfo().IsDir() {
		return artifactSelectionManifest{}, errors.New("artifact-selection.json is not a file")
	}
	if entry.UncompressedSize64 > maximumManifestBytes {
		return artifactSelectionManifest{}, errors.New("artifact-selection.json exceeds size limit")
	}
	reader, err := entry.Open()
	if err != nil {
		return artifactSelectionManifest{}, fmt.Errorf("open artifact-selection.json: %w", err)
	}
	defer reader.Close()

	document, err := io.ReadAll(io.LimitReader(reader, maximumManifestBytes+1))
	if err != nil {
		return artifactSelectionManifest{}, fmt.Errorf("read artifact-selection.json: %w", err)
	}
	if len(document) > maximumManifestBytes {
		return artifactSelectionManifest{}, errors.New("artifact-selection.json exceeds size limit")
	}
	if err := validateExactManifestJSON(document); err != nil {
		return artifactSelectionManifest{}, fmt.Errorf("validate artifact-selection.json keys: %w", err)
	}

	var manifest artifactSelectionManifest
	decoder := json.NewDecoder(bytes.NewReader(document))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&manifest); err != nil {
		return artifactSelectionManifest{}, fmt.Errorf("decode artifact-selection.json: %w", err)
	}
	if err := ensureJSONEnd(decoder); err != nil {
		return artifactSelectionManifest{}, err
	}
	if strings.TrimSpace(manifest.CustomerCode) == "" || strings.TrimSpace(manifest.VersionID) == "" {
		return artifactSelectionManifest{}, errors.New("artifact-selection.json customerCode and versionId are required")
	}
	return manifest, nil
}

var rootManifestKeys = map[string]struct{}{
	"customerCode":        {},
	"customerDisplayName": {},
	"versionId":           {},
	"items":               {},
	"backendArtifacts":    {},
	"frontendArtifacts":   {},
	"nodeSsrArtifacts":    {},
	"remark":              {},
}

var artifactManifestKeys = map[string]struct{}{
	"id":           {},
	"versionCode":  {},
	"artifactKind": {},
	"type":         {},
	"selectedType": {},
	"platform":     {},
	"fileName":     {},
	"filePath":     {},
	"sha256":       {},
	"imageRef":     {},
}

func validateExactManifestJSON(document []byte) error {
	decoder := json.NewDecoder(bytes.NewReader(document))
	decoder.UseNumber()
	if err := validateObject(decoder, "", rootManifestKeys, true); err != nil {
		return err
	}
	return ensureJSONEnd(decoder)
}

func validateObject(decoder *json.Decoder, objectPath string, allowed map[string]struct{}, root bool) error {
	token, err := decoder.Token()
	if err != nil {
		return err
	}
	if delimiter, ok := token.(json.Delim); !ok || delimiter != '{' {
		return fmt.Errorf("%s must be a JSON object", displayJSONPath(objectPath))
	}
	seen := make(map[string]struct{}, len(allowed))
	for decoder.More() {
		keyToken, err := decoder.Token()
		if err != nil {
			return err
		}
		key, ok := keyToken.(string)
		if !ok {
			return fmt.Errorf("%s contains a non-string key", displayJSONPath(objectPath))
		}
		fieldPath := key
		if objectPath != "" {
			fieldPath = objectPath + "." + key
		}
		if _, duplicate := seen[key]; duplicate {
			return fmt.Errorf("duplicate JSON field %s", fieldPath)
		}
		seen[key] = struct{}{}
		if _, known := allowed[key]; !known {
			return fmt.Errorf("unknown JSON field %s", fieldPath)
		}
		if root && (key == "backendArtifacts" || key == "frontendArtifacts" || key == "nodeSsrArtifacts") {
			if err := validateArtifactArray(decoder, fieldPath); err != nil {
				return err
			}
			continue
		}
		if err := consumeJSONValue(decoder, fieldPath); err != nil {
			return err
		}
	}
	_, err = decoder.Token()
	return err
}

func validateArtifactArray(decoder *json.Decoder, arrayPath string) error {
	token, err := decoder.Token()
	if err != nil {
		return err
	}
	if delimiter, ok := token.(json.Delim); !ok || delimiter != '[' {
		return fmt.Errorf("%s must be a JSON array", arrayPath)
	}
	index := 0
	for decoder.More() {
		if err := validateObject(decoder, fmt.Sprintf("%s[%d]", arrayPath, index), artifactManifestKeys, false); err != nil {
			return err
		}
		index++
	}
	_, err = decoder.Token()
	return err
}

func consumeJSONValue(decoder *json.Decoder, valuePath string) error {
	token, err := decoder.Token()
	if err != nil {
		return err
	}
	delimiter, composite := token.(json.Delim)
	if !composite {
		return nil
	}
	switch delimiter {
	case '[':
		for decoder.More() {
			if err := consumeJSONValue(decoder, valuePath); err != nil {
				return err
			}
		}
		_, err = decoder.Token()
		return err
	case '{':
		seen := make(map[string]struct{})
		for decoder.More() {
			keyToken, err := decoder.Token()
			if err != nil {
				return err
			}
			key := keyToken.(string)
			if _, duplicate := seen[key]; duplicate {
				return fmt.Errorf("duplicate JSON field %s.%s", valuePath, key)
			}
			seen[key] = struct{}{}
			if err := consumeJSONValue(decoder, valuePath+"."+key); err != nil {
				return err
			}
		}
		_, err = decoder.Token()
		return err
	default:
		return fmt.Errorf("unexpected JSON delimiter %q at %s", delimiter, valuePath)
	}
}

func displayJSONPath(value string) string {
	if value == "" {
		return "artifact-selection.json"
	}
	return value
}

func ensureJSONEnd(decoder *json.Decoder) error {
	var trailing any
	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
		if err == nil {
			return errors.New("artifact-selection.json contains multiple JSON values")
		}
		return fmt.Errorf("decode artifact-selection.json trailing content: %w", err)
	}
	return nil
}

func selectNativeBackend(artifacts []manifestArtifact) (manifestArtifact, error) {
	var selected manifestArtifact
	count := 0
	for _, artifact := range artifacts {
		if artifact.ArtifactKind == backendArtifactKind && artifact.Type == nativeArtifactType && artifact.SelectedType == nativeArtifactType {
			selected = artifact
			count++
		}
	}
	if count != 1 {
		return manifestArtifact{}, fmt.Errorf("backendArtifacts must contain exactly one BACKEND native selection, got %d", count)
	}
	if selected.ID <= 0 || selected.FileName == "" || selected.SHA256 == "" {
		return manifestArtifact{}, errors.New("selected native backend artifact requires id, fileName and sha256")
	}
	return selected, nil
}

func validateEntries(files []*zip.File) (map[string]*zip.File, error) {
	entries := make(map[string]*zip.File, len(files))
	for _, file := range files {
		name := file.Name
		if name == "" || strings.Contains(name, "\\") || path.IsAbs(name) || path.Clean(name) != name || name == "." || strings.HasPrefix(name, "../") {
			return nil, fmt.Errorf("update package contains unsafe ZIP entry: %q", name)
		}
		if file.Mode()&os.ModeSymlink != 0 {
			return nil, fmt.Errorf("update package contains symbolic link entry: %s", name)
		}
		if _, duplicate := entries[name]; duplicate {
			return nil, fmt.Errorf("update package contains duplicate ZIP entry: %s", name)
		}
		entries[name] = file
	}
	return entries, nil
}

func validateRootFileName(name string) error {
	if name == "" || strings.ContainsAny(name, "/\\") || path.Clean(name) != name || name == "." || name == ".." {
		return fmt.Errorf("expected one exact ZIP root file name, got %q", name)
	}
	return nil
}

func validateAbsoluteRegularFile(filePath string, description string) error {
	if !filepath.IsAbs(filePath) || filepath.Clean(filePath) != filePath {
		return fmt.Errorf("%s path must be a clean absolute path", description)
	}
	info, err := os.Lstat(filePath)
	if err != nil {
		return fmt.Errorf("inspect %s %s: %w", description, filePath, err)
	}
	if !info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 {
		return fmt.Errorf("%s is not a direct regular file: %s", description, filePath)
	}
	return nil
}

func hashFile(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", fmt.Errorf("open update package for SHA-256: %w", err)
	}
	digest := sha256.New()
	_, copyErr := io.Copy(digest, file)
	closeErr := file.Close()
	if err := errors.Join(copyErr, closeErr); err != nil {
		return "", fmt.Errorf("hash update package: %w", err)
	}
	return hex.EncodeToString(digest.Sum(nil)), nil
}

func syncDirectory(directory string) error {
	file, err := os.Open(directory)
	if err != nil {
		return fmt.Errorf("open extraction directory for flush: %w", err)
	}
	syncErr := file.Sync()
	closeErr := file.Close()
	if err := errors.Join(syncErr, closeErr); err != nil {
		return fmt.Errorf("flush extraction directory: %w", err)
	}
	return nil
}