package updatepackage

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

	"yms-daemon/internal/filestore"
)

// DirectNativeJAR is one JAR supplied directly by Jenkins or an operator.
// FileName is treated as opaque text; no version is parsed from it.
type DirectNativeJAR struct {
	Path     string
	SHA256   string
	FileName string
	Identity filestore.Identity
}

// OpenDirectNativeJAR validates the direct file, verifies every ZIP entry and
// records the immutable identity used by the transaction.
func OpenDirectNativeJAR(jarPath string) (DirectNativeJAR, error) {
	if err := validateAbsoluteRegularFile(jarPath, "native backend JAR"); err != nil {
		return DirectNativeJAR{}, err
	}
	fileName := filepath.Base(jarPath)
	if filepath.Ext(fileName) != ".jar" {
		return DirectNativeJAR{}, fmt.Errorf("native backend JAR file name must end with .jar: %s", fileName)
	}
	if err := verifyJARArchive(jarPath); err != nil {
		return DirectNativeJAR{}, err
	}
	identity, err := identifyFile(jarPath)
	if err != nil {
		return DirectNativeJAR{}, err
	}
	return DirectNativeJAR{
		Path:     jarPath,
		SHA256:   identity.SHA256,
		FileName: fileName,
		Identity: identity,
	}, nil
}

// CopyArtifact copies the exact JAR into transaction storage and rejects a
// source file that changes after OpenDirectNativeJAR returns.
func (j DirectNativeJAR) CopyArtifact(destination string) error {
	if !filepath.IsAbs(destination) || filepath.Clean(destination) != destination {
		return errors.New("native backend JAR 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 JAR destination directory: %w", err)
	}
	parentInfo, err := os.Lstat(parent)
	if err != nil {
		return fmt.Errorf("inspect native backend JAR destination directory: %w", err)
	}
	if !parentInfo.IsDir() || parentInfo.Mode()&os.ModeSymlink != 0 {
		return fmt.Errorf("native backend JAR destination parent is not a direct directory: %s", parent)
	}

	source, err := os.Open(j.Path)
	if err != nil {
		return fmt.Errorf("open native backend JAR: %w", err)
	}
	temporary, err := os.CreateTemp(parent, ".backend-jar-*")
	if err != nil {
		_ = source.Close()
		return fmt.Errorf("create native backend JAR transaction 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 JAR transaction file 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("copy native backend JAR: %w", err)
	}
	actualDigest := hex.EncodeToString(digest.Sum(nil))
	if written != j.Identity.Size || !strings.EqualFold(actualDigest, j.Identity.SHA256) {
		_ = temporary.Close()
		return errors.New("native backend JAR changed while entering the transaction")
	}
	if err := temporary.Sync(); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("flush native backend JAR transaction file: %w", err)
	}
	if err := temporary.Close(); err != nil {
		return fmt.Errorf("close native backend JAR transaction file: %w", err)
	}
	if err := verifyJARArchive(temporaryPath); err != nil {
		return fmt.Errorf("verify copied native backend JAR: %w", err)
	}
	if err := os.Rename(temporaryPath, destination); err != nil {
		return fmt.Errorf("publish native backend JAR transaction file: %w", err)
	}
	return syncDirectory(parent)
}

func verifyJARArchive(jarPath string) error {
	archive, err := zip.OpenReader(jarPath)
	if err != nil {
		return fmt.Errorf("open native backend JAR %s: %w", jarPath, err)
	}
	defer archive.Close()
	if len(archive.File) == 0 {
		return errors.New("native backend JAR contains no ZIP entries")
	}
	for _, entry := range archive.File {
		if entry.FileInfo().IsDir() {
			continue
		}
		reader, err := entry.Open()
		if err != nil {
			return fmt.Errorf("open native backend JAR entry %s: %w", entry.Name, err)
		}
		_, readErr := io.Copy(io.Discard, reader)
		closeErr := reader.Close()
		if err := errors.Join(readErr, closeErr); err != nil {
			return fmt.Errorf("verify native backend JAR entry %s: %w", entry.Name, err)
		}
	}
	return nil
}

func identifyFile(filePath string) (filestore.Identity, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return filestore.Identity{}, fmt.Errorf("open native backend JAR for identity: %w", err)
	}
	digest := sha256.New()
	size, copyErr := io.Copy(digest, file)
	closeErr := file.Close()
	if err := errors.Join(copyErr, closeErr); err != nil {
		return filestore.Identity{}, fmt.Errorf("identify native backend JAR: %w", err)
	}
	return filestore.Identity{Size: size, SHA256: hex.EncodeToString(digest.Sum(nil))}, nil
}