package languageService

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

const (
	betaPersistentContainer      = "79568e2a754e3eab8afe4b5bf96c27ab.bytes"
	betaPersistentContainerCopy  = "e303f4dc6c21f043021bb5b3b875b6c3.bytes"
	betaStreamingContainer       = "4703a1942cfa452f451ba0a2f826b764.bytes"
	betaStreamingContainerCopy   = "44b594f1fab938d6ed95d6a1154e03c0.bytes"
	betaPersistentDesignV        = "878d1fefee5f49221b003050cb4a2d2f"
	betaPersistentDesignVCopy    = "74b62fb914b36cccaa10d93ace9af2c0"
	betaStreamingDesignV         = "b5eefe4a429b498a8f5003f28a4b21c6"
	betaStreamingDesignVCopy     = "3ada95b84a1e0d96404ea5e7414ab353"
	betaPersistentContainerLimit = 26240102
	betaStreamingContainerLimit  = 73631
)

func (l *LanguageService) InstallThaiPatch(gameRoot, packageRoot string) (bool, string) {
	gameRoot, err := filepath.Abs(filepath.Clean(gameRoot))
	if err != nil {
		return false, fmt.Errorf("resolve game folder: %w", err).Error()
	}
	packageRoot, err = filepath.Abs(filepath.Clean(packageRoot))
	if err != nil {
		return false, fmt.Errorf("resolve patch package folder: %w", err).Error()
	}

	if _, err := os.Stat(filepath.Join(gameRoot, "StarRail.exe")); err != nil {
		return false, "selected folder does not contain StarRail.exe"
	}
	streamingAssets := filepath.Join(gameRoot, "StarRail_Data", "StreamingAssets")
	binaryVersion, err := os.ReadFile(filepath.Join(streamingAssets, "BinaryVersion.bytes"))
	if err != nil {
		return false, fmt.Errorf("read game version: %w", err).Error()
	}
	if !bytes.Contains(binaryVersion, []byte("BETAWin")) {
		return false, "this Thai patch package only supports Honkai: Star Rail Beta"
	}

	assets := filepath.Join(packageRoot, "assets")
	readAsset := func(relative string) ([]byte, error) {
		data, err := os.ReadFile(filepath.Join(assets, filepath.FromSlash(relative)))
		if err != nil {
			return nil, fmt.Errorf("read patch asset %s: %w", relative, err)
		}
		return data, nil
	}
	requireAsset := func(relative string) ([]byte, error) {
		data, err := readAsset(relative)
		if err != nil {
			return nil, err
		}
		if len(data) == 0 {
			return nil, fmt.Errorf("patch asset %s is empty", relative)
		}
		return data, nil
	}

	textMap, err := requireAsset("1_TextMap_th/1fb7b1dce8d66efe8e111bb07a3eef44.bytes")
	if err != nil {
		return false, err.Error()
	}
	persistentUI, err := requireAsset("2_UI_Persistent/fd5227547d65b8bb1238feb3e5820fa3.bytes")
	if err != nil {
		return false, err.Error()
	}
	streamingUI, err := requireAsset("3_UI_StreamingAssets/2ea44f7fabf315d35de1d7f3b4c07d89.bytes")
	if err != nil {
		return false, err.Error()
	}
	localePack, err := requireAsset("4_Locale_Pak/th.pak")
	if err != nil {
		return false, err.Error()
	}
	allowedLanguages, err := requireAsset("5_AllowedLanguage/allowed_language_140bytes.bin")
	if err != nil {
		return false, err.Error()
	}
	persistentDesign, err := requireAsset("prebuilt_designv/DesignV_" + betaPersistentDesignV + ".bytes")
	if err != nil {
		return false, err.Error()
	}
	streamingDesign, err := requireAsset("prebuilt_designv/DesignV_" + betaStreamingDesignV + ".bytes")
	if err != nil {
		return false, err.Error()
	}

	dataRoot := filepath.Join(gameRoot, "StarRail_Data")
	persistentDesignDir := filepath.Join(dataRoot, "Persistent", "DesignData", "Windows")
	streamingDesignDir := filepath.Join(dataRoot, "StreamingAssets", "DesignData", "Windows")
	for _, dir := range []string{
		filepath.Join(dataRoot, "Persistent", "Asb", "Windows"),
		filepath.Join(dataRoot, "Persistent", "Audio", "AudioPackage", "Windows"),
		persistentDesignDir,
		filepath.Join(dataRoot, "StreamingAssets", "Asb", "Windows"),
		streamingDesignDir,
	} {
		if err := os.MkdirAll(dir, 0755); err != nil {
			return false, fmt.Errorf("create patch folder %s: %w", dir, err).Error()
		}
	}

	type fileWrite struct {
		path string
		data []byte
	}
	writes := []fileWrite{
		{filepath.Join(dataRoot, "Persistent", "Asb", "Windows", "1fb7b1dce8d66efe8e111bb07a3eef44.bytes"), textMap},
		{filepath.Join(dataRoot, "Persistent", "Asb", "Windows", "fd5227547d65b8bb1238feb3e5820fa3.bytes"), persistentUI},
		{filepath.Join(dataRoot, "StreamingAssets", "Asb", "Windows", "2ea44f7fabf315d35de1d7f3b4c07d89.bytes"), streamingUI},
		{filepath.Join(dataRoot, "Persistent", "Audio", "AudioPackage", "Windows", "th.pak"), localePack},
		{filepath.Join(persistentDesignDir, "DesignV_"+betaPersistentDesignV+".bytes"), persistentDesign},
		{filepath.Join(persistentDesignDir, "DesignV_"+betaPersistentDesignVCopy+".bytes"), persistentDesign},
		{filepath.Join(streamingDesignDir, "DesignV_"+betaStreamingDesignV+".bytes"), streamingDesign},
		{filepath.Join(streamingDesignDir, "DesignV_"+betaStreamingDesignVCopy+".bytes"), streamingDesign},
	}

	for _, write := range writes {
		if err := os.WriteFile(write.path, write.data, 0644); err != nil {
			return false, fmt.Errorf("save patch file %s: %w", write.path, err).Error()
		}
	}

	if err := patchContainerFile(filepath.Join(persistentDesignDir, betaPersistentContainer), persistentDesign, betaPersistentContainerLimit); err != nil {
		return false, err.Error()
	}
	if err := patchContainerFile(filepath.Join(persistentDesignDir, betaPersistentContainerCopy), persistentDesign, betaPersistentContainerLimit); err != nil {
		return false, err.Error()
	}
	if err := patchContainerFile(filepath.Join(streamingDesignDir, betaStreamingContainer), streamingDesign, betaStreamingContainerLimit); err != nil {
		return false, err.Error()
	}
	if err := patchContainerFile(filepath.Join(streamingDesignDir, betaStreamingContainerCopy), streamingDesign, betaStreamingContainerLimit); err != nil {
		return false, err.Error()
	}

	if err := patchAllowedLanguages(filepath.Join(dataRoot, "Persistent", "AllowedLanguage.bytes"), allowedLanguages); err != nil {
		return false, err.Error()
	}

	return true, ""
}

func patchContainerFile(path string, targetPayload []byte, sizeLimit int64) error {
	data, err := os.ReadFile(path)
	if errors.Is(err, os.ErrNotExist) {
		return nil
	}
	if err != nil {
		return fmt.Errorf("read container %s: %w", path, err)
	}
	if int64(len(data)) > sizeLimit {
		return fmt.Errorf("container file is unexpectedly large: %s", path)
	}

	entries, err := parseDesignVContainer(data)
	if err != nil {
		return fmt.Errorf("parse container %s: %w", path, err)
	}

	for i := range entries {
		entries[i].payload = append([]byte(nil), targetPayload...)
	}

	rebuilt, err := buildDesignVContainer(entries)
	if err != nil {
		return fmt.Errorf("rebuild container %s: %w", path, err)
	}

	if err := os.WriteFile(path, rebuilt, 0644); err != nil {
		return fmt.Errorf("save container %s: %w", path, err)
	}
	return nil
}

type containerEntry struct {
	hash    string
	payload []byte
}

func parseDesignVContainer(data []byte) ([]containerEntry, error) {
	if len(data) < 4 {
		return nil, fmt.Errorf("container is too short")
	}
	reader := bytes.NewReader(data)
	var count uint32
	if err := binary.Read(reader, binary.LittleEndian, &count); err != nil {
		return nil, err
	}
	entries := make([]containerEntry, 0, count)
	for i := uint32(0); i < count; i++ {
		var hashBytes [16]byte
		if _, err := io.ReadFull(reader, hashBytes[:]); err != nil {
			return nil, err
		}
		var length uint32
		if err := binary.Read(reader, binary.LittleEndian, &length); err != nil {
			return nil, err
		}
		payload := make([]byte, length)
		if _, err := io.ReadFull(reader, payload); err != nil {
			return nil, err
		}
		entries = append(entries, containerEntry{
			hash:    hex.EncodeToString(hashBytes[:]),
			payload: payload,
		})
	}
	return entries, nil
}

func buildDesignVContainer(entries []containerEntry) ([]byte, error) {
	sort.Slice(entries, func(i, j int) bool {
		return strings.ToLower(entries[i].hash) < strings.ToLower(entries[j].hash)
	})
	var buffer bytes.Buffer
	if err := binary.Write(&buffer, binary.LittleEndian, uint32(len(entries))); err != nil {
		return nil, err
	}
	for _, entry := range entries {
		rawHash, err := hex.DecodeString(entry.hash)
		if err != nil || len(rawHash) != 16 {
			return nil, fmt.Errorf("invalid hash in container entry: %s", entry.hash)
		}
		if _, err := buffer.Write(rawHash); err != nil {
			return nil, err
		}
		if err := binary.Write(&buffer, binary.LittleEndian, uint32(len(entry.payload))); err != nil {
			return nil, err
		}
		if _, err := buffer.Write(entry.payload); err != nil {
			return nil, err
		}
	}
	return buffer.Bytes(), nil
}

func patchAllowedLanguages(path string, payload []byte) error {
	return os.WriteFile(path, payload, 0644)
}