package main

import (
	"archive/zip"
	"bufio"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"sauce.pizzawednes.day/kayomn/ini-gusher"
)

func (game *Game) Clean() error {
	// Clean up currently deployed files first.
	for _, filePath := range game.DeployedFilePaths {
		if removeError := os.Remove(filepath.Join(
			game.Path, filePath)); (removeError != nil) && (!(os.IsNotExist(removeError))) {

			return removeError
		}
	}

	game.DeployedFilePaths = game.DeployedFilePaths[:0]

	var overwriteDirPath = filepath.Join(cachePath(), game.Name, "overwritten")

	// Then restore all files overwritten by previously deployment.
	for _, filePath := range game.OverwrittenFilePaths {
		if renameError := os.Rename(filepath.Join(overwriteDirPath, filePath),
			filepath.Join(game.Path, filePath)); renameError != nil {

			return renameError
		}
	}

	game.OverwrittenFilePaths = game.OverwrittenFilePaths[:0]

	return game.saveDeployment()
}

func (game *Game) Deploy(names []string) error {
	if cleanError := game.Clean(); cleanError != nil {
		return cleanError
	}

	for _, name := range names {
		var mod, exists = game.Mods[name]

		if !(exists) {
			return fmt.Errorf("mod does not exist: %s", name)
		}

		var installPath = fmt.Sprintf("%s.%s",
			filepath.Join(configPath(), game.Name, name), mod.Format)

		switch mod.Format {
		case "zip":
			var zipReadCloser, openError = zip.OpenReader(installPath)

			if openError != nil {
				return openError
			}

			defer func() {
				if closeError := zipReadCloser.Close(); closeError != nil {
					// Zip read closer will not have any pending I/O operations nor is it possible
					// to have already been closed.
					panic(closeError)
				}
			}()

			for _, zipFile := range zipReadCloser.File {
				var deployPath = filepath.Join(game.Path, zipFile.Name)
				var fileMode = zipFile.Mode()

				if dirError := os.MkdirAll(filepath.Dir(deployPath), fileMode); dirError != nil {
					return dirError
				}

				if zipFile.FileInfo().IsDir() {
					// All work is done for creating a directory, rest is just for files.
					continue
				}

				// Backup up any pre-existing file before it is overwritten by Zip entry
				// extraction.
				if _, statError := os.Stat(deployPath); statError == nil {
					var backupPath = filepath.Join(
						cachePath(), game.Name, "overwritten", zipFile.Name)

					if dirError := os.MkdirAll(filepath.Dir(backupPath), os.ModePerm); dirError != nil {
						return dirError
					}

					if renameError := os.Rename(deployPath, backupPath); renameError != nil {
						return renameError
					}

					game.OverwrittenFilePaths = append(game.OverwrittenFilePaths, zipFile.Name)
				} else if !(os.IsNotExist(statError)) {
					return statError
				}

				if file, createError := os.Create(deployPath); createError == nil {
					var zipFile, ioError = zipFile.Open()

					if ioError == nil {
						_, ioError = io.Copy(file, zipFile)
					}

					if syncError := file.Sync(); (syncError != nil) && (ioError == nil) {
						ioError = syncError
					}

					if closeError := file.Close(); (closeError != nil) && (ioError == nil) {
						ioError = closeError
					}

					if closeError := zipFile.Close(); closeError != nil {
						ioError = closeError
					}

					if ioError != nil {
						return ioError
					}
				} else {
					if closeError := zipReadCloser.Close(); closeError != nil {
						return closeError
					}

					return createError
				}

				game.DeployedFilePaths = append(game.DeployedFilePaths, zipFile.Name)
			}

		default:
			return fmt.Errorf("unsupported mod format: %s", mod.Format)
		}
	}

	return game.saveDeployment()
}

type Game struct {
	Name                 string
	DeployedFilePaths    []string
	OverwrittenFilePaths []string
	Mods                 map[string]Mod
	Path                 string
}

func (game *Game) InstallMods(archivePaths []string) error {
	var installDirPath = filepath.Join(configPath(), game.Name)

	for _, archivePath := range archivePaths {
		var archiveName = filepath.Base(archivePath)
		var archiveExtension = filepath.Ext(archiveName)

		if len(archiveExtension) == 0 {
			return fmt.Errorf("unknown archive format: %s", archiveExtension)
		}

		var name = strings.TrimSuffix(archiveName, archiveExtension)

		if _, exists := game.Mods[name]; exists {
			return fmt.Errorf("mod with name already exists: `%s`", name)
		}

		// Copy archive into installation directory.
		if archiveFile, openError := os.Open(archivePath); openError == nil {
			defer func() {
				if closeError := archiveFile.Close(); closeError != nil {
					// Archive file will not have any pending I/O operations nor is it possible to have
					// already been closed.
					panic(closeError)
				}
			}()

			var archiveFileInfo, statError = archiveFile.Stat()

			if statError != nil {
				return statError
			}

			if dirError := os.MkdirAll(installDirPath, archiveFileInfo.Mode()); dirError != nil {
				return dirError
			}

			if installFile, createError := os.Create(filepath.Join(installDirPath, archiveName)); createError == nil {
				var _, copyError = io.Copy(installFile, archiveFile)
				var syncError = installFile.Sync()
				var closeError = installFile.Close()

				if (copyError != nil) || (syncError != nil) {
					return fmt.Errorf("failed to install mod")
				}

				if closeError != nil {
					return closeError
				}
			} else {
				return createError
			}
		} else {
			return openError
		}

		game.Mods[name] = Mod{
			Format:  archiveExtension[1:],
			Source:  archivePath,
			Version: "",
		}
	}

	return game.saveMods()
}

func (game *Game) Load() error {
	// Read deployed files from disk.
	var deployedListPath = filepath.Join(cachePath(), game.Name, "deployed.txt")

	if file, openError := os.Open(deployedListPath); openError == nil {
		for scanner := bufio.NewScanner(file); scanner.Scan(); {
			game.DeployedFilePaths = append(game.DeployedFilePaths, scanner.Text())
		}

		if closeError := file.Close(); closeError != nil {
			return closeError
		}
	} else if !(os.IsNotExist(openError)) {
		return openError
	}

	// Read overwritten game files from disk.
	var overwrittenFilesDirPath = filepath.Join(cachePath(), game.Name, "overwritten")

	if _, statError := os.Stat(overwrittenFilesDirPath); statError == nil {
		if walkError := filepath.WalkDir(overwrittenFilesDirPath, func(
			path string, dirEntry fs.DirEntry, walkError error) error {

			if walkError != nil {
				return walkError
			}

			if !(dirEntry.IsDir()) {
				game.OverwrittenFilePaths = append(game.OverwrittenFilePaths, path)
			}

			return nil
		}); walkError != nil {
			return walkError
		}
	} else if !(os.IsNotExist(statError)) {
		return statError
	}

	// Read mod info from disk.
	if file, openError := os.Open(filepath.Join(configPath(), game.Name, "mods.ini")); openError == nil {
		defer func() {
			if closeError := file.Close(); closeError != nil {
				// File will not have any pending I/O operations nor is it possible to have already
				// been closed.
				panic(closeError)
			}
		}()

		var parser = ini.NewParser(file)

		for entry := parser.Parse(); !(parser.IsEnd()); entry = parser.Parse() {
			var mod = game.Mods[entry.Section]

			switch entry.Key {
			case "format":
				mod.Format = entry.Value

			case "source":
				mod.Source = entry.Value

			case "version":
				mod.Version = entry.Value
			}

			game.Mods[entry.Section] = mod
		}

		if parserError := parser.Err(); parserError != nil {
			return parserError
		}
	} else if !(os.IsNotExist(openError)) {
		return openError
	}

	return nil
}

type Mod struct {
	Format  string
	Source  string
	Version string
}

func LoadGame(name string) (Game, error) {
	var configPath, configPathError = os.UserConfigDir()

	if configPathError != nil {
		return Game{}, configPathError
	}

	var gamesFile, gamesOpenError = os.Open(filepath.Join(configPath, "modman", "games.ini"))

	if gamesOpenError != nil {
		if os.IsNotExist(gamesOpenError) {
			return Game{}, fmt.Errorf("no games registered")
		}

		return Game{}, gamesOpenError
	}

	var gamesParser = ini.NewParser(gamesFile)

	for entry := gamesParser.Parse(); !(gamesParser.IsEnd()); entry = gamesParser.Parse() {
		if (entry.Key == "path") && (entry.Section == name) {
			var game = Game{
				Name:                 name,
				OverwrittenFilePaths: make([]string, 0, 512),
				DeployedFilePaths:    make([]string, 0, 512),
				Mods:                 make(map[string]Mod),
				Path:                 entry.Value,
			}

			if loadError := game.Load(); loadError != nil {
				return Game{}, loadError
			}

			return game, nil
		}
	}

	return Game{}, fmt.Errorf("game not registered: %s", name)
}

func (game *Game) RemoveMod(name string) error {
	if _, exists := game.Mods[name]; !(exists) {
		return fmt.Errorf("unknown mod: `%s`", name)
	}

	if removeError := os.RemoveAll(filepath.Join(
		configPath(), game.Name, name)); removeError != nil {

		return removeError
	}

	delete(game.Mods, name)

	return game.saveMods()
}

func RegisterGame(name string, dataPath string) error {
	var gamesPath = filepath.Join(configPath(), "games.ini")
	var gameNamePaths = make(map[string]string)

	if file, openError := os.Open(gamesPath); openError == nil {
		defer func() {
			if closeError := file.Close(); closeError != nil {
				// No way for this to fail.
				panic(closeError)
			}
		}()

		var parser = ini.NewParser(file)

		for entry := parser.Parse(); !(parser.IsEnd()); entry = parser.Parse() {
			if entry.Key == "path" {
				gameNamePaths[entry.Section] = entry.Value
			}
		}

		if parserError := parser.Err(); parserError != nil {
			return parserError
		}
	} else if !(os.IsNotExist(openError)) {
		return openError
	}

	if file, updateError := os.Create(gamesPath); updateError == nil {
		var writer = bufio.NewWriter(file)
		var builder = ini.NewBuilder(writer)

		for name, path := range gameNamePaths {
			if buildError := builder.Section(name); buildError != nil {
				updateError = buildError

				break
			}

			if buildError := builder.KeyValue("path", path); buildError != nil {
				updateError = buildError

				break
			}
		}

		if writeError := writer.Flush(); (writeError != nil) && (updateError == nil) {
			updateError = writeError
		}

		if syncError := file.Sync(); (syncError != nil) && (updateError == nil) {
			updateError = syncError
		}

		if closeError := file.Close(); (closeError != nil) && (updateError == nil) {
			updateError = closeError
		}

		if updateError != nil {
			return updateError
		}
	} else {
		return updateError
	}

	return nil
}

func (game *Game) RenameMod(modName string, newName string) error {
	var mod, exists = game.Mods[modName]

	if !(exists) {
		return fmt.Errorf("no mod with that name exists")
	}

	if _, nameTaken := game.Mods[newName]; nameTaken {
		return fmt.Errorf("a mod with the new name already exists")
	}

	var modsDirPath = filepath.Join(configPath(), game.Name)

	if renameError := os.Rename(filepath.Join(modsDirPath, modName),
		filepath.Join(modsDirPath, newName)); renameError != nil {

		return renameError
	}

	game.Mods[newName] = mod

	delete(game.Mods, modName)

	return game.saveMods()
}

func cachePath() string {
	return fallbackPath(os.UserCacheDir, "cache")
}

func configPath() string {
	return fallbackPath(os.UserConfigDir, "config")
}

func fallbackPath(getFalliblePath func() (string, error), fallbackSubdir string) string {
	var path, pathError = getFalliblePath()

	if pathError != nil {
		// Fallback to homedir.
		path, pathError = os.UserHomeDir()

		if pathError != nil {
			// User home dir should exist / be accessible.
			panic(pathError)
		}

		return filepath.Join(path, "modman", fallbackSubdir)
	}

	return filepath.Join(path, "modman")
}

func (game *Game) saveDeployment() error {
	var listPath = filepath.Join(cachePath(), game.Name, "deployed.txt")

	if len(game.DeployedFilePaths) == 0 {
		var truncateError = os.Truncate(listPath, 0)

		if !(os.IsNotExist(truncateError)) {
			return truncateError
		}
	}

	if dirError := os.MkdirAll(filepath.Dir(listPath), os.ModePerm); dirError != nil {
		return dirError
	}

	if file, updateError := os.Create(listPath); updateError == nil {
		var writer = bufio.NewWriter(file)

		for _, filePath := range game.DeployedFilePaths {
			if _, printError := fmt.Fprintln(writer, filePath); printError != nil {
				updateError = printError

				break
			}
		}

		if flushError := writer.Flush(); flushError != nil && updateError == nil {
			updateError = flushError
		}

		if syncError := file.Sync(); syncError != nil && updateError == nil {
			updateError = syncError
		}

		if closeError := file.Close(); closeError != nil && updateError == nil {
			updateError = closeError
		}

		if updateError != nil {
			return updateError
		}
	} else {
		return updateError
	}

	return nil
}

func (game *Game) saveMods() error {
	var file, updateError = os.Create(filepath.Join(configPath(), game.Name, "mods.ini"))

	if updateError != nil {
		return updateError
	}

	var writer = bufio.NewWriter(file)
	var builder = ini.NewBuilder(writer)

	for name, mod := range game.Mods {
		if buildError := builder.Section(name); buildError != nil {
			updateError = buildError

			break
		}

		if buildError := builder.KeyValue("format", mod.Format); buildError != nil {
			updateError = buildError

			break
		}

		if buildError := builder.KeyValue("source", mod.Source); buildError != nil {
			updateError = buildError

			break
		}

		if buildError := builder.KeyValue("version", mod.Version); buildError != nil {
			updateError = buildError

			break
		}
	}

	if writeError := writer.Flush(); (writeError != nil) && (updateError == nil) {
		updateError = writeError
	}

	if syncError := file.Sync(); (syncError != nil) && (updateError == nil) {
		updateError = syncError
	}

	if closeError := file.Close(); (closeError != nil) && (updateError == nil) {
		updateError = closeError
	}

	return updateError
}