package main

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

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

const appName = "modman"

var errGameNotFound = errors.New("game not found")

var gamesIniPath = filepath.Join(configDirPath(), "games.ini")

func CleanGameMods(gameName string) error {
	var deployDirPath, pathError = gameDataPath(gameName)

	if pathError != nil {
		return pathError
	}

	// Loop over overwrite dir and move files back.
	var cacheDirPath = filepath.Join(cacheDirPath(), gameName)
	var stageDirPath = filepath.Join(cacheDirPath, "staged")

	if walkError := filepath.WalkDir(stageDirPath, func(
		path string, dirEntry fs.DirEntry, err error) error {

		if err != nil {
			return err
		}

		if dirEntry.IsDir() {
			return nil
		}

		var relativePath, relativeError = filepath.Rel(stageDirPath, path)

		if relativeError != nil {
			return relativeError
		}

		if removeError := os.Remove(filepath.Join(
			deployDirPath, relativePath)); removeError != nil {

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

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

	if removeError := os.RemoveAll(stageDirPath); removeError != nil {
		return removeError
	}

	var overwriteDirPath = filepath.Join(cacheDirPath, "overwritten")

	if walkError := filepath.WalkDir(overwriteDirPath, func(
		path string, dirEntry fs.DirEntry, err error) error {

		if err != nil {
			return err
		}

		if dirEntry.IsDir() {
			return nil
		}

		var relativePath, relativeError = filepath.Rel(overwriteDirPath, path)

		if relativeError != nil {
			return relativeError
		}

		if renameError := os.Rename(path, filepath.Join(
			deployDirPath, relativePath)); renameError != nil {

			return renameError
		}

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

	if removeError := os.RemoveAll(overwriteDirPath); removeError != nil {
		return removeError
	}

	return nil
}

func CreateGame(gameName string, gameDataPath string) error {
	var gameDataPaths = make(map[string]string)

	if fileInfo, statError := os.Stat(gameDataPath); statError == nil {
		if !(fileInfo.IsDir()) {
			return fmt.Errorf("game data path must be a valid directory")
		}
	} else {
		return statError
	}

	if iniFile, openError := os.Open(gamesIniPath); openError == nil {
		defer func() {
			if closeError := iniFile.Close(); closeError != nil {
				panic(closeError)
			}
		}()

		var parser = ini.NewParser(iniFile)

		for entry := parser.Parse(); !(parser.IsEnd()); entry = parser.Parse() {
			var section = parser.Section()

			if section == gameName {
				return fmt.Errorf("`%s` is already used by a game", section)
			}

			if entry.Key == "path" {
				gameDataPaths[section] = entry.Value
			}
		}

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

	gameDataPaths[gameName] = gameDataPath

	return saveGames(gameDataPaths)
}

func DeployGameMods(gameName string, modArchivePaths []string) error {
	var deployDirPath, pathError = gameDataPath(gameName)

	if pathError != nil {
		return pathError
	}

	var overwrittenFilePaths = make(map[string]bool)
	var cacheDirPath = filepath.Join(cacheDirPath(), gameName)
	var overwriteDirPath = filepath.Join(cacheDirPath, "overwritten")

	if walkError := filepath.WalkDir(overwriteDirPath, func(
		path string, dirEntry fs.DirEntry, err error) error {

		if err != nil {
			return err
		}

		if !(dirEntry.IsDir()) {
			var relativePath, relativeError = filepath.Rel(overwriteDirPath, path)

			if relativeError != nil {
				return relativeError
			}

			overwrittenFilePaths[relativePath] = true
		}

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

	var stageDirPath = filepath.Join(cacheDirPath, "staged")

	for _, archivePath := range modArchivePaths {
		var archiveExtension = filepath.Ext(archivePath)

		if len(archiveExtension) == 0 {
			return fmt.Errorf("cannot infer archive format: `%s`", archivePath)
		}

		switch archiveExtension[1:] {
		case "zip":
			var zipReadCloser, openError = zip.OpenReader(archivePath)

			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 stagePath = filepath.Join(stageDirPath, zipFile.Name)

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

					return dirError
				}

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

				var entryReadCloser, openError = zipFile.Open()

				if openError != nil {
					return openError
				}

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

				if stagingFile, createError := os.Create(stagePath); createError == nil {
					if _, copyError := io.Copy(stagingFile, entryReadCloser); copyError != nil {
						stagingFile.Sync()
						stagingFile.Close()

						return copyError
					}

					if syncError := stagingFile.Sync(); syncError != nil {
						stagingFile.Close()

						return syncError
					}

					if closeError := stagingFile.Close(); closeError != nil {
						return closeError
					}
				} else {
					return createError
				}
			}

		default:
			return fmt.Errorf("unrecognized archive format: `%s`", archivePath)
		}
	}

	if walkError := filepath.WalkDir(stageDirPath, func(
		path string, dirEntry fs.DirEntry, err error) error {

		if dirEntry.IsDir() {
			return nil
		}

		var relativePath, relativeError = filepath.Rel(stageDirPath, path)

		if relativeError != nil {
			return relativeError
		}

		var deployFilePath = filepath.Join(deployDirPath, relativePath)

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

		if isOverwrittenFilePath := overwrittenFilePaths[relativePath]; !(isOverwrittenFilePath) {
			var ovewriteFilePath = filepath.Join(overwriteDirPath, relativePath)

			if _, statError := os.Stat(ovewriteFilePath); statError == nil {
				if dirError := os.MkdirAll(
					filepath.Dir(ovewriteFilePath), os.ModePerm); dirError != nil {

					return dirError
				}

				if renameError := os.Rename(deployFilePath, ovewriteFilePath); renameError != nil {
					return renameError
				}
			} else if !(os.IsNotExist(statError)) {
				return statError
			}
		}

		if linkError := os.Link(path, deployFilePath); linkError != nil {
			if !(os.IsNotExist(linkError)) {
				return linkError
			}
		}

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

	return nil
}

func RemoveGame(gameName string) error {
	if cleanError := CleanGameMods(gameName); cleanError != nil {
		return cleanError
	}

	var gameDataPaths = make(map[string]string)

	if iniFile, openError := os.Open(gamesIniPath); openError == nil {
		if (openError != nil) && !(os.IsNotExist(openError)) {
			return openError
		}

		defer func() {
			if closeError := iniFile.Close(); closeError != nil {
				panic(closeError)
			}
		}()

		var parser = ini.NewParser(iniFile)

		for entry := parser.Parse(); !(parser.IsEnd()); entry = parser.Parse() {
			var section = parser.Section()

			if (section != gameName) && (entry.Key == "path") {
				gameDataPaths[section] = entry.Value
			}
		}

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

	return saveGames(gameDataPaths)
}

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

func configDirPath() 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, appName, fallbackSubdir)
	}

	return filepath.Join(path, appName)
}

func gameDataPath(gameName string) (string, error) {
	var gamesFile, openError = os.Open(gamesIniPath)

	if (openError != nil) && !(os.IsNotExist(openError)) {
		return "", openError
	}

	defer func() {
		if closeError := gamesFile.Close(); closeError != nil {
			panic(closeError)
		}
	}()

	var parser = ini.NewParser(gamesFile)

	for entry := parser.Parse(); !(parser.IsEnd()); entry = parser.Parse() {
		if (parser.Section() == gameName) && (entry.Key == "path") {
			return entry.Value, nil
		}
	}

	if parseError := parser.Err(); parseError != nil {
		return "", parseError
	}

	return "", errGameNotFound
}

func saveGames(gameDataPaths map[string]string) error {
	if iniFile, createError := os.Create(gamesIniPath); createError == nil {
		var iniWriter = bufio.NewWriter(iniFile)
		var iniBuilder = ini.NewBuilder(iniWriter)

		for name, dataPath := range gameDataPaths {
			iniBuilder.Section(name)
			iniBuilder.KeyValue("path", dataPath)
		}

		if flushError := iniWriter.Flush(); flushError != nil {
			iniFile.Close()

			return flushError
		}

		if syncError := iniFile.Sync(); syncError != nil {
			iniFile.Close()

			return syncError
		}

		if closeError := iniFile.Close(); closeError != nil {
			return closeError
		}
	} else {
		return createError
	}

	return nil
}