package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"time"

	"github.com/distatus/battery"
	process "github.com/shirou/gopsutil/v3/process"
)

const (
	unknown         = "unknown"
	windowsPlatform = "windows"
	darwinPlatform  = "darwin"
	linuxPlatform   = "linux"
)

type commandError struct {
	err      string
	exitCode int
}

func (e *commandError) Error() string {
	return e.err
}

type noBatteryError struct{}

func (m *noBatteryError) Error() string {
	return "no battery"
}

type fileInfo struct {
	parentFolder string
	path         string
	isDir        bool
}

type cache interface {
	init(home string)
	close()
	get(key string) (string, bool)
	// ttl in minutes
	set(key, value string, ttl int)
}

type environmentInfo interface {
	getenv(key string) string
	getcwd() string
	homeDir() string
	hasFiles(pattern string) bool
	hasFilesInDir(dir, pattern string) bool
	hasFolder(folder string) bool
	getFileContent(file string) string
	getFoldersList(path string) []string
	getPathSeperator() string
	getCurrentUser() string
	isRunningAsRoot() bool
	getHostName() (string, error)
	getRuntimeGOOS() string
	getPlatform() string
	hasCommand(command string) bool
	runCommand(command string, args ...string) (string, error)
	runShellCommand(shell, command string) string
	lastErrorCode() int
	executionTime() float64
	getArgs() *args
	getBatteryInfo() ([]*battery.Battery, error)
	getShellName() string
	getWindowTitle(imageName, windowTitleRegex string) (string, error)
	doGet(url string, timeout int) ([]byte, error)
	hasParentFilePath(path string) (fileInfo *fileInfo, err error)
	isWsl() bool
	stackCount() int
	getTerminalWidth() (int, error)
	getCachePath() string
	cache() cache
	close()
	logs() string
}

type commandCache struct {
	commands *concurrentMap
}

func (c *commandCache) set(command, path string) {
	c.commands.set(command, path)
}

func (c *commandCache) get(command string) (string, bool) {
	cmd, found := c.commands.get(command)
	if !found {
		return "", false
	}
	command, ok := cmd.(string)
	return command, ok
}

type logType string

const (
	Error logType = "error"
	Debug logType = "debug"
)

type environment struct {
	args       *args
	cwd        string
	cmdCache   *commandCache
	fileCache  *fileCache
	logBuilder strings.Builder
	debug      bool
}

func (env *environment) init(args *args) {
	env.args = args
	env.cmdCache = &commandCache{
		commands: newConcurrentMap(),
	}
	if env.args != nil && *env.args.Debug {
		env.debug = true
		log.SetOutput(&env.logBuilder)
	}
	env.fileCache = &fileCache{}
	env.fileCache.init(env.getCachePath())
}

func (env *environment) trace(start time.Time, function string, args ...string) {
	if !env.debug {
		return
	}
	elapsed := time.Since(start)
	trace := fmt.Sprintf("%s duration: %s, args: %s", function, elapsed, strings.Trim(fmt.Sprint(args), "[]"))
	log.Println(trace)
}

func (env *environment) log(lt logType, function, message string) {
	if !env.debug {
		return
	}
	trace := fmt.Sprintf("%s: %s\n%s", lt, function, message)
	log.Println(trace)
}

func (env *environment) getenv(key string) string {
	defer env.trace(time.Now(), "getenv", key)
	val := os.Getenv(key)
	env.log(Debug, "getenv", val)
	return val
}

func (env *environment) getcwd() string {
	defer env.trace(time.Now(), "getcwd")
	if env.cwd != "" {
		return env.cwd
	}
	correctPath := func(pwd string) string {
		// on Windows, and being case sensitive and not consistent and all, this gives silly issues
		driveLetter := getCompiledRegex(`^[a-z]:`)
		return driveLetter.ReplaceAllStringFunc(pwd, strings.ToUpper)
	}
	if env.args != nil && *env.args.PWD != "" {
		env.cwd = correctPath(*env.args.PWD)
		return env.cwd
	}
	dir, err := os.Getwd()
	if err != nil {
		env.log(Error, "getcwd", err.Error())
		return ""
	}
	env.cwd = correctPath(dir)
	return env.cwd
}

func (env *environment) hasFiles(pattern string) bool {
	defer env.trace(time.Now(), "hasFiles", pattern)
	cwd := env.getcwd()
	pattern = cwd + env.getPathSeperator() + pattern
	matches, err := filepath.Glob(pattern)
	if err != nil {
		env.log(Error, "hasFiles", err.Error())
		return false
	}
	return len(matches) > 0
}

func (env *environment) hasFilesInDir(dir, pattern string) bool {
	defer env.trace(time.Now(), "hasFilesInDir", pattern)
	pattern = dir + env.getPathSeperator() + pattern
	matches, err := filepath.Glob(pattern)
	if err != nil {
		env.log(Error, "hasFilesInDir", err.Error())
		return false
	}
	return len(matches) > 0
}

func (env *environment) hasFolder(folder string) bool {
	defer env.trace(time.Now(), "hasFolder", folder)
	_, err := os.Stat(folder)
	return !os.IsNotExist(err)
}

func (env *environment) getFileContent(file string) string {
	defer env.trace(time.Now(), "getFileContent", file)
	content, err := ioutil.ReadFile(file)
	if err != nil {
		env.log(Error, "getFileContent", err.Error())
		return ""
	}
	return string(content)
}

func (env *environment) getFoldersList(path string) []string {
	defer env.trace(time.Now(), "getFoldersList", path)
	content, err := os.ReadDir(path)
	if err != nil {
		env.log(Error, "getFoldersList", err.Error())
		return nil
	}
	var folderNames []string
	for _, s := range content {
		if s.IsDir() {
			folderNames = append(folderNames, s.Name())
		}
	}
	return folderNames
}

func (env *environment) getPathSeperator() string {
	defer env.trace(time.Now(), "getPathSeperator")
	return string(os.PathSeparator)
}

func (env *environment) getCurrentUser() string {
	defer env.trace(time.Now(), "getCurrentUser")
	user := os.Getenv("USER")
	if user == "" {
		user = os.Getenv("USERNAME")
	}
	return user
}

func (env *environment) getHostName() (string, error) {
	defer env.trace(time.Now(), "getHostName")
	hostName, err := os.Hostname()
	if err != nil {
		env.log(Error, "getHostName", err.Error())
		return "", err
	}
	return cleanHostName(hostName), nil
}

func (env *environment) getRuntimeGOOS() string {
	defer env.trace(time.Now(), "getRuntimeGOOS")
	return runtime.GOOS
}

func (env *environment) runCommand(command string, args ...string) (string, error) {
	defer env.trace(time.Now(), "runCommand", append([]string{command}, args...)...)
	if cmd, ok := env.cmdCache.get(command); ok {
		command = cmd
	}
	copyAndCapture := func(r io.Reader) ([]byte, error) {
		var out []byte
		buf := make([]byte, 1024)
		for {
			n, err := r.Read(buf)
			if n > 0 {
				d := buf[:n]
				out = append(out, d...)
			}
			if err == nil {
				continue
			}
			// Read returns io.EOF at the end of file, which is not an error for us
			if err == io.EOF {
				err = nil
			}
			return out, err
		}
	}
	normalizeOutput := func(out []byte) string {
		return strings.TrimSuffix(string(out), "\n")
	}
	cmd := exec.Command(command, args...)
	var stdout, stderr []byte
	var stdoutErr, stderrErr error
	stdoutIn, _ := cmd.StdoutPipe()
	stderrIn, _ := cmd.StderrPipe()
	err := cmd.Start()
	if err != nil {
		errorStr := fmt.Sprintf("cmd.Start() failed with '%s'", err)
		env.log(Error, "runCommand", errorStr)
		return "", errors.New(errorStr)
	}
	// cmd.Wait() should be called only after we finish reading
	// from stdoutIn and stderrIn.
	// wg ensures that we finish
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		stdout, stdoutErr = copyAndCapture(stdoutIn)
		wg.Done()
	}()
	stderr, stderrErr = copyAndCapture(stderrIn)
	wg.Wait()
	err = cmd.Wait()
	if err != nil {
		env.log(Error, "runCommand", err.Error())
		if exitErr, ok := err.(*exec.ExitError); ok {
			return "", &commandError{
				err:      exitErr.Error(),
				exitCode: exitErr.ExitCode(),
			}
		}
	}
	if stdoutErr != nil || stderrErr != nil {
		errString := "failed to capture stdout or stderr"
		env.log(Error, "runCommand", errString)
		return "", errors.New(errString)
	}
	stderrStr := normalizeOutput(stderr)
	if len(stderrStr) > 0 {
		return stderrStr, nil
	}
	output := normalizeOutput(stdout)
	env.log(Debug, "runCommand", output)
	return output, nil
}

func (env *environment) runShellCommand(shell, command string) string {
	defer env.trace(time.Now(), "runShellCommand", shell, command)
	out, _ := env.runCommand(shell, "-c", command)
	return out
}

func (env *environment) hasCommand(command string) bool {
	defer env.trace(time.Now(), "hasCommand", command)
	if _, ok := env.cmdCache.get(command); ok {
		return true
	}
	path, err := exec.LookPath(command)
	if err == nil {
		env.cmdCache.set(command, path)
		return true
	}
	env.log(Error, "hasCommand", err.Error())
	return false
}

func (env *environment) lastErrorCode() int {
	defer env.trace(time.Now(), "lastErrorCode")
	return *env.args.ErrorCode
}

func (env *environment) executionTime() float64 {
	defer env.trace(time.Now(), "executionTime")
	if *env.args.ExecutionTime < 0 {
		return 0
	}
	return *env.args.ExecutionTime
}

func (env *environment) getArgs() *args {
	defer env.trace(time.Now(), "getArgs")
	return env.args
}

func (env *environment) getBatteryInfo() ([]*battery.Battery, error) {
	defer env.trace(time.Now(), "getBatteryInfo")
	batteries, err := battery.GetAll()
	// actual error, return it
	if err != nil && len(batteries) == 0 {
		env.log(Error, "getBatteryInfo", err.Error())
		return nil, err
	}
	// there are no batteries found
	if len(batteries) == 0 {
		return nil, &noBatteryError{}
	}
	// some batteries fail to get retrieved, filter them out if present
	validBatteries := []*battery.Battery{}
	for _, batt := range batteries {
		if batt != nil {
			validBatteries = append(validBatteries, batt)
		}
	}
	unableToRetrieveBatteryInfo := "A device which does not exist was specified."
	// when battery info fails to get retrieved but there is at least one valid battery, return it without error
	if len(validBatteries) > 0 && err != nil && strings.Contains(err.Error(), unableToRetrieveBatteryInfo) {
		return validBatteries, nil
	}
	// another error occurred (possibly unmapped use-case), return it
	if err != nil {
		env.log(Error, "getBatteryInfo", err.Error())
		return nil, err
	}
	// everything is fine
	return validBatteries, nil
}

func (env *environment) getShellName() string {
	defer env.trace(time.Now(), "getShellName")
	if *env.args.Shell != "" {
		return *env.args.Shell
	}
	pid := os.Getppid()
	p, _ := process.NewProcess(int32(pid))
	name, err := p.Name()
	if err != nil {
		env.log(Error, "getShellName", err.Error())
		return unknown
	}
	if name == "cmd.exe" {
		p, _ = p.Parent()
		name, err = p.Name()
	}
	if err != nil {
		env.log(Error, "getShellName", err.Error())
		return unknown
	}
	// Cache the shell value to speed things up.
	*env.args.Shell = strings.Trim(strings.Replace(name, ".exe", "", 1), " ")
	return *env.args.Shell
}

func (env *environment) doGet(url string, timeout int) ([]byte, error) {
	defer env.trace(time.Now(), "doGet", url)
	ctx, cncl := context.WithTimeout(context.Background(), time.Millisecond*time.Duration(timeout))
	defer cncl()
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}
	response, err := client.Do(request)
	if err != nil {
		env.log(Error, "doGet", err.Error())
		return nil, err
	}
	defer response.Body.Close()
	body, err := ioutil.ReadAll(response.Body)
	if err != nil {
		env.log(Error, "doGet", err.Error())
		return nil, err
	}
	return body, nil
}

func (env *environment) hasParentFilePath(path string) (*fileInfo, error) {
	defer env.trace(time.Now(), "hasParentFilePath", path)
	currentFolder := env.getcwd()
	for {
		searchPath := filepath.Join(currentFolder, path)
		info, err := os.Stat(searchPath)
		if err == nil {
			return &fileInfo{
				parentFolder: currentFolder,
				path:         searchPath,
				isDir:        info.IsDir(),
			}, nil
		}
		if !os.IsNotExist(err) {
			return nil, err
		}
		if dir := filepath.Dir(currentFolder); dir != currentFolder {
			currentFolder = dir
			continue
		}
		env.log(Error, "hasParentFilePath", err.Error())
		return nil, errors.New("no match at root level")
	}
}

func (env *environment) stackCount() int {
	defer env.trace(time.Now(), "stackCount")
	if *env.args.StackCount < 0 {
		return 0
	}
	return *env.args.StackCount
}

func (env *environment) cache() cache {
	return env.fileCache
}

func (env *environment) close() {
	env.fileCache.close()
}

func (env *environment) logs() string {
	return env.logBuilder.String()
}

func cleanHostName(hostName string) string {
	garbage := []string{
		".lan",
		".local",
		".localdomain",
	}
	for _, g := range garbage {
		if strings.HasSuffix(hostName, g) {
			hostName = strings.Replace(hostName, g, "", 1)
		}
	}
	return hostName
}

func returnOrBuildCachePath(path string) string {
	// validate root path
	if _, err := os.Stat(path); err != nil {
		return ""
	}
	// validate oh-my-posh folder, if non existent, create it
	cachePath := path + "/oh-my-posh"
	if _, err := os.Stat(cachePath); err == nil {
		return cachePath
	}
	if err := os.Mkdir(cachePath, 0755); err != nil {
		return ""
	}
	return cachePath
}