package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"math/rand"
	"os"
	"os/exec"
	"os/signal"
	"path/filepath"
	"runtime/debug"
	"sort"
	"strings"
	"syscall"
	"time"

	ln "github.com/peterh/liner"
	"golang.design/x/clipboard"
)

const version = "1.2.14"

const globalLibPath = "/usr/local/lib/slope/modules/"

var openFiles []*IOHandle
var replCounter int = 0
var line *ln.State
var initialTerm ln.ModeApplier = nil
var linerTerm ln.ModeApplier = nil
var panicOnException = true // default to `(exception-mode-panic)`
var ModBaseDir string = ""
var PreloadDir string = ""
var debugMode bool = false
var clipboardErr error

// Used in the repl so that input can continue,
// but potentially useful in other situations
func RecoverError() {
	if r := recover(); r != nil {
		if line == nil {
			fmt.Fprintf(os.Stderr, "\033[1mpanic:\033[0m %s\n", r)
			if debugMode {
				debug.PrintStack()
			}
			SafeExit(1)
		} else {
			fmt.Fprintf(os.Stderr, "\033[31mOops! %s\033[0m\n", r)
			if debugMode {
				debug.PrintStack()
			}
		}
	}
}

func BasicInstall(p string) {
	p = ExpandedAbsFilepath(p)
	ModBaseDir = ExpandedAbsFilepath(getModBaseDir())
	if _, err := os.Stat(filepath.Join(p, "main.slo")); err != nil {
		panic(fmt.Sprintf("Could not install %q, it does not exist or is not a valid module", p))
	}
	newPath := filepath.Join(ModBaseDir, filepath.Base(p))
	if _, err := os.Stat(newPath); err == nil {
		fmt.Printf("The module %q already exists, do you wish to overwrite it? ", filepath.Base(p))
		var answer string
		fmt.Scanln(&answer)
		if !strings.HasPrefix(strings.ToLower(answer), "y") {
			fmt.Println("Install cancelled")
			return
		}
	}

	cmd := exec.Command("cp", "-r", p, newPath)
	err := cmd.Run()
	if err != nil {
		panic(fmt.Sprintf("Could not install %q, there was an error while copying files", p))
	}
}

func Init() {
	openFiles = make([]*IOHandle, 0, 5)
	addGUIToLib()    // Will combine guiLib and stdLib
	addClipToLib()   // Will combine clipLib and stdLib
	addDialogToLib() // Will combine dialogLib and stdLib
	globalenv = env{stdLibrary, nil}
	ModBaseDir = ExpandedAbsFilepath(getModBaseDir())
	PreloadDir = ExpandedAbsFilepath(getPreloadDir())
	createDataDirs(ModBaseDir)
	createDataDirs(globalLibPath)
	createDataDirs(PreloadDir)
	c := make(chan os.Signal)
	signal.Notify(c, syscall.SIGINT)
	go handleSignals(c)
	clipboardErr = clipboard.Init()
	rand.Seed(time.Now().UnixNano())
}

func outputResult(txt string, environ *env) {
	defer RecoverError()
	parsed := Parse(txt)
	for i := range parsed.([]expression) {
		replCounter++
		evaluated := eval(parsed.([]expression)[i], environ)
		if e, ok := evaluated.(exception); panicOnException && ok {
			panic(string(e))
		}
		fmt.Printf("#%d=> %s\n", replCounter, String(evaluated, true))
	}
}

func Repl() {
	initialTerm, _ = ln.TerminalMode()
	line = ln.NewLiner()
	line.SetCtrlCAborts(true)
	linerTerm, _ = ln.TerminalMode()
	defer line.Close()

	histFile := ExpandedAbsFilepath(filepath.Join(getModBaseDir(), "..", historyFilename))
	if f, e := os.Open(histFile); e == nil {
		line.ReadHistory(f)
		f.Close()
	}

	// Add repl only proc, repl-flush
	globalenv.vars["repl-flush"] = func(a ...expression) expression {
		if f, e := os.Create(histFile); e == nil && line != nil {
			line.WriteHistory(f)
			f.Close()
		}
		return true
	}
	usageStrings["repl-flush"] = "(repl-flush) => #t\n\nForces a write to the repl history file, truncating the file, and writing the contents of the repl sesssion to the file:\n\n\t" + histFile

	// Set up completion
	line.SetTabCompletionStyle(ln.TabCircular)
	line.SetCompleter(func(l string) (c []string) {
		if len(l) == 0 {
			return
		}
		lastIndex := strings.LastIndexAny(l, "( \n")
		c = append(c, completeFromMap(usageStrings, l, lastIndex)...)
		c = append(c, completeFromMap(getAllModFuncNames(), l, lastIndex)...)
		sort.Strings(c)
		return
	})

	var text strings.Builder
	var cont bool
	var raw bool
	var match bool
	for {
		globalenv.vars[symbol("slope-interactive?")] = true
		if linerTerm != nil {
			linerTerm.ApplyMode()
		}
		in := prompt(line, cont, "!root!")
		if initialTerm != nil {
			initialTerm.ApplyMode()
		}
		if len(strings.TrimSpace(in)) == 0 && !raw {
			continue
		}
		text.WriteString(in)
		text.WriteRune('\n')
		var brokenString bool
		match, raw, brokenString = stringParensMatch(text.String())
		if !match && !brokenString {
			cont = true
		} else {
			cont = false
			outputResult(text.String(), &globalenv)
			text.Reset()
		}
	}
}

func RunCommand(s string) {
	if strings.Count(s, "(") != strings.Count(s, ")") {
		fmt.Fprintf(os.Stderr, "Invalid input string, uneven parens")
		SafeExit(1)
	}
	globalenv.vars[symbol("slope-interactive?")] = false
	p := Parse(s)
	for i := range p.([]expression) {
		replCounter++
		v := eval(p.([]expression)[i], &globalenv)
		if e, ok := v.(exception); panicOnException && ok {
			panic(string(e))
		}
	}
	SafeExit(0)
}

func RunModule(path string, relative bool) (env, error) {
	modDir := ModBaseDir
	modEnv := env{make(map[symbol]expression), &globalenv}
	revertToThisDir, err := os.Getwd()
	if err != nil {
		return modEnv, fmt.Errorf("System error during 'load-mod', could not get current working directory")
	}
	globalenv.vars[symbol("slope-interactive?")] = false

	var s string
	if !relative {
		// This branch is run from 'load-mod'
		err = os.Chdir(filepath.Join(modDir, path))
		if err != nil {
			err = os.Chdir(filepath.Join(globalLibPath, path))
			if err != nil {
				return modEnv, err
			}
			modDir = globalLibPath
		}
		fp := filepath.Join(modDir, path, "main.slo")
		b, err := ioutil.ReadFile(fp)
		if err != nil {
			_ = os.Chdir(revertToThisDir)
			return modEnv, fmt.Errorf("Module's main.slo file could not be read")
		}
		s = string(b)
	} else {
		// This branch is run from 'load-mod-file'
		p, _ := filepath.Abs(path)
		if !strings.HasPrefix(p, revertToThisDir) {
			return modEnv, fmt.Errorf("An attempt to load a file out of the module directory was made.")
		}
		b, err := ioutil.ReadFile(p)
		if err != nil {
			_ = os.Chdir(revertToThisDir)
			return modEnv, fmt.Errorf("Could not read module sub-file: %q", path)
		}
		s = string(b)
	}
	p := Parse(s)
	for i := range p.([]expression) {
		exp, ok := p.([]expression)[i].([]expression)
		if !ok {
			continue
		}

		proc, ok := exp[0].(symbol)
		if !ok {
			continue
		}
		switch proc {
		case symbol("define"), symbol("load-mod"), symbol("load-mod-file"):
			v := eval(p.([]expression)[i], &modEnv)
			if e, ok := v.(exception); panicOnException && ok {
				_ = os.Chdir(revertToThisDir)
				panic(string(e))
			} else if ok {
				_ = os.Chdir(revertToThisDir)
				return modEnv, fmt.Errorf(string(e))
			}
		}
	}
	_ = os.Chdir(revertToThisDir)
	return modEnv, nil
}

func RunFile(path string, load bool) error {
	replLine := replCounter
	globalenv.vars[symbol("slope-interactive?")] = false
	b, err := ioutil.ReadFile(path)
	if err != nil {
		if load {
			return err
		}
		fmt.Fprintf(os.Stderr, "Cannot read file %s", path)
		SafeExit(1)
	}
	s := string(b)
	p := Parse(s)
	for i := range p.([]expression) {
		replCounter++
		v := eval(p.([]expression)[i], &globalenv)
		if e, ok := v.(exception); panicOnException && ok {
			panic(string(e))
		}
	}
	if load {
		replCounter = replLine
		return nil
	}
	SafeExit(0)
	return nil // meaningless return since exit will occur
}

func prompt(l *ln.State, cont bool, inspectionID string) string {
	p := "> "
	if inspectionID != "!root!" {
		p = inspectionID + "> "
	}
	if cont {
		p = "+ "
	}
	val, err := l.Prompt(p)
	if err == ln.ErrPromptAborted {
		SafeExit(1)
	}
	l.AppendHistory(val)
	return val
}

func PrintVersion() {
	optionalModFormat := "Compiled Modules: %s\n"
	mods := make([]string, 0, 4)
	if clipboardIsOn {
		mods = append(mods, "clipboard")
	}
	if dialogIsOn {
		mods = append(mods, "dialog")
	}
	if guiIsOn {
		mods = append(mods, "gui")
	}
	optionalMods := ""
	if len(mods) > 0 {
		optionalMods = fmt.Sprintf(optionalModFormat, strings.Join(mods, ", "))
	}

	logo := "\033[7m┌─┐┬  ┌─┐┌─┐┌─┐\033[0m\n\033[7m└─┐│  │ │├─┘├┤ \033[0m\n\033[7m└─┘┴─┘└─┘┴  └─┘\033[0m"
	fmt.Printf("\033[1m%s\033[0m\nVersion: %s\n%s(c) 2021 sloum, see license with: (license)\n", logo, version, optionalMods)
}

func main() {
	defer RecoverError()
	verFlag := flag.Bool("v", false, "Print version information and exit")
	runCommand := flag.String("run", "", "A quoted string of commands to run and get output from")
	preloadEnv := flag.Bool("L", false, "Preload all files in the slope preload directory")
	bug := flag.Bool("debug", false, "Turns on debug mode allowing full stack traces of the underlying runtime on panic")
	install := flag.String("install", "", "Install a a module from a local path")

	flag.Parse()
	args := flag.Args()

	if *verFlag {
		PrintVersion()
		os.Exit(0)
	}

	if *install != "" {
		BasicInstall(*install)
	}

	if *bug {
		debugMode = true
	}

	Init()

	if *runCommand != "" {
		if *preloadEnv {
			preloadFiles()
		}
		if *runCommand == "--" {
			b, err := ioutil.ReadAll(os.Stdin)
			if err != nil {
				fmt.Fprintf(os.Stderr, "Could not read from stdin")
				SafeExit(1)
			}
			RunCommand(string(b))
		} else {
			RunCommand(*runCommand)
		}
	} else if len(args) > 0 {
		if *preloadEnv {
			preloadFiles()
		}
		RunFile(args[0], false)
	} else {
		PrintVersion()
		fmt.Printf("Type \033[1m(exit)\033[0m to quit\n\n")
		if *preloadEnv {
			preloadFiles()
		}
		Repl()
	}
}