package main

import (
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path"
	"strings"
	"time"
)

const (
	STAMP_FORMAT = "20060102-150405"
)

func checkUsage(debugFlag string, args []string) {
	if debugFlag != "" && debugFlag != "lexer" && debugFlag != "parser" && debugFlag != "search" {
		fmt.Fprintln(os.Stderr, "invalid value for 'debug'")
		os.Exit(1)
	}
	if len(args) != 1 {
		fmt.Fprintln(os.Stderr, "USAGE:", os.Args[0], "FILE")
		os.Exit(1)
	}
}

func outfile(infile string) io.Writer {
	basename := path.Base(infile)
	extension := path.Ext(basename)
	basename = strings.TrimSuffix(basename, extension)
	name := basename + time.Now().Format(STAMP_FORMAT) + ".txt"
	f, err := os.OpenFile(name, os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	fmt.Println(name)
	return f
}

func main() {
	var debug string
	var stdout bool
	flag.StringVar(&debug, "debug", "", "debug output of 'lexer', 'parser' or 'search'")
	flag.BoolVar(&stdout, "stdout", false, "use stdout instead of file output")
	flag.Parse()
	args := flag.Args()
	checkUsage(debug, args)
	filename := args[0]
	bytes, err := ioutil.ReadFile(filename)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
	} else {
		input := []rune(string(bytes))
		switch debug {
		case "lexer":
			DebugLexer(input, os.Stdout)
		case "parser":
			DebugParser(input, os.Stdout)
		case "search":
			DebugSearch(input)
		default:
			parsed := NewParser(input).Parse()
			var writer io.Writer
			if stdout {
				writer = os.Stdout
			} else {
				writer = outfile(filename)
			}
			generator := NewStdGenerator(writer)
			generator.Generate(parsed)
		}
	}
}