package main

import (
	"bufio"
	"flag"
	"fmt"
	"os"
)

var (
	file string
)

func main() {
	flag.Parse()
	args := flag.Args()

	if len(args) > 1 {
		fmt.Printf("Usage: %s [script]", args[0])
		os.Exit(64)
	} else if len(args) == 1 {
		runFile(args[0])
	} else {
		repl()
	}
}

func runFile(filename string) {
	bs, err := os.ReadFile(filename)
	if err != nil {
		fmt.Printf("unable to read file '%s':\n\t%s", filename, err.Error())
		os.Exit(64)
	}

	if !run(string(bs)) {
		os.Exit(65)
	}
}

func repl() {
	s := bufio.NewScanner(os.Stdin)
	for {
		fmt.Printf("repl> ")
		s.Scan()
		text := s.Text()

		if text == ":q" {
			return
		}

		run(text)
		if err := s.Err(); err != nil {
			panic(err)
		}
	}
}

func run(source string) bool {
	s := newScanner(source)
	tokens, ok := s.ScanTokens()
	if !ok {
		return false
	}

	p := newParser(tokens)
	expr, err := p.Parse()
	if err != nil {
		return false
	}

	printer := &astPrinter{}
	fmt.Println(printer.print(expr))

	return true
}

func reportErr(line int, message string) {
	report(line, "", message)
}

func reportSyntaxError(token *token, message string) {
	if token.Type == tokenTypeEOF {
		report(token.Line, "at EOF", message)
	} else {
		report(token.Line, "at \""+token.Lexeme+"\"", message)
	}
}

func report(line int, where, message string) {
	fmt.Printf("[line %d] Error%s: %s\n", line, where, message)
}