// The compiler
package main

import (
	"log"
	"os"
	"strconv"
	"strings"
)

const ERROR_LOG_LINES = 5

func countTabs(line string) int {
	tabs := 0
	for _, rune := range line {
		if rune == '\t' {
			tabs++
		}
	}
	return tabs
}

func printCompilerError(file string, source string, err CompilerError) {
	sourceRunes := []rune(source)
	lines := strings.Split(source, "\n")
	line := 0
	col := 0
	var i uint64
	for i = 0; i < err.Position; i++ {
		col++
		if sourceRunes[i] == '\n' {
			line++
			col = 0
		}
	}

	log.Println("Failed to compile: " + err.Message + " (at " + file + ":" + strconv.Itoa(line+1) + ":" + strconv.Itoa(col+1) + ")")

	linesStart := max(0, line-ERROR_LOG_LINES)
	linesEnd := min(len(lines), line+ERROR_LOG_LINES+1)

	for _, line := range lines[linesStart:line] {
		println(strings.Replace(line, "\t", "    ", -1))
	}

	tabs := countTabs(lines[line])
	println(strings.Repeat(" ", col+tabs*3) + "v--- error occurs here ---")

	for _, line := range lines[line:linesEnd] {
		println(strings.Replace(line, "\t", "    ", -1))
	}
}

func main() {
	if len(os.Args) != 2 {
		log.Fatalln("Usage: " + os.Args[0] + " <file>")
	}

	file := os.Args[1]
	content, err := os.ReadFile(file)
	if err != nil {
		log.Fatalln("Cannot open input file.", err)
	}

	source := string(content)

	tokens, err := lexer(source)
	if err != nil {
		if c, ok := err.(CompilerError); ok {
			printCompilerError(file, source, c)
		} else {
			log.Println(err)
		}

		return
	}

	log.Printf("Tokens:\n%+#v\n\n", tokens)

	parser := Parser{Tokens: tokens}
	parsed, err := parser.parseFile()
	if err != nil {
		if c, ok := err.(CompilerError); ok {
			printCompilerError(file, source, c)
		} else {
			log.Println(err)
		}

		return
	}

	log.Printf("Parsed:\n%+#v\n\n", parsed)

	validator := Validator{file: parsed}
	errors := validator.validate()
	if len(errors) != 0 {
		for _, err = range errors {
			if c, ok := err.(CompilerError); ok {
				printCompilerError(file, source, c)
			} else {
				log.Println(err)
			}
		}

		if len(errors) != 0 {
			return
		}
	}

	log.Printf("Validated:\n%+#v\n\n", parsed)

	wat, err := backendWAT(*parsed)
	if err != nil {
		if c, ok := err.(CompilerError); ok {
			printCompilerError(file, source, c)
		} else {
			log.Println(err)
		}

		return
	}

	log.Println("WAT: " + wat)
	os.WriteFile("out.wat", []byte(wat), 0o644)
}