package day10

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func clearLine(line *[]rune) {
	for idx := range *line {
		(*line)[idx] = '.'
	}
}

func printLine(line *[]rune) {
	for _, c := range *line {
		fmt.Printf("%c", c)
	}
	fmt.Println()
}

func registerCycle(cycle int, x int, line *[]rune) int {
	result := 0
	var position int

	for position = cycle - 1; position > 40; position -= 40 {
	}

	if cycle == 20 || (cycle > 20 && ((cycle-20)%40 == 0)) {
		result = x * cycle
		//fmt.Println("register cycle", cycle, "value of x is", x, "signal strength is", result)
	}

	//if position == 0 {
	//	fmt.Println("position is", position, "and x is", x)
	//}

	if position >= x-1 && position <= x+1 {
		(*line)[position] = '#'
	}

	if position == 40 {
		printLine(line)
		clearLine(line)
	}

	return result
}

func Run(filename string) {
	file, err := os.Open(filename)
	if err != nil {
		fmt.Println("Error opening file:", err)
		return
	}

	scanner := bufio.NewScanner(file)
	scanner.Split(bufio.ScanLines)
	cycle := 1
	x := 1
	signalStrengthSum := 0
	currentLine := []rune{'.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.', '.'}
	if len(currentLine) != 40 {
		fmt.Println("line length", len(currentLine))
		return
	}

	registerCycle(cycle, x, &currentLine)
	for scanner.Scan() {
		line := scanner.Text()

		if strings.HasPrefix(line, "addx ") {
			cycle += 1
			signalStrengthSum += registerCycle(cycle, x, &currentLine)
			cycle += 1
			mod, err := strconv.Atoi(string(line[5:]))
			if err != nil {
				fmt.Println("Invalid x modifier", err, "having read", string(line[5:]))
				return
			}
			x += mod
			signalStrengthSum += registerCycle(cycle, x, &currentLine)
		} else if strings.HasPrefix(line, "noop") {
			cycle += 1
			signalStrengthSum += registerCycle(cycle, x, &currentLine)
		} else {
			fmt.Println("PANIC: Unknown instruction:", line)
			return
		}
	}

	file.Close()
	//printLine(line)

	fmt.Println("Signal strength fun", signalStrengthSum)
}