package day21

import (
	"bytes"
	"fmt"
	"strconv"
	"strings"
	"tools"
)

var revIndex = map[int]int{
	0: 1,
	1: 1,
	2: 6,
	3: 2,
	4: 7,
	5: 3,
	6: 8,
	7: 4,
}

func scramble(s string, instr []string, reverse bool) string {
	sb := []byte(s)
	for _, inst := range instr {
		parts := strings.Split(inst, " ")
		if parts[0] == "swap" && parts[1] == "position" {
			x, _ := strconv.Atoi(parts[2])
			y, _ := strconv.Atoi(parts[5])
			sb[x], sb[y] = sb[y], sb[x]
		} else if parts[0] == "swap" && parts[1] == "letter" {
			x := bytes.Index(sb, []byte(parts[2]))
			y := bytes.Index(sb, []byte(parts[5]))
			sb[x], sb[y] = sb[y], sb[x]
		} else if parts[0] == "rotate" && parts[1] == "left" {
			x, _ := strconv.Atoi(parts[2])
			if reverse {
				sb = append(sb[len(sb)-(x%len(sb)):], sb[:len(sb)-(x%len(sb))]...)
			} else {
				sb = append(sb[x%len(sb):], sb[:x%len(sb)]...)
			}
		} else if parts[0] == "rotate" && parts[1] == "right" {
			x, _ := strconv.Atoi(parts[2])
			if reverse {
				sb = append(sb[x%len(sb):], sb[:x%len(sb)]...)
			} else {
				sb = append(sb[len(sb)-(x%len(sb)):], sb[:len(sb)-(x%len(sb))]...)
			}
		} else if parts[0] == "rotate" && parts[1] == "based" {
			var x int
			if reverse {
				x = bytes.Index(sb, []byte(parts[6]))
				x = revIndex[x]
				sb = append(sb[x%len(sb):], sb[:x%len(sb)]...)
			} else {
				x = bytes.Index(sb, []byte(parts[6]))
				if x >= 4 {
					x++
				}
				x++
				sb = append(sb[len(sb)-(x%len(sb)):], sb[:len(sb)-(x%len(sb))]...)
			}
		} else if parts[0] == "reverse" && parts[1] == "positions" {
			x, _ := strconv.Atoi(parts[2])
			y, _ := strconv.Atoi(parts[4])
			var ns []byte
			for i := 0; i < x; i++ {
				ns = append(ns, sb[i])
			}
			for i := y; i >= x; i-- {
				ns = append(ns, sb[i])
			}
			sb = append(ns, sb[y+1:]...)
		} else if parts[0] == "move" && parts[1] == "position" {
			x, _ := strconv.Atoi(parts[2])
			y, _ := strconv.Atoi(parts[5])
			if reverse {
				c := sb[y]
				sb = append(sb[:y], sb[y+1:]...)
				sb = append(sb[:x+1], sb[x:]...)
				sb[x] = c
			} else {
				c := sb[x]
				sb = append(sb[:x], sb[x+1:]...)
				sb = append(sb[:y+1], sb[y:]...)
				sb[y] = c
			}
		} else {
			fmt.Println("ERROR: unknown instruction:", inst)
		}
	}

	return string(sb)
}

func Part1(puzzle tools.AoCPuzzle) interface{} {
	inp := puzzle.GetInputArray()
	startString := inp[0]
	password := scramble(startString, inp[1:], false)

	return password
}

func Part2(puzzle tools.AoCPuzzle) interface{} {
	inp := puzzle.GetInputArray()
	var rinp []string
	for x := len(inp) - 1; x > 0; x-- {
		rinp = append(rinp, inp[x])
	}
	startString := "fbgdceah"
	//startString := "gfdhebac"
	password := scramble(startString, rinp, true)

	return password
}