package main

import (
	"fmt"
	"strconv"
	"strings"
)

type Day2Input [][]int64

func Day2Parse(lines []string) (Day2Input, error) {
	rows := make([][]int64, len(lines))
	for i, line := range lines {
		levelsCount := strings.Count(line, " ") + 1
		rows[i] = make([]int64, levelsCount)

		for j, level := range strings.Split(line, " ") {
			number, err := strconv.ParseInt(level, 10, 0)
			if err != nil {
				return nil, err
			}

			rows[i][j] = number
		}
	}

	return rows, nil
}

func absInt(value int64) int64 {
	if value < 0 {
		return -value
	} else {
		return value
	}
}

func Day2IsReportSafe(report []int64) bool {
	increasing := false
	decreasing := false

	for i := range len(report)-1 {
		if report[i+1] >= report[i] {
			increasing = true
		}
		if report[i+1] <= report[i] {
			decreasing = true
		}
		if absInt(report[i+1] - report[i]) >= 4 {
			return false
		}

		if increasing && decreasing {
			return false
		}
	}

	return !(increasing && decreasing) && (increasing || decreasing)
}

func Day2Part1(lines []string) error {
	input, err := Day2Parse(lines)
	if err != nil {
		return err
	}

	answer := 0
	for _, row := range input {
		if Day2IsReportSafe(row) {
			answer += 1
		}
	}

	fmt.Println(answer)

	return nil
}

func DeleteAtIndex(slice []int64, index int) []int64 {
	result := make([]int64, len(slice))
	copy(result, slice)
	return append(result[:index], result[index+1:]...)
}

func Day2Part2(lines []string) error {
	input, err := Day2Parse(lines)
	if err != nil {
		return err
	}

	answer := 0
	for _, row := range input {
		if Day2IsReportSafe(row) {
			answer += 1
			continue
		}

		for i := range len(row) {
			if Day2IsReportSafe(DeleteAtIndex(row, i)) {
				answer += 1
				break
			}
		}
	}

	fmt.Println(answer)

	return nil
}