import { readFileSync } from 'fs'

enum Tile {
    Round = 'O',
    Cube = '#',
    Empty = '.',
}

type Grid = Tile[][]

function parse(input: string): Grid {
    return input
        .trim()
        .split('\n')
        .map((line) => line.split('').map((char) => char as Tile))
}

function render(grid: Grid) {
    for (let y = 0; y < grid.length; y++) {
        let row = ''
        for (let x = 0; x < grid[0].length; x++) {
            row += String(grid[y][x])
        }
        console.log(row)
    }
    console.log('----------------------------------------')
}

function fullyTilt(
    grid: Grid,
    direction: 'north' | 'south' | 'east' | 'west',
): Grid {
    switch (direction) {
        case 'north':
            return applyUntilZero(grid, tiltNorth)
        case 'south':
            return applyUntilZero(grid, tiltSouth)
        case 'west':
            return applyUntilZero(grid, tiltWest)
        case 'east':
            return applyUntilZero(grid, tiltEast)
    }
}

// Returns the number of round rocks that moved north one cell after one round of simulation.
function tiltNorth(grid: Grid): number {
    let count = 0
    for (let y = 1; y < grid.length; y++) {
        for (let x = 0; x < grid[0].length; x++) {
            if (grid[y][x] === Tile.Round && grid[y - 1][x] === Tile.Empty) {
                grid[y - 1][x] = Tile.Round
                grid[y][x] = Tile.Empty
                count++
            }
        }
    }
    return count
}

function tiltSouth(grid: Grid): number {
    let count = 0
    for (let y = grid.length - 2; y >= 0; y--) {
        for (let x = 0; x < grid[0].length; x++) {
            if (grid[y][x] === Tile.Round && grid[y + 1][x] === Tile.Empty) {
                grid[y + 1][x] = Tile.Round
                grid[y][x] = Tile.Empty
                count++
            }
        }
    }
    return count
}

function tiltWest(grid: Grid): number {
    let count = 0
    for (let x = 1; x < grid[0].length; x++) {
        for (let y = 0; y < grid.length; y++) {
            if (grid[y][x] === Tile.Round && grid[y][x - 1] === Tile.Empty) {
                grid[y][x - 1] = Tile.Round
                grid[y][x] = Tile.Empty
                count++
            }
        }
    }
    return count
}

function tiltEast(grid: Grid): number {
    let count = 0
    for (let x = grid[0].length - 2; x >= 0; x--) {
        for (let y = 0; y < grid.length; y++) {
            if (grid[y][x] === Tile.Round && grid[y][x + 1] === Tile.Empty) {
                grid[y][x + 1] = Tile.Round
                grid[y][x] = Tile.Empty
                count++
            }
        }
    }
    return count
}

function applyUntilZero(input: Grid, fn: (grid: Grid) => number): Grid {
    let result = 0
    while ((result = fn(input)) !== 0) {}
    return input
}

function calcWeight(grid: Grid): number {
    let total = 0
    for (let y = 0; y < grid.length; y++) {
        let weight = grid.length - y
        for (let x = 0; x < grid[0].length; x++) {
            if (grid[y][x] === Tile.Round) {
                total += weight
            }
        }
    }
    return total
}

function part1(input: string): number {
    const grid = parse(input)
    render(grid)
    let moved = 0
    while ((moved = tiltNorth(grid)) > 0) {}
    return calcWeight(grid)
}

function part2(input: string): number {
    const grid = parse(input)
    const seen = new Map<string, number>() // grid -> loop first seen
    let cycling = false
    const end = 1_000_000_000
    for (let i = 0; i < end; i++) {
        fullyTilt(grid, 'north')
        fullyTilt(grid, 'west')
        fullyTilt(grid, 'south')
        fullyTilt(grid, 'east')
        const key = String(grid)
        if (!cycling && seen.has(key)) {
            const cycleStart = seen.get(key)!
            const period = i - cycleStart
            i = end - ((end - cycleStart) % period)
            cycling = true
        }
        seen.set(key, i)
    }
    return calcWeight(grid)
}

let input = `O....#....
O.OO#....#
.....##...
OO.#O....O
.O.....O#.
O.#..O.#.#
..O..#O..O
.......O..
#....###..
#OO..#....`

input = readFileSync('day14.txt', { encoding: 'utf8' })

console.log('part 1:', part1(input))
console.log('part 2:', part2(input))