const std = @import("std");
const util = @import("util.zig");
const mem = std.mem;

pub fn main() !void {
    const input = @embedFile("data/day08.txt");
    const sln = try solve(util.gpa, input);
    std.debug.print("{d}\n", .{sln.a});
    std.debug.print("{d}\n", .{sln.b});
}

const Solution = struct {
    a: usize,
    b: usize,
};

const Step = struct {
    left: [3]u8,
    right: [3]u8,
};

fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
    var states = std.AutoHashMap([3]u8, Step).init(alloc);
    defer states.deinit();

    var position: [3]u8 = "AAA".*;

    var it = util.splitLines(input);
    const steps = it.next().?;
    while (it.next()) |line| {
        if (line.len == 0) continue;
        try states.put(line[0..3].*, .{ .left = line[7..10].*, .right = line[12..15].* });
    }

    var count: u16 = 0;
    while (!mem.eql(u8, &position, "ZZZ")) : (count += 1) {
        const currState = states.get(position) orelse break; // ???????
        position = if (steps[count % steps.len] == 'L') currState.left else currState.right;
    }

    return .{ .a = count, .b = 0 };
}

test "silver" {
    const input =
        \\RL
        \\
        \\AAA = (BBB, CCC)
        \\BBB = (DDD, EEE)
        \\CCC = (ZZZ, GGG)
        \\DDD = (DDD, DDD)
        \\EEE = (EEE, EEE)
        \\GGG = (GGG, GGG)
        \\ZZZ = (ZZZ, ZZZ)
    ;
    const sln = try solve(std.testing.allocator, input);
    try std.testing.expectEqual(@as(usize, 2), sln.a);
}

test "gold" {
    const input =
        \\LR
        \\
        \\11A = (11B, XXX)
        \\11B = (XXX, 11Z)
        \\11Z = (11B, XXX)
        \\22A = (22B, XXX)
        \\22B = (22C, 22C)
        \\22C = (22Z, 22Z)
        \\22Z = (22B, 22B)
        \\XXX = (XXX, XXX)
    ;
    const sln = try solve(std.testing.allocator, input);
    try std.testing.expectEqual(@as(usize, 0), sln.b);
}