const std = @import("std");
const path = "../data/day24/input.txt";
const input_counter = 14; // number of instruction blocks
const input_length = 18; // items in each instruction block
const offset0 = 5;
const offset1 = 15;
const PairType = i9;
const Pair = [2]PairType;
const Pairs = [input_counter]Pair;
pub fn main() !void {
    var timer = try std.time.Timer.start();
    const ret = try second();
    const t = timer.lap() / 1000;
    try std.testing.expectEqual(@as(usize, 93185111127911), ret);
    std.debug.print("Day 24b result: {d} \t\ttime: {d}µs\n", .{ ret, t });
}
pub fn second() !usize {
    const start = 1;
    const pairs = try parseInput();
    const allocator = std.testing.allocator;
    var stack = std.ArrayList(Pair).init(allocator);
    defer stack.deinit();
    var ret: usize = 0;
    var i: usize = 0;
    while (i < input_counter) : (i += 1) {
        if (pairs[i][0] > 0) {
            try stack.append(Pair{ pairs[i][1], @intCast(PairType, i) });
        } else {
            const p = stack.pop();
            var add: PairType = start;
            while (add + p[0] + pairs[i][0] < start) {
                add += 1;
            }
            ret += @intCast(usize, add) *
                try std.math.powi(usize, 10, @intCast(usize, input_counter - 1 - p[1]));
            ret += @intCast(usize, (add + p[0] + pairs[i][0])) *
                try std.math.powi(usize, 10, input_counter - 1 - i);
        }
    }
    return ret;
}
fn parseInput() !Pairs {
    const input = @embedFile(path);
    var line = std.mem.split(u8, input, "\n");
    var ret: Pairs = undefined;
    var line_counter: usize = 0;
    var item_counter: usize = 0;
    while (line.next()) |l| : (line_counter += 1) {
        if (line_counter == input_length * item_counter + offset0) {
            var token = std.mem.tokenize(u8, l, " ");
            _ = token.next();
            _ = token.next();
            ret[item_counter][0] = try std.fmt.parseInt(PairType, token.next().?, 10);
        }
        if (line_counter == input_length * item_counter + offset1) {
            var token = std.mem.tokenize(u8, l, " ");
            _ = token.next();
            _ = token.next();
            ret[item_counter][1] = try std.fmt.parseInt(PairType, token.next().?, 10);
            item_counter += 1;
        }
    }
    return ret;
}
test "day24b" {
    try std.testing.expectEqual(@as(usize, 93185111127911), try second());
}