const std = @import("std");

pub fn loadFromStream(alloc: *std.mem.Allocator, stream: *std.fs.File.InStream.Stream) anyerror![]i32 {
    var program = try alloc.alloc(i32, 1024);

    var buf = [_]u8{0} ** 255;
    var i: u32 = 0;

    while (try stream.readUntilDelimiterOrEof(&buf, ',')) |num| {
        var trimmed = std.mem.trimRight(u8, num, "\r\n");
        program[i] = try std.fmt.parseInt(i32, trimmed, 10);

        std.debug.warn("{},", program[i]);

        i += 1;
    }

    std.debug.warn("\n");

    return program[0..program.len];
}

pub fn loadFromStdIn(alloc: *std.mem.Allocator) anyerror![]i32 {
    const file = std.io.getStdIn();
    const stream = &file.inStream().stream;

    return loadFromStream(alloc, stream);
}

pub fn run(program: []i32) void {
    // Initial program state
    var ip: u32 = 0;
    var exit: bool = false;

    // TODO: create a nice struct

    while (!exit) {
        //        std.debug.warn(" IP {d:4}: ", ip);
        const opcode = switch (program[ip]) {
            1 => {
                var a = program[@intCast(usize, program[ip + 1])];
                var b = program[@intCast(usize, program[ip + 2])];
                var dest = program[ip + 3];
                var result = a + b;

                //                std.debug.warn("ADD:  [{}] + [{}] => {} : {} + {} = {} => {}\n", ip + 1, ip + 2, dest, a, b, result, dest);
                program[@intCast(usize, dest)] = result;
                ip += 4;
            },
            2 => {
                var a = program[@intCast(usize, program[ip + 1])];
                var b = program[@intCast(usize, program[ip + 2])];
                var dest = program[ip + 3];
                var result = a * b;

                //                std.debug.warn("MULT: [{}] + [{}] => {} : {} + {} = {} => {}\n", ip + 1, ip + 2, dest, a, b, result, dest);
                program[@intCast(usize, dest)] = result;
                ip += 4;
            },
            99 => {
                //                std.debug.warn("EXIT\n");
                exit = true;
            },
            else => {
                std.debug.warn("Unknown opcode at IP {}: {}", ip, program[ip]);
                exit = true;
            },
        };
    }
}

const assert = std.debug.assert;

test "day 2 example 1" {
    var before: [12]i32 = .{ 1, 9, 10, 3, 2, 3, 11, 0, 99, 30, 40, 50 };
    var after: [12]i32 = .{ 3500, 9, 10, 70, 2, 3, 11, 0, 99, 30, 40, 50 };

    run(before[0..before.len]);
    assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
}

test "day 2 example 2" {
    var before: [5]i32 = .{ 1, 0, 0, 0, 99 };
    var after: [5]i32 = .{ 2, 0, 0, 0, 99 };

    run(before[0..before.len]);
    assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
}

test "day 2 example 3" {
    var before: [5]i32 = .{ 2, 3, 0, 3, 99 };
    var after: [5]i32 = .{ 2, 3, 0, 6, 99 };

    run(before[0..before.len]);
    assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
}

test "day 2 example 4" {
    var before: [6]i32 = .{ 2, 4, 4, 5, 99, 0 };
    var after: [6]i32 = .{ 2, 4, 4, 5, 99, 9801 };

    run(before[0..before.len]);
    assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
}

test "day 2 example 5" {
    var before: [9]i32 = .{ 1, 1, 1, 4, 99, 5, 6, 0, 99 };
    var after: [9]i32 = .{ 30, 1, 1, 4, 2, 5, 6, 0, 99 };

    run(before[0..before.len]);
    assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
}