const std = @import("std");
const print = std.debug.print;
const input = @cImport(@cInclude("linux/input.h"));

const CapsLockDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_CAPSLOCK, .value = 1, .time = undefined };
const CapsLockUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_CAPSLOCK, .value = 0, .time = undefined };
const EscDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_ESC, .value = 1, .time = undefined };
const EscUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_ESC, .value = 0, .time = undefined };
const LShiftDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_LEFTSHIFT, .value = 1, .time = undefined };
const LShiftUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_LEFTSHIFT, .value = 0, .time = undefined };
const RShiftDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_RIGHTSHIFT, .value = 1, .time = undefined };
const RShiftUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_RIGHTSHIFT, .value = 0, .time = undefined };
const Syn = input.input_event{ .type = input.EV_SYN, .code = input.SYN_REPORT, .value = 0, .time = undefined };

fn event_equal(e1: *const input.input_event, e2: *const input.input_event) bool {
    return (e1.*.type == e2.*.type) and (e1.*.code == e2.*.code) and (e1.*.value == e2.*.value);
}

fn event_read(event: *input.input_event) !void {
    event.* = try std.io.getStdIn().reader().readStruct(@TypeOf(event.*));
}

fn event_write(event: *const input.input_event) !void {
    try std.io.getStdOut().writer().writeStruct(event.*);
}

fn write_esc() !void {
    std.time.sleep(20000);
    try event_write(&EscDown);
    try event_write(&Syn);
    std.time.sleep(20000);
    try event_write(&EscUp);
}

pub fn main() !void {
    var event: input.input_event = undefined;
    var write_esc_lshift: bool = undefined;
    var write_esc_rshift: bool = undefined;
    var is_lshift_down: bool = false;
    var is_rshift_down: bool = false;

    while (true) {
        try event_read(&event);
        if (event.type == input.EV_MSC and event.type == input.MSC_SCAN) {
            continue;
        }

        if (event.type != input.EV_KEY) {
            try event_write(&event);
            continue;
        }

        write_esc_lshift = event_equal(&event, &LShiftUp) and is_lshift_down;
        write_esc_rshift = event_equal(&event, &RShiftUp) and is_rshift_down;
        is_lshift_down = event_equal(&event, &LShiftDown);
        is_rshift_down = event_equal(&event, &RShiftDown);

        if (event_equal(&event, &CapsLockUp) or event_equal(&event, &CapsLockDown)) {
            event.code = input.KEY_LEFTMETA;
        }

        try event_write(&event);

        if (write_esc_lshift) {
            write_esc_lshift = false;
            try write_esc();
        }

        if (write_esc_rshift) {
            write_esc_rshift = false;
            try write_esc();
        }
    }
}