const std = @import("std");
const c = @cImport({
    @cInclude("linux/input.h");
    @cInclude("libevdev-1.0/libevdev/libevdev.h");
    @cInclude("errno.h");
});

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

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

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

fn event_write(event: *const c.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);
}

fn device_open() !void {}

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    const allocator = gpa.allocator();
    defer _ = gpa.deinit();

    const args = try std.process.argsAlloc(allocator);

    if (args.len != 2) {
        std.debug.print("error: expected one argument", .{});
        std.os.exit(1);
    }
    const dev_name = args[1];
    var dev_fd = try std.fs.openFileAbsolute(dev_name, .{});

    const dev = c.libevdev_new();
    if (c.libevdev_set_fd(dev, dev_fd.handle) < 0) {
        std.debug.print("evdev: failed creating device from descriptor", .{});
        std.os.exit(1);
    }
    if (c.libevdev_grab(dev, c.LIBEVDEV_GRAB) < 0) {
        std.debug.print("evdev: failed grabbing device", .{});
        std.os.exit(1);
    }

    var write_esc_lshift: bool = undefined;
    var write_esc_rshift: bool = undefined;
    var is_lshift_down: bool = false;
    var is_rshift_down: bool = false;

    outer: while (true) {
        var event: c.input_event = undefined;
        var rc = c.libevdev_next_event(dev, c.LIBEVDEV_READ_FLAG_NORMAL | c.LIBEVDEV_READ_FLAG_BLOCKING, @ptrCast(&event));

        while (rc == c.LIBEVDEV_READ_STATUS_SYNC) {
            rc = c.libevdev_next_event(dev, c.LIBEVDEV_READ_FLAG_SYNC, @ptrCast(&event));
        }

        if (rc == -c.EAGAIN) {
            continue :outer;
        }

        if (rc != c.LIBEVDEV_READ_STATUS_SUCCESS) {
            break :outer;
        }

        if (event.type == c.EV_MSC and event.type == c.MSC_SCAN) {
            continue :outer;
        }

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

        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 = c.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();
        }
    }
}