//! Rust application for ESP32-S3
//! 
//! This module provides the main Rust application logic
//! that interacts with the USB HID interface implemented in C/TinyUSB.

#![no_std]

use esp_backtrace as _;

#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
    loop {
        core::hint::spin_loop();
    }
}

// HID 键码常量
const HID_KEY_A: u8 = 0x04;
const REPORT_ID_KEYBOARD: u8 = 1;
const PD_MS_TO_TICKS: u32 = 1;

// FFI 函数声明
extern "C" {
    fn rust_is_usb_mounted() -> bool;
    fn rust_send_keyboard_report(report_id: u8, modifier: u8, keycode: *const u8);
    fn rust_vTaskDelay(xTicksToDelay: u32);
}

#[no_mangle]
extern "C" fn rust_app_main() {
    // 初始化代码
    loop {
        send_random_key();
        // 等待 5 秒
        unsafe {
            rust_vTaskDelay(5000 * PD_MS_TO_TICKS);
        }
    }
}

#[export_name = "rust_usb_callback"]
pub unsafe extern "C" fn usb_callback(_event: u32) {
}

/// 发送 A-Z 随机键的按键事件
fn send_random_key() {
    // 等待 USB 设备挂载
    let mut mounted = false;
    for _ in 0..10 {
        mounted = unsafe {
            rust_is_usb_mounted()
        };
        if mounted {
            break;
        }
        // 等待 100ms
        unsafe {
            rust_vTaskDelay(100 * PD_MS_TO_TICKS);
        }
    }

    if mounted {
        // 生成随机的 A-Z 键码
        let random_value = get_random_u32() % 26;
        let random_key = HID_KEY_A + (random_value as u8);
        
        // 发送随机键按下事件
        let keycode = [random_key, 0, 0, 0, 0, 0];
        unsafe {
            rust_send_keyboard_report(REPORT_ID_KEYBOARD, 0, keycode.as_ptr());
        }

        // 等待 50ms
        unsafe {
            rust_vTaskDelay(50 * PD_MS_TO_TICKS);
        }

        // 发送随机键释放事件
        let keycode = [0, 0, 0, 0, 0, 0];
        unsafe {
            rust_send_keyboard_report(REPORT_ID_KEYBOARD, 0, keycode.as_ptr());
        }
    }
}

/// 获取随机数
fn get_random_u32() -> u32 {
    // 使用简单的线性同余生成器
    static mut SEED: u32 = 42;
    unsafe {
        SEED = SEED.wrapping_mul(1103515245).wrapping_add(12345);
        SEED
    }
}