//! 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]
#![no_main]

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;

// 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);
    fn rust_esp_log_i(tag: *const u8, format: *const u8);
}

/// 日志函数
fn log_info(message: &'static str) {
    // 转换 Rust 静态字符串为 C 字符串
    let tag = b"RustApp\0";
    
    // 直接使用静态字符串的指针，确保它在整个程序生命周期内有效
    // 注意：Rust 的字符串字面量已经以 null 结尾
    let msg_ptr = message.as_ptr();
    
    unsafe {
        rust_esp_log_i(tag.as_ptr(), msg_ptr);
    }
}

#[no_mangle]
extern "C" fn rust_app_main() {
    // 初始化代码
    log_info("Rust app started");
    loop {
        log_info("Sending random key...");
        send_random_key();
        // 等待 5 秒 (5000ms / 10ms per tick = 500 ticks)
        log_info("Waiting for 5 seconds...");
        unsafe {
            rust_vTaskDelay(500);
        }
    }
}

#[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 {
            log_info("USB mounted!");
            break;
        }
        // 等待 100ms (100ms / 10ms per tick = 10 ticks)
        log_info("USB not mounted yet");
        unsafe {
            rust_vTaskDelay(10);
        }
    }

    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];
        log_info("Sending key press event");
        unsafe {
            rust_send_keyboard_report(REPORT_ID_KEYBOARD, 0, keycode.as_ptr());
        }

        // 等待 50ms (50ms / 10ms per tick = 5 ticks)
        log_info("Waiting for 50ms...");
        unsafe {
            rust_vTaskDelay(5);
        }

        // 发送随机键释放事件
        let keycode = [0, 0, 0, 0, 0, 0];
        log_info("Sending key release event");
        unsafe {
            rust_send_keyboard_report(REPORT_ID_KEYBOARD, 0, keycode.as_ptr());
        }
    } else {
        log_info("USB not mounted after 10 attempts");
    }
}

/// 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
    }
}