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use std::ffi::CString;
use windows::Win32::UI::Input::KeyboardAndMouse::{
    GetKeyNameTextA, MapVirtualKeyA, VkKeyScanA, MAPVK_VK_TO_VSC,
};

/// Converts a key's name to its keycode.
pub fn name_to_keycode(name: u8) -> u32 {
    let result = unsafe { VkKeyScanA(name as _) } as u32;
    result & 0xff
}

/// Converts a keycode to the key's name.
pub fn keycode_to_name(keycode: u32) -> Option<String> {
    let scan_code = unsafe { MapVirtualKeyA(keycode, MAPVK_VK_TO_VSC) };
    let mut buffer = vec![0; 32];

    let result = unsafe { GetKeyNameTextA((scan_code << 16) as i32, &mut buffer) };

    if result > 0 {
        unsafe { buffer.set_len(result as usize) }
        CString::new(buffer)
            .ok()
            .and_then(|string| string.into_string().ok())
    } else {
        None
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn name_to_code() {
        assert_eq!(65, name_to_keycode(b'A'));
        assert_eq!(70, name_to_keycode(b'F'));
    }

    #[test]
    fn code_to_name() {
        assert_eq!(
            Some(String::from("ALT")),
            keycode_to_name(18).map(|name| name.to_uppercase())
        );
        assert_eq!(
            Some(String::from("A")),
            keycode_to_name(65).map(|name| name.to_uppercase())
        );
        assert_eq!(
            Some(String::from("F")),
            keycode_to_name(70).map(|name| name.to_uppercase())
        );
    }
}