//! HID Function implementation for USB Gadget

use std::path::{Path, PathBuf};
use tracing::debug;

use super::configfs::{create_dir, create_symlink, remove_dir, remove_file, write_bytes, write_file};
use super::function::{FunctionMeta, GadgetFunction};
use super::report_desc::{KEYBOARD_WITH_LED, MOUSE_ABSOLUTE, MOUSE_RELATIVE};
use crate::error::Result;

/// HID function type
#[derive(Debug, Clone)]
pub enum HidFunctionType {
    /// Keyboard with LED feedback support
    /// Uses 2 endpoints: IN (reports) + OUT (LED status)
    Keyboard,
    /// Relative mouse (traditional mouse movement)
    /// Uses 1 endpoint: IN
    MouseRelative,
    /// Absolute mouse (touchscreen-like positioning)
    /// Uses 1 endpoint: IN
    MouseAbsolute,
}

impl HidFunctionType {
    /// Get endpoints required for this function type
    pub fn endpoints(&self) -> u8 {
        match self {
            HidFunctionType::Keyboard => 2, // IN + OUT for LED
            HidFunctionType::MouseRelative => 1,
            HidFunctionType::MouseAbsolute => 1,
        }
    }

    /// Get HID protocol
    pub fn protocol(&self) -> u8 {
        match self {
            HidFunctionType::Keyboard => 1,      // Keyboard
            HidFunctionType::MouseRelative => 2, // Mouse
            HidFunctionType::MouseAbsolute => 2, // Mouse
        }
    }

    /// Get HID subclass
    pub fn subclass(&self) -> u8 {
        match self {
            HidFunctionType::Keyboard => 1,      // Boot interface
            HidFunctionType::MouseRelative => 1, // Boot interface
            HidFunctionType::MouseAbsolute => 0, // No boot interface (absolute not in boot protocol)
        }
    }

    /// Get report length in bytes
    pub fn report_length(&self) -> u8 {
        match self {
            HidFunctionType::Keyboard => 8,
            HidFunctionType::MouseRelative => 4,
            HidFunctionType::MouseAbsolute => 6,
        }
    }

    /// Get report descriptor
    pub fn report_desc(&self) -> &'static [u8] {
        match self {
            HidFunctionType::Keyboard => KEYBOARD_WITH_LED,
            HidFunctionType::MouseRelative => MOUSE_RELATIVE,
            HidFunctionType::MouseAbsolute => MOUSE_ABSOLUTE,
        }
    }

    /// Get description
    pub fn description(&self) -> &'static str {
        match self {
            HidFunctionType::Keyboard => "Keyboard",
            HidFunctionType::MouseRelative => "Relative Mouse",
            HidFunctionType::MouseAbsolute => "Absolute Mouse",
        }
    }
}

/// HID Function for USB Gadget
#[derive(Debug, Clone)]
pub struct HidFunction {
    /// Instance number (usb0, usb1, ...)
    instance: u8,
    /// Function type
    func_type: HidFunctionType,
    /// Cached function name (avoids repeated allocation)
    name: String,
}

impl HidFunction {
    /// Create a keyboard function
    pub fn keyboard(instance: u8) -> Self {
        Self {
            instance,
            func_type: HidFunctionType::Keyboard,
            name: format!("hid.usb{}", instance),
        }
    }

    /// Create a relative mouse function
    pub fn mouse_relative(instance: u8) -> Self {
        Self {
            instance,
            func_type: HidFunctionType::MouseRelative,
            name: format!("hid.usb{}", instance),
        }
    }

    /// Create an absolute mouse function
    pub fn mouse_absolute(instance: u8) -> Self {
        Self {
            instance,
            func_type: HidFunctionType::MouseAbsolute,
            name: format!("hid.usb{}", instance),
        }
    }

    /// Get function path in gadget
    fn function_path(&self, gadget_path: &Path) -> PathBuf {
        gadget_path.join("functions").join(self.name())
    }

    /// Get expected device path (e.g., /dev/hidg0)
    pub fn device_path(&self) -> PathBuf {
        PathBuf::from(format!("/dev/hidg{}", self.instance))
    }
}

impl GadgetFunction for HidFunction {
    fn name(&self) -> &str {
        &self.name
    }

    fn endpoints_required(&self) -> u8 {
        self.func_type.endpoints()
    }

    fn meta(&self) -> FunctionMeta {
        FunctionMeta {
            name: self.name().to_string(),
            description: self.func_type.description().to_string(),
            endpoints: self.endpoints_required(),
            enabled: true,
        }
    }

    fn create(&self, gadget_path: &Path) -> Result<()> {
        let func_path = self.function_path(gadget_path);
        create_dir(&func_path)?;

        // Set HID parameters
        write_file(&func_path.join("protocol"), &self.func_type.protocol().to_string())?;
        write_file(&func_path.join("subclass"), &self.func_type.subclass().to_string())?;
        write_file(&func_path.join("report_length"), &self.func_type.report_length().to_string())?;

        // For keyboard, enable OUT endpoint for LED feedback
        // no_out_endpoint: 0 = enable OUT endpoint, 1 = disable
        if matches!(self.func_type, HidFunctionType::Keyboard) {
            let no_out_path = func_path.join("no_out_endpoint");
            if no_out_path.exists() || func_path.exists() {
                // Try to write, ignore error if file doesn't exist yet
                let _ = write_file(&no_out_path, "0");
            }
        }

        // Write report descriptor
        write_bytes(&func_path.join("report_desc"), self.func_type.report_desc())?;

        debug!("Created HID function: {} at {}", self.name(), func_path.display());
        Ok(())
    }

    fn link(&self, config_path: &Path, gadget_path: &Path) -> Result<()> {
        let func_path = self.function_path(gadget_path);
        let link_path = config_path.join(self.name());

        if !link_path.exists() {
            create_symlink(&func_path, &link_path)?;
            debug!("Linked HID function {} to config", self.name());
        }

        Ok(())
    }

    fn unlink(&self, config_path: &Path) -> Result<()> {
        let link_path = config_path.join(self.name());
        remove_file(&link_path)?;
        debug!("Unlinked HID function {}", self.name());
        Ok(())
    }

    fn cleanup(&self, gadget_path: &Path) -> Result<()> {
        let func_path = self.function_path(gadget_path);
        remove_dir(&func_path)?;
        debug!("Cleaned up HID function {}", self.name());
        Ok(())
    }
}

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

    #[test]
    fn test_hid_function_types() {
        assert_eq!(HidFunctionType::Keyboard.endpoints(), 2);
        assert_eq!(HidFunctionType::MouseRelative.endpoints(), 1);
        assert_eq!(HidFunctionType::MouseAbsolute.endpoints(), 1);

        assert_eq!(HidFunctionType::Keyboard.report_length(), 8);
        assert_eq!(HidFunctionType::MouseRelative.report_length(), 4);
        assert_eq!(HidFunctionType::MouseAbsolute.report_length(), 6);
    }

    #[test]
    fn test_hid_function_names() {
        let kb = HidFunction::keyboard(0);
        assert_eq!(kb.name(), "hid.usb0");
        assert_eq!(kb.device_path(), PathBuf::from("/dev/hidg0"));

        let mouse = HidFunction::mouse_relative(1);
        assert_eq!(mouse.name(), "hid.usb1");
    }
}