//! UPP protocol frame structures

use serde::{Deserialize, Serialize};
use std::mem;

/// UPP USB frame header (5 bytes)
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[repr(C, packed)]
pub struct UPPUsbFrame {
    pub magic: u16,  // 0xBBAA
    pub cid: u8,     // Camera ID
    pub length: u16, // Data length (excluding header)
}

/// UPP camera frame header (7 bytes)
#[derive(Debug, Clone, Copy, Serialize, Deserialize, Default)]
#[repr(C, packed)]
pub struct UPPFrameHeader {
    pub frame_id: u8,      // Frame ID
    pub camera_number: u8, // Camera number
    pub flags: UPPFlags,   // Various flags
    pub g_sensor: u32,     // G-sensor data
}

/// UPP frame flags
#[derive(Debug, Clone, Copy, Serialize, Deserialize, Default)]
#[repr(C, packed)]
pub struct UPPFlags {
    pub has_g: bool,        // Has G-sensor data (bit 0)
    pub button_press: bool, // Button press detected (bit 1)
    pub other: u8,          // Other flags (bits 2-7, 6 bits total)
}

/// Complete UPP frame
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct UPPFrame {
    pub header: UPPFrameHeader,
    pub data: Vec<u8>,
}

impl UPPUsbFrame {
    /// Create a new UPP USB frame
    pub fn new(cid: u8, length: u16) -> Self {
        Self {
            magic: super::UPP_USB_MAGIC,
            cid,
            length,
        }
    }

    /// Get the total frame size including header
    /// Based on C++ POC: length field includes camera header + data, but not USB header
    pub fn total_size(&self) -> usize {
        mem::size_of::<Self>() + self.length as usize
    }

    /// Validate the frame magic number
    pub fn is_valid(&self) -> bool {
        self.magic == super::UPP_USB_MAGIC
    }

    /// Get the expected payload size (camera header + data)
    /// Based on C++ POC: this is what the length field represents
    pub fn expected_payload_size(&self) -> usize {
        self.length as usize
    }

    /// Get the expected data size (excluding camera header)
    /// Camera header is 7 bytes, so data size is payload - 7
    pub fn expected_data_size(&self) -> usize {
        if self.length >= 7 {
            self.length as usize - 7
        } else {
            0
        }
    }
}

impl UPPFrameHeader {
    /// Create a new UPP frame header
    pub fn new(
        frame_id: u8,
        camera_number: u8,
        has_g: bool,
        button_press: bool,
        g_sensor: u32,
    ) -> Self {
        Self {
            frame_id,
            camera_number,
            flags: UPPFlags {
                has_g,
                button_press,
                other: 0,
            },
            g_sensor,
        }
    }

    /// Check if this frame has G-sensor data
    pub fn has_g_sensor(&self) -> bool {
        self.flags.has_g
    }

    /// Check if button press was detected
    pub fn button_pressed(&self) -> bool {
        self.flags.button_press
    }

    /// Get other flags
    pub fn other_flags(&self) -> u8 {
        self.flags.other
    }

    /// Set other flags
    pub fn set_other_flags(&mut self, flags: u8) {
        self.flags.other = flags & 0x3F; // Only 6 bits
    }

    /// Get G-sensor data
    pub fn g_sensor_data(&self) -> Option<u32> {
        if self.has_g_sensor() {
            Some(self.g_sensor)
        } else {
            None
        }
    }
}

impl UPPFrame {
    /// Create a new UPP frame
    pub fn new(header: UPPFrameHeader, data: Vec<u8>) -> Self {
        Self { header, data }
    }

    /// Get the total frame size
    pub fn total_size(&self) -> usize {
        mem::size_of::<UPPFrameHeader>() + self.data.len()
    }

    /// Get the frame ID
    pub fn frame_id(&self) -> u8 {
        self.header.frame_id
    }

    /// Get the camera number
    pub fn camera_number(&self) -> u8 {
        self.header.camera_number
    }

    /// Check if button was pressed
    pub fn button_pressed(&self) -> bool {
        self.header.button_pressed()
    }

    /// Get G-sensor data if available
    pub fn g_sensor_data(&self) -> Option<u32> {
        if self.header.has_g_sensor() {
            Some(self.header.g_sensor)
        } else {
            None
        }
    }
}

impl Default for UPPUsbFrame {
    fn default() -> Self {
        Self {
            magic: super::UPP_USB_MAGIC,
            cid: super::UPP_CAMID_7,
            length: 0,
        }
    }
}

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

    #[test]
    fn test_upp_usb_frame_creation() {
        let frame = UPPUsbFrame::new(7, 1024);
        let magic = frame.magic;
        let cid = frame.cid;
        let length = frame.length;
        assert_eq!(magic, super::super::UPP_USB_MAGIC);
        assert_eq!(cid, 7);
        assert_eq!(length, 1024);
        assert!(frame.is_valid());
    }

    #[test]
    fn test_upp_usb_frame_validation() {
        let mut frame = UPPUsbFrame::new(7, 1024);
        assert!(frame.is_valid());

        frame.magic = 0x1234;
        assert!(!frame.is_valid());
    }

    #[test]
    fn test_upp_frame_header_creation() {
        let header = UPPFrameHeader::new(1, 0, true, false, 12345);
        assert_eq!(header.frame_id, 1);
        assert_eq!(header.camera_number, 0);
        assert!(header.has_g_sensor());
        assert!(!header.button_pressed());
        assert_eq!(header.g_sensor_data(), Some(12345));
    }

    #[test]
    fn test_upp_frame_header_flags() {
        let mut header = UPPFrameHeader::default();
        assert!(!header.has_g_sensor());
        assert!(!header.button_pressed());

        header.flags.has_g = true;
        header.flags.button_press = true;
        assert!(header.has_g_sensor());
        assert!(header.button_pressed());
    }

    #[test]
    fn test_upp_frame_creation() {
        let header = UPPFrameHeader::new(1, 0, false, false, 0);
        let data = vec![1, 2, 3, 4, 5];
        let frame = UPPFrame::new(header, data.clone());

        assert_eq!(frame.frame_id(), 1);
        assert_eq!(frame.camera_number(), 0);
        assert_eq!(frame.data, data);
        assert_eq!(frame.total_size(), mem::size_of::<UPPFrameHeader>() + 5);
    }

    #[test]
    fn test_upp_frame_defaults() {
        let frame = UPPFrame::default();
        assert_eq!(frame.frame_id(), 0);
        assert_eq!(frame.camera_number(), 0);
        assert!(frame.data.is_empty());
        assert!(!frame.button_pressed());
        assert!(frame.g_sensor_data().is_none());
    }

    #[test]
    fn test_upp_flags_other_bits() {
        let mut header = UPPFrameHeader::default();
        header.set_other_flags(0xFF);
        assert_eq!(header.other_flags(), 0x3F); // Only 6 bits should be set
    }

    #[test]
    fn test_memory_layout() {
        // Ensure packed structs have correct sizes
        assert_eq!(mem::size_of::<UPPUsbFrame>(), 5);
        // UPPFrameHeader: frame_id(1) + camera_number(1) + flags(3) + g_sensor(4) = 9 bytes
        assert_eq!(mem::size_of::<UPPFrameHeader>(), 9);
    }
}