use serde::{Deserialize, Serialize};

pub type UserId = u32; // Unique identifier for a user within a room
pub type StreamId = u16; // Typically mapped to User + Media Source

#[derive(Debug, Serialize, Deserialize, Clone, Copy, PartialEq, Eq, Hash)]
#[repr(u8)]
pub enum MediaType {
    Audio = 0,
    Video = 1,
    Screen = 2,
    Command = 3, // For handshake/keepalive
    Unknown = 255,
}

/// UDP Packet Header (fixed size binary struct)
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct PacketHeader {
    pub version: u8, // Protocol version (v1)
    pub media_type: MediaType,
    pub user_id: UserId, // Identifies the source user (was stream_id)
    pub sequence: u32, // User-defined sequence number (for reordering/loss)
    pub timestamp: u32, // RTP-like timestamp
    pub fragment_index: u16, // If packet is fragmented (0 if not)
    pub fragment_count: u16, // Total fragments (1 if not)
    pub flags: u8, // Bitmask: 0x01 = Keyframe, etc.
}

pub const FLAG_KEYFRAME: u8 = 0x01;

/// Signaling Messages (WebSocket - JSON)
#[derive(Debug, Serialize, Deserialize, Clone)]
#[serde(tag = "type", content = "data")]
pub enum ControlMsg {
    /// Client -> Server: Request to join a room
    Join {
        room_code: String,
        display_name: String,
    },
    /// Server -> Client: Join success
    Joined {
        self_id: UserId,
        room_code: String,
        peers: Vec<PeerInfo>,
    },
    /// Server -> Client: New peer joined
    PeerJoined {
        user_id: UserId,
        display_name: String,
    },
    /// Server -> Client: Peer left
    PeerLeft {
        user_id: UserId,
    },
    /// Client -> Server: Update stream status (e.g. camera on/off)
    UpdateStream {
        user_id: UserId,
        stream_id: StreamId,
        active: bool,
        media_type: MediaType,
    },
    /// Client <-> Server: Chat message
    ChatMessage {
        user_id: UserId,
        display_name: String,
        message: String,
        timestamp: u64,
    },
    /// General Error
    Error {
        message: String,
    },
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct PeerInfo {
    pub user_id: UserId,
    pub display_name: String,
    // Could include active streams etc.
}