use serde::{Deserialize, Serialize};
use std::collections::HashMap;

use super::metadata::ObjectManifest;

/// All inter-node cluster messages, serialized with bincode over QUIC streams.
///
/// Each message type gets its own bidirectional QUIC stream.
/// For shard data transfers, the header is sent first (bincode),
/// then raw shard bytes follow on the same stream.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ClusterRequest {
    // ============================
    // Shard operations
    // ============================

    /// Write a shard to a specific drive on the target node.
    /// Shard data follows after this header on the same stream.
    ShardWrite(ShardWriteRequest),

    /// Read a shard from the target node.
    ShardRead(ShardReadRequest),

    /// Delete a shard from the target node.
    ShardDelete(ShardDeleteRequest),

    /// Check if a shard exists and get its metadata.
    ShardHead(ShardHeadRequest),

    // ============================
    // Manifest operations
    // ============================

    /// Store an object manifest on the target node.
    ManifestWrite(ManifestWriteRequest),

    /// Retrieve an object manifest from the target node.
    ManifestRead(ManifestReadRequest),

    /// Delete an object manifest from the target node.
    ManifestDelete(ManifestDeleteRequest),

    /// List all manifests for a bucket on the target node.
    ManifestList(ManifestListRequest),

    // ============================
    // Cluster management
    // ============================

    /// Periodic heartbeat.
    Heartbeat(HeartbeatMessage),

    /// Request to join the cluster.
    JoinRequest(JoinRequestMessage),

    /// Synchronize cluster topology.
    TopologySync(TopologySyncMessage),

    // ============================
    // Healing
    // ============================

    /// Request a shard to be reconstructed and placed on a target drive.
    HealRequest(HealRequestMessage),
}

/// Responses to cluster requests.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ClusterResponse {
    // Shard ops
    ShardWriteAck(ShardWriteAck),
    ShardReadResponse(ShardReadResponse),
    ShardDeleteAck(ShardDeleteAck),
    ShardHeadResponse(ShardHeadResponse),

    // Manifest ops
    ManifestWriteAck(ManifestWriteAck),
    ManifestReadResponse(ManifestReadResponse),
    ManifestDeleteAck(ManifestDeleteAck),
    ManifestListResponse(ManifestListResponse),

    // Cluster mgmt
    HeartbeatAck(HeartbeatAckMessage),
    JoinResponse(JoinResponseMessage),
    TopologySyncAck(TopologySyncAckMessage),

    // Healing
    HealResponse(HealResponseMessage),

    // Error
    Error(ErrorResponse),
}

// ============================
// Shard operation messages
// ============================

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardWriteRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
    pub chunk_index: u32,
    pub shard_index: u32,
    pub shard_data_length: u64,
    pub checksum: u32, // crc32c of shard data
    pub object_metadata: HashMap<String, String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardWriteAck {
    pub request_id: String,
    pub success: bool,
    pub error: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardReadRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
    pub chunk_index: u32,
    pub shard_index: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardReadResponse {
    pub request_id: String,
    pub found: bool,
    pub shard_data_length: u64,
    pub checksum: u32,
    // Shard data follows on the stream after this header
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardDeleteRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
    pub chunk_index: u32,
    pub shard_index: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardDeleteAck {
    pub request_id: String,
    pub success: bool,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardHeadRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
    pub chunk_index: u32,
    pub shard_index: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShardHeadResponse {
    pub request_id: String,
    pub found: bool,
    pub data_size: u64,
    pub checksum: u32,
}

// ============================
// Manifest operation messages
// ============================

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestWriteRequest {
    pub request_id: String,
    pub manifest: ObjectManifest,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestWriteAck {
    pub request_id: String,
    pub success: bool,
    pub error: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestReadRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestReadResponse {
    pub request_id: String,
    pub found: bool,
    pub manifest: Option<ObjectManifest>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestDeleteRequest {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestDeleteAck {
    pub request_id: String,
    pub success: bool,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestListRequest {
    pub request_id: String,
    pub bucket: String,
    pub prefix: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ManifestListResponse {
    pub request_id: String,
    pub manifests: Vec<ObjectManifest>,
}

// ============================
// Cluster management messages
// ============================

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DriveStateInfo {
    pub drive_index: u32,
    pub status: String, // "online", "degraded", "offline", "healing"
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HeartbeatMessage {
    pub node_id: String,
    pub timestamp: String,
    pub drive_states: Vec<DriveStateInfo>,
    pub topology_version: u64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HeartbeatAckMessage {
    pub node_id: String,
    pub timestamp: String,
    pub topology_version: u64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeInfo {
    pub node_id: String,
    pub quic_addr: String,
    pub s3_addr: String,
    pub drive_count: u32,
    pub status: String,
    pub version: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JoinRequestMessage {
    pub node_info: NodeInfo,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ClusterTopology {
    pub version: u64,
    pub cluster_id: String,
    pub nodes: Vec<NodeInfo>,
    pub erasure_sets: Vec<ErasureSetInfo>,
    pub data_shards: usize,
    pub parity_shards: usize,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ErasureSetInfo {
    pub set_id: u32,
    pub drives: Vec<DriveLocationInfo>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DriveLocationInfo {
    pub node_id: String,
    pub drive_index: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JoinResponseMessage {
    pub accepted: bool,
    pub topology: Option<ClusterTopology>,
    pub error: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TopologySyncMessage {
    pub topology: ClusterTopology,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TopologySyncAckMessage {
    pub accepted: bool,
    pub current_version: u64,
}

// ============================
// Healing messages
// ============================

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealRequestMessage {
    pub request_id: String,
    pub bucket: String,
    pub key: String,
    pub chunk_index: u32,
    pub shard_index: u32,
    pub target_node_id: String,
    pub target_drive_index: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealResponseMessage {
    pub request_id: String,
    pub success: bool,
    pub error: Option<String>,
}

// ============================
// Error response
// ============================

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ErrorResponse {
    pub request_id: String,
    pub code: String,
    pub message: String,
}

// ============================
// Wire format helpers
// ============================

/// Serialize a request to bincode bytes with a 4-byte length prefix.
pub fn encode_request(req: &ClusterRequest) -> anyhow::Result<Vec<u8>> {
    let payload = bincode::serialize(req)?;
    let mut buf = Vec::with_capacity(4 + payload.len());
    buf.extend_from_slice(&(payload.len() as u32).to_le_bytes());
    buf.extend_from_slice(&payload);
    Ok(buf)
}

/// Serialize a response to bincode bytes with a 4-byte length prefix.
pub fn encode_response(resp: &ClusterResponse) -> anyhow::Result<Vec<u8>> {
    let payload = bincode::serialize(resp)?;
    let mut buf = Vec::with_capacity(4 + payload.len());
    buf.extend_from_slice(&(payload.len() as u32).to_le_bytes());
    buf.extend_from_slice(&payload);
    Ok(buf)
}

/// Read a length-prefixed bincode message from raw bytes.
/// Returns (decoded message, bytes consumed).
pub fn decode_request(data: &[u8]) -> anyhow::Result<(ClusterRequest, usize)> {
    if data.len() < 4 {
        anyhow::bail!("Not enough data for length prefix");
    }
    let len = u32::from_le_bytes([data[0], data[1], data[2], data[3]]) as usize;
    if data.len() < 4 + len {
        anyhow::bail!("Not enough data for message body");
    }
    let msg: ClusterRequest = bincode::deserialize(&data[4..4 + len])?;
    Ok((msg, 4 + len))
}

/// Read a length-prefixed bincode response from raw bytes.
pub fn decode_response(data: &[u8]) -> anyhow::Result<(ClusterResponse, usize)> {
    if data.len() < 4 {
        anyhow::bail!("Not enough data for length prefix");
    }
    let len = u32::from_le_bytes([data[0], data[1], data[2], data[3]]) as usize;
    if data.len() < 4 + len {
        anyhow::bail!("Not enough data for message body");
    }
    let msg: ClusterResponse = bincode::deserialize(&data[4..4 + len])?;
    Ok((msg, 4 + len))
}