use std::io::{self, Read, Write};
use std::net::TcpStream;

pub const CTDB_MAGIC: u32 = 0x43544442;
pub const CTDB_VERSION: u32 = 1;
pub const CTDB_HEADER_SIZE: usize = 24;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u32)]
pub enum CtdbCommand {
    Connect = 1,
    Disconnect = 2,
    Ping = 3,
    Pong = 4,
    GetDb = 10,
    Fetch = 11,
    Store = 12,
    Delete = 13,
    Keys = 14,
    SetNodeMask = 20,
    GetNodeMask = 21,
    NodeStatus = 22,
    TakeIp = 30,
    ReleaseIp = 31,
    Monitor = 40,
    Recovery = 50,
    RecoveryDone = 51,
    Unknown = 0xFFFF,
}

impl CtdbCommand {
    pub fn from_u32(v: u32) -> Self {
        match v {
            1 => CtdbCommand::Connect,
            2 => CtdbCommand::Disconnect,
            3 => CtdbCommand::Ping,
            4 => CtdbCommand::Pong,
            10 => CtdbCommand::GetDb,
            11 => CtdbCommand::Fetch,
            12 => CtdbCommand::Store,
            13 => CtdbCommand::Delete,
            14 => CtdbCommand::Keys,
            20 => CtdbCommand::SetNodeMask,
            21 => CtdbCommand::GetNodeMask,
            22 => CtdbCommand::NodeStatus,
            30 => CtdbCommand::TakeIp,
            31 => CtdbCommand::ReleaseIp,
            40 => CtdbCommand::Monitor,
            50 => CtdbCommand::Recovery,
            51 => CtdbCommand::RecoveryDone,
            _ => CtdbCommand::Unknown,
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CtdbStatus {
    Success = 0,
    Error = 1,
    NotFound = 2,
    Exists = 3,
    Corrupt = 4,
    Timeout = 5,
    NotActive = 6,
}

impl CtdbStatus {
    pub fn from_u32(v: u32) -> Self {
        match v {
            0 => CtdbStatus::Success,
            2 => CtdbStatus::NotFound,
            3 => CtdbStatus::Exists,
            4 => CtdbStatus::Corrupt,
            5 => CtdbStatus::Timeout,
            6 => CtdbStatus::NotActive,
            _ => CtdbStatus::Error,
        }
    }
}

#[derive(Debug, Clone)]
pub struct CtdbHeader {
    pub magic: u32,
    pub version: u32,
    pub command: u32,
    pub status: u32,
    pub length: u64,
}

impl CtdbHeader {
    pub fn new(command: CtdbCommand, status: CtdbStatus, length: u64) -> Self {
        Self {
            magic: CTDB_MAGIC,
            version: CTDB_VERSION,
            command: command as u32,
            status: status as u32,
            length,
        }
    }

    pub fn to_bytes(&self) -> Vec<u8> {
        let mut buf = Vec::with_capacity(CTDB_HEADER_SIZE);
        buf.extend_from_slice(&self.magic.to_le_bytes());
        buf.extend_from_slice(&self.version.to_le_bytes());
        buf.extend_from_slice(&self.command.to_le_bytes());
        buf.extend_from_slice(&self.status.to_le_bytes());
        buf.extend_from_slice(&self.length.to_le_bytes());
        buf
    }

    pub fn from_bytes(buf: &[u8]) -> Result<Self, CtdbProtoError> {
        if buf.len() < CTDB_HEADER_SIZE {
            return Err(CtdbProtoError::HeaderTooShort);
        }
        let magic = u32::from_le_bytes(buf[0..4].try_into().unwrap());
        let version = u32::from_le_bytes(buf[4..8].try_into().unwrap());
        let command = u32::from_le_bytes(buf[8..12].try_into().unwrap());
        let status = u32::from_le_bytes(buf[12..16].try_into().unwrap());
        let length = u64::from_le_bytes(buf[16..24].try_into().unwrap());
        Ok(Self {
            magic,
            version,
            command,
            status,
            length,
        })
    }

    pub fn is_valid(&self) -> bool {
        self.magic == CTDB_MAGIC && self.version == CTDB_VERSION
    }
}

#[derive(Debug, Clone)]
pub struct CtdbMessage {
    pub header: CtdbHeader,
    pub payload: Vec<u8>,
}

impl CtdbMessage {
    pub fn new(command: CtdbCommand, status: CtdbStatus, payload: Vec<u8>) -> Self {
        let length = payload.len() as u64;
        Self {
            header: CtdbHeader::new(command, status, length),
            payload,
        }
    }

    pub fn to_bytes(&self) -> Vec<u8> {
        let mut buf = self.header.to_bytes();
        buf.extend_from_slice(&self.payload);
        buf
    }

    pub fn from_bytes(buf: &[u8]) -> Result<Self, CtdbProtoError> {
        let header = CtdbHeader::from_bytes(buf)?;
        if !header.is_valid() {
            return Err(CtdbProtoError::InvalidMagic);
        }
        let payload = if buf.len() > CTDB_HEADER_SIZE {
            buf[CTDB_HEADER_SIZE..].to_vec()
        } else {
            Vec::new()
        };
        Ok(Self { header, payload })
    }

    pub fn command(&self) -> CtdbCommand {
        CtdbCommand::from_u32(self.header.command)
    }

    pub fn status(&self) -> CtdbStatus {
        CtdbStatus::from_u32(self.header.status)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CtdbProtoError {
    HeaderTooShort,
    InvalidMagic,
    IoError,
    InvalidPayload,
}

impl std::fmt::Display for CtdbProtoError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            CtdbProtoError::HeaderTooShort => write!(f, "header too short"),
            CtdbProtoError::InvalidMagic => write!(f, "invalid magic number"),
            CtdbProtoError::IoError => write!(f, "I/O error"),
            CtdbProtoError::InvalidPayload => write!(f, "invalid payload"),
        }
    }
}

impl std::error::Error for CtdbProtoError {}
impl From<io::Error> for CtdbProtoError {
    fn from(_: io::Error) -> Self {
        CtdbProtoError::IoError
    }
}

pub mod payload {
    use super::CtdbProtoError;

    pub fn encode_kv(key: &[u8], value: &[u8]) -> Vec<u8> {
        let mut buf = Vec::new();
        buf.extend_from_slice(&(key.len() as u32).to_le_bytes());
        buf.extend_from_slice(key);
        buf.extend_from_slice(&(value.len() as u32).to_le_bytes());
        buf.extend_from_slice(value);
        buf
    }

    pub fn decode_kv(payload: &[u8]) -> Result<(Vec<u8>, Vec<u8>), CtdbProtoError> {
        if payload.len() < 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let key_len = u32::from_le_bytes(payload[0..4].try_into().unwrap()) as usize;
        if payload.len() < 4 + key_len + 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let key = payload[4..4 + key_len].to_vec();
        let val_len_offset = 4 + key_len;
        let val_len = u32::from_le_bytes(
            payload[val_len_offset..val_len_offset + 4].try_into().unwrap(),
        ) as usize;
        let val_start = val_len_offset + 4;
        if payload.len() < val_start + val_len {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let value = payload[val_start..val_start + val_len].to_vec();
        Ok((key, value))
    }

    pub fn encode_key(key: &[u8]) -> Vec<u8> {
        let mut buf = Vec::new();
        buf.extend_from_slice(&(key.len() as u32).to_le_bytes());
        buf.extend_from_slice(key);
        buf
    }

    pub fn decode_key(payload: &[u8]) -> Result<Vec<u8>, CtdbProtoError> {
        if payload.len() < 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let key_len = u32::from_le_bytes(payload[0..4].try_into().unwrap()) as usize;
        if payload.len() < 4 + key_len {
            return Err(CtdbProtoError::InvalidPayload);
        }
        Ok(payload[4..4 + key_len].to_vec())
    }

    pub fn encode_node_id(id: u32) -> Vec<u8> {
        id.to_le_bytes().to_vec()
    }

    pub fn decode_node_id(payload: &[u8]) -> Result<u32, CtdbProtoError> {
        if payload.len() < 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        Ok(u32::from_le_bytes(payload[0..4].try_into().unwrap()))
    }

    pub fn encode_nodemask(active: &[u32]) -> Vec<u8> {
        let mut buf = Vec::new();
        buf.extend_from_slice(&(active.len() as u32).to_le_bytes());
        for &id in active {
            buf.extend_from_slice(&id.to_le_bytes());
        }
        buf
    }

    pub fn decode_nodemask(payload: &[u8]) -> Result<Vec<u32>, CtdbProtoError> {
        if payload.len() < 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let count = u32::from_le_bytes(payload[0..4].try_into().unwrap()) as usize;
        let mut ids = Vec::with_capacity(count);
        for i in 0..count {
            let offset = 4 + i * 4;
            if payload.len() < offset + 4 {
                return Err(CtdbProtoError::InvalidPayload);
            }
            ids.push(u32::from_le_bytes(payload[offset..offset + 4].try_into().unwrap()));
        }
        Ok(ids)
    }

    pub fn encode_ip(ip: &str, interface: &str) -> Vec<u8> {
        let ip_bytes = ip.as_bytes();
        let if_bytes = interface.as_bytes();
        let mut buf = Vec::new();
        buf.extend_from_slice(&(ip_bytes.len() as u32).to_le_bytes());
        buf.extend_from_slice(ip_bytes);
        buf.extend_from_slice(&(if_bytes.len() as u32).to_le_bytes());
        buf.extend_from_slice(if_bytes);
        buf
    }

    pub fn decode_ip(payload: &[u8]) -> Result<(String, String), CtdbProtoError> {
        if payload.len() < 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let ip_len = u32::from_le_bytes(payload[0..4].try_into().unwrap()) as usize;
        if payload.len() < 4 + ip_len + 4 {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let ip = String::from_utf8_lossy(&payload[4..4 + ip_len]).to_string();
        let if_offset = 4 + ip_len;
        let if_len = u32::from_le_bytes(
            payload[if_offset..if_offset + 4].try_into().unwrap(),
        ) as usize;
        let if_start = if_offset + 4;
        if payload.len() < if_start + if_len {
            return Err(CtdbProtoError::InvalidPayload);
        }
        let interface = String::from_utf8_lossy(&payload[if_start..if_start + if_len]).to_string();
        Ok((ip, interface))
    }
}

pub struct CtdbConnection {
    stream: TcpStream,
}

impl CtdbConnection {
    pub fn new(stream: TcpStream) -> Self {
        Self { stream }
    }

    pub fn connect(addr: &str) -> Result<Self, CtdbProtoError> {
        let stream = TcpStream::connect(addr)?;
        Ok(Self { stream })
    }

    pub fn send_message(&mut self, msg: &CtdbMessage) -> Result<(), CtdbProtoError> {
        let bytes = msg.to_bytes();
        self.stream.write_all(&bytes)?;
        Ok(())
    }

    pub fn recv_message(&mut self) -> Result<CtdbMessage, CtdbProtoError> {
        let mut header_buf = [0u8; CTDB_HEADER_SIZE];
        self.stream.read_exact(&mut header_buf)?;
        let header = CtdbHeader::from_bytes(&header_buf)?;
        if !header.is_valid() {
            return Err(CtdbProtoError::InvalidMagic);
        }
        let payload_len = header.length as usize;
        let mut payload = vec![0u8; payload_len];
        if payload_len > 0 {
            self.stream.read_exact(&mut payload)?;
        }
        Ok(CtdbMessage { header, payload })
    }

    pub fn ping(&mut self) -> Result<(), CtdbProtoError> {
        let msg = CtdbMessage::new(CtdbCommand::Ping, CtdbStatus::Success, vec![]);
        self.send_message(&msg)?;
        let resp = self.recv_message()?;
        if resp.command() == CtdbCommand::Pong && resp.status() == CtdbStatus::Success {
            Ok(())
        } else {
            Err(CtdbProtoError::InvalidPayload)
        }
    }

    pub fn store(&mut self, key: &[u8], value: &[u8]) -> Result<bool, CtdbProtoError> {
        let payload = payload::encode_kv(key, value);
        let msg = CtdbMessage::new(CtdbCommand::Store, CtdbStatus::Success, payload);
        self.send_message(&msg)?;
        let resp = self.recv_message()?;
        Ok(resp.status() == CtdbStatus::Success)
    }

    pub fn fetch(&mut self, key: &[u8]) -> Result<Vec<u8>, CtdbProtoError> {
        let payload = payload::encode_key(key);
        let msg = CtdbMessage::new(CtdbCommand::Fetch, CtdbStatus::Success, payload);
        self.send_message(&msg)?;
        let resp = self.recv_message()?;
        if resp.status() == CtdbStatus::Success {
            Ok(resp.payload)
        } else {
            Err(CtdbProtoError::InvalidPayload)
        }
    }

    pub fn delete(&mut self, key: &[u8]) -> Result<bool, CtdbProtoError> {
        let payload = payload::encode_key(key);
        let msg = CtdbMessage::new(CtdbCommand::Delete, CtdbStatus::Success, payload);
        self.send_message(&msg)?;
        let resp = self.recv_message()?;
        Ok(resp.status() == CtdbStatus::Success)
    }
}

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

    #[test]
    fn test_header_roundtrip() {
        let header = CtdbHeader::new(CtdbCommand::Ping, CtdbStatus::Success, 42);
        let bytes = header.to_bytes();
        let restored = CtdbHeader::from_bytes(&bytes).unwrap();
        assert_eq!(restored.magic, CTDB_MAGIC);
        assert_eq!(restored.version, CTDB_VERSION);
        assert_eq!(restored.command, CtdbCommand::Ping as u32);
        assert_eq!(restored.status, CtdbStatus::Success as u32);
        assert_eq!(restored.length, 42);
        assert!(restored.is_valid());
    }

    #[test]
    fn test_message_roundtrip() {
        let msg = CtdbMessage::new(
            CtdbCommand::Store,
            CtdbStatus::Success,
            b"test_payload".to_vec(),
        );
        let bytes = msg.to_bytes();
        let restored = CtdbMessage::from_bytes(&bytes).unwrap();
        assert_eq!(restored.command(), CtdbCommand::Store);
        assert_eq!(restored.payload, b"test_payload");
    }

    #[test]
    fn test_command_from_u32() {
        assert_eq!(CtdbCommand::from_u32(1), CtdbCommand::Connect);
        assert_eq!(CtdbCommand::from_u32(3), CtdbCommand::Ping);
        assert_eq!(CtdbCommand::from_u32(0xFFFF), CtdbCommand::Unknown);
        assert_eq!(CtdbCommand::from_u32(999), CtdbCommand::Unknown);
    }

    #[test]
    fn test_status_from_u32() {
        assert_eq!(CtdbStatus::from_u32(0), CtdbStatus::Success);
        assert_eq!(CtdbStatus::from_u32(2), CtdbStatus::NotFound);
        assert_eq!(CtdbStatus::from_u32(99), CtdbStatus::Error);
    }

    #[test]
    fn test_payload_encode_decode_kv() {
        let (key, val) = (b"mykey", b"myvalue");
        let encoded = payload::encode_kv(key, val);
        let (k, v) = payload::decode_kv(&encoded).unwrap();
        assert_eq!(k, key);
        assert_eq!(v, val);
    }

    #[test]
    fn test_payload_encode_decode_key() {
        let key = b"test_key";
        let encoded = payload::encode_key(key);
        let decoded = payload::decode_key(&encoded).unwrap();
        assert_eq!(decoded, key);
    }

    #[test]
    fn test_payload_node_id() {
        let encoded = payload::encode_node_id(42);
        let decoded = payload::decode_node_id(&encoded).unwrap();
        assert_eq!(decoded, 42);
    }

    #[test]
    fn test_payload_nodemask() {
        let ids = vec![0u32, 1, 2, 3];
        let encoded = payload::encode_nodemask(&ids);
        let decoded = payload::decode_nodemask(&encoded).unwrap();
        assert_eq!(decoded, ids);
    }

    #[test]
    fn test_payload_ip() {
        let encoded = payload::encode_ip("192.168.1.100", "eth0");
        let (ip, iface) = payload::decode_ip(&encoded).unwrap();
        assert_eq!(ip, "192.168.1.100");
        assert_eq!(iface, "eth0");
    }

    #[test]
    fn test_invalid_magic() {
        let mut bad_header = CtdbHeader::new(CtdbCommand::Ping, CtdbStatus::Success, 0);
        bad_header.magic = 0xDEADBEEF;
        assert!(!bad_header.is_valid());
    }

    #[test]
    fn test_empty_message() {
        let msg = CtdbMessage::new(CtdbCommand::Connect, CtdbStatus::Success, vec![]);
        let bytes = msg.to_bytes();
        let restored = CtdbMessage::from_bytes(&bytes).unwrap();
        assert!(restored.payload.is_empty());
        assert_eq!(restored.header.length, 0);
    }

    #[test]
    fn test_header_too_short() {
        let result = CtdbHeader::from_bytes(&[0u8; 10]);
        assert!(result.is_err());
    }

    #[test]
    fn test_large_payload() {
        let large = vec![0xABu8; 65000];
        let msg = CtdbMessage::new(CtdbCommand::Fetch, CtdbStatus::Success, large.clone());
        let bytes = msg.to_bytes();
        let restored = CtdbMessage::from_bytes(&bytes).unwrap();
        assert_eq!(restored.payload.len(), 65000);
        assert_eq!(restored.payload, large);
    }
}