//! Unified error type for imks.
//!
//! Consolidates all submodule-specific error enums into a single `ImksError`.
//! Public APIs return `ImksResult<T>`, private code may still use local enums
//! for internal dispatch and convert via `From` / `.map_err()` when crossing
//! module boundaries.

use std::string::FromUtf8Error;

use thiserror::Error;

/// Unified error enum for the entire imks crate.
#[derive(Debug, Error)]
pub enum ImksError {
    // Protocol layer (engine)
    #[error("invalid engine packet type: {0}")]
    InvalidEnginePacketType(u8),
    #[error("invalid engine packet type char: {0}")]
    InvalidEnginePacketTypeChar(char),
    #[error("empty engine packet")]
    EmptyEnginePacket,
    #[error("invalid base64: {0}")]
    InvalidBase64(#[from] base64::DecodeError),
    #[error("invalid utf8 in packet: {0}")]
    InvalidPacketUtf8(#[from] FromUtf8Error),
    #[error("engine serialization error: {0}")]
    EngineSerialization(String),

    // Transport upgrade
    #[error("session not found for upgrade")]
    UpgradeSessionNotFound,
    #[error("session already closed, cannot upgrade")]
    UpgradeSessionClosed,
    #[error("invalid session state for upgrade")]
    UpgradeInvalidState,

    // Socket.IO layer
    #[error("invalid socket packet type: {0}")]
    InvalidSocketPacketType(u8),
    #[error("invalid socket packet type char: {0}")]
    InvalidSocketPacketTypeChar(char),
    #[error("empty socket packet")]
    EmptySocketPacket,
    #[error("invalid socket packet format: {0}")]
    InvalidSocketPacketFormat(String),
    #[error("missing namespace in socket packet")]
    MissingNamespace,
    #[error("invalid attachment count in binary event")]
    InvalidAttachmentCount,

    // Socket namespace
    #[error("namespace error: {0}")]
    Namespace(String),
    #[error("socket not found: {0}")]
    SocketNotFound(String),
    #[error("failed to send packet to socket: channel full")]
    SocketSendFull,

    // Adapter layer
    #[error("adapter redis error: {0}")]
    AdapterRedis(String),
    #[error("adapter nats error: {0}")]
    AdapterNats(String),
    #[error("adapter message bus error: {0}")]
    AdapterMessageBus(String),
    #[error("adapter serialization error: {0}")]
    AdapterSerialization(String),
    #[error("adapter room error: {0}")]
    AdapterRoom(String),

    // Message bus
    #[error("message bus connection closed")]
    MessageBusConnectionClosed,
    #[error("message bus channel not found: {0}")]
    MessageBusChannelNotFound(String),

    // Session store
    #[error("session not found: {0}")]
    SessionNotFound(String),
    #[error("session expired: {0}")]
    SessionExpired(String),
    #[error("session store redis error: {0}")]
    SessionRedis(String),
    #[error("session serialization error: {0}")]
    SessionSerialization(String),

    // Database
    #[error("database error: {0}")]
    Database(#[from] sqlx::Error),

    // gRPC
    #[error("gRPC error: {0}")]
    GrpcStatus(#[from] tonic::Status),
    #[error("gRPC transport error: {0}")]
    GrpcTransport(#[from] tonic::transport::Error),

    // Serialization
    #[error("JSON error: {0}")]
    Json(#[from] serde_json::Error),

    // Transport
    #[error("webtransport error: {0}")]
    WebTransport(String),
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    // Auth
    #[error("auth error: {0}")]
    Auth(String),
    #[error("token expired")]
    TokenExpired,

    // General
    #[error("not found: {0}")]
    NotFound(String),
    #[error("invalid input: {0}")]
    InvalidInput(String),
    #[error("internal error: {0}")]
    Internal(String),
}

/// Convenience alias used across all public APIs.
pub type ImksResult<T> = Result<T, ImksError>;

// Conversions from submodule error types (for gradual migration).

impl From<crate::engine::packet::PacketError> for ImksError {
    fn from(e: crate::engine::packet::PacketError) -> Self {
        use crate::engine::packet::PacketError::*;
        match e {
            InvalidType(v) => ImksError::InvalidEnginePacketType(v),
            InvalidTypeChar(c) => ImksError::InvalidEnginePacketTypeChar(c),
            Empty => ImksError::EmptyEnginePacket,
            InvalidBase64(e) => ImksError::InvalidBase64(e),
            InvalidUtf8(e) => ImksError::InvalidPacketUtf8(e),
            Serialization(s) => ImksError::EngineSerialization(s),
        }
    }
}

impl From<crate::engine::upgrade::UpgradeError> for ImksError {
    fn from(e: crate::engine::upgrade::UpgradeError) -> Self {
        use crate::engine::upgrade::UpgradeError::*;
        match e {
            SessionNotFound => ImksError::UpgradeSessionNotFound,
            SessionClosed => ImksError::UpgradeSessionClosed,
            InvalidState => ImksError::UpgradeInvalidState,
        }
    }
}

impl From<crate::socket::packet::PacketError> for ImksError {
    fn from(e: crate::socket::packet::PacketError) -> Self {
        use crate::socket::packet::PacketError::*;
        match e {
            InvalidType(v) => ImksError::InvalidSocketPacketType(v),
            InvalidTypeChar(c) => ImksError::InvalidSocketPacketTypeChar(c),
            Empty => ImksError::EmptySocketPacket,
            InvalidFormat(s) => ImksError::InvalidSocketPacketFormat(s),
            Json(e) => ImksError::Json(e),
            MissingNamespace => ImksError::MissingNamespace,
            InvalidAttachmentCount => ImksError::InvalidAttachmentCount,
        }
    }
}

impl From<crate::socket::adapter::AdapterError> for ImksError {
    fn from(e: crate::socket::adapter::AdapterError) -> Self {
        use crate::socket::adapter::AdapterError::*;
        match e {
            Redis(s) => ImksError::AdapterRedis(s),
            Nats(s) => ImksError::AdapterNats(s),
            MessageBus(s) => ImksError::AdapterMessageBus(s),
            Serialization(s) => ImksError::AdapterSerialization(s),
            Room(s) => ImksError::AdapterRoom(s),
        }
    }
}

impl From<crate::socket::message_bus::MessageBusError> for ImksError {
    fn from(e: crate::socket::message_bus::MessageBusError) -> Self {
        use crate::socket::message_bus::MessageBusError::*;
        match e {
            Redis(s) => ImksError::AdapterRedis(s),
            Nats(s) => ImksError::AdapterNats(s),
            ConnectionClosed => ImksError::MessageBusConnectionClosed,
            ChannelNotFound(s) => ImksError::MessageBusChannelNotFound(s),
            Serialization(s) => ImksError::AdapterSerialization(s),
        }
    }
}

impl From<crate::socket::session_store::SessionError> for ImksError {
    fn from(e: crate::socket::session_store::SessionError) -> Self {
        use crate::socket::session_store::SessionError::*;
        match e {
            Redis(s) => ImksError::SessionRedis(s),
            NotFound(s) => ImksError::SessionNotFound(s),
            Serialization(s) => ImksError::SessionSerialization(s),
            Expired(s) => ImksError::SessionExpired(s),
        }
    }
}

impl From<tokio::sync::mpsc::error::TrySendError<crate::socket::packet::Packet>> for ImksError {
    fn from(_: tokio::sync::mpsc::error::TrySendError<crate::socket::packet::Packet>) -> Self {
        ImksError::SocketSendFull
    }
}

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

    #[test]
    fn test_imks_error_display() {
        let err = ImksError::NotFound("message 01909abc".into());
        assert_eq!(err.to_string(), "not found: message 01909abc");
    }

    #[test]
    fn test_imks_error_from_base64() {
        let b64_err = base64::DecodeError::InvalidByte(0, b'!');
        let err: ImksError = b64_err.into();
        assert!(matches!(err, ImksError::InvalidBase64(_)));
    }

    #[test]
    fn test_imks_error_from_sqlx() {
        // sqlx::Error doesn't impl PartialEq, so just check the variant
        let db_err = sqlx::Error::PoolClosed;
        let err: ImksError = db_err.into();
        assert!(matches!(err, ImksError::Database(_)));
    }

    #[test]
    fn test_imks_error_from_serde_json() {
        let json_err = serde_json::from_str::<serde_json::Value>("not json").unwrap_err();
        let err: ImksError = json_err.into();
        assert!(matches!(err, ImksError::Json(_)));
    }

    #[test]
    #[allow(clippy::unnecessary_literal_unwrap)]
    fn test_imks_result_ok() {
        let result: ImksResult<i32> = Ok(42);
        assert_eq!(result.unwrap(), 42);
    }

    #[test]
    fn test_imks_result_err() {
        let result: ImksResult<i32> = Err(ImksError::TokenExpired);
        assert!(result.is_err());
    }
}