//! Módulo de conexión - Gestión de conexiones P2P
//!
//! Maneja conexiones TLS, keepalives, y multiplexación de mensajes.

const std = @import("std");
const identity = @import("identity.zig");
const protocol = @import("protocol.zig");
const discovery = @import("discovery.zig");

pub const DeviceId = identity.DeviceId;

/// Configuración del nodo P2P
pub const Config = struct {
    /// Nombre del dispositivo
    device_name: []const u8 = "zcatp2p",

    /// Puerto para conexiones entrantes
    listen_port: u16 = 22000,

    /// Habilitar discovery local
    local_discovery: bool = true,

    /// Servidores de discovery global
    global_discovery_servers: []const []const u8 = &.{},

    /// Servidores STUN
    stun_servers: []const []const u8 = &.{
        "stun.l.google.com:19302",
        "stun.syncthing.net:3478",
    },

    /// Servidores relay
    relay_servers: []const []const u8 = &.{},

    /// Directorio de datos
    data_dir: []const u8,

    /// Compresión habilitada
    compression: bool = true,

    /// Callbacks
    on_device_discovered: ?*const fn (DeviceId, []const []const u8) void = null,
    on_message_received: ?*const fn (*Connection, protocol.Message) void = null,
    on_connection_state_changed: ?*const fn (*Connection, ConnectionState) void = null,
};

/// Estado de conexión
pub const ConnectionState = enum {
    connecting,
    connected,
    disconnecting,
    disconnected,
    @"error",
};

/// Tipo de NAT detectado
pub const NatType = enum {
    unknown,
    none,
    full_cone,
    restricted,
    port_restricted,
    symmetric,
    blocked,
};

/// Errores del módulo
pub const Error = error{
    AlreadyInitialized,
    NotInitialized,
    InvalidDeviceId,
    ConnectionFailed,
    ConnectionTimeout,
    ConnectionClosed,
    PeerNotFound,
    CertificateError,
    TlsError,
    ProtocolError,
    CompressionError,
    OutOfMemory,
    IoError,
    InvalidConfig,
};

/// Información de un peer
pub const PeerInfo = struct {
    device_id: DeviceId,
    device_name: []const u8,
    client_name: []const u8,
    client_version: []const u8,
    addresses: []const []const u8,
    connected_at: i64,
    is_local: bool,
    bytes_sent: u64,
    bytes_received: u64,
};

/// Conexión con un peer
pub const Connection = struct {
    allocator: std.mem.Allocator,
    device_id: DeviceId,
    state: ConnectionState,
    peer_info: ?PeerInfo,
    socket: ?std.posix.socket_t,
    next_message_id: u32,
    bytes_sent: u64,
    bytes_received: u64,
    connected_at: i64,

    pub fn init(allocator: std.mem.Allocator, device_id: DeviceId) Connection {
        return .{
            .allocator = allocator,
            .device_id = device_id,
            .state = .disconnected,
            .peer_info = null,
            .socket = null,
            .next_message_id = 1,
            .bytes_sent = 0,
            .bytes_received = 0,
            .connected_at = 0,
        };
    }

    pub fn deinit(self: *Connection) void {
        if (self.socket) |sock| {
            std.posix.close(sock);
        }
    }

    pub fn getDeviceId(self: *Connection) DeviceId {
        return self.device_id;
    }

    pub fn getState(self: *Connection) ConnectionState {
        return self.state;
    }

    pub fn getPeerInfo(self: *Connection) ?PeerInfo {
        return self.peer_info;
    }

    pub fn isConnected(self: *Connection) bool {
        return self.state == .connected;
    }

    /// Envía datos al peer
    pub fn send(
        self: *Connection,
        content_type: []const u8,
        data: []const u8,
    ) Error!u32 {
        if (self.state != .connected) return Error.ConnectionClosed;

        const msg_id = self.next_message_id;
        self.next_message_id += 1;

        const msg = protocol.DataMessage{
            .message_id = msg_id,
            .content_type = content_type,
            .data = data,
        };

        const encoded = msg.encode(self.allocator) catch return Error.OutOfMemory;
        defer self.allocator.free(encoded);

        // TODO: Enviar por socket con TLS
        self.bytes_sent += encoded.len;

        return msg_id;
    }

    /// Cierra la conexión
    pub fn close(self: *Connection) void {
        self.closeWithReason("closed by user");
    }

    /// Cierra la conexión con motivo
    pub fn closeWithReason(self: *Connection, reason: []const u8) void {
        _ = reason;
        if (self.socket) |sock| {
            std.posix.close(sock);
            self.socket = null;
        }
        self.state = .disconnected;
    }

    /// Espera hasta que la conexión esté establecida
    pub fn waitConnected(self: *Connection, timeout_ms: u32) Error!void {
        _ = timeout_ms;
        if (self.state == .connected) return;
        if (self.state == .@"error" or self.state == .disconnected) {
            return Error.ConnectionFailed;
        }
        // TODO: Implementar espera con timeout
        return Error.ConnectionTimeout;
    }
};

/// Instancia principal P2P
pub const P2P = struct {
    allocator: std.mem.Allocator,
    config: Config,
    device_id: DeviceId,
    connections: std.AutoHashMapUnmanaged(DeviceId, *Connection),
    discovery_manager: discovery.DiscoveryManager,
    listener_socket: ?std.posix.socket_t,
    external_address: ?[]const u8,
    nat_type: NatType,

    pub fn init(allocator: std.mem.Allocator, config: Config) Error!*P2P {
        const self = allocator.create(P2P) catch return Error.OutOfMemory;
        errdefer allocator.destroy(self);

        // Generar o cargar Device ID
        // TODO: Implementar carga de certificado
        var device_id: DeviceId = undefined;
        std.crypto.random.bytes(&device_id);

        self.* = .{
            .allocator = allocator,
            .config = config,
            .device_id = device_id,
            .connections = .{},
            .discovery_manager = discovery.DiscoveryManager.init(allocator, device_id),
            .listener_socket = null,
            .external_address = null,
            .nat_type = .unknown,
        };

        return self;
    }

    pub fn deinit(self: *P2P) void {
        // Cerrar todas las conexiones
        var iter = self.connections.iterator();
        while (iter.next()) |entry| {
            entry.value_ptr.*.deinit();
            self.allocator.destroy(entry.value_ptr.*);
        }
        self.connections.deinit(self.allocator);

        // Cerrar listener
        if (self.listener_socket) |sock| {
            std.posix.close(sock);
        }

        // Limpiar discovery
        self.discovery_manager.deinit();

        // Limpiar external address
        if (self.external_address) |addr| {
            self.allocator.free(addr);
        }

        self.allocator.destroy(self);
    }

    /// Obtiene el Device ID local
    pub fn getDeviceId(self: *P2P) DeviceId {
        return self.device_id;
    }

    /// Obtiene el Device ID como string
    pub fn getDeviceIdString(self: *P2P, buf: []u8) []const u8 {
        return identity.deviceIdToString(self.device_id, buf);
    }

    /// Parsea un Device ID desde string
    pub fn parseDeviceId(str: []const u8) Error!DeviceId {
        return identity.stringToDeviceId(str) catch Error.InvalidDeviceId;
    }

    /// Compara dos Device IDs
    pub fn deviceIdEquals(a: DeviceId, b: DeviceId) bool {
        return identity.deviceIdEquals(a, b);
    }

    /// Obtiene el Short ID
    pub fn getShortId(device_id: DeviceId) identity.ShortId {
        return identity.getShortId(device_id);
    }

    /// Conecta a un dispositivo
    pub fn connect(self: *P2P, device_id: DeviceId) Error!*Connection {
        // Verificar si ya existe conexión
        if (self.connections.get(device_id)) |conn| {
            if (conn.isConnected()) return conn;
        }

        // Crear nueva conexión
        const conn = self.allocator.create(Connection) catch return Error.OutOfMemory;
        conn.* = Connection.init(self.allocator, device_id);
        conn.state = .connecting;

        self.connections.put(self.allocator, device_id, conn) catch {
            self.allocator.destroy(conn);
            return Error.OutOfMemory;
        };

        // Buscar direcciones del peer
        const addresses = self.discovery_manager.lookup(device_id) catch null;
        if (addresses == null) {
            conn.state = .@"error";
            return Error.PeerNotFound;
        }

        // TODO: Intentar conectar a las direcciones

        return conn;
    }

    /// Desconecta de un peer
    pub fn disconnect(self: *P2P, device_id: DeviceId) void {
        if (self.connections.get(device_id)) |conn| {
            conn.close();
        }
    }

    /// Obtiene una conexión existente
    pub fn getConnection(self: *P2P, device_id: DeviceId) ?*Connection {
        return self.connections.get(device_id);
    }

    /// Número de conexiones activas
    pub fn connectionCount(self: *P2P) usize {
        var count: usize = 0;
        var iter = self.connections.iterator();
        while (iter.next()) |entry| {
            if (entry.value_ptr.*.isConnected()) count += 1;
        }
        return count;
    }

    /// Obtiene la IP externa
    pub fn getExternalAddress(self: *P2P) ?[]const u8 {
        return self.external_address;
    }

    /// Obtiene el tipo de NAT
    pub fn getNatType(self: *P2P) NatType {
        return self.nat_type;
    }
};

// =============================================================================
// Tests
// =============================================================================

test "p2p init/deinit" {
    const allocator = std.testing.allocator;

    const p2p = try P2P.init(allocator, .{
        .data_dir = "/tmp/zcatp2p-test",
    });
    defer p2p.deinit();

    try std.testing.expect(p2p.connectionCount() == 0);
}

test "connection init" {
    const allocator = std.testing.allocator;
    const device_id = [_]u8{0xab} ** 32;

    var conn = Connection.init(allocator, device_id);
    defer conn.deinit();

    try std.testing.expect(conn.state == .disconnected);
    try std.testing.expect(!conn.isConnected());
}