package notify

import (
	"errors"
	"fmt"
	"net"
	"time"
)

const defaultSignalAckTimeout = time.Second

const defaultSignalSendRetry = 3

type signalReliabilityConfig struct {
	Enabled           bool
	EnableConfigured  bool
	AckTimeout        time.Duration
	SendRetry         int
	ReceiveCacheLimit int
}

type SignalReliabilityOptions struct {
	Enabled           bool
	AckTimeout        time.Duration
	SendRetry         int
	ReceiveCacheLimit int
}

var (
	errSignalReliabilityClientNil         = errors.New("signal reliability client is nil")
	errSignalReliabilityServerNil         = errors.New("signal reliability server is nil")
	errSignalReliabilityUnsupportedClient = errors.New("signal reliability client type is unsupported")
	errSignalReliabilityUnsupportedServer = errors.New("signal reliability server type is unsupported")
)

func defaultSignalReliabilityConfig() signalReliabilityConfig {
	return signalReliabilityConfig{
		Enabled:           false,
		EnableConfigured:  false,
		AckTimeout:        defaultSignalAckTimeout,
		SendRetry:         defaultSignalSendRetry,
		ReceiveCacheLimit: defaultReceivedSignalCacheLimit,
	}
}

func DefaultSignalReliabilityOptions() SignalReliabilityOptions {
	cfg := defaultSignalReliabilityConfig()
	return SignalReliabilityOptions{
		Enabled:           true,
		AckTimeout:        cfg.AckTimeout,
		SendRetry:         cfg.SendRetry,
		ReceiveCacheLimit: cfg.ReceiveCacheLimit,
	}
}

func normalizeSignalReliabilityConfig(cfg signalReliabilityConfig) signalReliabilityConfig {
	defaults := defaultSignalReliabilityConfig()
	if cfg.AckTimeout <= 0 {
		cfg.AckTimeout = defaults.AckTimeout
	}
	if cfg.SendRetry <= 0 {
		cfg.SendRetry = defaults.SendRetry
	}
	if cfg.ReceiveCacheLimit <= 0 {
		cfg.ReceiveCacheLimit = defaults.ReceiveCacheLimit
	}
	return cfg
}

func signalReliabilityConfigFromOptions(opts *SignalReliabilityOptions) signalReliabilityConfig {
	cfg := defaultSignalReliabilityConfig()
	if opts == nil {
		cfg.Enabled = true
		cfg.EnableConfigured = true
		return cfg
	}
	return signalReliabilityConfig{
		Enabled:           opts.Enabled,
		EnableConfigured:  true,
		AckTimeout:        opts.AckTimeout,
		SendRetry:         opts.SendRetry,
		ReceiveCacheLimit: opts.ReceiveCacheLimit,
	}
}

type signalReliabilityConfigurer interface {
	setSignalReliabilityConfig(signalReliabilityConfig)
}

func UseSignalReliabilityClient(c Client, opts *SignalReliabilityOptions) error {
	if c == nil {
		return errSignalReliabilityClientNil
	}
	configurer, ok := any(c).(signalReliabilityConfigurer)
	if !ok {
		return errSignalReliabilityUnsupportedClient
	}
	configurer.setSignalReliabilityConfig(signalReliabilityConfigFromOptions(opts))
	return nil
}

func UseSignalReliabilityServer(s Server, opts *SignalReliabilityOptions) error {
	if s == nil {
		return errSignalReliabilityServerNil
	}
	configurer, ok := any(s).(signalReliabilityConfigurer)
	if !ok {
		return errSignalReliabilityUnsupportedServer
	}
	configurer.setSignalReliabilityConfig(signalReliabilityConfigFromOptions(opts))
	return nil
}

func (c *ClientCommon) getSignalReliabilityConfig() signalReliabilityConfig {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.signalReliableCfg = normalizeSignalReliabilityConfig(c.signalReliableCfg)
	return c.signalReliableCfg
}

func (s *ServerCommon) getSignalReliabilityConfig() signalReliabilityConfig {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.signalReliableCfg = normalizeSignalReliabilityConfig(s.signalReliableCfg)
	return s.signalReliableCfg
}

func (c *ClientCommon) setSignalReliabilityConfig(cfg signalReliabilityConfig) {
	cfg = normalizeSignalReliabilityConfig(cfg)
	c.mu.Lock()
	cfg.EnableConfigured = true
	c.signalReliableCfg = cfg
	state := c.logicalSession
	c.mu.Unlock()
	if state != nil {
		state.applySignalReliabilityConfig(cfg)
	}
}

func (s *ServerCommon) setSignalReliabilityConfig(cfg signalReliabilityConfig) {
	cfg = normalizeSignalReliabilityConfig(cfg)
	s.mu.Lock()
	cfg.EnableConfigured = true
	s.signalReliableCfg = cfg
	state := s.logicalSession
	s.mu.Unlock()
	if state != nil {
		state.applySignalReliabilityConfig(cfg)
	}
}

func (c *ClientCommon) applySignalReliabilityTransportDefault(enabled bool) {
	cfg := c.getSignalReliabilityConfig()
	if cfg.EnableConfigured {
		return
	}
	cfg.Enabled = enabled
	c.mu.Lock()
	c.signalReliableCfg = cfg
	c.mu.Unlock()
}

func (s *ServerCommon) applySignalReliabilityTransportDefault(enabled bool) {
	cfg := s.getSignalReliabilityConfig()
	if cfg.EnableConfigured {
		return
	}
	cfg.Enabled = enabled
	s.mu.Lock()
	s.signalReliableCfg = cfg
	s.mu.Unlock()
}

func requiresSignalReplyWait(msg TransferMsg) bool {
	return msg.Type == MSG_SYNC_ASK || msg.Type == MSG_KEY_CHANGE || msg.Type == MSG_SYS_WAIT
}

func signalCanUseTransportAck(msg TransferMsg) bool {
	return msg.ID != 0
}

func retryReliableSignalSend(cfg signalReliabilityConfig, send func(signalReliabilityConfig) error) error {
	return retryReliableSignalSendWithAttempt(cfg, func(cfg signalReliabilityConfig, _ int) error {
		return send(cfg)
	})
}

func retryReliableSignalSendWithAttempt(cfg signalReliabilityConfig, send func(signalReliabilityConfig, int) error) error {
	cfg = normalizeSignalReliabilityConfig(cfg)
	var lastErr error
	for attempt := 1; attempt <= cfg.SendRetry; attempt++ {
		lastErr = send(cfg, attempt)
		if lastErr == nil {
			return nil
		}
	}
	return lastErr
}

func sendSignalWithAck(scope string, signalID uint64, timeout time.Duration, pool *signalAckPool, send func() error) error {
	return sendSignalWithAckTracked(nil, scope, signalID, timeout, pool, send)
}

func sendSignalWithAckTracked(state *signalReliabilityState, scope string, signalID uint64, timeout time.Duration, pool *signalAckPool, send func() error) error {
	if state != nil {
		state.incAckWait()
	}
	wait := pool.prepare(scope, signalID)
	if err := send(); err != nil {
		wait.cancel()
		return err
	}
	err := pool.waitPrepared(wait, timeout)
	if state == nil {
		return err
	}
	if err == nil {
		state.incAckDeliver()
		return nil
	}
	if errors.Is(err, errSignalAckTimeout) {
		state.incAckTimeout()
		return err
	}
	if errors.Is(err, errSignalAckCanceled) {
		state.incAckCanceled()
		return err
	}
	return err
}

func (c *ClientCommon) sendSignalEnvelopeMaybeReliable(env Envelope, msg TransferMsg) error {
	state := c.getSignalReliabilityState()
	state.incSignalSend()
	cfg := c.getSignalReliabilityConfig()
	if !cfg.Enabled || !signalCanUseTransportAck(msg) {
		return c.sendEnvelope(env)
	}
	state.incReliableSend()
	return retryReliableSignalSendWithAttempt(cfg, func(cfg signalReliabilityConfig, attempt int) error {
		if attempt > 1 {
			state.incRetry()
		}
		return sendSignalWithAckTracked(state, clientFileScope(), env.ID, cfg.AckTimeout, c.getSignalAckPool(), func() error {
			return c.sendEnvelope(env)
		})
	})
}

func (s *ServerCommon) sendSignalEnvelopeMaybeReliable(logical *LogicalConn, env Envelope, msg TransferMsg) error {
	if logical == nil {
		return s.sendSignalEnvelopeMaybeReliableTransport(nil, env, msg)
	}
	return s.sendSignalEnvelopeMaybeReliableTransport(s.resolveOutboundTransport(logical), env, msg)
}

func (s *ServerCommon) sendSignalEnvelopeMaybeReliableTransport(transport *TransportConn, env Envelope, msg TransferMsg) error {
	state := s.getSignalReliabilityState()
	state.incSignalSend()
	cfg := s.getSignalReliabilityConfig()
	if !cfg.Enabled || !signalCanUseTransportAck(msg) {
		return s.sendEnvelopeTransport(transport, env)
	}
	state.incReliableSend()
	scope := serverTransportScopeForTransport(transport)
	return retryReliableSignalSendWithAttempt(cfg, func(cfg signalReliabilityConfig, attempt int) error {
		if attempt > 1 {
			state.incRetry()
		}
		return sendSignalWithAckTracked(state, scope, env.ID, cfg.AckTimeout, s.getSignalAckPool(), func() error {
			return s.sendEnvelopeTransport(transport, env)
		})
	})
}

func (c *ClientCommon) sendSignalAck(signalID uint64) error {
	return c.sendEnvelope(newSignalAckEnvelope(signalID))
}

func (s *ServerCommon) sendSignalAck(logical *LogicalConn, signalID uint64) error {
	if logical == nil {
		return s.sendSignalAckTransport(nil, signalID)
	}
	return s.sendSignalAckTransport(s.resolveOutboundTransport(logical), signalID)
}

func (s *ServerCommon) sendSignalAckTransport(transport *TransportConn, signalID uint64) error {
	return s.sendEnvelopeTransport(transport, newSignalAckEnvelope(signalID))
}

func (s *ServerCommon) sendSignalAckInbound(logical *LogicalConn, transport *TransportConn, conn net.Conn, signalID uint64) error {
	if conn == nil {
		return s.sendSignalAckTransport(transport, signalID)
	}
	return s.sendEnvelopeInboundTransport(logical, transport, conn, newSignalAckEnvelope(signalID))
}

func (c *ClientCommon) handleSignalAckEnvelope(env Envelope) bool {
	return c.getSignalAckPool().deliver(clientFileScope(), env.ID)
}

func (s *ServerCommon) handleSignalAckEnvelope(logical *LogicalConn, env Envelope) bool {
	if logical == nil {
		return s.handleSignalAckEnvelopeTransport(nil, env)
	}
	return s.handleSignalAckEnvelopeTransport(s.resolveOutboundTransport(logical), env)
}

func (s *ServerCommon) handleSignalAckEnvelopeTransport(transport *TransportConn, env Envelope) bool {
	return s.getSignalAckPool().deliverAny(serverTransportDeliveryScopesForTransport(transport), env.ID)
}

func (c *ClientCommon) handleReceivedSignalReliability(msg TransferMsg) bool {
	cfg := c.getSignalReliabilityConfig()
	if !cfg.Enabled || !signalCanUseTransportAck(msg) {
		return false
	}
	state := c.getSignalReliabilityState()
	duplicate := c.getReceivedSignalCache().seenOrRemember(clientFileScope(), msg.ID)
	if duplicate {
		state.incDuplicateRecv()
	}
	state.incAckSend()
	if err := c.sendSignalAck(msg.ID); err != nil {
		state.incAckSendError()
		if c.showError || c.debugMode {
			fmt.Println("client send signal ack error", err)
		}
	}
	return duplicate
}

func (s *ServerCommon) handleReceivedSignalReliability(logical *LogicalConn, msg TransferMsg) bool {
	return s.handleReceivedSignalReliabilityTransport(logical, s.resolveOutboundTransport(logical), nil, msg)
}

func (s *ServerCommon) handleReceivedSignalReliabilityTransport(logical *LogicalConn, transport *TransportConn, conn net.Conn, msg TransferMsg) bool {
	cfg := s.getSignalReliabilityConfig()
	if !cfg.Enabled || !signalCanUseTransportAck(msg) {
		return false
	}
	state := s.getSignalReliabilityState()
	scope := serverFileScope(logical)
	duplicate := s.getReceivedSignalCache().seenOrRemember(scope, msg.ID)
	if duplicate {
		state.incDuplicateRecv()
	}
	state.incAckSend()
	if err := s.sendSignalAckInbound(logical, transport, conn, msg.ID); err != nil {
		state.incAckSendError()
		if s.showError || s.debugMode {
			fmt.Println("server send signal ack error", err)
		}
	}
	return duplicate
}