package notify

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

const defaultPeerAttachReplayCapacity = 4096

type PeerAttachChannelBindingRole string

const (
	PeerAttachChannelBindingRoleClient PeerAttachChannelBindingRole = "client"
	PeerAttachChannelBindingRoleServer PeerAttachChannelBindingRole = "server"
)

type PeerAttachChannelBindingContext struct {
	Role   PeerAttachChannelBindingRole
	PeerID string
	Conn   net.Conn
}

type PeerAttachChannelBindingProvider func(PeerAttachChannelBindingContext) ([]byte, error)

type PeerAttachSecurityConfig struct {
	RequireExplicitAuth   bool
	RequireChannelBinding bool
	ReplayWindow          time.Duration
	ReplayCapacity        int
	ChannelBinding        PeerAttachChannelBindingProvider
}

type peerAttachSecurityState struct {
	requireExplicitAuth   bool
	requireChannelBinding bool
	replayWindow          time.Duration
	replayCapacity        int
	channelBinding        PeerAttachChannelBindingProvider
}

var errPeerAttachChannelBindingProviderNil = errors.New("peer attach channel binding provider is nil")

func DefaultPeerAttachSecurityConfig() PeerAttachSecurityConfig {
	return PeerAttachSecurityConfig{
		ReplayWindow:   peerAttachReplayTTL,
		ReplayCapacity: defaultPeerAttachReplayCapacity,
	}
}

func normalizePeerAttachSecurityConfig(cfg PeerAttachSecurityConfig) (peerAttachSecurityState, error) {
	if cfg.ReplayWindow <= 0 {
		cfg.ReplayWindow = peerAttachReplayTTL
	}
	if cfg.ReplayCapacity <= 0 {
		cfg.ReplayCapacity = defaultPeerAttachReplayCapacity
	}
	if cfg.RequireChannelBinding {
		cfg.RequireExplicitAuth = true
		if cfg.ChannelBinding == nil {
			return peerAttachSecurityState{}, errPeerAttachChannelBindingProviderNil
		}
	}
	return peerAttachSecurityState{
		requireExplicitAuth:   cfg.RequireExplicitAuth,
		requireChannelBinding: cfg.RequireChannelBinding,
		replayWindow:          cfg.ReplayWindow,
		replayCapacity:        cfg.ReplayCapacity,
		channelBinding:        cfg.ChannelBinding,
	}, nil
}

func peerAttachSecurityConfigFromState(state *peerAttachSecurityState) PeerAttachSecurityConfig {
	if state == nil {
		return DefaultPeerAttachSecurityConfig()
	}
	return PeerAttachSecurityConfig{
		RequireExplicitAuth:   state.requireExplicitAuth,
		RequireChannelBinding: state.requireChannelBinding,
		ReplayWindow:          state.replayWindow,
		ReplayCapacity:        state.replayCapacity,
		ChannelBinding:        state.channelBinding,
	}
}

func defaultPeerAttachSecurityState() *peerAttachSecurityState {
	cfg, _ := normalizePeerAttachSecurityConfig(DefaultPeerAttachSecurityConfig())
	return &cfg
}

func (c *ClientCommon) peerAttachSecuritySnapshot() peerAttachSecurityState {
	if c == nil {
		cfg, _ := normalizePeerAttachSecurityConfig(DefaultPeerAttachSecurityConfig())
		return cfg
	}
	if state := c.peerAttachSecurity.Load(); state != nil {
		return *state
	}
	cfg, _ := normalizePeerAttachSecurityConfig(DefaultPeerAttachSecurityConfig())
	return cfg
}

func (s *ServerCommon) peerAttachSecuritySnapshot() peerAttachSecurityState {
	if s == nil {
		cfg, _ := normalizePeerAttachSecurityConfig(DefaultPeerAttachSecurityConfig())
		return cfg
	}
	if state := s.peerAttachSecurity.Load(); state != nil {
		return *state
	}
	cfg, _ := normalizePeerAttachSecurityConfig(DefaultPeerAttachSecurityConfig())
	return cfg
}

func (c *ClientCommon) SetPeerAttachSecurityConfig(cfg PeerAttachSecurityConfig) error {
	state, err := normalizePeerAttachSecurityConfig(cfg)
	if err != nil {
		return err
	}
	c.peerAttachSecurity.Store(&state)
	return nil
}

func (c *ClientCommon) PeerAttachSecurityConfig() PeerAttachSecurityConfig {
	return peerAttachSecurityConfigFromState(c.peerAttachSecurity.Load())
}

func (s *ServerCommon) SetPeerAttachSecurityConfig(cfg PeerAttachSecurityConfig) error {
	state, err := normalizePeerAttachSecurityConfig(cfg)
	if err != nil {
		return err
	}
	s.peerAttachSecurity.Store(&state)
	return nil
}

func (s *ServerCommon) PeerAttachSecurityConfig() PeerAttachSecurityConfig {
	return peerAttachSecurityConfigFromState(s.peerAttachSecurity.Load())
}