package centrifuge

import (
	"encoding/json"
	"fmt"
	"strings"
	"sync"
)

// Disconnect allows to configure how client will be disconnected from server.
// The important note that Disconnect serialized to JSON must be less than 127 bytes
// due to WebSocket protocol limitations (because at moment we send Disconnect inside
// reason field of WebSocket close handshake).
// Note that due to performance reasons we cache Disconnect text representation
// for Close Frame on first send to client so changing field values inside existing
// Disconnect instance won't be reflected in WebSocket/Sockjs Close frames.
type Disconnect struct {
	// Code is disconnect code.
	Code uint32 `json:"code,omitempty"`
	// Reason is a short description of disconnect.
	Reason string `json:"reason"`
	// Reconnect gives client an advice to reconnect after disconnect or not.
	Reconnect bool `json:"reconnect"`

	closeTextOnce   sync.Once
	cachedCloseText string
}

var _ error = (*Disconnect)(nil)

// String representation.
func (d *Disconnect) String() string {
	return fmt.Sprintf("code: %d, reason: %s, reconnect: %t", d.Code, d.Reason, d.Reconnect)
}

// Error representation.
func (d *Disconnect) Error() string {
	return fmt.Sprintf("disconnected: code: %d, reason: %s, reconnect: %t", d.Code, d.Reason, d.Reconnect)
}

// CloseText allows to build disconnect advice sent inside Close frame.
// At moment we don't encode Code here to not duplicate information
// since it is sent separately as Code of WebSocket/SockJS Close Frame.
func (d *Disconnect) CloseText() string {
	d.closeTextOnce.Do(func() {
		buf := strings.Builder{}
		buf.WriteString(`{"reason":`)
		reason, _ := json.Marshal(d.Reason)
		buf.Write(reason)
		buf.WriteString(`,"reconnect":`)
		if d.Reconnect {
			buf.WriteString("true")
		} else {
			buf.WriteString("false")
		}
		buf.WriteString(`}`)
		d.cachedCloseText = buf.String()
	})
	return d.cachedCloseText
}

// Some predefined disconnect structures used by library internally. Though
// it's always possible to create Disconnect with any field values on the fly.
// Library users supposed to use codes in range 4000-4999 for custom disconnects.
var (
	// DisconnectNormal is clean disconnect when client cleanly closed connection.
	DisconnectNormal = &Disconnect{
		Code:      3000,
		Reason:    "normal",
		Reconnect: true,
	}
	// DisconnectShutdown sent when node is going to shut down.
	DisconnectShutdown = &Disconnect{
		Code:      3001,
		Reason:    "shutdown",
		Reconnect: true,
	}
	// DisconnectInvalidToken sent when client came with invalid token.
	DisconnectInvalidToken = &Disconnect{
		Code:      3002,
		Reason:    "invalid token",
		Reconnect: false,
	}
	// DisconnectBadRequest sent when client uses malformed protocol
	// frames or wrong order of commands.
	DisconnectBadRequest = &Disconnect{
		Code:      3003,
		Reason:    "bad request",
		Reconnect: false,
	}
	// DisconnectServerError sent when internal error occurred on server.
	DisconnectServerError = &Disconnect{
		Code:      3004,
		Reason:    "internal server error",
		Reconnect: true,
	}
	// DisconnectExpired sent when client connection expired.
	DisconnectExpired = &Disconnect{
		Code:      3005,
		Reason:    "expired",
		Reconnect: true,
	}
	// DisconnectSubExpired sent when client subscription expired.
	DisconnectSubExpired = &Disconnect{
		Code:      3006,
		Reason:    "subscription expired",
		Reconnect: true,
	}
	// DisconnectStale sent to close connection that did not become
	// authenticated in configured interval after dialing.
	DisconnectStale = &Disconnect{
		Code:      3007,
		Reason:    "stale",
		Reconnect: false,
	}
	// DisconnectSlow sent when client can't read messages fast enough.
	DisconnectSlow = &Disconnect{
		Code:      3008,
		Reason:    "slow",
		Reconnect: true,
	}
	// DisconnectWriteError sent when an error occurred while writing to
	// client connection.
	DisconnectWriteError = &Disconnect{
		Code:      3009,
		Reason:    "write error",
		Reconnect: true,
	}
	// DisconnectInsufficientState sent when server detects wrong client
	// position in channel Publication stream. Disconnect allows client
	// to restore missed publications on reconnect.
	DisconnectInsufficientState = &Disconnect{
		Code:      3010,
		Reason:    "insufficient state",
		Reconnect: true,
	}
	// DisconnectForceReconnect sent when server disconnects connection.
	DisconnectForceReconnect = &Disconnect{
		Code:      3011,
		Reason:    "force reconnect",
		Reconnect: true,
	}
	// DisconnectForceNoReconnect sent when server disconnects connection
	// and asks it to not reconnect again.
	DisconnectForceNoReconnect = &Disconnect{
		Code:      3012,
		Reason:    "force disconnect",
		Reconnect: false,
	}
	// DisconnectConnectionLimit can be sent when client connection exceeds a
	// configured connection limit (per user ID or due to other rule).
	DisconnectConnectionLimit = &Disconnect{
		Code:      3013,
		Reason:    "connection limit",
		Reconnect: false,
	}
)