package stario

import (
	"context"
	"errors"
	"sync"
	"time"
)

var ErrDeadlineExceeded = errors.New("deadline exceeded")
var ErrQueueDataFormat = errors.New("data format error")
var ErrQueueUnsupportedVersion = errors.New("unsupported frame version")
var ErrQueueUnsupportedFlags = errors.New("unsupported frame flags")
var ErrQueueMessageTooLarge = errors.New("message too large")
var ErrQueueFrameHandlerNil = errors.New("frame handler is nil")
var ErrQueueConnKeyInvalid = errors.New("queue conn key must be comparable")
var ErrQueueConnKeyNil = errors.New("queue conn key must not be nil")

const (
	queMagicSize      = 8
	queHeaderSize     = 14
	queVersionV1      = 1
	queSupportedFlags = 0
)

// 识别头
var queMagic = []byte{11, 27, 19, 96, 12, 25, 02, 20}

// MsgQueue 为基本的信息单位。
type MsgQueue struct {
	// Deprecated: frame-level IDs are no longer emitted by StarQueue v2 framing.
	ID uint16

	Msg  []byte
	Conn interface{}
}

// FrameView exposes a parsed payload without forcing StarQueue to clone it.
//
// The payload is only valid during the ParseMessageView callback. Callers must
// copy it if they need to keep it after the callback returns.
type FrameView struct {
	Payload []byte
	Conn    interface{}
}

// StarQueue 为流数据中的消息队列分发。
type StarQueue struct {
	maxLength uint32
	msgPool   chan MsgQueue
	states    sync.Map
	ctx       context.Context
	cancel    context.CancelFunc
	duration  time.Duration
	sendMu    sync.RWMutex
	stopOnce  sync.Once

	// Deprecated: new code should keep StarQueue focused on framing only.
	Encode bool
	// Deprecated: new code should keep StarQueue focused on framing only.
	EncodeFunc func([]byte) []byte
	// Deprecated: new code should keep StarQueue focused on framing only.
	DecodeFunc func([]byte) []byte
}

type queHeader struct {
	Length  uint32
	Version uint8
	Flags   uint8
}

type queConnState struct {
	mu  sync.Mutex
	buf []byte
}

func NewQueueCtx(ctx context.Context, count int64, maxMsgLength uint32) *StarQueue {
	if count < 0 {
		panic("stario: negative queue count")
	}
	q := &StarQueue{
		maxLength: maxMsgLength,
		msgPool:   make(chan MsgQueue, count),
	}
	if ctx == nil {
		q.ctx, q.cancel = context.WithCancel(context.Background())
	} else {
		q.ctx, q.cancel = context.WithCancel(ctx)
	}
	context.AfterFunc(q.ctx, q.shutdown)
	return q
}

func NewQueueWithCount(count int64) *StarQueue {
	return NewQueueCtx(nil, count, 0)
}

// NewQueue 建立一个新消息队列。
func NewQueue() *StarQueue {
	return NewQueueWithCount(32)
}