// ============================================================
// base.ts — 交易所适配器抽象基类
// ============================================================
// 所有交易所适配器（Binance / OKX / Bybit ...）继承此类，
// 复用指数退避重连、连接状态管理、限流等通用逻辑。
//
// 子类只需实现：
//   - connect()        — 建立 WebSocket/REST 连接
//   - disconnect()     — 断开连接并清理资源
//   - subscribeTicker() / subscribeTrade() / subscribeOrderbook()
//   - fetchKlines()    — REST 历史 K 线补拉
//   - fetchMarkets()   — 交易对元数据拉取
// ============================================================

import { Subject, type Observable } from "rxjs";
import { logger } from "../utils/logger";
import type {
    MarketDataFeed,
    Ticker,
    Trade,
    OrderBook,
    Kline,
    KlineInterval,
    MarketInfo,
    ConnectionState,
    AdapterConfig,
} from "./types";
import { DEFAULT_ADAPTER_CONFIG } from "./types";

// ============================================================
// 工具：异步 sleep
// ============================================================

/** 返回一个在 ms 毫秒后 resolve 的 Promise */
function sleep(ms: number): Promise<void> {
    return new Promise((resolve) => setTimeout(resolve, ms));
}

// ============================================================
// BaseExchangeAdapter
// ============================================================

export abstract class BaseExchangeAdapter implements MarketDataFeed {
    /** 交易所标识（子类必须覆盖） */
    abstract readonly exchange: string;

    /** 适配器配置（可在子类构造函数中覆盖默认值） */
    protected readonly config: AdapterConfig;

    /** 当前连接状态 */
    protected _connectionState: ConnectionState = "disconnected";

    /** 当前重连尝试次数（成功连接后重置） */
    protected reconnectAttempt = 0;

    /** Subject 清理注册表 —— disconnect 时统一 complete */
    protected activeSubjects = new Set<Subject<unknown>>();

    // ============================================================
    // 构造函数
    // ============================================================

    constructor(config: Partial<AdapterConfig> = {}) {
        this.config = { ...DEFAULT_ADAPTER_CONFIG, ...config };
    }

    // ============================================================
    // 连接状态（只读暴露）
    // ============================================================

    get connectionState(): ConnectionState {
        return this._connectionState;
    }

    /** 更新连接状态并记录日志 */
    protected setConnectionState(state: ConnectionState): void {
        const prev = this._connectionState;
        this._connectionState = state;
        if (prev !== state) {
            logger.info(
                { exchange: this.exchange, from: prev, to: state },
                `[${this.exchange}] connection state: ${prev} → ${state}`,
            );
        }
    }

    // ============================================================
    // 指数退避重连（所有子类复用）
    // ============================================================

    /**
     * 执行指数退避重连。
     *
     * 延迟公式：delay = baseDelay × 2^min(attempt, 5)
     *   - attempt=0: 3s
     *   - attempt=1: 6s
     *   - attempt=2: 12s
     *   - attempt=5: 96s（之后不再翻倍）
     *
     * 超过 maxReconnectAttempts 后抛出错误。
     *
     * @throws 达到最大重试次数后抛出
     */
    protected async reconnect(): Promise<void> {
        const { reconnectBaseDelayMs: baseDelay, maxReconnectAttempts } = this.config;

        if (this.reconnectAttempt >= maxReconnectAttempts) {
            this.setConnectionState("error");
            throw new Error(
                `[${this.exchange}] 重连失败：已达最大重试次数 (${maxReconnectAttempts})`,
            );
        }

        const cappedAttempt = Math.min(this.reconnectAttempt, 5);
        const delay = baseDelay * Math.pow(2, cappedAttempt);

        logger.warn(
            {
                exchange: this.exchange,
                attempt: this.reconnectAttempt + 1,
                maxAttempts: maxReconnectAttempts,
                delayMs: delay,
            },
            `[${this.exchange}] WebSocket 重连中...`,
        );

        await sleep(delay);

        this.reconnectAttempt++;
        this.setConnectionState("connecting");
        await this.connect();
    }

    /** 成功连接后重置重连计数器 */
    protected resetReconnectAttempts(): void {
        if (this.reconnectAttempt > 0) {
            logger.info(
                { exchange: this.exchange, attempts: this.reconnectAttempt },
                `[${this.exchange}] 重连成功，计数器重置`,
            );
        }
        this.reconnectAttempt = 0;
    }

    // ============================================================
    // Subject 管理工具
    // ============================================================

    /**
     * 创建一个受管理的 Subject，disconnect 时自动 complete。
     * 子类在 subscribe* 方法中使用此工具创建 Subject。
     */
    protected createManagedSubject<T>(): Subject<T> {
        const subject = new Subject<T>();
        this.activeSubjects.add(subject as Subject<unknown>);
        return subject;
    }

    /** 完成所有受管理的 Subject（disconnect 时调用） */
    protected completeAllSubjects(): void {
        for (const subject of this.activeSubjects) {
            subject.complete();
        }
        this.activeSubjects.clear();
    }

    // ============================================================
    // 抽象方法 —— 子类必须实现
    // ============================================================

    abstract connect(): Promise<void>;
    abstract disconnect(): Promise<void>;
    abstract subscribeTicker(symbols: string[]): Observable<Ticker>;
    abstract subscribeTrade(symbols: string[]): Observable<Trade>;
    abstract subscribeOrderbook(symbol: string, depth?: number): Observable<OrderBook>;
    abstract fetchKlines(
        symbol: string,
        interval: KlineInterval,
        startTime: number,
        endTime: number,
        limit?: number,
    ): Promise<Kline[]>;
    abstract fetchMarkets(): Promise<MarketInfo[]>;
}

export default BaseExchangeAdapter;