import EventEmitter from "events";
import crypto, { randomUUID } from "crypto";
import { IncomingMessage } from "http";
import { type WebSocket, RawData } from "ws";
import { Filter, NostrEvent, verifyEvent, matchFilters } from "nostr-tools";

import { logger } from "../logger.js";
import { SQLiteEventStore } from "../sqlite/event-store.js";

export type IncomingReqMessage = ["REQ", string, ...Filter[]];
export type IncomingCountMessage = ["COUNT", string, ...Filter[]];
export type IncomingEventMessage = ["EVENT", NostrEvent];
export type IncomingAuthMessage = ["AUTH", NostrEvent];
export type IncomingCloseMessage = ["CLOSE", string];

export type Subscription = {
  type: "REQ" | "COUNT";
  ws: WebSocket;
  id: string;
  filters: Filter[];
};

export type HandlerNext = () => Promise<void>;

export type HandlerContext = { event: NostrEvent; socket: WebSocket; relay: NostrRelay };
export type EventHandler = (
  ctx: HandlerContext,
  next: HandlerNext,
) => boolean | undefined | string | void | Promise<string | boolean | undefined | void>;

export type SubscriptionFilterContext = { id: string; filters: Filter[]; socket: WebSocket; relay: NostrRelay };
export type SubscriptionFilter = (
  ctx: SubscriptionFilterContext,
  next: HandlerNext,
) => boolean | undefined | void | Promise<boolean | undefined | void>;

type EventMap = {
  "event:received": [NostrEvent, WebSocket];
  "event:inserted": [NostrEvent, WebSocket];
  "event:rejected": [NostrEvent, WebSocket];
  "subscription:created": [Subscription, WebSocket];
  "subscription:updated": [Subscription, WebSocket];
  "subscription:closed": [Subscription, WebSocket];
  "socket:connect": [WebSocket];
  "socket:disconnect": [WebSocket];
  "socket:auth": [WebSocket, NostrEvent];
};

export class NostrRelay extends EventEmitter<EventMap> {
  static SUPPORTED_NIPS = [1, 4, 11, 45, 50, 70, 119];

  log = logger.extend("relay");
  eventStore: SQLiteEventStore;

  connectionId = new WeakMap<WebSocket, string>();

  // A map of subscriptions
  subscriptions: Subscription[] = [];

  // Create a map of connections
  // in the form <connid> : <ws>
  connections: Record<string, WebSocket> = {};

  publicURL?: string;
  requireRelayInAuth = true;
  sendChallenge = false;
  auth = new Map<WebSocket, { challenge: string; response?: NostrEvent }>();
  checkAuth?: (ws: WebSocket, auth: NostrEvent) => boolean | string;

  checkReadEvent?: (ws: WebSocket, event: NostrEvent, auth?: NostrEvent) => boolean;

  constructor(eventStore: SQLiteEventStore) {
    super();

    this.eventStore = eventStore;

    // listen for new events inserted into the store
    this.eventStore.on("event:inserted", (event) => {
      // make sure it wasn't the last event we inserted
      if (event.id !== this.lastInserted) this.sendEventToSubscriptions(event);
    });
  }

  async handleMessage(message: Buffer | string, ws: WebSocket) {
    let data;

    try {
      // TODO enforce max size

      // Parse JSON from the raw buffer
      data = JSON.parse(typeof message === "string" ? message : message.toString("utf-8"));

      if (!Array.isArray(data)) throw new Error("Message is not an array");

      // Pass the data to appropriate handler
      switch (data[0]) {
        case "REQ":
        case "COUNT":
          await this.handleSubscriptionMessage(data as IncomingReqMessage | IncomingCountMessage, ws);
          break;
        case "EVENT":
          await this.handleEventMessage(data as IncomingEventMessage, ws);
          break;
        case "AUTH":
          await this.handleAuthMessage(data as IncomingAuthMessage, ws);
          break;
        case "CLOSE":
          await this.handleCloseMessage(data as IncomingCloseMessage, ws);
          break;
      }
    } catch (err) {
      this.log("Failed to handle message", message.toString("utf-8"), err);
    }

    return data;
  }

  private socketCleanup = new Map<WebSocket, () => void>();
  handleConnection(ws: WebSocket, req: IncomingMessage) {
    let ip;

    // Record the IP address of the client
    if (typeof req.headers["x-forwarded-for"] === "string") {
      ip = req.headers["x-forwarded-for"].split(",")[0].trim();
    } else {
      ip = req.socket.remoteAddress;
    }

    // listen for messages
    const messageListener = (data: RawData, isBinary: boolean) => {
      if (data instanceof Buffer) this.handleMessage(data, ws);
    };
    ws.on("message", messageListener);

    const closeListener = () => this.handleDisconnect(ws);
    ws.on("close", closeListener);

    if (this.sendChallenge) {
      const challenge = randomUUID();
      this.auth.set(ws, { challenge });
      ws.send(JSON.stringify(["AUTH", challenge]));
    }

    this.emit("socket:connect", ws);

    // Generate a unique ID for ws connection
    const id = crypto.randomUUID();

    this.connectionId.set(ws, id);
    this.connections[id] = ws;

    this.socketCleanup.set(ws, () => {
      delete this.connections[id];
      ws.off("message", messageListener);
      ws.off("close", closeListener);
      this.connectionId.delete(ws);
      this.auth.delete(ws);
      this.emit("socket:disconnect", ws);
    });
  }

  disconnectSocket(ws: WebSocket) {
    this.socketCleanup.get(ws)?.();
  }

  handleDisconnect(ws: WebSocket) {
    const id = this.connectionId.get(ws);
    if (!id) return;

    const openSubscriptions = this.subscriptions.filter((sub) => sub.ws === ws);

    // remove all subscriptions
    this.subscriptions = this.subscriptions.filter((sub) => sub.ws !== ws);

    for (const sub of openSubscriptions) {
      this.emit("subscription:closed", sub, ws);
    }

    this.connectionId.delete(ws);
    delete this.connections[id];

    this.emit("socket:disconnect", ws);
  }

  sendEventToSubscriptions(event: NostrEvent) {
    for (const sub of this.subscriptions) {
      if (sub.type === "REQ" && !sub.filters.some((f) => f.search) && matchFilters(sub.filters, event)) {
        sub.ws.send(JSON.stringify(["EVENT", sub.id, event]));
      }
    }
  }

  /** Used to avoid infinite loop */
  private lastInserted: string = "";

  eventHandlers: EventHandler[] = [];
  private async callEventHandler(ctx: HandlerContext, index = 0): Promise<string | boolean | undefined | void> {
    const handler = this.eventHandlers[index];
    if (!handler) return;

    return await handler(ctx, async () => {
      await this.callEventHandler(ctx, index + 1);
    });
  }

  registerEventHandler(handler: EventHandler) {
    this.eventHandlers.push(handler);

    return () => this.unregisterEventHandler(handler);
  }
  unregisterEventHandler(handler: EventHandler) {
    const idx = this.eventHandlers.indexOf(handler);
    if (idx !== -1) this.eventHandlers.splice(idx, 1);
  }

  async handleEventMessage(data: IncomingEventMessage, ws: WebSocket) {
    // Get the event data
    const event = data[1] as NostrEvent;

    try {
      let inserted = false;

      // Verify the event's signature
      if (!verifyEvent(event)) throw new Error(`invalid: event failed to validate or verify`);

      // NIP-70 protected events
      const isProtected = event.tags.some((t) => t[0] === "-");
      if (isProtected && this.auth.get(ws)?.response?.pubkey !== event.pubkey) {
        throw new Error("auth-required: this event may only be published by its author");
      }

      const context: HandlerContext = { event, socket: ws, relay: this };
      let persist = (await this.callEventHandler(context)) ?? true;

      if (persist) {
        try {
          // Persist to database
          this.lastInserted = event.id;
          inserted = this.eventStore.addEvent(event);
        } catch (err) {
          console.log(err);
          throw new Error(`error: server error`);
        }

        this.emit("event:received", event, ws);
        if (inserted) {
          this.emit("event:inserted", event, ws);
          this.sendPublishOkMessage(ws, event, true, typeof persist === "string" ? persist : "");

          this.sendEventToSubscriptions(event);
        } else {
          this.sendPublishOkMessage(ws, event, true, typeof persist === "string" ? persist : "Duplicate");
        }
      } else {
        // reject with generic message
        throw new Error("Rejected");
      }
    } catch (err) {
      if (err instanceof Error) {
        // error occurred, send back the OK message with false
        this.emit("event:rejected", event, ws);
        this.sendPublishOkMessage(ws, event, false, err.message);
      }
    }
  }

  // response helpers
  makeAuthRequiredReason(reason: string) {
    return "auth-required: " + reason;
  }
  sendPublishOkMessage(ws: WebSocket, event: NostrEvent, success: boolean, message?: string) {
    ws.send(JSON.stringify(message ? ["OK", event.id, success, message] : ["OK", event.id, success]));
  }
  sendPublishAuthRequired(ws: WebSocket, event: NostrEvent, message: string) {
    ws.send(JSON.stringify(["OK", event.id, false, this.makeAuthRequiredReason(message)]));
  }

  handleAuthMessage(data: IncomingAuthMessage, ws: WebSocket) {
    try {
      const event = data[1];
      if (!verifyEvent(event)) {
        return this.sendPublishOkMessage(ws, event, false, "Invalid event");
      }

      const relay = event.tags.find((t) => t[0] === "relay")?.[1];
      if (this.requireRelayInAuth) {
        if (!relay) {
          return this.sendPublishOkMessage(ws, event, false, "Missing relay tag");
        }
        if (new URL(relay).toString() !== this.publicURL) {
          return this.sendPublishOkMessage(ws, event, false, "Bad relay tag");
        }
      }

      // check challenge
      const challenge = this.auth.get(ws)?.challenge;
      const challengeResponse = event.tags.find((t) => t[0] === "challenge")?.[1];

      if (!challengeResponse || !challenge) {
        return this.sendPublishOkMessage(ws, event, false, "Missing challenge tag");
      }
      if (challengeResponse !== challenge) {
        return this.sendPublishOkMessage(ws, event, false, "Bad challenge");
      }

      if (this.checkAuth) {
        const message = this.checkAuth(ws, event);
        if (typeof message === "string") return this.sendPublishOkMessage(ws, event, false, message);
        else if (message === false) return this.sendPublishOkMessage(ws, event, false, "Rejected auth");
      }

      this.auth.set(ws, { challenge, response: event });
      this.emit("socket:auth", ws, event);
      this.log("Authenticated", event.pubkey);
      this.sendPublishOkMessage(ws, event, true, "Authenticated");
    } catch (e) {}
  }

  protected runSubscription(sub: Subscription) {
    const auth = this.getSocketAuth(sub.ws);

    switch (sub.type) {
      case "REQ":
        const events = this.eventStore.getEventsForFilters(sub.filters);
        for (let event of events) {
          if (!this.checkReadEvent || this.checkReadEvent(sub.ws, event, auth)) {
            sub.ws.send(JSON.stringify(["EVENT", sub.id, event]));
          }
        }
        sub.ws.send(JSON.stringify(["EOSE", sub.id]));
        break;
      case "COUNT":
        const count = this.eventStore.countEventsForFilters(sub.filters);
        sub.ws.send(JSON.stringify(["COUNT", sub.id, { count }]));
        break;
    }
  }

  subscriptionFilters: SubscriptionFilter[] = [];
  private async checkSubscriptionFilters(
    ctx: SubscriptionFilterContext,
    index = 0,
  ): Promise<boolean | undefined | void> {
    const handler = this.subscriptionFilters[index];
    if (!handler) return;

    return await handler(ctx, async () => {
      await this.checkSubscriptionFilters(ctx, index + 1);
    });
  }
  registerSubscriptionFilter(filter: SubscriptionFilter) {
    this.subscriptionFilters.push(filter);

    return () => this.unregisterSubscriptionFilter(filter);
  }
  unregisterSubscriptionFilter(filter: SubscriptionFilter) {
    const idx = this.subscriptionFilters.indexOf(filter);
    if (idx !== -1) this.subscriptionFilters.splice(idx, 1);
  }

  async handleSubscriptionMessage(data: IncomingReqMessage | IncomingCountMessage, ws: WebSocket) {
    const [type, id, ...filters] = data;
    if (typeof id !== "string" || filters.length === 0) return;

    try {
      const allow = (await this.checkSubscriptionFilters({ socket: ws, filters, id, relay: this })) ?? true;

      if (allow === false) {
        return this.closeSubscription(id, ws, "Rejected");
      }

      let subscription = this.subscriptions.find((s) => s.id === id) || { type, id: id, ws, filters: [] };

      // override or set the filters
      subscription.filters = filters;

      // only save the subscription if its not a count
      if (type !== "COUNT") {
        if (!this.subscriptions.includes(subscription)) {
          this.subscriptions.push(subscription);
          this.emit("subscription:created", subscription, ws);
        } else {
          this.emit("subscription:updated", subscription, ws);
        }
      }

      // Run the subscription
      await this.runSubscription(subscription);
    } catch (error) {
      if (typeof error === "string") {
        this.closeSubscription(id, ws, error);
      } else if (error instanceof Error) {
        this.closeSubscription(id, ws, error.message);
      }
    }
  }

  closeSubscription(id: string, ws?: WebSocket, reason?: string) {
    const subscription = this.subscriptions.find((s) => s.id === id && (ws ? s.ws === ws : true));
    if (subscription) {
      this.subscriptions.splice(this.subscriptions.indexOf(subscription), 1);
      this.emit("subscription:closed", subscription, subscription.ws);
    }

    if (reason) (subscription?.ws || ws)?.send(JSON.stringify(["CLOSED", id, reason]));
  }
  handleCloseMessage(data: IncomingCloseMessage, ws: WebSocket) {
    if (typeof data[1] !== "string") return;
    const id = data[1];

    this.closeSubscription(id, ws);
  }

  getSocketAuth(ws: WebSocket) {
    return this.auth.get(ws)?.response;
  }

  stop() {
    for (const ws of Object.values(this.connections)) {
      ws.close();
    }
    this.removeAllListeners();
  }
}