// Copyright (c) 2020-2021 Drew Lemmy
// This file is part of KristWeb 2 under AGPL-3.0.
// Full details: https://github.com/tmpim/KristWeb2/blob/master/LICENSE.txt
import { store } from "@app";
import * as wsActions from "@actions/WebsocketActions";
import * as nodeActions from "@actions/NodeActions";

import * as api from "@api";
import { KristAddress, KristBlock, KristTransaction, WSConnectionState, WSIncomingMessage, WSSubscriptionLevel } from "@api/types";
import { Wallet, WalletMap, findWalletByAddress, syncWalletUpdate } from "@wallets";
import WebSocketAsPromised from "websocket-as-promised";

import { WSSubscription } from "./WebsocketSubscription";

import { throttle } from "lodash-es";

import Debug from "debug";
const debug = Debug("kristweb:websocket-connection");

const REFRESH_THROTTLE_MS = 500;
const DEFAULT_CONNECT_DEBOUNCE_MS = 1000;
const MAX_CONNECT_DEBOUNCE_MS = 360000;

export class WebsocketConnection {
  private wallets?: WalletMap;
  private ws?: WebSocketAsPromised;
  private reconnectionTimer?: number;

  private messageID = 1;
  private connectDebounce = DEFAULT_CONNECT_DEBOUNCE_MS;

  private forceClosing = false;

  private refreshThrottles: Record<string, (address: string) => void> = {};

  private subscriptions: Record<string, WSSubscription> = {};

  constructor(public syncNode: string) {
    debug("WS component init");
    this.attemptConnect();
  }

  setWallets(wallets: WalletMap): void {
    this.wallets = wallets;
  }

  private async connect() {
    debug("attempting connection to server...");
    this.setConnectionState("disconnected");

    // Get a websocket token
    const { url } = await api.post<{ url: string }>("ws/start");

    this.setConnectionState("connecting");

    // Connect to the websocket server
    this.ws = new WebSocketAsPromised(url, {
      packMessage: data => JSON.stringify(data),
      unpackMessage: data => JSON.parse(data.toString())
    });

    this.ws.onUnpackedMessage.addListener(this.handleMessage.bind(this));
    this.ws.onClose.addListener(this.handleClose.bind(this));

    this.messageID = 1;
    await this.ws.open();
    this.connectDebounce = DEFAULT_CONNECT_DEBOUNCE_MS;
  }

  async attemptConnect(): Promise<void> {
    try {
      await this.connect();
    } catch (err) {
      this.handleDisconnect(err);
    }
  }

  private handleDisconnect(err?: Error) {
    if (this.reconnectionTimer) window.clearTimeout(this.reconnectionTimer);

    // TODO: show errors to the user?
    this.setConnectionState("disconnected");
    debug("failed to connect to server, reconnecting in %d ms", this.connectDebounce, err);

    this.reconnectionTimer = window.setTimeout(() => {
      this.connectDebounce = Math.min(this.connectDebounce * 2, MAX_CONNECT_DEBOUNCE_MS);
      this.attemptConnect();
    }, this.connectDebounce);
  }

  handleClose(event: { code: number; reason: string }): void {
    debug("ws closed with code %d reason %s", event.code, event.reason);
    this.handleDisconnect();
  }

  /** Forcibly disconnect this instance from the websocket server (e.g. on
   * component unmount) */
  forceClose(): void {
    debug("received force close request");

    if (this.forceClosing) return;
    this.forceClosing = true;

    if (!this.ws || !this.ws.isOpened || this.ws.isClosed) return;
    debug("force closing ws");
    this.ws.close();
  }

  private setConnectionState(state: WSConnectionState) {
    debug("ws conn state: %s", state);
    store.dispatch(wsActions.setConnectionState(state));
  }

  handleMessage(data: WSIncomingMessage): void {
    if (!this.ws || !this.ws.isOpened || this.ws.isClosed) return;

    if (data.ok === false || data.error)
      debug("message ERR: %d %s", data.id || -1, data.error);

    if (data.type === "hello") {
      // Initial connection
      debug("connected");

      // Subscribe to all the events
      this.subscribe("transactions");
      this.subscribe("blocks");
      this.subscribe("names");
      this.subscribe("motd");

      this.setConnectionState("connected");
    } else if (data.address && this.wallets) {
      // Probably a response to `refreshBalance`
      const address: KristAddress = data.address;
      const wallet = findWalletByAddress(this.wallets, address.address);
      if (!wallet) return;

      debug("syncing %s to %s (balance: %d)", address.address, wallet.id, address.balance);
      syncWalletUpdate(wallet, address);
    } else if (data.type === "event" && data.event && this.wallets) {
      // Handle events
      switch (data.event) {
      case "transaction": {
        // If we receive a transaction relevant to any of our wallets, refresh
        // the balances.
        const transaction = data.transaction as KristTransaction;
        debug("transaction [%s] from %s to %s", transaction.type, transaction.from || "null", transaction.to || "null");

        const fromWallet = findWalletByAddress(this.wallets, transaction.from || undefined);
        const toWallet = findWalletByAddress(this.wallets, transaction.to);

        this.updateTransactionIDs(transaction, fromWallet, toWallet);

        switch (transaction.type) {
        // Update the name counts using the address lookup
        case "name_purchase":
        case "name_transfer":
          if (fromWallet) this.refreshBalance(fromWallet.address, true);
          if (toWallet) this.refreshBalance(toWallet.address, true);
          break;

        // Any other transaction; refresh the balances via the websocket
        default:
          if (fromWallet) this.refreshBalance(fromWallet.address);
          if (toWallet) this.refreshBalance(toWallet.address);
          break;
        }

        break;
      }
      case "block": {
        // Update the last block ID, which will trigger a re-fetch for
        // work-related and block value-related components.
        const block = data.block as KristBlock;
        debug("block id now %d", block.height);

        store.dispatch(nodeActions.setLastBlockID(block.height));

        break;
      }
      }
    }
  }

  private updateTransactionIDs(transaction: KristTransaction, fromWallet?: Wallet | null, toWallet?: Wallet | null) {
    // Updating these last IDs will trigger auto-refreshes on pages that need
    // them
    const {
      id,
      from, to,
      name: txName, sent_name: txSentName,
      type
    } = transaction;

    // Generic "last transaction ID", used for network transaction tables
    debug("lastTransactionID now %d", id);
    store.dispatch(nodeActions.setLastTransactionID(id));

    // Transactions to/from our own wallets, for the "my transactions" table
    if (fromWallet || toWallet) {
      debug("lastOwnTransactionID now %d", id);
      store.dispatch(nodeActions.setLastOwnTransactionID(id));
    }

    // Name transactions to/from our own names and network names
    if (type.startsWith("name_")) {
      debug("lastNameTransactionID now %d", id);
      store.dispatch(nodeActions.setLastNameTransactionID(id));

      if (fromWallet || toWallet) {
        debug("lastOwnNameTransactionID now %d", id);
        store.dispatch(nodeActions.setLastOwnNameTransactionID(id));
      }
    }

    // Non-mined transactions for transaction tables that exclude mined
    // transactions
    if (type !== "mined") {
      debug("lastNonMinedTransactionID now %d", id);
      store.dispatch(nodeActions.setLastNonMinedTransactionID(id));
    }

    // Find addresses/names that we are subscribed to
    for (const subID in this.subscriptions) {
      const { address, name } = this.subscriptions[subID];

      // Found a subscription interested in the addresses involved in this tx
      if (from && address === from || to && address === to) {
        debug("[address] updating subscription %s id to %d", subID, id);
        store.dispatch(wsActions.updateSubscription(subID, id));
      }

      // Found a subscription interested in the name involved in this tx
      if ((txName && txName === name) || (txSentName && txSentName === name)) {
        debug("[name] updating subscription %s id to %d", subID, id);
        store.dispatch(wsActions.updateSubscription(subID, id));
      }
    }
  }

  /** Queues a command to re-fetch an address's balance. The response will be
   * handled in {@link handleMessage}. This is automatically throttled to
   * execute on the leading edge of 500ms (REFRESH_THROTTLE_MS). */
  refreshBalance(address: string, fetchNames?: boolean): void {
    if (this.refreshThrottles[address]) {
      // Use the existing throttled function if it exists
      this.refreshThrottles[address](address);
    } else {
      // Create and cache a new throttle function for this address
      const throttled = throttle(
        this._refreshBalance.bind(this),
        REFRESH_THROTTLE_MS,
        { leading: true, trailing: false }
      );

      this.refreshThrottles[address] = throttled;
      throttled(address, fetchNames);
    }
  }

  private _refreshBalance(address: string, fetchNames?: boolean) {
    debug("refreshing balance of %s", address);
    this.ws?.sendPacked({
      type: "address",
      id: this.messageID++,
      address,
      fetchNames
    });
  }

  /** Subscribe to a Krist WS event. */
  subscribe(event: WSSubscriptionLevel): void {
    this.ws?.sendPacked({ type: "subscribe", event, id: this.messageID++ });
  }

  addSubscription(id: string, subscription: WSSubscription): void {
    debug("ws received added subscription %s", id);
    this.subscriptions[id] = subscription;
  }

  removeSubscription(id: string): void {
    debug("ws received removed subscription %s", id);
    if (this.subscriptions[id]) delete this.subscriptions[id];
  }
}