/*
 This file is part of TALER
 (C) 2016 GNUnet e.V.

 TALER is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 TALER is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */


/**
 * API to access the Taler crypto worker thread.
 * @author Florian Dold
 */

/**
 * Imports.
 */
import {
  AmountJson,
  CoinRecord,
  ContractTerms,
  DenominationRecord,
  PayCoinInfo,
  PaybackRequest,
  PreCoinRecord,
  RefreshSessionRecord,
  ReserveRecord,
  WireFee,
} from "../types";

import {
  CoinWithDenom,
} from "../wallet";

import * as timer from "../timer";

import { startWorker } from "./startWorker";


/**
 * State of a crypto worker.
 */
interface WorkerState {
  /**
   * The actual worker thread.
   */
  w: Worker|null;

  /**
   * Work we're currently executing or null if not busy.
   */
  currentWorkItem: WorkItem|null;

  /**
   * Timer to terminate the worker if it's not busy enough.
   */
  terminationTimerHandle: timer.TimerHandle|null;
}

interface WorkItem {
  operation: string;
  args: any[];
  resolve: any;
  reject: any;

  /**
   * Serial id to identify a matching response.
   */
  rpcId: number;
}


/**
 * Number of different priorities. Each priority p
 * must be 0 <= p < NUM_PRIO.
 */
const NUM_PRIO = 5;

/**
 * Crypto API that interfaces manages a background crypto thread
 * for the execution of expensive operations.
 */
export class CryptoApi {
  private nextRpcId: number = 1;
  private workers: WorkerState[];
  private workQueues: WorkItem[][];
  /**
   * Number of busy workers.
   */
  private numBusy: number = 0;

  /**
   * Start a worker (if not started) and set as busy.
   */
  wake(ws: WorkerState, work: WorkItem): void {
    if (ws.currentWorkItem !== null) {
      throw Error("assertion failed");
    }
    ws.currentWorkItem = work;
    this.numBusy++;
    if (!ws.w) {
      const w = startWorker();
      w.onmessage = (m: MessageEvent) => this.handleWorkerMessage(ws, m);
      w.onerror = (e: ErrorEvent) => this.handleWorkerError(ws, e);
      ws.w = w;
    }

    const msg: any = {
      args: work.args,
      id: work.rpcId,
      operation: work.operation,
    };
    this.resetWorkerTimeout(ws);
    ws.w!.postMessage(msg);
  }

  resetWorkerTimeout(ws: WorkerState) {
    if (ws.terminationTimerHandle !== null) {
      ws.terminationTimerHandle.clear();
      ws.terminationTimerHandle = null;
    }
    const destroy = () => {
      // terminate worker if it's idle
      if (ws.w && ws.currentWorkItem === null) {
        ws.w!.terminate();
        ws.w = null;
      }
    };
    ws.terminationTimerHandle = timer.after(20 * 1000, destroy);
  }

  handleWorkerError(ws: WorkerState, e: ErrorEvent) {
    if (ws.currentWorkItem) {
      console.error(`error in worker during ${ws.currentWorkItem!.operation}`,
                    e);
    } else {
      console.error("error in worker", e);
    }
    console.error(e.message);
    try {
      ws.w!.terminate();
      ws.w = null;
    } catch (e) {
      console.error(e);
    }
    if (ws.currentWorkItem !== null) {
      ws.currentWorkItem.reject(e);
      ws.currentWorkItem = null;
      this.numBusy--;
    }
    this.findWork(ws);
  }

  findWork(ws: WorkerState) {
    // try to find more work for this worker
    for (let i = 0; i < NUM_PRIO; i++) {
      const q = this.workQueues[NUM_PRIO - i - 1];
      if (q.length !== 0) {
        const work: WorkItem = q.shift()!;
        this.wake(ws, work);
        return;
      }
    }
  }

  handleWorkerMessage(ws: WorkerState, msg: MessageEvent) {
    const id = msg.data.id;
    if (typeof id !== "number") {
      console.error("rpc id must be number");
      return;
    }
    const currentWorkItem = ws.currentWorkItem;
    ws.currentWorkItem = null;
    this.numBusy--;
    this.findWork(ws);
    if (!currentWorkItem) {
      console.error("unsolicited response from worker");
      return;
    }
    if (id !== currentWorkItem.rpcId) {
      console.error(`RPC with id ${id} has no registry entry`);
      return;
    }
    currentWorkItem.resolve(msg.data.result);
  }

  constructor() {
    let concurrency = 2;
    try {
      // only works in the browser
      // tslint:disable-next-line:no-string-literal
      concurrency = (navigator as any)["hardwareConcurrency"];
    } catch (e) {
      // ignore
    }
    this.workers = new Array<WorkerState>(concurrency);

    for (let i = 0; i < this.workers.length; i++) {
      this.workers[i] = {
        currentWorkItem: null,
        terminationTimerHandle: null,
        w: null,
      };
    }
    this.workQueues = [];
    for (let i = 0; i < NUM_PRIO; i++) {
      this.workQueues.push([]);
    }
  }

  private doRpc<T>(operation: string, priority: number,
                   ...args: any[]): Promise<T> {
    const start = timer.performanceNow();

    const p = new Promise((resolve, reject) => {
      const rpcId = this.nextRpcId++;
      const workItem: WorkItem = {operation, args, resolve, reject, rpcId};

      if (this.numBusy === this.workers.length) {
        const q = this.workQueues[priority];
        if (!q) {
          throw Error("assertion failed");
        }
        this.workQueues[priority].push(workItem);
        return;
      }

      for (const ws of this.workers) {
        if (ws.currentWorkItem !== null) {
          continue;
        }

        this.wake(ws, workItem);
        return;
      }

      throw Error("assertion failed");
    });

    return p.then((r: T) => {
      console.log(`rpc ${operation} took ${timer.performanceNow() - start}ms`);
      return r;
    });
  }


  createPreCoin(denom: DenominationRecord, reserve: ReserveRecord): Promise<PreCoinRecord> {
    return this.doRpc<PreCoinRecord>("createPreCoin", 1, denom, reserve);
  }

  hashString(str: string): Promise<string> {
    return this.doRpc<string>("hashString", 1, str);
  }

  hashDenomPub(denomPub: string): Promise<string> {
    return this.doRpc<string>("hashDenomPub", 1, denomPub);
  }

  isValidDenom(denom: DenominationRecord,
               masterPub: string): Promise<boolean> {
    return this.doRpc<boolean>("isValidDenom", 2, denom, masterPub);
  }

  isValidWireFee(type: string, wf: WireFee, masterPub: string): Promise<boolean> {
    return this.doRpc<boolean>("isValidWireFee", 2, type, wf, masterPub);
  }

  isValidPaymentSignature(sig: string, contractHash: string, merchantPub: string) {
    return this.doRpc<PayCoinInfo>("isValidPaymentSignature", 1, sig, contractHash, merchantPub);
  }

  signDeposit(contractTerms: ContractTerms,
              cds: CoinWithDenom[]): Promise<PayCoinInfo> {
    return this.doRpc<PayCoinInfo>("signDeposit", 3, contractTerms, cds);
  }

  createEddsaKeypair(): Promise<{priv: string, pub: string}> {
    return this.doRpc<{priv: string, pub: string}>("createEddsaKeypair", 1);
  }

  rsaUnblind(sig: string, bk: string, pk: string): Promise<string> {
    return this.doRpc<string>("rsaUnblind", 4, sig, bk, pk);
  }

  createPaybackRequest(coin: CoinRecord): Promise<PaybackRequest> {
    return this.doRpc<PaybackRequest>("createPaybackRequest", 1, coin);
  }

  createRefreshSession(exchangeBaseUrl: string,
                       kappa: number,
                       meltCoin: CoinRecord,
                       newCoinDenoms: DenominationRecord[],
                       meltFee: AmountJson): Promise<RefreshSessionRecord> {
    return this.doRpc<RefreshSessionRecord>("createRefreshSession",
                      4,
                      exchangeBaseUrl,
                      kappa,
                      meltCoin,
                      newCoinDenoms,
                      meltFee);
  }
}