/*
 * Copyright 2021-2023 The NATS Authors
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { Empty } from "../nats-base-client/encoders.ts";
import { Codec, JSONCodec } from "../nats-base-client/codec.ts";
import { backoff, delay, extend } from "../nats-base-client/util.ts";
import { NatsConnectionImpl } from "../nats-base-client/nats.ts";
import { checkJsErrorCode } from "./jsutil.ts";
import {
  ErrorCode,
  JetStreamOptions,
  Msg,
  NatsConnection,
  NatsError,
  RequestOptions,
} from "../nats-base-client/core.ts";
import { ApiResponse } from "./jsapi_types.ts";

const defaultPrefix = "$JS.API";
const defaultTimeout = 5000;

export function defaultJsOptions(opts?: JetStreamOptions): JetStreamOptions {
  opts = opts || {} as JetStreamOptions;
  if (opts.domain) {
    opts.apiPrefix = `$JS.${opts.domain}.API`;
    delete opts.domain;
  }
  return extend({ apiPrefix: defaultPrefix, timeout: defaultTimeout }, opts);
}

export interface StreamNames {
  streams: string[];
}

export interface StreamNameBySubject {
  subject: string;
}

export class BaseApiClient {
  nc: NatsConnectionImpl;
  opts: JetStreamOptions;
  prefix: string;
  timeout: number;
  jc: Codec<unknown>;

  constructor(nc: NatsConnection, opts?: JetStreamOptions) {
    this.nc = nc as NatsConnectionImpl;
    this.opts = defaultJsOptions(opts);
    this._parseOpts();
    this.prefix = this.opts.apiPrefix!;
    this.timeout = this.opts.timeout!;
    this.jc = JSONCodec();
  }

  getOptions(): JetStreamOptions {
    return Object.assign({}, this.opts);
  }

  _parseOpts() {
    let prefix = this.opts.apiPrefix;
    if (!prefix || prefix.length === 0) {
      throw new Error("invalid empty prefix");
    }
    const c = prefix[prefix.length - 1];
    if (c === ".") {
      prefix = prefix.substr(0, prefix.length - 1);
    }
    this.opts.apiPrefix = prefix;
  }

  async _request(
    subj: string,
    data: unknown = null,
    opts?: Partial<RequestOptions> & { retries?: number },
  ): Promise<unknown> {
    opts = opts || {} as RequestOptions;
    opts.timeout = this.timeout;

    let a: Uint8Array = Empty;
    if (data) {
      a = this.jc.encode(data);
    }

    let { retries } = opts as {
      retries: number;
    };

    retries = retries || 1;
    retries = retries === -1 ? Number.MAX_SAFE_INTEGER : retries;
    const bo = backoff();

    for (let i = 0; i < retries; i++) {
      try {
        const m = await this.nc.request(
          subj,
          a,
          opts as RequestOptions,
        );
        return this.parseJsResponse(m);
      } catch (err) {
        const ne = err as NatsError;
        if (
          (ne.code === "503" || ne.code === ErrorCode.Timeout) &&
          i + 1 < retries
        ) {
          await delay(bo.backoff(i));
        } else {
          throw err;
        }
      }
    }
  }

  async findStream(subject: string): Promise<string> {
    const q = { subject } as StreamNameBySubject;
    const r = await this._request(`${this.prefix}.STREAM.NAMES`, q);
    const names = r as StreamNames;
    if (!names.streams || names.streams.length !== 1) {
      throw new Error("no stream matches subject");
    }
    return names.streams[0];
  }

  getConnection(): NatsConnection {
    return this.nc;
  }

  parseJsResponse(m: Msg): unknown {
    const v = this.jc.decode(m.data);
    const r = v as ApiResponse;
    if (r.error) {
      const err = checkJsErrorCode(r.error.code, r.error.description);
      if (err !== null) {
        err.api_error = r.error;
        throw err;
      }
    }
    return v;
  }
}