// Copyright (C) 2018 The Android Open Source Project
//
// 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 {assertExists} from '../base/logging';
import {deleteQuery} from '../common/actions';
import {rawQueryResultColumns, rawQueryResultIter, Row} from '../common/protos';
import {QueryResponse} from '../common/queries';
import {Controller} from './controller';
import {Engine} from './engine';
import {globals} from './globals';

export interface QueryControllerArgs {
  queryId: string;
  engine: Engine;
}

export class QueryController extends Controller<'init'|'querying'> {
  constructor(private args: QueryControllerArgs) {
    super('init');
  }

  run() {
    switch (this.state) {
      case 'init':
        const config = assertExists(globals.state.queries[this.args.queryId]);
        this.runQuery(config.query).then(result => {
          console.log(`Query ${config.query} took ${result.durationMs} ms`);
          globals.publish('QueryResult', {id: this.args.queryId, data: result});
          globals.dispatch(deleteQuery(this.args.queryId));
        });
        this.setState('querying');
        break;

      case 'querying':
        // Nothing to do here, as soon as the deleteQuery is dispatched this
        // controller will be destroyed (by the TraceController).
        break;

      default:
        throw new Error(`Unexpected state ${this.state}`);
    }
  }

  private async runQuery(sqlQuery: string) {
    const startMs = performance.now();
    const rawResult = await this.args.engine.query(sqlQuery);
    const durationMs = performance.now() - startMs;
    const columns = rawQueryResultColumns(rawResult);
    const rows =
        QueryController.firstN<Row>(10000, rawQueryResultIter(rawResult));
    const result: QueryResponse = {
      id: this.args.queryId,
      query: sqlQuery,
      durationMs,
      error: rawResult.error,
      totalRowCount: +rawResult.numRecords,
      columns,
      rows,
    };
    return result;
  }

  private static firstN<T>(n: number, iter: IterableIterator<T>): T[] {
    const list = [];
    for (let i = 0; i < n; i++) {
      const {done, value} = iter.next();
      if (done) break;
      list.push(value);
    }
    return list;
  }
}