///
/// Copyright © 2016-2019 The Thingsboard 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 { Injectable } from '@angular/core';
import { DAY, defaultTimeIntervals, SECOND } from '@shared/models/time/time.models';
import {HttpClient} from '@angular/common/http';
import {Observable} from 'rxjs';
import {defaultHttpOptions} from '@core/http/http-utils';
import {map} from 'rxjs/operators';

export interface TimeInterval {
  name: string;
  translateParams: {[key: string]: any};
  value: number;
}

const MIN_INTERVAL = SECOND;
const MAX_INTERVAL = 365 * 20 * DAY;

const MIN_LIMIT = 10;

const MAX_DATAPOINTS_LIMIT = 500;

@Injectable({
  providedIn: 'root'
})
export class TimeService {

  private maxDatapointsLimit = MAX_DATAPOINTS_LIMIT;

  constructor(
    private http: HttpClient
  ) {}

  public loadMaxDatapointsLimit(): Observable<number> {
    return this.http.get<number>('/api/dashboard/maxDatapointsLimit',
      defaultHttpOptions(true)).pipe(
        map( (limit) => {
          this.maxDatapointsLimit = limit;
          if (!this.maxDatapointsLimit || this.maxDatapointsLimit <= MIN_LIMIT) {
            this.maxDatapointsLimit = MIN_LIMIT + 1;
          }
          return this.maxDatapointsLimit;
        })
      );
  }

  public matchesExistingInterval(min: number, max: number, intervalMs: number): boolean {
    const intervals = this.getIntervals(min, max);
    return intervals.findIndex(interval => interval.value === intervalMs) > -1;
  }

  public getIntervals(min: number, max: number): Array<TimeInterval> {
    min = this.boundMinInterval(min);
    max = this.boundMaxInterval(max);
    return defaultTimeIntervals.filter((interval) => interval.value >= min && interval.value <= max);
  }

  public boundMinInterval(min: number): number {
    return this.toBound(min, MIN_INTERVAL, MAX_INTERVAL, MIN_INTERVAL);
  }

  public boundMaxInterval(max: number): number {
    return this.toBound(max, MIN_INTERVAL, MAX_INTERVAL, MAX_INTERVAL);
  }

  public boundToPredefinedInterval(min: number, max: number, intervalMs: number): number {
    const intervals = this.getIntervals(min, max);
    let minDelta = MAX_INTERVAL;
    const boundedInterval = intervalMs || min;
    let matchedInterval: TimeInterval = intervals[0];
    intervals.forEach((interval) => {
      const delta = Math.abs(interval.value - boundedInterval);
      if (delta < minDelta) {
        matchedInterval = interval;
        minDelta = delta;
      }
    });
    return matchedInterval.value;
  }

  public getMaxDatapointsLimit(): number {
    return this.maxDatapointsLimit;
  }

  public getMinDatapointsLimit(): number {
    return MIN_LIMIT;
  }

  public minIntervalLimit(timewindowMs: number): number {
    const min = timewindowMs / 500;
    return this.boundMinInterval(min);
  }

  public maxIntervalLimit(timewindowMs: number): number {
    const max = timewindowMs / MIN_LIMIT;
    return this.boundMaxInterval(max);
  }

  private toBound(value: number, min: number, max: number, defValue: number): number {
    if (typeof value !== 'undefined') {
      value = Math.max(value, min);
      value = Math.min(value, max);
      return value;
    } else {
      return defValue;
    }
  }

}