/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {InjectionToken, LOCALE_ID} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import {Subject} from 'rxjs/Subject';


/** InjectionToken for datepicker that can be used to override default locale code. */
export const MAT_DATE_LOCALE = new InjectionToken<string>('MAT_DATE_LOCALE');

/** Provider for MAT_DATE_LOCALE injection token. */
export const MAT_DATE_LOCALE_PROVIDER = {provide: MAT_DATE_LOCALE, useExisting: LOCALE_ID};

/** Adapts type `D` to be usable as a date by cdk-based components that work with dates. */
export abstract class DateAdapter<D> {
  /** The locale to use for all dates. */
  protected locale: any;

  /** A stream that emits when the locale changes. */
  get localeChanges(): Observable<void> { return this._localeChanges; }
  protected _localeChanges= new Subject<void>();

  /**
   * Gets the year component of the given date.
   * @param date The date to extract the year from.
   * @returns The year component.
   */
  abstract getYear(date: D): number;

  /**
   * Gets the month component of the given date.
   * @param date The date to extract the month from.
   * @returns The month component (0-indexed, 0 = January).
   */
  abstract getMonth(date: D): number;

  /**
   * Gets the date of the month component of the given date.
   * @param date The date to extract the date of the month from.
   * @returns The month component (1-indexed, 1 = first of month).
   */
  abstract getDate(date: D): number;

  /**
   * Gets the day of the week component of the given date.
   * @param date The date to extract the day of the week from.
   * @returns The month component (0-indexed, 0 = Sunday).
   */
  abstract getDayOfWeek(date: D): number;

  /**
   * Gets a list of names for the months.
   * @param style The naming style (e.g. long = 'January', short = 'Jan', narrow = 'J').
   * @returns An ordered list of all month names, starting with January.
   */
  abstract getMonthNames(style: 'long' | 'short' | 'narrow'): string[];

  /**
   * Gets a list of names for the dates of the month.
   * @returns An ordered list of all date of the month names, starting with '1'.
   */
  abstract getDateNames(): string[];

  /**
   * Gets a list of names for the days of the week.
   * @param style The naming style (e.g. long = 'Sunday', short = 'Sun', narrow = 'S').
   * @returns An ordered list of all weekday names, starting with Sunday.
   */
  abstract getDayOfWeekNames(style: 'long' | 'short' | 'narrow'): string[];

  /**
   * Gets the name for the year of the given date.
   * @param date The date to get the year name for.
   * @returns The name of the given year (e.g. '2017').
   */
  abstract getYearName(date: D): string;

  /**
   * Gets the first day of the week.
   * @returns The first day of the week (0-indexed, 0 = Sunday).
   */
  abstract getFirstDayOfWeek(): number;

  /**
   * Gets the number of days in the month of the given date.
   * @param date The date whose month should be checked.
   * @returns The number of days in the month of the given date.
   */
  abstract getNumDaysInMonth(date: D): number;

  /**
   * Clones the given date.
   * @param date The date to clone
   * @returns A new date equal to the given date.
   */
  abstract clone(date: D): D;

  /**
   * Creates a date with the given year, month, and date. Does not allow over/under-flow of the
   * month and date.
   * @param year The full year of the date. (e.g. 89 means the year 89, not the year 1989).
   * @param month The month of the date (0-indexed, 0 = January). Must be an integer 0 - 11.
   * @param date The date of month of the date. Must be an integer 1 - length of the given month.
   * @returns The new date, or null if invalid.
   */
  abstract createDate(year: number, month: number, date: number): D;

  /**
   * Gets today's date.
   * @returns Today's date.
   */
  abstract today(): D;

  /**
   * Parses a date from a user-provided value.
   * @param value The value to parse.
   * @param parseFormat The expected format of the value being parsed
   *     (type is implementation-dependent).
   * @returns The parsed date.
   */
  abstract parse(value: any, parseFormat: any): D | null;

  /**
   * Formats a date as a string according to the given format.
   * @param date The value to format.
   * @param displayFormat The format to use to display the date as a string.
   * @returns The formatted date string.
   */
  abstract format(date: D, displayFormat: any): string;

  /**
   * Adds the given number of years to the date. Years are counted as if flipping 12 pages on the
   * calendar for each year and then finding the closest date in the new month. For example when
   * adding 1 year to Feb 29, 2016, the resulting date will be Feb 28, 2017.
   * @param date The date to add years to.
   * @param years The number of years to add (may be negative).
   * @returns A new date equal to the given one with the specified number of years added.
   */
  abstract addCalendarYears(date: D, years: number): D;

  /**
   * Adds the given number of months to the date. Months are counted as if flipping a page on the
   * calendar for each month and then finding the closest date in the new month. For example when
   * adding 1 month to Jan 31, 2017, the resulting date will be Feb 28, 2017.
   * @param date The date to add months to.
   * @param months The number of months to add (may be negative).
   * @returns A new date equal to the given one with the specified number of months added.
   */
  abstract addCalendarMonths(date: D, months: number): D;

  /**
   * Adds the given number of days to the date. Days are counted as if moving one cell on the
   * calendar for each day.
   * @param date The date to add days to.
   * @param days The number of days to add (may be negative).
   * @returns A new date equal to the given one with the specified number of days added.
   */
  abstract addCalendarDays(date: D, days: number): D;

  /**
   * Gets the RFC 3339 compatible string (https://tools.ietf.org/html/rfc3339) for the given date.
   * This method is used to generate date strings that are compatible with native HTML attributes
   * such as the `min` or `max` attribute of an `<input>`.
   * @param date The date to get the ISO date string for.
   * @returns The ISO date string date string.
   */
  abstract toIso8601(date: D): string;

  /**
   * Checks whether the given object is considered a date instance by this DateAdapter.
   * @param obj The object to check
   * @returns Whether the object is a date instance.
   */
  abstract isDateInstance(obj: any): boolean;

  /**
   * Checks whether the given date is valid.
   * @param date The date to check.
   * @returns Whether the date is valid.
   */
  abstract isValid(date: D): boolean;

  /**
   * Gets date instance that is not valid.
   * @returns An invalid date.
   */
  abstract invalid(): D;

  /**
   * Attempts to deserialize a value to a valid date object. This is different from parsing in that
   * deserialize should only accept non-ambiguous, locale-independent formats (e.g. a ISO 8601
   * string). The default implementation does not allow any deserialization, it simply checks that
   * the given value is already a valid date object or null. The `<mat-datepicker>` will call this
   * method on all of it's `@Input()` properties that accept dates. It is therefore possible to
   * support passing values from your backend directly to these properties by overriding this method
   * to also deserialize the format used by your backend.
   * @param value The value to be deserialized into a date object.
   * @returns The deserialized date object, either a valid date, null if the value can be
   *     deserialized into a null date (e.g. the empty string), or an invalid date.
   */
  deserialize(value: any): D | null {
    if (value == null || this.isDateInstance(value) && this.isValid(value)) {
      return value;
    }
    return this.invalid();
  }

  /**
   * Sets the locale used for all dates.
   * @param locale The new locale.
   */
  setLocale(locale: any) {
    this.locale = locale;
    this._localeChanges.next();
  }

  /**
   * Compares two dates.
   * @param first The first date to compare.
   * @param second The second date to compare.
   * @returns 0 if the dates are equal, a number less than 0 if the first date is earlier,
   *     a number greater than 0 if the first date is later.
   */
  compareDate(first: D, second: D): number {
    return this.getYear(first) - this.getYear(second) ||
        this.getMonth(first) - this.getMonth(second) ||
        this.getDate(first) - this.getDate(second);
  }

  /**
   * Checks if two dates are equal.
   * @param first The first date to check.
   * @param second The second date to check.
   * @returns Whether the two dates are equal.
   *     Null dates are considered equal to other null dates.
   */
  sameDate(first: D | null, second: D | null): boolean {
    if (first && second) {
      let firstValid = this.isValid(first);
      let secondValid = this.isValid(second);
      if (firstValid && secondValid) {
        return !this.compareDate(first, second);
      }
      return firstValid == secondValid;
    }
    return first == second;
  }

  /**
   * Clamp the given date between min and max dates.
   * @param date The date to clamp.
   * @param min The minimum value to allow. If null or omitted no min is enforced.
   * @param max The maximum value to allow. If null or omitted no max is enforced.
   * @returns `min` if `date` is less than `min`, `max` if date is greater than `max`,
   *     otherwise `date`.
   */
  clampDate(date: D, min?: D | null, max?: D | null): D {
    if (min && this.compareDate(date, min) < 0) {
      return min;
    }
    if (max && this.compareDate(date, max) > 0) {
      return max;
    }
    return date;
  }
}