/**
 * @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, ɵisObservable as isObservable, ɵisPromise as isPromise} from '@angular/core';
import {forkJoin, from, Observable} from 'rxjs';
import {map} from 'rxjs/operators';

import {AsyncValidator, AsyncValidatorFn, ValidationErrors, Validator, ValidatorFn} from './directives/validators';
import {AbstractControl} from './model';

function isEmptyInputValue(value: any): boolean {
  // we don't check for string here so it also works with arrays
  return value == null || value.length === 0;
}

function hasValidLength(value: any): boolean {
  // non-strict comparison is intentional, to check for both `null` and `undefined` values
  return value != null && typeof value.length === 'number';
}

/**
 * @description
 * An `InjectionToken` for registering additional synchronous validators used with
 * `AbstractControl`s.
 *
 * 一个 `InjectionToken`，用于注册额外的同步验证器，供 `AbstractControl` 使用。
 *
 * @see `NG_ASYNC_VALIDATORS`
 *
 * @usageNotes
 *
 * ### Providing a custom validator
 *
 * ### 提供自定义验证器
 *
 * The following example registers a custom validator directive. Adding the validator to the
 * existing collection of validators requires the `multi: true` option.
 *
 * 下面的例子注册了一个自定义验证器指令。要把该验证器添加到现存的验证器集合中，需要使用 `multi: true` 选项。
 *
 * ```typescript
 * @Directive({
 *   selector: '[customValidator]',
 *   providers: [{provide: NG_VALIDATORS, useExisting: CustomValidatorDirective, multi: true}]
 * })
 * class CustomValidatorDirective implements Validator {
 *   validate(control: AbstractControl): ValidationErrors | null {
 *     return { 'custom': true };
 *   }
 * }
 * ```
 *
 * @publicApi
 */
export const NG_VALIDATORS = new InjectionToken<Array<Validator|Function>>('NgValidators');

/**
 * @description
 * An `InjectionToken` for registering additional asynchronous validators used with
 * `AbstractControl`s.
 *
 * 一个 `InjectionToken`，用于注册额外的异步验证器，供 `AbstractControl` 使用。
 *
 * @see `NG_VALIDATORS`
 *
 * @publicApi
 */
export const NG_ASYNC_VALIDATORS =
    new InjectionToken<Array<Validator|Function>>('NgAsyncValidators');

/**
 * A regular expression that matches valid e-mail addresses.
 *
 * At a high level, this regexp matches e-mail addresses of the format `local-part@tld`, where:
 * - `local-part` consists of one or more of the allowed characters (alphanumeric and some
 *   punctuation symbols).
 * - `local-part` cannot begin or end with a period (`.`).
 * - `local-part` cannot be longer than 64 characters.
 * - `tld` consists of one or more `labels` separated by periods (`.`). For example `localhost` or
 *   `foo.com`.
 * - A `label` consists of one or more of the allowed characters (alphanumeric, dashes (`-`) and
 *   periods (`.`)).
 * - A `label` cannot begin or end with a dash (`-`) or a period (`.`).
 * - A `label` cannot be longer than 63 characters.
 * - The whole address cannot be longer than 254 characters.
 *
 * ## Implementation background
 *
 * This regexp was ported over from AngularJS (see there for git history):
 * https://github.com/angular/angular.js/blob/c133ef836/src/ng/directive/input.js#L27
 * It is based on the
 * [WHATWG version](https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address) with
 * some enhancements to incorporate more RFC rules (such as rules related to domain names and the
 * lengths of different parts of the address). The main differences from the WHATWG version are:
 *   - Disallow `local-part` to begin or end with a period (`.`).
 *   - Disallow `local-part` length to exceed 64 characters.
 *   - Disallow total address length to exceed 254 characters.
 *
 * See [this commit](https://github.com/angular/angular.js/commit/f3f5cf72e) for more details.
 */
const EMAIL_REGEXP =
    /^(?=.{1,254}$)(?=.{1,64}@)[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)*@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/;

/**
 * @description
 * Provides a set of built-in validators that can be used by form controls.
 *
 * 提供一组内置验证器，可用于各种表单控件。
 *
 * A validator is a function that processes a `FormControl` or collection of
 * controls and returns an error map or null. A null map means that validation has passed.
 *
 * 验证器就是一个函数，它可以处理单个 `FormControl` 或一组控件，并返回一个错误映射表（map）或 null。null 表示验证已通过了。
 *
 * @see [Form Validation](/guide/form-validation)
 *
 * [表单验证](/guide/form-validation)
 * @publicApi
 */
export class Validators {
  /**
   * @description
   * Validator that requires the control's value to be greater than or equal to the provided number.
   * The validator exists only as a function and not as a directive.
   *
   * 此验证器要求控件的值大于或等于指定的数字。
   * 它只有函数形式，没有指令形式。
   *
   * @usageNotes
   *
   * ### Validate against a minimum of 3
   *
   * ### 验证至少为 3
   *
   * ```typescript
   * const control = new FormControl(2, Validators.min(3));
   *
   * console.log(control.errors); // {min: {min: 3, actual: 2}}
   * ```
   *
   * @returns A validator function that returns an error map with the
   * `min` property if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `min` 属性的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static min(min: number): ValidatorFn {
    return (control: AbstractControl): ValidationErrors|null => {
      if (isEmptyInputValue(control.value) || isEmptyInputValue(min)) {
        return null;  // don't validate empty values to allow optional controls
      }
      const value = parseFloat(control.value);
      // Controls with NaN values after parsing should be treated as not having a
      // minimum, per the HTML forms spec: https://www.w3.org/TR/html5/forms.html#attr-input-min
      return !isNaN(value) && value < min ? {'min': {'min': min, 'actual': control.value}} : null;
    };
  }

  /**
   * @description
   * Validator that requires the control's value to be less than or equal to the provided number.
   * The validator exists only as a function and not as a directive.
   *
   * 此验证器要求控件的值小于等于指定的数字。
   * 它只有函数形式，没有指令形式。
   *
   * @usageNotes
   *
   * ### Validate against a maximum of 15
   *
   * ### 验证最大为 15
   *
   * ```typescript
   * const control = new FormControl(16, Validators.max(15));
   *
   * console.log(control.errors); // {max: {max: 15, actual: 16}}
   * ```
   *
   * @returns A validator function that returns an error map with the
   * `max` property if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `max` 属性的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static max(max: number): ValidatorFn {
    return (control: AbstractControl): ValidationErrors|null => {
      if (isEmptyInputValue(control.value) || isEmptyInputValue(max)) {
        return null;  // don't validate empty values to allow optional controls
      }
      const value = parseFloat(control.value);
      // Controls with NaN values after parsing should be treated as not having a
      // maximum, per the HTML forms spec: https://www.w3.org/TR/html5/forms.html#attr-input-max
      return !isNaN(value) && value > max ? {'max': {'max': max, 'actual': control.value}} : null;
    };
  }

  /**
   * @description
   * Validator that requires the control have a non-empty value.
   *
   * 此验证器要求控件具有非空值。
   *
   * @usageNotes
   *
   * ### Validate that the field is non-empty
   *
   * ### 验证该字段不是空的
   *
   * ```typescript
   * const control = new FormControl('', Validators.required);
   *
   * console.log(control.errors); // {required: true}
   * ```
   *
   * @returns An error map with the `required` property
   * if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `required` 属性的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static required(control: AbstractControl): ValidationErrors|null {
    return isEmptyInputValue(control.value) ? {'required': true} : null;
  }

  /**
   * @description
   * Validator that requires the control's value be true. This validator is commonly
   * used for required checkboxes.
   *
   * 此验证器要求控件的值为真。它通常用来验证检查框。
   *
   * @usageNotes
   *
   * ### Validate that the field value is true
   *
   * ### 验证字段值为真
   *
   * ```typescript
   * const control = new FormControl('', Validators.requiredTrue);
   *
   * console.log(control.errors); // {required: true}
   * ```
   *
   * @returns An error map that contains the `required` property
   * set to `true` if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `required` 属性、值为 `true` 的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static requiredTrue(control: AbstractControl): ValidationErrors|null {
    return control.value === true ? null : {'required': true};
  }

  /**
   * @description
   * Validator that requires the control's value pass an email validation test.
   *
   * 此验证器要求控件的值能通过 email 格式验证。
   *
   * Tests the value using a [regular
   * expression](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions)
   * pattern suitable for common usecases. The pattern is based on the definition of a valid email
   * address in the [WHATWG HTML
   * specification](https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address) with
   * some enhancements to incorporate more RFC rules (such as rules related to domain names and the
   * lengths of different parts of the address).
   *
   * 使用适合普通用例的[正则表达式模式测试值](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions)。该模式基于 [WHATWG HTML 规范](https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address)中有效电子邮件地址的定义，并进行了一些增强以支持更多的 RFC 规则（例如与域名相关的规则以及地址不同部分的长度）。
   *
   * The differences from the WHATWG version include:
   *
   * 与 WHATWG 版本的区别包括：
   *
   * - Disallow `local-part` (the part before the `@` symbol) to begin or end with a period (`.`).
   *
   *   禁止 `local-part`（`@` 符号前面的部分）以句点（ `.` ）开头或结尾。
   *
   * - Disallow `local-part` to be longer than 64 characters.
   *
   *   不允许 `local-part` 超过 64 个字符。
   *
   * - Disallow the whole address to be longer than 254 characters.
   *
   *   不允许整个地址超过 254 个字符。
   *
   * If this pattern does not satisfy your business needs, you can use `Validators.pattern()` to
   * validate the value against a different pattern.
   *
   * 如果此模式不能满足你的业务需求，则可以使用 `Validators.pattern()` 来针对其他模式验证值。
   *
   * @usageNotes
   *
   * ### Validate that the field matches a valid email pattern
   *
   * ### 验证该字段匹配有效的 email 格式。
   *
   * ```typescript
   * const control = new FormControl('bad@', Validators.email);
   *
   * console.log(control.errors); // {email: true}
   * ```
   *
   * @returns An error map with the `email` property
   * if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `email` 属性的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static email(control: AbstractControl): ValidationErrors|null {
    if (isEmptyInputValue(control.value)) {
      return null;  // don't validate empty values to allow optional controls
    }
    return EMAIL_REGEXP.test(control.value) ? null : {'email': true};
  }

  /**
   * @description
   * Validator that requires the length of the control's value to be greater than or equal
   * to the provided minimum length. This validator is also provided by default if you use the
   * the HTML5 `minlength` attribute. Note that the `minLength` validator is intended to be used
   * only for types that have a numeric `length` property, such as strings or arrays. The
   * `minLength` validator logic is also not invoked for values when their `length` property is 0
   * (for example in case of an empty string or an empty array), to support optional controls. You
   * can use the standard `required` validator if empty values should not be considered valid.
   *
   * 此验证器要求控件值的长度大于等于所指定的最小长度。当使用 HTML5 的 `minlength` 属性时，此验证器也会生效。
   *
   * @usageNotes
   *
   * ### Validate that the field has a minimum of 3 characters
   *
   * ### 验证该字段至少有 3 个字符
   *
   * ```typescript
   * const control = new FormControl('ng', Validators.minLength(3));
   *
   * console.log(control.errors); // {minlength: {requiredLength: 3, actualLength: 2}}
   * ```
   *
   * ```html
   * <input minlength="5">
   * ```
   *
   * @returns A validator function that returns an error map with the
   * `minlength` if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `minlength` 属性的映射表（map），否则为 `null`。
   *
   *
   * @see `updateValueAndValidity()`
   *
   */
  static minLength(minLength: number): ValidatorFn {
    return (control: AbstractControl): ValidationErrors|null => {
      if (isEmptyInputValue(control.value) || !hasValidLength(control.value)) {
        // don't validate empty values to allow optional controls
        // don't validate values without `length` property
        return null;
      }

      return control.value.length < minLength ?
          {'minlength': {'requiredLength': minLength, 'actualLength': control.value.length}} :
          null;
    };
  }

  /**
   * @description
   * Validator that requires the length of the control's value to be less than or equal
   * to the provided maximum length. This validator is also provided by default if you use the
   * the HTML5 `maxlength` attribute. Note that the `maxLength` validator is intended to be used
   * only for types that have a numeric `length` property, such as strings or arrays.
   *
   * 此验证器要求控件值的长度小于等于所指定的最大长度。当使用 HTML5 的 `maxlength` 属性时，此验证器也会生效。
   *
   * @usageNotes
   *
   * ### Validate that the field has maximum of 5 characters
   *
   * ### 验证该字段最多具有 5 个字符
   *
   * ```typescript
   * const control = new FormControl('Angular', Validators.maxLength(5));
   *
   * console.log(control.errors); // {maxlength: {requiredLength: 5, actualLength: 7}}
   * ```
   *
   * ```html
   * <input maxlength="5">
   * ```
   *
   * @returns A validator function that returns an error map with the
   * `maxlength` property if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `maxlength` 属性的映射表（map），否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static maxLength(maxLength: number): ValidatorFn {
    return (control: AbstractControl): ValidationErrors|null => {
      return hasValidLength(control.value) && control.value.length > maxLength ?
          {'maxlength': {'requiredLength': maxLength, 'actualLength': control.value.length}} :
          null;
    };
  }

  /**
   * @description
   * Validator that requires the control's value to match a regex pattern. This validator is also
   * provided by default if you use the HTML5 `pattern` attribute.
   *
   * 此验证器要求控件的值匹配某个正则表达式。当使用 HTML5 的 `pattern` 属性时，它也会生效。
   *
   * @usageNotes
   *
   * ### Validate that the field only contains letters or spaces
   *
   * ### 验证该字段只包含字母或空格
   *
   * ```typescript
   * const control = new FormControl('1', Validators.pattern('[a-zA-Z ]*'));
   *
   * console.log(control.errors); // {pattern: {requiredPattern: '^[a-zA-Z ]*$', actualValue: '1'}}
   * ```
   *
   * ```html
   * <input pattern="[a-zA-Z ]*">
   * ```
   *
   * ### Pattern matching with the global or sticky flag
   *
   * ### 带有全局或粘性（sticky）标志的匹配模式
   *
   * `RegExp` objects created with the `g` or `y` flags that are passed into `Validators.pattern`
   * can produce different results on the same input when validations are run consecutively. This is
   * due to how the behavior of `RegExp.prototype.test` is
   * specified in [ECMA-262](https://tc39.es/ecma262/#sec-regexpbuiltinexec)
   * (`RegExp` preserves the index of the last match when the global or sticky flag is used).
   * Due to this behavior, it is recommended that when using
   * `Validators.pattern` you **do not** pass in a `RegExp` object with either the global or sticky
   * flag enabled.
   *
   * 当要连续运行验证时，使用传递给 `Validators.pattern` 的 `g` 或 `y` 标志创建的 `RegExp` 对象可以在同一输入上产生不同的结果。这是由于在 [ECMA-262 中](https://tc39.es/ecma262/#sec-regexpbuiltinexec)为 `RegExp.prototype.test` 定义的行为（`RegExp` 保留了最后一个匹配项的索引）。由于这种现象，建议你使用 `Validators.pattern` 时**不要**传入启用了全局或粘性标志的 `RegExp`。
   *
   * ```typescript
   * // Not recommended (since the `g` flag is used)
   * const controlOne = new FormControl('1', Validators.pattern(/foo/g));
   *
   * // Good
   * const controlTwo = new FormControl('1', Validators.pattern(/foo/));
   * ```
   *
   * @param pattern A regular expression to be used as is to test the values, or a string.
   * If a string is passed, the `^` character is prepended and the `$` character is
   * appended to the provided string (if not already present), and the resulting regular
   * expression is used to test the values.
   *
   * 用于测试值的正则表达式或字符串。如果传递了字符串，会在它前面追加 `^` 字符，并在后面追加 `$` 字符（如果尚不存在），然后使用所得的正则表达式测试这些值。
   *
   * @returns A validator function that returns an error map with the
   * `pattern` property if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回一个带有 `pattern` 属性的映射表（map），否则为 `null`。
   *
   *
   * @see `updateValueAndValidity()`
   *
   */
  static pattern(pattern: string|RegExp): ValidatorFn {
    if (!pattern) return Validators.nullValidator;
    let regex: RegExp;
    let regexStr: string;
    if (typeof pattern === 'string') {
      regexStr = '';

      if (pattern.charAt(0) !== '^') regexStr += '^';

      regexStr += pattern;

      if (pattern.charAt(pattern.length - 1) !== '$') regexStr += '$';

      regex = new RegExp(regexStr);
    } else {
      regexStr = pattern.toString();
      regex = pattern;
    }
    return (control: AbstractControl): ValidationErrors|null => {
      if (isEmptyInputValue(control.value)) {
        return null;  // don't validate empty values to allow optional controls
      }
      const value: string = control.value;
      return regex.test(value) ? null :
                                 {'pattern': {'requiredPattern': regexStr, 'actualValue': value}};
    };
  }

  /**
   * @description
   * Validator that performs no operation.
   *
   * 此验证器什么也不做。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static nullValidator(control: AbstractControl): ValidationErrors|null {
    return null;
  }

  /**
   * @description
   * Compose multiple validators into a single function that returns the union
   * of the individual error maps for the provided control.
   *
   * 把多个验证器合并成一个函数，它会返回指定控件的各个错误映射表的并集。
   *
   * @returns A validator function that returns an error map with the
   * merged error maps of the validators if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回各个验证器所返回错误对象的一个并集，否则为 `null`。
   *
   *
   * @see `updateValueAndValidity()`
   *
   */
  static compose(validators: null): null;
  static compose(validators: (ValidatorFn|null|undefined)[]): ValidatorFn|null;
  static compose(validators: (ValidatorFn|null|undefined)[]|null): ValidatorFn|null {
    if (!validators) return null;
    const presentValidators: ValidatorFn[] = validators.filter(isPresent) as any;
    if (presentValidators.length == 0) return null;

    return function(control: AbstractControl) {
      return mergeErrors(executeValidators<ValidatorFn>(control, presentValidators));
    };
  }

  /**
   * @description
   * Compose multiple async validators into a single function that returns the union
   * of the individual error objects for the provided control.
   *
   * 把多个异步验证器合并成一个函数，它会返回指定控件的各个错误映射表的并集。
   *
   * @returns A validator function that returns an error map with the
   * merged error objects of the async validators if the validation check fails, otherwise `null`.
   *
   * 如果验证失败，则此验证器函数返回各异步验证器所返回错误对象的一个并集，否则为 `null`。
   *
   * @see `updateValueAndValidity()`
   *
   */
  static composeAsync(validators: (AsyncValidatorFn|null)[]): AsyncValidatorFn|null {
    if (!validators) return null;
    const presentValidators: AsyncValidatorFn[] = validators.filter(isPresent) as any;
    if (presentValidators.length == 0) return null;

    return function(control: AbstractControl) {
      const observables =
          executeValidators<AsyncValidatorFn>(control, presentValidators).map(toObservable);
      return forkJoin(observables).pipe(map(mergeErrors));
    };
  }
}

function isPresent(o: any): boolean {
  return o != null;
}

export function toObservable(r: any): Observable<any> {
  const obs = isPromise(r) ? from(r) : r;
  if (!(isObservable(obs)) && (typeof ngDevMode === 'undefined' || ngDevMode)) {
    throw new Error(`Expected validator to return Promise or Observable.`);
  }
  return obs;
}

function mergeErrors(arrayOfErrors: (ValidationErrors|null)[]): ValidationErrors|null {
  let res: {[key: string]: any} = {};

  // Not using Array.reduce here due to a Chrome 80 bug
  // https://bugs.chromium.org/p/chromium/issues/detail?id=1049982
  arrayOfErrors.forEach((errors: ValidationErrors|null) => {
    res = errors != null ? {...res!, ...errors} : res!;
  });

  return Object.keys(res).length === 0 ? null : res;
}

type GenericValidatorFn = (control: AbstractControl) => any;

function executeValidators<V extends GenericValidatorFn>(
    control: AbstractControl, validators: V[]): ReturnType<V>[] {
  return validators.map(validator => validator(control));
}

function isValidatorFn<V>(validator: V|Validator|AsyncValidator): validator is V {
  return !(validator as Validator).validate;
}

/**
 * Given the list of validators that may contain both functions as well as classes, return the list
 * of validator functions (convert validator classes into validator functions). This is needed to
 * have consistent structure in validators list before composing them.
 *
 * @param validators The set of validators that may contain validators both in plain function form
 *     as well as represented as a validator class.
 */
export function normalizeValidators<V>(validators: (V|Validator|AsyncValidator)[]): V[] {
  return validators.map(validator => {
    return isValidatorFn<V>(validator) ?
        validator :
        ((c: AbstractControl) => validator.validate(c)) as unknown as V;
  });
}

/**
 * Merges synchronous validators into a single validator function (combined using
 * `Validators.compose`).
 */
export function composeValidators(validators: Array<Validator|ValidatorFn>): ValidatorFn|null {
  return validators != null ? Validators.compose(normalizeValidators<ValidatorFn>(validators)) :
                              null;
}

/**
 * Merges asynchronous validators into a single validator function (combined using
 * `Validators.composeAsync`).
 */
export function composeAsyncValidators(validators: Array<AsyncValidator|AsyncValidatorFn>):
    AsyncValidatorFn|null {
  return validators != null ?
      Validators.composeAsync(normalizeValidators<AsyncValidatorFn>(validators)) :
      null;
}

/**
 * Merges raw control validators with a given directive validator and returns the combined list of
 * validators as an array.
 */
export function mergeValidators<V>(controlValidators: V|V[]|null, dirValidator: V): V[] {
  if (controlValidators === null) return [dirValidator];
  return Array.isArray(controlValidators) ? [...controlValidators, dirValidator] :
                                            [controlValidators, dirValidator];
}

/**
 * Retrieves the list of raw synchronous validators attached to a given control.
 */
export function getControlValidators(control: AbstractControl): ValidatorFn|ValidatorFn[]|null {
  return (control as any)._rawValidators as ValidatorFn | ValidatorFn[] | null;
}

/**
 * Retrieves the list of raw asynchronous validators attached to a given control.
 */
export function getControlAsyncValidators(control: AbstractControl): AsyncValidatorFn|
    AsyncValidatorFn[]|null {
  return (control as any)._rawAsyncValidators as AsyncValidatorFn | AsyncValidatorFn[] | null;
}