import { type DeepPartial } from '@silverhand/essentials';
import { z } from 'zod';

/** Password policy configuration type. */
export type PasswordPolicy = {
  /** Policy about password length. */
  length: {
    /** Minimum password length. */
    min: number;
    /** Maximum password length. */
    max: number;
  };
  /**
   * Policy about password character types. Four types of characters are supported:
   *
   * - Lowercase letters (a-z).
   * - Uppercase letters (A-Z).
   * - Digits (0-9).
   * - Symbols ({@link PasswordPolicyChecker.symbols}).
   */
  characterTypes: {
    /** Minimum number of character types. Range: 1-4. */
    min: number;
  };
  /** Policy about what passwords to reject. */
  rejects: {
    /** Whether to reject passwords that are pwned. */
    pwned: boolean;
    /** Whether to reject passwords that like '123456' or 'aaaaaa'. */
    repetitionAndSequence: boolean;
    /** Whether to reject passwords that include current user information. */
    userInfo: boolean;
    /** Whether to reject passwords that include specific words. */
    words: string[];
  };
};

/** Password policy configuration guard. */
export const passwordPolicyGuard = z.object({
  length: z
    .object({
      min: z.number().int().min(1).default(8),
      max: z.number().int().min(1).default(256),
    })
    .default({}),
  characterTypes: z
    .object({
      min: z.number().int().min(1).max(4).optional().default(1),
    })
    .default({}),
  rejects: z
    .object({
      pwned: z.boolean().default(true),
      repetitionAndSequence: z.boolean().default(true),
      userInfo: z.boolean().default(true),
      words: z.string().array().default([]),
    })
    .default({}),
}) satisfies z.ZodType<PasswordPolicy, z.ZodTypeDef, DeepPartial<PasswordPolicy>>;

/** The code of why a password is rejected. */
export type PasswordRejectionCode =
  | 'too_short'
  | 'too_long'
  | 'character_types'
  | 'unsupported_characters'
  | 'pwned'
  | 'restricted.repetition'
  | 'restricted.sequence'
  | 'restricted.user_info'
  | 'restricted.words';

/** A password issue that does not meet the policy. */
export type PasswordIssue<Code extends PasswordRejectionCode = PasswordRejectionCode> = {
  /** Issue code. */
  code: `password_rejected.${Code}`;
  /** Interpolation data for the issue message. */
  interpolation?: Record<string, unknown>;
};

/** User information to check. */
export type UserInfo = Partial<{
  name: string;
  username: string;
  email: string;
  phoneNumber: string;
}>;

/**
 * The class for checking if a password meets the policy. The policy is defined as
 * {@link PasswordPolicy}.
 *
 * @example
 * ```ts
 * const checker = new PasswordPolicyChecker({
 *   length: { min: 8, max: 256 },
 *   characterTypes: { min: 2 },
 *   rejects: { pwned: true, repetitionAndSequence: true, words: [] },
 * });
 *
 * const issues = await checker.check('123456');
 * console.log(issues);
 * // [
 * //   { code: 'password_rejected.too_short' },
 * //   { code: 'password_rejected.character_types', interpolation: { min: 2 } },
 * //   { code: 'password_rejected.pwned' },
 * //   { code: 'password_rejected.restricted.sequence' },
 * // ]
 * ```
 */
export class PasswordPolicyChecker {
  static symbols = Object.freeze('!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ ' as const);

  /** A set of characters that are considered as sequential. */
  static sequence = Object.freeze([
    '0123456789',
    'abcdefghijklmnopqrstuvwxyz',
    'qwertyuiop',
    'asdfghjkl',
    'zxcvbnm',
    '1qaz',
    '2wsx',
    '3edc',
    '4rfv',
    '5tgb',
    '6yhn',
    '7ujm',
    '8ik',
    '9ol',
  ] as const);

  /** The length threshold for checking repetition and sequence. */
  static repetitionAndSequenceThreshold = 3 as const;
  /**
   * If the password contains more than such number of characters that are not
   * in the restricted phrases, it will be accepted.
   */
  static restrictedPhrasesTolerance = 3 as const;

  /** Get the length threshold for checking restricted phrases. */
  protected static getRestrictedPhraseThreshold(password: string): number {
    const { restrictedPhrasesTolerance } = PasswordPolicyChecker;

    return Math.max(1, password.length - restrictedPhrasesTolerance);
  }

  public readonly policy: PasswordPolicy;

  constructor(
    policy: DeepPartial<PasswordPolicy>,
    /** The Web Crypto API to use. By default, the global `crypto.subtle` will be used. */
    protected readonly subtle: SubtleCrypto = crypto.subtle
  ) {
    this.policy = passwordPolicyGuard.parse(policy);
  }

  /**
   * Check if a password meets all the policy requirements.
   *
   * @param password - Password to check.
   * @param userInfo - User information to check. Required if the policy
   * requires to reject passwords that include user information.
   * @returns An array of issues. If the password meets the policy, an empty array will be returned.
   * @throws TypeError - If the policy requires to reject passwords that include user information
   * but the user information is not provided.
   */
  /* eslint-disable @silverhand/fp/no-let, @silverhand/fp/no-mutation, @silverhand/fp/no-mutating-methods */
  async check(password: string, userInfo?: UserInfo): Promise<PasswordIssue[]> {
    const issues: PasswordIssue[] = this.fastCheck(password);

    if (this.policy.rejects.pwned && (await this.hasBeenPwned(password))) {
      issues.push({
        code: 'password_rejected.pwned',
      });
    }

    // `hashArray[i]` indicates whether the `i`th character violates the restriction.
    // We'll gradually set the value to `1` if needed.
    // The algorithm time complexity should be O(n^2), but it's fast enough for a password.
    const hashArray = Array.from<0 | 1>({ length: password.length }).fill(0);
    const issueCodes = new Set<PasswordRejectionCode>();
    const { repetitionAndSequence, words, userInfo: rejectUserInfo } = this.policy.rejects;
    const rejectWords = words.length > 0;

    const fillHashArray = (startIndex: number, length: number, code: PasswordRejectionCode) => {
      if (length <= 0) {
        return;
      }

      for (let i = startIndex; i < startIndex + length; i += 1) {
        hashArray[i] = 1;
      }
      issueCodes.add(code);
    };

    for (let i = 0; i < password.length; i += 1) {
      const sliced = password.slice(i);

      if (repetitionAndSequence) {
        fillHashArray(i, this.repetitionLength(sliced), 'restricted.repetition');
        fillHashArray(i, this.sequenceLength(sliced), 'restricted.sequence');
      }

      if (rejectWords) {
        fillHashArray(i, this.wordLength(sliced), 'restricted.words');
      }

      if (rejectUserInfo) {
        if (!userInfo) {
          throw new TypeError('User information data is required to check user information.');
        }

        fillHashArray(i, this.userInfoLength(sliced, userInfo), 'restricted.user_info');
      }
    }

    return hashArray.reduce<number>((total, current) => total + current, 0) >
      PasswordPolicyChecker.getRestrictedPhraseThreshold(password)
      ? [
          ...issues,
          ...[...issueCodes].map<PasswordIssue>((code) => ({ code: `password_rejected.${code}` })),
        ]
      : issues;
  }
  /* eslint-enable @silverhand/fp/no-let, @silverhand/fp/no-mutation, @silverhand/fp/no-mutating-methods */

  /**
   * Perform a fast check to see if the password passes the basic requirements.
   * Only the length and character types will be checked.
   *
   * This method is used for frontend validation.
   *
   * @param password - Password to check.
   * @returns Whether the password passes the basic requirements.
   */
  /* eslint-disable @silverhand/fp/no-mutating-methods */
  fastCheck(password: string) {
    const issues: PasswordIssue[] = [];

    if (password.length < this.policy.length.min) {
      issues.push({
        code: 'password_rejected.too_short',
        interpolation: { min: this.policy.length.min },
      });
    } else if (password.length > this.policy.length.max) {
      issues.push({
        code: 'password_rejected.too_long',
        interpolation: { max: this.policy.length.max },
      });
    }

    const characterTypes = this.checkCharTypes(password);
    if (characterTypes === 'unsupported') {
      issues.push({
        code: 'password_rejected.unsupported_characters',
      });
    } else if (!characterTypes) {
      issues.push({
        code: 'password_rejected.character_types',
        interpolation: { min: this.policy.characterTypes.min },
      });
    }

    return issues;
  }
  /* eslint-enable @silverhand/fp/no-mutating-methods */

  /**
   * Check if the given password contains enough character types.
   *
   * @param password - Password to check.
   * @returns Whether the password contains enough character types; or `'unsupported'`
   * if the password contains unsupported characters.
   */
  checkCharTypes(password: string): boolean | 'unsupported' {
    const characterTypes = new Set<string>();
    for (const char of password) {
      if (char >= 'a' && char <= 'z') {
        characterTypes.add('lowercase');
      } else if (char >= 'A' && char <= 'Z') {
        characterTypes.add('uppercase');
      } else if (char >= '0' && char <= '9') {
        characterTypes.add('digits');
      } else if (PasswordPolicyChecker.symbols.includes(char)) {
        characterTypes.add('symbols');
      } else {
        return 'unsupported';
      }
    }

    return characterTypes.size >= this.policy.characterTypes.min;
  }

  /**
   * Check if the given password has been pwned.
   *
   * @param password - Password to check.
   * @returns Whether the password has been pwned.
   */
  async hasBeenPwned(password: string): Promise<boolean> {
    const hash = await this.subtle.digest('SHA-1', new TextEncoder().encode(password));
    const hashHex = Array.from(new Uint8Array(hash))
      .map((binary) => binary.toString(16).padStart(2, '0'))
      .join('');
    const hashPrefix = hashHex.slice(0, 5);
    const hashSuffix = hashHex.slice(5);
    const response = await fetch(`https://api.pwnedpasswords.com/range/${hashPrefix}`);
    const text = await response.text();
    const hashes = text.split('\n');
    const found = hashes.some((hex) => hex.toLowerCase().startsWith(hashSuffix));

    return found;
  }

  /**
   * Get the length of the repetition at the beginning of the given string.
   * For example, `repetitionLength('aaaaa')` will return `5`.
   *
   * If the length is less than {@link PasswordPolicyChecker.repetitionAndSequenceThreshold},
   * `0` will be returned.
   */
  /* eslint-disable @silverhand/fp/no-let, @silverhand/fp/no-mutation */
  repetitionLength(password: string): number {
    const { repetitionAndSequenceThreshold } = PasswordPolicyChecker;
    const firstChar = password[0]?.toLowerCase();
    let length = 0;

    for (const char of password) {
      if (char.toLowerCase() === firstChar) {
        length += 1;
      } else {
        break;
      }
    }

    return length >= repetitionAndSequenceThreshold ? length : 0;
  }
  /* eslint-enable @silverhand/fp/no-let, @silverhand/fp/no-mutation */

  /**
   * Get the length of the user information at the beginning of the given string.
   * For example, `userInfoLength('silverhand', { username: 'silverhand' })` will return `10`.
   *
   * For multiple matches, the longest length will be returned.
   */
  // eslint-disable-next-line complexity
  userInfoLength(password: string, userInfo: UserInfo): number {
    const lowercased = password.toLowerCase();
    const { name, username, email, phoneNumber } = userInfo;
    // eslint-disable-next-line @silverhand/fp/no-let
    let length = 0;

    const updateLength = (newLength: number) => {
      if (newLength > length) {
        // eslint-disable-next-line @silverhand/fp/no-mutation
        length = newLength;
      }
    };

    if (name) {
      const joined = name.replaceAll(/\s+/g, '');

      // The original name should be the longest string, so we check it first.
      if (lowercased.startsWith(name.toLowerCase())) {
        updateLength(name.length);
      } else {
        if (lowercased.startsWith(joined.toLowerCase())) {
          updateLength(joined.length);
        }

        for (const word of name.split(' ')) {
          if (lowercased.startsWith(word.toLowerCase())) {
            updateLength(word.length);
          }
        }
      }
    }

    if (username && lowercased.startsWith(username.toLowerCase())) {
      updateLength(username.length);
    }

    if (email) {
      const emailPrefix = email.split('@')[0];
      if (emailPrefix && lowercased.startsWith(emailPrefix.toLowerCase())) {
        updateLength(emailPrefix.length);
      }
    }

    if (phoneNumber && lowercased.startsWith(phoneNumber)) {
      updateLength(phoneNumber.length);
    }

    return length;
  }

  /**
   * Get the length of the word that matches the word list at the beginning of the given string.
   *
   * For multiple matches, the longest length will be returned.
   */
  /* eslint-disable @silverhand/fp/no-let, @silverhand/fp/no-mutation */
  wordLength(password: string): number {
    const sliced = password.toLowerCase();
    let length = 0;

    for (const word of this.policy.rejects.words) {
      if (sliced.startsWith(word.toLowerCase()) && word.length > length) {
        length = word.length;
      }
    }

    return length;
  }
  /* eslint-enable @silverhand/fp/no-let, @silverhand/fp/no-mutation */

  /**
   * Get the length of the sequence at the beginning of the given string.
   * For example, `sequenceLength('12345')` will return `5`.
   *
   * If the length is less than {@link PasswordPolicyChecker.repetitionAndSequenceThreshold},
   * `0` will be returned.
   */
  /* eslint-disable @silverhand/fp/no-let, @silverhand/fp/no-mutation */
  sequenceLength(password: string): number {
    const { repetitionAndSequenceThreshold } = PasswordPolicyChecker;
    let value = '';
    let length = 0;

    for (const char of password) {
      if (!value || this.isSequential(value + char)) {
        value += char;
        length += 1;
      } else {
        break;
      }
    }

    return length >= repetitionAndSequenceThreshold ? length : 0;
  }
  /* eslint-enable @silverhand/fp/no-let, @silverhand/fp/no-mutation */

  /**
   * Check if the given string is sequential by iterating through the {@link PasswordPolicyChecker.sequence}.
   */
  protected isSequential(value: string): boolean {
    const { sequence } = PasswordPolicyChecker;
    const lowercased = value.toLowerCase();

    for (const seq of sequence) {
      // eslint-disable-next-line @silverhand/fp/no-mutating-methods -- created a new array before mutating
      if (seq.includes(lowercased) || [...seq].reverse().join('').includes(lowercased)) {
        return true;
      }
    }

    return false;
  }
}