// Copyright 2017-2020 the Short Unique ID authors. All rights reserved. Apache 2.0 license.
import version from './version.ts';

type Ranges = {
  digits: number[],
  lowerCase: number[],
  upperCase: number[],
};

/**
 * ```js
 * {
 *   dictionary: ['z', 'a', 'p', 'h', 'o', 'd', ...],
 *   skipShuffle: false,
 *   debug: false,
 *   length: 6,
 * }
 * ```
 */
type Options = {
  /** User-defined character dictionary */
  dictionary: string[],

  /** If true, sequentialUUID use the dictionary in the given order */
  shuffle: boolean,

  /** If true the instance will console.log useful info */
  debug: boolean,

  /** From 1 to infinity, the length you wish your UUID to be */
  length: number,
};

/**
 * 6 was chosen as the default UUID length since for most cases
 * it will be more than aptly suitable to provide millions of UUIDs
 * with a very low probability of producing a duplicate UUID.
 *
 * For example, with a dictionary including digits from 0 to 9,
 * as well as the alphabet from a to z both in UPPER and lower case,
 * the probability of generating a duplicate in 1,000,000 rounds
 * is ~0.00000002, or about 1 in 50,000,000.
 */
const DEFAULT_UUID_LENGTH: number = 6;

const DIGIT_FIRST_ASCII: number = 48;
const DIGIT_LAST_ASCII: number = 58;
const ALPHA_LOWER_FIRST_ASCII: number = 97;
const ALPHA_LOWER_LAST_ASCII: number = 123;
const ALPHA_UPPER_FIRST_ASCII: number = 65;
const ALPHA_UPPER_LAST_ASCII: number = 91;

const DICT_RANGES: Ranges = {
  digits: [DIGIT_FIRST_ASCII, DIGIT_LAST_ASCII],
  lowerCase: [ALPHA_LOWER_FIRST_ASCII, ALPHA_LOWER_LAST_ASCII],
  upperCase: [ALPHA_UPPER_FIRST_ASCII, ALPHA_UPPER_LAST_ASCII],
};

const DEFAULT_OPTIONS: Options = {
  dictionary: [],
  shuffle: true,
  debug: false,
  length: DEFAULT_UUID_LENGTH,
};

/**
 * Generate random or sequential UUID of any length.
 *
 * ### Use as module
 *
 * ```js
 * // Deno (web module) Import
 * import ShortUniqueId from 'https://cdn.jsdelivr.net/npm/short-unique-id@latest/short_uuid/mod.ts';
 * // ES6 Import
 * import ShortUniqueId from 'short-unique-id';
 * //or Node.js require
 * const ShortUniqueId = require('short-unique-id');
 *
 * //Instantiate
 * const uid = new ShortUniqueId();
 *
 * // Random UUID
 * console.log(uid());
 *
 * // Sequential UUID
 * console.log(uid.seq());
 * ```
 *
 * ### Use in browser
 *
 * ```html
 * <!-- Import -->
 * <script src="https://cdn.jsdelivr.net/npm/short-unique-id@latest/dist/short-unique-id.min.js"></script>
 *
 * <!-- Usage -->
 * <script>
 *   // Instantiate
 *   var uid = new ShortUniqueId();
 *
 *   // Random UUID
 *   document.write(uid());
 *
 *   // Sequential UUID
 *   document.write(uid.seq());
 * </script>
 * ```
 *
 * ### Options
 *
 * Options can be passed when instantiating `uid`:
 *
 * ```js
 * const options = { ... };
 *
 * const uid = new ShortUniqueId(options);
 * ```
 *
 * For more information take a look at the [Options type definition](/globals.html#options).
 */
class ShortUniqueId extends Function {
  counter: number;

  debug: boolean;

  dict: string[];

  version: string;

  dictIndex: number = 0;

  dictRange: number[] =[];

  lowerBound: number = 0;

  upperBound: number = 0;

  dictLength: number = 0;

  uuidLength: number;

  /* tslint:disable consistent-return */
  protected log(...args: any[]): void {
    const finalArgs = [...args];
    finalArgs[0] = `[short-unique-id] ${args[0]}`;
    /* tslint:disable no-console */
    if (this.debug === true) {
      if (typeof console !== 'undefined' && console !== null) {
        return console.log(...finalArgs);
      }
    }
    /* tslint:enable no-console */
  }
  /* tslint:enable consistent-return */

  constructor(argOptions: Partial<Options> = {}) {
    super('...args', 'return this.randomUUID(...args)');

    const options: Options = {
      ...DEFAULT_OPTIONS,
      ...argOptions as Partial<Options>,
    };

    this.counter = 0;
    this.debug = false;
    this.dict = [];
    this.version = version;

    const {
      dictionary: userDict,
      shuffle,
      length,
    } = options;

    this.uuidLength = length;

    if (userDict && userDict.length > 1) {
      this.setDictionary(userDict);
    } else {
      let i;

      this.dictIndex = i = 0;

      Object.keys(DICT_RANGES).forEach((rangeType: any) => {
        const rangeTypeKey : keyof Ranges = rangeType as keyof Ranges;

        this.dictRange = DICT_RANGES[rangeTypeKey];

        this.lowerBound = this.dictRange[0];
        this.upperBound = this.dictRange[1];

        for (
          this.dictIndex = i = this.lowerBound;
          this.lowerBound <= this.upperBound ? i < this.upperBound : i > this.upperBound;
          this.dictIndex = this.lowerBound <= this.upperBound ? i += 1 : i -= 1
        ) {
          this.dict.push(String.fromCharCode(this.dictIndex));
        }
      });
    }

    if (shuffle) {
      // Shuffle Dictionary for removing selection bias.
      const PROBABILITY = 0.5;
      this.setDictionary(this.dict.sort(() => Math.random() - PROBABILITY));
    } else {
      this.setDictionary(this.dict);
    }

    this.debug = options.debug;
    this.log(this.dict);
    this.log((`Generator instantiated with Dictionary Size ${this.dictLength}`));

    const instance = this.bind(this);
    Object.getOwnPropertyNames(this).forEach((prop: string) => {
      if (
        !(
          /arguments|caller|callee|length|name|prototype/
        ).test(prop)
      ) {
        const propKey = prop as keyof ShortUniqueId;
        instance[prop] = this[propKey];
      }
    });

    return instance;
  }

  /** Change the dictionary after initialization. */
  setDictionary(dictionary: string[]): void {
    this.dict = dictionary;

    // Cache Dictionary Length for future usage.
    this.dictLength = this.dict.length;// Resets internal counter.
    this.counter = 0;
  }

  seq(): string {
    return this.sequentialUUID();
  }

  /**
   * Generates UUID based on internal counter that's incremented after each ID generation.
   * @alias `const uid = new ShortUniqueId(); uid.seq();`
   */
  sequentialUUID(): string {
    let counterDiv: number;
    let counterRem: number;
    let id: string = '';

    counterDiv = this.counter;

    /* tslint:disable no-constant-condition */
    while (true) {
      counterRem = counterDiv % this.dictLength;
      counterDiv = Math.trunc(counterDiv / this.dictLength);
      id += this.dict[counterRem];
      if (counterDiv === 0) {
        break;
      }
    }
    /* tslint:enable no-constant-condition */
    this.counter += 1;

    return id;
  }

  /**
   * Generates UUID by creating each part randomly.
   * @alias `const uid = new ShortUniqueId(); uid(uuidLength: number);`
   */
  randomUUID(uuidLength: number = this.uuidLength || DEFAULT_UUID_LENGTH): string {
    let id: string;
    let randomPartIdx: number;
    let j: number;
    let idIndex: number;

    if ((uuidLength === null || typeof uuidLength === 'undefined') || uuidLength < 1) {
      throw new Error('Invalid UUID Length Provided');
    }

    // Generate random ID parts from Dictionary.
    id = '';
    for (
      idIndex = j = 0;
      0 <= uuidLength ? j < uuidLength : j > uuidLength;
      idIndex = 0 <= uuidLength ? j += 1: j -= 1
    ) {
      randomPartIdx = parseInt(
        (Math.random() * this.dictLength).toFixed(0),
        10,
      ) % this.dictLength;
      id += this.dict[randomPartIdx];
    }

    // Return random generated ID.
    return id;
  }

  /**
   * Calculates total number of possible UUIDs.
   *
   * Given that:
   *
   * - `H` is the total number of possible UUIDs
   * - `n` is the number of unique characters in the dictionary
   * - `l` is the UUID length
   *
   * Then `H` is defined as `n` to the power of `l`:
   *
   * ![](https://render.githubusercontent.com/render/math?math=%5CHuge%20H=n%5El)
   *
   * This function returns `H`.
   */
  availableUUIDs(uuidLength: number = this.uuidLength): number {
    return parseFloat(
      Math.pow([...new Set(this.dict)].length, uuidLength).toFixed(0),
    );
  }

  /**
   * Calculates approximate number of hashes before first collision.
   *
   * Given that:
   *
   * - `H` is the total number of possible UUIDs, or in terms of this library,
   * the result of running `availableUUIDs()`
   * - the expected number of values we have to choose before finding the
   * first collision can be expressed as the quantity `Q(H)`
   *
   * Then `Q(H)` can be approximated as the square root of the of the product
   * of half of pi times `H`:
   *
   * ![](https://render.githubusercontent.com/render/math?math=%5CHuge%20Q(H)%5Capprox%5Csqrt%7B%5Cfrac%7B%5Cpi%7D%7B2%7DH%7D)
   *
   * This function returns `Q(H)`.
   */
  approxMaxBeforeCollision(rounds: number = this.availableUUIDs(this.uuidLength)): number {
    return parseFloat(
      Math.sqrt((Math.PI / 2) * rounds).toFixed(20),
    );
  }

  /**
   * Calculates probability of generating duplicate UUIDs (a collision) in a
   * given number of UUID generation rounds.
   *
   * Given that:
   *
   * - `r` is the maximum number of times that `randomUUID()` will be called,
   * or better said the number of _rounds_
   * - `H` is the total number of possible UUIDs, or in terms of this library,
   * the result of running `availableUUIDs()`
   *
   * Then the probability of collision `p(r; H)` can be approximated as the result
   * of dividing the square root of the of the product of half of pi times `H` by `H`:
   *
   * ![](https://render.githubusercontent.com/render/math?math=%5CHuge%20p(r%3B%20H)%5Capprox%5Cfrac%7B%5Csqrt%7B%5Cfrac%7B%5Cpi%7D%7B2%7Dr%7D%7D%7BH%7D)
   *
   * This function returns `p(r; H)`.
   *
   * (Useful if you are wondering _"If I use this lib and expect to perform at most
   * `r` rounds of UUID generations, what is the probability that I will hit a duplicate UUID?"_.)
   */
  collisionProbability(
    rounds: number = this.availableUUIDs(this.uuidLength),
    uuidLength: number = this.uuidLength,
  ): number {
    return parseFloat(
      (
        this.approxMaxBeforeCollision(rounds) / this.availableUUIDs(uuidLength)
      ).toFixed(20),
    );
  }

  /**
   * Calculate a "uniqueness" score (from 0 to 1) of UUIDs based on size of
   * dictionary and chosen UUID length.
   *
   * Given that:
   *
   * - `H` is the total number of possible UUIDs, or in terms of this library,
   * the result of running `availableUUIDs()`
   * - `Q(H)` is the approximate number of hashes before first collision,
   * or in terms of this library, the result of running `approxMaxBeforeCollision()`
   *
   * Then `uniqueness` can be expressed as the additive inverse of the probability of
   * generating a "word" I had previously generated (a duplicate) at any given iteration
   * up to the the total number of possible UUIDs expressed as the quotiend of `Q(H)` and `H`:
   *
   * ![](https://render.githubusercontent.com/render/math?math=%5CHuge%201-%5Cfrac%7BQ(H)%7D%7BH%7D)
   *
   * (Useful if you need a value to rate the "quality" of the combination of given dictionary
   * and UUID length. The closer to 1, higher the uniqueness and thus better the quality.)
   */
  uniqueness(rounds: number = this.availableUUIDs(this.uuidLength)): number {
    const score = parseFloat(
      (1 - (
        this.approxMaxBeforeCollision(rounds) / rounds
      )).toFixed(20),
    );
    return (
      score > 1
    ) ? (
      1
    ) : (
      (score < 0) ? 0 : score
    );
  }

  /**
   * Return the version of this module.
   */
  getVersion(): string {
    return this.version;
  }
}

export default ShortUniqueId;