russoedu / sequential-id-generator

 * Generator (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Generator) function

 * (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*) that produces a sequence of IDs.

 *

 * The sequence is baed on a list of characters (_sequence_ parameter) and has the lenght based on an initial ID (_initialOrLength_ parameter when

 * a string is passed) or on a length o characters (_initialOrLength_ parameter when a number is passed).

 *

 * A generator function can be iterated with a 'for of', that will return the next ID for each iteration or can be called using "next()", that

 * will return an object like { value: <the ID>, done: <boolean that is true when the sequence is finished> }.

 * @param initialOrLength The __initial ID string__ if you want to __start the generation from a certain point__ or the __length of the ID__ to

 * __start from the first ID__. (default = 5)

 *

 * Example: _initialOrLength = '00'_ will produce a __sequence from '01' on__. The passed current ID is skipped.

 * Example: _initialOrLength = 2_ will __start from '00'__, as the sequence will start from the beginning of the _sequence_ with the specified length.

 * @param sequence The string with the sequence of characters to produce the IDs. The order of the characters mather to the result.

 * (default = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ')

 * @example const code = idGenerator('28')

 * code.next() // { value: '29', done: false }

 * code.next() // { value: '2A', done: false }

 * code.next() // { value: '2B', done: false }

 * @example const code = idGenerator('ZZ')

 * code.next() // { value: undefined, done: true }

 * @example const code = idGenerator(2, '01')

 * code.next() // { value: '00', done: false }

 * code.next() // { value: '01', done: false }

 * code.next() // { value: '10', done: false }

 * code.next() // { value: '11', done: false }

 * code.next() // { value: undefined, done: true }

 * @example const code = idGenerator('4', '0123456')

 * for (const str of code) {

 *    console.log(str)

 * } // 5, 6

 * @example const code = idGenerator(1, '0123456')

 * for (const str of code) {

 *    console.log(str)

 * } // 0, 1, 2, 4, 5, 6

 */

export default function sequentialIdGenerator (initialOrLength: string | number = 5, sequence = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'): Generator<string, void, unknown> {

  if (initialOrLength === 0 || initialOrLength === '') {

    console.error('initialOrLength must be bigger than 0 and can\'t be an empty string')

    throw new Error('initialOrLength must be bigger than 0 and can\'t be an empty string')

  }

  if (typeof initialOrLength === 'string') {

    for (let index = 0; index < initialOrLength.length; index++) {

      const char = initialOrLength[index]

      if (!sequence.includes(char)) {

        console.error('initialOrLength contains an ID with characters that couldn\'t be found in the sequence')

        throw new Error('initialOrLength contains an ID with characters that couldn\'t be found in the sequence')

      }

    }

  }

  return generator(initialOrLength, sequence)

}

}

/**

 * Generates the next ID

 * @param id The current id

 * @param sequence The string with the sequence of characters to produce the IDs. The order of the characters mather to the result.

 */

function nextId (id: string, sequence: string): string {

  let index = id.length - 1

  let nextId = ''

  let rest = 0

  while (index >= 0) {

    // Character is added for the last char and if there is a rest from previus chars

    if (index === id.length - 1 || rest) {

      const increment = incrementChar(id[index], sequence)

      nextId = increment.nextChar + nextId

      rest = increment.rest

    } else {

      nextId = id[index] + nextId

      rest = 0

    }

    index--

  }

  return nextId

}

/**

 * Increment the character, returning the "rest" in case the character is the last in the sequence

 * @param char The character to be incremented

 * @param sequence The sequence of characters

 */

function incrementChar (char: string, sequence: string) {

  if (sequence.indexOf(char) === sequence.length - 1) {

    return {

      nextChar: sequence[0],

      rest:     1,

    }

  } else {

    return {

      nextChar: sequence[sequence.indexOf(char) + 1],

      rest:     0,

    }

  }

}