"use strict"

const configurationError = require("./configurationError")
const isSingleLineString = require("./isSingleLineString")
const isWhitespace = require("./isWhitespace")

/**
 * Create a whitespaceChecker, which exposes the following functions:
 * - `before()`
 * - `beforeAllowingIndentation()`
 * - `after()`
 * - `afterOneOnly()`
 *
 * @param {"space"|"newline"} targetWhitespace - This is a keyword instead
 *   of the actual character (e.g. " ") in order to accommodate
 *   different styles of newline ("\n" vs "\r\n")
 * @param {
 *     "always"|"never"
 *     |"always-single-line"|"always-multi-line"
 *     | "never-single-line"|"never-multi-line"
 *   } expectation
 * @param {object} messages - An object of message functions;
 *   calling `before*()` or `after*()` and the `expectation` that is passed
 *   determines which message functions are required
 * @param {function} [messages.exectedBefore]
 * @param {function} [messages.rejectedBefore]
 * @param {function} [messages.expectedAfter]
 * @param {function} [messages.rejectedAfter]
 * @param {function} [messages.expectedBeforeSingleLine]
 * @param {function} [messages.rejectedBeforeSingleLine]
 * @param {function} [messages.expectedBeforeMultiLine]
 * @param {function} [messages.rejectedBeforeMultiLine]
 * @return {object} The checker, with its exposed checking functions
 */
module.exports = function (
  targetWhitespace/*: "space" | "newline"*/,
  expectation/*: "always" | "never" | "always-single-line"
    | "always-multi-line" | "never-single-line"|"never-multi-line"*/,
  messages/*: Object*/
)/*: {
  before: Function,
  beforeAllowingIndentation: Function,
  after: Function,
  afterOneOnly: Function
}*/ {
  // Keep track of active arguments in order to avoid passing
  // too much stuff around, making signatures long and confusing.
  // This variable gets reset anytime a checking function is called.
  let activeArgs

  /**
   * Check for whitespace *before* a character.
   *
   * @param {object} args - Named arguments object
   * @param {string} args.source - The source string
   * @param {number} args.index - The index of the character to check before
   * @param {function} args.err - If a violation is found, this callback
   *   will be invoked with the relevant warning message.
   *   Typically this callback will report() the violation.
   * @param {function} args.errTarget - If a violation is found, this string
   *   will be sent to the relevant warning message.
   * @param {string} [args.lineCheckStr] - Single- and multi-line checkers
   *   will use this string to determine whether they should proceed,
   *   i.e. if this string is one line only, single-line checkers will check,
   *   multi-line checkers will ignore.
   *   If none is passed, they will use `source`.
   * @param {boolean} [args.onlyOneChar=false] - Only check *one* character before.
   *   By default, "always-*" checks will look for the `targetWhitespace` one
   *   before and then ensure there is no whitespace two before. This option
   *   bypasses that second check.
   * @param {boolean} [args.allowIndentation=false] - Allow arbitrary indentation
   *   between the `targetWhitespace` (almost definitely a newline) and the `index`.
   *   With this option, the checker will see if a newline *begins* the whitespace before
   *   the `index`.
   */
  function before(args) {
    const source = args.source
    const index = args.index
    const err = args.err
    const errTarget = args.errTarget
    const lineCheckStr = args.lineCheckStr
    const onlyOneChar = args.onlyOneChar === undefined ? false : args.onlyOneChar
    const allowIndentation = args.allowIndentation === undefined ? false : args.allowIndentation

    activeArgs = { source, index, err, errTarget, onlyOneChar, allowIndentation }
    switch (expectation) {
      case "always":
        expectBefore()
        break
      case "never":
        rejectBefore()
        break
      case "always-single-line":
        if (!isSingleLineString(lineCheckStr || source)) {
          return
        }
        expectBefore(messages.expectedBeforeSingleLine)
        break
      case "never-single-line":
        if (!isSingleLineString(lineCheckStr || source)) {
          return
        }
        rejectBefore(messages.rejectedBeforeSingleLine)
        break
      case "always-multi-line":
        if (isSingleLineString(lineCheckStr || source)) {
          return
        }
        expectBefore(messages.expectedBeforeMultiLine)
        break
      case "never-multi-line":
        if (isSingleLineString(lineCheckStr || source)) {
          return
        }
        rejectBefore(messages.rejectedBeforeMultiLine)
        break
      default:
        throw configurationError(`Unknown expectation "${expectation}"`)
    }
  }

  /**
   * Check for whitespace *after* a character.
   *
   * Parameters are pretty much the same as for `before()`, above, just substitute
   * the word "after" for "before".
   */
  function after(args) {
    const source = args.source
    const index = args.index
    const err = args.err
    const errTarget = args.errTarget
    const lineCheckStr = args.lineCheckStr
    const onlyOneChar = args.onlyOneChar === undefined ? false : args.onlyOneChar

    activeArgs = { source, index, err, errTarget, onlyOneChar }
    switch (expectation) {
      case "always":
        expectAfter()
        break
      case "never":
        rejectAfter()
        break
      case "always-single-line":
        if (!isSingleLineString(lineCheckStr || source)) {
          return
        }
        expectAfter(messages.expectedAfterSingleLine)
        break
      case "never-single-line":
        if (!isSingleLineString(lineCheckStr || source)) {
          return
        }
        rejectAfter(messages.rejectedAfterSingleLine)
        break
      case "always-multi-line":
        if (isSingleLineString(lineCheckStr || source)) {
          return
        }
        expectAfter(messages.expectedAfterMultiLine)
        break
      case "never-multi-line":
        if (isSingleLineString(lineCheckStr || source)) {
          return
        }
        rejectAfter(messages.rejectedAfterMultiLine)
        break
      default:
        throw configurationError(`Unknown expectation "${expectation}"`)
    }
  }

  function beforeAllowingIndentation(obj) {
    before(Object.assign({}, obj, { allowIndentation: true }))
  }

  function expectBefore() {
    const messageFunc = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : messages.expectedBefore

    if (activeArgs.allowIndentation) {
      expectBeforeAllowingIndentation(messageFunc)
      return
    }

    const _activeArgs = activeArgs
    const source = _activeArgs.source,
      index = _activeArgs.index

    const oneCharBefore = source[index - 1]
    const twoCharsBefore = source[index - 2]

    if (!isValue(oneCharBefore)) {
      return
    }

    if (targetWhitespace === "space" && oneCharBefore === " ") {
      if (activeArgs.onlyOneChar || !isWhitespace(twoCharsBefore)) {
        return
      }
    }

    activeArgs.err(messageFunc(activeArgs.errTarget ? activeArgs.errTarget : source[index]))
  }

  function expectBeforeAllowingIndentation() {
    const messageFunc = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : messages.expectedBefore
    const _activeArgs2 = activeArgs
    const source = _activeArgs2.source,
      index = _activeArgs2.index,
      err = _activeArgs2.err

    const expectedChar = function () {
      if (targetWhitespace === "newline") {
        return "\n"
      }
    }()
    let i = index - 1
    while (source[i] !== expectedChar) {
      if (source[i] === "\t" || source[i] === " ") {
        i--
        continue
      }
      err(messageFunc(activeArgs.errTarget ? activeArgs.errTarget : source[index]))
      return
    }
  }

  function rejectBefore() {
    const messageFunc = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : messages.rejectedBefore
    const _activeArgs3 = activeArgs
    const source = _activeArgs3.source,
      index = _activeArgs3.index

    const oneCharBefore = source[index - 1]

    if (isValue(oneCharBefore) && isWhitespace(oneCharBefore)) {
      activeArgs.err(messageFunc(activeArgs.errTarget ? activeArgs.errTarget : source[index]))
    }
  }

  function afterOneOnly(obj) {
    after(Object.assign({}, obj, { onlyOneChar: true }))
  }

  function expectAfter() {
    const messageFunc = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : messages.expectedAfter
    const _activeArgs4 = activeArgs
    const source = _activeArgs4.source,
      index = _activeArgs4.index

    const oneCharAfter = source[index + 1]
    const twoCharsAfter = source[index + 2]

    if (!isValue(oneCharAfter)) {
      return
    }

    if (targetWhitespace === "newline") {
      // If index is followed by a Windows CR-LF ...
      if (oneCharAfter === "\r" && twoCharsAfter === "\n") {
        if (activeArgs.onlyOneChar || !isWhitespace(source[index + 3])) {
          return
        }
      }

      // If index is followed by a Unix LF ...
      if (oneCharAfter === "\n") {
        if (activeArgs.onlyOneChar || !isWhitespace(twoCharsAfter)) {
          return
        }
      }
    }

    if (targetWhitespace === "space" && oneCharAfter === " ") {
      if (activeArgs.onlyOneChar || !isWhitespace(twoCharsAfter)) {
        return
      }
    }

    activeArgs.err(messageFunc(activeArgs.errTarget ? activeArgs.errTarget : source[index]))
  }

  function rejectAfter() {
    const messageFunc = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : messages.rejectedAfter
    const _activeArgs5 = activeArgs
    const source = _activeArgs5.source,
      index = _activeArgs5.index

    const oneCharAfter = source[index + 1]

    if (isValue(oneCharAfter) && isWhitespace(oneCharAfter)) {
      activeArgs.err(messageFunc(activeArgs.errTarget ? activeArgs.errTarget : source[index]))
    }
  }

  return {
    before,
    beforeAllowingIndentation,
    after,
    afterOneOnly,
  }
}

function isValue(x) {
  return x !== undefined && x !== null
}