'use strict';

const utils = require('./utils');

const {
  CHAR_ASTERISK,             /* * */
  CHAR_AT,                   /* @ */
  CHAR_BACKWARD_SLASH,       /* \ */
  CHAR_COMMA,                /* , */
  CHAR_DOT,                  /* . */
  CHAR_EXCLAMATION_MARK,     /* ! */
  CHAR_FORWARD_SLASH,        /* / */
  CHAR_LEFT_CURLY_BRACE,     /* { */
  CHAR_LEFT_PARENTHESES,     /* ( */
  CHAR_LEFT_SQUARE_BRACKET,  /* [ */
  CHAR_PLUS,                 /* + */
  CHAR_QUESTION_MARK,        /* ? */
  CHAR_RIGHT_CURLY_BRACE,    /* } */
  CHAR_RIGHT_PARENTHESES,    /* ) */
  CHAR_RIGHT_SQUARE_BRACKET /* ] */
} = require('./constants');

const isPathSeparator = code => {
  return code === CHAR_FORWARD_SLASH || code === CHAR_BACKWARD_SLASH;
};

/**
 * Quickly scans a glob pattern and returns an object with a handful of
 * useful properties, like `isGlob`, `path` (the leading non-glob, if it exists),
 * `glob` (the actual pattern), and `negated` (true if the path starts with `!`).
 *
 * ```js
 * const pm = require('picomatch');
 * console.log(pm.scan('foo/bar/*.js'));
 * { isGlob: true, input: 'foo/bar/*.js', base: 'foo/bar', glob: '*.js' }
 * ```
 * @param {String} `str`
 * @param {Object} `options`
 * @return {Object} Returns an object with tokens and regex source string.
 * @api public
 */

module.exports = (input, options) => {
  let opts = options || {};
  let length = input.length - 1;
  let index = -1;
  let start = 0;
  let lastIndex = 0;
  let isGlob = false;
  let backslashes = false;
  let negated = false;
  let braces = 0;
  let prev;
  let code;

  let braceEscaped = false;

  let eos = () => index >= length;
  let advance = () => {
    prev = code;
    return input.charCodeAt(++index);
  };

  while (index < length) {
    code = advance();
    let next;

    if (code === CHAR_BACKWARD_SLASH) {
      backslashes = true;
      next = advance();

      if (next === CHAR_LEFT_CURLY_BRACE) {
        braceEscaped = true;
      }
      continue;
    }

    if (braceEscaped === true || code === CHAR_LEFT_CURLY_BRACE) {
      braces++;

      while (!eos() && (next = advance())) {
        if (next === CHAR_BACKWARD_SLASH) {
          backslashes = true;
          next = advance();
          continue;
        }

        if (next === CHAR_LEFT_CURLY_BRACE) {
          braces++;
          continue;
        }

        if (!braceEscaped && next === CHAR_DOT && (next = advance()) === CHAR_DOT) {
          isGlob = true;
          break;
        }

        if (!braceEscaped && next === CHAR_COMMA) {
          isGlob = true;
          break;
        }

        if (next === CHAR_RIGHT_CURLY_BRACE) {
          braces--;
          if (braces === 0) {
            braceEscaped = false;
            break;
          }
        }
      }
    }

    if (code === CHAR_FORWARD_SLASH) {
      if (prev === CHAR_DOT && index === (start + 1)) {
        start += 2;
        continue;
      }

      lastIndex = index + 1;
      continue;
    }

    if (code === CHAR_ASTERISK) {
      isGlob = true;
      break;
    }

    if (code === CHAR_ASTERISK || code === CHAR_QUESTION_MARK) {
      isGlob = true;
      break;
    }

    if (code === CHAR_LEFT_SQUARE_BRACKET) {
      while (!eos() && (next = advance())) {
        if (next === CHAR_BACKWARD_SLASH) {
          backslashes = true;
          next = advance();
          continue;
        }

        if (next === CHAR_RIGHT_SQUARE_BRACKET) {
          isGlob = true;
          break;
        }
      }
    }

    let isExtglobChar = code === CHAR_PLUS
      || code === CHAR_AT
      || code === CHAR_EXCLAMATION_MARK;

    if (isExtglobChar && input.charCodeAt(index + 1) === CHAR_LEFT_PARENTHESES) {
      isGlob = true;
      break;
    }

    if (code === CHAR_EXCLAMATION_MARK && index === start) {
      negated = true;
      start++;
      continue;
    }

    if (code === CHAR_LEFT_PARENTHESES) {
      while (!eos() && (next = advance())) {
        if (next === CHAR_BACKWARD_SLASH) {
          backslashes = true;
          next = advance();
          continue;
        }

        if (next === CHAR_RIGHT_PARENTHESES) {
          isGlob = true;
          break;
        }
      }
    }

    if (isGlob) {
      break;
    }
  }

  let prefix = '';
  let orig = input;
  let base = input;
  let glob = '';

  if (start > 0) {
    prefix = input.slice(0, start);
    input = input.slice(start);
    lastIndex -= start;
  }

  if (base && isGlob === true && lastIndex > 0) {
    base = input.slice(0, lastIndex);
    glob = input.slice(lastIndex);
  } else if (isGlob === true) {
    base = '';
    glob = input;
  } else {
    base = input;
  }

  if (base && base !== '' && base !== '/' && base !== input) {
    if (isPathSeparator(base.charCodeAt(base.length - 1))) {
      base = base.slice(0, -1);
    }
  }

  if (opts.unescape === true) {
    if (glob) glob = utils.removeBackslashes(glob);

    if (base && backslashes === true) {
      base = utils.removeBackslashes(base);
    }
  }

  return { prefix, input: orig, base, glob, negated, isGlob };
};