<?php
namespace HTML5\Parser;

/**
 * The scanner.
 *
 * This scans over an input stream.
 */
class Scanner {
  const CHARS_HEX = 'abcdefABCDEF01234567890';
  const CHARS_ALNUM = 'abcdefAghijklmnopqrstuvwxyABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890';
  const CHARS_ALPHA = 'abcdefAghijklmnopqrstuvwxyABCDEFGHIJKLMNOPQRSTUVWXYZ';

  protected $is;

  // Flipping this to TRUE will give minisculely more debugging info.
  public $debug = FALSE;

  /**
   * Create a new Scanner.
   *
   * @param \HTML5\Parser\InputStream $input
   *   An InputStream to be scanned.
   */
  public function __construct($input) {
    $this->is = $input;
  }

  /**
   * Get the current position.
   *
   * @return int
   *   The current intiger byte position.
   */
  public function position() {
    return $this->is->key();
  }

  /**
   * Take a peek at the next character in the data.
   *
   * @return string
   *   The next character.
   */
  public function peek() {
    return $this->is->peek();
  }

  /**
   * Get the next character.
   * 
   * Note: This advances the pointer.
   *
   * @return string
   *   The next character.
   */
  public function next() {
    $this->is->next();
    if ($this->is->valid()) {
      if ($this->debug) fprintf(STDOUT, "> %s\n", $this->is->current());
      return $this->is->current();
    }
    return FALSE;
  }

  /**
   * Get the current character.
   *
   * Note, this does not advance the pointer.
   * 
   * @return string
   *   The current character.
   */
  public function current() {
    if ($this->is->valid()) {
      return $this->is->current();
    }
    return FALSE;
  }

  /**
   * Silently consume N chars.
   */
  public function consume($count = 1) {
    for ($i = 0; $i < $count; ++$i) {
      $this->next();
    }
  }

  /**
   * Unconsume some of the data. This moves the data pointer backwards.
   *
   * @param  int $howMany
   *   The number of characters to move the pointer back.
   */
  public function unconsume($howMany = 1) {
    $this->is->unconsume($howMany);
  }

  /**
   * Get the next group of that contains hex characters.
   *
   * Note, along with getting the characters the pointer in the data will be
   * moved as well.
   * 
   * @return string
   *   The next group that is hex characters.
   */
  public function getHex() {
    return $this->is->charsWhile(static::CHARS_HEX);
  }

  /**
   * Get the next group of characters that are ASCII Alpha characters.
   *
   * Note, along with getting the characters the pointer in the data will be
   * moved as well.
   * 
   * @return string
   *   The next group of ASCII alpha characters.
   */
  public function getAsciiAlpha() {
    return $this->is->charsWhile(static::CHARS_ALPHA);
  }

  /**
   * Get the next group of characters that are ASCII Alpha characters and numbers.
   *
   * Note, along with getting the characters the pointer in the data will be
   * moved as well.
   * 
   * @return string
   *   The next group of ASCII alpha characters and numbers.
   */
  public function getAsciiAlphaNum() {
    return $this->is->charsWhile(static::CHARS_ALNUM);
  }

  /**
   * Get the next group of numbers.
   *
   * Note, along with getting the characters the pointer in the data will be
   * moved as well.
   * 
   * @return string
   *   The next group of numbers.
   */
  public function getNumeric() {
    return $this->is->charsWhile('0123456789');
  }

  /**
   * Consume whitespace.
   *
   * Whitespace in HTML5 is: formfeed, tab, newline, space.
   */
  public function whitespace() {
    return $this->is->charsWhile("\n\t\f ");
  }

  /**
   * Returns the current line that is being consumed.
   *
   * @return int
   *   The current line number.
   */
  public function currentLine() {
    return $this->is->currentLine();
  }

  /**
   * Read chars until something in the mask is encountered.
   */
  public function charsUntil($mask) {
    return $this->is->charsUntil($mask);
  }
  /**
   * Read chars as long as the mask matches.
   */
  public function charsWhile($mask) {
    return $this->is->charsWhile($mask);
  }

  /**
   * Returns the current column of the current line that the tokenizer is at.
   *
   * Newlines are column 0. The first char after a newline is column 1.
   *
   * @return int
   *   The column number.
   */
  public function columnOffset() {
    return $this->is->columnOffset();
  }

  /**
   * Get all characters until EOF.
   *
   * This consumes characters until the EOF.
   *
   * @return int
   *   The number of characters remaining.
   */
  public function remainingChars() {
    return $this->is->remainingChars();
  }
}