<?php
/** DomFramework
  * @package domframework
  * @author Dominique Fournier <dominique@fournier38.fr>
  */

/** Create a diff from two strings, array or files
  * The output is compatible with "patch" command.
  */
class xdiff
{
  /** The name of file1
    */
  private $filename1 = "Original";

  /** The name of file2
    */
  private $filename2 = "New";

 /** The timestamp for file1
   */
  private $file1Time;

 /** The timestamp for file2
   */
  private $file2Time;

  /** The output requested
    */
  private $output = null;

  /** The constructor allow to choose the output.
    * @param string $output The output mode [normal|unified]
    */
  public function __construct ($output = "normal")
  // {{{
  {
    if (! method_exists ($this, "display".ucfirst ($output)))
      throw new \Exception ("Invalid output requested to xdiff", 406);
    $this->output = "display".ucfirst ($output);
    $this->file1Time = date ("Y-m-d H:i:s.u000 O");
    $this->file2Time = date ("Y-m-d H:i:s.u001 O");
  }
  // }}}

  /** Compute the differences between two strings $string1 and $string2
    * @param string $string1 The first string to compare
    * @param string $string2 The second string to compare
    */
  public function diff ($string1, $string2)
  // {{{
  {
    if (! is_string ($string1))
      throw new \Exception (
        "Invalid string1 provided to diff method : not a string", 406);
    if (! is_string ($string2))
      throw new \Exception (
        "Invalid string2 provided to diff method : not a string", 406);
    return $this->diffArray (
      preg_split ("#(.*\\R)#", $string1, -1,
        PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY),
      preg_split ("#(.*\\R)#", $string2, -1,
        PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY));
  }
  // }}}

  /** Compute the differences between two files $file1 and $file2
    * @param string $file1 The first file to use to compare
    * @param string $file2 The second file to use to compare
    */
  public function diffFile ($file1, $file2)
  // {{{
  {
    if (! is_string ($file1))
      throw new \Exception (
        "Invalid file1 provided to diff method : not a string", 406);
    if (! is_string ($file2))
      throw new \Exception (
        "Invalid file2 provided to diff method : not a string", 406);
    if (! file_exists ($file1))
      throw new \Exception (
        "Invalid file1 provided to diff method : file don't exists", 406);
    if (! file_exists ($file2))
      throw new \Exception (
        "Invalid file2 provided to diff method : file don't exists", 406);
    if (! is_readable ($file1))
      throw new \Exception (
        "Invalid file1 provided to diff method : file is not readable", 406);
    if (! is_readable ($file2))
      throw new \Exception (
        "Invalid file2 provided to diff method : file is not readable", 406);
    $this->filename1 = $file1;
    $this->filename2 = $file2;
    $this->file1Time = date ("Y-m-d H:i:s.u000 O",
       filemtime ($this->filename1));
    $this->file2Time = date ("Y-m-d H:i:s.u001 O",
       filemtime ($this->filename2));
    return $this->diff (file_get_contents ($file1),
                        file_get_contents ($file2));
  }
  // }}}

  /** Compute the differences between two arrays $array1 and $array2
    * @param array $array1 The first array to compare
    * @param array $array2 The second array to compare
    */
  public function diffArray ($array1, $array2)
  // {{{
  {
    $diff = $this->computeArray ($array1, $array2);
    $method = $this->output;
    return $this->$method ($diff);
  }
  // }}}

  /** Compute the differences between two arrays $array1 and $array2
    * @param array $array1 The first array to compare
    * @param array $array2 The second array to compare
    */
  final public function computeArray ($array1, $array2)
  // {{{
  {
    if (! is_array ($array1))
      throw new \Exception (
        "Invalid array1 provided to diffArray method : not a array", 406);
    if (! is_array ($array2))
      throw new \Exception (
        "Invalid array2 provided to diffArray method : not a array", 406);
    $diff = array ();
    $i = 0; // $i is the index for $array1
    $j = 0; // $j is the index for $array2
    while ($i < count ($array1) || $j < count ($array2))
    {
      $chunk1 = array ();
      $chunk2 = array ();
      if (key_exists ($i, $array1) && key_exists ($j, $array2) &&
          $array1[$i] === $array2[$j])
      {
        //   EQUAL
        while (key_exists ($i, $array1) && key_exists ($j, $array2) &&
               $array1[$i] === $array2[$j])
        {
          $chunk1[] = $array1[$i];
          $i++;
          $j++;
        }
        $diff[] = array ("type"       => "Equal",
                         "startLine1" => 1 + $i - count ($chunk1),
                         "endLine1"   => $i,
                         "startLine2" => 1 + $j - count ($chunk1),
                         "endLine2"   => $j,
                         "length"     => count ($chunk1),
                         "chunk"      => $chunk1);

        continue;
      }
      // Generate the chunks
      $lcs = $this->lcs ($array1, $array2, $i, $j);
      if ($lcs === "")
      {
        while ($i < count ($array1))
        {
          if ($array1[$i] === $lcs)
            break;
          $chunk1[] = $array1[$i];
          $i++;
          $lcs = $this->lcs ($array1, $array2, $i, $j);
        }
        while ($j < count ($array2))
        {
          if ($array2[$j] === $lcs)
            break;
          $chunk2[] = $array2[$j];
          $j++;
          $lcs = $this->lcs ($array1, $array2, $i, $j);
        }
      }
      else
      {
        while ($i < count ($array1))
        {
          if ($array1[$i] === $lcs)
            break;
          $chunk1[] = $array1[$i];
          $i++;
        }
        while ($j < count ($array2))
        {
          if ($array2[$j] === $lcs)
            break;
          $chunk2[] = $array2[$j];
          $j++;
        }
      }
      // Add the diffs by the chunks availability
      if (empty ($chunk1) && ! empty ($chunk2))
      {
        //   APPEND
        $diff[] = array ("type"       => "Append",
                         "startLine1" => $i,
                         "endLine1"   => $i,
                         "startLine2" => 1 + $j - count ($chunk2),
                         "endLine2"   => $j,
                         "length"     => count ($chunk2),
                         "chunk"      => $chunk2);
      }
      elseif (! empty ($chunk1) && empty ($chunk2))
      {
        //   DELETE
        $diff[] = array ("type"       => "Delete",
                         "startLine1" => 1 + $i - count ($chunk1),
                         "endLine1"   => $i,
                         "startLine2" => $j,
                         "endLine2"   => $j,
                         "length"     => count ($chunk1),
                         "chunk"      => $chunk1);
      }
      else
      {
        //   CHANGE ON BOTH ARRAY
        $diff[] = array ("type"       => "Change",
                         "startLine1" => 1 + $i - count ($chunk1),
                         "endLine1"   => $i,
                         "startLine2" => 1 + $j - count ($chunk2),
                         "endLine2"   => $j,
                         "length1"    => count ($chunk1),
                         "length2"    => count ($chunk2),
                         "chunk1"     => $chunk1,
                         "chunk2"     => $chunk2);
      }
    }
    return $diff;
  }
  // }}}

  /** Return a string like "diff -u"
    * @param array $diffArray The diff array analyzed by diffArray method
    * @return string
    */
  private function displayUnified ($diffArray)
  // {{{
  {
    $d = "";
    $i = 0 ;
    while ($i < count ($diffArray))
    {
      $diff = $diffArray[$i];
      $i++;
      if ($diff["type"] === "Equal")
        continue;


      if ($diff["type"] === "Append")
      {
        $info = "@@ -";
        $info .= $diff["startLine1"];
        $info .= ",0";
        $info .= " +";
        $info .= $diff["startLine2"];
        if ($diff["length"] !== 1)
          $info .= ",".$diff["length"];
        $info .= " @@\n";
        $d .= $info;
        $d .= "+".implode ("+", $diff["chunk"]);
      }
      elseif ($diff["type"] === "Delete")
      {
        $info = "@@ -";
        $info .= $diff["startLine1"];
        if ($diff["length"] !== 1)
          $info .= ",".$diff["length"];
        $info .= " +";
        $info .= $diff["startLine2"];
        $info .= ",0";
        $info .= " @@\n";
        $d .= $info;
        $d .= "-".implode ("-", $diff["chunk"]);
      }
      elseif ($diff["type"] === "Change")
      {
        $info = "@@ -";
        $info .= $diff["startLine1"];
        if ($diff["length1"] !== 1)
          $info .= ",".$diff["length1"];
        $info .= " +";
        $info .= $diff["startLine2"];
        if ($diff["length2"] !== 1)
          $info .= ",".$diff["length2"];
        $info .= " @@\n";
        $d .= $info;
        $d .= "-".implode ("-", $diff["chunk1"]);
        $d .= "+".implode ("+", $diff["chunk2"]);
      }
      else
        throw new \Exception ("Invalid Chunk Type : ".$diff["type"]);
    }
    if ($d === "")
      return $d;
    $e  = "--- $this->filename1 $this->file1Time\n";
    $e .= "+++ $this->filename2 $this->file2Time\n";
    return $e.$d;
  }
  // }}}

  /** Return a string like "diff" without parameter
    * @param array $diffArray The diff array analyzed by diffArray method
    * @return string
    */
  private function displayNormal ($diffArray)
  // {{{
  {
    $d = "";
    $i = 0 ;
    while ($i < count ($diffArray))
    {
      $diff = $diffArray[$i];
      $i++;
      if ($diff["type"] === "Equal")
        continue;
      $info = $diff["startLine1"];
      if ($diff["startLine1"] !== $diff["endLine1"])
        $info .= ",".$diff["endLine1"];
      $info .= "%s";
      $info .= $diff["startLine2"];
      if ($diff["startLine2"] !== $diff["endLine2"])
        $info .= ",".$diff["endLine2"];
      $info .= "\n";
      if ($diff["type"] === "Append")
      {
        $d .= sprintf ($info, "a");
        $d .= "> ".implode ("> ", $diff["chunk"]);
      }
      elseif ($diff["type"] === "Delete")
      {
        $d .= sprintf ($info, "d");
        $d .= "< ".implode ("< ", $diff["chunk"]);
      }
      elseif ($diff["type"] === "Change")
      {
        $d .= sprintf ($info, "c");
        $d .= "< ".implode ("< ", $diff["chunk1"]);
        $d .= "---\n";
        $d .= "> ".implode ("> ", $diff["chunk2"]);
      }
      else
        throw new \Exception ("Invalid Chunk Type : ".$diff["type"]);
    }
    return $d;
  }
  // }}}

  /** This function return the next common part between both arrays starting at
    * position $i for $array1 and $j for array2
    * Return empty string if no common lines was found
    * @return string
    */
  private function lcs ($array1, $array2, $i, $j)
  // {{{
  {
    $found1 = false;
    $found2 = false;
    while ($i < count ($array1))
    {
      $tmp2 = $j;
      while ($tmp2 < count ($array2))
      {
        if ($array1[$i] === $array2[$tmp2] && trim ($array1[$i]) !== "")
        {
          $found1 = true;
          break 2;
        }
        $tmp2++;
      }
      $i++;
    }
    while ($j < count ($array2))
    {
      $tmp1 = $i;
      while ($tmp1 < count ($array1))
      {
        if ($array2[$j] === $array1[$tmp1] && trim ($array2[$j]) !== "")
        {
          $found2 = true;
          break 2;
        }
        $tmp1++;
      }
      $j++;
    }
    if (! $found1 || ! $found2)
      return "";
    if ($tmp1 - $i < $tmp2 - $j)
    {
      return "";
    }
    return $array1[$i];
  }
  // }}}
}