<?php
/**
 * Diff API: WP_Text_Diff_Renderer_Table class
 *
 * @package WordPress
 * @subpackage Diff
 * @since 4.7.0
 */

/**
 * Table renderer to display the diff lines.
 *
 * @since 2.6.0
 * @uses Text_Diff_Renderer Extends
 */
class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {

	/**
	 * @see Text_Diff_Renderer::_leading_context_lines
	 * @var int
	 * @since 2.6.0
	 */
	public $_leading_context_lines = 10000;

	/**
	 * @see Text_Diff_Renderer::_trailing_context_lines
	 * @var int
	 * @since 2.6.0
	 */
	public $_trailing_context_lines = 10000;

	/**
	 * Threshold for when a diff should be saved or omitted.
	 *
	 * @var float
	 * @since 2.6.0
	 */
	protected $_diff_threshold = 0.6;

	/**
	 * Inline display helper object name.
	 *
	 * @var string
	 * @since 2.6.0
	 */
	protected $inline_diff_renderer = 'WP_Text_Diff_Renderer_inline';

	/**
	 * Should we show the split view or not
	 *
	 * @var string
	 * @since 3.6.0
	 */
	protected $_show_split_view = true;

	protected $compat_fields = array( '_show_split_view', 'inline_diff_renderer', '_diff_threshold' );

	/**
	 * Caches the output of count_chars() in compute_string_distance()
	 *
	 * @var array
	 * @since 5.0.0
	 */
	protected $count_cache = array();

	/**
	 * Caches the difference calculation in compute_string_distance()
	 *
	 * @var array
	 * @since 5.0.0
	 */
	protected $difference_cache = array();

	/**
	 * Constructor - Call parent constructor with params array.
	 *
	 * This will set class properties based on the key value pairs in the array.
	 *
	 * @since 2.6.0
	 *
	 * @param array $params
	 */
	public function __construct( $params = array() ) {
		parent::__construct( $params );
		if ( isset( $params['show_split_view'] ) ) {
			$this->_show_split_view = $params['show_split_view'];
		}
	}

	/**
	 * @ignore
	 *
	 * @param string $header
	 * @return string
	 */
	public function _startBlock( $header ) {
		return '';
	}

	/**
	 * @ignore
	 *
	 * @param array  $lines
	 * @param string $prefix
	 */
	public function _lines( $lines, $prefix = ' ' ) {
	}

	/**
	 * @ignore
	 *
	 * @param string $line HTML-escape the value.
	 * @return string
	 */
	public function addedLine( $line ) {
		return "<td class='diff-addedline'><span aria-hidden='true' class='dashicons dashicons-plus'></span><span class='screen-reader-text'>" . __( 'Added:' ) . " </span>{$line}</td>";

	}

	/**
	 * @ignore
	 *
	 * @param string $line HTML-escape the value.
	 * @return string
	 */
	public function deletedLine( $line ) {
		return "<td class='diff-deletedline'><span aria-hidden='true' class='dashicons dashicons-minus'></span><span class='screen-reader-text'>" . __( 'Deleted:' ) . " </span>{$line}</td>";
	}

	/**
	 * @ignore
	 *
	 * @param string $line HTML-escape the value.
	 * @return string
	 */
	public function contextLine( $line ) {
		return "<td class='diff-context'><span class='screen-reader-text'>" . __( 'Unchanged:' ) . " </span>{$line}</td>";
	}

	/**
	 * @ignore
	 *
	 * @return string
	 */
	public function emptyLine() {
		return '<td>&nbsp;</td>';
	}

	/**
	 * @ignore
	 *
	 * @param array $lines
	 * @param bool  $encode
	 * @return string
	 */
	public function _added( $lines, $encode = true ) {
		$r = '';
		foreach ( $lines as $line ) {
			if ( $encode ) {
				$processed_line = htmlspecialchars( $line );

				/**
				 * Contextually filters a diffed line.
				 *
				 * Filters TextDiff processing of diffed line. By default, diffs are processed with
				 * htmlspecialchars. Use this filter to remove or change the processing. Passes a context
				 * indicating if the line is added, deleted or unchanged.
				 *
				 * @since 4.1.0
				 *
				 * @param string $processed_line The processed diffed line.
				 * @param string $line           The unprocessed diffed line.
				 * @param string $context        The line context. Values are 'added', 'deleted' or 'unchanged'.
				 */
				$line = apply_filters( 'process_text_diff_html', $processed_line, $line, 'added' );
			}

			if ( $this->_show_split_view ) {
				$r .= '<tr>' . $this->emptyLine() . $this->addedLine( $line ) . "</tr>\n";
			} else {
				$r .= '<tr>' . $this->addedLine( $line ) . "</tr>\n";
			}
		}
		return $r;
	}

	/**
	 * @ignore
	 *
	 * @param array $lines
	 * @param bool  $encode
	 * @return string
	 */
	public function _deleted( $lines, $encode = true ) {
		$r = '';
		foreach ( $lines as $line ) {
			if ( $encode ) {
				$processed_line = htmlspecialchars( $line );

				/** This filter is documented in wp-includes/wp-diff.php */
				$line = apply_filters( 'process_text_diff_html', $processed_line, $line, 'deleted' );
			}
			if ( $this->_show_split_view ) {
				$r .= '<tr>' . $this->deletedLine( $line ) . $this->emptyLine() . "</tr>\n";
			} else {
				$r .= '<tr>' . $this->deletedLine( $line ) . "</tr>\n";
			}
		}
		return $r;
	}

	/**
	 * @ignore
	 *
	 * @param array $lines
	 * @param bool  $encode
	 * @return string
	 */
	public function _context( $lines, $encode = true ) {
		$r = '';
		foreach ( $lines as $line ) {
			if ( $encode ) {
				$processed_line = htmlspecialchars( $line );

				/** This filter is documented in wp-includes/wp-diff.php */
				$line = apply_filters( 'process_text_diff_html', $processed_line, $line, 'unchanged' );
			}
			if ( $this->_show_split_view ) {
				$r .= '<tr>' . $this->contextLine( $line ) . $this->contextLine( $line ) . "</tr>\n";
			} else {
				$r .= '<tr>' . $this->contextLine( $line ) . "</tr>\n";
			}
		}
		return $r;
	}

	/**
	 * Process changed lines to do word-by-word diffs for extra highlighting.
	 *
	 * (TRAC style) sometimes these lines can actually be deleted or added rows.
	 * We do additional processing to figure that out
	 *
	 * @since 2.6.0
	 *
	 * @param array $orig
	 * @param array $final
	 * @return string
	 */
	public function _changed( $orig, $final ) {
		$r = '';

		/*
		 * Does the aforementioned additional processing:
		 * *_matches tell what rows are "the same" in orig and final. Those pairs will be diffed to get word changes.
		 * - match is numeric: an index in other column.
		 * - match is 'X': no match. It is a new row.
		 * *_rows are column vectors for the orig column and the final column.
		 * - row >= 0: an index of the $orig or $final array.
		 * - row < 0: a blank row for that column.
		 */
		list($orig_matches, $final_matches, $orig_rows, $final_rows) = $this->interleave_changed_lines( $orig, $final );

		// These will hold the word changes as determined by an inline diff.
		$orig_diffs  = array();
		$final_diffs = array();

		// Compute word diffs for each matched pair using the inline diff.
		foreach ( $orig_matches as $o => $f ) {
			if ( is_numeric( $o ) && is_numeric( $f ) ) {
				$text_diff = new Text_Diff( 'auto', array( array( $orig[ $o ] ), array( $final[ $f ] ) ) );
				$renderer  = new $this->inline_diff_renderer;
				$diff      = $renderer->render( $text_diff );

				// If they're too different, don't include any <ins> or <del>'s.
				if ( preg_match_all( '!(<ins>.*?</ins>|<del>.*?</del>)!', $diff, $diff_matches ) ) {
					// Length of all text between <ins> or <del>.
					$stripped_matches = strlen( strip_tags( implode( ' ', $diff_matches[0] ) ) );
					// Since we count length of text between <ins> or <del> (instead of picking just one),
					// we double the length of chars not in those tags.
					$stripped_diff = strlen( strip_tags( $diff ) ) * 2 - $stripped_matches;
					$diff_ratio    = $stripped_matches / $stripped_diff;
					if ( $diff_ratio > $this->_diff_threshold ) {
						continue; // Too different. Don't save diffs.
					}
				}

				// Un-inline the diffs by removing <del> or <ins>.
				$orig_diffs[ $o ]  = preg_replace( '|<ins>.*?</ins>|', '', $diff );
				$final_diffs[ $f ] = preg_replace( '|<del>.*?</del>|', '', $diff );
			}
		}

		foreach ( array_keys( $orig_rows ) as $row ) {
			// Both columns have blanks. Ignore them.
			if ( $orig_rows[ $row ] < 0 && $final_rows[ $row ] < 0 ) {
				continue;
			}

			// If we have a word based diff, use it. Otherwise, use the normal line.
			if ( isset( $orig_diffs[ $orig_rows[ $row ] ] ) ) {
				$orig_line = $orig_diffs[ $orig_rows[ $row ] ];
			} elseif ( isset( $orig[ $orig_rows[ $row ] ] ) ) {
				$orig_line = htmlspecialchars( $orig[ $orig_rows[ $row ] ] );
			} else {
				$orig_line = '';
			}

			if ( isset( $final_diffs[ $final_rows[ $row ] ] ) ) {
				$final_line = $final_diffs[ $final_rows[ $row ] ];
			} elseif ( isset( $final[ $final_rows[ $row ] ] ) ) {
				$final_line = htmlspecialchars( $final[ $final_rows[ $row ] ] );
			} else {
				$final_line = '';
			}

			if ( $orig_rows[ $row ] < 0 ) { // Orig is blank. This is really an added row.
				$r .= $this->_added( array( $final_line ), false );
			} elseif ( $final_rows[ $row ] < 0 ) { // Final is blank. This is really a deleted row.
				$r .= $this->_deleted( array( $orig_line ), false );
			} else { // A true changed row.
				if ( $this->_show_split_view ) {
					$r .= '<tr>' . $this->deletedLine( $orig_line ) . $this->addedLine( $final_line ) . "</tr>\n";
				} else {
					$r .= '<tr>' . $this->deletedLine( $orig_line ) . '</tr><tr>' . $this->addedLine( $final_line ) . "</tr>\n";
				}
			}
		}

		return $r;
	}

	/**
	 * Takes changed blocks and matches which rows in orig turned into which rows in final.
	 *
	 * @since 2.6.0
	 *
	 * @param array $orig  Lines of the original version of the text.
	 * @param array $final Lines of the final version of the text.
	 * @return array {
	 *     Array containing results of comparing the original text to the final text.
	 *
	 *     @type array $orig_matches  Associative array of original matches. Index == row
	 *                                number of `$orig`, value == corresponding row number
	 *                                of that same line in `$final` or 'x' if there is no
	 *                                corresponding row (indicating it is a deleted line).
	 *     @type array $final_matches Associative array of final matches. Index == row
	 *                                number of `$final`, value == corresponding row number
	 *                                of that same line in `$orig` or 'x' if there is no
	 *                                corresponding row (indicating it is a new line).
	 *     @type array $orig_rows     Associative array of interleaved rows of `$orig` with
	 *                                blanks to keep matches aligned with side-by-side diff
	 *                                of `$final`. A value >= 0 corresponds to index of `$orig`.
	 *                                Value < 0 indicates a blank row.
	 *     @type array $final_rows    Associative array of interleaved rows of `$final` with
	 *                                blanks to keep matches aligned with side-by-side diff
	 *                                of `$orig`. A value >= 0 corresponds to index of `$final`.
	 *                                Value < 0 indicates a blank row.
	 * }
	 */
	public function interleave_changed_lines( $orig, $final ) {

		// Contains all pairwise string comparisons. Keys are such that this need only be a one dimensional array.
		$matches = array();
		foreach ( array_keys( $orig ) as $o ) {
			foreach ( array_keys( $final ) as $f ) {
				$matches[ "$o,$f" ] = $this->compute_string_distance( $orig[ $o ], $final[ $f ] );
			}
		}
		asort( $matches ); // Order by string distance.

		$orig_matches  = array();
		$final_matches = array();

		foreach ( $matches as $keys => $difference ) {
			list($o, $f) = explode( ',', $keys );
			$o           = (int) $o;
			$f           = (int) $f;

			// Already have better matches for these guys.
			if ( isset( $orig_matches[ $o ] ) && isset( $final_matches[ $f ] ) ) {
				continue;
			}

			// First match for these guys. Must be best match.
			if ( ! isset( $orig_matches[ $o ] ) && ! isset( $final_matches[ $f ] ) ) {
				$orig_matches[ $o ]  = $f;
				$final_matches[ $f ] = $o;
				continue;
			}

			// Best match of this final is already taken? Must mean this final is a new row.
			if ( isset( $orig_matches[ $o ] ) ) {
				$final_matches[ $f ] = 'x';
			} elseif ( isset( $final_matches[ $f ] ) ) {
				// Best match of this orig is already taken? Must mean this orig is a deleted row.
				$orig_matches[ $o ] = 'x';
			}
		}

		// We read the text in this order.
		ksort( $orig_matches );
		ksort( $final_matches );

		// Stores rows and blanks for each column.
		$orig_rows      = array_keys( $orig_matches );
		$orig_rows_copy = $orig_rows;
		$final_rows     = array_keys( $final_matches );

		// Interleaves rows with blanks to keep matches aligned.
		// We may end up with some extraneous blank rows, but we'll just ignore them later.
		foreach ( $orig_rows_copy as $orig_row ) {
			$final_pos = array_search( $orig_matches[ $orig_row ], $final_rows, true );
			$orig_pos  = (int) array_search( $orig_row, $orig_rows, true );

			if ( false === $final_pos ) { // This orig is paired with a blank final.
				array_splice( $final_rows, $orig_pos, 0, -1 );
			} elseif ( $final_pos < $orig_pos ) { // This orig's match is up a ways. Pad final with blank rows.
				$diff_array = range( -1, $final_pos - $orig_pos );
				array_splice( $final_rows, $orig_pos, 0, $diff_array );
			} elseif ( $final_pos > $orig_pos ) { // This orig's match is down a ways. Pad orig with blank rows.
				$diff_array = range( -1, $orig_pos - $final_pos );
				array_splice( $orig_rows, $orig_pos, 0, $diff_array );
			}
		}

		// Pad the ends with blank rows if the columns aren't the same length.
		$diff_count = count( $orig_rows ) - count( $final_rows );
		if ( $diff_count < 0 ) {
			while ( $diff_count < 0 ) {
				array_push( $orig_rows, $diff_count++ );
			}
		} elseif ( $diff_count > 0 ) {
			$diff_count = -1 * $diff_count;
			while ( $diff_count < 0 ) {
				array_push( $final_rows, $diff_count++ );
			}
		}

		return array( $orig_matches, $final_matches, $orig_rows, $final_rows );
	}

	/**
	 * Computes a number that is intended to reflect the "distance" between two strings.
	 *
	 * @since 2.6.0
	 *
	 * @param string $string1
	 * @param string $string2
	 * @return int
	 */
	public function compute_string_distance( $string1, $string2 ) {
		// Use an md5 hash of the strings for a count cache, as it's fast to generate, and collisions aren't a concern.
		$count_key1 = md5( $string1 );
		$count_key2 = md5( $string2 );

		// Cache vectors containing character frequency for all chars in each string.
		if ( ! isset( $this->count_cache[ $count_key1 ] ) ) {
			$this->count_cache[ $count_key1 ] = count_chars( $string1 );
		}
		if ( ! isset( $this->count_cache[ $count_key2 ] ) ) {
			$this->count_cache[ $count_key2 ] = count_chars( $string2 );
		}

		$chars1 = $this->count_cache[ $count_key1 ];
		$chars2 = $this->count_cache[ $count_key2 ];

		$difference_key = md5( implode( ',', $chars1 ) . ':' . implode( ',', $chars2 ) );
		if ( ! isset( $this->difference_cache[ $difference_key ] ) ) {
			// L1-norm of difference vector.
			$this->difference_cache[ $difference_key ] = array_sum( array_map( array( $this, 'difference' ), $chars1, $chars2 ) );
		}

		$difference = $this->difference_cache[ $difference_key ];

		// $string1 has zero length? Odd. Give huge penalty by not dividing.
		if ( ! $string1 ) {
			return $difference;
		}

		// Return distance per character (of string1).
		return $difference / strlen( $string1 );
	}

	/**
	 * @ignore
	 * @since 2.6.0
	 *
	 * @param int $a
	 * @param int $b
	 * @return int
	 */
	public function difference( $a, $b ) {
		return abs( $a - $b );
	}

	/**
	 * Make private properties readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to get.
	 * @return mixed Property.
	 */
	public function __get( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return $this->$name;
		}
	}

	/**
	 * Make private properties settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name  Property to check if set.
	 * @param mixed  $value Property value.
	 * @return mixed Newly-set property.
	 */
	public function __set( $name, $value ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return $this->$name = $value;
		}
	}

	/**
	 * Make private properties checkable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to check if set.
	 * @return bool Whether the property is set.
	 */
	public function __isset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return isset( $this->$name );
		}
	}

	/**
	 * Make private properties un-settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to unset.
	 */
	public function __unset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			unset( $this->$name );
		}
	}
}
