<?php
/**
 * @private
 */
class Less_Visitor_processExtends extends Less_Visitor {

	public $allExtendsStack;

	/**
	 * @param Less_Tree_Ruleset $root
	 */
	public function run( $root ) {
		$extendFinder = new Less_Visitor_extendFinder();
		$extendFinder->run( $root );
		if ( !$extendFinder->foundExtends ) {
			return $root;
		}

		$root->allExtends = $this->doExtendChaining( $root->allExtends, $root->allExtends );

		$this->allExtendsStack = [];
		$this->allExtendsStack[] = &$root->allExtends;

		return $this->visitObj( $root );
	}

	private function doExtendChaining( $extendsList, $extendsListTarget, $iterationCount = 0 ) {
		//
		// chaining is different from normal extension.. if we extend an extend then we are not just copying, altering and pasting
		// the selector we would do normally, but we are also adding an extend with the same target selector
		// this means this new extend can then go and alter other extends
		//
		// this method deals with all the chaining work - without it, extend is flat and doesn't work on other extend selectors
		// this is also the most expensive.. and a match on one selector can cause an extension of a selector we had already processed if
		// we look at each selector at a time, as is done in visitRuleset

		$extendsToAdd = [];

		// loop through comparing every extend with every target extend.
		// a target extend is the one on the ruleset we are looking at copy/edit/pasting in place
		// e.g. .a:extend(.b) {} and .b:extend(.c) {} then the first extend extends the second one
		// and the second is the target.
		// the separation into two lists allows us to process a subset of chains with a bigger set, as is the
		// case when processing media queries
		for ( $extendIndex = 0, $extendsList_len = count( $extendsList ); $extendIndex < $extendsList_len; $extendIndex++ ) {
			for ( $targetExtendIndex = 0; $targetExtendIndex < count( $extendsListTarget ); $targetExtendIndex++ ) {

				$extend = $extendsList[$extendIndex];
				$targetExtend = $extendsListTarget[$targetExtendIndex];

				// Optimisation: Explicit reference, <https://github.com/wikimedia/less.php/pull/14>
				if ( \array_key_exists( $targetExtend->object_id, $extend->parent_ids ) ) {
					// ignore circular references
					continue;
				}

				// find a match in the target extends self selector (the bit before :extend)
				$selectorPath = [ $targetExtend->selfSelectors[0] ];
				$matches = $this->findMatch( $extend, $selectorPath );

				if ( $matches ) {

					// we found a match, so for each self selector..
					foreach ( $extend->selfSelectors as $selfSelector ) {

						// process the extend as usual
						$newSelector = $this->extendSelector( $matches, $selectorPath, $selfSelector );

						// but now we create a new extend from it
						$newExtend = new Less_Tree_Extend( $targetExtend->selector, $targetExtend->option, 0 );
						$newExtend->selfSelectors = $newSelector;

						// add the extend onto the list of extends for that selector
						end( $newSelector )->extendList = [ $newExtend ];
						// $newSelector[ count($newSelector)-1]->extendList = array($newExtend);

						// record that we need to add it.
						$extendsToAdd[] = $newExtend;
						$newExtend->ruleset = $targetExtend->ruleset;

						// remember its parents for circular references
						$newExtend->parent_ids = array_merge( $newExtend->parent_ids, $targetExtend->parent_ids, $extend->parent_ids );

						// only process the selector once.. if we have :extend(.a,.b) then multiple
						// extends will look at the same selector path, so when extending
						// we know that any others will be duplicates in terms of what is added to the css
						if ( $targetExtend->firstExtendOnThisSelectorPath ) {
							$newExtend->firstExtendOnThisSelectorPath = true;
							$targetExtend->ruleset->paths[] = $newSelector;
						}
					}
				}
			}
		}

		if ( $extendsToAdd ) {
			// try to detect circular references to stop a stack overflow.
			// may no longer be needed.			$this->extendChainCount++;
			if ( $iterationCount > 100 ) {

				try {
					$selectorOne = $extendsToAdd[0]->selfSelectors[0]->toCSS();
					$selectorTwo = $extendsToAdd[0]->selector->toCSS();
				} catch ( Exception $e ) {
					$selectorOne = "{unable to calculate}";
					$selectorTwo = "{unable to calculate}";
				}

				throw new Less_Exception_Parser( "extend circular reference detected. One of the circular extends is currently:" . $selectorOne . ":extend(" . $selectorTwo . ")" );
			}

			// now process the new extends on the existing rules so that we can handle a extending b extending c ectending d extending e...
			$extendsToAdd = $this->doExtendChaining( $extendsToAdd, $extendsListTarget, $iterationCount + 1 );
		}

		return array_merge( $extendsList, $extendsToAdd );
	}

	protected function visitDeclaration( $declNode, &$visitDeeper ) {
		$visitDeeper = false;
	}

	protected function visitMixinDefinition( $mixinDefinitionNode, &$visitDeeper ) {
		$visitDeeper = false;
	}

	protected function visitSelector( $selectorNode, &$visitDeeper ) {
		$visitDeeper = false;
	}

	protected function visitRuleset( $rulesetNode ) {
		if ( $rulesetNode->root ) {
			return;
		}

		$allExtends	= end( $this->allExtendsStack );
		$paths_len = count( $rulesetNode->paths );

		// look at each selector path in the ruleset, find any extend matches and then copy, find and replace
		foreach ( $allExtends as $allExtend ) {
			for ( $pathIndex = 0; $pathIndex < $paths_len; $pathIndex++ ) {

				// extending extends happens initially, before the main pass
				if ( isset( $rulesetNode->extendOnEveryPath ) && $rulesetNode->extendOnEveryPath ) {
					continue;
				}

				$selectorPath = $rulesetNode->paths[$pathIndex];

				if ( end( $selectorPath )->extendList ) {
					continue;
				}

				$this->ExtendMatch( $rulesetNode, $allExtend, $selectorPath );

			}
		}
	}

	private function ExtendMatch( $rulesetNode, $extend, $selectorPath ) {
		$matches = $this->findMatch( $extend, $selectorPath );

		if ( $matches ) {
			foreach ( $extend->selfSelectors as $selfSelector ) {
				$rulesetNode->paths[] = $this->extendSelector( $matches, $selectorPath, $selfSelector );
			}
		}
	}

	/**
	 * @param Less_Tree_Extend $extend
	 * @param Less_Tree_Selector[] $haystackSelectorPath
	 * @return false|array<array{index:int,initialCombinator:string}>
	 */
	private function findMatch( $extend, $haystackSelectorPath ) {
		if ( !$this->HasMatches( $extend, $haystackSelectorPath ) ) {
			return false;
		}

		//
		// look through the haystack selector path to try and find the needle - extend.selector
		// returns an array of selector matches that can then be replaced
		//
		$needleElements = $extend->selector->elements;
		$potentialMatches = [];
		$potentialMatches_len = 0;
		$potentialMatch = null;
		$matches = [];

		// loop through the haystack elements
		$haystack_path_len = count( $haystackSelectorPath );
		for ( $haystackSelectorIndex = 0; $haystackSelectorIndex < $haystack_path_len; $haystackSelectorIndex++ ) {
			$hackstackSelector = $haystackSelectorPath[$haystackSelectorIndex];

			$haystack_elements_len = count( $hackstackSelector->elements );
			for ( $hackstackElementIndex = 0; $hackstackElementIndex < $haystack_elements_len; $hackstackElementIndex++ ) {

				$haystackElement = $hackstackSelector->elements[$hackstackElementIndex];

				// if we allow elements before our match we can add a potential match every time. otherwise only at the first element.
				if ( $extend->allowBefore || ( $haystackSelectorIndex === 0 && $hackstackElementIndex === 0 ) ) {
					$potentialMatches[] = [ 'pathIndex' => $haystackSelectorIndex, 'index' => $hackstackElementIndex, 'matched' => 0, 'initialCombinator' => $haystackElement->combinator ];
					$potentialMatches_len++;
				}

				for ( $i = 0; $i < $potentialMatches_len; $i++ ) {

					$potentialMatch = &$potentialMatches[$i];
					$potentialMatch = $this->PotentialMatch( $potentialMatch, $needleElements, $haystackElement, $hackstackElementIndex );

					// if we are still valid and have finished, test whether we have elements after and whether these are allowed
					if ( $potentialMatch && $potentialMatch['matched'] === $extend->selector->elements_len ) {
						$potentialMatch['finished'] = true;

						if ( !$extend->allowAfter && ( $hackstackElementIndex + 1 < $haystack_elements_len || $haystackSelectorIndex + 1 < $haystack_path_len ) ) {
							$potentialMatch = null;
						}
					}

					// if null we remove, if not, we are still valid, so either push as a valid match or continue
					if ( $potentialMatch ) {
						if ( $potentialMatch['finished'] ) {
							$potentialMatch['length'] = $extend->selector->elements_len;
							$potentialMatch['endPathIndex'] = $haystackSelectorIndex;
							$potentialMatch['endPathElementIndex'] = $hackstackElementIndex + 1; // index after end of match
							$potentialMatches = []; // we don't allow matches to overlap, so start matching again
							$potentialMatches_len = 0;
							$matches[] = $potentialMatch;
						}
						continue;
					}

					array_splice( $potentialMatches, $i, 1 );
					$potentialMatches_len--;
					$i--;
				}
			}
		}

		return $matches;
	}

	// Before going through all the nested loops, lets check to see if a match is possible
	// Reduces Bootstrap 3.1 compile time from ~6.5s to ~5.6s
	private function HasMatches( $extend, $haystackSelectorPath ) {
		if ( !$extend->selector->cacheable ) {
			return true;
		}

		$first_el = $extend->selector->_oelements[0];

		foreach ( $haystackSelectorPath as $hackstackSelector ) {
			if ( !$hackstackSelector->cacheable ) {
				return true;
			}

			// Optimisation: Explicit reference, <https://github.com/wikimedia/less.php/pull/14>
			if ( \array_key_exists( $first_el, $hackstackSelector->_oelements_assoc ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * @param array $potentialMatch
	 * @param Less_Tree_Element[] $needleElements
	 * @param Less_Tree_Element $haystackElement
	 * @param int $hackstackElementIndex
	 */
	private function PotentialMatch( $potentialMatch, $needleElements, $haystackElement, $hackstackElementIndex ) {
		if ( $potentialMatch['matched'] > 0 ) {

			// selectors add " " onto the first element. When we use & it joins the selectors together, but if we don't
			// then each selector in haystackSelectorPath has a space before it added in the toCSS phase. so we need to work out
			// what the resulting combinator will be
			$targetCombinator = $haystackElement->combinator;
			if ( $targetCombinator === '' && $hackstackElementIndex === 0 ) {
				$targetCombinator = ' ';
			}

			if ( $needleElements[ $potentialMatch['matched'] ]->combinator !== $targetCombinator ) {
				return null;
			}
		}

		// if we don't match, null our match to indicate failure
		if ( !$this->isElementValuesEqual( $needleElements[$potentialMatch['matched'] ]->value, $haystackElement->value ) ) {
			return null;
		}

		$potentialMatch['finished'] = false;
		$potentialMatch['matched']++;

		return $potentialMatch;
	}

	/**
	 * @param string|Less_Tree_Attribute|Less_Tree_Dimension|Less_Tree_Keyword $elementValue1
	 * @param string|Less_Tree_Attribute|Less_Tree_Dimension|Less_Tree_Keyword $elementValue2
	 * @return bool
	 */
	private function isElementValuesEqual( $elementValue1, $elementValue2 ) {
		if ( $elementValue1 === $elementValue2 ) {
			return true;
		}

		if ( is_string( $elementValue1 ) || is_string( $elementValue2 ) ) {
			return false;
		}

		if ( $elementValue1 instanceof Less_Tree_Attribute ) {
			return $this->isAttributeValuesEqual( $elementValue1, $elementValue2 );
		}

		$elementValue1 = $elementValue1->value;
		if ( $elementValue1 instanceof Less_Tree_Selector ) {
			return $this->isSelectorValuesEqual( $elementValue1, $elementValue2 );
		}

		return false;
	}

	/**
	 * @param Less_Tree_Selector $elementValue1
	 */
	private function isSelectorValuesEqual( $elementValue1, $elementValue2 ) {
		$elementValue2 = $elementValue2->value;
		if ( !( $elementValue2 instanceof Less_Tree_Selector ) || $elementValue1->elements_len !== $elementValue2->elements_len ) {
			return false;
		}

		for ( $i = 0; $i < $elementValue1->elements_len; $i++ ) {

			if ( $elementValue1->elements[$i]->combinator !== $elementValue2->elements[$i]->combinator ) {
				if ( $i !== 0 || ( $elementValue1->elements[$i]->combinator || ' ' ) !== ( $elementValue2->elements[$i]->combinator || ' ' ) ) {
					return false;
				}
			}

			if ( !$this->isElementValuesEqual( $elementValue1->elements[$i]->value, $elementValue2->elements[$i]->value ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * @param Less_Tree_Attribute $elementValue1
	 */
	private function isAttributeValuesEqual( $elementValue1, $elementValue2 ) {
		if ( $elementValue1->op !== $elementValue2->op || $elementValue1->key !== $elementValue2->key ) {
			return false;
		}

		if ( !$elementValue1->value || !$elementValue2->value ) {
			if ( $elementValue1->value || $elementValue2->value ) {
				return false;
			}
			return true;
		}

		$elementValue1 = $elementValue1->value;

		if ( $elementValue1 instanceof Less_Tree_Quoted ) {
			$elementValue1 = $elementValue1->value;
		}

		$elementValue2 = $elementValue2->value;

		if ( $elementValue2 instanceof Less_Tree_Quoted ) {
			$elementValue2 = $elementValue2->value;
		}

		return $elementValue1 === $elementValue2;
	}

	private function extendSelector( $matches, $selectorPath, $replacementSelector ) {
		// for a set of matches, replace each match with the replacement selector

		$currentSelectorPathIndex = 0;
		$currentSelectorPathElementIndex = 0;
		$path = [];
		$selectorPath_len = count( $selectorPath );

		for ( $matchIndex = 0, $matches_len = count( $matches ); $matchIndex < $matches_len; $matchIndex++ ) {

			$match = $matches[$matchIndex];
			$selector = $selectorPath[ $match['pathIndex'] ];

			$firstElement = new Less_Tree_Element(
				$match['initialCombinator'],
				$replacementSelector->elements[0]->value,
				$replacementSelector->elements[0]->index,
				$replacementSelector->elements[0]->currentFileInfo
			);

			if ( $match['pathIndex'] > $currentSelectorPathIndex && $currentSelectorPathElementIndex > 0 ) {
				$last_path = end( $path );
				$last_path->elements = array_merge( $last_path->elements, array_slice( $selectorPath[$currentSelectorPathIndex]->elements, $currentSelectorPathElementIndex ) );
				$currentSelectorPathElementIndex = 0;
				$currentSelectorPathIndex++;
			}

			$newElements = array_merge(
				array_slice(
					$selector->elements,
					$currentSelectorPathElementIndex,
					// last parameter of array_slice is different than the last parameter of javascript's slice
					$match['index'] - $currentSelectorPathElementIndex
				),
				 [ $firstElement ],
				 array_slice( $replacementSelector->elements, 1 )
				);

			if ( $currentSelectorPathIndex === $match['pathIndex'] && $matchIndex > 0 ) {
				$last_key = count( $path ) - 1;
				$path[$last_key]->elements = array_merge( $path[$last_key]->elements, $newElements );
			} else {
				$path = array_merge( $path, array_slice( $selectorPath, $currentSelectorPathIndex, $match['pathIndex'] ) );
				$path[] = new Less_Tree_Selector( $newElements );
			}

			$currentSelectorPathIndex = $match['endPathIndex'];
			$currentSelectorPathElementIndex = $match['endPathElementIndex'];
			if ( $currentSelectorPathElementIndex >= count( $selectorPath[$currentSelectorPathIndex]->elements ) ) {
				$currentSelectorPathElementIndex = 0;
				$currentSelectorPathIndex++;
			}
		}

		if ( $currentSelectorPathIndex < $selectorPath_len && $currentSelectorPathElementIndex > 0 ) {
			$last_path = end( $path );
			$last_path->elements = array_merge( $last_path->elements, array_slice( $selectorPath[$currentSelectorPathIndex]->elements, $currentSelectorPathElementIndex ) );
			$currentSelectorPathIndex++;
		}

		$slice_len = $selectorPath_len - $currentSelectorPathIndex;
		$path = array_merge( $path, array_slice( $selectorPath, $currentSelectorPathIndex, $slice_len ) );

		return $path;
	}

	protected function visitMedia( $mediaNode ) {
		$newAllExtends = array_merge( $mediaNode->allExtends, end( $this->allExtendsStack ) );
		$this->allExtendsStack[] = $this->doExtendChaining( $newAllExtends, $mediaNode->allExtends );
	}

	protected function visitMediaOut() {
		array_pop( $this->allExtendsStack );
	}

	protected function visitAtRule( $atRuleNode ) {
		$newAllExtends = array_merge( $atRuleNode->allExtends, end( $this->allExtendsStack ) );
		$this->allExtendsStack[] = $this->doExtendChaining( $newAllExtends, $atRuleNode->allExtends );
	}

	protected function visitAtRuleOut() {
		array_pop( $this->allExtendsStack );
	}

}
