var tree = require("../tree"),
    Visitor = require("./visitor");

/*jshint loopfunc:true */

var ExtendFinderVisitor = function() {
    this._visitor = new Visitor(this);
    this.contexts = [];
    this.allExtendsStack = [[]];
};

ExtendFinderVisitor.prototype = {
    run: function (root) {
        root = this._visitor.visit(root);
        root.allExtends = this.allExtendsStack[0];
        return root;
    },
    visitRule: function (ruleNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitRuleset: function (rulesetNode, visitArgs) {
        if (rulesetNode.root) {
            return;
        }

        var i, j, extend, allSelectorsExtendList = [], extendList;

        // get &:extend(.a); rules which apply to all selectors in this ruleset
        var rules = rulesetNode.rules, ruleCnt = rules ? rules.length : 0;
        for(i = 0; i < ruleCnt; i++) {
            if (rulesetNode.rules[i] instanceof tree.Extend) {
                allSelectorsExtendList.push(rules[i]);
                rulesetNode.extendOnEveryPath = true;
            }
        }

        // now find every selector and apply the extends that apply to all extends
        // and the ones which apply to an individual extend
        var paths = rulesetNode.paths;
        for(i = 0; i < paths.length; i++) {
            var selectorPath = paths[i],
                selector = selectorPath[selectorPath.length - 1],
                selExtendList = selector.extendList;

            extendList = selExtendList ? selExtendList.slice(0).concat(allSelectorsExtendList)
                                       : allSelectorsExtendList;

            if (extendList) {
                extendList = extendList.map(function(allSelectorsExtend) {
                    return allSelectorsExtend.clone();
                });
            }

            for(j = 0; j < extendList.length; j++) {
                this.foundExtends = true;
                extend = extendList[j];
                extend.findSelfSelectors(selectorPath);
                extend.ruleset = rulesetNode;
                if (j === 0) { extend.firstExtendOnThisSelectorPath = true; }
                this.allExtendsStack[this.allExtendsStack.length-1].push(extend);
            }
        }

        this.contexts.push(rulesetNode.selectors);
    },
    visitRulesetOut: function (rulesetNode) {
        if (!rulesetNode.root) {
            this.contexts.length = this.contexts.length - 1;
        }
    },
    visitMedia: function (mediaNode, visitArgs) {
        mediaNode.allExtends = [];
        this.allExtendsStack.push(mediaNode.allExtends);
    },
    visitMediaOut: function (mediaNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    },
    visitDirective: function (directiveNode, visitArgs) {
        directiveNode.allExtends = [];
        this.allExtendsStack.push(directiveNode.allExtends);
    },
    visitDirectiveOut: function (directiveNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    }
};

var ProcessExtendsVisitor = function() {
    this._visitor = new Visitor(this);
};

ProcessExtendsVisitor.prototype = {
    run: function(root) {
        var extendFinder = new ExtendFinderVisitor();
        extendFinder.run(root);
        if (!extendFinder.foundExtends) { return root; }
        root.allExtends = root.allExtends.concat(this.doExtendChaining(root.allExtends, root.allExtends));
        this.allExtendsStack = [root.allExtends];
        return this._visitor.visit(root);
    },
    doExtendChaining: function (extendsList, extendsListTarget, iterationCount) {
        //
        // 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

        var extendIndex, targetExtendIndex, matches, extendsToAdd = [], newSelector, extendVisitor = this, selectorPath, extend, targetExtend, newExtend;

        iterationCount = iterationCount || 0;

        //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 seperation 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; extendIndex < extendsList.length; extendIndex++){
            for(targetExtendIndex = 0; targetExtendIndex < extendsListTarget.length; targetExtendIndex++){

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

                // look for circular references
                if( extend.parent_ids.indexOf( targetExtend.object_id ) >= 0 ){ continue; }

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

                if (matches.length) {

                    // we found a match, so for each self selector..
                    extend.selfSelectors.forEach(function(selfSelector) {

                        // process the extend as usual
                        newSelector = extendVisitor.extendSelector(matches, selectorPath, selfSelector);

                        // but now we create a new extend from it
                        newExtend = new(tree.Extend)(targetExtend.selector, targetExtend.option, 0);
                        newExtend.selfSelectors = newSelector;

                        // add the extend onto the list of extends for that selector
                        newSelector[newSelector.length-1].extendList = [newExtend];

                        // record that we need to add it.
                        extendsToAdd.push(newExtend);
                        newExtend.ruleset = targetExtend.ruleset;

                        //remember its parents for circular references
                        newExtend.parent_ids = newExtend.parent_ids.concat(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.push(newSelector);
                        }
                    });
                }
            }
        }

        if (extendsToAdd.length) {
            // try to detect circular references to stop a stack overflow.
            // may no longer be needed.
            this.extendChainCount++;
            if (iterationCount > 100) {
                var selectorOne = "{unable to calculate}";
                var selectorTwo = "{unable to calculate}";
                try
                {
                    selectorOne = extendsToAdd[0].selfSelectors[0].toCSS();
                    selectorTwo = extendsToAdd[0].selector.toCSS();
                }
                catch(e) {}
                throw {message: "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...
            return extendsToAdd.concat(extendVisitor.doExtendChaining(extendsToAdd, extendsListTarget, iterationCount+1));
        } else {
            return extendsToAdd;
        }
    },
    visitRule: function (ruleNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitSelector: function (selectorNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitRuleset: function (rulesetNode, visitArgs) {
        if (rulesetNode.root) {
            return;
        }
        var matches, pathIndex, extendIndex, allExtends = this.allExtendsStack[this.allExtendsStack.length-1], selectorsToAdd = [], extendVisitor = this, selectorPath;

        // look at each selector path in the ruleset, find any extend matches and then copy, find and replace

        for(extendIndex = 0; extendIndex < allExtends.length; extendIndex++) {
            for(pathIndex = 0; pathIndex < rulesetNode.paths.length; pathIndex++) {
                selectorPath = rulesetNode.paths[pathIndex];

                // extending extends happens initially, before the main pass
                if (rulesetNode.extendOnEveryPath) { continue; }
                var extendList = selectorPath[selectorPath.length-1].extendList;
                if (extendList && extendList.length) { continue; }

                matches = this.findMatch(allExtends[extendIndex], selectorPath);

                if (matches.length) {

                    allExtends[extendIndex].selfSelectors.forEach(function(selfSelector) {
                        selectorsToAdd.push(extendVisitor.extendSelector(matches, selectorPath, selfSelector));
                    });
                }
            }
        }
        rulesetNode.paths = rulesetNode.paths.concat(selectorsToAdd);
    },
    findMatch: function (extend, haystackSelectorPath) {
        //
        // 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
        //
        var haystackSelectorIndex, hackstackSelector, hackstackElementIndex, haystackElement,
            targetCombinator, i,
            extendVisitor = this,
            needleElements = extend.selector.elements,
            potentialMatches = [], potentialMatch, matches = [];

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

            for(hackstackElementIndex = 0; hackstackElementIndex < hackstackSelector.elements.length; 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.push({pathIndex: haystackSelectorIndex, index: hackstackElementIndex, matched: 0, initialCombinator: haystackElement.combinator});
                }

                for(i = 0; i < potentialMatches.length; i++) {
                    potentialMatch = potentialMatches[i];

                    // 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.value;
                    if (targetCombinator === '' && hackstackElementIndex === 0) {
                        targetCombinator = ' ';
                    }

                    // if we don't match, null our match to indicate failure
                    if (!extendVisitor.isElementValuesEqual(needleElements[potentialMatch.matched].value, haystackElement.value) ||
                        (potentialMatch.matched > 0 && needleElements[potentialMatch.matched].combinator.value !== targetCombinator)) {
                        potentialMatch = null;
                    } else {
                        potentialMatch.matched++;
                    }

                    // if we are still valid and have finished, test whether we have elements after and whether these are allowed
                    if (potentialMatch) {
                        potentialMatch.finished = potentialMatch.matched === needleElements.length;
                        if (potentialMatch.finished &&
                            (!extend.allowAfter && (hackstackElementIndex+1 < hackstackSelector.elements.length || haystackSelectorIndex+1 < haystackSelectorPath.length))) {
                            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 = needleElements.length;
                            potentialMatch.endPathIndex = haystackSelectorIndex;
                            potentialMatch.endPathElementIndex = hackstackElementIndex + 1; // index after end of match
                            potentialMatches.length = 0; // we don't allow matches to overlap, so start matching again
                            matches.push(potentialMatch);
                        }
                    } else {
                        potentialMatches.splice(i, 1);
                        i--;
                    }
                }
            }
        }
        return matches;
    },
    isElementValuesEqual: function(elementValue1, elementValue2) {
        if (typeof elementValue1 === "string" || typeof elementValue2 === "string") {
            return elementValue1 === elementValue2;
        }
        if (elementValue1 instanceof tree.Attribute) {
            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.value || elementValue1.value;
            elementValue2 = elementValue2.value.value || elementValue2.value;
            return elementValue1 === elementValue2;
        }
        elementValue1 = elementValue1.value;
        elementValue2 = elementValue2.value;
        if (elementValue1 instanceof tree.Selector) {
            if (!(elementValue2 instanceof tree.Selector) || elementValue1.elements.length !== elementValue2.elements.length) {
                return false;
            }
            for(var i = 0; i <elementValue1.elements.length; i++) {
                if (elementValue1.elements[i].combinator.value !== elementValue2.elements[i].combinator.value) {
                    if (i !== 0 || (elementValue1.elements[i].combinator.value || ' ') !== (elementValue2.elements[i].combinator.value || ' ')) {
                        return false;
                    }
                }
                if (!this.isElementValuesEqual(elementValue1.elements[i].value, elementValue2.elements[i].value)) {
                    return false;
                }
            }
            return true;
        }
        return false;
    },
    extendSelector:function (matches, selectorPath, replacementSelector) {

        //for a set of matches, replace each match with the replacement selector

        var currentSelectorPathIndex = 0,
            currentSelectorPathElementIndex = 0,
            path = [],
            matchIndex,
            selector,
            firstElement,
            match,
            newElements;

        for (matchIndex = 0; matchIndex < matches.length; matchIndex++) {
            match = matches[matchIndex];
            selector = selectorPath[match.pathIndex];
            firstElement = new tree.Element(
                match.initialCombinator,
                replacementSelector.elements[0].value,
                replacementSelector.elements[0].index,
                replacementSelector.elements[0].currentFileInfo
            );

            if (match.pathIndex > currentSelectorPathIndex && currentSelectorPathElementIndex > 0) {
                path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                currentSelectorPathElementIndex = 0;
                currentSelectorPathIndex++;
            }

            newElements = selector.elements
                .slice(currentSelectorPathElementIndex, match.index)
                .concat([firstElement])
                .concat(replacementSelector.elements.slice(1));

            if (currentSelectorPathIndex === match.pathIndex && matchIndex > 0) {
                path[path.length - 1].elements =
                    path[path.length - 1].elements.concat(newElements);
            } else {
                path = path.concat(selectorPath.slice(currentSelectorPathIndex, match.pathIndex));

                path.push(new tree.Selector(
                    newElements
                ));
            }
            currentSelectorPathIndex = match.endPathIndex;
            currentSelectorPathElementIndex = match.endPathElementIndex;
            if (currentSelectorPathElementIndex >= selectorPath[currentSelectorPathIndex].elements.length) {
                currentSelectorPathElementIndex = 0;
                currentSelectorPathIndex++;
            }
        }

        if (currentSelectorPathIndex < selectorPath.length && currentSelectorPathElementIndex > 0) {
            path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
            currentSelectorPathIndex++;
        }

        path = path.concat(selectorPath.slice(currentSelectorPathIndex, selectorPath.length));

        return path;
    },
    visitRulesetOut: function (rulesetNode) {
    },
    visitMedia: function (mediaNode, visitArgs) {
        var newAllExtends = mediaNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
        newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, mediaNode.allExtends));
        this.allExtendsStack.push(newAllExtends);
    },
    visitMediaOut: function (mediaNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    },
    visitDirective: function (directiveNode, visitArgs) {
        var newAllExtends = directiveNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
        newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, directiveNode.allExtends));
        this.allExtendsStack.push(newAllExtends);
    },
    visitDirectiveOut: function (directiveNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    }
};

module.exports = ProcessExtendsVisitor;
