'use strict';

var removeRule = require('./vcssom/removeRule').removeRule;

exports.addon = function (renderer) {
    // VCSSOM support only browser environment.
    if (!renderer.client) return;

    if (process.env.NODE_ENV !== 'production') {
        require('./__dev__/warnOnMissingDependencies')('cssom', renderer, ['createRule']); // cssom
    }

    var kebab = renderer.kebab;

    function VRule (selector, prelude) {
        this.rule = renderer.createRule(selector, prelude);
        this.decl = {};
    }
    VRule.prototype.diff = function (newDecl) {
        var oldDecl = this.decl;
        var style = this.rule.style;
        var property;
        for (property in oldDecl)
            if (newDecl[property] === undefined)
                style.removeProperty(property);
        for (property in newDecl)
            if (newDecl[property] !== oldDecl[property])
                style.setProperty(kebab(property), newDecl[property]);
        this.decl = newDecl;
    };
    VRule.prototype.del = function () {
        removeRule(this.rule);
    };

    function VSheet () {
        /**
         * {
         *   '<at-rule-prelude>': {
         *     '<selector>': {
         *       color: 'red
         *     }
         *   }
         * }
         */
        this.tree = {};
    }
    VSheet.prototype.diff = function (newTree) {
        var oldTree = this.tree;

        // Remove media queries not present in new tree.
        for (var prelude in oldTree) {
            if (newTree[prelude] === undefined) {
                var rules = oldTree[prelude];
                for (var selector in rules)
                    rules[selector].del();
            }
        }

        for (var prelude in newTree) {
            if (oldTree[prelude] === undefined) {
                // Whole media query is new.
                for (var selector in newTree[prelude]) {
                    var rule = new VRule(selector, prelude);
                    rule.diff(newTree[prelude][selector]);
                    newTree[prelude][selector] = rule;
                }
            } else {
                // Old tree already has rules with this media query.
                var oldRules = oldTree[prelude];
                var newRules = newTree[prelude];

                // Remove rules not present in new tree.
                for (var selector in oldRules)
                    if (!newRules[selector])
                        oldRules[selector].del();

                // Apply new rules.
                for (var selector in newRules) {
                    var rule = oldRules[selector];
                    if (rule) {
                        rule.diff(newRules[selector]);
                        newRules[selector] = rule;
                    } else {
                        rule = new VRule(selector, prelude);
                        rule.diff(newRules[selector]);
                        newRules[selector] = rule;
                    }
                }
            }
        }

        this.tree = newTree;
    };

    renderer.VRule = VRule;
    renderer.VSheet = VSheet;
};