(function () {
    'use strict';

    var Button = MediumEditor.Extension.extend({

        /* Button Options */

        /* action: [string]
         * The action argument to pass to MediumEditor.execAction()
         * when the button is clicked
         */
        action: undefined,

        /* aria: [string]
         * The value to add as the aria-label attribute of the button
         * element displayed in the toolbar.
         * This is also used as the tooltip for the button
         */
        aria: undefined,

        /* tagNames: [Array]
         * NOTE: This is not used if useQueryState is set to true.
         *
         * Array of element tag names that would indicate that this
         * button has already been applied. If this action has already
         * been applied, the button will be displayed as 'active' in the toolbar
         *
         * Example:
         * For 'bold', if the text is ever within a <b> or <strong>
         * tag that indicates the text is already bold. So the array
         * of tagNames for bold would be: ['b', 'strong']
         */
        tagNames: undefined,

        /* style: [Object]
         * NOTE: This is not used if useQueryState is set to true.
         *
         * A pair of css property & value(s) that indicate that this
         * button has already been applied. If this action has already
         * been applied, the button will be displayed as 'active' in the toolbar
         * Properties of the object:
         *   prop [String]: name of the css property
         *   value [String]: value(s) of the css property
         *                   multiple values can be separated by a '|'
         *
         * Example:
         * For 'bold', if the text is ever within an element with a 'font-weight'
         * style property set to '700' or 'bold', that indicates the text
         * is already bold.  So the style object for bold would be:
         * { prop: 'font-weight', value: '700|bold' }
         */
        style: undefined,

        /* useQueryState: [boolean]
         * Enables/disables whether this button should use the built-in
         * document.queryCommandState() method to determine whether
         * the action has already been applied.  If the action has already
         * been applied, the button will be displayed as 'active' in the toolbar
         *
         * Example:
         * For 'bold', if this is set to true, the code will call:
         * document.queryCommandState('bold') which will return true if the
         * browser thinks the text is already bold, and false otherwise
         */
        useQueryState: undefined,

        /* contentDefault: [string]
         * Default innerHTML to put inside the button
         */
        contentDefault: undefined,

        /* contentFA: [string]
         * The innerHTML to use for the content of the button
         * if the `buttonLabels` option for MediumEditor is set to 'fontawesome'
         */
        contentFA: undefined,

        /* classList: [Array]
         * An array of classNames (strings) to be added to the button
         */
        classList: undefined,

        /* attrs: [object]
         * A set of key-value pairs to add to the button as custom attributes
         */
        attrs: undefined,

        // The button constructor can optionally accept the name of a built-in button
        // (ie 'bold', 'italic', etc.)
        // When the name of a button is passed, it will initialize itself with the
        // configuration for that button
        constructor: function (options) {
            if (Button.isBuiltInButton(options)) {
                MediumEditor.Extension.call(this, this.defaults[options]);
            } else {
                MediumEditor.Extension.call(this, options);
            }
        },

        init: function () {
            MediumEditor.Extension.prototype.init.apply(this, arguments);

            this.button = this.createButton();
            this.on(this.button, 'click', this.handleClick.bind(this));
        },

        /* getButton: [function ()]
         *
         * If implemented, this function will be called when
         * the toolbar is being created.  The DOM Element returned
         * by this function will be appended to the toolbar along
         * with any other buttons.
         */
        getButton: function () {
            return this.button;
        },

        getAction: function () {
            return (typeof this.action === 'function') ? this.action(this.base.options) : this.action;
        },

        getAria: function () {
            return (typeof this.aria === 'function') ? this.aria(this.base.options) : this.aria;
        },

        getTagNames: function () {
            return (typeof this.tagNames === 'function') ? this.tagNames(this.base.options) : this.tagNames;
        },

        createButton: function () {
            var button = this.document.createElement('button'),
                content = this.contentDefault,
                ariaLabel = this.getAria(),
                buttonLabels = this.getEditorOption('buttonLabels');
            // Add class names
            button.classList.add('medium-editor-action');
            button.classList.add('medium-editor-action-' + this.name);
            if (this.classList) {
                this.classList.forEach(function (className) {
                    button.classList.add(className);
                });
            }

            // Add attributes
            button.setAttribute('data-action', this.getAction());
            if (ariaLabel) {
                button.setAttribute('title', ariaLabel);
                button.setAttribute('aria-label', ariaLabel);
            }
            if (this.attrs) {
                Object.keys(this.attrs).forEach(function (attr) {
                    button.setAttribute(attr, this.attrs[attr]);
                }, this);
            }

            if (buttonLabels === 'fontawesome' && this.contentFA) {
                content = this.contentFA;
            }
            button.innerHTML = content;
            return button;
        },

        handleClick: function (event) {
            event.preventDefault();
            event.stopPropagation();

            var action = this.getAction();

            if (action) {
                this.execAction(action);
            }
        },

        isActive: function () {
            return this.button.classList.contains(this.getEditorOption('activeButtonClass'));
        },

        setInactive: function () {
            this.button.classList.remove(this.getEditorOption('activeButtonClass'));
            delete this.knownState;
        },

        setActive: function () {
            this.button.classList.add(this.getEditorOption('activeButtonClass'));
            delete this.knownState;
        },

        queryCommandState: function () {
            var queryState = null;
            if (this.useQueryState) {
                queryState = this.base.queryCommandState(this.getAction());
            }
            return queryState;
        },

        isAlreadyApplied: function (node) {
            var isMatch = false,
                tagNames = this.getTagNames(),
                styleVals,
                computedStyle;

            if (this.knownState === false || this.knownState === true) {
                return this.knownState;
            }

            if (tagNames && tagNames.length > 0) {
                isMatch = tagNames.indexOf(node.nodeName.toLowerCase()) !== -1;
            }

            if (!isMatch && this.style) {
                styleVals = this.style.value.split('|');
                computedStyle = this.window.getComputedStyle(node, null).getPropertyValue(this.style.prop);
                styleVals.forEach(function (val) {
                    if (!this.knownState) {
                        isMatch = (computedStyle.indexOf(val) !== -1);
                        // text-decoration is not inherited by default
                        // so if the computed style for text-decoration doesn't match
                        // don't write to knownState so we can fallback to other checks
                        if (isMatch || this.style.prop !== 'text-decoration') {
                            this.knownState = isMatch;
                        }
                    }
                }, this);
            }

            return isMatch;
        }
    });

    Button.isBuiltInButton = function (name) {
        return (typeof name === 'string') && MediumEditor.extensions.button.prototype.defaults.hasOwnProperty(name);
    };

    MediumEditor.extensions.button = Button;
}());