DeanMarkTaylor/post-menu-private-message-button.js

## post-menu-private-message-button.js
// Show Private Message button (for specific categories)
// NOTE: In order for the button to display you need to 'message' to the post_menu site setting.
(function (require, Discourse, I18n, Em) {
    var Button = require('discourse/views/post-menu').Button;

    Discourse.PostMenuView.reopen({
        buttonForMessage: function (post) {
            // NOTE: just set whiteListedCategories to null / empty array to make buttons visible everywhere.
            var whiteListedCategories = [37, 71, 72, 73, 74, 75, 76, 77, 78],
                currentUser = Discourse.User.current();

            // Only create the button if the post author is not the current user.
            if (currentUser && (currentUser.id === post.user_id)) {
                return null;
            }

            // Don't display for private messages.
            if (post.topic && post.topic.archetype === 'private_message') {
                return null;
            }

            // Only display button for specific categories
            if (whiteListedCategories && whiteListedCategories.length > 0) {
                if (post.topic &&
                    post.topic.category_id &&
                    whiteListedCategories.indexOf(post.topic.category_id) === -1) {
                    return null;
                }
            }

            return new Button('message', 'topic.private_message', 'envelope', {
                className: 'message-button',
                disabled:  false
            });
        },

        clickMessage: function (post) {
            this.get('controller').send('replyAsNewPrivateMessage', post);
        }
    });

    Discourse.TopicController.reopen({
        actions: {
            replyAsNewPrivateMessage: function (post) {
                var composerController = this.get('controllers.composer'),
                    quoteController = this.get('controllers.quote-button'),
                    quotedText = Discourse.Quote.build(quoteController.get('post'), quoteController.get('buffer')),
                    topic = post ? post.get('topic') : this.get('model'),
                    self = this;

                quoteController.deselectText();

                composerController.open({
                    action:      Discourse.Composer.PRIVATE_MESSAGE,
                    usernames:   post.get('username'),
                    archetypeId: 'private_message',
                    draftKey:    'new_private_message'
                }).then(function () {
                    return Em.isEmpty(quotedText) ? Discourse.Post.loadQuote(post.get('id')) : quotedText;
                }).then(function (q) {
                    var postUrl = '' + location.protocol + '//' + location.host + (post.get('url')),
                        postLink = '[' + self.get('title') + '](' + postUrl + ')';
                    composerController.appendText(I18n.t('post.continue_discussion', {postLink: postLink}) + '\n\n' + q);
                });

                return false;
            }
        }
    });

})(window.require, window.Discourse, window.I18n, window.Em);