var reactions = (function () {
var exports = {};

function send_reaction_ajax(message_id, emoji_name, operation) {
    if (!emoji.emojis_by_name[emoji_name] && !emoji.realm_emojis[emoji_name]) {
        // Emoji doesn't exist
        return;
    }
    var args = {
        url: '/json/messages/' + message_id + '/emoji_reactions/' + encodeURIComponent(emoji_name),
        data: {},
        success: function () {},
        error: function (xhr) {
            var response = channel.xhr_error_message("Error sending reaction", xhr);
            // Errors are somewhat commmon here, due to race conditions
            // where the user tries to add/remove the reaction when there is already
            // an in-flight request.  We eventually want to make this a blueslip
            // error, rather than a warning, but we need to implement either
            // #4291 or #4295 first.
            blueslip.warn(response);
        },
    };
    if (operation === 'add') {
        channel.put(args);
    } else if (operation === 'remove') {
        channel.del(args);
    }
}

exports.current_user_has_reacted_to_emoji = function (message, emoji_name) {
    var user_id = page_params.user_id;
    return _.any(message.reactions, function (r) {
        return (r.user.id === user_id) &&  (r.emoji_name === emoji_name);
    });
};

function get_user_list_for_message_reaction(message, emoji_name) {
    var matching_reactions = message.reactions.filter(function (reaction) {
        return reaction.emoji_name === emoji_name;
    });
    return matching_reactions.map(function (reaction) {
        return reaction.user.id;
    });
}

function get_message(message_id) {
    var message = message_store.get(message_id);
    if (!message) {
        blueslip.error('reactions: Bad message id: ' + message_id);
        return;
    }

    return message;
}

exports.message_reaction_on_click = function (message_id, emoji_name) {
    // This toggles the current user's reaction to the clicked emoji.

    var message = get_message(message_id);
    if (!message) {
        return;
    }

    var has_reacted = exports.current_user_has_reacted_to_emoji(message, emoji_name);
    var operation = has_reacted ? 'remove' : 'add';

    send_reaction_ajax(message_id, emoji_name, operation);
};

function get_selected_emoji() {
    return $(".emoji-popover-emoji").filter(":focus")[0];
}

exports.toggle_reaction = function (message_id, emoji_name) {
    var message = get_message(message_id);
    if (!message) {
        return;
    }

    var selected_emoji = get_selected_emoji();
    if (emoji_name === undefined && selected_emoji === undefined) {
        return;
    }
    if (selected_emoji) {
        emoji_name = selected_emoji.title;
    }

    var has_reacted = exports.current_user_has_reacted_to_emoji(message, emoji_name);
    var operation = has_reacted ? 'remove' : 'add';

    send_reaction_ajax(message_id, emoji_name, operation);
    emoji_picker.hide_emoji_popover();
};

var reaction_show_list = []; // local reaction_show_list

exports.render_reaction_show_list = function () {
    var reaction_list = $(".emoji-popover-emoji");
    reaction_show_list = reaction_list.filter(function () {
        return $(this).css('display') === "inline-block";
    }).toArray();
};

function filter_emojis() {
    var elt = $(".emoji-popover-filter").expectOne();
    var search_term = elt.val().trim().toLowerCase();
    var reaction_list = $(".emoji-popover-emoji");
    if (search_term !== '') {
        reaction_list.each(function () {
            if (this.title.indexOf(search_term) === -1) {
                this.classList.add("hide");
            } else {
                this.classList.remove("hide");
            }
        });
    } else {
        reaction_list.removeClass("hide");
    }
    exports.render_reaction_show_list();
}

function get_emoji_at_index(index) {
    if (index >= 0 && index < reaction_show_list.length) {
        return reaction_show_list[index];
    }
}

function find_index_for_emoji(emoji) {
    return reaction_show_list.findIndex(function (reaction) {
        return emoji === reaction;
    });
}

function maybe_select_emoji(e) {
    if (e.keyCode === 13) { // enter key
        e.preventDefault();
        var first_emoji = get_emoji_at_index(0);
        if (first_emoji) {
            if (emoji_picker.is_composition(first_emoji)) {
                first_emoji.click();
            } else {
                exports.toggle_reaction(current_msg_list.selected_id(), first_emoji.title);
            }
        }
    }
}

$(document).on('click', '.emoji-popover-emoji.reaction', function () {
    // When an emoji is clicked in the popover,
    // if the user has reacted to this message with this emoji
    // the reaction is removed
    // otherwise, the reaction is added
    var emoji_name = this.title;
    var message_id = $(this).parent().attr('data-message-id');

    var message = get_message(message_id);
    if (!message) {
        return;
    }

    if (exports.current_user_has_reacted_to_emoji(message, emoji_name)) {
        $(this).removeClass('reacted');
    }
    exports.toggle_reaction(message_id, emoji_name);
});

$(document).on('input', '.emoji-popover-filter', filter_emojis);
$(document).on('keydown', '.emoji-popover-filter', maybe_select_emoji);

exports.reaction_navigate = function (e, event_name) {
    var first_emoji = get_emoji_at_index(0);
    var selected_emoji = get_selected_emoji();
    var selected_index = find_index_for_emoji(selected_emoji);

    // special cases
    if (event_name === 'down_arrow') {
        if ($('.emoji-popover-filter').is(':focus') && first_emoji) { // move down into emoji map
            $(first_emoji).focus();
        }
    } else if (event_name === 'up_arrow') {
        if (selected_emoji && selected_index < 6) {
            // In this case, we're move up into the reaction filter
            // rows.  Here, we override the default browser behavior,
            // which in Firefox is good (preserving the cursor
            // position) and in Chrome is bad (cursor goes to
            // beginning) with something reasonable and consistent
            // (cursor goes to the end of the filter string).
            $('.emoji-popover-filter').focus().caret(Infinity);
            return true;
        }
    }

    if (selected_emoji === undefined) {
        return false;
    }
    var next_index;
    switch (event_name) {
        case 'down_arrow':
            next_index = selected_index + 6;
            break;
        case 'up_arrow':
            next_index = selected_index - 6;
            break;
        case 'left_arrow':
            next_index = selected_index - 1;
            break;
        case 'right_arrow':
            next_index = selected_index + 1;
            break;
    }
    var next_emoji = get_emoji_at_index(next_index);
    if (next_emoji) {
        $(next_emoji).focus();
        return true;
    }
    return false;
};

function full_name(user_id) {
    if (user_id === page_params.user_id) {
        return 'You (click to remove)';
    }
    return people.get_person_from_user_id(user_id).full_name;
}

function generate_title(emoji_name, user_ids) {
    var i = user_ids.indexOf(page_params.user_id);
    if (i !== -1) {
        // Move current user's id to start of list
        user_ids.splice(i, 1);
        user_ids.unshift(page_params.user_id);
    }
    var reacted_with_string = ' reacted with :' + emoji_name + ':';
    var user_names = user_ids.map(full_name);
    if (user_names.length === 1) {
        return user_names[0] + reacted_with_string;
    }
    return _.initial(user_names).join(', ') + ' and ' + _.last(user_names) + reacted_with_string;
}

exports.get_reaction_section = function (message_id) {
    var message_element = $('.message_table').find("[zid='" + message_id + "']");
    var section = message_element.find('.message_reactions');
    return section;
};

exports.find_reaction = function (message_id, emoji_name) {
    var reaction_section = exports.get_reaction_section(message_id);
    var reaction = reaction_section.find("[data-emoji-name='" + emoji_name + "']");
    return reaction;
};

exports.get_add_reaction_button = function (message_id) {
    var reaction_section = exports.get_reaction_section(message_id);
    var add_button = reaction_section.find('.reaction_button');
    return add_button;
};

exports.add_reaction = function (event) {
    var message_id = event.message_id;
    var emoji_name = event.emoji_name;

    var message = message_store.get(message_id);
    if (message === undefined) {
        // If we don't have the message in cache, do nothing; if we
        // ever fetch it from the server, it'll come with the
        // latest reactions attached
        return;
    }

    event.emoji_name_css_class = emoji.emojis_name_to_css_class[emoji_name];
    event.user.id = event.user.user_id;

    message.reactions.push(event);

    var user_list = get_user_list_for_message_reaction(message, emoji_name);

    if (user_list.length > 1) {
        exports.update_existing_reaction(event, user_list);
    } else {
        exports.insert_new_reaction(event, user_list);
    }
};

exports.update_existing_reaction = function (event, user_list) {
    // Our caller ensures that this message already has a reaction
    // for this emoji and sets up our user_list.  This function
    // simply updates the DOM.

    var message_id = event.message_id;
    var emoji_name = event.emoji_name;

    var reaction = exports.find_reaction(message_id, emoji_name);
    var count_element = reaction.find('.message_reaction_count');

    count_element.html(user_list.length);

    var new_title = generate_title(emoji_name, user_list);
    reaction.prop('title', new_title);

    if (event.user.id === page_params.user_id) {
        reaction.addClass("reacted");
    }
};

exports.insert_new_reaction = function (event, user_list) {
    // Our caller ensures we are the first user to react to this
    // message with this emoji, and it populates user_list for
    // us.  We then render the emoji/title/count and insert it
    // before the add button.

    var message_id = event.message_id;
    var emoji_name = event.emoji_name;

    var new_title = generate_title(emoji_name, user_list);

    if (emoji.realm_emojis[emoji_name]) {
        event.is_realm_emoji = true;
        event.url = emoji.realm_emojis[emoji_name].emoji_url;
    }

    event.count = 1;
    event.title = new_title;
    event.emoji_alt_code = page_params.emoji_alt_code;

    if (event.user.id === page_params.user_id) {
        event.class = "message_reaction reacted";
    } else {
        event.class = "message_reaction";
    }

    var new_reaction = $(templates.render('message_reaction', event));

    // Now insert it before the add button.
    var reaction_button_element = exports.get_add_reaction_button(message_id);
    new_reaction.insertBefore(reaction_button_element);
};

exports.remove_reaction = function (event) {
    var emoji_name = event.emoji_name;
    var message_id = event.message_id;
    var user_id = event.user.user_id;
    var i = -1;
    var message = message_store.get(message_id);

    if (message === undefined) {
        // If we don't have the message in cache, do nothing; if we
        // ever fetch it from the server, it'll come with the
        // latest reactions attached
        return;
    }

    // Do the data part first:
    // Remove reactions from our message object.
    _.each(message.reactions, function (reaction, index) {
        if (reaction.emoji_name === emoji_name && reaction.user.id === user_id) {
            i = index;
        }
    });

    if (i !== -1) {
        message.reactions.splice(i, 1);
    }

    // Compute the new user list for this reaction.
    var user_list = get_user_list_for_message_reaction(message, emoji_name);

    var reaction = exports.find_reaction(message_id, emoji_name);

    if (user_list.length === 0) {
        // If this user was the only one reacting for this emoji, we simply
        // remove the reaction and exit.
        reaction.remove();
        return;
    }

    // The emoji still has reactions from other users, so we need to update
    // the title/count and, if the user is the current user, turn off the
    // "reacted" class.

    var new_title = generate_title(emoji_name, user_list);
    reaction.prop('title', new_title);

    var count_element = reaction.find('.message_reaction_count');
    count_element.html(user_list.length);

    if (user_id === page_params.user_id) {
        reaction.removeClass("reacted");
    }
};

exports.get_emojis_used_by_user_for_message_id = function (message_id) {
    var user_id = page_params.user_id;
    var message = message_store.get(message_id);
    var reactions_by_user = message.reactions.filter(function (reaction) {
        return reaction.user.id === user_id;
    });
    return reactions_by_user.map(function (reaction) {
        return reaction.emoji_name;
    });
};

exports.get_message_reactions = function (message) {
    var message_reactions = new Dict();
    _.each(message.reactions, function (reaction) {
        var user_id = reaction.user.id;
        if (!people.is_known_user_id(user_id)) {
            blueslip.warn('Unknown user_id ' + user_id +
                          'in reaction for message ' + message.id);
            return;
        }

        var user_list = message_reactions.setdefault(reaction.emoji_name, []);
        user_list.push(user_id);
    });
    var reactions = message_reactions.items().map(function (item) {
        var emoji_name = item[0];
        var user_ids = item[1];
        var reaction = {
            emoji_name: emoji_name,
            emoji_name_css_class: emoji.emojis_name_to_css_class[emoji_name],
            count: user_ids.length,
            title: generate_title(emoji_name, user_ids),
            emoji_alt_code: page_params.emoji_alt_code,
        };
        if (emoji.realm_emojis[reaction.emoji_name]) {
            reaction.is_realm_emoji = true;
            reaction.url = emoji.realm_emojis[reaction.emoji_name].emoji_url;
        }
        if (user_ids.indexOf(page_params.user_id) !== -1) {
            reaction.class = "message_reaction reacted";
        } else {
            reaction.class = "message_reaction";
        }
        return reaction;
    });
    return reactions;
};

$(function () {
    $(document).on('message_id_changed', function (event) {
        // When a message ID is changed via editing, update any
        // data-message-id references to it.
        var elts = $(".message_reactions[data-message-id='" + event.old_id + "']");
        elts.attr("data-message-id", event.new_id);
    });
});

return exports;
}());

if (typeof module !== 'undefined') {
    module.exports = reactions;
}