Proyectos de Subversion Moodle

// This file is part of Moodle - http://moodle.org/

//

// Moodle is free software: you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// Moodle is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**

 * This module will take 2 view states from the message_drawer_view_conversation

 * module and generate a patch that can be given to the

 * message_drawer_view_conversation_renderer module to update the UI.

 *

 * This module should never modify either state. It's purely a read only

 * module.

 *

 * @module     core_message/message_drawer_view_conversation_patcher

 * @copyright  2018 Ryan Wyllie <ryan@moodle.com>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

define(

[

    'jquery',

    'core/user_date',

    'core_message/message_drawer_view_conversation_constants'

],

function(

    $,

    UserDate,

    Constants

) {

    /**

     * Sort messages by day.

     *

     * @param  {Array} messages The list of messages to sort.

     * @param  {Number} midnight User's midnight timestamp.

     * @return {Array} messages sorted by day.

     */

    var sortMessagesByDay = function(messages, midnight) {

        var messagesByDay = messages.reduce(function(carry, message) {

            var timeCreated = message.timeCreated ? message.timeCreated : midnight;

            var dayTimestamp = UserDate.getUserMidnightForTimestamp(timeCreated, midnight);

            if (carry.hasOwnProperty(dayTimestamp)) {

                carry[dayTimestamp].push(message);

            } else {

                carry[dayTimestamp] = [message];

            }

            return carry;

        }, {});

        return Object.keys(messagesByDay).map(function(dayTimestamp) {

            return {

                timestamp: dayTimestamp,

                messages: messagesByDay[dayTimestamp]

            };

        });

    };

    /**

     * Diff 2 arrays using a match function

     *

     * @param  {Array} a The first array.

     * @param  {Array} b The second array.

     * @param  {Function} matchFunction Function used for matching array items.

     * @return {Object} Object containing array items missing from a, array items missing from b

     * and matches

     */

    var diffArrays = function(a, b, matchFunction) {

        // Make copy of it.

        b = b.slice();

        var missingFromA = [];

        var missingFromB = [];

        var matches = [];

        a.forEach(function(current) {

            var found = false;

            var index = 0;

            for (; index < b.length; index++) {

                var next = b[index];

                if (matchFunction(current, next)) {

                    found = true;

                    matches.push({

                        a: current,

                        b: next

                    });

                    break;

                }

            }

            if (found) {

                // This day has been processed so removed it from the list.

                b.splice(index, 1);

            } else {

                // If we couldn't find it in the next messages then it means

                // it needs to be added.

                missingFromB.push(current);

            }

        });

        missingFromA = b;

        return {

            missingFromA: missingFromA,

            missingFromB: missingFromB,

            matches: matches

        };

    };

    /**

     * Find an element in a array based on a matching function.

     *

     * @param  {array} array Array to search.

     * @param  {Function} breakFunction Function to run on array item.

     * @return {*} The array item.

     */

    var findPositionInArray = function(array, breakFunction) {

        var before = null;

        for (var i = 0; i < array.length; i++) {

            var candidate = array[i];

            if (breakFunction(candidate)) {

                return candidate;

            }

        }

        return before;

    };

    /**

     * Check if 2 arrays are equal.

     *

     * @param  {Array} a The first array.

     * @param  {Array} b The second array.

     * @return {Boolean} Are arrays equal.

     */

    var isArrayEqual = function(a, b) {

        // Make shallow copies so that we don't mess with the array sorting.

        a = a.slice();

        b = b.slice();

        a.sort();

        b.sort();

        var aLength = a.length;

        var bLength = b.length;

        if (aLength < 1 && bLength < 1) {

            return true;

        }

        if (aLength != bLength) {

            return false;

        }

        return a.every(function(item, index) {

            return item == b[index];

        });

    };

    /**

     * Do a shallow check to see if two objects appear to be equal. This should

     * only be used for pretty basic objects.

     *

     * @param {Object} a First object to compare.

     * @param {Object} b Second object to compare

     * @return {Bool}

     */

    var isObjectEqual = function(a, b) {

        var aKeys = Object.keys(a);

        var bKeys = Object.keys(b);

        if (aKeys.length != bKeys.length) {

            return false;

        }

        return aKeys.every(function(key) {

            var aVal = a[key];

            var bVal = b[key];

            var aType = typeof aVal;

            var bType = typeof bVal;

            aType = (aVal === null) ? 'null' : aType;

            bType = (aVal === null) ? 'null' : bType;

            aType = (aType === 'object' && Array.isArray(aType)) ? 'array' : aType;

            bType = (bType === 'object' && Array.isArray(bType)) ? 'array' : bType;

            if (aType !== bType) {

                return false;

            }

            switch (aType) {

                case 'object':

                    return isObjectEqual(aVal, bVal);

                case 'array':

                    return isArrayEqual(aVal, bVal);

                default:

                    return a[key] == b[key];

            }

        });

    };

    /**

     * Compare two messages to check if they are equal. This function only checks a subset

     * of the message properties which we know will change rather than all properties.

     *

     * @param {Object} a The first message

     * @param {Object} b The second message

     * @return {Bool}

     */

    var isMessageEqual = function(a, b) {

        return isObjectEqual(

            {

                id: a.id,

                state: a.sendState,

                text: a.text,

                timeCreated: a.timeCreated

            },

            {

                id: b.id,

                state: b.sendState,

                text: b.text,

                timeCreated: b.timeCreated

            }

        );

    };

    /**

     * Build a patch based on days.

     *

     * @param  {Object} current Current list current items.

     * @param  {Array} remove List of days to remove.

     * @param  {Array} add List of days to add.

     * @return {Object} Patch with elements to add and remove.

     */

    var buildDaysPatch = function(current, remove, add) {

        return {

            remove: remove,

            add: add.map(function(day) {

                // Any days left over in the "next" list weren't in the "current" list

                // so they will need to be added.

                var before = findPositionInArray(current, function(candidate) {

                    return day.timestamp < candidate.timestamp;

                });

                return {

                    before: before,

                    value: day

                };

            })

        };

    };

    /**

     * Build the messages patch for each day.

     *

     * @param {Array} matchingDays Array of old and new messages sorted by day.

     * @return {Object} patch.

     */

    var buildMessagesPatch = function(matchingDays) {

        var remove = [];

        var add = [];

        var update = [];

        // Iterate over the list of days and determine which messages in those days

        // have been changed.

        matchingDays.forEach(function(days) {

            var dayCurrent = days.a;

            var dayNext = days.b;

            // Find out which messages have changed in this day. This will return a list of messages

            // from the current state that couldn't be found in the next state and a list of messages in

            // the next state which couldn't be count in the current state.

            var messagesDiff = diffArrays(dayCurrent.messages, dayNext.messages, isMessageEqual);

            // Take the two arrays (list of messages changed from dayNext and list of messages changed

            // from dayCurrent) any work out which messages have been added/removed from the list and

            // which messages were just updated.

            var patch = diffArrays(

                // The messages from dayCurrent.message that weren't in dayNext.messages.

                messagesDiff.missingFromB,

                // The messages from dayNext.message that weren't in dayCurrent.messages.

                messagesDiff.missingFromA,

                function(a, b) {

                    // This function is going to determine if the messages were

                    // added/removed from either list or if they were simply an updated.

                    //

                    // If the IDs match or it was a state change (i.e. message with a temp

                    // ID goes from pending to sent and receives an actual id) then they are

                    // the same message which should be an update not an add/remove.

                    return a.id == b.id || (a.sendState != b.sendState && a.timeAdded == b.timeAdded);

                }

            );

            // Any messages from the current state for this day which aren't in the next state

            // for this day (i.e. the user deleted the message) means we need to remove them from

            // the UI.

            remove = remove.concat(patch.missingFromB);

            // Any messages not in the current state for this day which are in the next state

            // for this day (i.e. it's a new message) means we need to add it to the UI so work

            // out where in the list of messages it should appear (it could be a new message the

            // user has sent or older messages loaded as part of the conversation scroll back).

            patch.missingFromA.forEach(function(message) {

                // By default a null value for before will render the message at the bottom of

                // the message UI (i.e. it's the newest message).

                var before = null;

                if (message.timeCreated) {

                    // If this message has a time created then find where it sits in the list of

                    // message to insert it into the correct position.

                    before = findPositionInArray(dayCurrent.messages, function(candidate) {

                        if (message.timeCreated == candidate.timeCreated) {

                            return message.id < candidate.id;

                        } else {

                            return message.timeCreated < candidate.timeCreated;

                        }

                    });

                }

                add.push({

                    before: before,

                    value: message,

                    day: dayCurrent

                });

            });

            // Any message that appears in both the current state for this day and the next state

            // for this day means something in the message was updated.

            update = update.concat(patch.matches.map(function(message) {

                return {

                    before: message.a,

                    after: message.b

                };

            }));

        });

        return {

            add: add,

            remove: remove,

            update: update

        };

    };

    /**

     * Build a patch for this conversation.

     *

     * @param  {Object} state The current state of this conversation.

     * @param  {Object} newState The new state of this conversation.

     * @returns {Object} Patch with days and messsages for each day.

     */

    var buildConversationPatch = function(state, newState) {

        var diff = diffArrays(state.messages, newState.messages, isMessageEqual);

        if (diff.missingFromA.length || diff.missingFromB.length) {

            // Some messages have changed so let's work out which ones by sorting

            // them into their respective days.

            var current = sortMessagesByDay(state.messages, state.midnight);

            var next = sortMessagesByDay(newState.messages, newState.midnight);

            // This diffs the arrays to work out if there are any missing days that need

            // to be added (i.e. we've got some new messages on a new day) or if there

            // are any days that need to be deleted (i.e. the user has deleted some old messages).

            var daysDiff = diffArrays(current, next, function(dayCurrent, dayNext) {

                return dayCurrent.timestamp == dayNext.timestamp;

            });

            return {

                // Handle adding or removing whole days.

                days: buildDaysPatch(current, daysDiff.missingFromB, daysDiff.missingFromA),

                // Handle updating messages that don't require adding/removing a whole day.

                messages: buildMessagesPatch(daysDiff.matches)

            };

        } else {

            return null;

        }

    };

    /**

     * Build a patch for the header of this conversation. Check if this conversation

     * is a group conversation.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object} patch

     */

    var buildHeaderPatchTypePrivate = function(state, newState) {

        var requireAddContact = buildRequireAddContact(state, newState);

        var confirmContactRequest = buildConfirmContactRequest(state, newState);

        var oldOtherUser = getOtherUserFromState(state);

        var newOtherUser = getOtherUserFromState(newState);

        var requiresAddContact = requireAddContact && requireAddContact.show && !requireAddContact.hasMessages;

        var requiredAddContact = requireAddContact && !requireAddContact.show;

        // Render the header once we've got a user.

        var shouldRenderHeader = !oldOtherUser && newOtherUser;

        // We should also re-render the header if the other user requires

        // being added as a contact or if they did but no longer do.

        shouldRenderHeader = shouldRenderHeader || requiresAddContact || requiredAddContact;

        // Finally, we should re-render if the other user has sent this user

        // a contact request that is waiting for approval or if it's been approved/declined.

        shouldRenderHeader = shouldRenderHeader || confirmContactRequest !== null;

        if (shouldRenderHeader) {

            return {

                type: Constants.CONVERSATION_TYPES.PRIVATE,

                // We can show controls if the other user doesn't require add contact

                // and we aren't waiting for this user to respond to a contact request.

                showControls: !requiresAddContact && !confirmContactRequest,

                context: {

                    id: newState.id,

                    name: newState.name,

                    subname: newState.subname,

                    totalmembercount: newState.totalMemberCount,

                    imageurl: newState.imageUrl,

                    isfavourite: newState.isFavourite,

                    ismuted: newState.isMuted,

                    // Don't show favouriting if we don't have a conversation.

                    showfavourite: newState.id !== null,

                    userid: newOtherUser.id,

                    showonlinestatus: newOtherUser.showonlinestatus,

                    isonline: newOtherUser.isonline,

                    isblocked: newOtherUser.isblocked,

                    iscontact: newOtherUser.iscontact,

                    cancreatecontact: newOtherUser.cancreatecontact,

                }

            };

        }

        return null;

    };

    /**

     * Build a patch for the header of this conversation. Check if this conversation

     * is a group conversation.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object} patch

     */

    var buildHeaderPatchTypeSelf = function(state, newState) {

        var shouldRenderHeader = (state.name === null && newState.name !== null);

        if (shouldRenderHeader) {

            return {

                type: Constants.CONVERSATION_TYPES.SELF,

                // Don't display the controls for the self-conversations.

                showControls: false,

                context: {

                    id: newState.id,

                    name: newState.name,

                    subname: newState.subname,

                    imageurl: newState.imageUrl,

                    isfavourite: newState.isFavourite,

                    // Don't show favouriting if we don't have a conversation.

                    showfavourite: newState.id !== null,

                    showonlinestatus: true,

                }

            };

        }

        return null;

    };

    /**

     * Build a patch for the header of this conversation. Check if this conversation

     * is a group conversation.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object} patch

     */

    var buildHeaderPatchTypePublic = function(state, newState) {

        var oldMemberCount = state.totalMemberCount;

        var newMemberCount = newState.totalMemberCount;

        if (oldMemberCount != newMemberCount) {

            return {

                type: Constants.CONVERSATION_TYPES.PUBLIC,

                showControls: true,

                context: {

                    id: newState.id,

                    name: newState.name,

                    subname: newState.subname,

                    totalmembercount: newState.totalMemberCount,

                    imageurl: newState.imageUrl,

                    isfavourite: newState.isFavourite,

                    ismuted: newState.isMuted,

                    // Don't show favouriting if we don't have a conversation.

                    showfavourite: newState.id !== null

                }

            };

        } else {

            return null;

        }

    };

    /**

     * Find the newest or oldest message.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Number} Oldest or newest message id.

     */

    var buildScrollToMessagePatch = function(state, newState) {

        var oldMessages = state.messages;

        var newMessages = newState.messages;

        if (newMessages.length < 1) {

            return null;

        }

        if (oldMessages.length < 1) {

            return newMessages[newMessages.length - 1].id;

        }

        var previousNewest = oldMessages[state.messages.length - 1];

        var currentNewest = newMessages[newMessages.length - 1];

        var previousOldest = oldMessages[0];

        var currentOldest = newMessages[0];

        if (previousNewest.id != currentNewest.id) {

            return currentNewest.id;

        } else if (previousOldest.id != currentOldest.id) {

            return previousOldest.id;

        }

        return null;

    };

    /**

     * Check if members should be loaded.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildLoadingMembersPatch = function(state, newState) {

        if (!state.loadingMembers && newState.loadingMembers) {

            return true;

        } else if (state.loadingMembers && !newState.loadingMembers) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Check if the messages are being loaded for the first time.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildLoadingFirstMessages = function(state, newState) {

        if (state.hasTriedToLoadMessages === newState.hasTriedToLoadMessages) {

            return null;

        } else if (!newState.hasTriedToLoadMessages && newState.loadingMessages) {

            return true;

        } else if (newState.hasTriedToLoadMessages && !newState.loadingMessages) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Check if the messages are still being loaded

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildLoadingMessages = function(state, newState) {

        if (!state.loadingMessages && newState.loadingMessages) {

            return true;

        } else if (state.loadingMessages && !newState.loadingMessages) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Determine if we should show the emoji picker.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildShowEmojiPicker = function(state, newState) {

        if (!state.showEmojiPicker && newState.showEmojiPicker) {

            return true;

        } else if (state.showEmojiPicker && !newState.showEmojiPicker) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Determine if we should show the emoji auto complete.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildShowEmojiAutoComplete = function(state, newState) {

        if (!state.showEmojiAutoComplete && newState.showEmojiAutoComplete) {

            return true;

        } else if (state.showEmojiAutoComplete && !newState.showEmojiAutoComplete) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Get the user Object of user to be blocked if pending.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object|Bool|Null} User Object if Object.

     */

    var buildConfirmBlockUser = function(state, newState) {

        if (newState.pendingBlockUserIds.length) {

            // We currently only support a single user;

            var userId = newState.pendingBlockUserIds[0];

            return newState.members[userId];

        } else if (state.pendingBlockUserIds.length) {

            return false;

        }

        return null;

    };

    /**

     * Get the user Object of user to be unblocked if pending.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object|Bool|Null} User Object if Object.

     */

    var buildConfirmUnblockUser = function(state, newState) {

        if (newState.pendingUnblockUserIds.length) {

            // We currently only support a single user;

            var userId = newState.pendingUnblockUserIds[0];

            return newState.members[userId];

        } else if (state.pendingUnblockUserIds.length) {

            return false;

        }

        return null;

    };

    /**

     * Get the user Object of user to be added as contact if pending.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object|Bool|Null} User Object if Object.

     */

    var buildConfirmAddContact = function(state, newState) {

        if (newState.pendingAddContactIds.length) {

            // We currently only support a single user;

            var userId = newState.pendingAddContactIds[0];

            return newState.members[userId];

        } else if (state.pendingAddContactIds.length) {

            return false;

        }

        return null;

    };

    /**

     * Get the user Object of user to be removed as contact if pending.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object|Bool|Null} User Object if Object.

     */

    var buildConfirmRemoveContact = function(state, newState) {

        if (newState.pendingRemoveContactIds.length) {

            // We currently only support a single user;

            var userId = newState.pendingRemoveContactIds[0];

            return newState.members[userId];

        } else if (state.pendingRemoveContactIds.length) {

            return false;

        }

        return null;

    };

    /**

     * Check if there are any messages to be deleted.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object|Null} The conversation type and if the user can delete  the messages for all users.

     */

    var buildConfirmDeleteSelectedMessages = function(state, newState) {

        var oldPendingCount = state.pendingDeleteMessageIds.length;

        var newPendingCount = newState.pendingDeleteMessageIds.length;

        if (newPendingCount && !oldPendingCount) {

            return {

                show: true,

                type: newState.type,

                canDeleteMessagesForAllUsers: newState.canDeleteMessagesForAllUsers

            };

        } else if (oldPendingCount && !newPendingCount) {

            return {

                show: false

            };

        }

        return null;

    };

    /**

     * Check if there is a conversation to be deleted.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {int|Null} The conversation type to be deleted.

     */

    var buildConfirmDeleteConversation = function(state, newState) {

        if (!state.pendingDeleteConversation && newState.pendingDeleteConversation) {

            return newState.type;

        } else if (state.pendingDeleteConversation && !newState.pendingDeleteConversation) {

            return false;

        }

        return null;

    };

    /**

     * Check if there is a pending contact request to accept or decline.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildConfirmContactRequest = function(state, newState) {

        var loggedInUserId = state.loggedInUserId;

        var oldOtherUser = getOtherUserFromState(state);

        var newOtherUser = getOtherUserFromState(newState);

        var oldReceivedRequests = !oldOtherUser ? [] : oldOtherUser.contactrequests.filter(function(request) {

            return request.requesteduserid == loggedInUserId && request.userid == oldOtherUser.id;

        });

        var newReceivedRequests = !newOtherUser ? [] : newOtherUser.contactrequests.filter(function(request) {

            return request.requesteduserid == loggedInUserId && request.userid == newOtherUser.id;

        });

        var oldRequest = oldReceivedRequests.length ? oldReceivedRequests[0] : null;

        var newRequest = newReceivedRequests.length ? newReceivedRequests[0] : null;

        if (!oldRequest && newRequest) {

            return newOtherUser;

        } else if (oldRequest && !newRequest) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Check if there are any changes in blocked users.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildIsBlocked = function(state, newState) {

        var oldOtherUser = getOtherUserFromState(state);

        var newOtherUser = getOtherUserFromState(newState);

        if (!oldOtherUser && !newOtherUser) {

            return null;

        } else if (!oldOtherUser && newOtherUser) {

            return newOtherUser.isblocked ? true : null;

        } else if (!newOtherUser && oldOtherUser) {

            return oldOtherUser.isblocked ? false : null;

        } else if (oldOtherUser.isblocked && !newOtherUser.isblocked) {

            return false;

        } else if (!oldOtherUser.isblocked && newOtherUser.isblocked) {

            return true;

        } else {

            return null;

        }

    };

    /**

     * Check if there are any changes the conversation favourite state.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildIsFavourite = function(state, newState) {

        var oldIsFavourite = state.isFavourite;

        var newIsFavourite = newState.isFavourite;

        if (state.id === null && newState.id === null) {

            // The conversation isn't yet created so don't change anything.

            return null;

        } else if (state.id === null && newState.id !== null) {

            // The conversation was created so we can show the add favourite button.

            return 'show-add';

        } else if (state.id !== null && newState.id === null) {

            // We're changing from a created conversation to a new conversation so hide

            // the favouriting functionality for now.

            return 'hide';

        } else if (oldIsFavourite == newIsFavourite) {

            // No change.

            return null;

        } else if (!oldIsFavourite && newIsFavourite) {

            return 'show-remove';

        } else if (oldIsFavourite && !newIsFavourite) {

            return 'show-add';

        } else {

            return null;

        }

    };

    /**

     * Check if there are any changes the conversation muted state.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {string|null}

     */

    var buildIsMuted = function(state, newState) {

        var oldIsMuted = state.isMuted;

        var newIsMuted = newState.isMuted;

        if (state.id === null && newState.id === null) {

            // The conversation isn't yet created so don't change anything.

            return null;

        } else if (state.id === null && newState.id !== null) {

            // The conversation was created so we can show the mute button.

            return 'show-mute';

        } else if (state.id !== null && newState.id === null) {

            // We're changing from a created conversation to a new conversation so hide

            // the muting functionality for now.

            return 'hide';

        } else if (oldIsMuted == newIsMuted) {

            // No change.

            return null;

        } else if (!oldIsMuted && newIsMuted) {

            return 'show-unmute';

        } else if (oldIsMuted && !newIsMuted) {

            return 'show-mute';

        } else {

            return null;

        }

    };

    /**

     * Check if there are any changes in the contact status of the current user

     * and other user.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildIsContact = function(state, newState) {

        var loggedInUserId = state.loggedInUserId;

        var oldOtherUser = getOtherUserFromState(state);

        var newOtherUser = getOtherUserFromState(newState);

        var oldContactRequests = !oldOtherUser ? [] : oldOtherUser.contactrequests.filter(function(request) {

            return (request.userid == loggedInUserId && request.requesteduserid == oldOtherUser.id) ||

                (request.userid == oldOtherUser.id && request.requesteduserid == loggedInUserId);

        });

        var newContactRequests = !newOtherUser ? [] : newOtherUser.contactrequests.filter(function(request) {

            return (request.userid == loggedInUserId && request.requesteduserid == newOtherUser.id) ||

                (request.userid == newOtherUser.id && request.requesteduserid == loggedInUserId);

        });

        var oldHasContactRequests = oldContactRequests.length > 0;

        var newHasContactRequests = newContactRequests.length > 0;

        if (!oldOtherUser && !newOtherUser) {

            return null;

        } else if (oldHasContactRequests && newHasContactRequests) {

            return null;

        } else if (!oldHasContactRequests && newHasContactRequests && !newOtherUser.iscontact) {

            return 'pending-contact';

        } else if (!oldOtherUser && newOtherUser) {

            return newOtherUser.iscontact ? 'contact' : null;

        } else if (!newOtherUser && oldOtherUser) {

            return oldOtherUser.iscontact ? 'non-contact' : null;

        } else if (oldOtherUser.iscontact && !newOtherUser.iscontact) {

            return newHasContactRequests ? 'pending-contact' : 'non-contact';

        } else if (!oldOtherUser.iscontact && newOtherUser.iscontact) {

            return 'contact';

        } else {

            return null;

        }

    };

    /**

     * Check if a confirm action is active.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildLoadingConfirmationAction = function(state, newState) {

        if (!state.loadingConfirmAction && newState.loadingConfirmAction) {

            return true;

        } else if (state.loadingConfirmAction && !newState.loadingConfirmAction) {

            return false;

        } else {

            return null;

        }

    };

    /**

     * Check if a edit mode is active.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Bool|Null}

     */

    var buildInEditMode = function(state, newState) {

        var oldHasSelectedMessages = state.selectedMessageIds.length > 0;

        var newHasSelectedMessages = newState.selectedMessageIds.length > 0;

        var numberOfMessagesHasChanged = state.messages.length != newState.messages.length;

        if (!oldHasSelectedMessages && newHasSelectedMessages) {

            return true;

        } else if (oldHasSelectedMessages && !newHasSelectedMessages) {

            return false;

        } else if (oldHasSelectedMessages && numberOfMessagesHasChanged) {

            return true;

        } else {

            return null;

        }

    };

    /**

     * Build a patch for the messages selected.

     *

     * @param  {Object} state The current state.

     * @param  {Object} newState The new state.

     * @return {Object} patch

     */

    var buildSelectedMessages = function(state, newState) {

        var oldSelectedMessages = state.selectedMessageIds;

        var newSelectedMessages = newState.selectedMessageIds;

        if (isArrayEqual(oldSelectedMessages, newSelectedMessages)) {

            return null;

        }

        var diff = diffArrays(oldSelectedMessages, newSelectedMessages, function(a, b) {

            return a == b;

        });

        return {

            count: newSelectedMessages.length,

            add: diff.missingFromA,

            remove: diff.missingFromB

        };

    };

    /**

     * Get a list of users from the state that are not the logged in user. Use to find group

     * message members or the other user in a conversation.

     *

     * @param  {Object} state State

     * @return {Array} List of users.

     */

    var getOtherUserFromState = function(state) {

        return Object.keys(state.members).reduce(function(carry, userId) {

            if (userId != state.loggedInUserId && !carry) {

                carry = state.members[userId];

            }

            return carry;

        }, null);

    };

    /**

     * Check if the given user requires a contact request from the logged in user.

     *

     * @param  {Integer} loggedInUserId The logged in user id

     * @param  {Object} user User record

     * @return {Bool}

     */

    var requiresContactRequest = function(loggedInUserId, user) {

        // If a user can message then no contact request is required.

        if (user.canmessage) {

            return false;

        }