filter: Add helpers for updated navbar features.

This is a prep commit for changes to the top navbar, it adds helpers
to filter.js which will help control the behavior of some aspects of
the redesigned navbar.

Modified by tabbott to add comments, internationalization tags on the
strings, support streams:public, and change various title strings.

static/js/filter.js

@@ -148,12 +148,20 @@ function message_matches_search_term(message, operator, operand) {
     return true; // unknown operators return true (effectively ignored)
 }
 
-
 function Filter(operators) {
     if (operators === undefined) {
         this._operators = [];
     } else {
         this._operators = this.fix_operators(operators);
+        // if has_op stream
+        if (this.has_operator('stream')) {
+            const stream_name_from_search = this.operands('stream')[0];
+            const sub = stream_data.get_sub_by_name(stream_name_from_search);
+            if (sub) {
+                this._stream_name = sub.name;
+                this._is_stream_private = sub.invite_only;
+            }
+        }
     }
 }
 
@@ -401,6 +409,7 @@ Filter.prototype = {
         // TODO: Some users really hate it when Zulip marks messages as read
         // in interleaved views, so we will eventually have a setting
         // that early-exits before the subsequent checks.
+        // (in which case, is_common_narrow would also need to be modified)
 
         if (_.isEqual(term_types, ['stream'])) {
             return true;
@@ -433,6 +442,143 @@ Filter.prototype = {
         return this._can_mark_messages_read;
     },
 
+    // This is used to control the behaviour for "exiting search",
+    // given the ability to flip between displaying the search bar and the narrow description in UI
+    // here we define a narrow as a "common narrow" on the basis of
+    // https://paper.dropbox.com/doc/Navbar-behavior-table--AvnMKN4ogj3k2YF5jTbOiVv_AQ-cNOGtu7kSdtnKBizKXJge
+    // common narrows show a narrow description and allow the user to
+    // close search bar UI and show the narrow description UI.
+    //
+    // TODO: We likely will want to rewrite this to not piggy-back on
+    // can_mark_messages_read, since that might gain some more complex behavior
+    // with near: narrows.
+    is_common_narrow: function () {
+        // can_mark_messages_read tests the following filters:
+        // stream, stream + topic,
+        // is: private, pm-with:,
+        // is: mentioned
+        if (this.can_mark_messages_read()) {
+            return true;
+        }
+        // that leaves us with checking:
+        // is: starred
+        // (which can_mark_messages_read_does not check as starred messages are always read)
+        const term_types = this.sorted_term_types();
+
+        if (_.isEqual(term_types, ['is-starred'])) {
+            return true;
+        }
+        if (_.isEqual(term_types, ['streams-public'])) {
+            return true;
+        }
+        return false;
+    },
+
+    // This is used to control the behaviour for "exiting search"
+    // within a narrow (E.g. a stream/topic + search) to bring you to
+    // the containing common narrow (stream/topic, in the example)
+    // rather than "All messages".
+    //
+    // Note from tabbott: The slug-based approach may not be ideal; we
+    // may be able to do better another way.
+    generate_redirect_url: function () {
+        const term_types = this.sorted_term_types();
+
+        // this comes first because it has 3 term_types but is not a "complex filter"
+        if (_.isEqual(term_types, ['stream', 'topic', 'search'])) {
+            return  '/#narrow/stream/' + stream_data.name_to_slug(this.operands('stream')[0]) + '/topic/' + this.operands('topic')[0];
+        }
+
+        // eliminate "complex filters"
+        if (term_types.length >= 3) {
+            return "#"; // redirect to All
+        }
+
+        if (term_types[1] === 'search') {
+            switch (term_types[0]) {
+            case 'stream':
+                return  '/#narrow/stream/' + stream_data.name_to_slug(this.operands('stream')[0]);
+            case 'is-private':
+                return  '/#narrow/is/private';
+            case 'is-starred':
+                return  '/#narrow/is/starred';
+            case 'is-mentioned':
+                return  '/#narrow/is/mentioned';
+            case 'streams-public':
+                return  '/#narrow/streams/public';
+            case 'pm-with':
+                // join is used to transform the array to a comma separated string
+                return  '/#narrow/pm-with/' + people.emails_to_slug(this.operands('pm-with').join());
+                // TODO: It is ambiguous how we want to handle the 'sender' case,
+                // we may remove it in the future based on design decisions
+            case 'sender':
+                return  '/#narrow/sender/' + people.emails_to_slug(this.operands('sender')[0]);
+            }
+        }
+
+        return "#"; // redirect to All
+    },
+
+    get_icon: function () {
+        // We have special icons for the simple narrows available for the via sidebars.
+        const term_types = this.sorted_term_types();
+        switch (term_types[0]) {
+        case 'in-home':
+        case 'in-all':
+            return 'home';
+        case 'stream':
+            if (this._is_stream_private) {
+                return 'lock';
+            }
+            return 'hashtag';
+        case 'is-private':
+            return 'envelope';
+        case 'is-starred':
+            return 'star';
+        case 'is-mentioned':
+            return 'at';
+        case 'pm-with':
+            return 'envelope';
+        }
+    },
+
+    get_title: function () {
+        // Nice explanatory titles for common views.
+        const term_types = this.sorted_term_types();
+        if (term_types.length === 3 && _.isEqual(term_types, ['stream', 'topic', 'search']) ||
+            term_types.length === 2 && _.isEqual(term_types, ['stream', 'topic'])) {
+            return this._stream_name;
+        }
+        if (term_types.length === 1 || term_types.length === 2 && term_types[1] === 'search') {
+            switch (term_types[0]) {
+            case 'in-home':
+                return i18n.t('All messages');
+            case 'in-all':
+                return i18n.t('All messages including muted streams');
+            case 'streams-public':
+                return i18n.t('Public stream messages in organization');
+            case 'stream':
+                return this._stream_name;
+            case 'is-starred':
+                return i18n.t('Starred messages');
+            case 'is-mentioned':
+                return i18n.t('Mentions');
+            case 'is-private':
+                return i18n.t('Private messages');
+            case 'pm-with': {
+                const emails = this.operands('pm-with')[0].split(',');
+                const names = emails.map(email => {
+                    if (!people.get_by_email(email)) {
+                        return email;
+                    }
+                    return people.get_by_email(email).full_name;
+                });
+                return names;
+            }
+            }
+        }
+    },
+
     allow_use_first_unread_when_narrowing: function () {
         return this.can_mark_messages_read() || this.has_operator('is');
     },