[libgweather/ebassi/issue-161] location: Add getter for time zone name

[Emmanuele Bassi <ebassi src gnome org>]

commit 5adbc470187e58f090b39f32a57d00925cde181c
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Jan 13 02:41:02 2022 +0000

    location: Add getter for time zone name
    
    When I removed GWeatherTimezone I inadvertedly missed the only
    functionality that the type provided on top of GTimeZone, and that
    is: the ability to retrieve the human readable, localised name of the
    time zone bound to a location. That information does not exist in the
    time zone database as parsed by GLib, but it is available in GWeather's
    location database. This means we need to retrieve the time zone reference
    from the location's database, just like we do for
    gweather_location_get_timezone(), and from that reference we retrieve the
    localised string with the time zone name.
    
    The old GWeather-3 API allowed retrieving the name for any given
    GWeatherTimezone, but since all time zones are bound to a location, we can
    skip that particular aspect of the API.
    
    Fixes: #161

 libgweather/gweather-location.c | 92 +++++++++++++++++++++++++++++++++++++++++
 libgweather/gweather-location.h |  3 ++
 libgweather/tests/timezones.c   | 13 ++++++
 3 files changed, 108 insertions(+)
---
diff --git a/libgweather/gweather-location.c b/libgweather/gweather-location.c
index 0ad5adcf..9d8a62cb 100644
--- a/libgweather/gweather-location.c
+++ b/libgweather/gweather-location.c
@@ -1063,6 +1063,98 @@ gweather_location_get_timezone_str (GWeatherLocation *loc)
     return NULL;
 }
 
+static const char *
+timezone_ref_get_name (GWeatherDb *db,
+                       guint16 idx)
+{
+    DbWorldTimezonesEntryRef entry_ref = db_world_timezones_get_at (db->timezones_ref, idx);
+
+    DbTimezoneRef tz_ref = db_world_timezones_entry_get_value (entry_ref);
+    DbI18nRef tz_name = db_timezone_get_name (tz_ref);
+
+    const char *name = EMPTY_TO_NULL (db_i18n_get_str (tz_name));
+    const char *msgctxt = EMPTY_TO_NULL (db_i18n_get_msgctxt (tz_name));
+
+    if (name != NULL) {
+        if (msgctxt != NULL) {
+            return g_dpgettext2 (LOCATIONS_GETTEXT_PACKAGE, msgctxt, name);
+        } else {
+            return g_dgettext (LOCATIONS_GETTEXT_PACKAGE, name);
+        }
+    }
+
+    return NULL;
+}
+
+/**
+ * gweather_location_get_timezone_name:
+ * @loc: the location to query
+ * @tzid: (nullable): the identifier of a timezone
+ *
+ * Retrieves the human readable, localized name of the timezone available
+ * at the given location, if any.
+ *
+ * If @tzid is omitted then the returned name will be the one of the first
+ * available timezone.
+ *
+ * Returns: (transfer none) (nullable): the human readable name of the
+ *   location's timezone
+ */
+const char *
+gweather_location_get_timezone_name (GWeatherLocation *loc,
+                                     const char *tzid)
+{
+    g_autoptr (GWeatherLocation) s = NULL;
+
+    g_return_val_if_fail (GWEATHER_IS_LOCATION (loc), NULL);
+
+    ITER_UP (loc, s) {
+        /* NOTE: Only DB backed locations can have timezones */
+        if (s->db && IDX_VALID (s->db_idx)) {
+            if (tzid == NULL && IDX_VALID (s->tz_hint_idx)) {
+                return timezone_ref_get_name (s->db, s->tz_hint_idx);
+            }
+
+            DbArrayofuint16Ref ref;
+            gsize len;
+
+            ref = db_location_get_timezones (loc->ref);
+            len = db_arrayofuint16_get_length (ref);
+
+            if (len == 0) {
+                continue;
+            }
+
+            guint16 tz_idx;
+            if (tzid == NULL) {
+                tz_idx = 0;
+            } else {
+                gboolean found = FALSE;
+
+                for (gsize i = 0; i < len; i++) {
+                    tz_idx = db_arrayofuint16_get_at (ref, i);
+
+                    DbWorldTimezonesEntryRef entry_ref =
+                        db_world_timezones_get_at (s->db->timezones_ref, tz_idx);
+
+                    const char *id = db_world_timezones_entry_get_key (entry_ref);
+                    if (strcmp (id, tzid) == 0) {
+                        found = TRUE;
+                        break;
+                    }
+                }
+
+                if (!found)
+                    continue;
+            }
+
+            return timezone_ref_get_name (s->db, tz_idx);
+        }
+    }
+
+    return NULL;
+}
+
 static void
 add_timezones (GWeatherLocation *loc,
                GPtrArray *zones)
diff --git a/libgweather/gweather-location.h b/libgweather/gweather-location.h
index 4e33a108..bddfd9bf 100644
--- a/libgweather/gweather-location.h
+++ b/libgweather/gweather-location.h
@@ -147,6 +147,9 @@ GTimeZone *             gweather_location_get_timezone          (GWeatherLocatio
 GWEATHER_AVAILABLE_IN_ALL
 const char *            gweather_location_get_timezone_str      (GWeatherLocation  *loc);
 GWEATHER_AVAILABLE_IN_ALL
+const char *            gweather_location_get_timezone_name     (GWeatherLocation  *loc,
+                                                                 const char        *tzid);
+GWEATHER_AVAILABLE_IN_ALL
 GTimeZone **            gweather_location_get_timezones         (GWeatherLocation  *loc);
 GWEATHER_AVAILABLE_IN_ALL
 void                    gweather_location_free_timezones        (GWeatherLocation  *loc,
diff --git a/libgweather/tests/timezones.c b/libgweather/tests/timezones.c
index 5475c223..312b80da 100644
--- a/libgweather/tests/timezones.c
+++ b/libgweather/tests/timezones.c
@@ -147,6 +147,19 @@ test_timezone (GWeatherLocation *location)
         tzs = gweather_location_get_timezones (location);
         g_assert_nonnull (tzs);
 
+        for (int i = 0; tzs[i] != NULL; i++) {
+            GTimeZone *tz = tzs[i];
+
+            const char *tz_id = g_time_zone_get_identifier (tz);
+            const char *tz_name = gweather_location_get_timezone_name (location, tz_id);
+            g_test_message ("Location '%s': timezone (%s) = '%s'",
+                            gweather_location_get_name (location),
+                            tz_id,
+                            tz_name);
+
+            g_assert_nonnull (tz_name);
+        }
+
         /* Only countries should have multiple timezones associated */
         if ((tzs[0] == NULL && gweather_location_get_level (location) < GWEATHER_LOCATION_WEATHER_STATION) &&
             gweather_location_get_level (location) >= GWEATHER_LOCATION_COUNTRY) {