as-content-rating: Add content rating system APIs from gnome-software

These are moving to libappstream-glib as they are used by gnome-software
and libmalcontent-ui, and are potentially useful in other projects. In
particular, there are a number of translatable strings which need to be
centralised so that translation work isn’t repeated.

This code was originally written by:
 • Richard Hughes <richard@hughsie.com>
 • Piotr Drąg <piotrdrag@gmail.com>
 • Philip Withnall <withnall@endlessm.com>
 • Jordi Mas <jmas@softcatala.org>

It was previously in `src/gs-content-rating.[ch]` in gnome-software,
under the GPL-2.0+; and in `libmalcontent-ui/gs-content-rating.[ch]` in
malcontent, also under the GPL-2.0+. It has been relicensed from
GPL-2.0+ to LGPL-2.1+ for the move to appstream-glib, and all the
previous contributors have agreed. See
https://github.com/hughsie/appstream-glib/pull/364#issuecomment-632773905
and below for their agreements.

In moving it from one project to the other, I have added documentation
comments and tweaked some of the APIs to make them more usable.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

4 files changed, 1054 insertions, 0 deletions

diff --git a/libappstream-glib/as-content-rating.c b/libappstream-glib/as-content-rating.c
index 11bc20d..936923d 100644
--- a/libappstream-glib/as-content-rating.c
+++ b/libappstream-glib/as-content-rating.c
@@ -18,6 +18,8 @@
 
 #include "config.h"
 
+#include <glib/gi18n-lib.h>
+
 #include "as-node-private.h"
 #include "as-content-rating-private.h"
 #include "as-ref-string.h"
@@ -209,6 +211,905 @@ as_content_rating_value_from_string (const gchar *value)
 	return AS_CONTENT_RATING_VALUE_UNKNOWN;
 }
 
+static const gchar *rating_system_names[] = {
+	[AS_CONTENT_RATING_SYSTEM_UNKNOWN] = NULL,
+	[AS_CONTENT_RATING_SYSTEM_INCAA] = "INCAA",
+	[AS_CONTENT_RATING_SYSTEM_ACB] = "ACB",
+	[AS_CONTENT_RATING_SYSTEM_DJCTQ] = "DJCTQ",
+	[AS_CONTENT_RATING_SYSTEM_GSRR] = "GSRR",
+	[AS_CONTENT_RATING_SYSTEM_PEGI] = "PEGI",
+	[AS_CONTENT_RATING_SYSTEM_KAVI] = "KAVI",
+	[AS_CONTENT_RATING_SYSTEM_USK] = "USK",
+	[AS_CONTENT_RATING_SYSTEM_ESRA] = "ESRA",
+	[AS_CONTENT_RATING_SYSTEM_CERO] = "CERO",
+	[AS_CONTENT_RATING_SYSTEM_OFLCNZ] = "OFLCNZ",
+	[AS_CONTENT_RATING_SYSTEM_RUSSIA] = "RUSSIA",
+	[AS_CONTENT_RATING_SYSTEM_MDA] = "MDA",
+	[AS_CONTENT_RATING_SYSTEM_GRAC] = "GRAC",
+	[AS_CONTENT_RATING_SYSTEM_ESRB] = "ESRB",
+	[AS_CONTENT_RATING_SYSTEM_IARC] = "IARC",
+};
+G_STATIC_ASSERT (G_N_ELEMENTS (rating_system_names) == AS_CONTENT_RATING_SYSTEM_LAST);
+
+/**
+ * as_content_rating_system_to_string:
+ * @system: an #AsContentRatingSystem
+ *
+ * Get a human-readable string to identify @system. %NULL will be returned for
+ * %AS_CONTENT_RATING_SYSTEM_UNKNOWN.
+ *
+ * Returns: (nullable): a human-readable string for @system, or %NULL if unknown
+ * Since: 0.7.18
+ */
+const gchar *
+as_content_rating_system_to_string (AsContentRatingSystem system)
+{
+	if ((gint) system < AS_CONTENT_RATING_SYSTEM_UNKNOWN ||
+	    (gint) system >= AS_CONTENT_RATING_SYSTEM_LAST)
+		return NULL;
+
+	return rating_system_names[system];
+}
+
+static char *
+get_esrb_string (const gchar *source, const gchar *translate)
+{
+	if (g_strcmp0 (source, translate) == 0)
+		return g_strdup (source);
+	/* TRANSLATORS: This is the formatting of English and localized name
+	 * of the rating e.g. "Adults Only (solo adultos)" */
+	return g_strdup_printf (_("%s (%s)"), source, translate);
+}
+
+/**
+ * as_content_rating_system_format_age:
+ * @system: an #AsContentRatingSystem
+ * @age: a CSM age to format
+ *
+ * Format @age as a human-readable string in the given rating @system. This is
+ * the way to present system-specific strings in a UI.
+ *
+ * Returns: (transfer full) (nullable): a newly allocated formatted version of
+ *    @age, or %NULL if the given @system has no representation for @age
+ * Since: 0.7.18
+ */
+/* data obtained from https://en.wikipedia.org/wiki/Video_game_rating_system */
+gchar *
+as_content_rating_system_format_age (AsContentRatingSystem system, guint age)
+{
+	if (system == AS_CONTENT_RATING_SYSTEM_INCAA) {
+		if (age >= 18)
+			return g_strdup ("+18");
+		if (age >= 13)
+			return g_strdup ("+13");
+		return g_strdup ("ATP");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_ACB) {
+		if (age >= 18)
+			return g_strdup ("R18+");
+		if (age >= 15)
+			return g_strdup ("MA15+");
+		return g_strdup ("PG");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_DJCTQ) {
+		if (age >= 18)
+			return g_strdup ("18");
+		if (age >= 16)
+			return g_strdup ("16");
+		if (age >= 14)
+			return g_strdup ("14");
+		if (age >= 12)
+			return g_strdup ("12");
+		if (age >= 10)
+			return g_strdup ("10");
+		return g_strdup ("L");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_GSRR) {
+		if (age >= 18)
+			return g_strdup ("限制");
+		if (age >= 15)
+			return g_strdup ("輔15");
+		if (age >= 12)
+			return g_strdup ("輔12");
+		if (age >= 6)
+			return g_strdup ("保護");
+		return g_strdup ("普通");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_PEGI) {
+		if (age >= 18)
+			return g_strdup ("18");
+		if (age >= 16)
+			return g_strdup ("16");
+		if (age >= 12)
+			return g_strdup ("12");
+		if (age >= 7)
+			return g_strdup ("7");
+		if (age >= 3)
+			return g_strdup ("3");
+		return NULL;
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_KAVI) {
+		if (age >= 18)
+			return g_strdup ("18+");
+		if (age >= 16)
+			return g_strdup ("16+");
+		if (age >= 12)
+			return g_strdup ("12+");
+		if (age >= 7)
+			return g_strdup ("7+");
+		if (age >= 3)
+			return g_strdup ("3+");
+		return NULL;
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_USK) {
+		if (age >= 18)
+			return g_strdup ("18");
+		if (age >= 16)
+			return g_strdup ("16");
+		if (age >= 12)
+			return g_strdup ("12");
+		if (age >= 6)
+			return g_strdup ("6");
+		return g_strdup ("0");
+	}
+	/* Reference: http://www.esra.org.ir/ */
+	if (system == AS_CONTENT_RATING_SYSTEM_ESRA) {
+		if (age >= 18)
+			return g_strdup ("+18");
+		if (age >= 15)
+			return g_strdup ("+15");
+		if (age >= 12)
+			return g_strdup ("+12");
+		if (age >= 7)
+			return g_strdup ("+7");
+		if (age >= 3)
+			return g_strdup ("+3");
+		return NULL;
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_CERO) {
+		if (age >= 18)
+			return g_strdup ("Z");
+		if (age >= 17)
+			return g_strdup ("D");
+		if (age >= 15)
+			return g_strdup ("C");
+		if (age >= 12)
+			return g_strdup ("B");
+		return g_strdup ("A");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_OFLCNZ) {
+		if (age >= 18)
+			return g_strdup ("R18");
+		if (age >= 16)
+			return g_strdup ("R16");
+		if (age >= 15)
+			return g_strdup ("R15");
+		if (age >= 13)
+			return g_strdup ("R13");
+		return g_strdup ("G");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_RUSSIA) {
+		if (age >= 18)
+			return g_strdup ("18+");
+		if (age >= 16)
+			return g_strdup ("16+");
+		if (age >= 12)
+			return g_strdup ("12+");
+		if (age >= 6)
+			return g_strdup ("6+");
+		return g_strdup ("0+");
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_MDA) {
+		if (age >= 18)
+			return g_strdup ("M18");
+		if (age >= 16)
+			return g_strdup ("ADV");
+		return get_esrb_string ("General", _("General"));
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_GRAC) {
+		if (age >= 18)
+			return g_strdup ("18");
+		if (age >= 15)
+			return g_strdup ("15");
+		if (age >= 12)
+			return g_strdup ("12");
+		return get_esrb_string ("ALL", _("ALL"));
+	}
+	if (system == AS_CONTENT_RATING_SYSTEM_ESRB) {
+		if (age >= 18)
+			return get_esrb_string ("Adults Only", _("Adults Only"));
+		if (age >= 17)
+			return get_esrb_string ("Mature", _("Mature"));
+		if (age >= 13)
+			return get_esrb_string ("Teen", _("Teen"));
+		if (age >= 10)
+			return get_esrb_string ("Everyone 10+", _("Everyone 10+"));
+		if (age >= 6)
+			return get_esrb_string ("Everyone", _("Everyone"));
+
+		return get_esrb_string ("Early Childhood", _("Early Childhood"));
+	}
+	/* IARC = everything else */
+	if (age >= 18)
+		return g_strdup ("18+");
+	if (age >= 16)
+		return g_strdup ("16+");
+	if (age >= 12)
+		return g_strdup ("12+");
+	if (age >= 7)
+		return g_strdup ("7+");
+	if (age >= 3)
+		return g_strdup ("3+");
+	return NULL;
+}
+
+static const gchar *content_rating_strings[AS_CONTENT_RATING_SYSTEM_LAST][7] = {
+	/* AS_CONTENT_RATING_SYSTEM_UNKNOWN is handled in code */
+	[AS_CONTENT_RATING_SYSTEM_INCAA] = { "ATP", "+13", "+18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_ACB] = { "PG", "MA15+", "R18+", NULL },
+	[AS_CONTENT_RATING_SYSTEM_DJCTQ] = { "L", "10", "12", "14", "16", "18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_GSRR] = { "普通", "保護", "輔12", "輔15", "限制", NULL },
+	[AS_CONTENT_RATING_SYSTEM_PEGI] = { "3", "7", "12", "16", "18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_KAVI] = { "3+", "7+", "12+", "16+", "18+", NULL },
+	[AS_CONTENT_RATING_SYSTEM_USK] = { "0", "6", "12", "16", "18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_ESRA] = { "+3", "+7", "+12", "+15", "+18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_CERO] = { "A", "B", "C", "D", "Z", NULL },
+	[AS_CONTENT_RATING_SYSTEM_OFLCNZ] = { "G", "R13", "R15", "R16", "R18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_RUSSIA] = { "0+", "6+", "12+", "16+", "18+", NULL },
+	[AS_CONTENT_RATING_SYSTEM_MDA] = { "General", "ADV", "M18", NULL },
+	[AS_CONTENT_RATING_SYSTEM_GRAC] = { "ALL", "12", "15", "18", NULL },
+	/* Note: ESRB has locale-specific suffixes, so needs special further
+	 * handling in code. These strings are just the locale-independent parts. */
+	[AS_CONTENT_RATING_SYSTEM_ESRB] = { "Early Childhood", "Everyone", "Everyone 10+", "Teen", "Mature", "Adults Only", NULL },
+	[AS_CONTENT_RATING_SYSTEM_IARC] = { "3+", "7+", "12+", "16+", "18+", NULL },
+};
+
+/**
+ * as_content_rating_system_get_formatted_ages:
+ * @system: an #AsContentRatingSystem
+ *
+ * Get an array of all the possible return values of
+ * as_content_rating_system_format_age() for the given @system. The array is
+ * sorted with youngest CSM age first.
+ *
+ * Returns: (transfer full): %NULL-terminated array of human-readable age strings
+ * Since: 0.7.18
+ */
+gchar **
+as_content_rating_system_get_formatted_ages (AsContentRatingSystem system)
+{
+	g_return_val_if_fail ((int) system < AS_CONTENT_RATING_SYSTEM_LAST, NULL);
+
+	/* IARC is the fallback for everything */
+	if (system == AS_CONTENT_RATING_SYSTEM_UNKNOWN)
+		system = AS_CONTENT_RATING_SYSTEM_IARC;
+
+	/* ESRB is special as it requires localised suffixes */
+	if (system == AS_CONTENT_RATING_SYSTEM_ESRB) {
+		g_auto(GStrv) esrb_ages = g_new0 (gchar *, 7);
+
+		esrb_ages[0] = get_esrb_string (content_rating_strings[system][0], _("Early Childhood"));
+		esrb_ages[1] = get_esrb_string (content_rating_strings[system][1], _("Everyone"));
+		esrb_ages[2] = get_esrb_string (content_rating_strings[system][2], _("Everyone 10+"));
+		esrb_ages[3] = get_esrb_string (content_rating_strings[system][3], _("Teen"));
+		esrb_ages[4] = get_esrb_string (content_rating_strings[system][4], _("Mature"));
+		esrb_ages[5] = get_esrb_string (content_rating_strings[system][5], _("Adults Only"));
+		esrb_ages[6] = NULL;
+
+		return g_steal_pointer (&esrb_ages);
+	}
+
+	return g_strdupv ((gchar **) content_rating_strings[system]);
+}
+
+static guint content_rating_csm_ages[AS_CONTENT_RATING_SYSTEM_LAST][7] = {
+	/* AS_CONTENT_RATING_SYSTEM_UNKNOWN is handled in code */
+	[AS_CONTENT_RATING_SYSTEM_INCAA] = { 0, 13, 18 },
+	[AS_CONTENT_RATING_SYSTEM_ACB] = { 0, 15, 18 },
+	[AS_CONTENT_RATING_SYSTEM_DJCTQ] = { 0, 10, 12, 14, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_GSRR] = { 0, 6, 12, 15, 18 },
+	[AS_CONTENT_RATING_SYSTEM_PEGI] = { 3, 7, 12, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_KAVI] = { 3, 7, 12, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_USK] = { 0, 6, 12, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_ESRA] = { 3, 7, 12, 15, 18 },
+	[AS_CONTENT_RATING_SYSTEM_CERO] = { 0, 12, 15, 17, 18 },
+	[AS_CONTENT_RATING_SYSTEM_OFLCNZ] = { 0, 13, 15, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_RUSSIA] = { 0, 6, 12, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_MDA] = { 0, 16, 18 },
+	[AS_CONTENT_RATING_SYSTEM_GRAC] = { 0, 12, 15, 18 },
+	[AS_CONTENT_RATING_SYSTEM_ESRB] = { 0, 6, 10, 13, 17, 18 },
+	[AS_CONTENT_RATING_SYSTEM_IARC] = { 3, 7, 12, 16, 18 },
+};
+
+/**
+ * as_content_rating_system_get_csm_ages:
+ * @system: an #AsContentRatingSystem
+ * @length_out: (out) (not optional): return location for the length of the
+ *    returned array
+ *
+ * Get the CSM ages corresponding to the entries returned by
+ * as_content_rating_system_get_formatted_ages() for this @system.
+ *
+ * Returns: (transfer container) (array length=length_out): an array of CSM ages
+ * Since: 0.7.18
+ */
+const guint *
+as_content_rating_system_get_csm_ages (AsContentRatingSystem system, gsize *length_out)
+{
+	g_return_val_if_fail ((int) system < AS_CONTENT_RATING_SYSTEM_LAST, NULL);
+	g_return_val_if_fail (length_out != NULL, NULL);
+
+	/* IARC is the fallback for everything */
+	if (system == AS_CONTENT_RATING_SYSTEM_UNKNOWN)
+		system = AS_CONTENT_RATING_SYSTEM_IARC;
+
+	*length_out = g_strv_length ((gchar **) content_rating_strings[system]);
+	return content_rating_csm_ages[system];
+}
+
+/*
+ * parse_locale:
+ * @locale: (transfer full): a locale to parse
+ * @language_out: (out) (optional) (nullable): return location for the parsed
+ *    language, or %NULL to ignore
+ * @territory_out: (out) (optional) (nullable): return location for the parsed
+ *    territory, or %NULL to ignore
+ * @codeset_out: (out) (optional) (nullable): return location for the parsed
+ *    codeset, or %NULL to ignore
+ * @modifier_out: (out) (optional) (nullable): return location for the parsed
+ *    modifier, or %NULL to ignore
+ *
+ * Parse @locale as a locale string of the form
+ * `language[_territory][.codeset][@modifier]` — see `man 3 setlocale` for
+ * details.
+ *
+ * On success, %TRUE will be returned, and the components of the locale will be
+ * returned in the given addresses, with each component not including any
+ * separators. Otherwise, %FALSE will be returned and the components will be set
+ * to %NULL.
+ *
+ * @locale is modified, and any returned non-%NULL pointers will point inside
+ * it.
+ *
+ * Returns: %TRUE on success, %FALSE otherwise
+ */
+static gboolean
+parse_locale (gchar *locale  /* (transfer full) */,
+	      const gchar **language_out,
+	      const gchar **territory_out,
+	      const gchar **codeset_out,
+	      const gchar **modifier_out)
+{
+	gchar *separator;
+	const gchar *language = NULL, *territory = NULL, *codeset = NULL, *modifier = NULL;
+
+	separator = strrchr (locale, '@');
+	if (separator != NULL) {
+		modifier = separator + 1;
+		*separator = '\0';
+	}
+
+	separator = strrchr (locale, '.');
+	if (separator != NULL) {
+		codeset = separator + 1;
+		*separator = '\0';
+	}
+
+	separator = strrchr (locale, '_');
+	if (separator != NULL) {
+		territory = separator + 1;
+		*separator = '\0';
+	}
+
+	language = locale;
+
+	/* Parse failure? */
+	if (*language == '\0') {
+		language = NULL;
+		territory = NULL;
+		codeset = NULL;
+		modifier = NULL;
+	}
+
+	if (language_out != NULL)
+		*language_out = language;
+	if (territory_out != NULL)
+		*territory_out = territory;
+	if (codeset_out != NULL)
+		*codeset_out = codeset;
+	if (modifier_out != NULL)
+		*modifier_out = modifier;
+
+	return (language != NULL);
+}
+
+/**
+ * as_content_rating_system_from_locale:
+ * @locale: a locale, in the format described in `man 3 setlocale`
+ *
+ * Determine the most appropriate #AsContentRatingSystem for the given @locale.
+ * Content rating systems are selected by territory. If no content rating system
+ * seems suitable, %AS_CONTENT_RATING_SYSTEM_IARC is returned.
+ *
+ * Returns: the most relevant #AsContentRatingSystem
+ * Since: 0.7.18
+ */
+/* data obtained from https://en.wikipedia.org/wiki/Video_game_rating_system */
+AsContentRatingSystem
+as_content_rating_system_from_locale (const gchar *locale)
+{
+	g_autofree gchar *locale_copy = g_strdup (locale);
+	const gchar *territory;
+
+	/* Default to IARC for locales which can’t be parsed. */
+	if (!parse_locale (locale_copy, NULL, &territory, NULL, NULL))
+		return AS_CONTENT_RATING_SYSTEM_IARC;
+
+	/* Argentina */
+	if (g_strcmp0 (territory, "AR") == 0)
+		return AS_CONTENT_RATING_SYSTEM_INCAA;
+
+	/* Australia */
+	if (g_strcmp0 (territory, "AU") == 0)
+		return AS_CONTENT_RATING_SYSTEM_ACB;
+
+	/* Brazil */
+	if (g_strcmp0 (territory, "BR") == 0)
+		return AS_CONTENT_RATING_SYSTEM_DJCTQ;
+
+	/* Taiwan */
+	if (g_strcmp0 (territory, "TW") == 0)
+		return AS_CONTENT_RATING_SYSTEM_GSRR;
+
+	/* Europe (but not Finland or Germany), India, Israel,
+	 * Pakistan, Quebec, South Africa */
+	if ((g_strcmp0 (territory, "GB") == 0) ||
+	    g_strcmp0 (territory, "AL") == 0 ||
+	    g_strcmp0 (territory, "AD") == 0 ||
+	    g_strcmp0 (territory, "AM") == 0 ||
+	    g_strcmp0 (territory, "AT") == 0 ||
+	    g_strcmp0 (territory, "AZ") == 0 ||
+	    g_strcmp0 (territory, "BY") == 0 ||
+	    g_strcmp0 (territory, "BE") == 0 ||
+	    g_strcmp0 (territory, "BA") == 0 ||
+	    g_strcmp0 (territory, "BG") == 0 ||
+	    g_strcmp0 (territory, "HR") == 0 ||
+	    g_strcmp0 (territory, "CY") == 0 ||
+	    g_strcmp0 (territory, "CZ") == 0 ||
+	    g_strcmp0 (territory, "DK") == 0 ||
+	    g_strcmp0 (territory, "EE") == 0 ||
+	    g_strcmp0 (territory, "FR") == 0 ||
+	    g_strcmp0 (territory, "GE") == 0 ||
+	    g_strcmp0 (territory, "GR") == 0 ||
+	    g_strcmp0 (territory, "HU") == 0 ||
+	    g_strcmp0 (territory, "IS") == 0 ||
+	    g_strcmp0 (territory, "IT") == 0 ||
+	    g_strcmp0 (territory, "LZ") == 0 ||
+	    g_strcmp0 (territory, "XK") == 0 ||
+	    g_strcmp0 (territory, "LV") == 0 ||
+	    g_strcmp0 (territory, "FL") == 0 ||
+	    g_strcmp0 (territory, "LU") == 0 ||
+	    g_strcmp0 (territory, "LT") == 0 ||
+	    g_strcmp0 (territory, "MK") == 0 ||
+	    g_strcmp0 (territory, "MT") == 0 ||
+	    g_strcmp0 (territory, "MD") == 0 ||
+	    g_strcmp0 (territory, "MC") == 0 ||
+	    g_strcmp0 (territory, "ME") == 0 ||
+	    g_strcmp0 (territory, "NL") == 0 ||
+	    g_strcmp0 (territory, "NO") == 0 ||
+	    g_strcmp0 (territory, "PL") == 0 ||
+	    g_strcmp0 (territory, "PT") == 0 ||
+	    g_strcmp0 (territory, "RO") == 0 ||
+	    g_strcmp0 (territory, "SM") == 0 ||
+	    g_strcmp0 (territory, "RS") == 0 ||
+	    g_strcmp0 (territory, "SK") == 0 ||
+	    g_strcmp0 (territory, "SI") == 0 ||
+	    g_strcmp0 (territory, "ES") == 0 ||
+	    g_strcmp0 (territory, "SE") == 0 ||
+	    g_strcmp0 (territory, "CH") == 0 ||
+	    g_strcmp0 (territory, "TR") == 0 ||
+	    g_strcmp0 (territory, "UA") == 0 ||
+	    g_strcmp0 (territory, "VA") == 0 ||
+	    g_strcmp0 (territory, "IN") == 0 ||
+	    g_strcmp0 (territory, "IL") == 0 ||
+	    g_strcmp0 (territory, "PK") == 0 ||
+	    g_strcmp0 (territory, "ZA") == 0)
+		return AS_CONTENT_RATING_SYSTEM_PEGI;
+
+	/* Finland */
+	if (g_strcmp0 (territory, "FI") == 0)
+		return AS_CONTENT_RATING_SYSTEM_KAVI;
+
+	/* Germany */
+	if (g_strcmp0 (territory, "DE") == 0)
+		return AS_CONTENT_RATING_SYSTEM_USK;
+
+	/* Iran */
+	if (g_strcmp0 (territory, "IR") == 0)
+		return AS_CONTENT_RATING_SYSTEM_ESRA;
+
+	/* Japan */
+	if (g_strcmp0 (territory, "JP") == 0)
+		return AS_CONTENT_RATING_SYSTEM_CERO;
+
+	/* New Zealand */
+	if (g_strcmp0 (territory, "NZ") == 0)
+		return AS_CONTENT_RATING_SYSTEM_OFLCNZ;
+
+	/* Russia: Content rating law */
+	if (g_strcmp0 (territory, "RU") == 0)
+		return AS_CONTENT_RATING_SYSTEM_RUSSIA;
+
+	/* Singapore */
+	if (g_strcmp0 (territory, "SQ") == 0)
+		return AS_CONTENT_RATING_SYSTEM_MDA;
+
+	/* South Korea */
+	if (g_strcmp0 (territory, "KR") == 0)
+		return AS_CONTENT_RATING_SYSTEM_GRAC;
+
+	/* USA, Canada, Mexico */
+	if ((g_strcmp0 (territory, "US") == 0) ||
+	    g_strcmp0 (territory, "CA") == 0 ||
+	    g_strcmp0 (territory, "MX") == 0)
+		return AS_CONTENT_RATING_SYSTEM_ESRB;
+
+	/* everything else is IARC */
+	return AS_CONTENT_RATING_SYSTEM_IARC;
+}
+
+/* Table of the human-readable descriptions for each #AsContentRatingValue for
+ * each content rating category. @desc_none must be non-%NULL, but the other
+ * values may be %NULL if no description is appropriate. In that case, the next
+ * non-%NULL description for a lower #AsContentRatingValue will be used. */
+static const struct {
+	const gchar *id;  /* (not nullable) */
+	const gchar *desc_none;  /* (not nullable) */
+	const gchar *desc_mild;  /* (nullable) */
+	const gchar *desc_moderate;  /* (nullable) */
+	const gchar *desc_intense;  /* (nullable) */
+} oars_descriptions[] = {
+	{
+		"violence-cartoon",
+		/* TRANSLATORS: content rating description */
+		N_("No cartoon violence"),
+		/* TRANSLATORS: content rating description */
+		N_("Cartoon characters in unsafe situations"),
+		/* TRANSLATORS: content rating description */
+		N_("Cartoon characters in aggressive conflict"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic violence involving cartoon characters"),
+	},
+	{
+		"violence-fantasy",
+		/* TRANSLATORS: content rating description */
+		N_("No fantasy violence"),
+		/* TRANSLATORS: content rating description */
+		N_("Characters in unsafe situations easily distinguishable from reality"),
+		/* TRANSLATORS: content rating description */
+		N_("Characters in aggressive conflict easily distinguishable from reality"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic violence easily distinguishable from reality"),
+	},
+	{
+		"violence-realistic",
+		/* TRANSLATORS: content rating description */
+		N_("No realistic violence"),
+		/* TRANSLATORS: content rating description */
+		N_("Mildly realistic characters in unsafe situations"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of realistic characters in aggressive conflict"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic violence involving realistic characters"),
+	},
+	{
+		"violence-bloodshed",
+		/* TRANSLATORS: content rating description */
+		N_("No bloodshed"),
+		/* TRANSLATORS: content rating description */
+		N_("Unrealistic bloodshed"),
+		/* TRANSLATORS: content rating description */
+		N_("Realistic bloodshed"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of bloodshed and the mutilation of body parts"),
+	},
+	{
+		"violence-sexual",
+		/* TRANSLATORS: content rating description */
+		N_("No sexual violence"),
+		/* TRANSLATORS: content rating description */
+		N_("Rape or other violent sexual behavior"),
+		NULL,
+		NULL,
+	},
+	{
+		"drugs-alcohol",
+		/* TRANSLATORS: content rating description */
+		N_("No references to alcohol"),
+		/* TRANSLATORS: content rating description */
+		N_("References to alcoholic beverages"),
+		/* TRANSLATORS: content rating description */
+		N_("Use of alcoholic beverages"),
+		NULL,
+	},
+	{
+		"drugs-narcotics",
+		/* TRANSLATORS: content rating description */
+		N_("No references to illicit drugs"),
+		/* TRANSLATORS: content rating description */
+		N_("References to illicit drugs"),
+		/* TRANSLATORS: content rating description */
+		N_("Use of illicit drugs"),
+		NULL,
+	},
+	{
+		"drugs-tobacco",
+		/* TRANSLATORS: content rating description */
+		N_("No references to tobacco products"),
+		/* TRANSLATORS: content rating description */
+		N_("References to tobacco products"),
+		/* TRANSLATORS: content rating description */
+		N_("Use of tobacco products"),
+		NULL,
+	},
+	{
+		"sex-nudity",
+		/* TRANSLATORS: content rating description */
+		N_("No nudity of any sort"),
+		/* TRANSLATORS: content rating description */
+		N_("Brief artistic nudity"),
+		/* TRANSLATORS: content rating description */
+		N_("Prolonged nudity"),
+		NULL,
+	},
+	{
+		"sex-themes",
+		/* TRANSLATORS: content rating description */
+		N_("No references to or depictions of sexual nature"),
+		/* TRANSLATORS: content rating description */
+		N_("Provocative references or depictions"),
+		/* TRANSLATORS: content rating description */
+		N_("Sexual references or depictions"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic sexual behavior"),
+	},
+	{
+		"language-profanity",
+		/* TRANSLATORS: content rating description */
+		N_("No profanity of any kind"),
+		/* TRANSLATORS: content rating description */
+		N_("Mild or infrequent use of profanity"),
+		/* TRANSLATORS: content rating description */
+		N_("Moderate use of profanity"),
+		/* TRANSLATORS: content rating description */
+		N_("Strong or frequent use of profanity"),
+	},
+	{
+		"language-humor",
+		/* TRANSLATORS: content rating description */
+		N_("No inappropriate humor"),
+		/* TRANSLATORS: content rating description */
+		N_("Slapstick humor"),
+		/* TRANSLATORS: content rating description */
+		N_("Vulgar or bathroom humor"),
+		/* TRANSLATORS: content rating description */
+		N_("Mature or sexual humor"),
+	},
+	{
+		"language-discrimination",
+		/* TRANSLATORS: content rating description */
+		N_("No discriminatory language of any kind"),
+		/* TRANSLATORS: content rating description */
+		N_("Negativity towards a specific group of people"),
+		/* TRANSLATORS: content rating description */
+		N_("Discrimination designed to cause emotional harm"),
+		/* TRANSLATORS: content rating description */
+		N_("Explicit discrimination based on gender, sexuality, race or religion"),
+	},
+	{
+		"money-advertising",
+		/* TRANSLATORS: content rating description */
+		N_("No advertising of any kind"),
+		/* TRANSLATORS: content rating description */
+		N_("Product placement"),
+		/* TRANSLATORS: content rating description */
+		N_("Explicit references to specific brands or trademarked products"),
+		/* TRANSLATORS: content rating description */
+		N_("Users are encouraged to purchase specific real-world items"),
+	},
+	{
+		"money-gambling",
+		/* TRANSLATORS: content rating description */
+		N_("No gambling of any kind"),
+		/* TRANSLATORS: content rating description */
+		N_("Gambling on random events using tokens or credits"),
+		/* TRANSLATORS: content rating description */
+		N_("Gambling using “play” money"),
+		/* TRANSLATORS: content rating description */
+		N_("Gambling using real money"),
+	},
+	{
+		"money-purchasing",
+		/* TRANSLATORS: content rating description */
+		N_("No ability to spend money"),
+		/* TRANSLATORS: content rating description */
+		N_("Users are encouraged to donate real money"),
+		NULL,
+		/* TRANSLATORS: content rating description */
+		N_("Ability to spend real money in-app"),
+	},
+	{
+		"social-chat",
+		/* TRANSLATORS: content rating description */
+		N_("No way to chat with other users"),
+		/* TRANSLATORS: content rating description */
+		N_("User-to-user interactions without chat functionality"),
+		/* TRANSLATORS: content rating description */
+		N_("Moderated chat functionality between users"),
+		/* TRANSLATORS: content rating description */
+		N_("Uncontrolled chat functionality between users"),
+	},
+	{
+		"social-audio",
+		/* TRANSLATORS: content rating description */
+		N_("No way to talk with other users"),
+		/* TRANSLATORS: content rating description */
+		N_("Uncontrolled audio or video chat functionality between users"),
+		NULL,
+		NULL,
+	},
+	{
+		"social-contacts",
+		/* TRANSLATORS: content rating description */
+		N_("No sharing of social network usernames or email addresses"),
+		/* TRANSLATORS: content rating description */
+		N_("Sharing social network usernames or email addresses"),
+		NULL,
+		NULL,
+	},
+	{
+		"social-info",
+		/* TRANSLATORS: content rating description */
+		N_("No sharing of user information with third parties"),
+		/* TRANSLATORS: content rating description */
+		N_("Checking for the latest application version"),
+		/* TRANSLATORS: content rating description */
+		N_("Sharing diagnostic data that does not let others identify the user"),
+		/* TRANSLATORS: content rating description */
+		N_("Sharing information that lets others identify the user"),
+	},
+	{
+		"social-location",
+		/* TRANSLATORS: content rating description */
+		N_("No sharing of physical location with other users"),
+		/* TRANSLATORS: content rating description */
+		N_("Sharing physical location with other users"),
+		NULL,
+		NULL,
+	},
+
+	/* v1.1 */
+	{
+		"sex-homosexuality",
+		/* TRANSLATORS: content rating description */
+		N_("No references to homosexuality"),
+		/* TRANSLATORS: content rating description */
+		N_("Indirect references to homosexuality"),
+		/* TRANSLATORS: content rating description */
+		N_("Kissing between people of the same gender"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic sexual behavior between people of the same gender"),
+	},
+	{
+		"sex-prostitution",
+		/* TRANSLATORS: content rating description */
+		N_("No references to prostitution"),
+		/* TRANSLATORS: content rating description */
+		N_("Indirect references to prostitution"),
+		/* TRANSLATORS: content rating description */
+		N_("Direct references to prostitution"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic depictions of the act of prostitution"),
+	},
+	{
+		"sex-adultery",
+		/* TRANSLATORS: content rating description */
+		N_("No references to adultery"),
+		/* TRANSLATORS: content rating description */
+		N_("Indirect references to adultery"),
+		/* TRANSLATORS: content rating description */
+		N_("Direct references to adultery"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic depictions of the act of adultery"),
+	},
+	{
+		"sex-appearance",
+		/* TRANSLATORS: content rating description */
+		N_("No sexualized characters"),
+		NULL,
+		/* TRANSLATORS: content rating description */
+		N_("Scantily clad human characters"),
+		/* TRANSLATORS: content rating description */
+		N_("Overtly sexualized human characters"),
+	},
+	{
+		"violence-worship",
+		/* TRANSLATORS: content rating description */
+		N_("No references to desecration"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of or references to historical desecration"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of modern-day human desecration"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic depictions of modern-day desecration"),
+	},
+	{
+		"violence-desecration",
+		/* TRANSLATORS: content rating description */
+		N_("No visible dead human remains"),
+		/* TRANSLATORS: content rating description */
+		N_("Visible dead human remains"),
+		/* TRANSLATORS: content rating description */
+		N_("Dead human remains that are exposed to the elements"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic depictions of desecration of human bodies"),
+	},
+	{
+		"violence-slavery",
+		/* TRANSLATORS: content rating description */
+		N_("No references to slavery"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of or references to historical slavery"),
+		/* TRANSLATORS: content rating description */
+		N_("Depictions of modern-day slavery"),
+		/* TRANSLATORS: content rating description */
+		N_("Graphic depictions of modern-day slavery"),
+	},
+};
+
+/**
+ * as_content_rating_attribute_get_description:
+ * @id: the subsection ID e.g. `violence-cartoon`
+ * @value: the #AsContentRatingValue, e.g. %AS_CONTENT_RATING_VALUE_INTENSE
+ *
+ * Get a human-readable description of what content would be expected to
+ * require the content rating attribute given by @id and @value.
+ *
+ * Returns: a human-readable description of @id and @value
+ * Since: 0.7.18
+ */
+const gchar *
+as_content_rating_attribute_get_description (const gchar *id, AsContentRatingValue value)
+{
+	gsize i;
+
+	if ((gint) value < AS_CONTENT_RATING_VALUE_NONE ||
+	    (gint) value > AS_CONTENT_RATING_VALUE_INTENSE)
+		return NULL;
+
+	for (i = 0; i < G_N_ELEMENTS (oars_descriptions); i++) {
+		if (!g_str_equal (oars_descriptions[i].id, id))
+			continue;
+
+		/* Return the most-intense non-NULL string. */
+		if (oars_descriptions[i].desc_intense != NULL && value >= AS_CONTENT_RATING_VALUE_INTENSE)
+			return _(oars_descriptions[i].desc_intense);
+		if (oars_descriptions[i].desc_moderate != NULL && value >= AS_CONTENT_RATING_VALUE_MODERATE)
+			return _(oars_descriptions[i].desc_moderate);
+		if (oars_descriptions[i].desc_mild != NULL && value >= AS_CONTENT_RATING_VALUE_MILD)
+			return _(oars_descriptions[i].desc_mild);
+		if (oars_descriptions[i].desc_none != NULL && value >= AS_CONTENT_RATING_VALUE_NONE)
+			return _(oars_descriptions[i].desc_none);
+		g_assert_not_reached ();
+	}
+
+	/* This means the requested @id is missing from @oars_descriptions, so
+	 * presumably the OARS spec has been updated but appstream-glib hasn’t. */
+	g_warn_if_reached ();
+
+	return NULL;
+}
+
 /* The struct definition below assumes we don’t grow more
  * #AsContentRating values. */
 G_STATIC_ASSERT (AS_CONTENT_RATING_VALUE_LAST == AS_CONTENT_RATING_VALUE_INTENSE + 1);
@@ -309,6 +1210,48 @@ as_content_rating_attribute_to_csm_age (const gchar *id, AsContentRatingValue va
 }
 
 /**
+ * as_content_rating_attribute_from_csm_age:
+ * @id: the subsection ID e.g. `violence-cartoon`
+ * @age: the CSM age
+ *
+ * Gets the highest #AsContentRatingValue which is allowed to be seen by the
+ * given Common Sense Media @age for the given subsection @id.
+ *
+ * For example, if the CSM age mappings for `violence-bloodshed` are:
+ *  * age ≥ 0 for %AS_CONTENT_RATING_VALUE_NONE
+ *  * age ≥ 9 for %AS_CONTENT_RATING_VALUE_MILD
+ *  * age ≥ 11 for %AS_CONTENT_RATING_VALUE_MODERATE
+ *  * age ≥ 18 for %AS_CONTENT_RATING_VALUE_INTENSE
+ * then calling this function with `violence-bloodshed` and @age set to 17 would
+ * return %AS_CONTENT_RATING_VALUE_MODERATE. Calling it with age 18 would
+ * return %AS_CONTENT_RATING_VALUE_INTENSE.
+ *
+ * Returns: the #AsContentRatingValue, or %AS_CONTENT_RATING_VALUE_UNKNOWN if
+ *    unknown
+ * Since: 0.7.18
+ */
+AsContentRatingValue
+as_content_rating_attribute_from_csm_age (const gchar *id, guint age)
+{
+	for (gsize i = 0; G_N_ELEMENTS (oars_to_csm_mappings); i++) {
+		if (g_strcmp0 (id, oars_to_csm_mappings[i].id) == 0) {
+			if (age >= oars_to_csm_mappings[i].csm_age_intense)
+				return AS_CONTENT_RATING_VALUE_INTENSE;
+			else if (age >= oars_to_csm_mappings[i].csm_age_moderate)
+				return AS_CONTENT_RATING_VALUE_MODERATE;
+			else if (age >= oars_to_csm_mappings[i].csm_age_mild)
+				return AS_CONTENT_RATING_VALUE_MILD;
+			else if (age >= oars_to_csm_mappings[i].csm_age_none)
+				return AS_CONTENT_RATING_VALUE_NONE;
+			else
+				return AS_CONTENT_RATING_VALUE_UNKNOWN;
+		}
+	}
+
+	return AS_CONTENT_RATING_VALUE_UNKNOWN;
+}
+
+/**
  * as_content_rating_get_all_rating_ids:
  *
  * Returns a list of all the valid OARS content rating attribute IDs as could
diff --git a/libappstream-glib/as-content-rating.h b/libappstream-glib/as-content-rating.h
index 42decd3..4d8b5b2 100644
--- a/libappstream-glib/as-content-rating.h
+++ b/libappstream-glib/as-content-rating.h
@@ -52,12 +52,66 @@ typedef enum {
 	AS_CONTENT_RATING_VALUE_LAST
 } AsContentRatingValue;
 
+/**
+ * AsContentRatingSystem:
+ * @AS_CONTENT_RATING_SYSTEM_UNKNOWN: Unknown ratings system
+ * @AS_CONTENT_RATING_SYSTEM_INCAA: INCAA
+ * @AS_CONTENT_RATING_SYSTEM_ACB: ACB
+ * @AS_CONTENT_RATING_SYSTEM_DJCTQ: DJCTQ
+ * @AS_CONTENT_RATING_SYSTEM_GSRR: GSRR
+ * @AS_CONTENT_RATING_SYSTEM_PEGI: PEGI
+ * @AS_CONTENT_RATING_SYSTEM_KAVI: KAVI
+ * @AS_CONTENT_RATING_SYSTEM_USK: USK
+ * @AS_CONTENT_RATING_SYSTEM_ESRA: ESRA
+ * @AS_CONTENT_RATING_SYSTEM_CERO: CERO
+ * @AS_CONTENT_RATING_SYSTEM_OFLCNZ: OFLCNZ
+ * @AS_CONTENT_RATING_SYSTEM_RUSSIA: Russia
+ * @AS_CONTENT_RATING_SYSTEM_MDA: MDA
+ * @AS_CONTENT_RATING_SYSTEM_GRAC: GRAC
+ * @AS_CONTENT_RATING_SYSTEM_ESRB: ESRB
+ * @AS_CONTENT_RATING_SYSTEM_IARC: IARC
+ *
+ * A content rating system for a particular territory.
+ *
+ * Since: 0.7.18
+ */
+typedef enum {
+	AS_CONTENT_RATING_SYSTEM_UNKNOWN,
+	AS_CONTENT_RATING_SYSTEM_INCAA,
+	AS_CONTENT_RATING_SYSTEM_ACB,
+	AS_CONTENT_RATING_SYSTEM_DJCTQ,
+	AS_CONTENT_RATING_SYSTEM_GSRR,
+	AS_CONTENT_RATING_SYSTEM_PEGI,
+	AS_CONTENT_RATING_SYSTEM_KAVI,
+	AS_CONTENT_RATING_SYSTEM_USK,
+	AS_CONTENT_RATING_SYSTEM_ESRA,
+	AS_CONTENT_RATING_SYSTEM_CERO,
+	AS_CONTENT_RATING_SYSTEM_OFLCNZ,
+	AS_CONTENT_RATING_SYSTEM_RUSSIA,
+	AS_CONTENT_RATING_SYSTEM_MDA,
+	AS_CONTENT_RATING_SYSTEM_GRAC,
+	AS_CONTENT_RATING_SYSTEM_ESRB,
+	AS_CONTENT_RATING_SYSTEM_IARC,
+	/*< private >*/
+	AS_CONTENT_RATING_SYSTEM_LAST
+} AsContentRatingSystem;
+
 AsContentRating	*as_content_rating_new		(void);
 
 /* helpers */
 const gchar	*as_content_rating_value_to_string	(AsContentRatingValue	 value);
 AsContentRatingValue	 as_content_rating_value_from_string	(const gchar	*value);
 
+const gchar	*as_content_rating_system_to_string	(AsContentRatingSystem	 system);
+gchar		*as_content_rating_system_format_age	(AsContentRatingSystem	 system,
+							 guint			 age);
+
+AsContentRatingSystem	 as_content_rating_system_from_locale	(const gchar	*locale);
+
+gchar		**as_content_rating_system_get_formatted_ages	(AsContentRatingSystem	 system);
+const guint	 *as_content_rating_system_get_csm_ages		(AsContentRatingSystem	 system,
+								 gsize			*length_out);
+
 /* getters */
 const gchar	*as_content_rating_get_kind	(AsContentRating	*content_rating);
 guint		 as_content_rating_get_minimum_age (AsContentRating	*content_rating);
@@ -71,6 +125,10 @@ const gchar	**as_content_rating_get_rating_ids (AsContentRating	*content_rating)
 
 guint		as_content_rating_attribute_to_csm_age (const gchar		*id,
 							AsContentRatingValue 	 value);
+AsContentRatingValue	as_content_rating_attribute_from_csm_age	(const gchar	*id,
+									 guint		 age);
+const gchar	*as_content_rating_attribute_get_description (const gchar	*id,
+							      AsContentRatingValue	value);
 const gchar	**as_content_rating_get_all_rating_ids (void);
 
 /* setters */
diff --git a/libappstream-glib/as-self-test.c b/libappstream-glib/as-self-test.c
index 6616641..d7c726e 100644
--- a/libappstream-glib/as-self-test.c
+++ b/libappstream-glib/as-self-test.c
@@ -1884,6 +1884,57 @@ as_test_content_rating_mappings (void)
 	g_assert_cmpuint (as_content_rating_attribute_to_csm_age ("not-valid-id", AS_CONTENT_RATING_VALUE_INTENSE), ==, 0);
 }
 
+/* Test that gs_utils_content_rating_system_from_locale() returns the correct
+ * rating system for various standard locales and various forms of locale name.
+ * See `locale -a` for the list of all available locales which some of these
+ * test vectors were derived from. */
+static void
+as_test_content_rating_from_locale (void)
+{
+	const struct {
+		const gchar *locale;
+		AsContentRatingSystem expected_system;
+	} vectors[] = {
+		/* Simple tests to get coverage of each rating system: */
+		{ "es_AR", AS_CONTENT_RATING_SYSTEM_INCAA },
+		{ "en_AU", AS_CONTENT_RATING_SYSTEM_ACB },
+		{ "pt_BR", AS_CONTENT_RATING_SYSTEM_DJCTQ },
+		{ "zh_TW", AS_CONTENT_RATING_SYSTEM_GSRR },
+		{ "en_GB", AS_CONTENT_RATING_SYSTEM_PEGI },
+		{ "hy_AM", AS_CONTENT_RATING_SYSTEM_PEGI },
+		{ "bg_BG", AS_CONTENT_RATING_SYSTEM_PEGI },
+		{ "fi_FI", AS_CONTENT_RATING_SYSTEM_KAVI },
+		{ "de_DE", AS_CONTENT_RATING_SYSTEM_USK },
+		{ "az_IR", AS_CONTENT_RATING_SYSTEM_ESRA },
+		{ "jp_JP", AS_CONTENT_RATING_SYSTEM_CERO },
+		{ "en_NZ", AS_CONTENT_RATING_SYSTEM_OFLCNZ },
+		{ "ru_RU", AS_CONTENT_RATING_SYSTEM_RUSSIA },
+		{ "en_SQ", AS_CONTENT_RATING_SYSTEM_MDA },
+		{ "ko_KR", AS_CONTENT_RATING_SYSTEM_GRAC },
+		{ "en_US", AS_CONTENT_RATING_SYSTEM_ESRB },
+		{ "en_US", AS_CONTENT_RATING_SYSTEM_ESRB },
+		{ "en_CA", AS_CONTENT_RATING_SYSTEM_ESRB },
+		{ "es_MX", AS_CONTENT_RATING_SYSTEM_ESRB },
+		/* Fallback (arbitrarily chosen Venezuela since it seems to use IARC): */
+		{ "es_VE", AS_CONTENT_RATING_SYSTEM_IARC },
+		/* Locale with a codeset: */
+		{ "nl_NL.iso88591", AS_CONTENT_RATING_SYSTEM_PEGI },
+		/* Locale with a codeset and modifier: */
+		{ "nl_NL.iso885915@euro", AS_CONTENT_RATING_SYSTEM_PEGI },
+		/* Locale with a less esoteric codeset: */
+		{ "en_GB.UTF-8", AS_CONTENT_RATING_SYSTEM_PEGI },
+		/* Locale with a modifier but no codeset: */
+		{ "fi_FI@euro", AS_CONTENT_RATING_SYSTEM_KAVI },
+		/* Invalid locale: */
+		{ "_invalid", AS_CONTENT_RATING_SYSTEM_IARC },
+	};
+
+	for (gsize i = 0; i < G_N_ELEMENTS (vectors); i++) {
+		g_test_message ("Test %" G_GSIZE_FORMAT ": %s", i, vectors[i].locale);
+		g_assert_cmpint (as_content_rating_system_from_locale (vectors[i].locale), ==, vectors[i].expected_system);
+	}
+}
+
 static void
 as_test_app_func (void)
 {
@@ -5717,6 +5768,7 @@ main (int argc, char **argv)
 	g_test_add_func ("/AppStream/content_rating", as_test_content_rating_func);
 	g_test_add_func ("/AppStream/content_rating/empty", as_test_content_rating_empty);
 	g_test_add_func ("/AppStream/content_rating/mappings", as_test_content_rating_mappings);
+	g_test_add_func ("/AppStream/content_rating/from-locale", as_test_content_rating_from_locale);
 	g_test_add_func ("/AppStream/release", as_test_release_func);
 	g_test_add_func ("/AppStream/release{date}", as_test_release_date_func);
 	g_test_add_func ("/AppStream/release{appdata}", as_test_release_appdata_func);
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 905d786..a683ff7 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -1,3 +1,4 @@
 client/as-builder.c
 client/as-compose.c
 client/as-util.c
+libappstream-glib/as-content-rating.c