Do something special on Tuesday

Optional feature, can be enabled for a certain channel with a config flag.
![Happy Tuesday](https://tenor.com/view/happy-tuesday-its-tuesday-tuesday-dance-default-mario-gif-15064439)

config.c

@@ -1,5 +1,9 @@
 #define _GNU_SOURCE
+#include <assert.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
 
 #include <concord/discord.h>
 
@@ -7,11 +11,32 @@
 
 struct zblock_config zblock_config;
 
-int zblock_config_load(struct discord *client) {
+static const char *ZBLOCK_CONFIG_ERRORS[] = {
+	"OK",
+	"Error loading conninfo from config",
+	"No channel id was provided for the tuesday event"
+};
+static_assert(sizeof(ZBLOCK_CONFIG_ERRORS) / sizeof(*ZBLOCK_CONFIG_ERRORS) == ZBLOCK_CONFIG_ERRORCOUNT, "Not all config errors implemented");
+
+zblock_config_err zblock_config_load(struct discord *client) {
 	struct ccord_szbuf_readonly conninfo = discord_config_get_field(client, (char *[2]){"zblock", "conninfo"}, 2);
 	if (asprintf(&zblock_config.conninfo, "%.*s", (int)conninfo.size, conninfo.start) < 0) {
-		return 1;
+		return ZBLOCK_CONFIG_CONNINFO_ERROR;
+	}
+
+	struct ccord_szbuf_readonly tuesday_enable = discord_config_get_field(client, (char *[3]){"zblock", "tuesday", "enable"}, 3);
+	if (!strncmp(tuesday_enable.start, "true", tuesday_enable.size)) {
+		zblock_config.tuesday_enable = true;
+		struct ccord_szbuf_readonly tuesday_channel = discord_config_get_field(client, (char *[3]){"zblock", "tuesday", "channel"}, 3);
+		zblock_config.tuesday_channel = 0; // initialize it with something
+		if (tuesday_channel.size > 0) zblock_config.tuesday_channel = strtoull(tuesday_channel.start, NULL, 10);
+		if (!zblock_config.tuesday_channel) return ZBLOCK_CONFIG_NO_TUESDAY_CHANNEL;
 	}
 	
-	return 0;
+	return ZBLOCK_CONFIG_OK;
+}
+
+// returns a string about the result of a config function
+const char *zblock_config_strerror(zblock_config_err error) {
+	return error < 0 || error >= ZBLOCK_CONFIG_ERRORCOUNT ? "Unspecified error" : ZBLOCK_CONFIG_ERRORS[error];
 }

config.h

@@ -6,8 +6,21 @@
 // the current zblock config
 extern struct zblock_config {
 	char *conninfo;
+	u64snowflake tuesday_channel;
+	bool tuesday_enable;
 } zblock_config;
 
-int zblock_config_load(struct discord *client);
+typedef enum {
+	ZBLOCK_CONFIG_OK,
+	ZBLOCK_CONFIG_CONNINFO_ERROR,
+	ZBLOCK_CONFIG_NO_TUESDAY_CHANNEL,
+	ZBLOCK_CONFIG_ERRORCOUNT
+} zblock_config_err;
+
+// load config entries for zblock
+zblock_config_err zblock_config_load(struct discord *client);
+
+// returns a string about the result of a config function
+const char *zblock_config_strerror(zblock_config_err error);
 
 #endif

main.c

@@ -218,6 +218,17 @@ static void timer_retrieve_feeds(struct discord *client, struct discord_timer *t
 	pthread_create(&retrieve_thread, NULL, &thread_retrieve_feeds, client);
 }
 
+static void timer_tuesday_event(struct discord *client, struct discord_timer *timer) {
+	// not doing anything with the timer
+	(void) timer;
+
+	struct discord_create_message msg = {
+		.content = "https://tenor.com/view/happy-tuesday-its-tuesday-tuesday-dance-default-mario-gif-15064439"
+	};
+
+	discord_create_message(client, zblock_config.tuesday_channel, &msg, NULL);
+}
+
 static void bot_command_add(struct discord *client, const struct discord_interaction *event) {
 	char msg[DISCORD_MAX_MESSAGE_LEN];
 	zblock_feed_info feed;
@@ -505,6 +516,18 @@ static struct bot_command commands[] = {
 	}
 };
 
+// delay before the first feed retrieval (in ms)
+#define FEED_TIMER_DELAY 15000
+
+// interval for the feed retrieval timer (in ms)
+#define FEED_TIMER_INTERVAL 600000
+
+// seconds in a day
+#define ONE_DAY_SEC 86400
+
+// milliseconds in a week
+#define ONE_WEEK_MS 604800000
+
 static void on_ready(struct discord *client, const struct discord_ready *event) {
 	log_info("Logged in as %s!", event->user->username);
 
@@ -512,6 +535,25 @@ static void on_ready(struct discord *client, const struct discord_ready *event)
 	for (struct bot_command *i = commands; i < commands + sizeof(commands) / sizeof(*commands); ++i) {
 		discord_create_global_application_command(client, event->application->id, &i->cmd, NULL);
 	}
+
+	// feed timer
+	discord_timer_interval(client, timer_retrieve_feeds, NULL, NULL, FEED_TIMER_DELAY, FEED_TIMER_INTERVAL, -1);
+
+	// find the next tueday and start the timer for the tuesday event
+	if (zblock_config.tuesday_enable) {
+		time_t current_time = time(NULL);
+		struct tm midnight_tm;
+		gmtime_r(&current_time, &midnight_tm);
+		// set it to midnight
+		midnight_tm.tm_sec = 0;
+		midnight_tm.tm_min = 0;
+		midnight_tm.tm_hour = 0;
+		time_t midnight_time = timegm(&midnight_tm);
+		// find next tuesday and add it to the time
+		time_t next_tuesday = midnight_time + ONE_DAY_SEC * (((1 - midnight_tm.tm_wday + 7) % 7) + 1);
+		// set a timer that starts midnight next tuesday and triggers every week
+		discord_timer_interval(client, timer_tuesday_event, NULL, NULL, (next_tuesday - current_time) * 1000, ONE_WEEK_MS, -1);
+	}
 }
 
 static void on_interaction(struct discord *client, const struct discord_interaction *event) {
@@ -549,12 +591,6 @@ static void on_guild_delete(struct discord *client, const struct discord_guild *
 	}
 }
 
-// delay before the first feed retrieval (in ms)
-#define FEED_TIMER_DELAY 15000
-
-// interval for the feed retrieval timer (in ms)
-#define FEED_TIMER_INTERVAL 600000
-
 int main(void) {
 	int exit_code = 0;	
 	
@@ -562,7 +598,13 @@ int main(void) {
 	setlocale(LC_ALL, "C");
 	srand(time(NULL));
 	struct discord *client = discord_config_init("config.json");
-	zblock_config_load(client);
+
+	zblock_config_err config_err = zblock_config_load(client);
+	if (config_err) {
+		log_fatal("Error loading zblock config: %s\n", zblock_config_strerror(config_err));
+		exit_code = 1;
+		goto cleanup;
+	}
 	
 	// connect to database
 	database_conn = PQconnectdb(zblock_config.conninfo);
@@ -575,7 +617,6 @@ int main(void) {
 	discord_set_on_ready(client, &on_ready);
 	discord_set_on_interaction_create(client, &on_interaction);
 	discord_set_on_guild_delete(client, &on_guild_delete);
-	discord_timer_interval(client, timer_retrieve_feeds, NULL, NULL, FEED_TIMER_DELAY, FEED_TIMER_INTERVAL, -1);
 	discord_run(client);
 	
 	PQfinish(database_conn);