From a1d62dd085ac70fc90a05095220156897bdd8f82 Mon Sep 17 00:00:00 2001
From: Tommaso Negri <me@tommasongr.com>
Date: Tue, 11 Aug 2026 17:50:39 +0200
Subject: refactor daemons + mpd + documentation

---
 daemons/mpd.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 daemons/mpd.c

(limited to 'daemons/mpd.c')

diff --git a/daemons/mpd.c b/daemons/mpd.c
new file mode 100644
index 0000000..f8dbb64
--- /dev/null
+++ b/daemons/mpd.c
@@ -0,0 +1,156 @@
+// mpd — MPD (Music Player Daemon) daemon for bar
+//
+// Connects to MPD via TCP and uses the `idle` command to block until
+// the player state or playlist changes. When it does, posts a Darwin
+// notification. No polling, no special permissions — just a TCP socket.
+//
+// MPD_HOST and MPD_PORT environment variables are respected (same as
+// mpc's convention). Defaults: localhost:6600.
+//
+// Compile:
+//   cc -o bar-mpd daemons/mpd.c
+
+#include <notify.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <netdb.h>
+#include <sys/socket.h>
+#include <errno.h>
+
+static volatile int keep_running = 1;
+
+static void handle_signal(int sig) {
+	(void)sig;
+	keep_running = 0;
+}
+
+// ── MPD helpers ──────────────────────────────────────────────────────
+
+/// Read a line from the MPD socket (up to newline). Returns the number
+/// of bytes read, or -1 on error. The line is null-terminated.
+static int read_line(int fd, char *buf, size_t size) {
+	size_t i = 0;
+	while (i < size - 1) {
+		ssize_t n = read(fd, &buf[i], 1);
+		if (n <= 0) return -1;
+		if (buf[i] == '\n') break;
+		i++;
+	}
+	buf[i] = '\0';
+	return (int)i;
+}
+
+/// Connect to MPD. Returns a socket fd, or -1 on failure.
+static int connect_mpd(const char *host, int port) {
+	struct addrinfo hints = {0}, *ai = NULL;
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+
+	char port_str[16];
+	snprintf(port_str, sizeof(port_str), "%d", port);
+
+	int err = getaddrinfo(host, port_str, &hints, &ai);
+	if (err) return -1;
+
+	int fd = -1;
+	for (struct addrinfo *rp = ai; rp; rp = rp->ai_next) {
+		fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+		if (fd < 0) continue;
+		if (connect(fd, rp->ai_addr, rp->ai_addrlen) == 0) break;
+		close(fd);
+		fd = -1;
+	}
+	freeaddrinfo(ai);
+
+	if (fd < 0) return -1;
+
+	// Read the MPD greeting line (e.g. "OK MPD 0.23.0")
+	char buf[256];
+	if (read_line(fd, buf, sizeof(buf)) < 0) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+/// Send a command to MPD and read the response. Returns 0 on success.
+static int mpd_command(int fd, const char *cmd) {
+	char buf[1024];
+	snprintf(buf, sizeof(buf), "%s\n", cmd);
+	ssize_t len = strlen(buf);
+
+	if (write(fd, buf, len) != len) return -1;
+
+	// Read until we see "OK" or "ACK"
+	while (1) {
+		int n = read_line(fd, buf, sizeof(buf));
+		if (n < 0) return -1;
+		if (strcmp(buf, "OK") == 0) return 0;
+		if (strncmp(buf, "ACK", 3) == 0) return -1;
+		// ignore other response lines (e.g. "changed: player")
+	}
+}
+
+// ── Main ─────────────────────────────────────────────────────────────
+
+int main(void) {
+	// Use sigaction so that read() is NOT restarted after a signal
+	// (macOS's signal() enables SA_RESTART by default, which would
+	//  cause the program to ignore Ctrl+C while blocked on read).
+	struct sigaction sa = {0};
+	sa.sa_handler = handle_signal;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = 0;  // no SA_RESTART → read() returns EINTR
+	sigaction(SIGINT, &sa, NULL);
+	sigaction(SIGTERM, &sa, NULL);
+
+	// Read MPD host/port from environment (same convention as mpc)
+	const char *mpd_host = getenv("MPD_HOST");
+	if (!mpd_host || !*mpd_host) mpd_host = "localhost";
+
+	int mpd_port = 6600;
+	const char *port_env = getenv("MPD_PORT");
+	if (port_env && *port_env) mpd_port = atoi(port_env);
+
+	while (keep_running) {
+		int fd = connect_mpd(mpd_host, mpd_port);
+		if (fd < 0) {
+			// MPD not running yet — wait and retry
+			for (int i = 0; i < 10 && keep_running; i++) sleep(1);
+			continue;
+		}
+
+		// Enter idle mode — blocks until something changes
+		while (keep_running) {
+			const char *idle_cmd = "idle player playlist options\n";
+			ssize_t len = strlen(idle_cmd);
+
+			if (write(fd, idle_cmd, len) != len) break;
+
+			// Read response — will block until MPD sends something
+			char buf[256];
+			int n = read_line(fd, buf, sizeof(buf));
+			if (n < 0) break;
+
+			// Drain the rest of the response
+			while (1) {
+				n = read_line(fd, buf, sizeof(buf));
+				if (n < 0) break;
+				if (strcmp(buf, "OK") == 0) break;
+			}
+
+			notify_post("bar.touch.<block-name>");
+		}
+
+		close(fd);
+
+		// Brief pause before reconnecting
+		if (keep_running) sleep(1);
+	}
+
+	return 0;
+}
-- 
cgit v1.2.3