package main

import (
	"errors"
	"net"
	"os"
	"path/filepath"
	"syscall"
	"testing"
	"time"
)

// TestNotifyReadyWritesToTheSocket: the whole contract. systemd hands the
// process a unixgram socket path in NOTIFY_SOCKET and waits for READY=1
// before calling the unit started — which is what turns "exec'd" into
// "actually serving" for the adopt pass's restart check.
//
// Uses os.MkdirTemp directly (NOT t.TempDir): t.TempDir embeds the test
// name in the path it hands back, and AF_UNIX socket paths are capped at
// sizeof(sockaddr_un.sun_path) — 108 bytes on Linux. A long test name under
// a long TMPDIR pushes that over the limit and net.ListenPacket fails with
// "invalid argument", which is a test-harness artifact, not evidence
// unixgram sockets are unsupported here — so only the genuinely-unsupported
// errors (EAFNOSUPPORT, EPERM) are allowed to skip the test; anything else,
// including a too-long path, must fail loudly.
func TestNotifyReadyWritesToTheSocket(t *testing.T) {
	dir, err := os.MkdirTemp("", "n")
	if err != nil {
		t.Fatalf("MkdirTemp: %v", err)
	}
	t.Cleanup(func() { os.RemoveAll(dir) })
	sock := filepath.Join(dir, "n.sock")
	conn, err := net.ListenPacket("unixgram", sock)
	if err != nil {
		if errors.Is(err, syscall.EAFNOSUPPORT) || errors.Is(err, syscall.EPERM) {
			t.Skipf("unixgram unavailable here: %v", err)
		}
		t.Fatalf("ListenPacket(unixgram, %s): %v", sock, err)
	}
	defer conn.Close()
	t.Setenv("NOTIFY_SOCKET", sock)

	if err := NotifyReady(); err != nil {
		t.Fatalf("NotifyReady: %v", err)
	}
	buf := make([]byte, 64)
	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	n, _, err := conn.ReadFrom(buf)
	if err != nil {
		t.Fatalf("nothing arrived on the notify socket: %v", err)
	}
	if got := string(buf[:n]); got != "READY=1" {
		t.Fatalf("sent %q, want READY=1", got)
	}
}

// TestNotifyReadyIsANoOpOutsideSystemd: the console runs under `go run`, in
// tests and on a laptop, and none of those set NOTIFY_SOCKET. Absent is
// normal, not an error.
func TestNotifyReadyIsANoOpOutsideSystemd(t *testing.T) {
	t.Setenv("NOTIFY_SOCKET", "")
	if err := NotifyReady(); err != nil {
		t.Fatalf("NotifyReady with no socket = %v, want nil", err)
	}
}