chore: initialize go-sip repository

internal/callwindow/window.go

@@ -0,0 +1,33 @@
+// Package callwindow enforces the fixed legal window for SIP outbound dialing.
+package callwindow
+
+import (
+	"fmt"
+	"time"
+)
+
+const (
+	LocationName = "Asia/Shanghai"
+	OpenHour     = 9
+	CloseHour    = 20
+)
+
+var shanghai = time.FixedZone(LocationName, 8*60*60)
+
+// Allowed reports whether SIP outbound dialing is permitted at now. The
+// boundary is [09:00, 20:00) in Asia/Shanghai; the input's instant, not its
+// presentation timezone, is authoritative.
+func Allowed(now time.Time) bool {
+	local := now.In(shanghai)
+	minutes := local.Hour()*60 + local.Minute()
+	return minutes >= OpenHour*60 && minutes < CloseHour*60
+}
+
+// Check returns a stable, actionable error when outbound dialing is closed.
+func Check(now time.Time) error {
+	local := now.In(shanghai)
+	if Allowed(now) {
+		return nil
+	}
+	return fmt.Errorf("SIP outbound dialing is closed at %s; allowed window is %02d:00-%02d:00 %s", local.Format("2006-01-02 15:04:05 -0700"), OpenHour, CloseHour, LocationName)
+}

internal/callwindow/window_test.go

@@ -0,0 +1,49 @@
+package callwindow
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestAllowedBoundariesInShanghai(t *testing.T) {
+	location := time.FixedZone("test", 8*60*60)
+	tests := []struct {
+		name string
+		at   time.Time
+		want bool
+	}{
+		{name: "before opening", at: time.Date(2026, 9, 20, 8, 59, 59, 0, location), want: false},
+		{name: "opening", at: time.Date(2026, 9, 20, 9, 0, 0, 0, location), want: true},
+		{name: "before closing", at: time.Date(2026, 9, 20, 19, 59, 59, 0, location), want: true},
+		{name: "closing", at: time.Date(2026, 9, 20, 20, 0, 0, 0, location), want: false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Allowed(tt.at); got != tt.want {
+				t.Fatalf("Allowed(%s)=%v, want %v", tt.at, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAllowedConvertsUTCToShanghai(t *testing.T) {
+	if !Allowed(time.Date(2026, 9, 20, 1, 0, 0, 0, time.UTC)) {
+		t.Fatal("01:00 UTC should be 09:00 Asia/Shanghai and allowed")
+	}
+	if Allowed(time.Date(2026, 9, 20, 12, 0, 0, 0, time.UTC)) {
+		t.Fatal("12:00 UTC should be 20:00 Asia/Shanghai and rejected")
+	}
+}
+
+func TestCheckExplainsClosedWindow(t *testing.T) {
+	err := Check(time.Date(2026, 9, 20, 20, 0, 0, 0, time.FixedZone("test", 8*60*60)))
+	if err == nil {
+		t.Fatal("expected closed-window error")
+	}
+	for _, want := range []string{"09:00", "20:00", "Asia/Shanghai"} {
+		if !strings.Contains(err.Error(), want) {
+			t.Fatalf("error %q does not contain %q", err, want)
+		}
+	}
+}