Sub2API v1.0 - AI API 网关（二开初始版本，基于上游 Wei-Shaw/sub2api）

backend/internal/service/proxy_fallback_test.go

@@ -0,0 +1,73 @@
+//go:build unit
+
+package service
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func mkProxy(id int64, mode string, backup *int64, expiresInDays *int, now time.Time) Proxy {
+	p := Proxy{ID: id, FallbackMode: mode, BackupProxyID: backup}
+	if expiresInDays != nil {
+		t := now.AddDate(0, 0, *expiresInDays)
+		p.ExpiresAt = &t
+	}
+	return p
+}
+func i64(v int64) *int64 { return &v }
+func di(v int) *int      { return &v }
+
+func TestResolveFallbackTarget(t *testing.T) {
+	now := time.Now()
+	t.Run("none keeps original", func(t *testing.T) {
+		a := mkProxy(1, FallbackModeNone, nil, di(-1), now)
+		by := map[int64]Proxy{1: a}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.False(t, change)
+		require.Nil(t, target)
+	})
+	t.Run("direct -> nil target, change", func(t *testing.T) {
+		a := mkProxy(1, FallbackModeDirect, nil, di(-1), now)
+		by := map[int64]Proxy{1: a}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.True(t, change)
+		require.Nil(t, target)
+	})
+	t.Run("proxy -> healthy backup", func(t *testing.T) {
+		b := mkProxy(2, FallbackModeNone, nil, di(30), now)
+		a := mkProxy(1, FallbackModeProxy, i64(2), di(-1), now)
+		by := map[int64]Proxy{1: a, 2: b}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.True(t, change)
+		require.NotNil(t, target)
+		require.Equal(t, int64(2), *target)
+	})
+	t.Run("chain A->B(expired)->C(healthy)", func(t *testing.T) {
+		c := mkProxy(3, FallbackModeNone, nil, di(30), now)
+		b := mkProxy(2, FallbackModeProxy, i64(3), di(-1), now)
+		a := mkProxy(1, FallbackModeProxy, i64(2), di(-1), now)
+		by := map[int64]Proxy{1: a, 2: b, 3: c}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.True(t, change)
+		require.Equal(t, int64(3), *target)
+	})
+	t.Run("cycle A->B->A keeps original", func(t *testing.T) {
+		b := mkProxy(2, FallbackModeProxy, i64(1), di(-1), now)
+		a := mkProxy(1, FallbackModeProxy, i64(2), di(-1), now)
+		by := map[int64]Proxy{1: a, 2: b}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.False(t, change)
+		require.Nil(t, target)
+	})
+	t.Run("chain tail direct fallback", func(t *testing.T) {
+		b := mkProxy(2, FallbackModeDirect, nil, di(-1), now)
+		a := mkProxy(1, FallbackModeProxy, i64(2), di(-1), now)
+		by := map[int64]Proxy{1: a, 2: b}
+		target, change := ResolveProxyFallbackTarget(a, by, now)
+		require.True(t, change)
+		require.Nil(t, target)
+	})
+}