package api

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"visiona-backend/internal/device"
	"visiona-backend/internal/session"
)

// stubDriverStatusFetcher 是 driverStatusFetcher 的測試替身。
//
// 可設定：回傳的即時 status（liveStatus）、回傳的 error（err），並記錄呼叫參數，
// 用來驗證 handler 是否有嘗試查詢、以及傳的序號 / userID 正確。
type stubDriverStatusFetcher struct {
	liveStatus string
	err        error

	called    bool
	gotUserID string
	gotSerial string
}

func (s *stubDriverStatusFetcher) FetchDriverStatus(_ context.Context, userID, serial string) (string, error) {
	s.called = true
	s.gotUserID = userID
	s.gotSerial = serial
	return s.liveStatus, s.err
}

// getDeviceStatus 打 GET /api/devices/:id 並解出回應的 data.status 欄。
func getDeviceStatus(t *testing.T, r *gin.Engine, id string) (int, string) {
	t.Helper()
	w := httptest.NewRecorder()
	r.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/api/devices/"+id, nil))

	var sb SuccessBody
	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &sb), "body=%s", w.Body.String())
	if w.Code != http.StatusOK {
		return w.Code, ""
	}
	data, ok := sb.Data.(map[string]any)
	require.True(t, ok, "data 應為物件，實際 body=%s", w.Body.String())
	status, _ := data["status"].(string)
	return w.Code, status
}

// newGetDeviceFixture 建 router + 塞一顆 device，可注入自訂 Deps 欄位（fetcher）。
func newGetDeviceFixture(t *testing.T, d *device.Device, mutate func(*Deps)) *gin.Engine {
	t.Helper()
	repo := device.NewInMemoryRepository()
	require.NoError(t, repo.Save(context.Background(), d))

	r := gin.New()
	r.Use(RequestIDMiddleware())
	r.Use(injectStaticUserContext(d.OwnerUserID, ""))
	g := r.Group("/api")

	deps := Deps{
		DeviceRepo:   repo,
		SessionStore: &fakeSessionStore{},
	}
	if mutate != nil {
		mutate(&deps)
	}
	registerDeviceRoutes(g, deps)
	return r
}

// TestGetDevice_ProxySuccess_OverridesDBStatus 驗證：proxy 成功拿到即時 driver status
// （"connected"）時，回應的 status 用即時值覆蓋 DB 的靜態值（"unknown"）。
//
// 這是 gate isDriverConnected 能通過的核心路徑（DB unknown → 即時 connected）。
func TestGetDevice_ProxySuccess_OverridesDBStatus(t *testing.T) {
	fetcher := &stubDriverStatusFetcher{liveStatus: "connected"}
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "0xB906162C",
		RemoteStatus: device.RemoteStatusOnline,
		Status:       device.USBStatusUnknown, // DB 靜態值
		CreatedAt:    time.Now().UTC(),
	}, func(d *Deps) { d.DriverStatusFetcher = fetcher })

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code)
	assert.Equal(t, "connected", status, "應以即時 driver status 覆蓋 DB unknown")

	assert.True(t, fetcher.called, "應嘗試打 local agent")
	assert.Equal(t, "0xB906162C", fetcher.gotSerial, "應以序號走 serial 路由")
	assert.Equal(t, "demo-user", fetcher.gotUserID, "應帶當前 user")
}

// TestGetDevice_ProxyFails_FallbackDBStatus 驗證：proxy 回 error（local agent 不可達 /
// 該序號無 session）時 graceful fallback——回 DB 的 status，且 GET :id 仍是 200。
func TestGetDevice_ProxyFails_FallbackDBStatus(t *testing.T) {
	fetcher := &stubDriverStatusFetcher{err: errDriverStatusUnavailable}
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "0xB906162C",
		RemoteStatus: device.RemoteStatusOnline,
		Status:       device.USBStatusOnline, // DB 靜態值
		CreatedAt:    time.Now().UTC(),
	}, func(d *Deps) { d.DriverStatusFetcher = fetcher })

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code, "proxy 失敗不能讓詳情頁掛")
	assert.Equal(t, device.USBStatusOnline, status, "應 fallback 回 DB status")
	assert.True(t, fetcher.called)
}

// TestGetDevice_TunnelDisconnected_FallbackDBStatus 驗證：tunnel 離線
// （fetcher 回 session.ErrSessionNotFound）時 fallback DB status、仍回 200。
func TestGetDevice_TunnelDisconnected_FallbackDBStatus(t *testing.T) {
	fetcher := &stubDriverStatusFetcher{err: session.ErrSessionNotFound}
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "0xB906162C",
		RemoteStatus: device.RemoteStatusOffline,
		Status:       device.USBStatusUnknown,
		CreatedAt:    time.Now().UTC(),
	}, func(d *Deps) { d.DriverStatusFetcher = fetcher })

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code)
	assert.Equal(t, device.USBStatusUnknown, status, "tunnel 離線應 fallback DB unknown")
	assert.True(t, errors.Is(fetcher.err, session.ErrSessionNotFound))
}

// TestGetDevice_EmptyLiveStatus_FallbackDBStatus 驗證：proxy 成功但回空 status
// （不該覆蓋成空字串）時，保留 DB status。
func TestGetDevice_EmptyLiveStatus_FallbackDBStatus(t *testing.T) {
	fetcher := &stubDriverStatusFetcher{liveStatus: ""}
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "0xB906162C",
		RemoteStatus: device.RemoteStatusOnline,
		Status:       device.USBStatusOnline,
		CreatedAt:    time.Now().UTC(),
	}, func(d *Deps) { d.DriverStatusFetcher = fetcher })

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code)
	assert.Equal(t, device.USBStatusOnline, status, "空即時 status 不該覆蓋 DB status")
}

// TestGetDevice_NoSerial_SkipsProxy 驗證：device 無序號時完全不打 local agent
// （無序號不支援 serial 路由），直接回 DB status。
func TestGetDevice_NoSerial_SkipsProxy(t *testing.T) {
	fetcher := &stubDriverStatusFetcher{liveStatus: "connected"}
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "", // 無序號
		RemoteStatus: device.RemoteStatusOnline,
		Status:       device.USBStatusUnknown,
		CreatedAt:    time.Now().UTC(),
	}, func(d *Deps) { d.DriverStatusFetcher = fetcher })

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code)
	assert.Equal(t, device.USBStatusUnknown, status, "無序號回 DB status")
	assert.False(t, fetcher.called, "無序號不該打 local agent")
}

// TestGetDevice_NoFetcher_ReturnsDBStatus 驗證：沒有 fetcher（Forwarder/SessionStore
// 未配置，resolveDriverStatusFetcher 回 nil）時 handler 不 panic，直接回 DB status。
func TestGetDevice_NoFetcher_ReturnsDBStatus(t *testing.T) {
	r := newGetDeviceFixture(t, &device.Device{
		ID: "dev1", OwnerUserID: "demo-user", Name: "KL520", DeviceType: "kl520",
		SerialNumber: "0xB906162C",
		RemoteStatus: device.RemoteStatusOnline,
		Status:       device.USBStatusOnline,
		CreatedAt:    time.Now().UTC(),
	}, nil) // 不注入 fetcher；fakeSessionStore 存在但 Forwarder 為 nil → newForwarder... 回 nil

	code, status := getDeviceStatus(t, r, "dev1")
	require.Equal(t, http.StatusOK, code)
	assert.Equal(t, device.USBStatusOnline, status)
}

// TestResolveDriverStatusFetcher_NilWhenNoForwarder 驗證：Forwarder 為 nil 時
// default fetcher 為 nil（handler 據此略過即時查詢）。
func TestResolveDriverStatusFetcher_NilWhenNoForwarder(t *testing.T) {
	assert.Nil(t, resolveDriverStatusFetcher(Deps{SessionStore: &fakeSessionStore{}}),
		"Forwarder 為 nil 應回 nil fetcher")
	assert.Nil(t, resolveDriverStatusFetcher(Deps{}),
		"Forwarder + SessionStore 皆 nil 應回 nil fetcher")
}

// TestResolveDriverStatusFetcher_InjectedWins 驗證：Deps.DriverStatusFetcher 非 nil 時
// 優先用注入的 stub（不 fallback default）。
func TestResolveDriverStatusFetcher_InjectedWins(t *testing.T) {
	stub := &stubDriverStatusFetcher{}
	got := resolveDriverStatusFetcher(Deps{DriverStatusFetcher: stub})
	assert.Same(t, stub, got)
}