package app

import (
	"encoding/json"
	"fmt"
	"testing"
)

// Pull to refresh on 附近 should bring different faces without sending the
// reader across town. Before this, a seed replaced the distance ordering
// entirely and the list became a plain shuffle of the whole city.
func TestNearbyShuffleStaysWithinDistanceBandsMySQL(t *testing.T) {
	db := isolatedIMDatabase(t)
	a := &App{db: db, hub: NewHub(), config: Config{Environment: "development", JWTSecret: "isolated-im-regression-secret-only"}}
	// Viewer at the city centre; then three people ~200m away and three ~40km away.
	const centreLat, centreLng = 22.5431, 114.0579
	if _, err := db.Exec(`INSERT INTO user_location_states(user_id,city_code,latitude,longitude) VALUES(1,'440300',?,?)`, centreLat, centreLng); err != nil {
		t.Fatal(err)
	}
	near := map[int64]bool{}
	for id := int64(2); id <= 7; id++ {
		if id > 3 {
			if _, err := db.Exec(`INSERT INTO users(id,public_id,password_hash) VALUES(?,CONCAT('NEARBY',?),'!NO_LOGIN')`, id, id); err != nil {
				t.Fatal(err)
			}
			for _, statement := range []string{
				`INSERT INTO user_profiles(user_id,nickname) VALUES(?,CONCAT('附近',?))`,
				`INSERT INTO user_privacy_settings(user_id) VALUES(?)`,
			} {
				args := []any{id}
				if statement == `INSERT INTO user_profiles(user_id,nickname) VALUES(?,CONCAT('附近',?))` {
					args = append(args, id)
				}
				if _, err := db.Exec(statement, args...); err != nil {
					t.Fatal(err)
				}
			}
		}
		offset := 0.002 * float64(id) // ~200m steps
		if id >= 5 {
			offset = 0.36 * float64(id) // ~40km and beyond
		} else {
			near[id] = true
		}
		if _, err := db.Exec(`INSERT INTO user_location_states(user_id,city_code,latitude,longitude) VALUES(?,'440300',?,?)`, id, centreLat+offset, centreLng); err != nil {
			t.Fatal(err)
		}
	}
	page := func(seed int) []int64 {
		t.Helper()
		var payload struct {
			Items []struct {
				ID int64 `json:"id"`
			} `json:"items"`
		}
		query := "/api/v1/nearby/users?page=1&pageSize=20"
		if seed > 0 {
			query += fmt.Sprintf("&seed=%d", seed)
		}
		if err := json.Unmarshal(imTestCall(t, a.nearby, 1, "GET", query, "", 200), &payload); err != nil {
			t.Fatal(err)
		}
		ids := []int64{}
		for _, item := range payload.Items {
			ids = append(ids, item.ID)
		}
		return ids
	}

	t.Run("the near band always comes first, whatever the seed", func(t *testing.T) {
		for _, seed := range []int{0, 7, 12345, 2147483647} {
			ids := page(seed)
			if len(ids) < 6 {
				t.Fatalf("seed %d 返回 %v", seed, ids)
			}
			for index, id := range ids[:3] {
				if !near[id] {
					t.Fatalf("seed %d 第 %d 位是远处的 %d: %v", seed, index+1, id, ids)
				}
			}
			for _, id := range ids[3:] {
				if near[id] {
					t.Fatalf("seed %d 把近处的人排到了后面: %v", seed, ids)
				}
			}
		}
	})

	t.Run("different seeds reorder people inside the band", func(t *testing.T) {
		seen := map[string]bool{}
		for seed := 1; seed <= 40; seed++ {
			ids := page(seed)
			seen[fmt.Sprint(ids[:3])] = true
		}
		if len(seen) < 2 {
			t.Fatalf("刷新应当换顺序，实际只有一种排列: %v", seen)
		}
	})

	t.Run("one seed is stable, so paging cannot repeat or skip a row", func(t *testing.T) {
		first := page(99)
		for attempt := 0; attempt < 3; attempt++ {
			if fmt.Sprint(page(99)) != fmt.Sprint(first) {
				t.Fatalf("同一 seed 必须给出同一顺序: %v vs %v", page(99), first)
			}
		}
	})
}