package main

import (
	"context"
	"database/sql"
	"database/sql/driver"
	"errors"
	"os"
	"reflect"
	"testing"
	"time"

	mysql "github.com/go-sql-driver/mysql"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
)

// A lost session must never reconnect without its temporary shadow tables.
type oneSessionConnector struct {
	driver.Connector
	used bool
}

func (c *oneSessionConnector) Connect(ctx context.Context) (driver.Conn, error) {
	if c.used {
		return nil, errors.New("temporary-table integration session cannot reconnect")
	}
	c.used = true
	return c.Connector.Connect(ctx)
}

func TestProtectedGPSWriteMySQLTemporaryTables(t *testing.T) {
	dsn := os.Getenv("BACKFILL_TEST_MYSQL_DSN")
	if dsn == "" {
		t.Skip("set BACKFILL_TEST_MYSQL_DSN for isolated temporary-table integration")
	}
	cfg, err := mysql.ParseDSN(dsn)
	if err != nil {
		t.Fatal("invalid integration DSN")
	}
	cfg.ParseTime = true
	cfg.Loc = time.FixedZone("Asia/Shanghai", 8*3600)
	connector, err := mysql.NewConnector(cfg)
	if err != nil {
		t.Fatal("integration connector unavailable")
	}
	db := sql.OpenDB(&oneSessionConnector{Connector: connector})
	db.SetMaxOpenConns(1)
	db.SetMaxIdleConns(1)
	defer db.Close()
	ctx := context.Background()
	for _, table := range []string{"vehicle_daily_mileage_source", "vehicle_daily_mileage", "vehicle_data_source"} {
		if _, err := db.ExecContext(ctx, "CREATE TEMPORARY TABLE gps_fixture_"+table+" LIKE "+table); err != nil {
			t.Fatal(err)
		}
		if _, err := db.ExecContext(ctx, "CREATE TEMPORARY TABLE "+table+" LIKE gps_fixture_"+table); err != nil {
			t.Fatal(err)
		}
	}
	loc := cfg.Loc
	prev := time.Date(2026, 10, 20, 23, 59, 0, 0, loc)
	end := time.Date(2026, 10, 21, 23, 59, 0, 0, loc)
	const vin = "LTESTGPSPROTECT001"
	key := "JT808:fixture@PLATFORM:g7s"
	if _, err := db.Exec(`INSERT INTO vehicle_daily_mileage_source
(vin,stat_date,protocol,source_key,source_ip,source_endpoint,phone,platform_name,first_total_mileage_km,latest_total_mileage_km,daily_mileage_km,sample_count,first_event_time,latest_event_time,quality_status,quality_reason)
VALUES (?,'2026-10-21','JT808',?,'1.2.3.4','1.2.3.4:1','fixture','G7s',100,120,20,200,?,?,'OK','historical_source_baseline'),
(?,'2026-10-21','JT808','JT808:other@PLATFORM:other','2.3.4.5','2.3.4.5:2','other','Other',100,101,1,3,?,?,'OK','historical_source_baseline')`, vin, key, prev, end, vin, prev, end.Add(-time.Minute)); err != nil {
		t.Fatal(err)
	}
	// Keep the existing manual final selected. This exercises the protected
	// write path without MySQL's temporary-table self-join restriction in the
	// independent projection query (covered separately by replay verification).
	if _, err := db.Exec(`INSERT INTO vehicle_daily_mileage_source (vin,stat_date,protocol,source_key,source_ip,daily_mileage_km,sample_count,quality_status,quality_reason,is_selected)
VALUES (?,'2026-10-21','JT808','manual-report','manual-import',88,1,'OK','manual_gps_report',1)`, vin); err != nil {
		t.Fatal(err)
	}
	if _, err := db.Exec(`INSERT INTO vehicle_daily_mileage (vin,stat_date,protocol,source_id,daily_mileage_km) VALUES (?,'2026-10-21','JT808',0,88)`, vin); err != nil {
		t.Fatal(err)
	}
	agg := &metricAgg{VIN: vin, Date: "2026-10-21", Protocol: envelope.ProtocolJT808, SourceKey: key, Phone: "fixture", SourceEndpoint: "1.2.3.4:3", SourceCode: "g7s", SourceKind: "PLATFORM", PlatformName: "G7s", FirstKM: 90, LatestKM: 115, Count: 100, FirstEventTime: prev.Add(-24 * time.Hour), LatestEventTime: end.Add(-time.Hour), QualityStatus: "OK", QualityReason: "historical_source_baseline"}
	read := func() []any {
		var first, last, daily float64
		var count int
		var firstTS, lastTS time.Time
		if err := db.QueryRow(`SELECT first_total_mileage_km,latest_total_mileage_km,daily_mileage_km,sample_count,first_event_time,latest_event_time FROM vehicle_daily_mileage_source WHERE vin=? AND source_key=?`, vin, key).Scan(&first, &last, &daily, &count, &firstTS, &lastTS); err != nil {
			t.Fatal(err)
		}
		return []any{first, last, daily, count, firstTS, lastTS}
	}
	var before []any
	for run := 0; run < 2; run++ {
		if _, err := writeAggregates(ctx, db, map[string]*metricAgg{"fixture": agg}, 500); err != nil {
			t.Fatal(err)
		}
		got := read()
		if got[0] != float64(100) || got[1] != float64(120) || got[2] != float64(20) || got[3] != 200 {
			t.Fatalf("durable data overwritten: %+v", got)
		}
		if run == 1 && !reflect.DeepEqual(before, got) {
			t.Fatalf("repeated backfill changed business values: before=%+v after=%+v", before, got)
		}
		before = got
	}
	var sources int
	if err := db.QueryRow("SELECT COUNT(*) FROM vehicle_daily_mileage_source WHERE vin=?", vin).Scan(&sources); err != nil {
		t.Fatal(err)
	}
	if sources != 3 {
		t.Fatalf("missing durable alternate source: %d", sources)
	}
	// Newer event with a lower counter wins by time, not MAX(odometer).
	agg.FirstKM, agg.FirstEventTime = 100, prev
	agg.LatestKM, agg.LatestEventTime = 119, end.Add(time.Second)
	if _, err := writeAggregates(ctx, db, map[string]*metricAgg{"fixture": agg}, 500); err != nil {
		t.Fatal(err)
	}
	if got := read(); got[1] != float64(119) || got[2] != float64(19) {
		t.Fatalf("newer event rejected: %+v", got)
	}
	agg.LatestKM, agg.LatestEventTime = 121, end.Add(2*time.Second)
	if _, err := writeAggregates(ctx, db, map[string]*metricAgg{"fixture": agg}, 500); err != nil {
		t.Fatal(err)
	}
	var final float64
	if err := db.QueryRow("SELECT daily_mileage_km FROM vehicle_daily_mileage WHERE vin=?", vin).Scan(&final); err != nil {
		t.Fatal(err)
	}
	if final != 88 {
		t.Fatalf("manual final overwritten: %v", final)
	}
	t.Log("temporary-table scenarios passed: incomplete RAW, alternate source retention, repeated backfill, event ordering, manual final; production rows modified=0")
}