package main

import (
	"context"
	"database/sql"
	"flag"
	"fmt"
	"log"
	"os"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	_ "github.com/go-sql-driver/mysql"
	_ "github.com/taosdata/driver-go/v3/taosWS"

	"lingniu/vehicle-data-platform/apps/api/internal/config"
	"lingniu/vehicle-data-platform/apps/api/internal/openplatform"
)

func main() {
	date := flag.String("date", "", "last date to calculate in yyyy-MM-dd; defaults to yesterday in Asia/Shanghai")
	lookback := flag.Int("lookback-days", envInt("OPEN_STAT_LOOKBACK_DAYS", 2), "number of dates ending at -date")
	noise := flag.Float64("hydrogen-noise-kg", envFloat("OPEN_STAT_HYDROGEN_NOISE_KG", 0.05), "ignored mass jitter")
	maxDrop := flag.Float64("hydrogen-max-drop-kg", envFloat("OPEN_STAT_HYDROGEN_MAX_DROP_KG", 20), "maximum accepted drop between samples")
	vin := flag.String("vin", "", "optional 17-character VIN for a scoped rebuild")
	vinWorkers := flag.Int("vin-workers", envInt("OPEN_STAT_VIN_WORKERS", 4), "parallel per-VIN queries for an all-vehicle day")
	allDates := flag.Bool("all-dates", false, "rebuild every available completed event date; optionally scoped by -vin")
	dryRun := flag.Bool("dry-run", false, "calculate and print results without changing MySQL")
	seedStream := flag.Bool("seed-stream-state", false, "atomically seed current-day segment stream watermarks during a controlled writer handoff")
	flag.Parse()

	cfg := config.Load()
	if cfg.MySQLDSN == "" || cfg.TDengineDSN == "" {
		log.Fatal("MYSQL_DSN and TDENGINE_DSN are required")
	}
	mysqlDB, err := sql.Open("mysql", cfg.MySQLDSN)
	if err != nil {
		log.Fatal(err)
	}
	defer mysqlDB.Close()
	tdengineDB, err := sql.Open(cfg.TDengineDriver, cfg.TDengineDSN)
	if err != nil {
		log.Fatal(err)
	}
	defer tdengineDB.Close()

	location := time.FixedZone("Asia/Shanghai", 8*60*60)
	endDate := time.Now().In(location).AddDate(0, 0, -1)
	if *date != "" {
		endDate, err = time.ParseInLocation("2006-01-02", *date, location)
		if err != nil {
			log.Fatal("-date must use yyyy-MM-dd")
		}
	}
	if *lookback < 1 || *lookback > 31 {
		log.Fatal("-lookback-days must be between 1 and 31")
	}
	if *vinWorkers < 1 || *vinWorkers > 16 {
		log.Fatal("-vin-workers must be between 1 and 16")
	}
	normalizedVIN := strings.ToUpper(strings.TrimSpace(*vin))
	if *seedStream && normalizedVIN != "" {
		log.Fatal("-seed-stream-state requires an all-vehicle rebuild")
	}
	if *seedStream && *dryRun {
		log.Fatal("-seed-stream-state cannot be combined with -dry-run")
	}
	tdengineDB.SetMaxOpenConns(*vinWorkers)
	timeout := 30 * time.Minute
	if *allDates {
		timeout = 6 * time.Hour
	}
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()
	capacities, err := openplatform.LoadHydrogenCapacities(ctx, mysqlDB)
	if err != nil {
		log.Fatalf("load hydrogen tank capacities: %v", err)
	}
	if normalizedVIN != "" {
		if _, ok := capacities[normalizedVIN]; !ok {
			log.Fatalf("no active hydrogen tank capacity for VIN %s", normalizedVIN)
		}
	}
	startDate := time.Date(endDate.Year(), endDate.Month(), endDate.Day(), 0, 0, 0, 0, location).AddDate(0, 0, -(*lookback - 1))
	if *allDates {
		var first, last time.Time
		var found bool
		var rangeErr error
		if normalizedVIN == "" {
			first, last, found, rangeErr = openplatform.HydrogenObservationDateRangeForAll(ctx, tdengineDB, cfg.TDengineDatabase)
		} else {
			first, last, found, rangeErr = openplatform.HydrogenObservationDateRange(ctx, tdengineDB, cfg.TDengineDatabase, normalizedVIN)
		}
		if rangeErr != nil {
			log.Fatalf("load hydrogen date range: %v", rangeErr)
		}
		if !found {
			log.Fatal("no GB32960 history found")
		}
		first = first.In(location)
		last = last.In(location)
		startDate = time.Date(first.Year(), first.Month(), first.Day(), 0, 0, 0, 0, location)
		endDate = time.Date(last.Year(), last.Month(), last.Day(), 0, 0, 0, 0, location)
		now := time.Now().In(location)
		lastCompletedDate := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, location).AddDate(0, 0, -1)
		if endDate.After(lastCompletedDate) {
			endDate = lastCompletedDate
		}
		scope := "all-vehicles"
		if normalizedVIN != "" {
			scope = normalizedVIN
		}
		fmt.Printf("scope=%s date_from=%s date_to=%s mode=all-dates\n", scope, startDate.Format("2006-01-02"), endDate.Format("2006-01-02"))
	}
	for start := startDate; !start.After(endDate); start = start.AddDate(0, 0, 1) {
		date := start.Format("2006-01-02")
		energyParameters, parameterErr := openplatform.LoadHydrogenCalculationParameters(ctx, mysqlDB, start)
		if parameterErr != nil {
			log.Fatalf("load hydrogen energy parameters for %s: %v", date, parameterErr)
		}
		var stats []openplatform.HydrogenDailyStat
		observationCount := 0
		if normalizedVIN == "" {
			var vins []string
			vins, err = openplatform.LoadHydrogenObservationVINs(ctx, tdengineDB, cfg.TDengineDatabase, start, start.AddDate(0, 0, 1), capacities)
			if err == nil {
				stats, observationCount, err = buildHydrogenDailyStatsByVIN(ctx, tdengineDB, cfg.TDengineDatabase, capacities, energyParameters, vins, start, *noise, *maxDrop, *vinWorkers)
			}
		} else {
			var observations []openplatform.HydrogenObservation
			observations, err = openplatform.LoadHydrogenObservationsForVIN(ctx, tdengineDB, cfg.TDengineDatabase, start, start.AddDate(0, 0, 1), capacities, normalizedVIN)
			observationCount = len(observations)
			stats = openplatform.BuildHydrogenDailyStatsOrderedWithParameters(observations, date, *noise, *maxDrop, energyParameters)
		}
		if err != nil {
			log.Fatalf("load hydrogen observations for %s: %v", date, err)
		}
		if !*dryRun {
			if *seedStream {
				err = openplatform.ReplaceHydrogenDailyStatsAndSeedStream(ctx, mysqlDB, date, stats)
			} else if normalizedVIN == "" {
				err = openplatform.ReplaceHydrogenDailyStats(ctx, mysqlDB, date, stats)
			} else {
				err = openplatform.ReplaceHydrogenDailyStatsForVIN(ctx, mysqlDB, date, normalizedVIN, stats)
			}
			if err != nil {
				log.Fatalf("persist hydrogen statistics for %s: %v", date, err)
			}
		}
		mode := "write"
		if *dryRun {
			mode = "dry-run"
		}
		if normalizedVIN != "" && len(stats) == 1 {
			fmt.Printf("date=%s vin=%s observations=%d consumption_kg=%.3f refuels=%d quality=%s mode=%s\n", date, normalizedVIN, observationCount, stats[0].ConsumptionKg, stats[0].RefuelCount, stats[0].QualityStatus, mode)
		} else {
			fmt.Printf("date=%s observations=%d vehicles=%d mode=%s\n", date, observationCount, len(stats), mode)
		}
	}
}

type hydrogenVINResult struct {
	VIN              string
	ObservationCount int
	Stats            []openplatform.HydrogenDailyStat
	Err              error
}

func buildHydrogenDailyStatsByVIN(
	ctx context.Context,
	tdengineDB *sql.DB,
	database string,
	capacities map[string]float64,
	energyParameters map[string]openplatform.HydrogenCalculationParameters,
	vins []string,
	start time.Time,
	noiseKg float64,
	maxDropKg float64,
	workerCount int,
) ([]openplatform.HydrogenDailyStat, int, error) {
	if len(vins) == 0 {
		return nil, 0, nil
	}
	if workerCount > len(vins) {
		workerCount = len(vins)
	}
	workerCtx, cancel := context.WithCancel(ctx)
	defer cancel()
	jobs := make(chan string)
	results := make(chan hydrogenVINResult, len(vins))
	var workers sync.WaitGroup
	for worker := 0; worker < workerCount; worker++ {
		workers.Add(1)
		go func() {
			defer workers.Done()
			for vin := range jobs {
				observations, err := openplatform.LoadHydrogenObservationsForVIN(workerCtx, tdengineDB, database, start, start.AddDate(0, 0, 1), capacities, vin)
				if err != nil {
					results <- hydrogenVINResult{VIN: vin, Err: err}
					continue
				}
				results <- hydrogenVINResult{
					VIN: vin, ObservationCount: len(observations),
					Stats: openplatform.BuildHydrogenDailyStatsOrderedWithParameters(observations, start.Format("2006-01-02"), noiseKg, maxDropKg, energyParameters),
				}
			}
		}()
	}
	go func() {
		defer close(jobs)
		for _, vin := range vins {
			select {
			case jobs <- vin:
			case <-workerCtx.Done():
				return
			}
		}
	}()
	go func() {
		workers.Wait()
		close(results)
	}()
	stats := make([]openplatform.HydrogenDailyStat, 0, len(vins))
	observationCount := 0
	var firstErr error
	for result := range results {
		if result.Err != nil {
			if firstErr == nil {
				firstErr = fmt.Errorf("VIN %s: %w", result.VIN, result.Err)
				cancel()
			}
			continue
		}
		observationCount += result.ObservationCount
		stats = append(stats, result.Stats...)
	}
	if firstErr != nil {
		return nil, 0, firstErr
	}
	sort.Slice(stats, func(i, j int) bool { return stats[i].VIN < stats[j].VIN })
	return stats, observationCount, nil
}

func envInt(name string, fallback int) int {
	value, err := strconv.Atoi(os.Getenv(name))
	if err != nil {
		return fallback
	}
	return value
}

func envFloat(name string, fallback float64) float64 {
	value, err := strconv.ParseFloat(os.Getenv(name), 64)
	if err != nil {
		return fallback
	}
	return value
}