package data

import (
	"context"
	"database/sql"
	"time"
)

type PredictPoint struct {
	ForecastTime time.Time
	RainMMx1000  int32
}

// ForecastRainAtIssued returns forecast hourly rows for a given station/provider at an exact issued_at time.
func ForecastRainAtIssued(ctx context.Context, stationID, provider string, issuedAt time.Time) ([]PredictPoint, error) {
	const q = `
        SELECT forecast_time, rain_mm_x1000
        FROM forecast_hourly
        WHERE station_id=$1 AND provider=$2 AND issued_at=$3
        ORDER BY forecast_time ASC`
	rows, err := DB().QueryContext(ctx, q, stationID, provider, issuedAt)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []PredictPoint
	for rows.Next() {
		var p PredictPoint
		var rain sql.NullInt32
		if err := rows.Scan(&p.ForecastTime, &rain); err != nil {
			continue
		}
		if rain.Valid {
			p.RainMMx1000 = rain.Int32
		}
		out = append(out, p)
	}
	return out, nil
}

// ResolveIssuedAtInBucket finds the latest issued_at in [bucket, bucket+1h) for station/provider.
func ResolveIssuedAtInBucket(ctx context.Context, stationID, provider string, bucketHour time.Time) (time.Time, bool, error) {
	const q = `SELECT issued_at FROM forecast_hourly WHERE station_id=$1 AND provider=$2 AND issued_at >= $3 AND issued_at < $3 + interval '1 hour' ORDER BY issued_at DESC LIMIT 1`
	var t time.Time
	err := DB().QueryRowContext(ctx, q, stationID, provider, bucketHour).Scan(&t)
	if err == sql.ErrNoRows {
		return time.Time{}, false, nil
	}
	if err != nil {
		return time.Time{}, false, err
	}
	return t, true, nil
}

// UpsertForecastRain writes rain-only rows for a provider at issued_at, upserting by key.
// Only the rain_mm_x1000 column is set/updated; other columns remain NULL or unchanged.
type UpsertRainItem struct {
	ForecastTime time.Time
	RainMMx1000  int32
}

func UpsertForecastRain(ctx context.Context, stationID, provider string, issuedAt time.Time, items []UpsertRainItem) error {
	if len(items) == 0 {
		return nil
	}
	const q = `
        INSERT INTO forecast_hourly (
            station_id, provider, issued_at, forecast_time, rain_mm_x1000
        ) VALUES ($1,$2,$3,$4,$5)
        ON CONFLICT (station_id, provider, issued_at, forecast_time) DO UPDATE SET
            rain_mm_x1000 = EXCLUDED.rain_mm_x1000`
	tx, err := DB().BeginTx(ctx, &sql.TxOptions{})
	if err != nil {
		return err
	}
	defer func() {
		_ = tx.Rollback()
	}()
	for _, it := range items {
		if _, err := tx.ExecContext(ctx, q, stationID, provider, issuedAt, it.ForecastTime, it.RainMMx1000); err != nil {
			return err
		}
	}
	return tx.Commit()
}