package db

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

	mssqldb "github.com/denisenkom/go-mssqldb" // for error inspection
	log "github.com/sirupsen/logrus"

	"gitea.futuresens.co.uk/futuresens/hardlink/types"
)

// InitMSSQL opens and pings the SQL Server instance (keeps your original behaviour)
func InitMSSQL(port int, user, password, database string) (*sql.DB, error) {
	if port <= 0 || user == "" || database == "" {
		return nil, errors.New("incomplete database configuration")
	}

	dsn := fmt.Sprintf(
		"sqlserver://%s:%s@%s:%d?database=%s&encrypt=disable",
		user, password, "localhost", port, database,
	)

	db, err := sql.Open("sqlserver", dsn)
	if err != nil {
		return nil, err
	}

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	if err := db.PingContext(ctx); err != nil {
		db.Close()
		return nil, err
	}

	if err := db.QueryRowContext(ctx, "SELECT 1").Scan(new(int)); err != nil {
		db.Close()
		return nil, err
	}
	log.Info("Database connection established")
	return db, nil
}

func parseDateOnly(s string) (time.Time, error) {
	parsed, err := time.Parse(types.CustomLayout, s)
	if err == nil {
		// construct midnight in local timezone, then convert to UTC for storage consistency
		localMidnight := time.Date(parsed.Year(), parsed.Month(), parsed.Day(), 0, 0, 0, 0, time.Local)
		return localMidnight.UTC(), nil
	}
	return time.Time{}, fmt.Errorf("parseDateOnly error: parsing %q: %w", s, err)
}

// InsertPreauth stores a preauthorization record. It is idempotent: duplicate TxnReference is ignored.
func InsertPreauth(ctx context.Context, db *sql.DB, m map[string]string, checkoutDate string) error {
	const funcName = "InsertPreauth"

	totalMinorUnits := m[types.TotalAmount]
	txnReference := m[types.Reference]
	if txnReference == "" {
		return fmt.Errorf("%s: missing REFERENCE", funcName)
	}
	if totalMinorUnits == "" {
		return fmt.Errorf("%s: missing TotalAmount", funcName)
	}

	// parse minor units, fallback to 0 on parse error but report it
	amountInt, err := strconv.ParseInt(totalMinorUnits, 10, 64)
	if err != nil {
		log.WithFields(log.Fields{
			"func":  funcName,
			"value": totalMinorUnits,
			"error": err,
		}).Warnf("parsing TotalAmount, defaulting to 0")
		amountInt = 0
	}
	totalAmount := float64(amountInt) / 100.0

	txnTime := time.Now().UTC()

	// parse departure / checkout date and compute release date (48h after departure)
	checkOutDate, err := parseDateOnly(checkoutDate)
	if err != nil {
		return fmt.Errorf("InsertPreauth: parsing checkoutDate %q: %w", checkoutDate, err)
	}
	releaseDate := checkOutDate.Add(48 * time.Hour)

	const stmt = `
INSERT INTO dbo.Preauthorizations
    (TxnReference, TotalMinorUnits, TotalAmount, TxnDateTime, DepartureDate, ReleaseDate)
VALUES
    (@TxnReference, @TotalMinorUnits, @TotalAmount, @TxnDateTime, @DepartureDate, @ReleaseDate);
`
	_, err = db.ExecContext(ctx, stmt,
		sql.Named("TxnReference", txnReference),
		sql.Named("TotalMinorUnits", totalMinorUnits),
		sql.Named("TotalAmount", totalAmount),
		sql.Named("TxnDateTime", txnTime),
		sql.Named("DepartureDate", checkOutDate),
		sql.Named("ReleaseDate", releaseDate),
	)
	if err != nil {
		// handle duplicate-key (unique constraint) gracefully: SQL Server error numbers 2601/2627
		var sqlErr mssqldb.Error
		if errors.As(err, &sqlErr) {
			if sqlErr.Number == 2627 || sqlErr.Number == 2601 {
				log.Infof("InsertPreauth: preauth %s already exists (duplicate key) - ignoring", txnReference)
				return nil
			}
		}
		return fmt.Errorf("InsertPreauth exec: %w", err)
	}

	log.Infof("Inserted preauth %s amount=%s minorUnits release=%s", txnReference, totalMinorUnits, releaseDate.Format(time.RFC3339))
	return nil
}

// GetDuePreauths returns preauths with ReleaseDate <= now where Released = 0.
// If limit > 0, the query uses TOP(limit) to bound results at DB level.
func GetDuePreauths(ctx context.Context, db *sql.DB, now time.Time, limit int) ([]types.PreauthRec, error) {
	baseQuery := `
SELECT Id, TxnReference, TotalMinorUnits, TotalAmount, TxnDateTime, DepartureDate, ReleaseDate, Released, ReleasedAt
FROM dbo.Preauthorizations
WHERE Released = 0 AND ReleaseDate <= @Now
ORDER BY ReleaseDate ASC
`
	query := baseQuery
	if limit > 0 {
		// embed TOP to keep DB from returning everything; limit is controlled by the caller.
		query = strings.Replace(baseQuery, "SELECT", fmt.Sprintf("SELECT TOP (%d)", limit), 1)
	}

	rows, err := db.QueryContext(ctx, query, sql.Named("Now", now))
	if err != nil {
		return nil, fmt.Errorf("GetDuePreauths query: %w", err)
	}
	defer rows.Close()

	var out []types.PreauthRec
	for rows.Next() {
		var r types.PreauthRec
		var departure sql.NullTime
		var releasedAt sql.NullTime
		// Note: adjust scanning targets if types.PreauthRec fields differ
		if err := rows.Scan(
			&r.Id,
			&r.TxnReference,
			&r.TotalMinorUnits,
			&r.TotalAmount,
			&r.TxnDateTime,
			&departure,
			&r.ReleaseDate,
			&r.Released,
			&releasedAt,
		); err != nil {
			return nil, fmt.Errorf("GetDuePreauths scan: %w", err)
		}

		if departure.Valid {
			r.DepartureDate = departure.Time
		} else {
			r.DepartureDate = time.Time{}
		}
		r.ReleasedAt = releasedAt

		out = append(out, r)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("GetDuePreauths rows: %w", err)
	}
	return out, nil
}

// MarkPreauthReleased sets Released=1 and stores the timestamp. Returns error if no rows updated.
func MarkPreauthReleased(ctx context.Context, db *sql.DB, txnReference string, releasedAt time.Time) error {
	const stmt = `
UPDATE dbo.Preauthorizations
SET Released = 1, ReleasedAt = @ReleasedAt
WHERE TxnReference = @TxnReference AND Released = 0;
`
	res, err := db.ExecContext(ctx, stmt, sql.Named("ReleasedAt", releasedAt), sql.Named("TxnReference", txnReference))
	if err != nil {
		return fmt.Errorf("MarkPreauthReleased exec: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("MarkPreauthReleased RowsAffected: %w", err)
	}
	if n == 0 {
		return fmt.Errorf("no rows updated for %s (maybe already released)", txnReference)
	}
	log.Infof("Marked preauth %s released at %s", txnReference, releasedAt.Format(time.RFC3339))
	return nil
}