package mailstore

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

	"github.com/jackc/pgx/v5/pgconn"
)

// pgUniqueViolationCode identifies the SQLSTATE returned by PostgreSQL when
// a UNIQUE constraint is violated by INSERT or UPDATE.
const pgUniqueViolationCode = "23505"

// isUniqueViolation reports whether err is a PostgreSQL unique-violation,
// regardless of constraint name.
func isUniqueViolation(err error) bool {
	var pgErr *pgconn.PgError
	if !errors.As(err, &pgErr) {
		return false
	}
	return pgErr.Code == pgUniqueViolationCode
}

// nullableTime returns t.UTC() when non-nil, otherwise nil for NULL columns.
func nullableTime(t *time.Time) any {
	if t == nil {
		return nil
	}
	return t.UTC()
}

// isNoRows reports whether err is sql.ErrNoRows.
func isNoRows(err error) bool {
	return errors.Is(err, sql.ErrNoRows)
}

// timeFromNullable copies an optional *time.Time read from Postgres into a
// new pointer normalised to UTC.
func timeFromNullable(value *time.Time) *time.Time {
	if value == nil {
		return nil
	}
	utc := value.UTC()
	return &utc
}

// withTimeout derives a child context bounded by timeout and prefixes context
// errors with operation. Callers must always invoke the returned cancel.
func withTimeout(ctx context.Context, operation string, timeout time.Duration) (context.Context, context.CancelFunc, error) {
	if ctx == nil {
		return nil, nil, fmt.Errorf("%s: nil context", operation)
	}
	if err := ctx.Err(); err != nil {
		return nil, nil, fmt.Errorf("%s: %w", operation, err)
	}
	if timeout <= 0 {
		return nil, nil, fmt.Errorf("%s: operation timeout must be positive", operation)
	}
	bounded, cancel := context.WithTimeout(ctx, timeout)
	return bounded, cancel, nil
}