package store

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

// OutboxEvent is the durable hand-off between a committed domain mutation and
// transient WebSocket delivery. Consumers must make delivery idempotent by
// event ID and only acknowledge after successful fan-out.
type OutboxEvent struct {
	EventID       string
	AggregateType string
	AggregateID   string
	Revision      uint64
	EventType     string
	Payload       []byte
	CreatedAt     time.Time
	PublishedAt   *time.Time
}

const OutboxUnpublishedSelectSQL = `SELECT event_id, aggregate_type, aggregate_id, revision,
    event_type, payload, created_at, published_at
FROM outbox
WHERE published_at IS NULL
ORDER BY created_at, event_id
LIMIT $1`

const OutboxMarkPublishedSQL = `UPDATE outbox
SET published_at = $2
WHERE event_id = $1 AND published_at IS NULL`

var ErrOutboxEventNotFound = fmt.Errorf("outbox event not found or already published")

// ReadUnpublishedOutbox returns a bounded, stable ordered batch. It does not
// mark rows before delivery: a worker crash therefore leaves events replayable.
func ReadUnpublishedOutbox(ctx context.Context, db *sql.DB, limit int) ([]OutboxEvent, error) {
	if db == nil || limit < 1 || limit > 1000 {
		return nil, fmt.Errorf("invalid outbox read arguments")
	}
	rows, err := db.QueryContext(ctx, OutboxUnpublishedSelectSQL, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	events := make([]OutboxEvent, 0, limit)
	for rows.Next() {
		var event OutboxEvent
		if err := rows.Scan(&event.EventID, &event.AggregateType, &event.AggregateID, &event.Revision, &event.EventType, &event.Payload, &event.CreatedAt, &event.PublishedAt); err != nil {
			return nil, err
		}
		events = append(events, event)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return events, nil
}

// MarkOutboxPublished acknowledges one event only if it is still unpublished.
// Repeated acknowledgement is reported to the caller so a worker cannot
// mistake an already-completed delivery for a fresh one.
func MarkOutboxPublished(ctx context.Context, db *sql.DB, eventID string, publishedAt time.Time) error {
	if db == nil || eventID == "" || publishedAt.IsZero() {
		return fmt.Errorf("invalid outbox acknowledgement arguments")
	}
	result, err := db.ExecContext(ctx, OutboxMarkPublishedSQL, eventID, publishedAt)
	if err != nil {
		return err
	}
	changed, err := result.RowsAffected()
	if err != nil {
		return err
	}
	if changed != 1 {
		return ErrOutboxEventNotFound
	}
	return nil
}