package checkin

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

// UserEvent is an event a user has checked into, enriched with event metadata.
type UserEvent struct {
	EventURI    string
	EventName   string
	Location    string
	StartTime   time.Time
	EndTime     time.Time
	CheckedInAt time.Time
	IsOngoing   bool
}

// ListForUser returns all events a user has checked into, most recent first.
// Each event appears once (even if the user checked in multiple times).
// did can be an ATProto DID ("did:plc:...") or a local ID ("local_...").
func ListForUser(ctx context.Context, db *sql.DB, did string, now time.Time) ([]UserEvent, error) {
	rows, err := db.QueryContext(ctx, `
		SELECT e.uri, e.name, e.location, e.start_time, e.end_time,
		       MAX(c.checked_in_at) AS last_checkin
		FROM checkins c
		JOIN events e ON e.uri = c.event_uri
		WHERE c.did = ?
		GROUP BY e.uri
		ORDER BY last_checkin DESC
	`, did)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []UserEvent
	for rows.Next() {
		var ue UserEvent
		var checkedInAtStr string
		if err := rows.Scan(&ue.EventURI, &ue.EventName, &ue.Location,
			&ue.StartTime, &ue.EndTime, &checkedInAtStr); err != nil {
			return nil, err
		}
		ue.CheckedInAt, _ = time.Parse(time.RFC3339, checkedInAtStr)
		if ue.CheckedInAt.IsZero() {
			ue.CheckedInAt, _ = time.Parse("2006-01-02 15:04:05", checkedInAtStr)
		}
		ue.IsOngoing = !now.Before(ue.StartTime) && !now.After(ue.EndTime)
		out = append(out, ue)
	}
	return out, rows.Err()
}

// ListAttendeesForEvent returns distinct DIDs of users who checked into a
// specific event, ordered by check-in time (earliest first).
func ListAttendeesForEvent(ctx context.Context, db *sql.DB, eventURI string) ([]string, error) {
	rows, err := db.QueryContext(ctx, `
		SELECT did
		FROM checkins
		WHERE event_uri = ?
		GROUP BY did
		ORDER BY MIN(checked_in_at) ASC
	`, eventURI)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []string
	for rows.Next() {
		var did string
		if err := rows.Scan(&did); err != nil {
			return nil, err
		}
		out = append(out, did)
	}
	return out, rows.Err()
}