package timeline

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

	"reanimator/internal/domain"
)

type EventRepository struct {
	db *sql.DB
}

func NewEventRepository(db *sql.DB) *EventRepository {
	return &EventRepository{db: db}
}

type Cursor struct {
	Time time.Time
	ID   int64
}

func EncodeCursor(cursor Cursor) string {
	return fmt.Sprintf("%d:%d", cursor.Time.UnixNano(), cursor.ID)
}

func DecodeCursor(value string) (Cursor, error) {
	parts := strings.Split(value, ":")
	if len(parts) != 2 {
		return Cursor{}, fmt.Errorf("invalid cursor")
	}
	ts, err := strconv.ParseInt(parts[0], 10, 64)
	if err != nil {
		return Cursor{}, fmt.Errorf("invalid cursor")
	}
	id, err := strconv.ParseInt(parts[1], 10, 64)
	if err != nil || id <= 0 {
		return Cursor{}, fmt.Errorf("invalid cursor")
	}
	return Cursor{Time: time.Unix(0, ts).UTC(), ID: id}, nil
}

func (r *EventRepository) List(ctx context.Context, subjectType string, subjectID int64, limit int, cursor *Cursor) ([]domain.TimelineEvent, *Cursor, error) {
	if limit <= 0 {
		limit = 50
	}
	if limit > 200 {
		limit = 200
	}

	args := []any{subjectType, subjectID}
	query := `
		SELECT id, subject_type, subject_id, event_type, event_time, asset_id, component_id, firmware_version, created_at
		FROM timeline_events
		WHERE subject_type = ? AND subject_id = ?`
	if cursor != nil {
		query += " AND (event_time > ? OR (event_time = ? AND id > ?))"
		args = append(args, cursor.Time, cursor.Time, cursor.ID)
	}
	query += " ORDER BY event_time, id LIMIT ?"
	args = append(args, limit+1)

	rows, err := r.db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, nil, err
	}
	defer rows.Close()

	events := make([]domain.TimelineEvent, 0)
	for rows.Next() {
		var event domain.TimelineEvent
		var assetID sql.NullInt64
		var componentID sql.NullInt64
		var firmware sql.NullString

		if err := rows.Scan(&event.ID, &event.SubjectType, &event.SubjectID, &event.EventType, &event.EventTime, &assetID, &componentID, &firmware, &event.CreatedAt); err != nil {
			return nil, nil, err
		}
		if assetID.Valid {
			event.AssetID = &assetID.Int64
		}
		if componentID.Valid {
			event.ComponentID = &componentID.Int64
		}
		if firmware.Valid {
			event.FirmwareVersion = &firmware.String
		}
		events = append(events, event)
	}
	if err := rows.Err(); err != nil {
		return nil, nil, err
	}

	var nextCursor *Cursor
	if len(events) > limit {
		last := events[limit-1]
		nextCursor = &Cursor{Time: last.EventTime.UTC(), ID: last.ID}
		events = events[:limit]
	}

	return events, nextCursor, nil
}