package mongoext

import (
	"context"
	"go.mongodb.org/mongo-driver/mongo"
	"gogs.mikescher.com/BlackForestBytes/goext/rfctime"
	"inopart/backend/common/cursortoken"
	"inopart/backend/models"
)

func HandleMongoCursorWithToken[T models.Entity](ctx context.Context, cursor *mongo.Cursor, pageSize *int) ([]T, string, error) {
	var tokenStr string
	var docs []T
	numDocs := cursor.RemainingBatchLength()

	if pageSize == nil || (numDocs <= *pageSize) && numDocs > 0 {
		docs = make([]T, numDocs)

		err := cursor.All(ctx, &docs)
		if err != nil {
			return []T{}, "", err
		}

	} else if numDocs == *pageSize+1 {

		docs = make([]T, numDocs-1)

		for i := 0; i < numDocs-1; i++ {
			cursor.Next(ctx)
			err := cursor.Decode(&docs[i])
			if err != nil {
				return []T{}, "", err
			}
		}

		var nextPageDoc T
		cursor.Next(ctx)
		err := cursor.Decode(&nextPageDoc)
		if err != nil {
			return []T{}, "", err
		}

		nextPageToken := cursortoken.CursorToken{
			Timestamp: rfctime.RFC3339NanoTime{},
			Id:        nextPageDoc.GetId(),
			Offset:    0,
			PageSize:  *pageSize,
		}

		tokenStr, err = nextPageToken.Token()
		if err != nil {
			return nil, "", err
		}
	}

	return docs, tokenStr, nil
}