Product/graphql/helper/collection.go

package helper

import (
	"fmt"
	"github.com/gshopify/service-wrapper/fun"
	"github.com/gshopify/service-wrapper/model"
	"gshopper.com/gshopify/products/graphql/generated"
)

func NewCollectionConnection(src []*generated.Collection,
	after *string, before *string, first *int, last *int, reverse *bool) (*generated.CollectionConnection, error) {
	var (
		connection = &generated.CollectionConnection{}
		err        error
	)

	if len(src) == 0 {
		return connection, nil
	}

	if reverse != nil && *reverse {
		src = fun.Reverse(src)
	}

	connection.Nodes = src[:]
	connection.Nodes = fun.First(connection.Nodes, first)
	connection.Nodes = fun.Last(connection.Nodes, last)

	if connection.Nodes, err = fun.WithCursor(connection.Nodes, after, model.GidCollection, true); err != nil {
		return nil, fmt.Errorf("illegal cursor: %s", *after)
	}

	if connection.Nodes, err = fun.WithCursor(connection.Nodes, before, model.GidCollection, false); err != nil {
		return nil, fmt.Errorf("illegal cursor: %s", *before)
	}

	connection.PageInfo = NewPageInfo(connection.Nodes, model.GidCollection, src[0], src[len(src)-1])

	// Edges
	for i := range connection.Nodes {
		e := &generated.CollectionEdge{
			Node: connection.Nodes[i],
		}

		if c, err := model.NewSimpleCursor(e.Node.ID, model.GidCollection); err == nil {
			e.Cursor = *c.String()
		}

		connection.Edges = append(connection.Edges, e)
	}

	return connection, nil
}