graphql: directly return a connection, cleaning

1 files changed, 82 insertions, 0 deletions

diff --git a/graphql/connections/connection_template.go b/graphql/connections/connection_template.go
new file mode 100644
index 00000000..3dfaca8f
--- /dev/null
+++ b/graphql/connections/connection_template.go
@@ -0,0 +1,82 @@
+package connections
+
+import (
+	"fmt"
+	"github.com/MichaelMure/git-bug/graphql/models"
+	"github.com/cheekybits/genny/generic"
+)
+
+type NodeType generic.Type
+type EdgeType generic.Type
+type ConnectionType generic.Type
+
+type NodeTypeEdger func(value NodeType, offset int) Edge
+type NodeTypeConMaker func(edges []EdgeType, info models.PageInfo, totalCount int) ConnectionType
+
+func NodeTypeCon(source []NodeType, edger NodeTypeEdger, conMaker NodeTypeConMaker, input models.ConnectionInput) (ConnectionType, error) {
+	var edges []EdgeType
+	var pageInfo models.PageInfo
+
+	emptyCon := conMaker(edges, pageInfo, 0)
+
+	offset := 0
+
+	if input.After != nil {
+		for i, value := range source {
+			edge := edger(value, i)
+			if edge.GetCursor() == *input.After {
+				// remove all previous element including the "after" one
+				source = source[i+1:]
+				offset = i + 1
+				break
+			}
+		}
+	}
+
+	if input.Before != nil {
+		for i, value := range source {
+			edge := edger(value, i+offset)
+
+			if edge.GetCursor() == *input.Before {
+				// remove all after element including the "before" one
+				break
+			}
+
+			edges = append(edges, edge.(EdgeType))
+		}
+	} else {
+		edges = make([]EdgeType, len(source))
+
+		for i, value := range source {
+			edges[i] = edger(value, i+offset).(EdgeType)
+		}
+	}
+
+	if input.First != nil {
+		if *input.First < 0 {
+			return emptyCon, fmt.Errorf("first less than zero")
+		}
+
+		if len(edges) > *input.First {
+			// Slice result to be of length first by removing edges from the end
+			edges = edges[:*input.First]
+			pageInfo.HasNextPage = true
+		}
+	}
+
+	if input.Last != nil {
+		if *input.Last < 0 {
+			return emptyCon, fmt.Errorf("last less than zero")
+		}
+
+		if len(edges) > *input.Last {
+			// Slice result to be of length last by removing edges from the start
+			edges = edges[len(edges)-*input.Last:]
+			pageInfo.HasPreviousPage = true
+		}
+	}
+
+	con := conMaker(edges, pageInfo, len(source))
+
+	return con, nil
+}