1 files changed, 108 insertions, 8 deletions

diff --git a/api/graphql/connections/connections.go b/api/graphql/connections/connections.go
index bfdf8909..1ac2294f 100644
--- a/api/graphql/connections/connections.go
+++ b/api/graphql/connections/connections.go
@@ -1,11 +1,3 @@
-//go:generate genny -in=connection_template.go -out=gen_lazy_bug.go gen "Name=LazyBug NodeType=entity.Id EdgeType=LazyBugEdge ConnectionType=models.BugConnection"
-//go:generate genny -in=connection_template.go -out=gen_lazy_identity.go gen "Name=LazyIdentity NodeType=entity.Id EdgeType=LazyIdentityEdge ConnectionType=models.IdentityConnection"
-//go:generate genny -in=connection_template.go -out=gen_identity.go gen "Name=Identity NodeType=models.IdentityWrapper EdgeType=models.IdentityEdge ConnectionType=models.IdentityConnection"
-//go:generate genny -in=connection_template.go -out=gen_operation.go gen "Name=Operation NodeType=dag.Operation EdgeType=models.OperationEdge ConnectionType=models.OperationConnection"
-//go:generate genny -in=connection_template.go -out=gen_comment.go gen "Name=Comment NodeType=bug.Comment EdgeType=models.CommentEdge ConnectionType=models.CommentConnection"
-//go:generate genny -in=connection_template.go -out=gen_timeline.go gen "Name=TimelineItem NodeType=bug.TimelineItem EdgeType=models.TimelineItemEdge ConnectionType=models.TimelineItemConnection"
-//go:generate genny -in=connection_template.go -out=gen_label.go gen "Name=Label NodeType=bug.Label EdgeType=models.LabelEdge ConnectionType=models.LabelConnection"
-
 // Package connections implement a generic GraphQL relay connection
 package connections
 
@@ -14,6 +6,8 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+
+	"github.com/git-bug/git-bug/api/graphql/models"
 )
 
 const cursorPrefix = "cursor:"
@@ -43,3 +37,109 @@ func CursorToOffset(cursor string) (int, error) {
 	}
 	return offset, nil
 }
+
+// EdgeMaker defines a function that takes a NodeType and an offset and
+// create an Edge.
+type EdgeMaker[NodeType any] func(value NodeType, offset int) Edge
+
+// ConMaker defines a function that creates a ConnectionType
+type ConMaker[NodeType any, EdgeType Edge, ConType any] func(
+	edges []*EdgeType,
+	nodes []NodeType,
+	info *models.PageInfo,
+	totalCount int) (*ConType, error)
+
+// Connection will paginate a source according to the input of a relay connection
+func Connection[NodeType any, EdgeType Edge, ConType any](
+	source []NodeType,
+	edgeMaker EdgeMaker[NodeType],
+	conMaker ConMaker[NodeType, EdgeType, ConType],
+	input models.ConnectionInput) (*ConType, error) {
+
+	var nodes []NodeType
+	var edges []*EdgeType
+	var cursors []string
+	var pageInfo = &models.PageInfo{}
+	var totalCount = len(source)
+
+	emptyCon, _ := conMaker(edges, nodes, pageInfo, 0)
+
+	offset := 0
+
+	if input.After != nil {
+		for i, value := range source {
+			edge := edgeMaker(value, i)
+			if edge.GetCursor() == *input.After {
+				// remove all previous element including the "after" one
+				source = source[i+1:]
+				offset = i + 1
+				pageInfo.HasPreviousPage = true
+				break
+			}
+		}
+	}
+
+	if input.Before != nil {
+		for i, value := range source {
+			edge := edgeMaker(value, i+offset)
+
+			if edge.GetCursor() == *input.Before {
+				// remove all after element including the "before" one
+				pageInfo.HasNextPage = true
+				break
+			}
+
+			e := edge.(EdgeType)
+			edges = append(edges, &e)
+			cursors = append(cursors, edge.GetCursor())
+			nodes = append(nodes, value)
+		}
+	} else {
+		edges = make([]*EdgeType, len(source))
+		cursors = make([]string, len(source))
+		nodes = source
+
+		for i, value := range source {
+			edge := edgeMaker(value, i+offset)
+			e := edge.(EdgeType)
+			edges[i] = &e
+			cursors[i] = edge.GetCursor()
+		}
+	}
+
+	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]
+			cursors = cursors[:*input.First]
+			nodes = nodes[:*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:]
+			cursors = cursors[len(cursors)-*input.Last:]
+			nodes = nodes[len(nodes)-*input.Last:]
+			pageInfo.HasPreviousPage = true
+		}
+	}
+
+	// Fill up pageInfo cursors
+	if len(cursors) > 0 {
+		pageInfo.StartCursor = cursors[0]
+		pageInfo.EndCursor = cursors[len(cursors)-1]
+	}
+
+	return conMaker(edges, nodes, pageInfo, totalCount)
+}