graphql: lazy loading for the bug relay connection

7 files changed, 77 insertions, 19 deletions

diff --git a/bug/bug.go b/bug/bug.go
index 713d6edc..d3cc41dd 100644
--- a/bug/bug.go
+++ b/bug/bug.go
@@ -204,6 +204,11 @@ func readAllBugs(repo repository.Repo, refPrefix string) <-chan StreamedBug {
 	return out
 }
 
+// List all the available local bug ids
+func ListLocalIds(repo repository.Repo) ([]string, error) {
+	return repo.ListIds(bugsRefPattern)
+}
+
 // IsValid check if the Bug data is valid
 func (bug *Bug) IsValid() bool {
 	// non-empty
diff --git a/cache/cache.go b/cache/cache.go
index 779b95b0..07c5be52 100644
--- a/cache/cache.go
+++ b/cache/cache.go
@@ -23,6 +23,7 @@ type Cacher interface {
 type RepoCacher interface {
 	ResolveBug(id string) (BugCacher, error)
 	ResolveBugPrefix(prefix string) (BugCacher, error)
+	AllBugIds() ([]string, error)
 	ClearAllBugs()
 }
 
@@ -155,6 +156,10 @@ func (c RepoCache) ResolveBugPrefix(prefix string) (BugCacher, error) {
 	return cached, nil
 }
 
+func (c RepoCache) AllBugIds() ([]string, error) {
+	return bug.ListLocalIds(c.repo)
+}
+
 func (c RepoCache) ClearAllBugs() {
 	c.bugs = make(map[string]BugCacher)
 }
diff --git a/graphql/connections/connection_template.go b/graphql/connections/connection_template.go
index 3dfaca8f..7f97c00b 100644
--- a/graphql/connections/connection_template.go
+++ b/graphql/connections/connection_template.go
@@ -11,13 +11,13 @@ 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
+type NodeTypeConMaker func(edges []EdgeType, info models.PageInfo, totalCount int) (ConnectionType, error)
 
 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)
+	emptyCon, _ := conMaker(edges, pageInfo, 0)
 
 	offset := 0
 
@@ -76,7 +76,5 @@ func NodeTypeCon(source []NodeType, edger NodeTypeEdger, conMaker NodeTypeConMak
 		}
 	}
 
-	con := conMaker(edges, pageInfo, len(source))
-
-	return con, nil
+	return conMaker(edges, pageInfo, len(source))
 }
diff --git a/graphql/connections/connections.go b/graphql/connections/connections.go
index 145bfbbe..84dc3750 100644
--- a/graphql/connections/connections.go
+++ b/graphql/connections/connections.go
@@ -1,4 +1,4 @@
-//go:generate genny -in=connection_template.go -out=gen_bug.go gen "NodeType=bug.Snapshot EdgeType=models.BugEdge ConnectionType=models.BugConnection"
+//go:generate genny -in=connection_template.go -out=gen_bug.go gen "NodeType=string EdgeType=LazyBugEdge ConnectionType=models.BugConnection"
 //go:generate genny -in=connection_template.go -out=gen_operation.go gen "NodeType=bug.Operation EdgeType=models.OperationEdge ConnectionType=models.OperationConnection"
 //go:generate genny -in=connection_template.go -out=gen_comment.go gen "NodeType=bug.Comment EdgeType=models.CommentEdge ConnectionType=models.CommentConnection"
 
diff --git a/graphql/connections/gen_bug.go b/graphql/connections/gen_bug.go
index b43d5c11..64458669 100644
--- a/graphql/connections/gen_bug.go
+++ b/graphql/connections/gen_bug.go
@@ -7,18 +7,17 @@ package connections
 import (
 	"fmt"
 
-	"github.com/MichaelMure/git-bug/bug"
 	"github.com/MichaelMure/git-bug/graphql/models"
 )
 
-type BugSnapshotEdger func(value bug.Snapshot, offset int) Edge
-type BugSnapshotConMaker func(edges []models.BugEdge, info models.PageInfo, totalCount int) models.BugConnection
+type StringEdger func(value string, offset int) Edge
+type StringConMaker func(edges []LazyBugEdge, info models.PageInfo, totalCount int) (models.BugConnection, error)
 
-func BugSnapshotCon(source []bug.Snapshot, edger BugSnapshotEdger, conMaker BugSnapshotConMaker, input models.ConnectionInput) (models.BugConnection, error) {
-	var edges []models.BugEdge
+func StringCon(source []string, edger StringEdger, conMaker StringConMaker, input models.ConnectionInput) (models.BugConnection, error) {
+	var edges []LazyBugEdge
 	var pageInfo models.PageInfo
 
-	emptyCon := conMaker(edges, pageInfo, 0)
+	emptyCon, _ := conMaker(edges, pageInfo, 0)
 
 	offset := 0
 
@@ -43,13 +42,13 @@ func BugSnapshotCon(source []bug.Snapshot, edger BugSnapshotEdger, conMaker BugS
 				break
 			}
 
-			edges = append(edges, edge.(models.BugEdge))
+			edges = append(edges, edge.(LazyBugEdge))
 		}
 	} else {
-		edges = make([]models.BugEdge, len(source))
+		edges = make([]LazyBugEdge, len(source))
 
 		for i, value := range source {
-			edges[i] = edger(value, i+offset).(models.BugEdge)
+			edges[i] = edger(value, i+offset).(LazyBugEdge)
 		}
 	}
 
@@ -77,7 +76,5 @@ func BugSnapshotCon(source []bug.Snapshot, edger BugSnapshotEdger, conMaker BugS
 		}
 	}
 
-	con := conMaker(edges, pageInfo, len(source))
-
-	return con, nil
+	return conMaker(edges, pageInfo, len(source))
 }
diff --git a/graphql/connections/lazy_bug.go b/graphql/connections/lazy_bug.go
new file mode 100644
index 00000000..35dcb687
--- /dev/null
+++ b/graphql/connections/lazy_bug.go
@@ -0,0 +1,10 @@
+package connections
+
+type LazyBugEdge struct {
+	Id     string
+	Cursor string
+}
+
+func (lbe LazyBugEdge) GetCursor() string {
+	return lbe.Cursor
+}
diff --git a/graphql/resolvers/repo.go b/graphql/resolvers/repo.go
index d8190f15..2031d7b6 100644
--- a/graphql/resolvers/repo.go
+++ b/graphql/resolvers/repo.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"github.com/MichaelMure/git-bug/bug"
 	"github.com/MichaelMure/git-bug/cache"
+	"github.com/MichaelMure/git-bug/graphql/connections"
 	"github.com/MichaelMure/git-bug/graphql/models"
 )
 
@@ -13,7 +14,49 @@ type repoResolver struct {
 }
 
 func (repoResolver) AllBugs(ctx context.Context, obj *repoResolver, input models.ConnectionInput) (models.BugConnection, error) {
-	panic("implement me")
+
+	// Simply pass a []string with the ids to the pagination algorithm
+	source, err := obj.repo.AllBugIds()
+
+	if err != nil {
+		return models.BugConnection{}, err
+	}
+
+	// The edger create a custom edge holding just the id
+	edger := func(id string, offset int) connections.Edge {
+		return connections.LazyBugEdge{
+			Id:     id,
+			Cursor: connections.OffsetToCursor(offset),
+		}
+	}
+
+	// The conMaker will finally load and compile bugs from git to replace the selected edges
+	conMaker := func(lazyBugEdges []connections.LazyBugEdge, info models.PageInfo, totalCount int) (models.BugConnection, error) {
+		edges := make([]models.BugEdge, len(lazyBugEdges))
+
+		for i, lazyBugEdge := range lazyBugEdges {
+			b, err := obj.repo.ResolveBug(lazyBugEdge.Id)
+
+			if err != nil {
+				return models.BugConnection{}, err
+			}
+
+			snap := b.Snapshot()
+
+			edges[i] = models.BugEdge{
+				Cursor: lazyBugEdge.Cursor,
+				Node:   *snap,
+			}
+		}
+
+		return models.BugConnection{
+			Edges:      edges,
+			PageInfo:   info,
+			TotalCount: totalCount,
+		}, nil
+	}
+
+	return connections.StringCon(source, edger, conMaker, input)
 }
 
 func (repoResolver) Bug(ctx context.Context, obj *repoResolver, prefix string) (*bug.Snapshot, error) {