From e4e734f3dd6b47587d368c055648d42ecb71a1cb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mickae=CC=88l=20Menu?= <mickael.menu@gmail.com>
Date: Fri, 29 Jan 2021 20:40:06 +0100
Subject: [PATCH] Add --orphan filtering flag

---
 adapter/sqlite/note_dao.go      | 5 +++++
 adapter/sqlite/note_dao_test.go | 9 +++++++++
 cmd/finder_opts.go              | 5 +++++
 core/note/find.go               | 4 ++++
 4 files changed, 23 insertions(+)

diff --git a/adapter/sqlite/note_dao.go b/adapter/sqlite/note_dao.go
index 49e270a..8b2f4f9 100644
--- a/adapter/sqlite/note_dao.go
+++ b/adapter/sqlite/note_dao.go
@@ -410,6 +410,11 @@ func (d *NoteDAO) findRows(opts note.FinderOpts) (*sql.Rows, error) {
 
 			whereExprs = append(whereExprs, expr)
 
+		case note.OrphanFilter:
+			whereExprs = append(whereExprs, `n.id NOT IN (
+				SELECT target_id FROM links WHERE target_id IS NOT NULL
+			)`)
+
 		case note.DateFilter:
 			value := "?"
 			field := "n." + dateField(filter)
diff --git a/adapter/sqlite/note_dao_test.go b/adapter/sqlite/note_dao_test.go
index 53c249d..681bb16 100644
--- a/adapter/sqlite/note_dao_test.go
+++ b/adapter/sqlite/note_dao_test.go
@@ -527,6 +527,15 @@ func TestNoteDAOFindNotLinkingTo(t *testing.T) {
 	)
 }
 
+func TestNoteDAOFindOrphan(t *testing.T) {
+	testNoteDAOFindPaths(t,
+		note.FinderOpts{
+			Filters: []note.Filter{note.OrphanFilter{}},
+		},
+		[]string{"ref/test/b.md", "f39c8.md", "log/2021-02-04.md", "index.md"},
+	)
+}
+
 func TestNoteDAOFindCreatedOn(t *testing.T) {
 	testNoteDAOFindPaths(t,
 		note.FinderOpts{
diff --git a/cmd/finder_opts.go b/cmd/finder_opts.go
index cbda819..0f74231 100644
--- a/cmd/finder_opts.go
+++ b/cmd/finder_opts.go
@@ -23,6 +23,7 @@ type Filtering struct {
 	LinkingTo      []string `help:"Only the notes linking to the given notes" placeholder:"<path>" short:"L"`
 	NotLinkedBy    []string `help:"Only the notes not linked by the given notes" placeholder:"<path>"`
 	NotLinkingTo   []string `help:"Only the notes not linking to the given notes" placeholder:"<path>"`
+	Orphan         bool     `help:"Only the notes which don't have any other note linking to them"`
 	Exclude        []string `help:"Excludes notes matching the given file path pattern from the list" short:"x" placeholder:"<glob>"`
 	Interactive    bool     `help:"Further filter the list of notes interactively" short:"i"`
 }
@@ -154,6 +155,10 @@ func NewFinderOpts(zk *zk.Zk, filtering Filtering, sorting Sorting) (*note.Finde
 		})
 	}
 
+	if filtering.Orphan {
+		filters = append(filters, note.OrphanFilter{})
+	}
+
 	if filtering.Interactive {
 		filters = append(filters, note.InteractiveFilter(true))
 	}
diff --git a/core/note/find.go b/core/note/find.go
index 8e7f65c..97e388d 100644
--- a/core/note/find.go
+++ b/core/note/find.go
@@ -52,6 +52,9 @@ type LinkingToFilter struct {
 	Negate bool
 }
 
+// OrphanFilter is a note filter used to select notes having no other notes linking to them.
+type OrphanFilter struct{}
+
 // DateFilter can be used to filter notes created or modified before, after or on a given date.
 type DateFilter struct {
 	Date      time.Time
@@ -67,6 +70,7 @@ func (f PathFilter) sealed()        {}
 func (f ExcludePathFilter) sealed() {}
 func (f LinkedByFilter) sealed()    {}
 func (f LinkingToFilter) sealed()   {}
+func (f OrphanFilter) sealed()      {}
 func (f DateFilter) sealed()        {}
 func (f InteractiveFilter) sealed() {}