From a72a2a5f7410d3350909494aba964088c23ffa2e Mon Sep 17 00:00:00 2001
From: Peter Stuifzand <peter.stuifzand@gmail.com>
Date: Sat, 10 Jul 2021 10:50:35 +0200
Subject: [PATCH] LSP references to browse the backlinks of the link under the
 caret (#58)

---
 CHANGELOG.md                   |  1 +
 internal/adapter/lsp/server.go | 67 ++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b24ae06..c892bd8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ All notable changes to this project will be documented in this file.
     * `{{json title}}` prints with quotes `"An interesting note"`
     * `{{json .}}` serializes the full template context as a JSON object.
 * Use `--header` and `--footer` options with `zk list` to print arbitrary text at the start or end of the list.
+* Support for LSP references to browse the backlinks of the link under the caret (contributed by [@pstuifzand](https://github.com/mickael-menu/zk/pull/58)).
 
 ### Fixed
 
diff --git a/internal/adapter/lsp/server.go b/internal/adapter/lsp/server.go
index e07ec0c..c139525 100644
--- a/internal/adapter/lsp/server.go
+++ b/internal/adapter/lsp/server.go
@@ -104,6 +104,8 @@ func NewServer(opts ServerOpts) *Server {
 			ResolveProvider:   boolPtr(true),
 		}
 
+		capabilities.ReferencesProvider = &protocol.ReferenceOptions{}
+
 		return protocol.InitializeResult{
 			Capabilities: capabilities,
 			ServerInfo: &protocol.InitializeResultServerInfo{
@@ -389,6 +391,71 @@ func NewServer(opts ServerOpts) *Server {
 		return actions, nil
 	}
 
+	handler.TextDocumentReferences = func(context *glsp.Context, params *protocol.ReferenceParams) ([]protocol.Location, error) {
+		doc, ok := server.documents.Get(params.TextDocument.URI)
+		if !ok {
+			return nil, nil
+		}
+
+		link, err := doc.DocumentLinkAt(params.Position)
+		if link == nil || err != nil {
+			return nil, err
+		}
+
+		notebook, err := server.notebookOf(doc)
+		if err != nil {
+			return nil, err
+		}
+
+		target, err := server.noteForHref(link.Href, doc, notebook)
+		if link == nil || target == nil || err != nil {
+			return nil, err
+		}
+
+		p, err := notebook.RelPath(target.Path)
+		if err != nil {
+			return nil, err
+		}
+
+		opts := core.NoteFindOpts{
+			LinkTo: &core.LinkFilter{Paths: []string{p}},
+		}
+
+		notes, err := notebook.FindNotes(opts)
+		if err != nil {
+			return nil, err
+		}
+
+		var locations []protocol.Location
+
+		for _, note := range notes {
+			pos := strings.Index(note.RawContent, target.Path[0:len(target.Path)-3])
+			var line uint32 = 0
+			if pos < 0 {
+				line = 0
+			} else {
+				linePos := strings.Count(note.RawContent[0:pos], "\n")
+				line = uint32(linePos)
+			}
+
+			locations = append(locations, protocol.Location{
+				URI: pathToURI(filepath.Join(notebook.Path, note.Path)),
+				Range: protocol.Range{
+					Start: protocol.Position{
+						Line:      line,
+						Character: 0,
+					},
+					End: protocol.Position{
+						Line:      line,
+						Character: 0,
+					},
+				},
+			})
+		}
+
+		return locations, nil
+	}
+
 	return server
 }