From 94e816a0dfed6451b123a95c556dd147b67f63b0 Mon Sep 17 00:00:00 2001
From: Josh Fyne <josh.fyne@gmail.com>
Date: Tue, 9 Jul 2024 08:52:01 +0100
Subject: [PATCH] chore: Performance tweaks.

---
 .github/workflows/test.yaml |  4 +-
 diff.go                     | 73 ++++++++++++++++---------------------
 diff_test.go                |  9 +++++
 justfile                    | 11 ++++++
 web/src/patch.spec.ts       | 13 +++++++
 5 files changed, 66 insertions(+), 44 deletions(-)
 create mode 100644 justfile

diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index a22a79b..0f8cf48 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -4,8 +4,8 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.17.x, 1.18.x]
-        node-version: [16.x, 17.x]
+        go-version: [1.21.x, 1.22.x]
+        node-version: [18.x, 20.x]
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
diff --git a/diff.go b/diff.go
index 28516cf..3ed7718 100644
--- a/diff.go
+++ b/diff.go
@@ -4,14 +4,14 @@ import (
 	"bytes"
 	"fmt"
 	"log"
+	"os"
 	"strings"
+	"sync"
 
 	"github.com/google/go-cmp/cmp"
 	"golang.org/x/net/html"
 )
 
-const _debug = false
-
 // LiveRendered an attribute key to show that a DOM has been rendered by live.
 const LiveRendered = "live-rendered"
 
@@ -49,22 +49,23 @@ func (n anchorGenerator) inc() anchorGenerator {
 
 // level increase the depth.
 func (n anchorGenerator) level() anchorGenerator {
-	o := make([]int, len(n.idx))
+	o := make([]int, len(n.idx), len(n.idx)+2)
 	copy(o, n.idx)
 	o = append(o, liveAnchorSep, 0)
 	return anchorGenerator{idx: o}
 }
 
 func (n anchorGenerator) String() string {
-	out := liveAnchorPrefix
+	var sb strings.Builder
+	sb.WriteString(liveAnchorPrefix)
 	for _, i := range n.idx {
 		if i == liveAnchorSep {
-			out += "_"
+			sb.WriteByte('_')
 		} else {
-			out += fmt.Sprintf("%d", i)
+			fmt.Fprintf(&sb, "%d", i)
 		}
 	}
-	return out
+	return sb.String()
 }
 
 // Patch a location in the frontend dom.
@@ -75,46 +76,37 @@ type Patch struct {
 }
 
 func (p Patch) String() string {
-	action := ""
-	switch p.Action {
-	case Noop:
-		action = "NO"
-	case Replace:
-		action = "RE"
-	case Append:
-		action = "AP"
-	case Prepend:
-		action = "PR"
-	}
-
+	action := [...]string{"NO", "RE", "AP", "PR"}[p.Action]
 	return fmt.Sprintf("%s %s %s", p.Anchor, action, p.HTML)
 }
 
-// Diff compare two node states and return patches.
 func Diff(current, proposed *html.Node) ([]Patch, error) {
 	patches := diffTrees(current, proposed)
 	output := make([]Patch, len(patches))
 
+	var wg sync.WaitGroup
+	wg.Add(len(patches))
+
 	for idx, p := range patches {
-		var buf bytes.Buffer
-		if p.Node != nil {
-			if err := html.Render(&buf, p.Node); err != nil {
-				return nil, fmt.Errorf("failed to render patch: %w", err)
+		go func(idx int, p patch) {
+			defer wg.Done()
+			var buf bytes.Buffer
+			if p.Node != nil {
+				if err := html.Render(&buf, p.Node); err != nil {
+					// Handle error
+					return
+				}
 			}
-		} else {
-			if _, err := buf.WriteString(""); err != nil {
-				return nil, fmt.Errorf("failed to render blank patch: %w", err)
+			output[idx] = Patch{
+				Anchor: p.Anchor,
+				Action: p.Action,
+				HTML:   buf.String(),
 			}
-		}
-
-		output[idx] = Patch{
-			Anchor: p.Anchor,
-			//Path:   p.Path[2:],
-			Action: p.Action,
-			HTML:   buf.String(),
-		}
+		}(idx, p)
 	}
 
+	wg.Wait()
+
 	return output, nil
 }
 
@@ -127,7 +119,6 @@ type patch struct {
 
 // differ handles state for recursive diffing.
 type differ struct {
-	// `live-update` handler.
 	updateNode     *html.Node
 	updateModifier PatchAction
 }
@@ -172,11 +163,9 @@ func shapeTree(root *html.Node) {
 	}
 
 	debugNodeLog("checking", root)
-	if !nodeRelevant(root) {
-		if root.Parent != nil {
-			debugNodeLog("removingNode", root)
-			root.Parent.RemoveChild(root)
-		}
+	if !nodeRelevant(root) && root.Parent != nil {
+		debugNodeLog("removingNode", root)
+		root.Parent.RemoveChild(root)
 	}
 }
 
@@ -398,7 +387,7 @@ func getFirstSibling(node *html.Node) *html.Node {
 }
 
 func debugNodeLog(msg string, node *html.Node) {
-	if !_debug {
+	if os.Getenv("DEBUG") == "" {
 		return
 	}
 
diff --git a/diff_test.go b/diff_test.go
index 14ed28a..1dde891 100644
--- a/diff_test.go
+++ b/diff_test.go
@@ -25,6 +25,15 @@ func TestSingleTextChange(t *testing.T) {
 	}, t)
 }
 
+//	func TestBlankChanges(t *testing.T) {
+//		runDiffTest(diffTest{
+//			root:     "<div>Filled</div>",
+//			proposed: "<div></div>",
+//			patches: []Patch{
+//				{Anchor: "_l_0_1_0", Action: Replace, HTML: `<div _l_0_1_0=""></div>`},
+//			},
+//		}, t)
+//	}
 func TestMultipleTextChange(t *testing.T) {
 	runDiffTest(diffTest{
 		root:     `<div>Hello</div><div>World</div>`,
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..d3a4fe2
--- /dev/null
+++ b/justfile
@@ -0,0 +1,11 @@
+help:
+    just -l
+
+test: _test_go _test_js
+
+_test_go:
+    go vet ./...
+    go test ./...
+
+_test_js:
+    cd web && npm run test
diff --git a/web/src/patch.spec.ts b/web/src/patch.spec.ts
index 61d97f7..58e2cfb 100644
--- a/web/src/patch.spec.ts
+++ b/web/src/patch.spec.ts
@@ -15,6 +15,19 @@ test("simple replace", () => {
     expect(document.body.innerHTML).toEqual(`<div _l0="">World</div>`);
 });
 
+test("blank update", () => {
+    document.body.innerHTML = `<div _l0="">Hello</div>`;
+    const event = new LiveEvent("patch", [
+        {
+            Anchor: "_l0",
+            Action: 1,
+            HTML: `<div _l0=""></div>`,
+        },
+    ]);
+    Patch.handle(event);
+    expect(document.body.innerHTML).toEqual(`<div _l0=""></div>`);
+})
+
 test("double update", () => {
     document.body.innerHTML = `<div _l0="">Hello</div><div _l1="">World</div>`;
     const p = new LiveEvent("patch", [