Allow editing of individual sections

CLAUDE.md

@@ -54,6 +54,8 @@ Prefer separate, human-readable `.html` files over inlined HTML strings in Go. E
 - Do not inline JS in templates or merge unrelated features into one file
 - `ALT+SHIFT` is the modifier for all keyboard shortcuts — do not introduce others
 - Editor toolbar buttons use `data-action` + `data-key`; adding `data-key` auto-registers the shortcut
+- Prefer generic, descriptive CSS classes (`btn`, `btn-small`, `muted`, `danger`) over element-specific names (`save-button`, `cancel-button`, `form-name-input`). Use a modifier + base class pattern (`btn btn-small`) rather than one-off classes that duplicate shared styles.
+- Where possible, re-use existing CSS classes
 
 ## Development Priorities
 

assets/page.html

@@ -26,6 +26,7 @@
         <main>
             {{if .EditMode}}
             <form id="edit-form" class="edit-form" method="POST" action="{{.PostURL}}">
+                {{if ge .SectionIndex 0}}<input type="hidden" name="section" value="{{.SectionIndex}}">{{end}}
                 <div class="editor-toolbar">
                     <button type="button" class="btn btn-tool" data-action="bold"      data-key="B" title="Bold (B)">**</button>
                     <button type="button" class="btn btn-tool" data-action="italic"    data-key="I" title="Italic (I)">*</button>
@@ -62,6 +63,9 @@
             {{if or .Content .SpecialContent}}
             <script src="/_/content.js"></script>
             {{end}}
+            {{if .Content}}
+            <script src="/_/sections.js"></script>
+            {{end}}
             {{if .Entries}}
             <div class="listing">
                 <div class="listing-header">Contents</div>

assets/sections.js

@@ -0,0 +1,16 @@
+(function () {
+    var content = document.querySelector('.content');
+    if (!content) return;
+    var headings = content.querySelectorAll('h1, h2, h3, h4, h5, h6');
+    if (!headings.length) return;
+
+    // Section 0 is pre-heading content, editable via full-page edit.
+    // Sections 1..N each start at a heading; that is the index sent to the server.
+    headings.forEach(function (h, i) {
+        var a = document.createElement('a');
+        a.href = '?edit&section=' + (i + 1);
+        a.className = 'btn btn-small section-edit';
+        a.textContent = 'edit';
+        h.appendChild(a);
+    });
+}());

assets/style.css

@@ -104,6 +104,13 @@ header {
     color: #ffd54f;
 }
 
+/* === Button modifiers === */
+.btn-small {
+    font-size: 0.65rem;
+    font-weight: normal;
+    vertical-align: middle;
+}
+
 /* === Main === */
 main {
     max-width: 860px;
@@ -331,7 +338,6 @@ textarea:focus {
     box-shadow: 0 0 5px #0a0;
 }
 
-
 /* === Diary views === */
 .diary-section {
     margin: 2rem 0;
@@ -380,6 +386,11 @@ textarea:focus {
     margin-bottom: 0.75rem;
 }
 
+/* === Section edit links === */
+.section-edit {
+    margin-left: 0.75rem;
+}
+
 /* === Empty state === */
 .empty {
     padding: 1rem;

main.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 	"strings"
 )
 
@@ -123,6 +124,16 @@ func (h *handler) serveDir(w http.ResponseWriter, r *http.Request, urlPath, fsPa
 	indexPath := filepath.Join(fsPath, "index.md")
 	rawMD, _ := os.ReadFile(indexPath)
 
+	// Determine section index (-1 = whole page).
+	sectionIndex := -1
+	if editMode {
+		if s := r.URL.Query().Get("section"); s != "" {
+			if n, err := strconv.Atoi(s); err == nil && n >= 0 {
+				sectionIndex = n
+			}
+		}
+	}
+
 	var rendered template.HTML
 	if len(rawMD) > 0 && !editMode {
 		rendered = renderMarkdown(rawMD)
@@ -152,13 +163,22 @@ func (h *handler) serveDir(w http.ResponseWriter, r *http.Request, urlPath, fsPa
 		specialContent = special.Content
 	}
 
+	rawContent := string(rawMD)
+	if editMode && sectionIndex >= 0 {
+		sections := splitSections(rawMD)
+		if sectionIndex < len(sections) {
+			rawContent = string(sections[sectionIndex])
+		}
+	}
+
 	data := pageData{
 		Title:          title,
 		Crumbs:         buildCrumbs(urlPath),
 		CanEdit:        true,
 		EditMode:       editMode,
+		SectionIndex:   sectionIndex,
 		PostURL:        urlPath,
-		RawContent:     string(rawMD),
+		RawContent:     rawContent,
 		Content:        rendered,
 		Entries:        entries,
 		SpecialContent: specialContent,
@@ -177,6 +197,23 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 	}
 	content := r.FormValue("content")
 	indexPath := filepath.Join(fsPath, "index.md")
+
+	// If a section index was submitted, splice the edited section back into
+	// the full file rather than replacing the whole document.
+	if s := r.FormValue("section"); s != "" {
+		sectionIndex, err := strconv.Atoi(s)
+		if err != nil || sectionIndex < 0 {
+			http.Error(w, "bad section", http.StatusBadRequest)
+			return
+		}
+		rawMD, _ := os.ReadFile(indexPath)
+		sections := splitSections(rawMD)
+		if sectionIndex < len(sections) {
+			sections[sectionIndex] = []byte(content)
+		}
+		content = string(joinSections(sections))
+	}
+
 	if strings.TrimSpace(content) == "" {
 		if err := os.Remove(indexPath); err != nil && !os.IsNotExist(err) {
 			http.Error(w, "delete failed: "+err.Error(), http.StatusInternalServerError)

render.go

@@ -32,6 +32,7 @@ type pageData struct {
 	Crumbs         []crumb
 	CanEdit        bool
 	EditMode       bool
+	SectionIndex   int // -1 = whole page; >=0 = section being edited
 	PostURL        string
 	RawContent     string
 	Content        template.HTML

sections.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"bytes"
+	"regexp"
+)
+
+var sectionHeadingRe = regexp.MustCompile(`(?m)^#{1,6} `)
+
+// splitSections splits raw markdown into sections.
+// Section 0 is any content before the first heading.
+// Each subsequent section begins at a heading line and runs to the next.
+func splitSections(raw []byte) [][]byte {
+	locs := sectionHeadingRe.FindAllIndex(raw, -1)
+	if len(locs) == 0 {
+		return [][]byte{raw}
+	}
+	sections := make([][]byte, 0, len(locs)+1)
+	prev := 0
+	for _, loc := range locs {
+		sections = append(sections, raw[prev:loc[0]])
+		prev = loc[0]
+	}
+	sections = append(sections, raw[prev:])
+	return sections
+}
+
+// joinSections reassembles sections produced by splitSections.
+func joinSections(sections [][]byte) []byte {
+	return bytes.Join(sections, nil)
+}