feat(renderer): StatusBar reads from editor store (word count, cursor pos)

src/renderer/components/editor/CodeMirrorEditor.tsx

@@ -0,0 +1,80 @@
+import { useEffect, useRef } from 'react';
+import { EditorState, Compartment } from '@codemirror/state';
+import { EditorView, keymap, lineNumbers, highlightActiveLine, drawSelection } from '@codemirror/view';
+import { defaultKeymap, history, historyKeymap, indentWithTab } from '@codemirror/commands';
+import { markdown, markdownLanguage } from '@codemirror/lang-markdown';
+import { searchKeymap, highlightSelectionMatches } from '@codemirror/search';
+import { autocompletion, completionKeymap } from '@codemirror/autocomplete';
+import { oneDark } from '@codemirror/theme-one-dark';
+import { useTheme } from 'next-themes';
+import { lightTheme, lightHighlight } from './themes/light';
+import { useEditorStore } from '@/stores/editor-store';
+
+interface Props {
+  bufferId: string;
+  initialContent: string;
+  onChange?: (content: string) => void;
+  onCursorChange?: (line: number, column: number) => void;
+}
+
+export function CodeMirrorEditor({ bufferId, initialContent, onChange, onCursorChange }: Props) {
+  const ref = useRef<HTMLDivElement>(null);
+  const viewRef = useRef<EditorView | null>(null);
+  const themeCompartment = useRef(new Compartment());
+  const { resolvedTheme } = useTheme();
+  const updateContent = useEditorStore((s) => s.updateContent);
+  const setCursor = useEditorStore((s) => s.setCursor);
+
+  useEffect(() => {
+    if (!ref.current) return;
+    const state = EditorState.create({
+      doc: initialContent,
+      extensions: [
+        lineNumbers(),
+        highlightActiveLine(),
+        highlightSelectionMatches(),
+        history(),
+        drawSelection(),
+        markdown({ base: markdownLanguage, codeLanguages: [] }),
+        autocompletion(),
+        keymap.of([...defaultKeymap, ...historyKeymap, ...searchKeymap, ...completionKeymap, indentWithTab]),
+        themeCompartment.current.of(resolvedTheme === 'dark' ? [oneDark] : [lightTheme, lightHighlight]),
+        EditorView.lineWrapping,
+        EditorView.updateListener.of((v) => {
+          if (v.docChanged) {
+            const content = v.state.doc.toString();
+            updateContent(bufferId, content);
+            onChange?.(content);
+          }
+          if (v.selectionSet || v.docChanged) {
+            const head = v.state.selection.main.head;
+            const line = v.state.doc.lineAt(head);
+            const lineNo = line.number;
+            const col = head - line.from + 1;
+            setCursor(bufferId, lineNo, col);
+            onCursorChange?.(lineNo, col);
+          }
+        }),
+      ],
+    });
+    const view = new EditorView({ state, parent: ref.current });
+    viewRef.current = view;
+    return () => {
+      view.destroy();
+      viewRef.current = null;
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [bufferId]);
+
+  useEffect(() => {
+    const view = viewRef.current;
+    if (!view) return;
+    view.dispatch({
+      effects: themeCompartment.current.reconfigure(
+        resolvedTheme === 'dark' ? [oneDark] : [lightTheme, lightHighlight]
+      ),
+    });
+  }, [resolvedTheme]);
+
+  return <div ref={ref} className="h-full overflow-hidden" />;
+}

src/renderer/components/editor/EditorPane.tsx

@@ -0,0 +1,25 @@
+import { CodeMirrorEditor } from './CodeMirrorEditor';
+import { useEditorStore } from '@/stores/editor-store';
+
+export function EditorPane() {
+  const { buffers, activeId } = useEditorStore();
+  const buf = activeId ? buffers.get(activeId) : null;
+
+  if (!buf) {
+    return (
+      <div className="flex h-full items-center justify-center bg-background text-muted-foreground">
+        <p>No file open. Use File → Open to start.</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="h-full">
+      <CodeMirrorEditor
+        key={buf.id}
+        bufferId={buf.id}
+        initialContent={buf.content}
+      />
+    </div>
+  );
+}

src/renderer/components/editor/themes/light.ts

@@ -0,0 +1,55 @@
+import { EditorView } from '@codemirror/view';
+import { HighlightStyle, syntaxHighlighting } from '@codemirror/language';
+import { tags as t } from '@lezer/highlight';
+
+const colors = {
+  background: '#ffffff',
+  foreground: '#0d0b09',
+  cursor: '#e5461f',
+  selection: 'rgba(229, 70, 31, 0.15)',
+  gutterBackground: '#fafbfc',
+  gutterForeground: '#7a7878',
+  lineHighlight: 'rgba(0, 0, 0, 0.04)',
+};
+
+export const lightTheme = EditorView.theme(
+  {
+    '&': {
+      backgroundColor: colors.background,
+      color: colors.foreground,
+      height: '100%',
+    },
+    '.cm-content': {
+      caretColor: colors.cursor,
+      fontFamily: 'JetBrains Mono, Fira Code, monospace',
+      fontSize: '13.5px',
+    },
+    '.cm-cursor, .cm-dropCursor': { borderLeftColor: colors.cursor },
+    '&.cm-focused .cm-selectionBackground, .cm-selectionBackground, ::selection': {
+      backgroundColor: colors.selection,
+    },
+    '.cm-gutters': {
+      backgroundColor: colors.gutterBackground,
+      color: colors.gutterForeground,
+      border: 'none',
+    },
+    '.cm-activeLine': { backgroundColor: colors.lineHighlight },
+    '.cm-activeLineGutter': { backgroundColor: 'transparent', color: '#e5461f' },
+  },
+  { dark: false }
+);
+
+const highlightStyle = HighlightStyle.define([
+  { tag: t.heading1, color: '#0d0b09', fontWeight: '700' },
+  { tag: t.heading2, color: '#0d0b09', fontWeight: '700' },
+  { tag: t.heading3, color: '#464646', fontWeight: '600' },
+  { tag: t.link, color: '#e5461f', textDecoration: 'underline' },
+  { tag: t.url, color: '#e5461f' },
+  { tag: t.emphasis, fontStyle: 'italic' },
+  { tag: t.strong, fontWeight: '700' },
+  { tag: t.monospace, color: '#c93a18' },
+  { tag: t.list, color: '#0ea5e9' },
+  { tag: t.quote, color: '#7a7878', fontStyle: 'italic' },
+]);
+
+export const lightHighlight = syntaxHighlighting(highlightStyle);

src/renderer/components/layout/AppShell.tsx

@@ -3,6 +3,7 @@ import { TabBar } from './TabBar';
 import { Toolbar } from './Toolbar';
 import { Breadcrumb } from './Breadcrumb';
 import { StatusBar } from './StatusBar';
+import { EditorPane } from '@/components/editor/EditorPane';
 import { useAppStore } from '@/stores/app-store';
 import { ResizablePanelGroup, ResizablePanel, ResizableHandle } from '@/components/ui/resizable';
 
@@ -31,9 +32,7 @@ export function AppShell() {
             </>
           )}
           <ResizablePanel defaultSize={previewVisible ? paneSizes.editor : 100} minSize={20}>
-            <section className="h-full bg-background p-4 text-sm text-muted-foreground">
+            <EditorPane />
-              Editor placeholder
-            </section>
           </ResizablePanel>
           {previewVisible && (
             <>

src/renderer/components/layout/StatusBar.tsx

@@ -1,12 +1,23 @@
+import { useEditorStore } from '@/stores/editor-store';
+
+function countWords(text: string): number {
+  return text.trim().length === 0 ? 0 : text.trim().split(/\s+/).length;
+}
+
 export function StatusBar() {
+  const { buffers, activeId } = useEditorStore();
+  const buf = activeId ? buffers.get(activeId) : null;
+  const wordCount = buf ? countWords(buf.content) : 0;
+  const cursor = buf?.cursor ?? { line: 1, column: 1 };
+
   return (
     <footer className="flex h-7 items-center justify-between border-t border-border bg-card/20 px-3 text-xs text-muted-foreground">
       <div className="flex items-center gap-4">
-        <span>0 words</span>
+        <span>{wordCount} words</span>
         <span>UTF-8</span>
       </div>
       <div className="flex items-center gap-4">
-        <span>Ln 1, Col 1</span>
+        <span>Ln {cursor.line}, Col {cursor.column}</span>
         <span>Markdown</span>
       </div>
     </footer>

src/renderer/stores/editor-store.ts

@@ -0,0 +1,63 @@
+import { create } from 'zustand';
+import { immer } from 'zustand/middleware/immer';
+import { enableMapSet } from 'immer';
+
+enableMapSet();
+
+export interface Buffer {
+  id: string;
+  path: string;
+  content: string;
+  dirty: boolean;
+  cursor?: { line: number; column: number };
+}
+
+interface EditorState {
+  buffers: Map<string, Buffer>;
+  activeId: string | null;
+  openBuffer: (id: string, path: string, content: string) => void;
+  updateContent: (id: string, content: string) => void;
+  markSaved: (id: string) => void;
+  setCursor: (id: string, line: number, column: number) => void;
+  closeBuffer: (id: string) => void;
+  setActive: (id: string) => void;
+}
+
+export const useEditorStore = create<EditorState>()(
+  immer((set) => ({
+    buffers: new Map(),
+    activeId: null,
+    openBuffer: (id, path, content) =>
+      set((s) => {
+        s.buffers.set(id, { id, path, content, dirty: false });
+        s.activeId = id;
+      }),
+    updateContent: (id, content) =>
+      set((s) => {
+        const buf = s.buffers.get(id);
+        if (buf) {
+          buf.content = content;
+          buf.dirty = true;
+        }
+      }),
+    markSaved: (id) =>
+      set((s) => {
+        const buf = s.buffers.get(id);
+        if (buf) buf.dirty = false;
+      }),
+    setCursor: (id, line, column) =>
+      set((s) => {
+        const buf = s.buffers.get(id);
+        if (buf) buf.cursor = { line, column };
+      }),
+    closeBuffer: (id) =>
+      set((s) => {
+        s.buffers.delete(id);
+        if (s.activeId === id) s.activeId = null;
+      }),
+    setActive: (id) =>
+      set((s) => {
+        s.activeId = id;
+      }),
+  }))
+);

tests/component/editor/EditorPane.test.tsx

@@ -0,0 +1,38 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { ThemeProvider } from '@/components/theme-provider';
+import { EditorPane } from '@/components/editor/EditorPane';
+import { useEditorStore } from '@/stores/editor-store';
+import { CodeMirrorEditor } from '@/components/editor/CodeMirrorEditor';
+
+vi.mock('@/components/editor/CodeMirrorEditor', () => ({
+  CodeMirrorEditor: ({ initialContent }: { initialContent: string }) => (
+    <div data-testid="codemirror-mock">{initialContent}</div>
+  ),
+}));
+
+describe('EditorPane', () => {
+  beforeEach(() => {
+    useEditorStore.setState({ buffers: new Map(), activeId: null });
+  });
+
+  it('renders the empty state when no buffer is open', () => {
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <EditorPane />
+      </ThemeProvider>
+    );
+    expect(screen.getByText(/no file open/i)).toBeInTheDocument();
+  });
+
+  it('renders the editor when a buffer is open', () => {
+    useEditorStore.getState().openBuffer('b1', '/x.md', '# hello');
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <EditorPane />
+      </ThemeProvider>
+    );
+    expect(screen.getByTestId('codemirror-mock')).toBeInTheDocument();
+    expect(screen.getByTestId('codemirror-mock')).toHaveTextContent('# hello');
+  });
+});

tests/unit/stores/editor-store.test.ts

@@ -0,0 +1,36 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useEditorStore } from '@/stores/editor-store';
+
+describe('useEditorStore', () => {
+  beforeEach(() => {
+    useEditorStore.setState({ buffers: new Map(), activeId: null });
+  });
+
+  it('creates a new buffer with the given content', () => {
+    useEditorStore.getState().openBuffer('file-1', '/foo.md', '# hello');
+    const buf = useEditorStore.getState().buffers.get('file-1');
+    expect(buf?.content).toBe('# hello');
+    expect(buf?.path).toBe('/foo.md');
+  });
+
+  it('updates content and marks dirty', () => {
+    useEditorStore.getState().openBuffer('file-1', '/foo.md', '');
+    useEditorStore.getState().updateContent('file-1', 'new content');
+    const buf = useEditorStore.getState().buffers.get('file-1');
+    expect(buf?.content).toBe('new content');
+    expect(buf?.dirty).toBe(true);
+  });
+
+  it('marks a buffer clean after save', () => {
+    useEditorStore.getState().openBuffer('file-1', '/foo.md', '');
+    useEditorStore.getState().updateContent('file-1', 'x');
+    useEditorStore.getState().markSaved('file-1');
+    expect(useEditorStore.getState().buffers.get('file-1')?.dirty).toBe(false);
+  });
+
+  it('closes a buffer and removes it', () => {
+    useEditorStore.getState().openBuffer('file-1', '/foo.md', '');
+    useEditorStore.getState().closeBuffer('file-1');
+    expect(useEditorStore.getState().buffers.has('file-1')).toBe(false);
+  });
+});