feat: add File Explorer sidebar panel

src/sidebar/explorer-panel.js

@@ -0,0 +1,70 @@
+const path = require('path');
+
+function renderExplorerPanel(container, { listDirectory, onFileOpen, currentDir }) {
+    container.innerHTML = `
+        <div class="explorer-panel">
+            <div class="explorer-toolbar">
+                <input type="text" class="explorer-path" id="explorer-path" value="${currentDir || ''}" placeholder="Open a folder..." readonly>
+                <button class="explorer-browse-btn" id="explorer-browse" title="Browse folder">&#x1F4C2;</button>
+            </div>
+            <div class="explorer-tree" id="explorer-tree"></div>
+        </div>
+    `;
+
+    document.getElementById('explorer-browse')?.addEventListener('click', async () => {
+        const dir = await listDirectory(null); // null means open folder dialog
+        if (dir) {
+            document.getElementById('explorer-path').value = dir.path;
+            renderTree(document.getElementById('explorer-tree'), dir.entries, listDirectory, onFileOpen, dir.path);
+        }
+    });
+
+    if (currentDir) {
+        listDirectory(currentDir).then(dir => {
+            if (dir) renderTree(document.getElementById('explorer-tree'), dir.entries, listDirectory, onFileOpen, currentDir);
+        });
+    }
+}
+
+function renderTree(container, entries, listDirectory, onFileOpen, basePath) {
+    container.innerHTML = entries.map(entry => {
+        if (entry.isDirectory) {
+            return `<div class="tree-item tree-folder collapsed" data-path="${entry.path}">
+                <span class="tree-icon">&#x25B6;</span>
+                <span class="tree-name">${entry.name}</span>
+                <div class="tree-children"></div>
+            </div>`;
+        }
+        return `<div class="tree-item tree-file" data-path="${entry.path}">
+            <span class="tree-icon">${getFileIcon(entry.name)}</span>
+            <span class="tree-name">${entry.name}</span>
+        </div>`;
+    }).join('');
+
+    container.querySelectorAll('.tree-folder').forEach(el => {
+        el.querySelector('.tree-name').addEventListener('click', async () => {
+            const isCollapsed = el.classList.contains('collapsed');
+            if (isCollapsed) {
+                const dir = await listDirectory(el.dataset.path);
+                if (dir) {
+                    const childContainer = el.querySelector('.tree-children');
+                    renderTree(childContainer, dir.entries, listDirectory, onFileOpen, el.dataset.path);
+                }
+            }
+            el.classList.toggle('collapsed');
+            el.querySelector('.tree-icon').textContent = el.classList.contains('collapsed') ? '\u25B6' : '\u25BC';
+        });
+    });
+
+    container.querySelectorAll('.tree-file').forEach(el => {
+        el.addEventListener('click', () => onFileOpen(el.dataset.path));
+    });
+}
+
+function getFileIcon(filename) {
+    const ext = filename.split('.').pop().toLowerCase();
+    const icons = { md: '\u{1F4DD}', js: '\u{1F4DC}', json: '{}', html: '\u{1F310}', css: '\u{1F3A8}', py: '\u{1F40D}', pdf: '\u{1F4D5}', txt: '\u{1F4C4}' };
+    return icons[ext] || '\u{1F4C4}';
+}
+
+module.exports = { renderExplorerPanel };