# Phase 2 — Builder Upgrade Implementation Plan

> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.

**Goal:** Transform the FormBuilderModal with drag & drop, live preview, and undo/redo.

**Architecture:** All three features modify `form-builder.ts`. Undo/redo is implemented first (provides infrastructure), then drag & drop (uses pushSnapshot), then layout restructure for preview. Each task builds on the previous.

**Tech Stack:** TypeScript, Obsidian API, HTML5 Drag & Drop, esbuild

---

### Task 1: Add undo/redo infrastructure

**Files:**
- Modify: `src/ui/form-builder.ts`

**Step 1: Add instance variables and imports**

At the top of `FormBuilderModal` class, after the existing `private onSave` line, add:

```typescript
  private history: FormDefinition[] = [];
  private historyIndex = 0;
```

**Step 2: Initialize history in constructor**

In the constructor, after `this.onSave = onSave;`, add:

```typescript
    this.history = [structuredClone(this.draft)];
    this.historyIndex = 0;
```

**Step 3: Add pushSnapshot, undo, redo methods**

Add these three methods after the `onClose()` method, before `render()`:

```typescript
  private pushSnapshot(): void {
    // Truncate any forward history
    this.history = this.history.slice(0, this.historyIndex + 1);
    this.history.push(structuredClone(this.draft));
    // Cap at 30 entries
    if (this.history.length > 30) {
      this.history.shift();
    } else {
      this.historyIndex++;
    }
  }

  private undo(): void {
    if (this.historyIndex <= 0) return;
    this.historyIndex--;
    this.draft = structuredClone(this.history[this.historyIndex]);
    this.render();
  }

  private redo(): void {
    if (this.historyIndex >= this.history.length - 1) return;
    this.historyIndex++;
    this.draft = structuredClone(this.history[this.historyIndex]);
    this.render();
  }
```

**Step 4: Add keyboard listener in render()**

In the `render()` method, right after `contentEl.addClass('ff-builder-modal');`, add:

```typescript
    // Undo/Redo keyboard shortcuts
    contentEl.addEventListener('keydown', (e: KeyboardEvent) => {
      if (e.key === 'z' && (e.ctrlKey || e.metaKey) && !e.shiftKey) {
        e.preventDefault();
        this.undo();
      } else if (e.key === 'z' && (e.ctrlKey || e.metaKey) && e.shiftKey) {
        e.preventDefault();
        this.redo();
      }
    });
```

**Step 5: Add undo/redo buttons in footer**

In the `render()` method, replace the entire footer section (from `const footer = ...` through the save button click handler) with:

```typescript
    // --- Footer ---
    const footer = contentEl.createDiv({ cls: 'ff-builder-footer' });

    // Left side: undo/redo
    const undoRedoEl = footer.createDiv({ cls: 'ff-builder-undo-redo' });

    const undoBtn = undoRedoEl.createEl('button', {
      cls: 'ff-builder-action-btn',
      text: '\u21A9',
    });
    undoBtn.setAttribute('aria-label', 'Undo (Ctrl+Z)');
    if (this.historyIndex <= 0) undoBtn.setAttribute('disabled', '');
    undoBtn.addEventListener('click', () => this.undo());

    const redoBtn = undoRedoEl.createEl('button', {
      cls: 'ff-builder-action-btn',
      text: '\u21AA',
    });
    redoBtn.setAttribute('aria-label', 'Redo (Ctrl+Shift+Z)');
    if (this.historyIndex >= this.history.length - 1) redoBtn.setAttribute('disabled', '');
    redoBtn.addEventListener('click', () => this.redo());

    // Right side: cancel/save
    const footerRight = footer.createDiv({ cls: 'ff-builder-footer-right' });

    const cancelBtn = footerRight.createEl('button', { text: 'Cancel' });
    cancelBtn.addEventListener('click', () => {
      this.close();
    });

    const saveBtn = footerRight.createEl('button', {
      text: 'Save',
      cls: 'mod-cta',
    });
    saveBtn.addEventListener('click', () => {
      if (!this.draft.name.trim()) {
        new Notice('Form name cannot be empty.');
        return;
      }
      this.onSave(this.draft);
      this.close();
    });
```

**Step 6: Add pushSnapshot to all mutation points**

In the `render()` method:

1. Before the mode dropdown onChange mutation, add `this.pushSnapshot();` before `this.draft.mode = v as ...`:
```typescript
      (v) => {
        this.pushSnapshot();
        this.draft.mode = v as 'create' | 'update';
        this.render();
      },
```

2. Before the add-field mutation, add `this.pushSnapshot();` before `this.draft.fields.push(newField)`:
```typescript
    addBtn.addEventListener('click', () => {
      const newField: FormField = {
        id: `field_${Date.now()}`,
        label: 'New Field',
        type: 'text',
        required: false,
      };
      this.pushSnapshot();
      this.draft.fields.push(newField);
      this.render();
    });
```

In the `renderFields()` method:

3. Before move-up swap: add `this.pushSnapshot();`
```typescript
        upBtn.addEventListener('click', () => {
          this.pushSnapshot();
          [this.draft.fields[i - 1], this.draft.fields[i]] = [
            this.draft.fields[i],
            this.draft.fields[i - 1],
          ];
          this.render();
        });
```

4. Before move-down swap: add `this.pushSnapshot();`
```typescript
        downBtn.addEventListener('click', () => {
          this.pushSnapshot();
          [this.draft.fields[i], this.draft.fields[i + 1]] = [
            this.draft.fields[i + 1],
            this.draft.fields[i],
          ];
          this.render();
        });
```

5. Before delete splice: add `this.pushSnapshot();`
```typescript
      deleteBtn.addEventListener('click', () => {
        this.pushSnapshot();
        this.draft.fields.splice(i, 1);
        this.render();
      });
```

6. Before type change: add `this.pushSnapshot();`
```typescript
        (v) => {
          this.pushSnapshot();
          field.type = v as FieldType;
          this.render();
        },
```

**Step 7: Add pushSnapshot to setting helpers**

Modify each helper to call `this.pushSnapshot()` before invoking the callback:

In `addTextSetting`:
```typescript
    input.addEventListener('change', () => {
      this.pushSnapshot();
      onChange(input.value);
    });
```

In `addTextareaSetting`:
```typescript
    textarea.addEventListener('change', () => {
      this.pushSnapshot();
      onChange(textarea.value);
    });
```

In `addDropdownSetting`:
```typescript
    select.addEventListener('change', () => {
      this.pushSnapshot();
      onChange(select.value);
    });
```

In `addToggleSetting`:
```typescript
    toggle.addEventListener('click', () => {
      this.pushSnapshot();
      const enabled = !toggle.hasClass('is-enabled');
      toggle.toggleClass('is-enabled', enabled);
      onChange(enabled);
    });
```

**Step 8: Build to verify**

Run: `node esbuild.config.mjs`
Expected: No errors

**Step 9: Commit**

```bash
git add src/ui/form-builder.ts
git commit -m "feat: add snapshot-based undo/redo to form builder"
```

---

### Task 2: Add drag & drop field reordering

**Files:**
- Modify: `src/ui/form-builder.ts` (renderFields method)

**Step 1: Add instance variable**

After the `historyIndex` declaration, add:

```typescript
  private dragSourceIndex: number | null = null;
```

**Step 2: Add drag handle and events to renderFields()**

In the `renderFields()` method, make these changes to each field element:

After `const fieldEl = container.createDiv({ cls: 'ff-builder-field' });`, add:
```typescript
      fieldEl.setAttribute('draggable', 'true');
      fieldEl.dataset.index = String(i);
```

In the header section, add a drag handle BEFORE the field number span:
```typescript
      headerEl.createSpan({
        cls: 'ff-drag-handle',
        text: '\u2807',
      });
```

After the delete button (after the entire actions section), add drag event handlers on `fieldEl`:

```typescript
      // --- Drag & Drop ---
      fieldEl.addEventListener('dragstart', (e: DragEvent) => {
        this.dragSourceIndex = i;
        fieldEl.addClass('ff-dragging');
        if (e.dataTransfer) {
          e.dataTransfer.effectAllowed = 'move';
        }
      });

      fieldEl.addEventListener('dragend', () => {
        this.dragSourceIndex = null;
        fieldEl.removeClass('ff-dragging');
      });

      fieldEl.addEventListener('dragover', (e: DragEvent) => {
        e.preventDefault();
        if (this.dragSourceIndex === null || this.dragSourceIndex === i) return;
        if (e.dataTransfer) e.dataTransfer.dropEffect = 'move';

        const rect = fieldEl.getBoundingClientRect();
        const midY = rect.top + rect.height / 2;
        fieldEl.removeClass('ff-drop-above', 'ff-drop-below');
        if (e.clientY < midY) {
          fieldEl.addClass('ff-drop-above');
        } else {
          fieldEl.addClass('ff-drop-below');
        }
      });

      fieldEl.addEventListener('dragleave', () => {
        fieldEl.removeClass('ff-drop-above', 'ff-drop-below');
      });

      fieldEl.addEventListener('drop', (e: DragEvent) => {
        e.preventDefault();
        fieldEl.removeClass('ff-drop-above', 'ff-drop-below');
        if (this.dragSourceIndex === null || this.dragSourceIndex === i) return;

        const rect = fieldEl.getBoundingClientRect();
        const midY = rect.top + rect.height / 2;
        const insertBefore = e.clientY < midY;

        this.pushSnapshot();
        const [moved] = this.draft.fields.splice(this.dragSourceIndex, 1);
        let targetIndex = insertBefore ? i : i + 1;
        if (this.dragSourceIndex < i) targetIndex--;
        this.draft.fields.splice(targetIndex, 0, moved);
        this.dragSourceIndex = null;
        this.render();
      });
```

**Step 3: Build to verify**

Run: `node esbuild.config.mjs`
Expected: No errors

**Step 4: Commit**

```bash
git add src/ui/form-builder.ts
git commit -m "feat: add drag & drop field reordering to form builder"
```

---

### Task 3: Add side-by-side live preview

**Files:**
- Modify: `src/ui/form-builder.ts`

**Step 1: Add import for renderField**

At the top of the file, change the imports to include renderField:

```typescript
import { App, Modal, Notice } from 'obsidian';
import { FormDefinition, FormField, FieldType } from '../types';
import { renderField } from './field-renderers';
```

**Step 2: Restructure render() to use grid layout**

In the `render()` method, replace the content between the keyboard listener and the footer with a grid layout. The full `render()` method should become:

```typescript
  private render(): void {
    const { contentEl } = this;
    contentEl.empty();
    contentEl.addClass('ff-builder-modal');

    // Undo/Redo keyboard shortcuts
    contentEl.addEventListener('keydown', (e: KeyboardEvent) => {
      if (e.key === 'z' && (e.ctrlKey || e.metaKey) && !e.shiftKey) {
        e.preventDefault();
        this.undo();
      } else if (e.key === 'z' && (e.ctrlKey || e.metaKey) && e.shiftKey) {
        e.preventDefault();
        this.redo();
      }
    });

    // --- Two-column layout ---
    const layout = contentEl.createDiv({ cls: 'ff-builder-layout' });

    // === LEFT: Editor ===
    const editorEl = layout.createDiv({ cls: 'ff-builder-editor' });

    editorEl.createEl('h2', { text: 'Form Settings' });

    const generalEl = editorEl.createDiv({ cls: 'ff-builder-general' });

    // Name
    this.addTextSetting(generalEl, 'Form Name', this.draft.name, (v) => {
      this.draft.name = v;
    });

    // Mode
    this.addDropdownSetting(
      generalEl,
      'Mode',
      ['create', 'update'],
      this.draft.mode,
      (v) => {
        this.pushSnapshot();
        this.draft.mode = v as 'create' | 'update';
        this.render();
      },
    );

    // Mode-specific settings
    if (this.draft.mode === 'create') {
      this.addTextSetting(
        generalEl,
        'Target Folder',
        this.draft.targetFolder ?? '/',
        (v) => {
          this.draft.targetFolder = v;
        },
      );
      this.addTextSetting(
        generalEl,
        'File Name Template',
        this.draft.fileNameTemplate ?? '{{date}}-{{title}}',
        (v) => {
          this.draft.fileNameTemplate = v;
        },
      );
      this.addTextareaSetting(
        generalEl,
        'Body Template',
        this.draft.bodyTemplate ?? '',
        (v) => {
          this.draft.bodyTemplate = v;
        },
      );
    } else {
      this.addDropdownSetting(
        generalEl,
        'Target File',
        ['active', 'prompt'],
        this.draft.targetFile ?? 'active',
        (v) => {
          this.draft.targetFile = v as 'active' | 'prompt';
        },
      );
    }

    // Fields section
    editorEl.createEl('h3', { text: 'Fields' });

    const fieldsContainer = editorEl.createDiv({ cls: 'ff-builder-fields' });
    this.renderFields(fieldsContainer);

    // Add field button
    const addBtn = editorEl.createEl('button', {
      cls: 'ff-builder-add-btn',
      text: '+ Add Field',
    });
    addBtn.addEventListener('click', () => {
      const newField: FormField = {
        id: `field_${Date.now()}`,
        label: 'New Field',
        type: 'text',
        required: false,
      };
      this.pushSnapshot();
      this.draft.fields.push(newField);
      this.render();
    });

    // === RIGHT: Preview ===
    const previewEl = layout.createDiv({ cls: 'ff-builder-preview' });
    previewEl.createEl('h2', { text: 'Preview' });

    const previewContent = previewEl.createDiv({ cls: 'ff-builder-preview-content' });

    if (this.draft.fields.length === 0) {
      previewContent.createDiv({
        cls: 'ff-builder-preview-empty',
        text: 'Add fields to see a preview.',
      });
    } else {
      // Form title
      previewContent.createEl('h3', {
        text: this.draft.name || 'Untitled Form',
        cls: 'ff-form-title',
      });

      // Render each field
      const previewFields = previewContent.createDiv({ cls: 'ff-fields' });
      for (const field of this.draft.fields) {
        renderField(this.app, previewFields, field, field.defaultValue);
      }

      // Disabled submit button
      const previewFooter = previewContent.createDiv({ cls: 'ff-form-footer' });
      const previewSubmit = previewFooter.createEl('button', {
        text: this.draft.mode === 'create' ? 'Create Note' : 'Update Frontmatter',
        cls: 'mod-cta ff-submit-btn',
      });
      previewSubmit.setAttribute('disabled', '');
    }

    // --- Footer (full width, below grid) ---
    const footer = contentEl.createDiv({ cls: 'ff-builder-footer' });

    // Left side: undo/redo
    const undoRedoEl = footer.createDiv({ cls: 'ff-builder-undo-redo' });

    const undoBtn = undoRedoEl.createEl('button', {
      cls: 'ff-builder-action-btn',
      text: '\u21A9',
    });
    undoBtn.setAttribute('aria-label', 'Undo (Ctrl+Z)');
    if (this.historyIndex <= 0) undoBtn.setAttribute('disabled', '');
    undoBtn.addEventListener('click', () => this.undo());

    const redoBtn = undoRedoEl.createEl('button', {
      cls: 'ff-builder-action-btn',
      text: '\u21AA',
    });
    redoBtn.setAttribute('aria-label', 'Redo (Ctrl+Shift+Z)');
    if (this.historyIndex >= this.history.length - 1) redoBtn.setAttribute('disabled', '');
    redoBtn.addEventListener('click', () => this.redo());

    // Right side: cancel/save
    const footerRight = footer.createDiv({ cls: 'ff-builder-footer-right' });

    const cancelBtn = footerRight.createEl('button', { text: 'Cancel' });
    cancelBtn.addEventListener('click', () => {
      this.close();
    });

    const saveBtn = footerRight.createEl('button', {
      text: 'Save',
      cls: 'mod-cta',
    });
    saveBtn.addEventListener('click', () => {
      if (!this.draft.name.trim()) {
        new Notice('Form name cannot be empty.');
        return;
      }
      this.onSave(this.draft);
      this.close();
    });
  }
```

Note: This replaces the ENTIRE render() method. The renderFields() method and setting helpers stay unchanged from Task 2.

**Step 3: Build to verify**

Run: `node esbuild.config.mjs`
Expected: No errors

**Step 4: Commit**

```bash
git add src/ui/form-builder.ts
git commit -m "feat: add side-by-side live preview to form builder"
```

---

### Task 4: Add Phase 2 styles

**Files:**
- Modify: `styles.css`

**Step 1: Add drag & drop styles**

Add after the existing `.ff-builder-field-body` rule (after `padding: 10px;`):

```css
/* --- Drag & Drop --- */

.ff-drag-handle {
  cursor: grab;
  color: var(--text-faint);
  font-size: 1rem;
  line-height: 1;
  user-select: none;
  transition: color 0.15s ease;
  padding: 0 2px;
}

.ff-drag-handle:hover {
  color: var(--text-muted);
}

.ff-builder-field.ff-dragging {
  opacity: 0.4;
}

.ff-builder-field.ff-drop-above {
  border-top: 2px solid var(--interactive-accent);
}

.ff-builder-field.ff-drop-below {
  border-bottom: 2px solid var(--interactive-accent);
}
```

**Step 2: Update builder modal width and add layout styles**

Replace the existing `.ff-builder-modal` rule:

```css
.ff-builder-modal {
  max-width: 1100px;
  margin: 0 auto;
}
```

Add after `.ff-builder-modal h3`:

```css
/* --- Two-column layout --- */

.ff-builder-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  min-height: 300px;
}

.ff-builder-editor {
  min-width: 0;
}
```

**Step 3: Add preview panel styles**

Add after the `.ff-builder-editor` rule:

```css
/* --- Preview panel --- */

.ff-builder-preview {
  border-left: 1px solid var(--background-modifier-border);
  padding-left: 24px;
  min-width: 0;
}

.ff-builder-preview h2 {
  position: sticky;
  top: 0;
  background: var(--background-primary);
  padding-bottom: 8px;
  z-index: 1;
}

.ff-builder-preview-content {
  max-height: 55vh;
  overflow-y: auto;
  padding-right: 4px;
}

.ff-builder-preview-empty {
  padding: 32px 16px;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}
```

**Step 4: Add undo/redo footer styles**

Replace the existing `.ff-builder-footer` rule:

```css
.ff-builder-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--background-modifier-border);
}

.ff-builder-undo-redo {
  display: flex;
  gap: 4px;
}

.ff-builder-footer-right {
  display: flex;
  gap: 8px;
}

.ff-builder-action-btn:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}
```

**Step 5: Build to verify**

Run: `node esbuild.config.mjs`
Expected: No errors

**Step 6: Commit**

```bash
git add styles.css
git commit -m "feat: add styles for drag & drop, preview panel, and undo/redo"
```

---

### Task 5: Final build and verification

**Step 1: Clean build**

Run: `node esbuild.config.mjs`
Expected: Build succeeds, no errors

**Step 2: Verify all files are tracked**

Run: `git status`
Expected: Clean working tree

**Step 3: Verify commit history**

Run: `git log --oneline -6`
Expected: 4 new commits on top of Phase 1 history