# Epic & Wiki Feature Implementation Summary

## Overview
This document summarizes the implementation of the Epic and Wiki features for the Kanban application.

## What Was Implemented

### Backend (Flask)

#### 1. Database Models

**Epic Model** (`backend/app/models/epic.py`)
- Rich text content support (JSON for Slate.js)
- Hierarchical structure (parent_epic_id for nesting)
- Color coding
- Position ordering
- Board-level scoping
- Soft delete support (closed field)
- Depth limit for hierarchy control

**Wiki Model** (`backend/app/models/wiki.py`)
- Rich text content (JSON for Slate.js)
- URL-friendly slugs
- Summary field
- Categories for organization
- Tags support
- Created by / Updated by tracking
- Board-level scoping

**Card Model Update** (`backend/app/models/card.py`)
- Added `epic_id` foreign key to link cards to epics

**Association Table** (`wiki_entity_links`)
- Many-to-many relationship between Wikis and entity types
- Supports linking Wikis to Cards, Epics, and future entity types

#### 2. Database Migration
- Created migration file: `6fc439155ced_add_epic_and_wiki_models.py`
- Adds all new tables and relationships

### Frontend (React/TypeScript)

#### 1. TypeScript Types (`frontend/src/types/epic.ts`)
```typescript
- Epic interface
- Wiki interface
- CreateEpicRequest / UpdateEpicRequest
- CreateWikiRequest / UpdateWikiRequest
- WikiEntityLink interface
```

#### 2. Components

**RichTextEditor** (`frontend/src/components/RichTextEditor.tsx`)
- Slate.js-based rich text editor
- Editable with proper styling
- Dark mode support
- Placeholder support
- Read-only mode option

**RichTextContent** (`frontend/src/components/RichTextContent.tsx`)
- Read-only renderer for Slate.js content
- Supports paragraphs, lists, blockquotes
- Text formatting (bold, italic, underline, code)
- Dark mode styling

#### 3. Custom Hook

**useEpics** (`frontend/src/hooks/useEpics.ts`)
- Fetch all epics for a board
- Create new epic
- Update existing epic
- Delete epic
- Integrated with global loader and toast notifications
- Error handling with user-friendly messages

#### 4. API Integration

Updated `useApi` hook with epic methods:
```typescript
- getEpics(boardId)
- createEpic(boardId, epicData)
- getEpic(epicId)
- updateEpic(epicId, epicData)
- deleteEpic(epicId)
- addEpicToCard(cardId, epicId)
- removeEpicFromCard(cardId, epicId)
```

## Key Design Decisions

### 1. Epic Hierarchy
- **Decision**: Self-referential foreign key (`parent_epic_id`)
- **Rationale**: Allows flexible nesting of epics with arbitrary depth
- **Feature**: `depth_limit` field to control maximum nesting depth

### 2. Rich Text Storage
- **Decision**: Store as JSON (compatible with Slate.js)
- **Rationale**: 
  - Slate.js natively uses JSON format
  - No serialization/deserialization overhead
  - Easy to query and modify content structure

### 3. Wiki vs Document Naming
- **Decision**: Use "Wiki" instead of "Document"
- **Rationale**: Avoids confusion with file attachments
- **Meaning**: Wiki implies knowledge base / documentation repository

### 4. Entity Linking Strategy
- **Decision**: Polymorphic association table (`wiki_entity_links`)
- **Rationale**: 
  - Single table handles all entity types
  - Easy to add new entity types in future
  - Avoids circular imports and complex schema changes

### 5. Epic-Card Relationship
- **Decision**: One-way reference (Card → Epic)
- **Rationale**: 
  - Simpler than many-to-many (epics contain cards)
  - Cards can belong to one epic at a time
  - Consistent with Jira's parent/child pattern

## Architecture

### Backend Data Flow

```
Board (1) ───────┬─────── (1) Epic
  │               │
  │               │─── (0..*) Card (via epic_id)
  │
  └───────────────┬─────── (0..*) Wiki
                   │
                   └─── wiki_entity_links ───┬── Card
                                            ├── Epic
                                            └── (future entities)
```

### Frontend Component Structure

```
BoardEpics (page)
├── EpicList
│   └── EpicCard
└── CreateEpicModal
    ├── EpicForm
    │   ├── EpicNameInput
    │   ├── EpicDescriptionInput
    │   └── RichTextEditor (content)
    └── ColorPicker
```

## Next Steps

### Immediate Actions Required

1. **Run Database Migration**
   ```bash
   cd backend
   flask db upgrade
   ```

2. **Create Backend Routes** (`backend/app/routes/kanban/epics.py`)
   - CRUD operations for Epics
   - Epic-Card linking endpoints
   - Wiki CRUD operations
   - Wiki-Entity linking endpoints

3. **Create Backend Schemas** (`backend/app/schemas/epic.py`, `wiki.py`)
   - Marshmallow schemas for serialization
   - Input validation

4. **Update BoardEpics Page** (`frontend/src/pages/BoardEpics.tsx`)
   - Implement epic list view
   - Add create epic modal
   - Add epic detail view
   - Include RichTextEditor for epic content

5. **Update Card Detail Page** (`frontend/src/pages/CardDetail.tsx`)
   - Add epic selector dropdown
   - Display linked epic information
   - Add wiki links

### Future Enhancements

1. **Wiki Features**
   - Wiki page with sidebar navigation
   - Markdown export/import
   - Wiki search functionality
   - Version history

2. **Epic Features**
   - Epic progress tracking (cards completed vs total)
   - Epic metrics dashboard
   - Epic drag-and-drop reordering
   - Epic timeline view

3. **UI/UX Improvements**
   - Epic color picker with presets
   - Epic hierarchy tree view
   - Inline card epic assignment
   - Epic templates

4. **Analytics**
   - Epic completion rate
   - Time spent on epic
   - Epic size distribution
   - Wiki usage statistics

## Database Schema

### Epic Table
```sql
CREATE TABLE epics (
    id SERIAL PRIMARY KEY,
    name VARCHAR(200) NOT NULL,
    description TEXT,
    content JSONB,
    color VARCHAR(7),
    closed BOOLEAN DEFAULT FALSE,
    pos FLOAT,
    depth_limit INTEGER,
    board_id INTEGER REFERENCES boards(id),
    parent_epic_id INTEGER REFERENCES epics(id),
    date_last_activity TIMESTAMP,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
```

### Wiki Table
```sql
CREATE TABLE wikis (
    id SERIAL PRIMARY KEY,
    name VARCHAR(200) NOT NULL,
    slug VARCHAR(200) UNIQUE,
    content JSONB NOT NULL,
    summary TEXT,
    category VARCHAR(100),
    board_id INTEGER REFERENCES boards(id),
    created_by INTEGER REFERENCES users(id),
    updated_by INTEGER REFERENCES users(id),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
```

### Wiki Entity Links Table
```sql
CREATE TABLE wiki_entity_links (
    wiki_id INTEGER REFERENCES wikis(id) ON DELETE CASCADE,
    entity_type VARCHAR(50) NOT NULL,
    entity_id INTEGER NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    linked_by INTEGER REFERENCES users(id),
    PRIMARY KEY (wiki_id, entity_type, entity_id)
);
```

## API Endpoints (To Be Implemented)

### Epic Endpoints
```
GET    /api/boards/<board_id>/epics
POST   /api/boards/<board_id>/epics
GET    /api/epics/<epic_id>
PUT    /api/epics/<epic_id>
DELETE /api/epics/<epic_id>
```

### Epic-Card Linking
```
POST   /api/cards/<card_id>/epics
DELETE /api/cards/<card_id>/epics/<epic_id>
```

### Wiki Endpoints
```
GET    /api/boards/<board_id>/wikis
POST   /api/boards/<board_id>/wikis
GET    /api/wikis/<wiki_id>
PUT    /api/wikis/<wiki_id>
DELETE /api/wikis/<wiki_id>
GET    /api/wikis/<wiki_id>/content
```

### Wiki-Entity Linking
```
POST   /api/wikis/<wiki_id>/links
DELETE /api/wikis/<wiki_id>/links/<entity_type>/<entity_id>
```

## Testing Considerations

### Unit Tests
- Epic model creation and relationships
- Wiki model creation and relationships
- Epic hierarchy validation
- Wiki slug generation
- Rich text content serialization

### Integration Tests
- Epic CRUD operations
- Wiki CRUD operations
- Epic-Card linking
- Wiki-Entity linking
- Epic hierarchy operations

### Frontend Tests
- RichTextEditor component
- RichTextContent component
- useEpics hook
- Epic list rendering
- Epic creation form

## Notes

- **Slate.js Content**: Content is stored as raw Slate.js JSON format, which includes element types, text nodes, and formatting information
- **Hierarchical Epics**: While supported, UI for nesting epics is not yet implemented
- **Wiki Slugs**: Slugs should be auto-generated from wiki names and checked for uniqueness
- **Color Codes**: Epic colors should be valid hex codes (e.g., "#ef4444")
- **Position**: Epic positions use float values for flexible reordering (similar to Trello)

## Related Files

### Backend
- `backend/app/models/epic.py` - Epic model
- `backend/app/models/wiki.py` - Wiki model
- `backend/app/models/card.py` - Updated Card model
- `backend/app/models/__init__.py` - Model imports
- `backend/migrations/versions/6fc439155ced_add_epic_and_wiki_models.py` - Migration

### Frontend
- `frontend/src/types/epic.ts` - TypeScript interfaces
- `frontend/src/components/RichTextEditor.tsx` - Editor component
- `frontend/src/components/RichTextContent.tsx` - Content renderer
- `frontend/src/hooks/useEpics.ts` - Epic custom hook
- `frontend/src/hooks/useApi.ts` - Updated API methods