# Writing Plugins

BetterCurseForge features a lightweight plugin system that allows you to extend CurseForge Launcher functionality, manipulate the DOM, hook runtime methods, and persist configuration.

---

## Plugin Directory Structure

Plugins are stored in the BetterCurseForge user directory:

```text
%APPDATA%\CurseForge\BetterCurseForge\plugins\
```

Each plugin lives in its own dedicated subfolder:

```text
plugins/
└── compact-mode/
    ├── manifest.json       # Required: Plugin metadata
    ├── index.js            # Required: Entry script
    └── styles.css          # Optional: Companion stylesheet
```

You can open the plugins folder directly from the BetterCurseForge desktop GUI by clicking **Open Plugins Folder**.

---

## Plugin Manifest (`manifest.json`)

The `manifest.json` file declares your plugin's metadata:

```json
{
  "id": "compact-mode",
  "name": "Compact Mode",
  "version": "1.0.0",
  "description": "Reduces padding across mod lists, sidebar items, and modpack details for high-density browsing.",
  "author": "ModderDev",
  "main": "index.js",
  "styles": "styles.css"
}
```

### Manifest Fields

| Field | Type | Required | Description |
| :--- | :--- | :--- | :--- |
| `name` | `string` | **Yes** | Display name shown in the management UI. |
| `version` | `string` | **Yes** | Semantic version string (e.g. `1.0.0`). |
| `description` | `string` | No | Brief summary of what the plugin accomplishes. |
| `author` | `string` | No | Author name or handle. |
| `main` | `string` | No | Entry JavaScript file. Defaults to `index.js`. |
| `styles` | `string` | No | Companion stylesheet injected automatically on enable. Defaults to `styles.css`. |

---

## Plugin Lifecycle & Execution

Plugin scripts are executed when enabled, receiving the `BetterCurseForge` global API and a `plugin` context object:

```javascript
// index.js
// BetterCurseForge passes (BetterCurseForge, plugin)
const { injectCSS, patcher, settings, on, off } = BetterCurseForge;

console.log('[MyPlugin] Plugin initialized!');

// Attach an onDisable cleanup handler:
plugin.onDisable = () => {
  console.log('[MyPlugin] Plugin disabled! Cleaning up...');
  // Remove any custom DOM elements, event listeners, or intervals here
};
```

::: tip AUTOMATIC STYLE INJECTION & REMOVAL
If your plugin folder contains a `styles.css` (or file declared in `"styles"` in `manifest.json`), BetterCurseForge automatically injects it into `<head>` when your plugin is enabled and removes it when disabled! You do not need to manually inject or clean up companion stylesheets.
:::

---

## BetterCurseForge Plugin APIs

### 1. `BetterCurseForge.injectCSS(css)`
Injects custom CSS dynamically into `<head>`. Returns a cleanup function that unmounts the style tag:

```javascript
const removeStyles = BetterCurseForge.injectCSS(`
  .addon-row { padding: 4px 8px !important; }
`);

// Later in cleanup:
plugin.onDisable = () => {
  removeStyles();
};
```

---

### 2. `BetterCurseForge.settings`
Stores and retrieves persistent settings saved to disk (`settings.json`):

```javascript
// Retrieve a stored setting (or null if not set)
const isCustomFont = await BetterCurseForge.settings.get('compactMode.customFont');

// Store a setting
await BetterCurseForge.settings.set('compactMode.density', 'ultra');
```

---

### 3. `BetterCurseForge.patcher`
Safe method monkey-patching for objects and functions:

#### `patcher.before(object, methodName, callback)`
Runs your callback before the target method executes. Receives `(args)`:

```javascript
const unpatch = BetterCurseForge.patcher.before(console, 'error', (args) => {
  console.warn('[Intercepted Console Error]', ...args);
});

plugin.onDisable = () => unpatch();
```

#### `patcher.after(object, methodName, callback)`
Runs after the target method completes. Receives `(args, result)`. You can return a modified value:

```javascript
const unpatch = BetterCurseForge.patcher.after(targetObj, 'getItemTitle', (args, result) => {
  return `⚡ ${result}`;
});

plugin.onDisable = () => unpatch();
```

#### `patcher.instead(object, methodName, callback)`
Completely supersedes the target method. Receives `(args, originalMethod)`:

```javascript
const unpatch = BetterCurseForge.patcher.instead(targetObj, 'fetchData', (args, originalFn) => {
  console.log('Intercepting fetchData call...');
  return originalFn(...args);
});

plugin.onDisable = () => unpatch();
```

---

### 4. `BetterCurseForge.on(event, callback)` / `.off()` / `.emit()`
Application-wide event emitter:

```javascript
const onReady = () => console.log('CurseForge UI is fully loaded!');

BetterCurseForge.on('ready', onReady);

plugin.onDisable = () => {
  BetterCurseForge.off('ready', onReady);
};
```

---

## Complete Example: Compact Mode Plugin

This plugin adds a high-density layout mode to CurseForge.

::: code-group

```json [manifest.json]
{
  "id": "compact-mode",
  "name": "Compact Mode",
  "version": "1.0.0",
  "description": "Reduces margins and padding for high-density modpack browsing.",
  "author": "BetterCurseForge Team",
  "main": "index.js",
  "styles": "styles.css"
}
```

```javascript [index.js]
// Add compact layout class to the document root
document.documentElement.classList.add('bcf-compact-layout');

console.log('[Compact Mode] Activated');

// Clean up when toggled off
plugin.onDisable = () => {
  document.documentElement.classList.remove('bcf-compact-layout');
  console.log('[Compact Mode] Deactivated');
};
```

```css [styles.css]
/* Automatically injected when plugin is enabled */
.bcf-compact-layout .tile-view-item {
  width: 150px !important;
  height: 240px !important;
}

.bcf-compact-layout .action-button-container {
  height: 48px !important;
  margin: 6px 0 !important;
}

.bcf-compact-layout .details-title {
  font-size: 13px !important;
}
```

:::