---
title: Hook Reference
description: Plugin hooks for extending EmDash functionality.
---

import { Aside } from "@astrojs/starlight/components";

Hooks allow plugins to intercept and modify EmDash behavior at specific points in the content and media lifecycle.

## Hook Overview

| Hook                   | Trigger                        | Can Modify    |
| ---------------------- | ------------------------------ | ------------- |
| `content:beforeSave`   | Before content is saved        | Content data  |
| `content:afterSave`    | After content is saved         | Nothing       |
| `content:beforeDelete` | Before content is deleted      | Can cancel    |
| `content:afterDelete`  | After content is deleted       | Nothing       |
| `media:beforeUpload`   | Before file is uploaded        | File metadata |
| `media:afterUpload`    | After file is uploaded         | Nothing       |
| `plugin:install`       | When plugin is first installed | Nothing       |
| `plugin:activate`      | When plugin is enabled         | Nothing       |
| `plugin:deactivate`    | When plugin is disabled        | Nothing       |
| `plugin:uninstall`     | When plugin is removed         | Nothing       |

## Content Hooks

### `content:beforeSave`

Runs before content is saved to the database. Use to validate, transform, or enrich content.

```ts
import { definePlugin } from "emdash";

export default definePlugin({
	id: "my-plugin",
	version: "1.0.0",
	hooks: {
		"content:beforeSave": async (event, ctx) => {
			const { content, collection, isNew } = event;

			// Add timestamps
			if (isNew) {
				content.createdBy = "system";
			}
			content.modifiedAt = new Date().toISOString();

			// Return modified content
			return content;
		},
	},
});
```

#### Event

```ts
interface ContentHookEvent {
	content: Record<string, unknown>; // Content data
	collection: string; // Collection slug
	isNew: boolean; // True for creates, false for updates
}
```

#### Return Value

- Return modified content object to apply changes
- Return `void` to pass through unchanged

### `content:afterSave`

Runs after content is saved. Use for side effects like notifications, cache invalidation, or external syncing.

```ts
hooks: {
  "content:afterSave": async (event, ctx) => {
    const { content, collection, isNew } = event;

    if (collection === "posts" && content.status === "published") {
      // Notify external service
      await ctx.http?.fetch("https://api.example.com/notify", {
        method: "POST",
        body: JSON.stringify({ postId: content.id }),
      });
    }
  },
}
```

#### Return Value

No return value expected.

### `content:beforeDelete`

Runs before content is deleted. Use to validate deletion or prevent it.

```ts
hooks: {
  "content:beforeDelete": async (event, ctx) => {
    const { id, collection } = event;

    // Prevent deletion of protected content
    const item = await ctx.content?.get(collection, id);
    if (item?.data.protected) {
      return false; // Cancel deletion
    }

    // Allow deletion
    return true;
  },
}
```

#### Event

```ts
interface ContentDeleteEvent {
	id: string; // Entry ID
	collection: string; // Collection slug
}
```

#### Return Value

- Return `false` to cancel deletion
- Return `true` or `void` to allow

### `content:afterDelete`

Runs after content is deleted. Use for cleanup tasks.

```ts
hooks: {
  "content:afterDelete": async (event, ctx) => {
    const { id, collection } = event;

    // Clean up related data
    await ctx.storage.relatedItems.delete(`${collection}:${id}`);
  },
}
```

## Media Hooks

### `media:beforeUpload`

Runs before a file is uploaded. Use to validate, rename, or reject files.

```ts
hooks: {
  "media:beforeUpload": async (event, ctx) => {
    const { file } = event;

    // Reject files over 10MB
    if (file.size > 10 * 1024 * 1024) {
      throw new Error("File too large");
    }

    // Rename file
    return {
      name: `${Date.now()}-${file.name}`,
      type: file.type,
      size: file.size,
    };
  },
}
```

#### Event

```ts
interface MediaUploadEvent {
	file: {
		name: string; // Original filename
		type: string; // MIME type
		size: number; // Size in bytes
	};
}
```

#### Return Value

- Return modified file metadata to apply changes
- Return `void` to pass through unchanged
- Throw to reject the upload

### `media:afterUpload`

Runs after a file is uploaded. Use for processing, thumbnails, or metadata extraction.

```ts
hooks: {
  "media:afterUpload": async (event, ctx) => {
    const { media } = event;

    if (media.mimeType.startsWith("image/")) {
      // Store image metadata
      await ctx.kv.set(`media:${media.id}:analyzed`, {
        processedAt: new Date().toISOString(),
      });
    }
  },
}
```

#### Event

```ts
interface MediaAfterUploadEvent {
	media: {
		id: string;
		filename: string;
		mimeType: string;
		size: number | null;
		url: string;
		createdAt: string;
	};
}
```

## Lifecycle Hooks

### `plugin:install`

Runs when a plugin is first installed. Use for initial setup, creating storage collections, or seeding data.

```ts
hooks: {
  "plugin:install": async (event, ctx) => {
    // Initialize default settings
    await ctx.kv.set("settings:enabled", true);
    await ctx.kv.set("settings:threshold", 100);

    ctx.log.info("Plugin installed successfully");
  },
}
```

### `plugin:activate`

Runs when a plugin is enabled (after install or re-enable).

```ts
hooks: {
  "plugin:activate": async (event, ctx) => {
    ctx.log.info("Plugin activated");
  },
}
```

### `plugin:deactivate`

Runs when a plugin is disabled.

```ts
hooks: {
  "plugin:deactivate": async (event, ctx) => {
    ctx.log.info("Plugin deactivated");
  },
}
```

### `plugin:uninstall`

Runs when a plugin is removed. Use for cleanup.

```ts
hooks: {
  "plugin:uninstall": async (event, ctx) => {
    const { deleteData } = event;

    if (deleteData) {
      // Clean up all plugin data
      const items = await ctx.kv.list("settings:");
      for (const { key } of items) {
        await ctx.kv.delete(key);
      }
    }

    ctx.log.info("Plugin uninstalled");
  },
}
```

#### Event

```ts
interface UninstallEvent {
	deleteData: boolean; // User chose to delete data
}
```

## Hook Configuration

Hooks accept either a handler function or a configuration object:

```ts
hooks: {
  // Simple handler
  "content:afterSave": async (event, ctx) => { ... },

  // With configuration
  "content:beforeSave": {
    priority: 50,        // Lower runs first (default: 100)
    timeout: 10000,      // Max execution time in ms (default: 5000)
    dependencies: [],    // Run after these plugins
    errorPolicy: "abort", // "continue" or "abort" (default)
    handler: async (event, ctx) => { ... },
  },
}
```

### Configuration Options

| Option         | Type       | Default   | Description                        |
| -------------- | ---------- | --------- | ---------------------------------- |
| `priority`     | `number`   | `100`     | Execution order (lower = earlier)  |
| `timeout`      | `number`   | `5000`    | Max execution time in milliseconds |
| `dependencies` | `string[]` | `[]`      | Plugin IDs that must run first     |
| `errorPolicy`  | `string`   | `"abort"` | `"continue"` to ignore errors      |

## Plugin Context

All hooks receive a context object with access to plugin APIs:

```ts
interface PluginContext {
	plugin: { id: string; version: string };
	storage: PluginStorage; // Declared storage collections
	kv: KVAccess; // Key-value store
	content?: ContentAccess; // If read:content or write:content capability
	media?: MediaAccess; // If read:media or write:media capability
	http?: HttpAccess; // If network:fetch capability
	log: LogAccess; // Always available
}
```

<Aside>
	Context APIs are gated by plugin capabilities. Declare required capabilities in the plugin
	definition.
</Aside>

## Error Handling

Errors in hooks are logged and handled based on `errorPolicy`:

- `"abort"` (default) — Stop execution, rollback transaction if applicable
- `"continue"` — Log error and continue to next hook

```ts
hooks: {
  "content:beforeSave": {
    errorPolicy: "continue", // Don't block save if this fails
    handler: async (event, ctx) => {
      try {
        await ctx.http?.fetch("https://api.example.com/validate");
      } catch (error) {
        ctx.log.warn("Validation service unavailable", error);
      }
    },
  },
}
```

## Execution Order

Hooks run in this order:

1. Sorted by `priority` (ascending)
2. Plugins with `dependencies` run after their dependencies
3. Within same priority, order is deterministic but unspecified

```ts
// This runs first (priority 10)
{ priority: 10, handler: ... }

// This runs second (priority 50)
{ priority: 50, handler: ... }

// This runs last (default priority 100)
{ handler: ... }
```
