# Resource System

The resource system is one of the most important architectural concepts in Chamilo 2.0. It provides a unified abstraction for all course content — documents, exercises, learning paths, forum posts, and more.

## Core Concept

Every piece of course content is represented by a **ResourceNode**. This gives all content types a common set of capabilities:

* **Visibility control** — Show/hide from learners
* **Access control** — Security voters check permissions via the ResourceNode
* **File storage** — Attached files are stored via ResourceFile
* **Tree structure** — ResourceNodes form a tree (parent-child relationships)
* **Audit trail** — Creator, creation date, modification tracking

## Key Entities

### ResourceNode (`src/CoreBundle/Entity/ResourceNode.php`)

The central entity. Every content entity has a one-to-one relationship with a ResourceNode.

Key fields:

| Field           | Type         | Description                                 |
| --------------- | ------------ | ------------------------------------------- |
| `id`            | integer      | Primary key                                 |
| `uuid`          | UUID v4      | Unique identifier for API use               |
| `title`         | string       | Display title                               |
| `creator`       | User         | The user who created this resource          |
| `resourceFile`  | ResourceFile | The attached file (if any)                  |
| `resourceType`  | ResourceType | The type of resource (document, quiz, etc.) |
| `parent`        | ResourceNode | Parent in the resource tree                 |
| `children`      | Collection   | Child ResourceNodes                         |
| `resourceLinks` | Collection   | Visibility and access links                 |

The tree uses Gedmo's **materialized path** strategy for efficient hierarchical queries.

### ResourceFile (`src/CoreBundle/Entity/ResourceFile.php`)

Stores the actual file data for a resource:

| Field          | Type    | Description            |
| -------------- | ------- | ---------------------- |
| `id`           | integer | Primary key            |
| `title`        | string  | Original filename      |
| `mimeType`     | string  | MIME type              |
| `originalName` | string  | Original upload name   |
| `size`         | integer | File size in bytes     |
| `crop`         | string  | Crop data (for images) |

File storage is handled by Flysystem, so files can be on local disk, S3, Azure, or GCS depending on configuration.

### ResourceLink

Controls visibility and access per context. There are 3 main context types:

1. Course
2. Session
3. Group (in a course)

So the ResourceLink entity reflects the combination of those 3 context types and establishes a visibility for that complete context:

| Field        | Type    | Description                          |
| ------------ | ------- | ------------------------------------ |
| `course`     | Course  | Which course the resource belongs to |
| `session`    | Session | Which session (null for base course) |
| `group`      | CGroup  | Which group (null for whole course)  |
| `visibility` | integer | Visible, invisible, or deleted       |

This allows the same ResourceNode to have different visibility in different contexts (e.g., visible in one session but hidden in another).

This is set automatically when using the interface and deciding, for example, that a resource is a session-specific resource which will be visible for all groups in a given course in a given session, but invisible in the base course or in another session.

By default, resources visible in a base course are also visible in all sessions of that course, but the course tutor can decide to hide a resource from a specific session. In this case, we will retrieve the specific visibility for this resource in this session and see that it has a visibility of 0, so the item will not appear to learners in this session, while a lack of session-specific visibility in other sessions will make the resource use the visibility of the base course (and the resource will show to learners).

## API Platform Integration

ResourceNode is exposed as an API Platform resource with security:

```php
#[ApiResource(
    operations: [
        new Get(security: "is_granted('VIEW', object)"),
        new Put(security: "is_granted('EDIT', object)"),
        new Delete(security: "is_granted('DELETE', object)"),
        new GetCollection(security: "is_granted('ROLE_USER')"),
    ]
)]
```

## How Content Entities Connect

Course content entities (CDocument, CQuiz, CLp, etc.) extend `AbstractResource` or implement `ResourceInterface`, which gives them a `resourceNode` relationship:

```php
// In CDocument entity:
#[ORM\OneToOne(targetEntity: ResourceNode::class)]
private ResourceNode $resourceNode;
```

When you create a CDocument, a ResourceNode is automatically created alongside it, providing unified resource management.

## Practical Implications

When working with course content:

1. **Creating content** — Create both the content entity AND its ResourceNode
2. **Checking permissions** — Use the ResourceNode's security voters
3. **Managing files** — Attach files through ResourceFile
4. **Controlling visibility** — Create/modify ResourceLinks
5. **Building trees** — Use the parent-child relationship on ResourceNode for folder structures (e.g., document folders)


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