Title: Link Filter

Description: Filter entities by their relationships to other entities

Tags: features, filters, relationships

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Link Filter Feature Documentation

Overview

The Link Filter feature allows users to filter entities by their relationships to other entities. For example, you can filter all real estate properties that are linked to a specific contact like "Yannic Buchwald".

How It Works

Automatic Activation
The link filter automatically appears in the filter panel when:
The current entity type has linksConfiguration.enabled = true
The type has defined allowedTypes or relationships to other entity types

User Interface
The link filter provides a two-step selection process:
Type Selection: First dropdown allows you to select which type of entity you want to filter by (e.g., "Contacts")
Entity Selection: Second dropdown allows you to select the specific entity (e.g., "Yannic Buchwald")

Filter Logic
When a link filter is applied:
The system queries the relations collection to find all relationships involving the selected entity
It extracts the IDs of entities that are linked to the selected entity
The main data view is filtered to show only those linked entities

Example Use Cases

Real Estate and Contacts
Scenario: You have real estate properties linked to contacts (agents, owners, managers)
Usage: Filter all properties where "Yannic Buchwald" is linked as an agent
Result: Only properties with Yannic as a linked contact are displayed

Projects and Team Members
Scenario: You have projects linked to team members
Usage: Filter all projects where "John Doe" is assigned
Result: Only projects with John as a team member are displayed

Technical Implementation

Components
LinksFilterWidget.svelte: The main filter UI component
FilterComponent.svelte: Automatically includes links filter when appropriate
DataViewWidget.svelte: Handles the special links filtering logic

Database Queries
The filter converts to MongoDB queries that:
Query the relations collection: { "links.collectionName": targetType, "links.id": selectedEntityId }
Extract linked entity IDs from relations
Filter main collection: { id: { $in: [linkedEntityIds] } }

Translation Keys
widgets.dataView.filter.selectType: "Select type..."
widgets.dataView.filter.selectEntity: "Select entity..."

Configuration

Enabling Links for a Type
const myType: Type = {
  // ... other properties
  linksConfiguration: {
    enabled: true,
    allowedTypes: ["tenant-projectId-contactType"],
    descriptions: {
      "contactType": [
        { de: "Immobilienmakler", en: "Real Estate Agent" },
        { de: "Eigentümer", en: "Owner" }
      ]
    }
  }
};

Template Integration
The feature works seamlessly with existing templates like the Real Estate template, which already defines link configurations for contacts.

Testing

Unit Tests
Located in: packages/client/src/data-widgets/links/LinksFilterWidget.test.ts

E2E Tests
Located in: apps/backoffice/src/routes/projects/[projectId]/link-filter.e2e.ts

Manual Testing Steps
Create a project with the Real Estate template
Add some contacts (e.g., "Yannic Buchwald", "Max Mustermann") 
Add real estate properties and link them to contacts
Navigate to the real estate data view
Click the filter button to open filters
Look for "Verknüpfungen" (Links) filter
Select "Kontakte" in the first dropdown
Select a specific contact in the second dropdown
Verify only linked properties are displayed

Browser Compatibility
The feature uses standard web technologies and should work in all modern browsers that support the base application.