Add documentation: Advanced Data Sources Guide

docs/Advanced Data Sources Guide.md

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+# Advanced Data Sources Guide
+
+**Description:** This document provides in-depth information on the `data_sources` module, covering advanced features such as data collections, conditional variables, and data transformers. It is designed to help you leverage these features for dynamic content management.
+
+**Target Audience:** Developers, System Architects, Content Managers
+
+## Table of Contents
+
+1.  [Data Collections](#data-collections)
+    *   [Defining Data Collections](#defining-data-collections)
+    *   [Accessing Data Collections](#accessing-data-collections)
+    *   [Data Collection Operations](#data-collection-operations)
+2.  [Conditional Variables](#conditional-variables)
+    *   [Defining Conditional Variables](#defining-conditional-variables)
+    *   [Using Conditional Variables](#using-conditional-variables)
+    *   [Conditional Variable Examples](#conditional-variable-examples)
+3.  [Data Transformers](#data-transformers)
+    *   [Built-in Data Transformers](#built-in-data-transformers)
+    *   [Custom Data Transformers](#custom-data-transformers)
+    *   [Applying Data Transformers](#applying-data-transformers)
+4.  [Integration Examples](#integration-examples)
+    *   [Example 1: Dynamic Content Display](#example-1-dynamic-content-display)
+    *   [Example 2: Personalized User Experience](#example-2-personalized-user-experience)
+5.  [Best Practices](#best-practices)
+    *   [Data Source Design](#data-source-design)
+    *   [Performance Optimization](#performance-optimization)
+    *   [Security Considerations](#security-considerations)
+
+## 1. Data Collections
+
+Data collections allow you to group related data records together, enabling efficient management and retrieval of data.
+
+### Defining Data Collections
+
+Data collections are defined using a specific configuration format.  The exact format depends on the underlying data source implementation.  Here's a conceptual example:
+
+```json
+{
+  "name": "products",
+  "description": "A collection of product data",
+  "source": "database",
+  "query": "SELECT * FROM products",
+  "fields": [
+    {"name": "id", "type": "integer"},
+    {"name": "name", "type": "string"},
+    {"name": "price", "type": "number"}
+  ]
+}
+```
+
+This example defines a data collection named "products" that retrieves data from a database table.  The `fields` array describes the structure of each data record in the collection.
+
+### Accessing Data Collections
+
+Data collections can be accessed programmatically using the `data_sources` module.
+
+```python
+from data_sources import get_data_collection
+
+products = get_data_collection("products")
+
+for product in products:
+  print(f"Product Name: {product['name']}, Price: {product['price']}")
+```
+
+This code snippet retrieves the "products" data collection and iterates through each record, printing the product name and price.
+
+### Data Collection Operations
+
+Common operations on data collections include:
+
+*   **Filtering:** Selecting specific records based on criteria.
+*   **Sorting:** Ordering records based on a field.
+*   **Pagination:** Dividing the collection into smaller pages for efficient display.
+
+Example of filtering:
+
+```python
+from data_sources import get_data_collection
+
+products = get_data_collection("products")
+
+# Filter products with price greater than 50
+filtered_products = [p for p in products if p['price'] > 50]
+
+for product in filtered_products:
+  print(f"Product Name: {product['name']}, Price: {product['price']}")
+```
+
+## 2. Conditional Variables
+
+Conditional variables allow you to dynamically adjust content based on specific conditions.  This enables personalized experiences and context-aware content delivery.
+
+### Defining Conditional Variables
+
+Conditional variables are defined with a name, a condition, and a value to be used when the condition is met.
+
+```json
+{
+  "name": "is_premium_user",
+  "condition": "user.membership_level == 'premium'",
+  "value": true
+}
+```
+
+This example defines a conditional variable named "is\_premium\_user" that evaluates to `true` if the user's membership level is "premium".
+
+### Using Conditional Variables
+
+Conditional variables can be used in templates or code to control content display or application behavior.
+
+```html
+{% if is_premium_user %}
+  <p>Welcome, premium user! You have access to exclusive content.</p>
+{% else %}
+  <p>Upgrade to premium for exclusive access!</p>
+{% endif %}
+```
+
+This example uses the "is\_premium\_user" variable in a template to display different content based on the user's membership level.
+
+### Conditional Variable Examples
+
+| Variable Name       | Condition                               | Value (if true) | Description                                                                 |
+| --------------------- | --------------------------------------- | --------------- | --------------------------------------------------------------------------- |
+| `is_logged_in`      | `user.is_authenticated`                 | `true`          | Indicates whether the user is logged in.                                    |
+| `device_is_mobile`  | `device.type == 'mobile'`               | `true`          | Indicates whether the user is accessing the site from a mobile device.       |
+| `user_age_over_18`  | `user.age >= 18`                        | `true`          | Indicates whether the user is over 18 years old.                             |
+| `is_weekend`        | `datetime.datetime.now().weekday() > 4` | `true`          | Indicates whether it is the weekend (Saturday or Sunday).                   |
+
+## 3. Data Transformers
+
+Data transformers allow you to modify data before it is displayed or used in your application. This can be useful for formatting dates, converting currencies, or performing other data manipulations.
+
+### Built-in Data Transformers
+
+The `data_sources` module provides several built-in data transformers for common data manipulation tasks. Examples include:
+
+*   `date_format`: Formats a date value.
+*   `currency_format`: Formats a currency value.
+*   `uppercase`: Converts a string to uppercase.
+*   `lowercase`: Converts a string to lowercase.
+
+### Custom Data Transformers
+
+You can also create custom data transformers to perform specific data manipulations.  This typically involves defining a function that takes the data as input and returns the transformed data.
+
+```python
+def custom_transformer(data):
+  """
+  Example custom data transformer that adds a prefix to a string.
+  """
+  return "PREFIX_" + str(data)
+
+# Register the custom transformer (implementation specific)
+# register_transformer("add_prefix", custom_transformer)
+```
+
+### Applying Data Transformers
+
+Data transformers are applied to data fields using a specific configuration format.
+
+```json
+{
+  "field": "date",
+  "transformer": "date_format",
+  "options": {"format": "%Y-%m-%d"}
+}
+```
+
+This example applies the `date_format` transformer to the "date" field, formatting it as "YYYY-MM-DD".
+
+Example of applying a custom transformer:
+
+```json
+{
+  "field": "product_name",
+  "transformer": "add_prefix"
+}
+```
+
+## 4. Integration Examples
+
+### Example 1: Dynamic Content Display
+
+This example demonstrates how to use data collections and conditional variables to dynamically display content based on user roles.
+
+```python
+from data_sources import get_data_collection, get_variable
+
+articles = get_data_collection("articles")
+is_admin = get_variable("is_admin")
+
+if is_admin:
+  # Display all articles
+  for article in articles:
+    print(f"Title: {article['title']}, Content: {article['content']}")
+else:
+  # Display only published articles
+  published_articles = [a for a in articles if a['status'] == 'published']
+  for article in published_articles:
+    print(f"Title: {article['title']}, Content: {article['content']}")
+```
+
+### Example 2: Personalized User Experience
+
+This example demonstrates how to use data transformers to personalize the user experience by formatting dates and currencies based on the user's locale.
+
+```python
+from data_sources import get_data_collection
+
+products = get_data_collection("products")
+
+for product in products:
+  formatted_price = currency_format(product['price'], locale=user.locale) # Assuming currency_format is available and user.locale exists
+  print(f"Product Name: {product['name']}, Price: {formatted_price}")
+```
+
+## 5. Best Practices
+
+### Data Source Design
+
+*   **Choose the right data source:** Select a data source that is appropriate for the type of data you are managing.
+*   **Design efficient queries:** Optimize your queries to retrieve data quickly and efficiently.
+*   **Use data caching:** Cache frequently accessed data to improve performance.
+
+### Performance Optimization
+
+*   **Minimize data transfers:** Only retrieve the data that you need.
+*   **Use data compression:** Compress data to reduce transfer times.
+*   **Optimize data transformations:** Ensure that your data transformations are efficient.
+
+### Security Considerations
+
+*   **Sanitize user input:** Prevent SQL injection and other security vulnerabilities.
+*   **Secure data access:** Restrict access to sensitive data.
+*   **Encrypt sensitive data:** Encrypt sensitive data at rest and in transit.
+
+**Related Endpoints:**
+
+*   `/dataSources/index`
+*   `/dataSources/model/DataSource`
+*   `/dataSources/model/DataRecord`