doc: add more information to README.md

README.md

@@ -1,6 +1,12 @@
 # heave 󱅝
 
-A Rust EAV data model implementation
+A Rust EAV data model implementation.
+
+Heave is a Rust library that provides a flexible and extensible implementation of the Entity-Attribute-Value (EAV) data model. It allows you to manage data with a dynamic schema, making it suitable for scenarios where attributes of entities are not known at compile time. The library includes support for persisting the EAV data to a SQLite database.
+
+## Typed Entities
+
+Typed entities may be used leveraging the `EAV` trait to map to and from schemaless entities.
 
 ## EAV
 
@@ -22,7 +28,105 @@ Learn more on EAV data model [here](https://en.wikipedia.org/wiki/Entity%E2%80%9
 
 ## Example
 
-...
+Here is an example of how to define a typed entity, persist it to a SQLite database, and load it back.
+
+```rust
+use heave::{Catalog, EAV, Entity};
+use std::fs;
+
+// Define a typed entity.
+#[derive(Clone, Debug, PartialEq)]
+struct Product {
+    id: String,
+    name: String,
+    model: Option<String>,
+    price: u64,
+    in_stock: bool,
+}
+
+// Implement the EAV trait to define the class of the entity.
+impl EAV for Product {
+    fn class() -> &'static str {
+        "product"
+    }
+}
+
+// Implement From<Entity> to map a schemaless entity to a typed one.
+impl From<Entity> for Product {
+    fn from(entity: Entity) -> Self {
+        Product {
+            id: entity.id.clone(),
+            name: entity.unwrap("name"),
+            model: entity.unwrap_opt("model"),
+            price: entity.unwrap_or("price", 0),
+            in_stock: entity.unwrap("in_stock"),
+        }
+    }
+}
+
+// Implement From<Product> to map a typed entity to a schemaless one.
+impl From<Product> for Entity {
+    fn from(value: Product) -> Self {
+        let mut entity = Entity::new::<Product>()
+            .with_id(&value.id)
+            .with_attribute("name", value.name)
+            .with_attribute("price", value.price)
+            .with_attribute("in_stock", value.in_stock);
+        if let Some(model) = value.model {
+            entity.set("model", model);
+        }
+        entity
+    }
+}
+
+fn main() {
+    let db_path = "example.db";
+
+    // Initialize a new catalog and database.
+    let mut catalog = Catalog::new(db_path);
+    catalog.init();
+
+    // Create a new typed object.
+    let product = Product {
+        id: "prod-123".to_string(),
+        name: String::from("PenguinX Laptop"),
+        model: None,
+        price: 135000,
+        in_stock: true,
+    };
+    let product_id = product.id.clone();
+
+    // Insert the object and persist it to the database.
+    catalog.insert(product);
+    catalog.persist();
+
+    // Create a new catalog to simulate a different application instance.
+    let mut new_catalog = Catalog::new(db_path);
+
+    // Load the entity from the database.
+    new_catalog.load_by_id(&product_id);
+
+    // Retrieve the typed object from the catalog.
+    let read_product = new_catalog.get::<Product>(&product_id).unwrap();
+
+    println!("Successfully persisted and loaded: {:?}", read_product);
+
+    // Clean up the database file.
+    fs::remove_file(db_path).unwrap();
+}
+```
+
+## Contributing
+
+Contributions are welcome! If you'd like to contribute to heave, please follow these steps:
+
+1. Fork the repository.
+2. Create a new branch for your feature or bug fix.
+3. Make your changes and commit them with a clear message.
+4. Push your branch to your fork.
+5. Open a pull request to the main repository.
+
+Please ensure that your code adheres to the existing style and that all tests pass before submitting a pull request.
 
 ## Credits