### Handle Closure Tree Errors Gracefully

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Manage potential failures during closure tree operations, including database errors, backend limitations, and invariant violations. This example demonstrates handling specific errors like `EmptyPath` and wrapped database errors.

```rust
use closure_tree::{ClosureTreeRepository, ClosureTreeError};
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Empty path returns an error
    match repo.find_or_create_by_path(&db, &[] as &[&str]).await {
        Err(ClosureTreeError::EmptyPath) => {
            println!("Cannot create path with no segments");
        }
        _ => panic!("Expected EmptyPath error"),
    }

    // Database errors are wrapped
    let invalid_db = Database::connect("postgres://invalid:5432/db").await;
    match invalid_db {
        Err(e) => println!("Connection failed: {}", e),
        _ => {}
    }

    // Successful operation returns the model
    match repo.find_or_create_by_path(&db, &["valid", "path"]).await {
        Ok(node) => println!("Created: {}", node.name),
        Err(ClosureTreeError::Database(db_err)) => {
            eprintln!("Database error: {}", db_err);
        }
        Err(ClosureTreeError::UnsupportedBackend) => {
            eprintln!("Only PostgreSQL is supported");
        }
        Err(e) => eprintln!("Other error: {}", e),
    }

    Ok(())
}

```

--------------------------------

### Query Parent and Children in Rust

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Navigate immediate hierarchical relationships using `parent` to get the direct parent of a node and `children` to retrieve all immediate children, both ordered by name. These methods require a valid node and database connection.

```rust
use closure_tree::ClosureTreeRepository;
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Create hierarchy
    repo.find_or_create_by_path(&db, &["parent", "child1"]).await?;
    repo.find_or_create_by_path(&db, &["parent", "child2"]).await?;
    let child1 = repo.find_by_path(&db, &["parent", "child1"]).await?.unwrap();

    // Get parent of a node
    let parent = repo.parent(&db, &child1).await?;
    if let Some(p) = parent {
        println!("Parent: {}", p.name);
        // Output: Parent: parent

        // Get all children of parent
        let children = repo.children(&db, &p).await?;
        let names: Vec<&str> = children.iter().map(|c| c.name.as_str()).collect();
        println!("Children: {:?}", names);
        // Output: Children: ["child1", "child2"]
    }

    // Root nodes have no parent
    let root = repo.find_by_path(&db, &["parent"]).await?.unwrap();
    let root_parent = repo.parent(&db, &root).await?;
    assert!(root_parent.is_none());

    Ok(())
}
```

--------------------------------

### Find Root Nodes in Rust

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

The `roots` method efficiently retrieves all top-level nodes that do not have any parent, effectively returning the starting points of all tree structures within the repository. This requires a database connection and a ClosureTreeRepository instance.

```rust
use closure_tree::ClosureTreeRepository;
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Create multiple root hierarchies
    repo.find_or_create_by_path(&db, &["documents", "2024"]).await?;
    repo.find_or_create_by_path(&db, &["photos", "vacation"]).await?;
    repo.find_or_create_by_path(&db, &["music", "rock"]).await?;

    // Get all root nodes
    let roots = repo.roots(&db).await?;
    let root_names: Vec<&str> = roots.iter().map(|r| r.name.as_str()).collect();
    println!("Roots: {:?}", root_names);
    // Output: Roots: ["documents", "music", "photos"]  // Ordered alphabetically

    assert_eq!(roots.len(), 3);

    Ok(())
}
```

--------------------------------

### Ensure Data Consistency with PostgreSQL Advisory Locks

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Utilize PostgreSQL advisory locks to prevent race conditions during concurrent node creation. The library automatically manages lock acquisition and release within transactions, ensuring data integrity. This example shows default lock behavior and how to inspect lock strategy.

```rust
use closure_tree::{
    ClosureTreeRepository,
    ClosureTreeConfig,
    ClosureTreeOptions,
    AdvisoryLockStrategy,
    AdvisoryLockKey
};
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Default behavior uses namespaced advisory locks
    // This is safe for concurrent calls from multiple processes
    let node1 = repo.find_or_create_by_path(&db, &["shared", "resource"]).await?;

    // Lock is automatically released after operation completes
    // Other processes can now acquire the lock

    // Configuration example (normally done via derive macro):
    let config = ClosureTreeConfig::new("MyEntity", "MyEntityHierarchy");
    let lock_strategy = config.advisory_lock_strategy();

    match lock_strategy {
        AdvisoryLockStrategy::Namespaced(key) => {
            println!("Using advisory lock: {}", key.as_str());
        }
        AdvisoryLockStrategy::Disabled => {
            println!("Advisory locks disabled (not recommended)");
        }
    }

    Ok(())
}

```

--------------------------------

### Query Descendants in Rust

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

The `descendants` method fetches all nodes that are descendants of a given node, excluding the node itself. The `self_and_descendants` variant includes the starting node. Both methods return results ordered by name and require a database connection and repository.

```rust
use closure_tree::ClosureTreeRepository;
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Build a tree structure
    repo.find_or_create_by_path(&db, &["root", "branch1", "leaf1"]).await?;
    repo.find_or_create_by_path(&db, &["root", "branch1", "leaf2"]).await?;
    repo.find_or_create_by_path(&db, &["root", "branch2", "leaf3"]).await?;

    let root = repo.find_by_path(&db, &["root"]).await?.unwrap();

    // Get all descendants (excluding root itself)
    let descendants = repo.descendants(&db, &root).await?;
    let names: Vec<&str> = descendants.iter().map(|n| n.name.as_str()).collect();
    println!("Descendants: {:?}", names);
    // Output: Descendants: ["branch1", "branch2", "leaf1", "leaf2", "leaf3"]

    // Include the node itself
    let all = repo.self_and_descendants(&db, &root).await?;
    assert_eq!(all.len(), 6);  // root + 5 descendants

    Ok(())
}
```

--------------------------------

### Find or Create Node by Path (Rust)

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Illustrates how to use the `find_or_create_by_path` method from `ClosureTreeRepository` to navigate or build tree structures. This method accepts a slice of path segments, ensures all nodes in the path exist (creating them if necessary), and returns the final node in the path. It utilizes PostgreSQL advisory locks to prevent race conditions during creation.

```rust
use closure_tree::ClosureTreeRepository;
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // Creates root -> child -> leaf hierarchy, returns the leaf node
    let leaf = repo
        .find_or_create_by_path(&db, &["root", "child", "leaf"])
        .await?;

    println!("Created node: {} with id {}", leaf.name, leaf.id);
    // Output: Created node: leaf with id 3

    // Calling again returns existing nodes without duplication
    let same_leaf = repo
        .find_or_create_by_path(&db, &["root", "child", "leaf"])
        .await?;

    assert_eq!(leaf.id, same_leaf.id);

    Ok(())
}
```

--------------------------------

### Development Commands (Shell)

Source: https://github.com/closuretree/closure-tree-rs/blob/master/README.md

This is a collection of standard Cargo commands used for development within the closure-tree Rust project. It includes commands for code formatting, linting, and running tests.

```shell
cargo fmt
cargo clippy --all-targets -- -D warnings
cargo test
```

--------------------------------

### Find or Create Node by Path (Rust)

Source: https://github.com/closuretree/closure-tree-rs/blob/master/README.md

This Rust code snippet illustrates how to use the `ClosureTreeRepository` to find a node based on its path or create it if it doesn't exist. It requires an active database connection and uses asynchronous operations.

```rust
use closure_tree::ClosureTreeRepository;
use closure_tree::ClosureTreeModelDerive as ClosureTreeModel;
use sea_orm::entity::prelude::*;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = sea_orm::Database::connect("postgres://...").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    let _leaf = repo
        .find_or_create_by_path(&db, &["root", "child", "leaf"])
        .await?;

    Ok(())
}

```

--------------------------------

### Create Database Schema for Closure Tree (Rust)

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Provides Rust code to set up the necessary PostgreSQL tables for the closure tree pattern: a `nodes` table for tree data and a `node_hierarchies` table for storing ancestor-descendant relationships. This function connects to a PostgreSQL database and executes SQL statements to create these tables if they don't exist.

```rust
use sea_orm::{Database, DatabaseConnection, DbBackend, Statement};

async fn setup_database() -> Result<DatabaseConnection, sea_orm::DbErr> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;

    // Create nodes table
    db.execute(Statement::from_string(
        DbBackend::Postgres,
        r#"
        CREATE TABLE IF NOT EXISTS nodes (
            id SERIAL PRIMARY KEY,
            parent_id INTEGER REFERENCES nodes(id) ON DELETE CASCADE,
            name TEXT NOT NULL
        );
        "#,
    )).await?;

    // Create hierarchy table for closure relationships
    db.execute(Statement::from_string(
        DbBackend::Postgres,
        r#"
        CREATE TABLE IF NOT EXISTS node_hierarchies (
            ancestor_id INTEGER NOT NULL REFERENCES nodes(id) ON DELETE CASCADE,
            descendant_id INTEGER NOT NULL REFERENCES nodes(id) ON DELETE CASCADE,
            generations INTEGER NOT NULL,
            PRIMARY KEY (ancestor_id, descendant_id)
        );
        "#,
    )).await?;

    Ok(db)
}
```

--------------------------------

### Define Closure Tree Models with Derive Macros (Rust)

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Demonstrates how to define node and hierarchy entities using SeaORM's derive macros, including the `ClosureTreeModel` macro for seamless integration with the closure tree pattern. This requires defining both a node entity and a hierarchy entity to track relationships.

```rust
use closure_tree::ClosureTreeModelDerive as ClosureTreeModel;
use sea_orm::entity::prelude::*;

// Node entity representing tree nodes
#[derive(Clone, Debug, PartialEq, DeriveEntityModel, ClosureTreeModel)]
#[sea_orm(table_name = "nodes")]
#[closure_tree(
    hierarchy_module = "crate::entity::node_hierarchy",
    hierarchy_table = "node_hierarchies"
)]
pub struct Model {
    #[sea_orm(primary_key)]
    pub id: i32,
    pub parent_id: Option<i32>,
    pub name: String,
}

#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
pub enum Relation {}

impl ActiveModelBehavior for ActiveModel {}

// Hierarchy entity tracking ancestor-descendant relationships
pub mod node_hierarchy {
    use sea_orm::entity::prelude::*;

    #[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
    #[sea_orm(table_name = "node_hierarchies")]
    pub struct Model {
        #[sea_orm(primary_key)]
        pub ancestor_id: i32,
        #[sea_orm(primary_key)]
        pub descendant_id: i32,
        pub generations: i32,  // Distance between ancestor and descendant
    }

    #[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
    pub enum Relation {}

    impl ActiveModelBehavior for ActiveModel {}
}
```

--------------------------------

### Define SeaORM Model with ClosureTree Derives (Rust)

Source: https://github.com/closuretree/closure-tree-rs/blob/master/README.md

This Rust code demonstrates how to define a SeaORM entity model for hierarchical data and derive the necessary traits for closure-tree integration. It includes the main model structure and attributes for closure-tree.

```rust
use closure_tree::ClosureTreeRepository;
use closure_tree::ClosureTreeModelDerive as ClosureTreeModel;
use sea_orm::entity::prelude::*;

#[derive(Clone, Debug, PartialEq, DeriveEntityModel, ClosureTreeModel)]
#[sea_orm(table_name = "nodes")]
#[closure_tree(hierarchy_module = "crate::entity::node_hierarchy", hierarchy_table = "node_hierarchies")]
pub struct Model {
    #[sea_orm(primary_key)]
    pub id: i32,
    pub parent_id: Option<i32>,
    pub name: String,
}

```

--------------------------------

### Add closure-tree Dependency (TOML)

Source: https://github.com/closuretree/closure-tree-rs/blob/master/README.md

This snippet shows how to add the closure-tree crate as a dependency to your Rust project using Cargo.toml. It specifies the version to be used.

```toml
[dependencies]
closure-tree = "0.0.1"
```

--------------------------------

### Find Nodes by Path in Rust

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

The `find_by_path` method allows retrieval of nodes by specifying a hierarchical path of names. It returns `None` if any part of the path is invalid. This function requires a database connection and a configured ClosureTreeRepository.

```rust
use closure_tree::ClosureTreeRepository;
use sea_orm::Database;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let db = Database::connect("postgres://user:pass@localhost:5432/mydb").await?;
    let repo = ClosureTreeRepository::<entity::node::Model>::new();

    // First create some nodes
    repo.find_or_create_by_path(&db, &["documents", "projects", "2024"]).await?;

    // Find an existing node
    let projects = repo
        .find_by_path(&db, &["documents", "projects"])
        .await?;
        // .expect("projects node should exist");

    // Uncomment the following lines to print the found project name
    // if let Some(projects_node) = projects {
    //     println!("Found: {}", projects_node.name);
    //     // Output: Found: projects
    // }

    // Non-existent path returns None
    let missing = repo
        .find_by_path(&db, &["documents", "missing", "path"])
        .await?;

    assert!(missing.is_none());

    Ok(())
}
```

--------------------------------

### Configure Closure Tree Options with Derive Macro Attributes

Source: https://context7.com/closuretree/closure-tree-rs/llms.txt

Customize field names and behavior for Closure Tree by using derive macro attributes. This allows specifying hierarchy module, table, parent field, name field, and ID field directly on the model.

```rust
use closure_tree::{ClosureTreeModelDerive as ClosureTreeModel, OrderStrategy};
use sea_orm::entity::prelude::*;

// Custom field names using macro attributes
#[derive(Clone, Debug, PartialEq, DeriveEntityModel, ClosureTreeModel)]
#[sea_orm(table_name = "categories")]
#[closure_tree(
    hierarchy_module = "crate::entity::category_hierarchy",
    hierarchy_table = "category_hierarchies",
    parent_field = "parent_category_id",
    name_field = "category_name",
    id_field = "category_id"
)]
pub struct Model {
    #[sea_orm(primary_key)]
    pub category_id: i32,
    pub parent_category_id: Option<i32>,
    pub category_name: String,
    pub sort_order: i32,
}

#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
pub enum Relation {}

impl ActiveModelBehavior for ActiveModel {}

// Access configuration at runtime
use closure_tree::ClosureTreeModel;

fn print_config() {
    let config = Model::closure_tree_config();
    println!("Parent column: {}", config.parent_column());
    println!("Name column: {}", config.name_column());
    println!("Hierarchy table: {}", config.hierarchy_table());
    // Output:
    // Parent column: parent_category_id
    // Name column: category_name
    // Hierarchy table: category_hierarchies
}

```

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