Small example to show how to compose components (capabilities) in a Topology to simplify reusing existing components for different topologies

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "ambassador"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e68de4cdc6006162265d0957edb4a860fe4e711b1dc17a5746fd95f952f08285"
+dependencies = [
+ "itertools",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
+[[package]]
+name = "harmony-composable"
+version = "0.1.0"
+dependencies = [
+ "ambassador",
+]
+
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.103"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ee95bc4ef87b8d5ba32e8b7714ccc834865276eab0aed5c9958d00ec45f49e8"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.41"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce25767e7b499d1b604768e7cde645d14cc8584231ea6b295e9c9eb22c02e1d1"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"

Cargo.toml

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+[package]
+name = "harmony-composable"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+ambassador = "0.4.2"

src/components/mod.rs

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+pub mod network_manager;
+pub mod switch;

src/components/network_manager.rs

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+use ambassador::delegatable_trait;
+
+#[delegatable_trait]
+pub trait NetworkManager {
+    fn ensure_network_manager_installed(&self) -> Result<(), String>;
+    fn configure_bond(&self, bond: String) -> Result<(), String>;
+}

src/components/switch.rs

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+use ambassador::delegatable_trait;
+
+#[delegatable_trait]
+pub trait Switch {
+    fn setup_switch(&self) -> Result<(), String>;
+    fn create_port_channel(&self, port_channel: String) -> Result<(), String>;
+}

src/core/mod.rs

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+pub mod topology;

src/core/topology.rs

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+pub trait Topology {
+    fn name(&self) -> String;
+}

src/infra/brocade.rs

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+use crate::components::switch::Switch;
+
+pub struct BrocadeSwitch {}
+
+impl Switch for BrocadeSwitch {
+    fn setup_switch(&self) -> Result<(), String> {
+        println!("BrocadeSwitch: Installing...");
+        Ok(())
+    }
+
+    fn create_port_channel(&self, port_channel: String) -> Result<(), String> {
+        println!("BrocadeSwitch: Creating port channel {}", port_channel);
+        Ok(())
+    }
+}

src/infra/k8s_client.rs

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+pub struct Client {}

src/infra/mod.rs

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+pub mod brocade;
+pub mod k8s_client;
+pub mod nmcli;
+pub mod openshift;

src/infra/nmcli.rs

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+use crate::components::network_manager::NetworkManager;
+
+pub struct NmcliNetworkManager {}
+
+impl NetworkManager for NmcliNetworkManager {
+    fn ensure_network_manager_installed(&self) -> Result<(), String> {
+        println!("Nmcli: Installing...");
+        Ok(())
+    }
+
+    fn configure_bond(&self, bond: String) -> Result<(), String> {
+        println!("Nmcli: Configuring bond {}", bond);
+        Ok(())
+    }
+}

src/infra/openshift.rs

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+use std::sync::Arc;
+
+use crate::{components::network_manager::NetworkManager, infra::k8s_client};
+
+pub struct OpenShiftNmStateNetworkManager {
+    pub k8s_client: Arc<k8s_client::Client>,
+}
+
+impl NetworkManager for OpenShiftNmStateNetworkManager {
+    fn ensure_network_manager_installed(&self) -> Result<(), String> {
+        println!("OpenShift NM State: Installing...");
+
+        // self.k8s_client.apply(...)
+
+        Ok(())
+    }
+
+    fn configure_bond(&self, bond: String) -> Result<(), String> {
+        println!("OpenShift NM State: Configuring bond {}", bond);
+        Ok(())
+    }
+}

src/main.rs

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+use std::sync::Arc;
+
+use crate::{
+    components::{network_manager::NetworkManager, switch::Switch},
+    core::topology::Topology,
+    infra::brocade::BrocadeSwitch,
+    topologies::{k8s::NetworkManagerProvider, k8s_anywhere::K8sAnywhereTopology},
+};
+
+mod components;
+mod core;
+mod infra;
+mod topologies;
+
+fn configure_port_channel<T: Topology + Switch>(topology: &T) -> Result<(), String> {
+    println!(
+        "--- Running configure_port_channel for: {} ---",
+        topology.name()
+    );
+    topology.setup_switch()?;
+    topology.create_port_channel("pc-123".to_string())?;
+    Ok(())
+}
+
+fn configure_bond<T: Topology + NetworkManager>(topology: &T) -> Result<(), String> {
+    println!("--- Running configure_bond for: {} ---", topology.name());
+    topology.ensure_network_manager_installed()?;
+    topology.configure_bond("bond0".to_string())?;
+    Ok(())
+}
+
+fn main() {
+    let topology = K8sAnywhereTopology::new(NetworkManagerProvider {}, Arc::new(BrocadeSwitch {}));
+
+    // Simulate the execution of a Score's Interpret
+    configure_bond(&topology).unwrap();
+    configure_port_channel(&topology).unwrap();
+}

src/topologies/k8s.rs

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+use std::sync::Arc;
+
+use crate::{
+    components::network_manager::NetworkManager,
+    core::topology::Topology,
+    infra::{k8s_client, nmcli::NmcliNetworkManager, openshift::OpenShiftNmStateNetworkManager},
+};
+
+pub enum K8sSource {
+    K3dFamily,
+    OpenShiftFamily,
+}
+
+pub struct K8sState {
+    pub source: K8sSource,
+}
+
+pub trait K8sClient {
+    fn k8s_state(&self) -> K8sState;
+    fn k8s_client(&self) -> Arc<k8s_client::Client>;
+}
+
+pub struct NetworkManagerProvider {}
+
+impl NetworkManagerProvider {
+    pub fn provide<T: Topology + K8sClient>(&self, topology: &T) -> Arc<dyn NetworkManager> {
+        match topology.k8s_state().source {
+            K8sSource::K3dFamily => Arc::new(NmcliNetworkManager {}),
+            K8sSource::OpenShiftFamily => {
+                let k8s_client = topology.k8s_client().clone();
+                Arc::new(OpenShiftNmStateNetworkManager { k8s_client })
+            }
+        }
+    }
+}

src/topologies/k8s_anywhere.rs

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+use std::{cell::OnceCell, sync::Arc};
+
+use ambassador::delegate_to_methods;
+
+use crate::{
+    components::{
+        network_manager::{NetworkManager, ambassador_impl_NetworkManager},
+        switch::{Switch, ambassador_impl_Switch},
+    },
+    core::topology::Topology,
+    infra::k8s_client,
+    topologies::k8s::{K8sClient, K8sSource, K8sState, NetworkManagerProvider},
+};
+
+pub struct K8sAnywhereTopology {
+    network_manager_provider: NetworkManagerProvider,
+    network_manager: OnceCell<Arc<dyn NetworkManager>>,
+    switch: Arc<dyn Switch>,
+}
+
+#[delegate_to_methods]
+#[delegate(NetworkManager, target_ref = "network_manager")]
+#[delegate(Switch, target_ref = "switch")]
+impl K8sAnywhereTopology {
+    pub fn new(network_manager_provider: NetworkManagerProvider, switch: Arc<dyn Switch>) -> Self {
+        Self {
+            network_manager_provider,
+            network_manager: OnceCell::new(),
+            switch,
+        }
+    }
+
+    fn network_manager(&self) -> &dyn NetworkManager {
+        self.network_manager
+            .get_or_init(|| self.network_manager_provider.provide(self))
+            .as_ref()
+    }
+
+    fn switch(&self) -> &dyn Switch {
+        self.switch.as_ref()
+    }
+}
+
+impl Topology for K8sAnywhereTopology {
+    fn name(&self) -> String {
+        "K8sAnywhere".to_string()
+    }
+}
+
+impl K8sClient for K8sAnywhereTopology {
+    fn k8s_state(&self) -> K8sState {
+        K8sState {
+            source: K8sSource::OpenShiftFamily,
+        }
+    }
+
+    fn k8s_client(&self) -> Arc<k8s_client::Client> {
+        Arc::new(k8s_client::Client {})
+    }
+}

src/topologies/mod.rs

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+pub mod k8s;
+pub mod k8s_anywhere;