// api/networks.rs — Server functions for networks

use leptos::prelude::*;
use serde::{Deserialize, Serialize};

use crate::models::Network;

// Network row augmented with pre-computed counts.
// Defined here (not in models.rs) because it is a presentation model
// specific to the Networks page, not a pure domain entity.
#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct NetworkWithCounts {
    pub id: i64,
    pub cidr: String,
    /// Number of hosts whose IP falls within this network's CIDR range.
    pub host_count: i64,
    /// Number of distinct applications linked via ports open on hosts in this network.
    pub application_count: i64,
}

// ─── Queries ──────────────────────────────────────────────────────────────────

/// Returns all networks from the database.
///
/// Called by the Networks page to populate the list.
#[server]
pub async fn get_networks() -> Result<Vec<Network>, ServerFnError> {
    use sqlx::AnyPool;
    use crate::server::repository::networks as repo;

    // `use_context` retrieves a value previously registered with `provide_context`.
    // The pool was injected in main.rs before every request.
    // `ok_or_else` converts `None` into an error (defensive: should never happen).
    let pool = use_context::<AnyPool>()
        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;

    // Propagate any DB error as a ServerFnError so the client sees a clean message.
    repo::list_networks(&pool)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))
}

/// Returns all networks enriched with host and application counts.
///
/// A single SQL query fetches everything at once using correlated subqueries,
/// avoiding N+1 round-trips regardless of the number of networks.
///
/// `application_count` = distinct applications whose registered ports appear
/// among the ports open on hosts in each network (via host_ports → application_ports).
#[server]
pub async fn get_networks_with_counts() -> Result<Vec<NetworkWithCounts>, ServerFnError> {
    use sqlx::{AnyPool, Row};

    let pool = use_context::<AnyPool>()
        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;

    let rows = sqlx::query(
        "SELECT
            n.id,
            n.cidr,
            (SELECT COUNT(*) FROM hosts WHERE network_id = n.id) AS host_count,
            (SELECT COUNT(DISTINCT ap.application_id)
               FROM hosts h
               JOIN host_ports hp ON hp.host_id = h.id
               JOIN application_ports ap ON ap.port_number = hp.port_number
              WHERE h.network_id = n.id) AS application_count
         FROM networks n
         ORDER BY n.id",
    )
    .fetch_all(&pool)
    .await
    .map_err(|e| ServerFnError::new(e.to_string()))?;

    let networks = rows
        .into_iter()
        .map(|row| NetworkWithCounts {
            id:                row.get("id"),
            cidr:              row.get("cidr"),
            host_count:        row.get("host_count"),
            application_count: row.get("application_count"),
        })
        .collect();

    Ok(networks)
}

// ─── Mutations ────────────────────────────────────────────────────────────────

/// Creates a new network with the given CIDR block.
///
/// Returns the created record (with its auto-generated id).
/// Returns an error if the CIDR is malformed or already exists.
#[server]
pub async fn create_network(cidr: String) -> Result<Network, ServerFnError> {
    use sqlx::AnyPool;
    use crate::server::{repository::networks as repo, validation::validate_cidr};

    let pool = use_context::<AnyPool>()
        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;

    // Validate the CIDR before touching the database.
    // Example of a valid CIDR: "192.168.1.0/24"
    validate_cidr(&cidr).map_err(|e| ServerFnError::new(e.to_string()))?;

    repo::create_network(&pool, &cidr)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))
}

/// Deletes a network by id.
///
/// Also deletes all hosts in that network (via `ON DELETE CASCADE`).
/// Returns `true` if the network existed and was deleted.
#[server]
pub async fn delete_network(id: i64) -> Result<bool, ServerFnError> {
    use sqlx::AnyPool;
    use crate::server::repository::networks as repo;

    let pool = use_context::<AnyPool>()
        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;

    repo::delete_network(&pool, id)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))
}