handler.rs

//! Handler trait and utilities
//!
//! This module provides the [`Handler`] trait and related types for defining
//! HTTP request handlers in RustAPI.
//!
//! # Handler Functions
//!
//! Any async function that takes extractors as parameters and returns a type
//! implementing [`IntoResponse`] can be used as a handler:
//!
//! ```rust,ignore
//! use rustapi_core::{Json, Path, IntoResponse};
//! use serde::{Deserialize, Serialize};
//!
//! // No parameters
//! async fn hello() -> &'static str {
//!     "Hello, World!"
//! }
//!
//! // With extractors
//! async fn get_user(Path(id): Path<i64>) -> Json<User> {
//!     Json(User { id, name: "Alice".to_string() })
//! }
//!
//! // Multiple extractors (up to 5 supported)
//! async fn create_user(
//!     State(db): State<DbPool>,
//!     Json(body): Json<CreateUser>,
//! ) -> Result<Created<User>, ApiError> {
//!     // ...
//! }
//! ```
//!
//! # Route Helpers
//!
//! The module provides helper functions for creating routes with metadata:
//!
//! ```rust,ignore
//! use rustapi_core::handler::{get_route, post_route};
//!
//! let get = get_route("/users", list_users);
//! let post = post_route("/users", create_user);
//! ```
//!
//! # Macro-Based Routing
//!
//! For more ergonomic routing, use the `#[rustapi::get]`, `#[rustapi::post]`, etc.
//! macros from `rustapi-macros`:
//!
//! ```rust,ignore
//! #[rustapi::get("/users/{id}")]
//! async fn get_user(Path(id): Path<i64>) -> Json<User> {
//!     // ...
//! }
//! ```

use crate::extract::FromRequest;
use crate::request::Request;
use crate::response::{IntoResponse, Response};
use rustapi_openapi::{Operation, OperationModifier, ResponseModifier};
use std::future::Future;
use std::marker::PhantomData;
use std::pin::Pin;

mod sealed {
    pub trait Sealed {}

    impl<T> Sealed for T where T: Clone + Send + Sync + Sized + 'static {}
}

/// Trait representing an async handler function
pub trait Handler<T>: sealed::Sealed + Clone + Send + Sync + Sized + 'static {
    /// The response type
    type Future: Future<Output = Response> + Send + 'static;

    /// Call the handler with the request
    fn call(self, req: Request) -> Self::Future;

    /// Update the OpenAPI operation
    fn update_operation(op: &mut Operation);

    /// Register any OpenAPI components referenced by this handler.
    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec);
}

/// Wrapper to convert a Handler into a tower Service
pub struct HandlerService<H, T> {
    handler: H,
    _marker: PhantomData<fn() -> T>,
}

impl<H, T> HandlerService<H, T> {
    pub fn new(handler: H) -> Self {
        Self {
            handler,
            _marker: PhantomData,
        }
    }
}

impl<H: Clone, T> Clone for HandlerService<H, T> {
    fn clone(&self) -> Self {
        Self {
            handler: self.handler.clone(),
            _marker: PhantomData,
        }
    }
}

// Implement Handler for async functions with 0-6 extractors

// 0 args
impl<F, Fut, Res> Handler<()> for F
where
    F: FnOnce() -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, _req: Request) -> Self::Future {
        Box::pin(async move { self().await.into_response() })
    }

    fn update_operation(op: &mut Operation) {
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        Res::register_components(spec);
    }
}

// 1 arg
impl<F, Fut, Res, T1> Handler<(T1,)> for F
where
    F: FnOnce(T1) -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
    T1: FromRequest + OperationModifier + Send + 'static,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, mut req: Request) -> Self::Future {
        Box::pin(async move {
            let t1 = match T1::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            self(t1).await.into_response()
        })
    }

    fn update_operation(op: &mut Operation) {
        T1::update_operation(op);
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        T1::register_components(spec);
        Res::register_components(spec);
    }
}

// 2 args
impl<F, Fut, Res, T1, T2> Handler<(T1, T2)> for F
where
    F: FnOnce(T1, T2) -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
    T1: FromRequest + OperationModifier + Send + 'static,
    T2: FromRequest + OperationModifier + Send + 'static,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, mut req: Request) -> Self::Future {
        Box::pin(async move {
            let t1 = match T1::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t2 = match T2::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            self(t1, t2).await.into_response()
        })
    }

    fn update_operation(op: &mut Operation) {
        T1::update_operation(op);
        T2::update_operation(op);
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        T1::register_components(spec);
        T2::register_components(spec);
        Res::register_components(spec);
    }
}

// 3 args
impl<F, Fut, Res, T1, T2, T3> Handler<(T1, T2, T3)> for F
where
    F: FnOnce(T1, T2, T3) -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
    T1: FromRequest + OperationModifier + Send + 'static,
    T2: FromRequest + OperationModifier + Send + 'static,
    T3: FromRequest + OperationModifier + Send + 'static,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, mut req: Request) -> Self::Future {
        Box::pin(async move {
            let t1 = match T1::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t2 = match T2::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t3 = match T3::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            self(t1, t2, t3).await.into_response()
        })
    }

    fn update_operation(op: &mut Operation) {
        T1::update_operation(op);
        T2::update_operation(op);
        T3::update_operation(op);
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        T1::register_components(spec);
        T2::register_components(spec);
        T3::register_components(spec);
        Res::register_components(spec);
    }
}

// 4 args
impl<F, Fut, Res, T1, T2, T3, T4> Handler<(T1, T2, T3, T4)> for F
where
    F: FnOnce(T1, T2, T3, T4) -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
    T1: FromRequest + OperationModifier + Send + 'static,
    T2: FromRequest + OperationModifier + Send + 'static,
    T3: FromRequest + OperationModifier + Send + 'static,
    T4: FromRequest + OperationModifier + Send + 'static,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, mut req: Request) -> Self::Future {
        Box::pin(async move {
            let t1 = match T1::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t2 = match T2::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t3 = match T3::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t4 = match T4::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            self(t1, t2, t3, t4).await.into_response()
        })
    }

    fn update_operation(op: &mut Operation) {
        T1::update_operation(op);
        T2::update_operation(op);
        T3::update_operation(op);
        T4::update_operation(op);
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        T1::register_components(spec);
        T2::register_components(spec);
        T3::register_components(spec);
        T4::register_components(spec);
        Res::register_components(spec);
    }
}

// 5 args
impl<F, Fut, Res, T1, T2, T3, T4, T5> Handler<(T1, T2, T3, T4, T5)> for F
where
    F: FnOnce(T1, T2, T3, T4, T5) -> Fut + Clone + Send + Sync + 'static,
    Fut: Future<Output = Res> + Send + 'static,
    Res: IntoResponse + ResponseModifier,
    T1: FromRequest + OperationModifier + Send + 'static,
    T2: FromRequest + OperationModifier + Send + 'static,
    T3: FromRequest + OperationModifier + Send + 'static,
    T4: FromRequest + OperationModifier + Send + 'static,
    T5: FromRequest + OperationModifier + Send + 'static,
{
    type Future = Pin<Box<dyn Future<Output = Response> + Send>>;

    fn call(self, mut req: Request) -> Self::Future {
        Box::pin(async move {
            let t1 = match T1::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t2 = match T2::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t3 = match T3::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t4 = match T4::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            let t5 = match T5::from_request(&mut req).await {
                Ok(v) => v,
                Err(e) => return e.into_response(),
            };
            self(t1, t2, t3, t4, t5).await.into_response()
        })
    }

    fn update_operation(op: &mut Operation) {
        T1::update_operation(op);
        T2::update_operation(op);
        T3::update_operation(op);
        T4::update_operation(op);
        T5::update_operation(op);
        Res::update_response(op);
    }

    fn register_components(spec: &mut rustapi_openapi::OpenApiSpec) {
        T1::register_components(spec);
        T2::register_components(spec);
        T3::register_components(spec);
        T4::register_components(spec);
        T5::register_components(spec);
        Res::register_components(spec);
    }
}

// Type-erased handler for storage in router
pub(crate) type BoxedHandler =
    std::sync::Arc<dyn Fn(Request) -> Pin<Box<dyn Future<Output = Response> + Send>> + Send + Sync>;

/// Create a boxed handler from any Handler
pub(crate) fn into_boxed_handler<H, T>(handler: H) -> BoxedHandler
where
    H: Handler<T>,
    T: 'static,
{
    std::sync::Arc::new(move |req| {
        let handler = handler.clone();
        Box::pin(async move { handler.call(req).await })
    })
}

/// Trait for handlers with route metadata (generated by `#[rustapi::get]`, etc.)
///
/// This trait provides the path and method information for a handler,
/// allowing `.mount(handler)` to automatically register the route.
pub trait RouteHandler<T>: Handler<T> {
    /// The path pattern for this route (e.g., "/users/{id}")
    const PATH: &'static str;
    /// The HTTP method for this route (e.g., "GET")
    const METHOD: &'static str;
}

/// Represents a route definition that can be registered with .mount()
pub struct Route {
    pub(crate) path: &'static str,
    pub(crate) method: &'static str,
    pub(crate) handler: BoxedHandler,
    pub(crate) operation: Operation,
    pub(crate) component_registrar: fn(&mut rustapi_openapi::OpenApiSpec),
    /// Custom parameter schemas for OpenAPI (param_name -> schema_type)
    /// Supported types: "uuid", "integer", "string", "boolean", "number"
    pub(crate) param_schemas: std::collections::BTreeMap<String, String>,
    /// Custom error responses for OpenAPI (status_code -> description)
    pub(crate) error_responses: Vec<(u16, String)>,
}

impl Route {
    /// Create a new route from a handler with path and method
    pub fn new<H, T>(path: &'static str, method: &'static str, handler: H) -> Self
    where
        H: Handler<T>,
        T: 'static,
    {
        let mut operation = Operation::new();
        H::update_operation(&mut operation);

        Self {
            path,
            method,
            handler: into_boxed_handler(handler),
            operation,
            component_registrar: <H as Handler<T>>::register_components,
            param_schemas: std::collections::BTreeMap::new(),
            error_responses: Vec::new(),
        }
    }
    /// Set the operation summary
    pub fn summary(mut self, summary: impl Into<String>) -> Self {
        self.operation = self.operation.summary(summary);
        self
    }

    /// Set the operation description
    pub fn description(mut self, description: impl Into<String>) -> Self {
        self.operation = self.operation.description(description);
        self
    }

    /// Add a tag to the operation
    pub fn tag(mut self, tag: impl Into<String>) -> Self {
        self.operation.tags.push(tag.into());
        self
    }

    /// Get the route path
    pub fn path(&self) -> &str {
        self.path
    }

    /// Get the route method
    pub fn method(&self) -> &str {
        self.method
    }

    /// Set a custom OpenAPI schema type for a path parameter
    ///
    /// This is useful for overriding the auto-inferred type, e.g., when
    /// a parameter named `id` is actually a UUID instead of an integer.
    ///
    /// # Supported schema types
    /// - `"uuid"` - String with UUID format
    /// - `"integer"` or `"int"` - Integer with int64 format
    /// - `"string"` - Plain string
    /// - `"boolean"` or `"bool"` - Boolean
    /// - `"number"` - Number (float)
    ///
    /// # Example
    ///
    /// ```rust,ignore
    /// #[rustapi::get("/users/{id}")]
    /// async fn get_user(Path(id): Path<Uuid>) -> Json<User> {
    ///     // ...
    /// }
    ///
    /// // In route registration:
    /// get_route("/users/{id}", get_user).param("id", "uuid")
    /// ```
    pub fn param(mut self, name: impl Into<String>, schema_type: impl Into<String>) -> Self {
        self.param_schemas.insert(name.into(), schema_type.into());
        self
    }

    /// Get the custom parameter schemas
    pub fn param_schemas(&self) -> &std::collections::BTreeMap<String, String> {
        &self.param_schemas
    }

    /// Add a typed error response to the OpenAPI specification for this route
    ///
    /// This adds an error response entry to the operation's responses map,
    /// referencing the standard `ErrorSchema` component.
    ///
    /// # Arguments
    ///
    /// * `status` - HTTP status code (e.g., 404, 403, 409)
    /// * `description` - Human-readable description of when this error occurs
    ///
    /// # Example
    ///
    /// ```rust,ignore
    /// get_route("/users/{id}", get_user)
    ///     .error_response(404, "User not found")
    ///     .error_response(403, "Forbidden - insufficient permissions")
    /// ```
    pub fn error_response(mut self, status: u16, description: impl Into<String>) -> Self {
        let desc = description.into();
        self.error_responses.push((status, desc.clone()));

        // Also add directly to the operation's responses
        let mut content = std::collections::BTreeMap::new();
        content.insert(
            "application/json".to_string(),
            rustapi_openapi::MediaType {
                schema: Some(rustapi_openapi::SchemaRef::Ref {
                    reference: "#/components/schemas/ErrorSchema".to_string(),
                }),
                example: None,
            },
        );

        self.operation.responses.insert(
            status.to_string(),
            rustapi_openapi::ResponseSpec {
                description: desc,
                content,
                headers: std::collections::BTreeMap::new(),
            },
        );

        self
    }

    /// Get the custom error responses
    pub fn error_responses(&self) -> &[(u16, String)] {
        &self.error_responses
    }
}

/// Helper macro to create a Route from a handler with RouteHandler trait
#[macro_export]
macro_rules! route {
    ($handler:ident) => {{
        $crate::Route::new($handler::PATH, $handler::METHOD, $handler)
    }};
}

/// Create a GET route
pub fn get_route<H, T>(path: &'static str, handler: H) -> Route
where
    H: Handler<T>,
    T: 'static,
{
    Route::new(path, "GET", handler)
}

/// Create a POST route
pub fn post_route<H, T>(path: &'static str, handler: H) -> Route
where
    H: Handler<T>,
    T: 'static,
{
    Route::new(path, "POST", handler)
}

/// Create a PUT route
pub fn put_route<H, T>(path: &'static str, handler: H) -> Route
where
    H: Handler<T>,
    T: 'static,
{
    Route::new(path, "PUT", handler)
}

/// Create a PATCH route
pub fn patch_route<H, T>(path: &'static str, handler: H) -> Route
where
    H: Handler<T>,
    T: 'static,
{
    Route::new(path, "PATCH", handler)
}

/// Create a DELETE route
pub fn delete_route<H, T>(path: &'static str, handler: H) -> Route
where
    H: Handler<T>,
    T: 'static,
{
    Route::new(path, "DELETE", handler)
}