From f6a09236f8efc70208796fedb915ea584ed5ea49 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Ma=C4=87kowski?= <m4tx@m4tx.pl>
Date: Mon, 8 Jul 2024 16:13:27 -0700
Subject: [PATCH] feat: initial API implementation

This is an early vision of the basic concepts and how the API overall
might look like in the future. There's also a fully working Hello world
example that implements a single endpoint.
---
 Cargo.toml                       |   5 +
 examples/hello-world/Cargo.toml  |   3 +
 examples/hello-world/src/main.rs |  30 ++-
 flareon/Cargo.toml               |   8 +
 flareon/src/lib.rs               | 309 ++++++++++++++++++++++++++++++-
 flareon/src/prelude.rs           |   3 +
 6 files changed, 348 insertions(+), 10 deletions(-)
 create mode 100644 flareon/src/prelude.rs

diff --git a/Cargo.toml b/Cargo.toml
index e3ee4d6..c6fe397 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,12 +17,17 @@ license = "MIT OR Apache-2.0"
 [workspace.dependencies]
 async-trait = "0.1.80"
 axum = "0.7.5"
+bytes = "1.6.1"
 chrono = { version = "0.4.38", features = ["serde"] }
 clap = { version = "4.5.8", features = ["derive", "env"] }
+derive_builder = "0.20.0"
 env_logger = "0.11.3"
+indexmap = "2.2.6"
 itertools = "0.13.0"
 log = "0.4.22"
+regex = "1.10.5"
 serde = "1.0.203"
 slug = "0.1.5"
 tokio = { version = "1.38.0", features = ["macros", "rt-multi-thread"] }
 tower = "0.4.13"
+thiserror = "1.0.61"
diff --git a/examples/hello-world/Cargo.toml b/examples/hello-world/Cargo.toml
index 2dbef25..05cdc2e 100644
--- a/examples/hello-world/Cargo.toml
+++ b/examples/hello-world/Cargo.toml
@@ -3,5 +3,8 @@ name = "example-hello-world"
 version = "0.1.0"
 publish = false
 description = "Hello World - Flareon example."
+edition = "2021"
 
 [dependencies]
+flareon = { path = "../../flareon" }
+tokio = { version = "1.38.0", features = ["macros", "rt-multi-thread"] }
diff --git a/examples/hello-world/src/main.rs b/examples/hello-world/src/main.rs
index f328e4d..c0d5667 100644
--- a/examples/hello-world/src/main.rs
+++ b/examples/hello-world/src/main.rs
@@ -1 +1,29 @@
-fn main() {}
+use std::sync::Arc;
+
+use flareon::prelude::{
+    Body, Error, FlareonApp, FlareonProject, Request, Response, Route, StatusCode,
+};
+
+fn return_hello(_request: Request) -> Result<Response, Error> {
+    Ok(Response::new_html(
+        StatusCode::OK,
+        Body::fixed("<h1>Hello Flareon!</h1>".as_bytes().to_vec()),
+    ))
+}
+
+#[tokio::main]
+async fn main() {
+    let hello_app = FlareonApp::builder()
+        .urls([Route::with_handler("", Arc::new(Box::new(return_hello)))])
+        .build()
+        .unwrap();
+
+    let flareon_project = FlareonProject::builder()
+        .register_app_with_views(hello_app, "")
+        .build()
+        .unwrap();
+
+    flareon::run(flareon_project, "127.0.0.1:8000")
+        .await
+        .unwrap();
+}
diff --git a/flareon/Cargo.toml b/flareon/Cargo.toml
index 73215d2..25d8064 100644
--- a/flareon/Cargo.toml
+++ b/flareon/Cargo.toml
@@ -6,3 +6,11 @@ license.workspace = true
 description = "Modern web framework focused on speed and ease of use."
 
 [dependencies]
+async-trait.workspace = true
+axum.workspace = true
+bytes.workspace = true
+derive_builder.workspace = true
+indexmap.workspace = true
+log.workspace = true
+thiserror.workspace = true
+tokio.workspace = true
diff --git a/flareon/src/lib.rs b/flareon/src/lib.rs
index b93cf3f..1b562fb 100644
--- a/flareon/src/lib.rs
+++ b/flareon/src/lib.rs
@@ -1,14 +1,305 @@
-pub fn add(left: u64, right: u64) -> u64 {
-    left + right
+pub mod prelude;
+
+use std::fmt::{Debug, Formatter};
+use std::io::Read;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use axum::handler::HandlerWithoutStateExt;
+use bytes::Bytes;
+use derive_builder::Builder;
+use indexmap::IndexMap;
+use log::info;
+use thiserror::Error;
+
+pub type StatusCode = axum::http::StatusCode;
+
+#[async_trait]
+pub trait RequestHandler {
+    async fn handle(&self, request: Request) -> Result<Response, Error>;
+}
+
+#[derive(Clone, Debug)]
+pub struct Router {
+    urls: Vec<Route>,
+}
+
+impl Router {
+    #[must_use]
+    pub fn with_urls<T: Into<Vec<Route>>>(urls: T) -> Self {
+        Self { urls: urls.into() }
+    }
+
+    async fn route(&self, request: Request, request_path: &str) -> Result<Response, Error> {
+        for route in &self.urls {
+            if request_path.starts_with(&route.url) {
+                let request_path = &request_path[route.url.len()..];
+                match &route.view {
+                    RouteInner::Handler(handler) => return handler.handle(request).await,
+                    RouteInner::Router(router) => {
+                        return Box::pin(router.route(request, request_path)).await
+                    }
+                }
+            }
+        }
+
+        unimplemented!("404 handler is not implemented yet")
+    }
+}
+
+#[async_trait]
+impl RequestHandler for Router {
+    async fn handle(&self, request: Request) -> Result<Response, Error> {
+        let path = request.uri().path().to_owned();
+        self.route(request, &path).await
+    }
+}
+
+#[async_trait]
+impl<T> RequestHandler for T
+where
+    T: Fn(Request) -> Result<Response, Error> + Send + Sync,
+{
+    async fn handle(&self, request: Request) -> Result<Response, Error> {
+        self(request)
+    }
+}
+
+/// A building block for a Flareon project.
+///
+/// A Flareon app is a part (ideally, reusable) of a Flareon project that is
+/// responsible for its own set of functionalities. Examples of apps could be:
+/// * admin panel
+/// * user authentication
+/// * blog
+/// * message board
+/// * session management
+/// * etc.
+///
+/// Each app can have its own set of URLs that it can handle which can be
+/// mounted on the project's router, its own set of middleware, database
+/// migrations (which can depend on other apps), etc.
+#[derive(Clone, Debug, Builder)]
+#[builder(setter(into))]
+pub struct FlareonApp {
+    router: Router,
+}
+
+impl FlareonApp {
+    #[must_use]
+    pub fn builder() -> FlareonAppBuilder {
+        FlareonAppBuilder::default()
+    }
+}
+
+impl FlareonAppBuilder {
+    #[allow(unused_mut)]
+    pub fn urls<T: Into<Vec<Route>>>(&mut self, urls: T) -> &mut Self {
+        let mut new = self;
+        new.router = Some(Router::with_urls(urls.into()));
+        new
+    }
+}
+
+#[derive(Clone)]
+pub struct Route {
+    url: String,
+    view: RouteInner,
+}
+
+impl Route {
+    #[must_use]
+    pub fn with_handler<T: Into<String>>(
+        url: T,
+        view: Arc<Box<dyn RequestHandler + Send + Sync>>,
+    ) -> Self {
+        Self {
+            url: url.into(),
+            view: RouteInner::Handler(view),
+        }
+    }
+
+    #[must_use]
+    pub fn with_router<T: Into<String>>(url: T, router: Router) -> Self {
+        Self {
+            url: url.into(),
+            view: RouteInner::Router(router),
+        }
+    }
 }
 
-#[cfg(test)]
-mod tests {
-    use super::*;
+#[derive(Clone)]
+enum RouteInner {
+    Handler(Arc<Box<dyn RequestHandler + Send + Sync>>),
+    Router(Router),
+}
+
+impl Debug for Route {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match &self.view {
+            RouteInner::Handler(_) => f.debug_tuple("Handler").field(&"handler(...)").finish(),
+            RouteInner::Router(router) => f.debug_tuple("Router").field(router).finish(),
+        }
+    }
+}
+
+pub type Request = axum::extract::Request;
+
+type HeadersMap = IndexMap<String, String>;
+
+#[derive(Debug)]
+pub struct Response {
+    status: StatusCode,
+    headers: HeadersMap,
+    body: Body,
+}
+
+const CONTENT_TYPE_HEADER: &str = "Content-Type";
+const HTML_CONTENT_TYPE: &str = "text/html";
+
+impl Response {
+    #[must_use]
+    pub fn new_html(status: StatusCode, body: Body) -> Self {
+        Self {
+            status,
+            headers: Self::html_headers(),
+            body,
+        }
+    }
 
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
+    #[must_use]
+    fn html_headers() -> HeadersMap {
+        let mut headers = HeadersMap::new();
+        headers.insert(CONTENT_TYPE_HEADER.to_owned(), HTML_CONTENT_TYPE.to_owned());
+        headers
     }
 }
+
+pub enum Body {
+    Fixed(Bytes),
+    Streaming(Box<dyn Read>),
+}
+
+impl Debug for Body {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Body::Fixed(data) => f.debug_tuple("Fixed").field(data).finish(),
+            Body::Streaming(_) => f.debug_tuple("Streaming").field(&"...").finish(),
+        }
+    }
+}
+
+impl Body {
+    #[must_use]
+    pub fn empty() -> Self {
+        Self::Fixed(Bytes::new())
+    }
+
+    #[must_use]
+    pub fn fixed<T: Into<Bytes>>(data: T) -> Self {
+        Self::Fixed(data.into())
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("Could not create a response object: {0}")]
+    ResponseBuilder(#[from] axum::http::Error),
+}
+
+#[derive(Clone, Debug)]
+pub struct FlareonProject {
+    apps: Vec<FlareonApp>,
+    router: Router,
+}
+
+#[derive(Debug)]
+pub struct FlareonProjectBuilder {
+    apps: Vec<FlareonApp>,
+    urls: Vec<Route>,
+}
+
+impl FlareonProjectBuilder {
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            apps: Vec::new(),
+            urls: Vec::new(),
+        }
+    }
+
+    #[must_use]
+    pub fn register_app_with_views(&mut self, app: FlareonApp, url_prefix: &str) -> &mut Self {
+        let new = self;
+        new.urls.push(Route::with_handler(
+            url_prefix,
+            Arc::new(Box::new(app.router.clone())),
+        ));
+        new.apps.push(app);
+        new
+    }
+
+    pub fn build(&self) -> Result<FlareonProject, Error> {
+        Ok(FlareonProject {
+            apps: self.apps.clone(),
+            router: Router::with_urls(self.urls.clone()),
+        })
+    }
+}
+
+impl Default for FlareonProjectBuilder {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl FlareonProject {
+    #[must_use]
+    pub fn builder() -> FlareonProjectBuilder {
+        FlareonProjectBuilder::default()
+    }
+}
+
+pub async fn run(mut project: FlareonProject, address_str: &str) -> Result<(), Error> {
+    for app in &mut project.apps {
+        info!("Initializing app: {:?}", app);
+    }
+
+    let listener = tokio::net::TcpListener::bind(address_str).await.unwrap();
+
+    let handler = |request: axum::extract::Request| async move {
+        pass_to_axum(&project, request)
+            .await
+            .unwrap_or_else(handle_response_error)
+    };
+    axum::serve(listener, handler.into_make_service())
+        .await
+        .unwrap();
+
+    Ok(())
+}
+
+async fn pass_to_axum(
+    project: &FlareonProject,
+    request: axum::extract::Request,
+) -> Result<axum::response::Response, Error> {
+    let response = project.router.handle(request).await?;
+
+    let mut builder = axum::http::Response::builder().status(response.status);
+    for (key, value) in response.headers {
+        builder = builder.header(key, value);
+    }
+    let axum_response = builder.body(match response.body {
+        Body::Fixed(data) => axum::body::Body::from(data),
+        Body::Streaming(_) => unimplemented!(),
+    });
+
+    match axum_response {
+        Ok(response) => Ok(response),
+        Err(error) => Err(Error::ResponseBuilder(error)),
+    }
+}
+
+fn handle_response_error(_error: Error) -> axum::response::Response {
+    unimplemented!("500 error handler is not implemented yet")
+}
diff --git a/flareon/src/prelude.rs b/flareon/src/prelude.rs
new file mode 100644
index 0000000..6c2ec5f
--- /dev/null
+++ b/flareon/src/prelude.rs
@@ -0,0 +1,3 @@
+pub use crate::{
+    Body, Error, FlareonApp, FlareonProject, Request, RequestHandler, Response, Route, StatusCode,
+};