//! Run with
//!
//! ```not_rust
//! cargo run -p example-validator
//!
//! curl '127.0.0.1:3000?name='
//! -> Input validation error: [name: Can not be empty]
//!
//! curl '127.0.0.1:3000?name=LT'
//! -> <h1>Hello, LT!</h1>
//! ```

use async_trait::async_trait;
use axum::{
    body::{Bytes, Full},
    extract::{Form, FromRequest, RequestParts},
    http::{Response, StatusCode},
    response::{Html, IntoResponse},
    routing::get,
    BoxError, Router,
};
use serde::{de::DeserializeOwned, Deserialize};
use std::{convert::Infallible, net::SocketAddr};
use thiserror::Error;
use validator::Validate;

#[tokio::main]
async fn main() {
    if std::env::var_os("RUST_LOG").is_none() {
        std::env::set_var("RUST_LOG", "example_validator=debug")
    }
    tracing_subscriber::fmt::init();

    // build our application with a route
    let app = Router::new().route("/", get(handler));

    // run it
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    tracing::debug!("listening on {}", addr);

    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

#[derive(Debug, Deserialize, Validate)]
pub struct NameInput {
    #[validate(length(min = 1, message = "Can not be empty"))]
    pub name: String,
}

async fn handler(ValidatedForm(input): ValidatedForm<NameInput>) -> Html<String> {
    Html(format!("<h1>Hello, {}!</h1>", input.name))
}

#[derive(Debug, Clone, Copy, Default)]
pub struct ValidatedForm<T>(pub T);

#[async_trait]
impl<T, B> FromRequest<B> for ValidatedForm<T>
where
    T: DeserializeOwned + Validate,
    B: http_body::Body + Send,
    B::Data: Send,
    B::Error: Into<BoxError>,
{
    type Rejection = ServerError;

    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
        let Form(value) = Form::<T>::from_request(req).await?;
        value.validate()?;
        Ok(ValidatedForm(value))
    }
}

#[derive(Debug, Error)]
pub enum ServerError {
    #[error(transparent)]
    ValidationError(#[from] validator::ValidationErrors),

    #[error(transparent)]
    AxumFormRejection(#[from] axum::extract::rejection::FormRejection),
}

impl IntoResponse for ServerError {
    type Body = Full<Bytes>;
    type BodyError = Infallible;

    fn into_response(self) -> Response<Self::Body> {
        match self {
            ServerError::ValidationError(_) => {
                let message = format!("Input validation error: [{}]", self).replace("\n", ", ");
                (StatusCode::BAD_REQUEST, message)
            }
            ServerError::AxumFormRejection(_) => (StatusCode::BAD_REQUEST, self.to_string()),
        }
        .into_response()
    }
}