use std::io;
use std::net::TcpListener;
use std::net::TcpStream;
use std::thread;

use rusty_http::Http;
use rusty_http::Request;
use rusty_http::Response;
use rusty_http::StatusCode;

const DIALOG_A_NOT_FOUND: &str = "
    <h1>400 Bad Request</h1>
    <p>Parameter 'a' not found</p>
";

const DIALOG_B_NOT_FOUND: &str = "
    <h1>400 Bad Request</h1>
    <p>Parameter 'b' not found</p>
";

const DIALOG_A_INVALID: &str = "
    <h1>400 Bad Request</h1>
    <p>Parameter 'a' can only be a number from 0 to 255</p>
";

const DIALOG_B_INVALID: &str = "
    <h1>400 Bad Request</h1>
    <p>Parameter 'b' can only be a number from 0 to 255</p>
";

fn add(request: Request, response: Response) -> io::Result<()> {
    let Some(a) = request.params.get("a") else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_A_NOT_FOUND)?;
        
        return Ok(());
    };

    let Some(b) = request.params.get("b") else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_B_NOT_FOUND)?;
        
        return Ok(());
    };

    let Ok(a) = a.parse::<u8>() else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_A_INVALID)?;
        
        return Ok(());
    };

    let Ok(b) = b.parse::<u8>() else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_B_INVALID)?;
        return Ok(());
    };

    let content = format!("<h1>{} + {} = {}</h1>", a, b, a as u16 + b as u16);

    response.html(content)?;

    Ok(())
}

fn sub(request: Request, response: Response) -> io::Result<()> {
    let Some(a) = request.params.get("a") else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_A_NOT_FOUND)?;
        
        return Ok(());
    };

    let Some(b) = request.params.get("b") else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_B_NOT_FOUND)?;
        
        return Ok(());
    };

    let Ok(a) = a.parse::<u8>() else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_A_INVALID)?;
        
        return Ok(());
    };

    let Ok(b) = b.parse::<u8>() else {
        response.status_code(StatusCode::BadRequest)
                .html(&DIALOG_B_INVALID)?;
        return Ok(());
    };

    let content = format!("<h1>{} - {} = {}</h1>", a, b, a as i16 - b as i16);
    
    response.html(content)?;

    Ok(())
}

fn not_found(request: Request, response: Response) -> io::Result<()> {
    let content = format!("
        <h1>400 Bad Request</h1>
        <p>Page '{}' could not been found</p>
    ", request.uri);

    response.status_code(StatusCode::NotFound)
            .html(content)?;

    Ok(())
}

fn init_stream(stream: TcpStream) -> io::Result<()> {
    let (request, response) = Http::from(stream)?;

    match request.uri.as_str() {
        "/add" => add(request, response)?,
        "/sub" => sub(request, response)?,
        _      => not_found(request, response)?
    }

    Ok(())
}

fn main() -> io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:8080")?;

    for stream in listener.incoming().filter_map(Result::ok) {
        thread::spawn(|| init_stream(stream));
    }

    Ok(())
}