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use std::collections::HashMap;
use std::io::{BufRead, BufReader, Write};
use std::net::{Shutdown, TcpListener, TcpStream};
use std::str::FromStr;
use std::thread;

pub enum HttpMethod {
    GET,
    POST,
    PUT,
    PATCH,
    DELETE,
    OPTIONS,
}

impl FromStr for HttpMethod {
    type Err = ();

    fn from_str(input: &str) -> Result<HttpMethod, ()> {
        match input {
            "GET" => Ok(HttpMethod::GET),
            "POST" => Ok(HttpMethod::POST),
            "PUT" => Ok(HttpMethod::PUT),
            "PATCH" => Ok(HttpMethod::PATCH),
            "DELETE" => Ok(HttpMethod::DELETE),
            "OPTIONS" => Ok(HttpMethod::OPTIONS),
            _ => Err(())
        }
    }
}

pub struct HttpRequest {
    pub method: HttpMethod,
    pub path: String,
}

pub struct HttpResponse {
    pub status_code: i32,
    pub status_code_message: String,
    pub headers: HashMap<String, String>,
    pub body: String,
}

pub fn start(addr: &str, callback: fn(HttpRequest) -> HttpResponse) -> Result<(), &str> {
    let listener = TcpListener::bind(addr);

    if listener.is_err() {
        return Err("Could not bind listener to address");
    }

    let listener = listener.unwrap();

    for stream in listener.incoming() {
        let stream = stream;

        if stream.is_err() {
            return Err("Error when trying to get the stream instance.");
        }

        let stream = stream.unwrap();

        process_request(stream, callback);
    }

    return Ok(());
}

pub fn start_multithreaded(addr: &str, callback: fn(HttpRequest) -> HttpResponse) -> Result<(), &str> {
    let listener = TcpListener::bind(addr);

    if listener.is_err() {
        return Err("Could not bind listener to address");
    }

    let listener = listener.unwrap();

    for stream in listener.incoming() {
        let stream = stream;

        if stream.is_err() {
            return Err("Error when trying to get the stream instance.");
        }

        let stream = stream.unwrap();

        thread::spawn(move || process_request(stream, callback));
    }

    return Ok(());
}

fn process_request(mut stream: TcpStream, callback: fn(HttpRequest) -> HttpResponse) {
    let mut buffer = String::new();

    let mut reader = BufReader::new(&mut stream);

    reader.read_line(&mut buffer).expect("Can't read line");

    let http_request = analyze_request_data(buffer.clone());
    let http_response: HttpResponse;

    if http_request.is_err() {
        println!("{}", buffer);

        http_response = HttpResponse
        {
            status_code: 400,
            status_code_message: "Bad Request".to_string(),
            headers: Default::default(),
            body: "".to_string(),
        };
    } else {
        let http_request = http_request.unwrap();

        http_response = callback(http_request);
    }

    let generated_response = generate_response(http_response);

    let _ = stream.write(generated_response.as_bytes());
    let _ = stream.shutdown(Shutdown::Both);
    drop(stream);
}

fn analyze_request_data(request_payload: String) -> Result<HttpRequest, &'static str> {
    let splitted_request_payload: Vec<String> = request_payload
        .split("\r\n")
        .map(|x| x.strip_suffix("\r\n").unwrap_or(&*x))
        .map(|x| x.to_string())
        .collect::<Vec<String>>();

    if splitted_request_payload.len() == 0 {
        return Err("Request is empty.");
    }

    let splitted_protocol_line: Vec<String> = splitted_request_payload[0]
        .split(" ")
        .map(|x| x.to_string())
        .collect::<Vec<String>>();

    if splitted_protocol_line.len() < 3 {
        return Err("Protocol line is invalid! It should contain minimum 3 elements");
    }

    let method = HttpMethod::from_str(splitted_protocol_line[0].as_ref());

    if method.is_err() {
        return Err("Protocol line contains invalid method.");
    }

    let method = method.unwrap();

    if splitted_protocol_line[2] != "HTTP/1.1" {
        return Err("Protocol line contains invalid protocol version");
    }

    let http_request = HttpRequest {
        method,
        path: splitted_protocol_line[1].to_string(),
    };

    return Ok(http_request);
}

fn generate_response(mut http_response: HttpResponse) -> String {
    let mut raw: String = format!("HTTP/1.1 {0} {1}\r\n", http_response.status_code.to_string(), http_response.status_code_message);
    if http_response.body != "" {
        http_response.headers.insert("Content-Length".parse().unwrap(), http_response.body.as_bytes().len().to_string());
    }

    for header in http_response.headers {
        raw.push_str(&*header.0);
        raw.push_str(": ");
        raw.push_str(&*header.1);
        raw.push_str("\r\n");
    }
    raw.push_str("\r\n");
    raw.push_str(&*http_response.body);
    raw.push_str("\r\n");

    return raw;
}