// Copyright (c) 2026 Cyprien Avico avicocyprien@yahoo.com
//
// Licensed under the MIT License <LICENSE-MIT or http://opensource.org/licenses/MIT>.
// This file may not be copied, modified, or distributed except according to those terms.

//! Module for parsing HTTP packets.

use std::convert::TryFrom;
use std::fmt;

use crate::{
    checks::application::http::{
        parse_payload_as_utf8, require_header_part, require_method, require_request_line,
        require_uri, require_version,
    },
    errors::application::http::HttpParseError,
};

#[cfg_attr(doc, aquamarine::aquamarine)]
/// HTTP Request
///
/// ```mermaid
/// ---
/// title: HttpRequest
/// ---
/// packet-beta
/// 0-63: "Request Line variable"
/// 64-127: "Headers variable"
/// 128-143: "CRLF separator"
/// 144-207: "Body variable"
/// ```
///
/// The `HttpRequest` struct represents a parsed HTTP request.
#[derive(Debug)]
pub struct HttpRequest {
    pub method: String,
    pub uri: String,
    pub version: String,
    pub headers: Vec<(String, String)>,
    pub body: String,
}

impl fmt::Display for HttpRequest {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "HTTP Request: method={}, uri={}, version={}, headers={:?}, body={}",
            self.method, self.uri, self.version, self.headers, self.body
        )
    }
}

impl TryFrom<&[u8]> for HttpRequest {
    type Error = HttpParseError;

    fn try_from(payload: &[u8]) -> Result<Self, Self::Error> {
        parse_http_request(payload)
    }
}

/// Parses an HTTP request from a given payload.
pub fn parse_http_request(payload: &[u8]) -> Result<HttpRequest, HttpParseError> {
    let payload_str = parse_payload_as_utf8(payload)?;

    let mut lines = payload_str.split("\r\n");

    let request_line = require_request_line(lines.next())?;

    let mut request_parts = request_line.split_whitespace();
    let method = require_method(request_parts.next())?.to_string();
    let uri = require_uri(request_parts.next())?.to_string();
    let version = require_version(request_parts.next())?.to_string();

    let mut headers = Vec::new();
    for line in lines.by_ref() {
        if line.is_empty() {
            break;
        }
        let mut header_parts = line.splitn(2, ':');
        let name = require_header_part(header_parts.next())?.trim().to_string();
        let value = require_header_part(header_parts.next())?.trim().to_string();
        headers.push((name, value));
    }

    let body = lines.collect::<Vec<&str>>().join("\r\n");

    Ok(HttpRequest {
        method,
        uri,
        version,
        headers,
        body,
    })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_http_request() {
        let http_payload = b"GET /index.html HTTP/1.1\r\nHost: www.example.com\r\nUser-Agent: curl/7.68.0\r\nAccept: */*\r\n\r\n";
        match HttpRequest::try_from(&http_payload[..]) {
            Ok(request) => {
                assert_eq!(request.method, "GET");
                assert_eq!(request.uri, "/index.html");
                assert_eq!(request.version, "HTTP/1.1");
                assert_eq!(request.headers.len(), 3);
                assert_eq!(
                    request.headers[0],
                    ("Host".to_string(), "www.example.com".to_string())
                );
                assert_eq!(
                    request.headers[1],
                    ("User-Agent".to_string(), "curl/7.68.0".to_string())
                );
                assert_eq!(
                    request.headers[2],
                    ("Accept".to_string(), "*/*".to_string())
                );
                assert_eq!(request.body, "");
            }
            Err(_) => panic!("Expected HTTP request"),
        }
    }

    #[test]
    fn test_parse_http_request_with_body() {
        let http_payload = b"POST /submit HTTP/1.1\r\nHost: www.example.com\r\nContent-Type: application/x-www-form-urlencoded\r\nContent-Length: 13\r\n\r\nfield1=value1";
        match HttpRequest::try_from(&http_payload[..]) {
            Ok(request) => {
                assert_eq!(request.method, "POST");
                assert_eq!(request.uri, "/submit");
                assert_eq!(request.version, "HTTP/1.1");
                assert_eq!(request.headers.len(), 3);
                assert_eq!(
                    request.headers[0],
                    ("Host".to_string(), "www.example.com".to_string())
                );
                assert_eq!(
                    request.headers[1],
                    (
                        "Content-Type".to_string(),
                        "application/x-www-form-urlencoded".to_string()
                    )
                );
                assert_eq!(
                    request.headers[2],
                    ("Content-Length".to_string(), "13".to_string())
                );
                assert_eq!(request.body, "field1=value1");
            }
            Err(_) => panic!("Expected HTTP request with body"),
        }
    }

    #[test]
    fn test_parse_http_request_invalid() {
        let http_payload = b"INVALID REQUEST\r\n\r\n";
        match HttpRequest::try_from(&http_payload[..]) {
            Ok(_) => panic!("Expected invalid HTTP request"),
            Err(err) => assert_eq!(err, HttpParseError::MissingVersion),
        }
    }
}
