#pragma once

#include <cstdint>
#include <optional>
#include <span>
#include <string>
#include <string_view>

#include "wireframe/l7/dissector.hpp"

// Best-effort, single-segment HTTP/1.x request/status-line parsing (plus
// the Host: header for requests). No TCP stream reassembly, so a
// message split across multiple packets is only partially visible here
// - the same scope DNS already has (single UDP datagram, no
// reassembly). Good enough for a one-line summary, not a full dissector.
namespace wireframe::net {

inline constexpr std::uint16_t kHttpPort = 80;

struct HttpMessage {
    bool is_request;
    std::string method_or_version;  // request: method (GET); response: "HTTP/1.1"
    std::string target_or_status;   // request: target path; response: status code
    std::optional<std::string> host;  // request only, from a Host: header if present
};

inline std::optional<HttpMessage> parse_http(std::span<const unsigned char> payload) {
    std::string_view text(reinterpret_cast<const char*>(payload.data()), payload.size());

    std::size_t line_end = text.find("\r\n");
    std::size_t term_len = 2;
    if (line_end == std::string_view::npos) {
        line_end = text.find('\n');
        term_len = 1;
        if (line_end == std::string_view::npos) return std::nullopt;
    }
    std::string_view first_line = text.substr(0, line_end);

    std::size_t sp1 = first_line.find(' ');
    if (sp1 == std::string_view::npos) return std::nullopt;
    std::size_t sp2 = first_line.find(' ', sp1 + 1);
    if (sp2 == std::string_view::npos) return std::nullopt;

    std::string_view field1 = first_line.substr(0, sp1);
    std::string_view field2 = first_line.substr(sp1 + 1, sp2 - sp1 - 1);

    HttpMessage msg;

    if (field1.substr(0, 5) == "HTTP/") {
        msg.is_request = false;
        msg.method_or_version = std::string(field1);
        msg.target_or_status = std::string(field2);
        return msg;
    }

    static constexpr std::string_view kMethods[] = {"GET",     "POST",  "PUT",     "DELETE",
                                                      "HEAD",    "OPTIONS", "PATCH", "CONNECT",
                                                      "TRACE"};
    bool known_method = false;
    for (auto method : kMethods) {
        if (field1 == method) {
            known_method = true;
            break;
        }
    }
    if (!known_method) return std::nullopt;

    msg.is_request = true;
    msg.method_or_version = std::string(field1);
    msg.target_or_status = std::string(field2);

    // Best-effort Host: header scan, bounded by whatever this one
    // packet contains and terminated at the first blank line (end of
    // headers) or the end of the payload - never loops past text.size().
    std::size_t pos = line_end + term_len;
    while (pos < text.size()) {
        std::size_t next_end = text.find("\r\n", pos);
        std::size_t header_len = (next_end == std::string_view::npos) ? text.size() - pos
                                                                        : next_end - pos;
        std::string_view header_line = text.substr(pos, header_len);
        if (header_line.empty()) break;  // blank line: end of headers

        if (header_line.size() > 5 &&
            (header_line.substr(0, 5) == "Host:" || header_line.substr(0, 5) == "host:")) {
            std::size_t value_start = 5;
            while (value_start < header_line.size() && header_line[value_start] == ' ') {
                ++value_start;
            }
            msg.host = std::string(header_line.substr(value_start));
        }

        if (next_end == std::string_view::npos) break;
        pos = next_end + 2;
    }

    return msg;
}

class HttpDissector : public L7Dissector {
public:
    std::uint16_t port() const override { return kHttpPort; }

    std::optional<std::string> summarize(std::span<const unsigned char> payload) const override {
        auto msg = parse_http(payload);
        if (!msg) return std::nullopt;

        std::string out = "HTTP " + msg->method_or_version + " " + msg->target_or_status;
        if (msg->host) out += " Host: " + *msg->host;
        return out;
    }
};

}  // namespace wireframe::net