#pragma once

#include <cstdio>
#include <optional>
#include <span>
#include <string>
#include <vector>

#include <pcap.h>

#include "wireframe/l7/dissector.hpp"
#include "wireframe/l7/dns.hpp"
#include "wireframe/l7/http.hpp"
#include "wireframe/l7/mdns.hpp"
#include "wireframe/l7/ssh.hpp"
#include "wireframe/l7/tls.hpp"
#include "wireframe/net/ethernet.hpp"
#include "wireframe/net/icmp.hpp"
#include "wireframe/net/ipv4.hpp"
#include "wireframe/net/ipv6.hpp"
#include "wireframe/net/tcp.hpp"
#include "wireframe/net/udp.hpp"

// Packet -> human-readable summary. Shared by every frontend (plain
// CLI, TUI, GUI) so they can't drift apart on what a given packet
// decodes to - one source of truth, not three copies to keep in sync.
namespace wireframe {

inline std::string mac_to_string(const net::MacAddress& mac) {
    char buf[18];
    std::snprintf(buf, sizeof(buf), "%02x:%02x:%02x:%02x:%02x:%02x", mac.bytes[0], mac.bytes[1],
                  mac.bytes[2], mac.bytes[3], mac.bytes[4], mac.bytes[5]);
    return buf;
}

inline std::string ipv4_to_string(const net::Ipv4Address& ip) {
    char buf[16];
    std::snprintf(buf, sizeof(buf), "%u.%u.%u.%u", ip.bytes[0], ip.bytes[1], ip.bytes[2],
                  ip.bytes[3]);
    return buf;
}

inline std::string tcp_flags_to_string(std::uint8_t flags) {
    using namespace net;
    std::string out;
    if (flags & kTcpSyn) out += 'S';
    if (flags & kTcpAck) out += 'A';
    if (flags & kTcpFin) out += 'F';
    if (flags & kTcpRst) out += 'R';
    if (flags & kTcpPsh) out += 'P';
    if (flags & kTcpUrg) out += 'U';
    return out.empty() ? "-" : out;
}

// Registered once. DNS (UDP) was the first L7 dissector, proving the
// interface (wireframe/l7/dissector.hpp) is enough to add a protocol
// without touching the L2-L4 decode path; HTTP (TCP) is the second,
// and the first to actually exercise L7Registry's TCP-payload path --
// DNS alone never did, since it only ever runs over UDP port 53. TLS
// (also TCP, port 443) covers what HTTP increasingly can't: most web
// traffic today is encrypted, and SNI is the one piece of a TLS
// handshake still readable without decrypting anything. mDNS reuses
// DNS's own parser (same wire format, different port/label) at
// essentially no extra cost. SSH is the first dissector whose *entire*
// protocol is one cleartext line before everything else encrypts --
// unlike TLS's SNI, there's nothing further to ever add here.
inline const net::L7Registry& l7_registry() {
    static const net::DnsDissector dns_dissector;
    static const net::HttpDissector http_dissector;
    static const net::TlsSniDissector tls_dissector;
    static const net::MdnsDissector mdns_dissector;
    static const net::SshDissector ssh_dissector;
    static const net::L7Registry registry = [] {
        net::L7Registry r;
        r.add(&dns_dissector);
        r.add(&http_dissector);
        r.add(&tls_dissector);
        r.add(&mdns_dissector);
        r.add(&ssh_dissector);
        return r;
    }();
    return registry;
}

// Tries the destination port first (the common case: a client talking
// to a well-known server port), then the source port (a server's
// reply, coming from that same well-known port).
inline std::optional<std::string> l7_summarize(std::span<const unsigned char> payload,
                                                 std::uint16_t src_port, std::uint16_t dst_port) {
    if (auto summary = l7_registry().dissect(dst_port, payload)) return summary;
    return l7_registry().dissect(src_port, payload);
}

// IPv4 and IPv6 headers carry different fields (ttl vs. hop_limit,
// 4-byte vs. 16-byte addresses), but everything above the IP layer --
// TCP/UDP decode plus the L7 lookup - is identical once normalized to
// this. Keeping that dispatch in one place means TCP/UDP/L7 formatting
// can't drift between the two IP versions.
struct IpInfo {
    const char* label;  // "IPv4" or "IPv6"
    std::string src_str;
    std::string dst_str;
    std::uint8_t ttl_or_hop_limit;
    std::uint8_t proto;
    std::span<const unsigned char> payload;
};

inline std::string summarize_transport_and_above(const IpInfo& info) {
    char ip_buf[160];
    std::snprintf(ip_buf, sizeof(ip_buf), " | %s %s -> %s ttl=%u proto=%u", info.label,
                  info.src_str.c_str(), info.dst_str.c_str(), info.ttl_or_hop_limit, info.proto);
    std::string out = ip_buf;

    if (info.proto == net::kProtoTcp) {
        if (auto tcp = net::parse_tcp(info.payload)) {
            char tcp_buf[128];
            std::snprintf(tcp_buf, sizeof(tcp_buf), " | TCP %u -> %u [%s] seq=%u ack=%u win=%u",
                          tcp->header.src_port, tcp->header.dst_port,
                          tcp_flags_to_string(tcp->header.flags).c_str(), tcp->header.seq,
                          tcp->header.ack, tcp->header.window);
            out += tcp_buf;
            if (auto l7 = l7_summarize(tcp->payload, tcp->header.src_port, tcp->header.dst_port)) {
                out += " | " + *l7;
            }
        }
    } else if (info.proto == net::kProtoUdp) {
        if (auto udp = net::parse_udp(info.payload)) {
            char udp_buf[64];
            std::snprintf(udp_buf, sizeof(udp_buf), " | UDP %u -> %u len=%u",
                          udp->header.src_port, udp->header.dst_port, udp->header.length);
            out += udp_buf;
            if (auto l7 = l7_summarize(udp->payload, udp->header.src_port, udp->header.dst_port)) {
                out += " | " + *l7;
            }
        }
    } else if (info.proto == net::kProtoIcmp) {
        if (auto icmp = net::parse_icmpv4(info.payload)) {
            out += " | ICMP " + net::icmpv4_type_name(icmp->type);
            if (icmp->identifier) {
                out += " id=" + std::to_string(*icmp->identifier) +
                       " seq=" + std::to_string(*icmp->sequence);
            }
        }
    } else if (info.proto == net::kNextHeaderIcmpv6) {
        if (auto icmp = net::parse_icmpv6(info.payload)) {
            out += " | ICMPv6 " + net::icmpv6_type_name(icmp->type);
            if (icmp->identifier) {
                out += " id=" + std::to_string(*icmp->identifier) +
                       " seq=" + std::to_string(*icmp->sequence);
            }
        } else {
            out += " | ICMPv6";  // truncated: at least say what it is
        }
    }
    return out;
}

// `datalink` is the interface's actual pcap_datalink() type, not an
// assumption: tunnel/VPN interfaces (tailscale0, wireguard, plain
// tun/tap) hand libpcap raw IP with no link-layer header at all
// (DLT_RAW), unlike a real NIC or even `lo` (both DLT_EN10MB on
// Linux). Treating raw IP bytes as an Ethernet frame silently produces
// garbage MACs and ethertypes - verified by actually capturing on
// tailscale0 before this branch existed.
//
// IP version is read from the packet itself (the first nibble), not
// inferred from ethertype/datalink: DLT_RAW has no ethertype to key
// off at all, and even on Ethernet this keeps IPv4/IPv6 dispatch in
// one place.
inline std::string summarize_packet(std::span<const unsigned char> bytes, int datalink) {
    std::span<const unsigned char> ip_bytes;
    std::string out;

    if (datalink == DLT_RAW) {
        out = "RAW";
        ip_bytes = bytes;
    } else {
        auto eth = net::parse_ethernet(bytes);
        if (!eth) {
            char buf[64];
            std::snprintf(buf, sizeof(buf), "[%zu bytes] truncated ethernet frame", bytes.size());
            return buf;
        }

        out = "ETH " + mac_to_string(eth->header.src) + " -> " + mac_to_string(eth->header.dst);
        char eth_buf[32];
        std::snprintf(eth_buf, sizeof(eth_buf), " ethertype=0x%04x", eth->header.ethertype);
        out += eth_buf;

        if (eth->header.ethertype != net::kEthertypeIPv4 &&
            eth->header.ethertype != net::kEthertypeIPv6) {
            return out;
        }
        ip_bytes = eth->payload;
    }

    if (ip_bytes.empty()) {
        out += " | IP (empty payload)";
        return out;
    }
    std::uint8_t version = static_cast<std::uint8_t>(ip_bytes[0] >> 4);

    if (version == 4) {
        auto ip = net::parse_ipv4(ip_bytes);
        if (!ip) {
            out += " | IPv4 (truncated)";
            return out;
        }
        out += summarize_transport_and_above({"IPv4", ipv4_to_string(ip->header.src),
                                               ipv4_to_string(ip->header.dst), ip->header.ttl,
                                               ip->header.protocol, ip->payload});
    } else if (version == 6) {
        auto ip6 = net::parse_ipv6(ip_bytes);
        if (!ip6) {
            out += " | IPv6 (truncated)";
            return out;
        }
        std::string src_str = net::ipv6_to_string(ip6->header.src);
        std::string dst_str = net::ipv6_to_string(ip6->header.dst);

        // next_header may name an extension header (Hop-by-Hop,
        // Routing, Dest Options, Fragment, AH) rather than the actual
        // transport protocol; walk through those to find it.
        auto walked = net::walk_ipv6_extension_headers(ip6->header.next_header, ip6->payload);
        if (walked.stopped_at_esp) {
            char buf[160];
            std::snprintf(buf, sizeof(buf), " | IPv6 %s -> %s ttl=%u proto=%u | ESP (encrypted)",
                          src_str.c_str(), dst_str.c_str(), ip6->header.hop_limit,
                          net::kNextHeaderEsp);
            out += buf;
        } else {
            out += summarize_transport_and_above({"IPv6", src_str, dst_str, ip6->header.hop_limit,
                                                   walked.final_next_header, walked.payload});
        }
    } else {
        out += " | IP version " + std::to_string(version) + " (unsupported)";
    }
    return out;
}

// One formatted line per 16 bytes: offset, hex, ASCII gutter. Returned
// as lines rather than printed so both the CLI's -x output and a GUI
// details pane can use the same formatting.
inline std::vector<std::string> hex_dump_lines(std::span<const unsigned char> bytes) {
    std::vector<std::string> lines;
    for (std::size_t offset = 0; offset < bytes.size(); offset += 16) {
        char offset_buf[32];
        std::snprintf(offset_buf, sizeof(offset_buf), "%06zx  ", offset);
        std::string line = offset_buf;

        std::size_t line_len = std::min<std::size_t>(16, bytes.size() - offset);
        for (std::size_t i = 0; i < 16; ++i) {
            if (i < line_len) {
                char byte_buf[4];
                std::snprintf(byte_buf, sizeof(byte_buf), "%02x ", bytes[offset + i]);
                line += byte_buf;
            } else {
                line += "   ";
            }
            if (i == 7) line += ' ';
        }

        line += " |";
        for (std::size_t i = 0; i < line_len; ++i) {
            unsigned char c = bytes[offset + i];
            line += (c >= 0x20 && c < 0x7f) ? static_cast<char>(c) : '.';
        }
        line += '|';

        lines.push_back(std::move(line));
    }
    return lines;
}

}  // namespace wireframe