// disc_identity.cpp — see disc_identity.h.
//
// The header detection mirrors the proven raw-sector logic previously inlined
// in main.cpp (handles both 2352-byte raw and 2048-byte cooked sector layouts,
// which is what real .bin/.cue and .iso dumps use respectively).

#include "disc_identity.h"

#include "crc32.h"
#include "disc_path.h"

#include <algorithm>
#include <cctype>
#include <cstring>
#include <fstream>
#include <sstream>
#include <vector>

namespace fs = std::filesystem;

namespace PSXRecompV4 {

namespace {

std::string uppercase_ascii(std::string s) {
    for (char& c : s) c = (char)std::toupper((unsigned char)c);
    return s;
}

bool read_at(std::ifstream& f, uint64_t offset, uint8_t* out, size_t len) {
    f.clear();
    f.seekg((std::streamoff)offset, std::ios::beg);
    if (!f.good()) return false;
    f.read(reinterpret_cast<char*>(out), (std::streamsize)len);
    return f.gcount() == (std::streamsize)len;
}

bool is_iso_pvd(const uint8_t* sector) {
    return sector[0] == 0x01 && std::memcmp(&sector[1], "CD001", 5) == 0 && sector[6] == 0x01;
}

// "SCUS-94236" -> region. PSX serial prefixes encode the territory.
std::string region_from_serial(const std::string& serial) {
    if (serial.size() < 4) return std::string();
    const std::string p = uppercase_ascii(serial.substr(0, 4));
    if (p == "SCUS" || p == "SLUS" || p == "LSP9") return "NTSC-U";
    if (p == "SCES" || p == "SLES" || p == "SCED" || p == "SLED") return "PAL";
    if (p == "SCPS" || p == "SLPS" || p == "SLPM" || p == "SCPM" || p == "ESPM") return "NTSC-J";
    return std::string();
}

// Normalize a scanned EXE-style id "SCUS_942.36" to the game-id form
// "SCUS-94236". Pass-through for things already in game-id form. Returns ""
// if the token doesn't look like a serial.
std::string normalize_serial(const std::string& raw) {
    std::string s;
    for (char c : raw) {
        if (std::isalnum((unsigned char)c)) s += (char)std::toupper((unsigned char)c);
        // drop separators ('_', '.', '-')
    }
    // Expect 4 letters + 5 digits.
    if (s.size() < 9) return std::string();
    for (int i = 0; i < 4; i++) if (!std::isalpha((unsigned char)s[i])) return std::string();
    for (int i = 4; i < 9; i++) if (!std::isdigit((unsigned char)s[i])) return std::string();
    return s.substr(0, 4) + "-" + s.substr(4, 5);
}

// Scan the SYSTEM.CNF text region for the BOOT serial. PSX SYSTEM.CNF holds a
// line like `BOOT = cdrom:\SCUS_942.36;1`. We look for "cdrom:" and read the
// following filename token, then normalize it.
std::string scan_boot_serial(const std::vector<uint8_t>& buf) {
    static const char kKey[] = "cdrom:";
    const size_t klen = sizeof(kKey) - 1;
    if (buf.size() < klen) return std::string();
    for (size_t i = 0; i + klen < buf.size(); i++) {
        bool hit = true;
        for (size_t k = 0; k < klen; k++) {
            char a = (char)std::tolower((unsigned char)buf[i + k]);
            if (a != kKey[k]) { hit = false; break; }
        }
        if (!hit) continue;
        // Read the token after "cdrom:", skipping any leading path separators.
        size_t j = i + klen;
        while (j < buf.size() && (buf[j] == '\\' || buf[j] == '/')) j++;
        std::string token;
        while (j < buf.size()) {
            char c = (char)buf[j];
            if (c == ';' || c == '\r' || c == '\n' || c == ' ' || c == '\t' || c == 0) break;
            token += c;
            j++;
            if (token.size() > 32) break;
        }
        const size_t slash = token.find_last_of("\\/");
        if (slash != std::string::npos) token = token.substr(slash + 1);
        const std::string norm = normalize_serial(token);
        if (!norm.empty()) return norm;
    }
    return std::string();
}

uint32_t crc32_stream(std::ifstream& f) {
    f.clear();
    f.seekg(0, std::ios::beg);
    uint32_t crc = 0xFFFFFFFFu;
    std::vector<uint8_t> chunk(1u << 20);  // 1 MiB
    while (f.good()) {
        f.read(reinterpret_cast<char*>(chunk.data()), (std::streamsize)chunk.size());
        const std::streamsize got = f.gcount();
        if (got <= 0) break;
        crc = crc32_update(crc, chunk.data(), (size_t)got);
    }
    return crc ^ 0xFFFFFFFFu;
}

}  // namespace

DiscIdentity identify_disc(const fs::path& path,
                           const std::string& expected_serial,
                           uint32_t expected_crc, bool has_expected_crc,
                           bool compute_crc) {
    DiscIdentity v;
    v.expected_serial_given = !expected_serial.empty();
    v.expected_crc_given    = has_expected_crc;

    // Resolve through the shared picked-path resolver so identity is read from
    // the data track no matter which member of the dump the user handed us —
    // the .cue and its .bin must produce the same verdict, serial and CRC32.
    const DiscPathResolution resolved = resolve_disc_path(path);
    const fs::path data_path = resolved.data;
    std::ifstream f(data_path, std::ios::binary | std::ios::ate);
    if (!f.is_open()) {
        v.detail = resolved.note.empty()
                       ? "Could not open the disc image or its CUE-referenced BIN file."
                       : resolved.note;
        return v;
    }
    v.opened = true;
    const uint64_t size = (uint64_t)f.tellg();

    // PVD: try raw (2352) then cooked (2048) sector 16.
    uint8_t sector[2048];
    if ((size >= (16ull * 2352ull + 24ull + sizeof(sector))) &&
        read_at(f, 16ull * 2352ull + 24ull, sector, sizeof(sector)) && is_iso_pvd(sector)) {
        v.has_header = true;
    } else if ((size >= (16ull * 2048ull + sizeof(sector))) &&
               read_at(f, 16ull * 2048ull, sector, sizeof(sector)) && is_iso_pvd(sector)) {
        v.has_header = true;
    }

    if (!v.has_header) {
        v.detail = "No ISO9660 CD001 header was found at the standard PS1 disc locations.";
        // Region may still be inferable from the expected serial for display.
        v.region = region_from_serial(expected_serial);
        return v;
    }

    // PVD volume identifier: offset 40, 32 bytes (space-padded).
    {
        std::string vol((const char*)&sector[40], 32);
        const size_t last = vol.find_last_not_of(" \t\0");
        if (last != std::string::npos) vol.erase(last + 1); else vol.clear();
        v.volume_id = vol;
    }

    // Scan the early image for the boot serial + (if given) the expected serial.
    const size_t scan_len = (size_t)std::min<uint64_t>(size, 16ull * 1024ull * 1024ull);
    std::vector<uint8_t> scan(scan_len);
    if (read_at(f, 0, scan.data(), scan.size())) {
        v.detected_serial = scan_boot_serial(scan);

        if (v.expected_serial_given) {
            // Match either the game-id form (SCUS-94236) or the EXE form (SCUS_942.36).
            const std::string serial_id = uppercase_ascii(expected_serial);
            std::string exe_id = serial_id;  // SCUS-94236 -> SCUS_942.36
            if (serial_id.size() == 10 && serial_id[4] == '-')
                exe_id = serial_id.substr(0, 4) + "_" + serial_id.substr(5, 3) + "." +
                         serial_id.substr(8, 2);
            auto contains = [&](const std::string& needle) {
                if (needle.empty() || needle.size() > scan.size()) return false;
                return std::search(scan.begin(), scan.end(), needle.begin(), needle.end()) !=
                       scan.end();
            };
            v.serial_matches = contains(serial_id) || contains(exe_id);
            if (!v.serial_matches && !v.detected_serial.empty() &&
                v.detected_serial == serial_id)
                v.serial_matches = true;  // boot line agrees even if the literal bytes differ
        }
    } else {
        v.detail = "The ISO header is present, but the image could not be scanned.";
    }

    // Region: prefer the disc's own serial, fall back to the expected one.
    v.region = region_from_serial(!v.detected_serial.empty() ? v.detected_serial
                                                             : expected_serial);

    // CRC32 (full image), streamed.
    if (compute_crc) {
        v.crc          = crc32_stream(f);
        v.crc_computed = true;
        if (has_expected_crc) v.crc_matches = (v.crc == expected_crc);
    }

    return v;
}

}  // namespace PSXRecompV4