package blockchain;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.Objects;

/**
 * ============================================================================
 *  BchBlockEntry — запись блокчейна SHiNE (.bch)
 * ============================================================================
 *
 * RAW (BigEndian):
 *   [4]  recordSize        = RAW_HEADER_SIZE + body.length
 *   [4]  recordNumber
 *   [8]  timestamp         UNIX time (секунды)
 *   [M]  bodyBytes         (внутри body первые 4 байта = [type][ver])
 *
 * FULL:
 *   RAW + signature64 + hash32
 *
 * ============================================================================
 */
public class BchBlockEntry {

    // ---- Константы размеров ----
    public static final int SIGNATURE_LEN = 64;
    public static final int HASH_LEN      = 32;

    /** RAW заголовок теперь: size + number + timestamp */
    public static final int RAW_HEADER_SIZE = 4 + 4 + 8; // 16

    // ---- Поля RAW-заголовка ----
    public final int   recordSize;        // [4]  M + 16
    public final int   recordNumber;      // [4]
    public final long  timestamp;         // [8]
    public final byte[] body;             // [M]  тело записи (начинается с type/ver)

    // ---- Поля подписи и хэша ----
    private byte[] signature64;           // [64]
    private byte[] hash32;                // [32]

    // ---- Кэшированные представления ----
    public final byte[] rawBytes;         // RAW без подписи/хэша
    private byte[] rawBytesWithSignatureAndHash; // FULL (может быть null)

    // ========================================================================
    //                     КОНСТРУКТОР №1 — из полей (RAW only)
    // ========================================================================
    public BchBlockEntry(int recordNumber,
                         long timestamp,
                         byte[] body) {
        Objects.requireNonNull(body, "body == null");

        this.recordNumber = recordNumber;
        this.timestamp    = timestamp;
        this.body         = Arrays.copyOf(body, body.length);
        this.recordSize   = body.length + RAW_HEADER_SIZE;

        ByteBuffer buf = ByteBuffer
                .allocate(RAW_HEADER_SIZE + body.length)
                .order(ByteOrder.BIG_ENDIAN);

        buf.putInt(recordSize);
        buf.putInt(recordNumber);
        buf.putLong(timestamp);
        buf.put(body);

        this.rawBytes = buf.array();
    }

    // ========================================================================
    //             КОНСТРУКТОР №2 — из полного массива (RAW + SIG + HASH)
    // ========================================================================
    public BchBlockEntry(byte[] rawWithSigAndHash) {
        Objects.requireNonNull(rawWithSigAndHash, "rawWithSigAndHash == null");
        if (rawWithSigAndHash.length < RAW_HEADER_SIZE + SIGNATURE_LEN + HASH_LEN)
            throw new IllegalArgumentException("Слишком мало данных для полного блока");

        ByteBuffer probe = ByteBuffer.wrap(rawWithSigAndHash).order(ByteOrder.BIG_ENDIAN);
        int rs = probe.getInt(); // recordSize
        if (rs < RAW_HEADER_SIZE)
            throw new IllegalArgumentException("Некорректный recordSize: " + rs);
        if (rawWithSigAndHash.length < rs + SIGNATURE_LEN + HASH_LEN)
            throw new IllegalArgumentException("Данные короче, чем raw+sig+hash");

        this.rawBytes = Arrays.copyOfRange(rawWithSigAndHash, 0, rs);

        ByteBuffer buf = ByteBuffer.wrap(this.rawBytes).order(ByteOrder.BIG_ENDIAN);
        this.recordSize   = buf.getInt();
        this.recordNumber = buf.getInt();
        this.timestamp    = buf.getLong();

        int bodyLen = this.recordSize - RAW_HEADER_SIZE;
        if (bodyLen < 0 || bodyLen != this.rawBytes.length - RAW_HEADER_SIZE)
            throw new IllegalArgumentException("Неконсистентная длина тела блока");

        this.body = new byte[bodyLen];
        buf.get(this.body);

        // подпись + хэш
        ByteBuffer tail = ByteBuffer
                .wrap(rawWithSigAndHash, rs, SIGNATURE_LEN + HASH_LEN)
                .order(ByteOrder.BIG_ENDIAN);

        this.signature64 = new byte[SIGNATURE_LEN];
        tail.get(this.signature64);
        this.hash32 = new byte[HASH_LEN];
        tail.get(this.hash32);

        this.rawBytesWithSignatureAndHash =
                Arrays.copyOf(rawWithSigAndHash, rs + SIGNATURE_LEN + HASH_LEN);
    }

    // ========================================================================
    //                        Добавить подпись и хэш
    // ========================================================================
    public BchBlockEntry addSignatureAndHash(byte[] signature64, byte[] hash32) {
        Objects.requireNonNull(signature64, "signature64 == null");
        Objects.requireNonNull(hash32, "hash32 == null");
        if (signature64.length != SIGNATURE_LEN) throw new IllegalArgumentException("signature64 != 64");
        if (hash32.length != HASH_LEN) throw new IllegalArgumentException("hash32 != 32");

        this.signature64 = Arrays.copyOf(signature64, SIGNATURE_LEN);
        this.hash32 = Arrays.copyOf(hash32, HASH_LEN);

        byte[] full = new byte[this.rawBytes.length + SIGNATURE_LEN + HASH_LEN];
        System.arraycopy(this.rawBytes, 0, full, 0, this.rawBytes.length);
        System.arraycopy(this.signature64, 0, full, this.rawBytes.length, SIGNATURE_LEN);
        System.arraycopy(this.hash32, 0, full, this.rawBytes.length + SIGNATURE_LEN, HASH_LEN);
        this.rawBytesWithSignatureAndHash = full;
        return this;
    }

    // ========================================================================
    //                              Геттеры
    // ========================================================================
    public byte[] getSignature64() { return signature64 == null ? null : Arrays.copyOf(signature64, SIGNATURE_LEN); }
    public byte[] getHash32()      { return hash32 == null ? null : Arrays.copyOf(hash32, HASH_LEN); }
    public byte[] getRawBytesWithSignatureAndHash() {
        return rawBytesWithSignatureAndHash == null ? null : Arrays.copyOf(rawBytesWithSignatureAndHash, rawBytesWithSignatureAndHash.length);
    }

    // ========================================================================
    //                              Отладка
    // ========================================================================
    @Override
    public String toString() {
        return String.format(
                "BchBlock[num=%d, time=%d, raw=%d, full=%s]",
                recordNumber, timestamp,
                rawBytes.length,
                rawBytesWithSignatureAndHash == null ? "null" : String.valueOf(rawBytesWithSignatureAndHash.length)
        );
    }
}