feat(spv): header sync, Merkle proofs, scripthash

src/Core/Spv/BlockHeaderInfo.cs

@@ -0,0 +1,53 @@
+using NBitcoin;
+using NBitcoin.Crypto;
+using PalladiumWallet.Core.Chain;
+
+namespace PalladiumWallet.Core.Spv;
+
+/// <summary>
+/// Header di blocco parsato dagli 80 byte canonici (blueprint §7.2):
+/// versione, prev_hash, merkle_root, timestamp, bits, nonce.
+/// </summary>
+public sealed record BlockHeaderInfo(
+    int Version, uint256 PrevHash, uint256 MerkleRoot, uint Timestamp, uint Bits, uint Nonce, uint256 Hash)
+{
+    public const int Size = 80;
+
+    public static BlockHeaderInfo Parse(string headerHex) => Parse(Convert.FromHexString(headerHex));
+
+    public static BlockHeaderInfo Parse(byte[] raw)
+    {
+        if (raw.Length != Size)
+            throw new ArgumentException($"Header di {raw.Length} byte (attesi {Size}).", nameof(raw));
+
+        return new BlockHeaderInfo(
+            Version: BitConverter.ToInt32(raw, 0),
+            PrevHash: new uint256(raw.AsSpan(4, 32)),
+            MerkleRoot: new uint256(raw.AsSpan(36, 32)),
+            Timestamp: BitConverter.ToUInt32(raw, 68),
+            Bits: BitConverter.ToUInt32(raw, 72),
+            Nonce: BitConverter.ToUInt32(raw, 76),
+            Hash: new uint256(Hashes.DoubleSHA256RawBytes(raw, 0, Size)));
+    }
+
+    /// <summary>
+    /// Validazione SPV dell'header (§7.2): collegamento al precedente e,
+    /// se il profilo non impone lo skip (catena LWMA), verifica PoW
+    /// hash &lt;= target dai bits. Il controllo di coerenza dei bits col
+    /// retargeting completo richiede la storia: per la catena di riferimento
+    /// è sostituito dai checkpoint (§7.3).
+    /// </summary>
+    public bool IsValidChild(uint256 expectedPrevHash, ChainProfile profile)
+    {
+        if (PrevHash != expectedPrevHash)
+            return false;
+        if (profile.SkipPowValidation)
+            return true;
+        var target = new Target(Bits).ToUInt256();
+        return Hash <= target;
+    }
+
+    /// <summary>Confronto con un checkpoint hardcoded (§7.3).</summary>
+    public bool MatchesCheckpoint(Checkpoint checkpoint) =>
+        Hash == uint256.Parse(checkpoint.BlockHash);
+}