Add ability to convert to/from PSBT0 and PSBT2

Author: NicolasDorier

NBitcoin.Tests/PSBT2Tests.cs

@@ -156,7 +156,7 @@ public void InvalidPSBT(string psbt)
 		[InlineData("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")]
 		[InlineData("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")]
 		[InlineData("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")]
-		public void ValidPSBTs(string psbt)
+		public void ValidPSBT2(string psbt)
 		{
 			var p = PSBT.Parse(psbt, Network.Main);
 			Assert.IsType<PSBT2>(p);
@@ -165,6 +165,18 @@ public void ValidPSBTs(string psbt)
 			Assert.Equal(psbt, Encoders.Hex.EncodeData(bytes));
 			Assert.Empty(p.Outputs.SelectMany(o => o.Unknown));
 			Assert.Empty(p.Inputs.SelectMany(o => o.Unknown));
+
+			var v0 = p.ToPSBTv0();
+			var v2 = v0.ToPSBTv2();
+			var expected = (PSBT2)p.Clone();
+			// Remove the fields that are not supported in PSBTv0.
+			// this information has been lost in the roundtrip
+			expected.FallbackLockTime = null;
+			expected.ModifiableFlags = null;
+			foreach (var input in expected.Inputs)
+				((PSBT2Input)input).UnifiedTimeLock = null;
+
+			Assert.Equal(expected.ToString(), v2.ToString());
 		}
 
 		[Fact]

NBitcoin/BIP174/PartiallySignedTransaction.cs

@@ -9,6 +9,7 @@
 using NBitcoin.BuilderExtensions;
 using System.Diagnostics.CodeAnalysis;
 using NBitcoin.BIP370;
+using NBitcoin.Protocol;
 
 namespace NBitcoin
 {
@@ -1286,6 +1287,65 @@ public PSBT RebaseKeyPaths(IHDKey accountKey, RootedKeyPath newRoot)
 		}
 		public Transaction GetGlobalTransaction() => GetGlobalTransaction(false);
 		internal abstract Transaction GetGlobalTransaction(bool @unsafe);
+
+		/// <summary>
+		/// If this instance is <see cref="PSBT0"/>, returns it.
+		/// Else, converts to a <see cref="PSBT0"/> instance.
+		/// </summary>
+		/// <returns>This instance, or a conversion</returns>
+		public PSBT0 ToPSBTv0()
+		{
+			if (this is PSBT0 p)
+				return p;
+			var maps = new Maps();
+			FillMaps(maps);
+			var global = this.GetGlobalTransaction(true);
+			int i = 0;
+			foreach (var b in PSBT2Constants.PSBT_V0_GLOBAL_EXCLUSIONSET)
+				maps[i].Remove([b]);
+			maps[i].Add(PSBTConstants.PSBT_GLOBAL_UNSIGNED_TX, global.ToBytes());
+			i++;
+			for (int o = 0; o < this.Inputs.Count; o++)
+			{
+				foreach (var b in PSBT2Constants.PSBT_V0_INPUT_EXCLUSIONSET)
+					maps[i].Remove([b]);
+				i++;
+			}
+			for (int o = 0; o < this.Outputs.Count; o++)
+			{
+				foreach (var b in PSBT2Constants.PSBT_V0_OUTPUT_EXCLUSIONSET)
+					maps[i].Remove([b]);
+				i++;
+			}
+			return new PSBT0(maps, Network);
+		}
+		/// <summary>
+		/// If this instance is <see cref="PSBT2"/>, returns it.
+		/// Else, converts to a <see cref="PSBT2"/> instance.
+		/// </summary>
+		/// <returns>This instance, or a conversion</returns>
+		public PSBT2 ToPSBTv2()
+		{
+			if (this is PSBT2 p)
+				return p;
+			var maps = new Maps();
+			FillMaps(maps);
+			var tx = GetGlobalTransaction(true);
+			maps[0].Remove([PSBTConstants.PSBT_GLOBAL_UNSIGNED_TX]);
+			maps[0].Add(PSBT2Constants.PSBT_GLOBAL_TX_VERSION, tx.Version);
+			maps[0].Add(PSBT2Constants.PSBT_GLOBAL_INPUT_COUNT, new VarInt((uint)tx.Inputs.Count));
+			maps[0].Add(PSBT2Constants.PSBT_GLOBAL_OUTPUT_COUNT, new VarInt((uint)tx.Outputs.Count));
+			int i = 1;
+			foreach (var txin in tx.Inputs)
+			{
+				PSBT2Input.FillMap(maps[i++], txin);
+			}
+			foreach (var txout in tx.Outputs)
+			{
+				PSBT2Output.FillMap(maps[i++], txout);
+			}
+			return new PSBT2(maps, Network);
+		}
 	}
 }
 #nullable disable

NBitcoin/BIP370/PSBT2.cs

@@ -15,7 +15,7 @@ internal PSBT2(Transaction tx, Network network): this(CreateMap(tx, network), ne
 	{
 	}
 
-	private static Maps CreateMap(Transaction tx, Network network)
+	internal static Maps CreateMap(Transaction tx, Network network)
 	{
 		var m = new Maps();
 		var global = m.NewMap();
@@ -39,9 +39,9 @@ internal PSBT2(Maps maps, Network network) : base(maps, network, PSBTVersion.PSB
 	{
 		var globalMap = maps[0];
 		if (globalMap.ContainsKey([PSBTConstants.PSBT_GLOBAL_UNSIGNED_TX]))
-		{
 			throw new FormatException("PSBT v2 must not contain PSBT_GLOBAL_UNSIGNED_TX");
-		}
+		if (globalMap.TryRemove<int>(PSBTConstants.PSBT_GLOBAL_VERSION, out var psbtVersion) && psbtVersion != 2)
+			throw new FormatException("PSBTv2 should have PSBT_GLOBAL_VERSION set to 2");
 
 		if (globalMap.TryRemove<uint>(PSBT2Constants.PSBT_GLOBAL_FALLBACK_LOCKTIME, out var v))
 			FallbackLockTime = new LockTime(v);