feature(sdk): Add support for signing v2 transactions

[n8maninger]

Signing v2 transactions has a slightly different flow and structure from V1.

1. Build the transaction
2. Calculate the input sig hash
3. Sign the input sighash for each siacoin and siafund input using its private key

const state, network; // should be retrieved from the API

const txn = {
    "siacoinInputs": [
      {
        "parent": {
          "id": "a2b01527c128eebd19056d5048d6b18b31df1fa9589993c55d50607dc097e69c",
          "stateElement": {
            "leafIndex": 4646,
            "merkleProof": [
              "aac548e6cdd2f05daa89ce83b1935bb1f2d4b363a1d27ed3158f8157d209eea7",
              "211e336ba260f72dbe8059e7e564414cda75386ebaf79720ee1078e6aa513e15",
              "3ad4326fae446f729679cdb80fd1ea55c184c025bf228cd4cf49471be9c517f6"
            ]
          },
          "siacoinOutput": {
            "value": "424999930000000000000000000000",
            "address": "2b8fc779876872055333fa0609f37a604be076e97bfeeab4d1c7df7d02f9cff3b8e6317047fa"
          },
          "maturityHeight": 0
        }
      }
    ],
    "siacoinOutputs": [
      {
        "value": "15000000000000000000000000000",
        "address": "2e5716a6ba598292b2c0233fcc9e21f992c5f536ae1e0634907855224d5e9216a0c1256e0085"
      },
      {
        "value": "409999918000000000000000000000",
        "address": "2b8fc779876872055333fa0609f37a604be076e97bfeeab4d1c7df7d02f9cff3b8e6317047fa"
      }
    ],
    "minerFee": "12000000000000000000000"
  },
  sigHash = wallet.v2TransactionInputSigHash(state, network, txn);

txn.siacoinInputs.forEach((input) => {
    const privateKey = getPrivateKeyForAddress(input.parent.siacoinOutput.address),
      unlockCondtions = getUnlockConditionsForAddress(input.parent.siacoinOutput.address); // I can't remember if you store this as the policy or unlock conditions on the address or in the local storage

    input.satisfiedPolicy = {
      "policy": {
        "type": "uc",
        "policy": unlockCondtions
      },
      "signatures": [
        wallet.signHash(privateKey, sigHash)
      ]
    };
});

txn.siafundInputs.forEach((input) => {
  const privateKey = getPrivateKeyForAddress(input.parent.siacoinOutput.address),
    unlockCondtions = getUnlockConditionsForAddress(input.parent.siacoinOutput.address);

  input.satisfiedPolicy = {
    "policy": {
      "type": "uc",
      "policy": unlockCondtions
    },
    "signatures": [
      wallet.signHash(privateKey, sigHash)
    ]
  };
});

/*
{
  "siacoinInputs": [
    {
      "parent": {
        "id": "a2b01527c128eebd19056d5048d6b18b31df1fa9589993c55d50607dc097e69c",
        "stateElement": {
          "leafIndex": 4646,
          "merkleProof": [
            "aac548e6cdd2f05daa89ce83b1935bb1f2d4b363a1d27ed3158f8157d209eea7",
            "211e336ba260f72dbe8059e7e564414cda75386ebaf79720ee1078e6aa513e15",
            "3ad4326fae446f729679cdb80fd1ea55c184c025bf228cd4cf49471be9c517f6"
          ]
        },
        "siacoinOutput": {
          "value": "424999930000000000000000000000",
          "address": "2b8fc779876872055333fa0609f37a604be076e97bfeeab4d1c7df7d02f9cff3b8e6317047fa"
        },
        "maturityHeight": 0
      },
      "satisfiedPolicy": {
        "policy": {
          "type": "uc",
          "policy": {
            "timelock": 0,
            "publicKeys": [
              "ed25519:9dd50ac053764d67b6bcee937a1186c7d3341daedd326f6022afca8c4021d6bb"
            ],
            "signaturesRequired": 1
          }
        },
        "signatures": [
          "c21ac65cd105460879dfdaa37cf7efabf42e7978f85c7e1fe73f95c4637b3e0b64dd43f052a9f59194abfc0ba678d4c9e9122a821c9a7a5b45c4c204e8d2470d"
        ]
      }
    }
  ],
  "siacoinOutputs": [
    {
      "value": "15000000000000000000000000000",
      "address": "2e5716a6ba598292b2c0233fcc9e21f992c5f536ae1e0634907855224d5e9216a0c1256e0085"
    },
    {
      "value": "409999918000000000000000000000",
      "address": "2b8fc779876872055333fa0609f37a604be076e97bfeeab4d1c7df7d02f9cff3b8e6317047fa"
    }
  ],
  "minerFee": "12000000000000000000000"
}
*/

I'm hoping you'll be able to use this API to construct the transaction instead of using /fund and /fundsf separately: SiaFoundation/walletd#211

The request body is the Siacoin and Siafund recipients. The response is an unsigned transaction.

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[alexfreska]

Looks good, I'll give it a go and see if I hit any issues.

Just need to fix an issue with the commit formatting 😆:

feat(sdk): add support for signing v2 transactions

error:

⧗   input: feature(sdk): Add support for signing v2 transactions
✖   subject must not be sentence-case, start-case, pascal-case, upper-case [subject-case]
✖   type must be one of [build, chore, ci, docs, feat, fix, perf, refactor, revert, style, test] [type-enum]

✖   found 2 problems, 0 warnings