# Sync committee API proposal

## GET /eth/v1/beacon/states/_{state_id}_/sync_committees
Obtain the sync committee for the given state ID.

### Parameters
- epoch (query, string, optional) fetch sync committees for the given epoch. If not present then the sync committees for the epoch of the state will be obtained

### Returns

{
  "data": {
    "validators": [ 
      1,
      2,
      3,
      4,
      5,
      6,
      7,
      8
    ],
    "aggregate_validators": [ 
      [
        1,
        2,
        3,
        4,
      ],
      [
        5,
        6,
        7,
        8,
      ] 
    ] 
  } 
}

### Open questions
- do we need to return `aggregate_validators`? This is a simple set of slices of `validators` so seems to be overkill, but reflects more closely the spec data structure.

## POST /eth/v1/validator/duties/sync/_{epoch}_
Obtain the sync committee duties for the provided validators.

### Parameters
- validators (body,string array) an array of the validator indices for which to obtain the duties.

### Returns

{
  "dependent_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
  "data": [
    {
      "pubkey": "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a",
      "validator_index": "1",
      "sync_committee_index": "2",
    }
  ]
}

### Notes
- although pubkey can be inferred from the index we return it to keep this call analogous with the one that fetches attester duties
- `sync_committee_index` is the index of the validator in the sync committee. This can be used to infer the subnet to which the contribution should be broadcast

## GET /eth/v1/validator/sync_committee_contribution
Aggregates all sync comittee signatures matching given beacon block root.

## POST /eth/v1/beacon/pool/sync_committees
Submit sync committee signatures to node.

### Body

[
  {
    "slot": 1,
    "beacon_block_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
    "validator_index": "1",
    "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
  }
]

## POST /eth/v1/validator/sync_committee_subscriptions
Signal beacon node to prepare a sync committee subnet.

### Body

[
  {
    "validator_index": "1",
    "sync_committee_index": "2",
    "is_aggregator": true
  }
]

### Notes
- we do not send the actual subnet to which we want to subscribe. This can be calculated by the beacon node given `sync_committee_index`

## GET /eth/v1/validator/sync_committee_contribution
Request a sync committee contribution.

### Parameters
- slot (query, string, required) the slot for which to fetch the contribution
- subcommittee_index (query, string, required) the subcommittee index for which to fetch the contribution
- beacon_block_root (query, string, required) the beacon block root for which to fetch the contribution

### Returns

{
  "data": {
    "slot": 1,
    "beacon_block_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
    "subcommittee_index": "3",
    "aggregation_bits": "0x01"
  }
}

## POST /eth/v1/validator/contribution_and_proofs
Publish multiple contribution and proofs.

### Body

[
  {
    "message": {
      "aggregator_index": "1",
      "contribution": {
        "slot": 1,
        "beacon_block_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
        "subcommittee_index": "3",
        "aggregation_bits": "0x01",
        "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
      },
      "selection_proof": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
    },
    "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
  }
]