Blockdaemon Chain Watch - streaming on-chain events in real-time

In this example we'll use the Event Streaming service to monitor any on-chain transfers to the PEPE smart contract
Requirements:
- Go lang
- Blockdaemon REST API key
- Reverse proxy service
- HTTPie & jq CLI tools
Docs: https://docs.blockdaemon.com/reference/events-introduction

Step 1. Run webhook receiver (includes a Challenge Response Check)

the sample webhook server will respond to CRC token checks with the secret "mysecret123"
all webhook posts will be printed to the console
the service will listen on port 8082

go run webhookserver.go

Step 2. Publish the webhook server socket

ngrok reverse proxy is used as an example to publish the server
register for ngrok account or publish through your own methods

# set the Webhook Server FQDN
export WEBHOOKSERVERFQDN=XXXX.ngrok-free.app

# start the reverse proxy
ngrok http --domain=$WEBHOOKSERVERFQDN http://localhost:8082

Step 3.

# set Blockdaemon API key variable
export XAPIKey=XXXXX

# note Event Streaming protocol capabilities
http GET https://svc.blockdaemon.com/streaming/v2/ \
  X-Api-Key:$XAPIKey

# create webhook target - set the ngrok domain and note secret matches webhook server
TARGET_ID=$(http POST https://svc.blockdaemon.com/streaming/v2/targets \
    X-Api-Key:$XAPIKey \
    name='smartcontract webhook target' \
    description='Sample Go Webhookserver target' \
    max_buffer_count:=100 \
    settings:='{"destination": "https://'"$WEBHOOKSERVERFQDN"'", "method": "POST", "secret": "mysecret123"}' \
    type='webhook' \
    | jq -r .id)

# get the webhook target status - should be "connected"
http GET https://svc.blockdaemon.com/streaming/v2/targets \
    X-Api-Key:$XAPIKey

Step 4.

# create a smart contract address variable key
VARIABLE_ID=$(http POST https://svc.blockdaemon.com/streaming/v2/variables \
    X-Api-Key:$XAPIKey \
    name='smart contract addresses' \
    description='smart contract addresses' \
    type='string' \
    | jq -r .id)

# set the variable key value to the PEPE token contract address 0x6982508145454Ce325dDbE47a25d4ec3d2311933
http POST https://svc.blockdaemon.com/streaming/v2/variables/$VARIABLE_ID/values \
    X-Api-Key:$XAPIKey \
    value='0x6982508145454Ce325dDbE47a25d4ec3d2311933'

Step 5.

# create rule combing the webhook target, the blockchain (Ethereum Mainnet), and the target address
RULE_ID=$(http POST https://svc.blockdaemon.com/streaming/v2/rules \
    X-Api-Key:$XAPIKey \
    name='Ethereum mainnet rule' \
    description='Ethereum mainnet rule' \
    network='mainnet' \
    protocol='ethereum' \
    condition:='[{"variable_type": "address", "variable_id": "'"$VARIABLE_ID"'"}]' \
    target="$TARGET_ID" \
    condition_type='match_var' \
    is_active:=true \
    template='ALL_DATA')

# validate the rule
http GET https://svc.blockdaemon.com/streaming/v2/rules \
    X-Api-Key:$XAPIKey

Step 6.

Observe the webhook events in the webhookserver output. Example below:

{
  "data": {
    "accessList": [],
    "additionalFields": {
      "yParity": "0x0"
    },
    "blockHash": "0xfc57c0ce8f94d133863f21dda0943b553e792e5fd1b9e687c680aa1b286bfd1f",
    "blockNumber": "0x12b845b",
    "chainId": "0x1",
    "contractAddress": null,
    "creates": null,
    "cumulativeGasUsed": "0x1bfc64d",
    "effectiveGasPrice": "0x2bad348ab",
    "from": "0xcAFb5420CE411476ef43CCeEa50e71A95b6Ad5B0",
    "gas": "0x163ed",
    "gasPrice": "0x2bad348ab",
    "gasUsed": "0xd986",
    "hash": "0x06424f8c03c746ea1ccf3167d454a4ca54351bb4b179c9b3803455872cc31248",
    "input": "0xa9059cbb00000000000000000000000031da1b45d2570b5722618b8b43b0c805114048ee00000000000000000000000000000000000000000031c7ea725f3bca431e6000",
    "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080000000000000008000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000010000004000000000000000000000000000000000000000000000000000000000200000000000040000000000000000000000000000000002000000000000000000000000000000002000000000400000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000008000",
    "maxFeePerGas": "0x40c933ae2",
    "maxPriorityFeePerGas": "0xecd10",
    "nonce": "0x3d6",
    "publicKey": null,
    "r": "0x2b12ee7984f96db6cf16a190e257caa0392fa8961243488ff07caa4931adaffe",
    "raw": null,
    "root": null,
    "s": "0x6ed8f306cdfa24c4aea4f30ec5cfb853dfe90adc6d32db37d60195e36e3b1422",
    "status": "0x1",
    "timestamp": 1712799383,
    "to": "0x6982508145454Ce325dDbE47a25d4ec3d2311933",
    "transactionIndex": "0xd0",
    "type": "0x2",
    "uuid": "8e695b82-7ed3-4ab0-894d-bce7a91077a6",
    "v": "0x0",
    "value": "0x0"
  },
  "event_type": "confirmed_tx",
  "network": "mainnet",
  "protocol": "ethereum",
  "rule_id": "34b775e7-4425-4487-9181-0436022588fc",
  "target_id": "9c6b6a09-dd23-40b7-bb57-7aa0673f2a20"
}

where:

data.input: 0xa9059cbb00000000000000000000000031da1b45d2570b5722618b8b43b0c805114048ee00000000000000000000000000000000000000000031c7ea725f3bca431e6000

ABI decodes to:

      "definition": "transfer(address,uint256)",
      "decodedInputs": [
        "0x31DA1B45d2570B5722618B8b43b0C805114048EE",
        "60181440870692720000000000"
      ]

meaning 60181440870692720000000000 PEPE was transferred from 0xcAFb5420CE411476ef43CCeEa50e71A95b6Ad5B0 to 0x31DA1B45d2570B5722618B8b43b0C805114048EE

Step 7.

# delete the rule to halt further notifitions
http DELETE https://svc.blockdaemon.com/streaming/v2/rules/$RULE_ID \
    X-Api-Key:$XAPIKey

Blockdaemon/demo-event-streaming