Fixed reading incomplete event JSON strings from the stream

[ihor]

Overview

The event handler code that processes the stream input expects chunks to be full event strings (from the beginning of the string until the end of line character), which is not always true.

outputStream._write = async (chunk, encoding, done) => {
    chunk.toString().split("\n")
        .filter(str => str.startsWith('data'))

Because of that, sometimes incomplete JSON strings are read from the stream, which results in the following errors:

Error while processing an event.
Event: data:{"DeployProcessed":{"deploy_hash":"af4f25e8236afecacf24ec45751e6de5af06682280cbf3d3bc6adea9749fb185","account":"018267d68f8d249b1430551ecc7b4c176d66f2ba2bf98d5547e7c3accc99375e53","timestamp":"2021-01-28T12:49:18.335Z","ttl":"1h","dependencies":[],"block_hash":"f0462bfeec91c520b7f139311037d703119053a935d88cb969027bfde22c72e0","execution_result":{"Success":{"effect":{"operations":[{"key":"deploy-af4f25e8236afecacf24ec45751e6de5af06682280cbf3d3bc6adea9749fb185","kind":"Write"},{"key":"hash-16f7f0d0899fc928adc13b1f5e4f857a03729e09ce9b651ce24d175c6d06ad99","kind":"Read"},{"key":"uref-36db58a395b29be22b6760ad56a1e3c7834988c9c60a5e74677dd65c21fceeaf-000","kind":"Write"},{"key":"account-hash-f5c8e69a44360b63a0d2f4bbe46648c05cb935417faa8b2e67deae29f6f2eae4","kind":"Write"},{"key":"hash-1bf3224baf001c6410f5cd6820924114d40be93cbb912432001cac9f62c0d0ce","kind":"Read"},{"key":"hash-ac387ec1e25673f8dd79e221a79e4d9e2265d2fc2f52d8552614f559df0810b9","kind":"Read"},{"key":"uref-650196897547fe641f16f9e1bcd9d497c96d6b203e4b9a587b62fbf2f4587706-000","kind":"Write"},{"key":"transfer-7b3ec69713c3ec591a6aaca27bc7e901d3a8aa3474eef47a57500422fd5db34d","kind":"Write"},{"key":"uref-3bf3ef523f2b252abcd4cefcc9d96bd92c140c6b8901d7336884801585d3372d-000","kind":"Add"},{"key":"hash-be8d196e566c19405a948944b2063ee575f363d6c0525ce65715d9a07bd73446","kind":"Read"},{"key":"uref-4d5c3ab2d09c09e76130d70cb9cd940eb6a37c16b2ac3100c6850914533c02b9-000","
Error: SyntaxError: Unexpected end of JSON input

Error while processing an event.
Event: data:{"FinalitySignature":{"block_hash":"5d586c6985567f897598148639c8413ea2f37b8173bcccd264629fb5757f669e","era_id":22,"signature":"01fc98d03c28d1d2c8bc849cd7c0822485050ed91ab88242eebe26797746cdedef3349923b6d53890ec9751163fb34de3c48ece283bc80062399cfc52991c1600a","public_key":"018b15761be0c5271
Error: SyntaxError: Unexpected end of JSON input

In this PR, I wrapped the original stream into the readline interface to ensure only full lines are passed to the consumer.

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Notes

I tried to preserve the original code structure. Not sure if it was needed.

[George-cl]

Nice one!