README.md

Origin EventSource

The Origin Marketplace contract emits events when users take actions such as creating listings or making offers. In order to arrive at the current state of a listing or offer, all prior events must be considered.

For example, the status property of a listing will need to change from available to sold once an offer has been made. For multi-unit listings, availableUnits will have to be decremented for every successful sale. Once availableUnits reaches 0, status should change from available to out of stock.

Ths module provides a simple API for retrieving the current state of a listing or offer. It works something like this:

1. Fetch all relevant events from the ethereum node for the given listing or offer
2. Fetch all IPFS objects for those events
3. Loop through the events and apply transformations and computations
4. Ensure objects match the relevant JSON Schema after each stage
5. Return the final state

Usage

import EventSource from '@origin/eventsource'

const eventSource = new EventSource({
  marketplaceContract: MarketplaceContractInstance,
  ipfsGateway: "https://ipfs.originprotocol.com"
})

const listing = eventSource.getListing('0')
console.log(listing)

const offer = eventSource.getOffer('0', '0')
console.log(offer)