middleware-final.js

// In these examples

// transform args
module.exports = async (req, res, chain) => {
  let ce = create_cloudevent(req, res)
  chain.finalize(ce) // ends the chain, and calls the user function with these args
}

// or don't transform args
module.exports = async (req, res, chain) => {
  report_metrics(req, res)
  chain.next() // calls the next 
}

// append args
module.exports = async (req, res, chain) => {
  let context = create_context(req, res)
  ? // adds the context to the args
}

middleware-types.js

// In this example we have different types of middleware
// they explicitly do different types of things

// transform the function arguments before invoking
// also trap errors if you'd like
// question: what if more than one middleware wants to transform?
module.exports.$finalize = async (req, res, func) => {
  let ce = create_cloudevent(req, res)
  func(ce)
}

// or
module.exports.$finalize = async (req, res, func) => {
  let c = create_context(req, res)
  func.appendArg(c)
}

// like a preprocessor. can't change the args but can have side-effects
// this might log something, or report metrics
module.exports.$filter = async (req, res) => {
  // report some metrics
}