#!/usr/bin/node
////////////////////////////////////////////////////////////////////////////////
//// Create AWS Service Promisified Functions
//// @author Michael Rosata
////
//// @dependencies ramda, yargs
////
//// @desc
////   Returns the code that would wrap every method from one AWS Service into
////   functions that return Promises rather than those returning Node style
////   callbacks.
////   The new functions are named similar to their original counterparts.
////   IE:
////     S3.getBucket() --> s3GetBucket()
////   It can also generate an entire module.export = {...} for the service.
////   in which case `s3getBucket` becomes `s3.getBucket`
////
//// @uses
////   node ./denode-aws-service-code.js --service s3
////   node ./denode-aws-service-code.js --service s3 --as-export
////   node ./denode-aws-service-code.js --service sqs --namespace SQS
////   node ./denode-aws-service-code.js --service sqs --promisify customFnName
////
const AWS = require('aws-sdk')
const argv = require('yargs').argv
const {
  map,
  filter,
  complement,
  pipe,
  either,
  equals,
  apply,
  join,
  propOr,
  toUpper,
} = require('ramda')


////
//// Command Line Arguments
const SERVICE = argv.service || argv.s || ''
const NS = argv.namespace || argv.ns || toUpper(SERVICE)
const AS_EXPORT = Boolean(argv.asExport || argv.e)
const PROMISIFY = argv.promisify || argv.p || 'denodify'


////
//// Utility Functions
////

// capitalize ::
const capitalize =
  s =>
  `${s.substr(0,1).toUpperCase()}${s.substr(1)}`

// getCode ::
const getCode =
  (ns, promisify) =>
  methods =>
  methods.map(name => `const ${ns}${capitalize(name)} = ${promisify}(${ns}.${name}, ${ns})`)

// getExport ::
const getExportCode =
  (ns, promisify) =>
  (methods = []) => [
    `module.exports = {`, // Declare and open object literal
    ...methods.map(name => `  ${name}: ${promisify}(${ns}.${name}, ${ns}),`),
    '}', // closed object literal
  ]

// notApiOrConstructor ::
const notApiOrConstructor = complement(
  either(
    equals('serviceIdentifier'),
    either(equals('api'), equals('constructor'))
  ))


////
//// Main Code
////

/**
 * Create Code which would promisify (denodify) an AWS service
 * into either a series of declared functions or as one namespace
 * that essentially has the same collection of methods as the
 * service being denodified
 *
 * @param {string} serviceName - name of service, ie: 's3', 'sqs'.
 * @param {string} [serviceNS] - namespace of service on AWS object. By
 *   default it assumes the `serviceName` capitalized.
 * @param {string} [promisify] - name of the promisify function.
 * @param {boolean} [asExport] - default false, create as object instead
 *   of having all individual functions.
 */
function denodeAwsServiceCode(serviceName, serviceNS = toUpper(serviceName), promisify = 'denodify', asExport = false) {
  // Create the service so we can get the method names from its __proto__
  const service = new AWS[serviceNS]()

  // Depending on whether the code will be one namespace or many functions, we need different builder
  const codeBuilder = asExport ? getExportCode : getCode

  // Get the keys, filter unwanted properties, build the code
  return pipe(
    x => Reflect.ownKeys(x.__proto__),
    filter(notApiOrConstructor),
    codeBuilder(serviceName, promisify),
    join('\n')
  )(service)
}


////
//// If Command Line Arguments Passed, then we shall execute the function
//// to to build and output code that promisifies the AWS 'SERVICE' service
if (SERVICE && NS) {
  const theCode = denodeAwsServiceCode(SERVICE, NS, PROMISIFY, AS_EXPORT)

  console.log(
    `/**\
    \n * AWS SERVICE ${NS} AS PROMISE RETURNING FUNCTIONS\
    \n */\
    \n\const AWS = require('aws-sdk')
    \n\
    \n// denodify ::\
    \nconst denodify =\
    \n  (fn, context = null) =>\
    \n  (...args) =>\
    \n    new Promise((resolve, reject) => {\
    \n      fn.call(context, ...args, (err, data) => {\
    \n        if (err) return reject(err)\
    \n        return resolve(data)\
    \n      })\
    \n    })\
    \n\
    \n////\
    \n//// Actual AWS Service:${NS}:\
    \nconst ${SERVICE} = new AWS.${NS}({/*..config..*/})\
    \n\
    \n////\
    \n//// Denodified Versions of ${SERVICE} API methods\
    \n${theCode}\
    \n`
  )
}


module.exports = denodeAwsServiceCode