/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/* eslint-disable no-template-curly-in-string  */

'use strict'

const { readdirSync } = require('fs')
const dedent = require('dedent')
const deepmerge = require('deepmerge')

function genFactory (folder) {
  // get all the API files
  const apiFiles = readdirSync(folder)
  const types = apiFiles
    .map(file => {
      const name = file
        .slice(0, -3)
        .replace(/\.([a-z])/g, k => k[1].toUpperCase())
        .replace(/_([a-z])/g, k => k[1].toUpperCase())

      return file
        .slice(0, -3) // remove `.js` extension
        .split('.')
        .reverse()
        .reduce((acc, val) => {
          const obj = {
            [val]: acc === null
              ? `ApiMethod<RequestParams.${name[0].toUpperCase() + name.slice(1)}>`
              : acc
          }
          if (isSnakeCased(val)) {
            obj[camelify(val)] = acc === null
              ? `ApiMethod<RequestParams.${name[0].toUpperCase() + name.slice(1)}>`
              : acc
          }
          return obj
        }, null)
    })
    .reduce((acc, val) => deepmerge(acc, val), {})

  const apis = apiFiles
    .map(file => {
      // const name = format(file.slice(0, -3))
      return file
        .slice(0, -3) // remove `.js` extension
        .split('.')
        .reverse()
        .reduce((acc, val) => {
          const obj = {
            [val]: acc === null
              ? `lazyLoad('${file.slice(0, -3)}', opts)` // `${name}(opts)`
              : acc
          }
          if (isSnakeCased(val)) {
            obj[camelify(val)] = acc === null
              ? `lazyLoad('${file.slice(0, -3)}', opts)` // `${name}(opts)`
              : acc
          }
          return obj
        }, null)
    })
    .reduce((acc, val) => deepmerge(acc, val), {})

  // serialize the API object
  const apisStr = JSON.stringify(apis, null, 2)
    // split & join to fix the indentation
    .split('\n')
    .join('\n    ')
    // remove useless quotes
    .replace(/"/g, '')

  // serialize the type object
  const typesStr = Object.keys(types)
    .map(key => `${key}: ${JSON.stringify(types[key], null, 2)}`)
    .join('\n')
    // remove useless quotes and commas
    .replace(/"/g, '')
    .replace(/,/g, '')

  const fn = dedent`
  /*
   * Licensed to Elasticsearch B.V. under one or more contributor
   * license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright
   * ownership. Elasticsearch B.V. licenses this file to you under
   * the Apache License, Version 2.0 (the "License"); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */

  'use strict'

  const assert = require('assert')

  function ESAPI (opts) {
    assert(opts.makeRequest, 'Missing makeRequest function')
    assert(opts.ConfigurationError, 'Missing ConfigurationError class')
    assert(opts.result, 'Missing default result object')

    const { result } = opts
    opts.handleError = handleError
    opts.snakeCaseKeys = snakeCaseKeys

    const apis = ${apisStr}


    return apis

    function handleError(err, callback) {
      if (callback) return callback(err, result)
      return Promise.reject(err)
    }

    function snakeCaseKeys (acceptedQuerystring, snakeCase, querystring, warnings) {
      var target = {}
      var keys = Object.keys(querystring)
      for (var i = 0, len = keys.length; i < len; i++) {
        var key = keys[i]
        target[snakeCase[key] || key] = querystring[key]
        if (acceptedQuerystring.indexOf(snakeCase[key] || key) === -1) {
          warnings.push('Client - Unknown parameter: "' + key + '", sending it as query parameter')
        }
      }
      return target
    }
  }

  // It's unlikely that a user needs all of our APIs,
  // and since require is a sync operation that takes time
  // (given the amount of APIs we have), let's lazy load them,
  // so a given API file will be required only
  // if the user actually needs that API.
  // The following implementation takes advantage
  // of js closures to have a simple cache with the least overhead.
  function lazyLoad (file, opts) {
    var fn = null
    return function _lazyLoad (params, options, callback) {
      if (fn === null) {
        fn = require(${'`./api/${file}.js`'})(opts)
      }
      return fn(params, options, callback)
    }
  }

  module.exports = ESAPI
  `

  // new line at the end of file
  return { fn: fn + '\n', types: typesStr }
}

// from snake_case to camelCase
function camelify (str) {
  return str.replace(/_([a-z])/g, k => k[1].toUpperCase())
}

function isSnakeCased (str) {
  return !!~str.indexOf('_')
}

module.exports = genFactory