'use strict'

const debug = require('debug')('purs-loader')
const loaderUtils = require('loader-utils')
const Promise = require('bluebird')
const fs = Promise.promisifyAll(require('fs'))
const path = require('path')
const jsStringEscape = require('js-string-escape')
const PsModuleMap = require('./PsModuleMap');
const Psc = require('./Psc');
const PscIde = require('./PscIde');
const dargs = require('./dargs');

const requireRegex = /require\(['"]\.\.\/([\w\.]+)['"]\)/g

module.exports = function purescriptLoader(source, map) {
  const callback = this.async()
  const config = this.options
  const query = loaderUtils.parseQuery(this.query)
  const webpackOptions = this.options.purescriptLoader || {}

  const options = Object.assign({
    context: config.context,
    psc: 'psc',
    pscArgs: {},
    pscBundle: 'psc-bundle',
    pscBundleArgs: {},
    pscIde: false,
    pscIdeColors: webpackOptions.psc === 'psa' || query.psc === 'psa',
    pscIdeArgs: {},
    bundleOutput: 'output/bundle.js',
    bundleNamespace: 'PS',
    bundle: false,
    warnings: true,
    output: 'output',
    src: [
      path.join('src', '**', '*.purs'),
      path.join('bower_components', 'purescript-*', 'src', '**', '*.purs')
    ]
  }, webpackOptions, query)

  this.cacheable && this.cacheable()

  let cache = config.purescriptLoaderCache = config.purescriptLoaderCache || {
    rebuild: false,
    deferred: [],
    bundleModules: []
  }

  if (!config.purescriptLoaderInstalled) {
    config.purescriptLoaderInstalled = true

    // invalidate loader cache when bundle is marked as invalid (in watch mode)
    this._compiler.plugin('invalid', () => {
      debug('invalidating loader cache');

      cache = config.purescriptLoaderCache = {
        rebuild: options.pscIde,
        deferred: [],
        bundleModules: [],
        ideServer: cache.ideServer,
        psModuleMap: cache.psModuleMap
      }
    })

    // add psc warnings to webpack compilation warnings
    this._compiler.plugin('after-compile', (compilation, callback) => {
      if (options.warnings && cache.warnings) {
        compilation.warnings.unshift(`PureScript compilation:\n${cache.warnings}`)
        cache.warnings = null;
      }

      if (cache.errors) {
        compilation.errors.unshift(`PureScript compilation:\n${cache.errors}`)
        cache.errors = null;
      }

      callback()
    })
  }

  const psModuleName = PsModuleMap.match(source)
  const psModule = {
    name: psModuleName,
    load: js => callback(null, js),
    reject: error => callback(error),
    srcPath: this.resourcePath,
    srcDir: path.dirname(this.resourcePath),
    jsPath: path.resolve(path.join(options.output, psModuleName, 'index.js')),
    options: options,
    cache: cache,
  }

  debug('loader called', psModule.name)

  if (options.bundle) {
    cache.bundleModules.push(psModule.name)
  }

  if (cache.rebuild) {
    return PscIde.connect(psModule)
      .then(PscIde.rebuild)
      .then(toJavaScript)
      .then(psModule.load)
      .catch(psModule.reject)
  }

  if (cache.compilationFinished) {
    return toJavaScript(psModule).then(psModule.load).catch(psModule.reject)
  }

  // We need to wait for compilation to finish before the loaders run so that
  // references to compiled output are valid.
  cache.deferred.push(psModule)

  if (!cache.compilationStarted) {
    return Psc.compile(psModule)
       .then(() => PsModuleMap.makeMap(options.src).then(map => {
         debug('rebuilt module map');
         cache.psModuleMap = map;
       }))
      .then(() => Promise.map(cache.deferred, psModule => {
        if (typeof cache.ideServer === 'object') cache.ideServer.kill()
        return toJavaScript(psModule).then(psModule.load)
      }))
      .catch(error => {
        cache.deferred[0].reject(error)
        cache.deferred.slice(1).forEach(psModule => psModule.reject(new Error('purs-loader failed')))
      })
  }
}

function updatePsModuleMap(psModule) {
  const options = psModule.options
  const cache = psModule.cache
  const filePurs = psModule.srcPath
  if (!cache.psModuleMap) {
    debug('module mapping does not exist');
    return PsModuleMap.makeMap(options.src).then(map => {
      cache.psModuleMap = map;
      return cache.psModuleMap;
    });
  }
  else {
    return PsModuleMap.makeMapEntry(filePurs).then(result => {
      const map = Object.assign(cache.psModuleMap, result)
      cache.psModuleMap = map;
      return cache.psModuleMap;
    });
  }
}

// The actual loader is executed *after* purescript compilation.
function toJavaScript(psModule) {
  const options = psModule.options
  const cache = psModule.cache
  const bundlePath = path.resolve(options.bundleOutput)
  const jsPath = cache.bundle ? bundlePath : psModule.jsPath

  debug('loading JavaScript for', psModule.name)

  return Promise.props({
    js: fs.readFileAsync(jsPath, 'utf8'),
    psModuleMap: updatePsModuleMap(psModule)
  }).then(result => {
    let js = ''

    if (options.bundle) {
      // if bundling, return a reference to the bundle
      js = 'module.exports = require("'
             + jsStringEscape(path.relative(psModule.srcDir, options.bundleOutput))
             + '")["' + psModule.name + '"]'
    } else {
      // replace require paths to output files generated by psc with paths
      // to purescript sources, which are then also run through this loader.
      js = result.js
        .replace(requireRegex, (m, p1) => {
          return 'require("' + jsStringEscape(result.psModuleMap[p1].src) + '")'
        })
        .replace(/require\(['"]\.\/foreign['"]\)/g, (m, p1) => {
          return 'require("' + jsStringEscape(result.psModuleMap[psModule.name].ffi) + '")'
        })
    }

    return js
  })
}