Cloud support / Dropbox OAuth reference client (#659)

* bioms shouldn't be masked or the style selection box is useless
* fix: misleading comment
* Fix: calculating absolute flux from precipitation normal-value.
* Fix: River automatic rerender on regeneration.
* Dropbox OAuth implementation and Cloud framework
* add some space
* removing unnecessary logs, defer script load

Created by: Mészáros Gergely <monk@geotronic.hu>

modules/cloud.js

@@ -0,0 +1,141 @@
+"use strict";
+
+/*
+Cloud provider implementations (Dropbox only as now)
+
+provider Interface:
+
+name: name of the provider
+async auth(): authenticate and get access tokens from provider
+async save(filename): save map file to provider as filename
+async load(filename): load filename from provider
+async list(): list available filenames at provider
+async getLink(filePath): get shareable link for file
+restore(): restore access tokens from storage if possible
+
+*/
+
+window.Cloud = (function () {
+
+  // helpers to use in providers for token handling
+  const lSKey = x => `auth-${x}`
+  const setToken = (prov, key) => localStorage.setItem(lSKey(prov), key)
+  const getToken = prov => localStorage.getItem(lSKey(prov))
+
+  /**********************************************************/
+  /* Dropbox provider                                       */
+  /**********************************************************/
+
+  const DBP = {
+    name: 'dropbox',
+    clientId: 'sp7tzwm27u2w5ns',
+    authWindow: undefined,
+    token: null, // Access token
+    api: null,
+
+    restore() {
+      this.token = getToken(this.name)
+      if (this.token) this.connect(this.token)
+    },
+
+    async call(name, param) {
+      try {
+        return await this.api[name](param)
+      } catch (e) {
+        if (e.name !== "DropboxResponseError") throw(e)
+        // retry with auth
+        await this.auth()
+        return await this.api[name](param)
+      }
+    },
+
+    connect(token) {
+      const clientId = this.clientId
+      const auth = new Dropbox.DropboxAuth({ clientId })
+      auth.setAccessToken(token)
+      this.api = new Dropbox.Dropbox({ auth })
+    },
+
+    async save(fileName, contents) {
+      if (!this.api) await this.auth()
+      const resp = this.call('filesUpload', { path: '/' + fileName, contents })
+      console.log("Dropbox response:", resp)
+      return true
+    },
+
+    async load(path) {
+      if (!this.api) await this.auth()
+      const resp = await this.call('filesDownload', { path })
+      const blob = resp.result.fileBlob
+      if (!blob) throw(new Error('Invalid response from dropbox.'))
+      return blob
+    },
+
+    async list() {
+      if (!this.api) return null
+      const resp = await this.call('filesListFolder', { path: '' })
+      return resp.result.entries.map(e => ({ name: e.name, path: e.path_lower }))
+    },
+
+    auth() {
+        const url = window.location.origin + window.location.pathname + 'dropbox.html'
+        this.authWindow = window.open(url, 'auth', 'width=640,height=480')
+        // child window expected to call
+        // window.opener.Cloud.providers.dropbox.setDropBoxToken (see below)
+        return new Promise((resolve, reject) => {
+          const watchDog = () => {
+            this.authWindow.close()
+            reject(new Error("Timeout. No auth for dropbox."))
+          }
+          setTimeout(watchDog, 120*1000)
+          window.addEventListener('dropboxauth', e => {
+            clearTimeout(watchDog)
+            resolve()
+          })
+        })
+    },
+
+    // Callback function for auth window.
+    setDropBoxToken(token) {
+      console.log('Access token got:', token)
+      setToken(this.name, token)
+      this.connect(token)
+      this.authWindow.close()
+      window.dispatchEvent(new Event('dropboxauth'))
+    },
+
+    async getLink(path) {
+      if (!this.api) await this.auth()
+      let resp
+
+      // already exists?
+      resp = await this.call('sharingListSharedLinks', { path })
+      if (resp.result.links.length)
+        return resp.result.links[0].url
+
+      // create new
+      resp = await this.call('sharingCreateSharedLinkWithSettings', {
+        path,
+        settings: {
+          require_password: false,
+          audience: 'public',
+          access: 'viewer',
+          requested_visibility: 'public',
+          allow_download: true,
+        }
+      })
+      console.log("dropbox link object:", resp.result)
+      return resp.result.url
+    },
+  }
+
+  // register providers here:
+  const providers = {
+    dropbox: DBP,
+  }
+
+  // restore all providers at startup
+  for (const p of Object.values(providers)) p.restore()
+
+  return { providers }
+})()