improve config saving; fix pairing bug

lib/settings-loader.js

@@ -5,6 +5,7 @@ const _ = require('lodash/fp')
 const argv = require('minimist')(process.argv.slice(2))
 const pify = require('pify')
 
+const pgp = require('pg-promise')()
 const db = require('./db')
 const configValidate = require('./config-validate')
 
@@ -39,7 +40,7 @@ function isEquivalentField (a, b) {
 
 // b overrides a
 function mergeValues (a, b) {
-  return _.unionWith(isEquivalentField, b, a)
+  return _.reject(r => _.isNil(r.fieldValue), _.unionWith(isEquivalentField, b, a))
 }
 
 function load (versionId) {
@@ -125,6 +126,50 @@ function save (config) {
   .catch(() => db.none(sql, ['config', {config}, false]))
 }
 
+function configAddField (scope, fieldCode, value) {
+  return {
+    fieldLocator: {
+      fieldScope: {
+        crypto: scope.crypto,
+        machine: scope.machine
+      },
+      code: fieldCode
+    },
+    fieldValue: {value}
+  }
+}
+
+function configDeleteField (scope, fieldCode) {
+  return {
+    fieldLocator: {
+      fieldScope: {
+        crypto: scope.crypto,
+        machine: scope.machine
+      },
+      code: fieldCode
+    },
+    fieldValue: null
+  }
+}
+
+function modifyConfig (newFields) {
+  const TransactionMode = pgp.txMode.TransactionMode
+  const isolationLevel = pgp.txMode.isolationLevel
+  const tmSRD = new TransactionMode({tiLevel: isolationLevel.serializable})
+
+  function transaction (t) {
+    return loadLatest()
+    .then(settings => {
+      const oldConfig = settings.config
+      return save(mergeValues(oldConfig, newFields))
+    })
+  }
+
+  transaction.txMode = tmSRD
+
+  return db.tx(transaction)
+}
+
 module.exports = {
   settings,
   loadConfig,
@@ -132,5 +177,8 @@ module.exports = {
   loadLatest,
   save,
   loadFixture,
-  mergeValues
+  mergeValues,
+  modifyConfig,
+  configAddField,
+  configDeleteField
 }