Add method to parse bank transactions as JSON

This implements parsing of the Account Information Service format as
defined in the Berlin Group Group NextGenPSD2 XS2A Framework, which
is widely used across various European banks.

This is a first step to replace the current bank import features with
a standardized JSON interface.

app/models/bank_account.rb

@@ -24,4 +24,8 @@ class BankAccount < ApplicationRecord
     end
     count
   end
+
+  def last_transaction_date
+    bank_transactions.order(date: :desc).first&.date
+  end
 end

lib/bank_account_information_importer.rb

@@ -0,0 +1,55 @@
+class BankAccountInformationImporter
+
+  def initialize(bank_account)
+    @bank_account = bank_account
+  end
+
+  def import!(content)
+    return nil if content.empty?
+    data = JSON.parse content, symbolize_names: true
+
+    return 0 if data.empty?
+    booked = data.fetch(:transactions, {}).fetch(:booked, [])
+
+    ret = 0
+    booked.each do |t|
+      amount = parse_account_information_amount t[:transactionAmount]
+      entityName = amount < 0 ? t[:creditorName] : t[:debtorName]
+      entityAccount = amount < 0 ? t[:creditorAccount] : t[:debtorAccount]
+
+      @bank_account.bank_transactions.where(external_id: t[:transactionId]).first_or_create.update({
+        date: t[:bookingDate],
+        amount: amount,
+        iban: entityAccount && entityAccount[:iban],
+        reference: t[:remittanceInformationUnstructured],
+        text: entityName,
+        receipt: t[:additionalInformation],
+      })
+      ret += 1
+    end
+
+    balances = Hash[ data[:balances] ? data[:balances].map { |b|  [b[:balanceType], b[:balanceAmount]] } : [] ]
+    balance = balances.values.first
+    %w(closingBooked expected authorised openingBooked interimAvailable forwardAvailable nonInvoiced).each do |type|
+      value = balances[type]
+      if value then
+        balance = value
+        break
+      end
+    end
+
+    @bank_account.balance = parse_account_information_amount(balance) || @bank_account.bank_transactions.sum(:amount)
+    @bank_account.import_continuation_point = booked.first&.fetch(:entryReference, nil)
+    @bank_account.last_import = Time.now
+    @bank_account.save!
+
+    ret
+  end
+
+  private
+
+  def parse_account_information_amount(value)
+    value && value[:amount].to_f
+  end
+
+end

spec/lib/bank_account_information_importer_spec.rb

@@ -0,0 +1,412 @@
+require_relative '../spec_helper'
+
+describe BankTransaction do
+  let(:bank_account) { create :bank_account }
+
+  it 'empty content' do
+    content = <<-JSON
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to be(nil)
+  end
+
+  it 'invalid JSON' do
+    content = <<-JSON
+      #invalid#
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect{importer.import!(content)}.to raise_error(JSON::ParserError)
+  end
+
+  it 'empty object' do
+    content = <<-JSON
+      {}
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(0)
+  end
+
+  it 'des sometet' do
+    content = <<-JSON
+      {
+        "balances": [],
+        "transactions": {}
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(0)
+  end
+
+  it 'without actual content' do
+    content = <<-JSON
+      {
+        "balances": [],
+        "transactions": {
+          "booked": []
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(0)
+  end
+
+  it 'use favorite balanceType' do
+    content = <<-JSON
+      {
+        "balances": [
+          {
+            "balanceType": "authorised",
+            "balanceAmount": {
+              "currency": "EUR",
+              "amount": "123.45"
+            }
+          },
+          {
+            "balanceType": "closingBooked",
+            "balanceAmount": {
+              "currency": "EUR",
+              "amount": "234.56"
+            }
+          },
+          {
+            "balanceType": "##UNKNOWN##",
+            "balanceAmount": {
+              "currency": "EUR",
+              "amount": "345.67"
+            }
+          },
+          {
+            "balanceType": "expected",
+            "balanceAmount": {
+              "currency": "EUR",
+              "amount": "456.78"
+            }
+          }
+        ]
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(0)
+    expect(bank_account.balance).to eq(234.56)
+  end
+
+  it 'use unknown balance if no other exists' do
+    content = <<-JSON
+      {
+        "balances": [
+          {
+            "balanceType": "##UNKNOWN##",
+            "balanceAmount": {
+              "currency": "EUR",
+              "amount": "123.45"
+            }
+          }
+        ]
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(0)
+    expect(bank_account.balance).to eq(123.45)
+  end
+
+  it 'use transaction sum as balance' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionId": "1",
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "12.3"
+              },
+              "bookingDate": "2019-02-14",
+              "valueDate": "2019-02-13",
+              "debtorName": "Example User"
+            },
+            {
+              "transactionId": "2",
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "-1.2"
+              },
+              "bookingDate": "2019-02-12",
+              "valueDate": "2019-02-11",
+              "debtorName": "Example Supplier"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(2)
+    expect(bank_account.last_transaction_date).to eq('2019-02-14'.to_date)
+    expect(bank_account.balance).to eq(11.1)
+  end
+
+  it 'can import debit entry' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "-194.83"
+              },
+              "creditorAccount": {
+                "iban": "DE72957284895783674747"
+              },
+              "creditorName": "Deutsche Bundesbahn",
+              "creditorId": "DE76356347538353",
+              "mandateId": "34564OB3633ZT3",
+              "remittanceInformationUnstructured": "743574386368 Muenchen-Hamburg 27.03.2019",
+              "bookingDate": "2019-02-13",
+              "valueDate": "2019-02-13",
+              "entryReference": "3648793450370305937",
+              "transactionId": "3648793450370305937",
+              "bankTransactionCode": "PMNT-RDDT-ESDD",
+              "additionalInformation": "Lastschrift"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(1)
+
+    bt = bank_account.bank_transactions.first
+    expect(bt.amount).to eq(-194.83)
+    expect(bt.date).to eq('2019-02-13'.to_date)
+    expect(bt.text).to eq('Deutsche Bundesbahn')
+    expect(bt.iban).to eq('DE72957284895783674747')
+    expect(bt.reference).to eq("743574386368 Muenchen-Hamburg 27.03.2019")
+    expect(bt.receipt).to eq('Lastschrift')
+  end
+
+  it 'can import US bank transfer' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "-238.68"
+              },
+              "originalAmount": {
+                "currency": "USD",
+                "amount": "-270.46"
+              },
+              "currencyExchange": {
+                "sourceCurrency": "EUR",
+                "targetCurrency": "USD",
+                "unitCurrency": "EUR",
+                "quotationDate": "2019-02-13",
+                "exchangeRate": "1.13315"
+              },
+              "creditorAccount": {
+                "bban": "693757683985"
+              },
+              "creditorAgent": "FRTZUSWA435",
+              "creditorName": "Hammersmith Inc.",
+              "creditorAddress": "1326 Canwood Drive, CA 45562, US",
+              "remittanceInformationUnstructured": "Martin Schöneicher, Inv# 123453423, Thx",
+              "endToEndId": "Corvette Ersatzteile",
+              "bookingDate": "2019-02-13",
+              "valueDate": "2019-02-13",
+              "entryReference": "8463794476737676345",
+              "transactionId": "8463794476737676345",
+              "bankTransactionCode": "PMNT-ICDT-XBCT",
+              "additionalInformation": "Auslands-Überweisung"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(1)
+
+    bt = bank_account.bank_transactions.first
+    expect(bt.amount).to eq(-238.68)
+    expect(bt.date).to eq('2019-02-13'.to_date)
+    expect(bt.text).to eq('Hammersmith Inc.')
+    expect(bt.iban).to be(nil)
+    expect(bt.reference).to eq('Martin Schöneicher, Inv# 123453423, Thx')
+    expect(bt.receipt).to eq('Auslands-Überweisung')
+  end
+
+  it 'can import bank fees' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "-12.3"
+              },
+              "creditorName": "superbank AG",
+              "remittanceInformationUnstructured": "Überweisung US, Wechselspesen u Provision",
+              "bookingDate": "2019-02-14",
+              "valueDate": "2019-02-13",
+              "entryReference": "3346453823263457367",
+              "transactionId": "3346453823263457367",
+              "bankTransactionCode": "ACMT-MCOP-CHRG",
+              "additionalInformation": "Spesen/Gebühren"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(1)
+
+    bt = bank_account.bank_transactions.first
+    expect(bt.amount).to eq(-12.3)
+    expect(bt.date).to eq('2019-02-14'.to_date)
+    expect(bt.text).to eq('superbank AG')
+    expect(bt.iban).to be(nil)
+    expect(bt.reference).to eq("Überweisung US, Wechselspesen u Provision")
+    expect(bt.receipt).to eq('Spesen/Gebühren')
+  end
+
+  it 'can import credit entry' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "136.47"
+              },
+              "debtorAccount": {
+                "iban": "AT251657674147449499"
+              },
+              "debtorName": "Maria Reithuber",
+              "remittanceInformationUnstructured": "Danke für's Auslegen",
+              "endToEndId": "Auslage von Martin S.",
+              "bookingDate": "2019-02-14",
+              "valueDate": "2019-02-14",
+              "entryReference": "4856465768967584736",
+              "transactionId": "4856465768967584736",
+              "bankTransactionCode": "PMNT-RCDT-ESCT",
+              "additionalInformation": "Gutschrift"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(1)
+
+    bt = bank_account.bank_transactions.first
+    expect(bt.amount).to eq(136.47)
+    expect(bt.date).to eq('2019-02-14'.to_date)
+    expect(bt.text).to eq('Maria Reithuber')
+    expect(bt.iban).to eq('AT251657674147449499')
+    expect(bt.reference).to eq("Danke für's Auslegen")
+    expect(bt.receipt).to eq('Gutschrift')
+  end
+
+  it 'use transaction sum as balance' do
+    content = <<-JSON
+      {
+        "transactions": {
+          "booked": [
+            {
+              "transactionId": "T1",
+              "entryReference": "E1",
+              "bookingDate": "2020-01-01",
+              "valueDate": "2020-01-02",
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "11"
+              },
+              "creditorName": "CN1",
+              "creditorAccount": {
+                "iban": "CH9300762011623852957"
+              },
+              "debtorName": "DN1",
+              "debtorAccount": {
+                "iban": "DE72957284895783674747"
+              },
+              "additionalInformation": "AI1"
+            },
+            {
+              "transactionId": "T2",
+              "entryReference": "E2",
+              "bookingDate": "2010-02-01",
+              "valueDate": "2010-02-02",
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "-22"
+              },
+              "creditorName": "CN2",
+              "creditorAccount": {
+                "iban": "CH9300762011623852957"
+              },
+              "debtorName": "DN2",
+              "debtorAccount": {
+                "iban": "DE72957284895783674747"
+              },
+              "remittanceInformationUnstructured": "RI2"
+            },
+            {
+              "transactionId": "T3",
+              "bookingDate": "2000-03-01",
+              "transactionAmount": {
+                "currency": "EUR",
+                "amount": "33"
+              },
+              "debtorName": "DN3"
+            }
+          ]
+        }
+      }
+    JSON
+
+    importer = BankAccountInformationImporter.new(bank_account)
+    expect(importer.import!(content)).to eq(3)
+    expect(bank_account.import_continuation_point).to eq('E1')
+    expect(bank_account.last_transaction_date).to eq('2020-01-01'.to_date)
+    expect(bank_account.balance).to eq(22)
+
+    bt1 = bank_account.bank_transactions.find_by_external_id("T1")
+    expect(bt1.amount).to eq(11)
+    expect(bt1.date).to eq('2020-01-01'.to_date)
+    expect(bt1.text).to eq('DN1')
+    expect(bt1.iban).to eq('DE72957284895783674747')
+    expect(bt1.reference).to be(nil)
+    expect(bt1.receipt).to eq('AI1')
+
+    bt2 = bank_account.bank_transactions.find_by_external_id("T2")
+    expect(bt2.amount).to eq(-22)
+    expect(bt2.date).to eq('2010-02-01'.to_date)
+    expect(bt2.text).to eq('CN2')
+    expect(bt2.iban).to eq('CH9300762011623852957')
+    expect(bt2.reference).to eq('RI2')
+    expect(bt2.receipt).to be(nil)
+
+    bt3 = bank_account.bank_transactions.find_by_external_id("T3")
+    expect(bt3.amount).to eq(33)
+    expect(bt3.date).to eq('2000-03-01'.to_date)
+    expect(bt3.text).to eq('DN3')
+    expect(bt3.iban).to be(nil)
+    expect(bt3.reference).to be(nil)
+    expect(bt3.receipt).to be(nil)
+  end
+end