Feature/currencies (#541)

Now each project can have a currency, default to None.
Each bill can use a different currency, and a conversion to project default currency is done on settle.

Fix #512

.gitignore

@@ -1,4 +1,3 @@
-ihatemoney.cfg
 *.pyc
 *.egg-info
 dist
@@ -13,3 +12,8 @@ build
 .pytest_cache
 ihatemoney/budget.db
 .idea/
+.envrc
+.DS_Store
+.idea
+.python-version
+

ihatemoney/currency_convertor.py

@@ -0,0 +1,46 @@
+from cachetools import TTLCache, cached
+import requests
+
+
+class Singleton(type):
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]
+
+
+class CurrencyConverter(object, metaclass=Singleton):
+    # Get exchange rates
+    default = "No Currency"
+    api_url = "https://api.exchangeratesapi.io/latest?base=USD"
+
+    def __init__(self):
+        pass
+
+    @cached(cache=TTLCache(maxsize=1, ttl=86400))
+    def get_rates(self):
+        rates = requests.get(self.api_url).json()["rates"]
+        rates[self.default] = 1.0
+        return rates
+
+    def get_currencies(self):
+        rates = [rate for rate in self.get_rates()]
+        rates.sort(key=lambda rate: "" if rate == self.default else rate)
+        return rates
+
+    def exchange_currency(self, amount, source_currency, dest_currency):
+        if (
+            source_currency == dest_currency
+            or source_currency == self.default
+            or dest_currency == self.default
+        ):
+            return amount
+
+        rates = self.get_rates()
+        source_rate = rates[source_currency]
+        dest_rate = rates[dest_currency]
+        new_amount = (float(amount) / source_rate) * dest_rate
+        # round to two digits because we are dealing with money
+        return round(new_amount, 2)

ihatemoney/forms.py

@@ -1,3 +1,4 @@
+import copy
 from datetime import datetime
 from re import match
 
@@ -8,7 +9,7 @@ from flask_wtf.file import FileAllowed, FileField, FileRequired
 from flask_wtf.form import FlaskForm
 from jinja2 import Markup
 from werkzeug.security import check_password_hash, generate_password_hash
-from wtforms.fields.core import SelectField, SelectMultipleField
+from wtforms.fields.core import Label, SelectField, SelectMultipleField
 from wtforms.fields.html5 import DateField, DecimalField, URLField
 from wtforms.fields.simple import BooleanField, PasswordField, StringField, SubmitField
 from wtforms.validators import (
@@ -20,6 +21,7 @@ from wtforms.validators import (
     ValidationError,
 )
 
+from ihatemoney.currency_convertor import CurrencyConverter
 from ihatemoney.models import LoggingMode, Person, Project
 from ihatemoney.utils import eval_arithmetic_expression, slugify
 
@@ -31,6 +33,18 @@ def strip_filter(string):
         return string
 
 
+def get_editprojectform_for(project, **kwargs):
+    """Return an instance of EditProjectForm configured for a particular project.
+    """
+    form = EditProjectForm(**kwargs)
+    choices = copy.copy(form.default_currency.choices)
+    choices.sort(
+        key=lambda rates: "" if rates[0] == project.default_currency else rates[0]
+    )
+    form.default_currency.choices = choices
+    return form
+
+
 def get_billform_for(project, set_default=True, **kwargs):
     """Return an instance of BillForm configured for a particular project.
 
@@ -39,6 +53,23 @@ def get_billform_for(project, set_default=True, **kwargs):
 
     """
     form = BillForm(**kwargs)
+    if form.original_currency.data == "None":
+        form.original_currency.data = project.default_currency
+
+    if form.original_currency.data != CurrencyConverter.default:
+        choices = copy.copy(form.original_currency.choices)
+        choices.remove((CurrencyConverter.default, CurrencyConverter.default))
+        choices.sort(
+            key=lambda rates: "" if rates[0] == project.default_currency else rates[0]
+        )
+        form.original_currency.choices = choices
+    else:
+        form.original_currency.render_kw = {"default": True}
+        form.original_currency.data = CurrencyConverter.default
+
+    form.original_currency.label = Label(
+        "original_currency", "Currency (Default: %s)" % (project.default_currency)
+    )
     active_members = [(m.id, m.name) for m in project.active_members]
 
     form.payed_for.choices = form.payer.choices = active_members
@@ -89,6 +120,15 @@ class EditProjectForm(FlaskForm):
     contact_email = StringField(_("Email"), validators=[DataRequired(), Email()])
     project_history = BooleanField(_("Enable project history"))
     ip_recording = BooleanField(_("Use IP tracking for project history"))
+    currency_helper = CurrencyConverter()
+    default_currency = SelectField(
+        _("Default Currency"),
+        choices=[
+            (currency_name, currency_name)
+            for currency_name in currency_helper.get_currencies()
+        ],
+        validators=[DataRequired()],
+    )
 
     @property
     def logging_preference(self):
@@ -112,6 +152,7 @@ class EditProjectForm(FlaskForm):
             password=generate_password_hash(self.password.data),
             contact_email=self.contact_email.data,
             logging_preference=self.logging_preference,
+            default_currency=self.default_currency.data,
         )
         return project
 
@@ -125,6 +166,7 @@ class EditProjectForm(FlaskForm):
 
         project.contact_email = self.contact_email.data
         project.logging_preference = self.logging_preference
+        project.default_currency = self.default_currency.data
 
         return project
 
@@ -199,6 +241,15 @@ class BillForm(FlaskForm):
     what = StringField(_("What?"), validators=[DataRequired()])
     payer = SelectField(_("Payer"), validators=[DataRequired()], coerce=int)
     amount = CalculatorStringField(_("Amount paid"), validators=[DataRequired()])
+    currency_helper = CurrencyConverter()
+    original_currency = SelectField(
+        _("Currency"),
+        choices=[
+            (currency_name, currency_name)
+            for currency_name in currency_helper.get_currencies()
+        ],
+        validators=[DataRequired()],
+    )
     external_link = URLField(
         _("External link"),
         validators=[Optional()],
@@ -217,6 +268,10 @@ class BillForm(FlaskForm):
         bill.external_link = self.external_link.data
         bill.date = self.date.data
         bill.owers = [Person.query.get(ower, project) for ower in self.payed_for.data]
+        bill.original_currency = self.original_currency.data
+        bill.converted_amount = self.currency_helper.exchange_currency(
+            bill.amount, bill.original_currency, project.default_currency
+        )
         return bill
 
     def fake_form(self, bill, project):
@@ -226,6 +281,10 @@ class BillForm(FlaskForm):
         bill.external_link = ""
         bill.date = self.date
         bill.owers = [Person.query.get(ower, project) for ower in self.payed_for]
+        bill.original_currency = CurrencyConverter.default
+        bill.converted_amount = self.currency_helper.exchange_currency(
+            bill.amount, bill.original_currency, project.default_currency
+        )
 
         return bill
 
@@ -234,6 +293,7 @@ class BillForm(FlaskForm):
         self.amount.data = bill.amount
         self.what.data = bill.what
         self.external_link.data = bill.external_link
+        self.original_currency.data = bill.original_currency
         self.date.data = bill.date
         self.payed_for.data = [int(ower.id) for ower in bill.owers]
 

ihatemoney/history.py

@@ -105,6 +105,14 @@ def get_history(project, human_readable_names=True):
                             if removed:
                                 changeset["owers_removed"] = (None, removed)
 
+                        # Remove converted_amount if amount changed in the same way.
+                        if (
+                            "amount" in changeset
+                            and "converted_amount" in changeset
+                            and changeset["amount"] == changeset["converted_amount"]
+                        ):
+                            del changeset["converted_amount"]
+
                     for (prop, (val_before, val_after),) in changeset.items():
                         if human_readable_names:
                             if prop == "payer_id":

ihatemoney/migrations/versions/927ed575acbd_add_currencies.py

@@ -0,0 +1,73 @@
+"""Add currencies
+
+Revision ID: 927ed575acbd
+Revises: cb038f79982e
+Create Date: 2020-04-25 14:49:41.136602
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = "927ed575acbd"
+down_revision = "cb038f79982e"
+
+from alembic import op
+import sqlalchemy as sa
+from ihatemoney.currency_convertor import CurrencyConverter
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column("bill", sa.Column("converted_amount", sa.Float(), nullable=True))
+    op.add_column(
+        "bill",
+        sa.Column(
+            "original_currency",
+            sa.String(length=3),
+            server_default=CurrencyConverter.default,
+            nullable=True,
+        ),
+    )
+    op.add_column(
+        "bill_version",
+        sa.Column("converted_amount", sa.Float(), autoincrement=False, nullable=True),
+    )
+    op.add_column(
+        "bill_version",
+        sa.Column(
+            "original_currency", sa.String(length=3), autoincrement=False, nullable=True
+        ),
+    )
+    op.add_column(
+        "project",
+        sa.Column(
+            "default_currency",
+            sa.String(length=3),
+            server_default=CurrencyConverter.default,
+            nullable=True,
+        ),
+    )
+    op.add_column(
+        "project_version",
+        sa.Column(
+            "default_currency", sa.String(length=3), autoincrement=False, nullable=True
+        ),
+    )
+    # ### end Alembic commands ###
+    op.execute(
+        """
+    UPDATE bill
+    SET converted_amount = amount
+    WHERE converted_amount IS NULL
+    """
+    )
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column("project_version", "default_currency")
+    op.drop_column("project", "default_currency")
+    op.drop_column("bill_version", "original_currency")
+    op.drop_column("bill_version", "converted_amount")
+    op.drop_column("bill", "original_currency")
+    op.drop_column("bill", "converted_amount")
+    # ### end Alembic commands ###

ihatemoney/models.py

@@ -71,6 +71,7 @@ class Project(db.Model):
     members = db.relationship("Person", backref="project")
 
     query_class = ProjectQuery
+    default_currency = db.Column(db.String(3))
 
     @property
     def _to_serialize(self):
@@ -80,6 +81,7 @@ class Project(db.Model):
             "contact_email": self.contact_email,
             "logging_preference": self.logging_preference.value,
             "members": [],
+            "default_currency": self.default_currency,
         }
 
         balance = self.balance
@@ -128,7 +130,10 @@ class Project(db.Model):
             {
                 "member": member,
                 "paid": sum(
-                    [bill.amount for bill in self.get_member_bills(member.id).all()]
+                    [
+                        bill.converted_amount
+                        for bill in self.get_member_bills(member.id).all()
+                    ]
                 ),
                 "spent": sum(
                     [
@@ -151,7 +156,7 @@ class Project(db.Model):
         """
         monthly = defaultdict(lambda: defaultdict(float))
         for bill in self.get_bills().all():
-            monthly[bill.date.year][bill.date.month] += bill.amount
+            monthly[bill.date.year][bill.date.month] += bill.converted_amount
         return monthly
 
     @property
@@ -432,6 +437,9 @@ class Bill(db.Model):
     what = db.Column(db.UnicodeText)
     external_link = db.Column(db.UnicodeText)
 
+    original_currency = db.Column(db.String(3))
+    converted_amount = db.Column(db.Float)
+
     archive = db.Column(db.Integer, db.ForeignKey("archive.id"))
 
     @property
@@ -445,9 +453,11 @@ class Bill(db.Model):
             "creation_date": self.creation_date,
             "what": self.what,
             "external_link": self.external_link,
+            "original_currency": self.original_currency,
+            "converted_amount": self.converted_amount,
         }
 
-    def pay_each(self):
+    def pay_each_default(self, amount):
         """Compute what each share has to pay"""
         if self.owers:
             weights = (
@@ -455,13 +465,16 @@ class Bill(db.Model):
                 .join(billowers, Bill)
                 .filter(Bill.id == self.id)
             ).scalar()
-            return self.amount / weights
+            return amount / weights
         else:
             return 0
 
     def __str__(self):
         return self.what
 
+    def pay_each(self):
+        return self.pay_each_default(self.converted_amount)
+
     def __repr__(self):
         return (
             f"<Bill of {self.amount} from {self.payer} for "

ihatemoney/run.py

@@ -10,6 +10,7 @@ from werkzeug.middleware.proxy_fix import ProxyFix
 
 from ihatemoney import default_settings
 from ihatemoney.api.v1 import api as apiv1
+from ihatemoney.currency_convertor import CurrencyConverter
 from ihatemoney.models import db
 from ihatemoney.utils import (
     IhmJSONEncoder,
@@ -137,6 +138,9 @@ def create_app(
     # Configure the a, root="main"pplication
     setup_database(app)
 
+    # Setup Currency Cache
+    CurrencyConverter()
+
     mail = Mail()
     mail.init_app(app)
     app.mail = mail

ihatemoney/templates/forms.html

@@ -75,6 +75,7 @@
     {{ input(form.name) }}
     {{ input(form.password) }}
     {{ input(form.contact_email) }}
+    {{ input(form.default_currency) }}
     {% if not home %}
     {{ submit(form.submit, home=True) }}
     {% endif %}
@@ -96,6 +97,7 @@
         </div>
     </div>
 
+    {{ input(form.default_currency) }}
     <div class="actions">
         <button class="btn btn-primary">{{ _("Edit the project") }}</button>
         <a id="delete-project" style="color:red; margin-left:10px; cursor:pointer; ">{{ _("delete") }}</a>
@@ -122,6 +124,9 @@
     {{ input(form.what, inline=True) }}
     {{ input(form.payer, inline=True, class="form-control custom-select") }}
     {{ input(form.amount, inline=True) }}
+    {% if not form.original_currency.render_kw %}
+        {{ input(form.original_currency, inline=True) }}
+    {% endif %}
     {{ input(form.external_link, inline=True) }}
 
     <div class="form-group row">

ihatemoney/templates/history.html

@@ -225,6 +225,10 @@
                         {{ simple_property_change(event, _("Amount")) }}
                     {% elif event.prop_changed == "date" %}
                         {{ simple_property_change(event, _("Date")) }}
+                    {% elif event.prop_changed == "original_currency" %}
+                        {{ simple_property_change(event, _("Currency")) }}
+                    {% elif event.prop_changed == "converted_amount" %}
+                        {{ simple_property_change(event, _("Amount in %(currency)s", currency=g.project.default_currency)) }}
                     {% else %}
                        {{ describe_object(event) }} {{ _("modified") }}
                     {% endif %}

ihatemoney/templates/list_bills.html

@@ -111,7 +111,19 @@
         <div class="clearfix"></div>
 
         <table id="bill_table" class="col table table-striped table-hover table-responsive-sm">
-            <thead><tr><th>{{ _("When?") }}</th><th>{{ _("Who paid?") }}</<th><th>{{ _("For what?") }}</th><th>{{ _("For whom?") }}</th><th>{{ _("How much?") }}</th><th>{{ _("Actions") }}</th></tr></thead>
+            <thead>
+                <tr><th>{{ _("When?") }}
+                </th><th>{{ _("Who paid?") }}   
+                </th><th>{{ _("For what?") }}
+                </th><th>{{ _("For whom?") }}
+                </th><th>{{ _("How much?") }}
+                {% if g.project.default_currency != "No Currency" %}
+                  </th><th>{{ _("Amount in %(currency)s", currency=g.project.default_currency) }}
+                {%- else -%}
+                  </th><th>{{ _("Amount") }}
+                {% endif %}
+                </th><th>{{ _("Actions") }}</th></tr>
+            </thead>
         <tbody>
         {% for bill in bills.items %}
         <tr owers="{{bill.owers|join(',','id')}}" payer="{{bill.payer.id}}">
@@ -130,7 +142,14 @@
                 {%- else -%}
                 {{ bill.owers|join(', ', 'name') }}
                 {%- endif %}</td>
-                <td>{{ "%0.2f"|format(bill.amount) }} ({{ "%0.2f"|format(bill.pay_each()) }} {{ _("each") }})</td>
+                <td>
+                    {% if bill.original_currency != "No Currency" %}
+                        {{ "%0.2f"|format(bill.amount) }} {{bill.original_currency}} ({{ "%0.2f"|format(bill.pay_each_default(bill.amount)) }} {{bill.original_currency}} {{ _(" each") }})
+                    {%- else -%}
+                        {{ "%0.2f"|format(bill.amount) }} ({{ "%0.2f"|format(bill.pay_each_default(bill.amount)) }} {{ _(" each") }})
+                    {% endif %}
+                </td>
+                <td>{{ "%0.2f"|format(bill.converted_amount) }}</td>
                 <td class="bill-actions">
                     <a class="edit" href="{{ url_for(".edit_bill", bill_id=bill.id) }}" title="{{ _("edit") }}">{{ _('edit') }}</a>
                     <a class="delete" href="{{ url_for(".delete_bill", bill_id=bill.id) }}" title="{{ _("delete") }}">{{ _('delete') }}</a>

ihatemoney/tests/tests.py

@@ -6,7 +6,7 @@ import json
 import os
 from time import sleep
 import unittest
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 from flask import session
 from flask_testing import TestCase
@@ -14,6 +14,7 @@ from sqlalchemy import orm
 from werkzeug.security import check_password_hash, generate_password_hash
 
 from ihatemoney import history, models, utils
+from ihatemoney.currency_convertor import CurrencyConverter
 from ihatemoney.manage import DeleteProject, GenerateConfig, GeneratePasswordHash
 from ihatemoney.run import create_app, db, load_configuration
 from ihatemoney.versioning import LoggingMode
@@ -59,6 +60,7 @@ class BaseTestCase(TestCase):
                 "id": name,
                 "password": name,
                 "contact_email": f"{name}@notmyidea.org",
+                "default_currency": "USD",
             },
         )
 
@@ -68,6 +70,7 @@ class BaseTestCase(TestCase):
             name=str(name),
             password=generate_password_hash(name),
             contact_email=f"{name}@notmyidea.org",
+            default_currency="USD",
         )
         models.db.session.add(project)
         models.db.session.commit()
@@ -254,6 +257,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                     "id": "raclette",
                     "password": "party",
                     "contact_email": "raclette@notmyidea.org",
+                    "default_currency": "USD",
                 },
             )
 
@@ -273,6 +277,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                     "id": "raclette",  # already used !
                     "password": "party",
                     "contact_email": "raclette@notmyidea.org",
+                    "default_currency": "USD",
                 },
             )
 
@@ -290,6 +295,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                     "id": "raclette",
                     "password": "party",
                     "contact_email": "raclette@notmyidea.org",
+                    "default_currency": "USD",
                 },
             )
 
@@ -310,6 +316,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                     "id": "raclette",
                     "password": "party",
                     "contact_email": "raclette@notmyidea.org",
+                    "default_currency": "USD",
                 },
             )
 
@@ -329,6 +336,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                     "id": "raclette",
                     "password": "party",
                     "contact_email": "raclette@notmyidea.org",
+                    "default_currency": "USD",
                 },
             )
 
@@ -841,6 +849,7 @@ class BudgetTestCase(IhatemoneyTestCase):
             "contact_email": "alexis@notmyidea.org",
             "password": "didoudida",
             "logging_preference": LoggingMode.ENABLED.value,
+            "default_currency": "USD",
         }
 
         resp = self.client.post("/raclette/edit", data=new_data, follow_redirects=True)
@@ -849,6 +858,7 @@ class BudgetTestCase(IhatemoneyTestCase):
 
         self.assertEqual(project.name, new_data["name"])
         self.assertEqual(project.contact_email, new_data["contact_email"])
+        self.assertEqual(project.default_currency, new_data["default_currency"])
         self.assertTrue(check_password_hash(project.password, new_data["password"]))
 
         # Editing a project with a wrong email address should fail
@@ -1099,6 +1109,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                 "payer": 1,
                 "payed_for": [1, 2, 3, 4],
                 "amount": "10.0",
+                "original_currency": "USD",
             },
         )
 
@@ -1110,6 +1121,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                 "payer": 2,
                 "payed_for": [1, 3],
                 "amount": "200",
+                "original_currency": "USD",
             },
         )
 
@@ -1121,6 +1133,7 @@ class BudgetTestCase(IhatemoneyTestCase):
                 "payer": 3,
                 "payed_for": [2],
                 "amount": "13.33",
+                "original_currency": "USD",
             },
         )
 
@@ -1425,6 +1438,7 @@ class APITestCase(IhatemoneyTestCase):
                 "id": id,
                 "password": password,
                 "contact_email": contact,
+                "default_currency": "USD",
             },
         )
 
@@ -1486,6 +1500,7 @@ class APITestCase(IhatemoneyTestCase):
                 "id": "raclette",
                 "password": "raclette",
                 "contact_email": "not-an-email",
+                "default_currency": "USD",
             },
         )
 
@@ -1514,6 +1529,7 @@ class APITestCase(IhatemoneyTestCase):
             "members": [],
             "name": "raclette",
             "contact_email": "raclette@notmyidea.org",
+            "default_currency": "USD",
             "id": "raclette",
             "logging_preference": 1,
         }
@@ -1525,6 +1541,7 @@ class APITestCase(IhatemoneyTestCase):
             "/api/projects/raclette",
             data={
                 "contact_email": "yeah@notmyidea.org",
+                "default_currency": "USD",
                 "password": "raclette",
                 "name": "The raclette party",
                 "project_history": "y",
@@ -1542,6 +1559,7 @@ class APITestCase(IhatemoneyTestCase):
         expected = {
             "name": "The raclette party",
             "contact_email": "yeah@notmyidea.org",
+            "default_currency": "USD",
             "members": [],
             "id": "raclette",
             "logging_preference": 1,
@@ -1554,6 +1572,7 @@ class APITestCase(IhatemoneyTestCase):
             "/api/projects/raclette",
             data={
                 "contact_email": "yeah@notmyidea.org",
+                "default_currency": "USD",
                 "password": "tartiflette",
                 "name": "The raclette party",
             },
@@ -1776,6 +1795,8 @@ class APITestCase(IhatemoneyTestCase):
             "amount": 25.0,
             "date": "2011-08-10",
             "id": 1,
+            "converted_amount": 25.0,
+            "original_currency": "USD",
             "external_link": "https://raclette.fr",
         }
 
@@ -1845,6 +1866,8 @@ class APITestCase(IhatemoneyTestCase):
             "amount": 25.0,
             "date": "2011-09-10",
             "external_link": "https://raclette.fr",
+            "converted_amount": 25.0,
+            "original_currency": "USD",
             "id": 1,
         }
 
@@ -1922,6 +1945,8 @@ class APITestCase(IhatemoneyTestCase):
                 "date": "2011-08-10",
                 "id": id,
                 "external_link": "",
+                "original_currency": "USD",
+                "converted_amount": expected_amount,
             }
 
             got = json.loads(req.data.decode("utf-8"))
@@ -2064,6 +2089,8 @@ class APITestCase(IhatemoneyTestCase):
             "date": "2011-08-10",
             "id": 1,
             "external_link": "",
+            "converted_amount": 25.0,
+            "original_currency": "USD",
         }
         got = json.loads(req.data.decode("utf-8"))
         self.assertEqual(
@@ -2106,6 +2133,7 @@ class APITestCase(IhatemoneyTestCase):
             "id": "raclette",
             "name": "raclette",
             "logging_preference": 1,
+            "default_currency": "USD",
         }
 
         self.assertStatus(200, req)
@@ -2273,6 +2301,7 @@ class HistoryTestCase(IhatemoneyTestCase):
             "name": "demo",
             "contact_email": "demo@notmyidea.org",
             "password": "demo",
+            "default_currency": "USD",
         }
 
         if logging_preference != LoggingMode.DISABLED:
@@ -2327,6 +2356,7 @@ class HistoryTestCase(IhatemoneyTestCase):
             "contact_email": "demo2@notmyidea.org",
             "password": "123456",
             "project_history": "y",
+            "default_currency": "USD",
         }
 
         resp = self.client.post("/demo/edit", data=new_data, follow_redirects=True)
@@ -2422,6 +2452,7 @@ class HistoryTestCase(IhatemoneyTestCase):
             "name": "demo2",
             "contact_email": "demo2@notmyidea.org",
             "password": "123456",
+            "default_currency": "USD",
         }
 
         # Keep privacy settings where they were
@@ -2850,5 +2881,23 @@ class HistoryTestCase(IhatemoneyTestCase):
         self.assertEqual(len(history_list), 6)
 
 
+class TestCurrencyConverter(unittest.TestCase):
+    converter = CurrencyConverter()
+    mock_data = {"USD": 1, "EUR": 0.8115}
+    converter.get_rates = MagicMock(return_value=mock_data)
+
+    def test_only_one_instance(self):
+        one = id(CurrencyConverter())
+        two = id(CurrencyConverter())
+        self.assertEqual(one, two)
+
+    def test_get_currencies(self):
+        self.assertCountEqual(self.converter.get_currencies(), ["USD", "EUR"])
+
+    def test_exchange_currency(self):
+        result = self.converter.exchange_currency(100, "USD", "EUR")
+        self.assertEqual(result, 81.15)
+
+
 if __name__ == "__main__":
     unittest.main()

ihatemoney/web.py

@@ -37,10 +37,10 @@ from sqlalchemy_continuum import Operation
 from werkzeug.exceptions import NotFound
 from werkzeug.security import check_password_hash, generate_password_hash
 
+from ihatemoney.currency_convertor import CurrencyConverter
 from ihatemoney.forms import (
     AdminAuthenticationForm,
     AuthenticationForm,
-    EditProjectForm,
     InviteForm,
     MemberForm,
     PasswordReminder,
@@ -48,6 +48,7 @@ from ihatemoney.forms import (
     ResetPasswordForm,
     UploadForm,
     get_billform_for,
+    get_editprojectform_for,
 )
 from ihatemoney.history import get_history, get_history_queries
 from ihatemoney.models import Bill, LoggingMode, Person, Project, db
@@ -376,7 +377,7 @@ def reset_password():
 
 @main.route("/<project_id>/edit", methods=["GET", "POST"])
 def edit_project():
-    edit_form = EditProjectForm()
+    edit_form = get_editprojectform_for(g.project)
     import_form = UploadForm()
     # Import form
     if import_form.validate_on_submit():
@@ -391,6 +392,18 @@ def edit_project():
     # Edit form
     if edit_form.validate_on_submit():
         project = edit_form.update(g.project)
+        # Update converted currency
+        if project.default_currency != CurrencyConverter.default:
+            for bill in project.get_bills():
+
+                if bill.original_currency == CurrencyConverter.default:
+                    bill.original_currency = project.default_currency
+
+                bill.converted_amount = CurrencyConverter().exchange_currency(
+                    bill.amount, bill.original_currency, project.default_currency
+                )
+                db.session.add(bill)
+
         db.session.add(project)
         db.session.commit()
 
@@ -478,6 +491,7 @@ def import_project(file, project):
         form.date = parse(b["date"])
         form.payer = id_dict[b["payer_name"]]
         form.payed_for = owers_id
+        form.original_currency = b.get("original_currency")
 
         db.session.add(form.fake_form(bill, project))
 
@@ -543,6 +557,7 @@ def demo():
             name="demonstration",
             password=generate_password_hash("demo"),
             contact_email="demo@notmyidea.org",
+            default_currency="EUR",
         )
         db.session.add(project)
         db.session.commit()

setup.cfg

@@ -23,6 +23,7 @@ include_package_data = True
 zip_safe = False
 install_requires =
     blinker==1.4
+    cachetools==4.1.0
     debts==0.5
     email_validator==1.0.5
     Flask-Babel==1.0.0
@@ -37,6 +38,7 @@ install_requires =
     Flask==1.1.2
     itsdangerous==1.1.0
     Jinja2==2.11.2
+    requests==2.22.0
     SQLAlchemy-Continuum==1.3.9
 
 [options.extras_require]