Create a currency model

InvenTree/InvenTree/settings.py

@@ -83,6 +83,7 @@ INSTALLED_APPS = [
     'django.contrib.staticfiles',
 
     # InvenTree apps
+    'common.apps.CommonConfig',
     'part.apps.PartConfig',
     'stock.apps.StockConfig',
     'company.apps.CompanyConfig',

InvenTree/common/admin.py

@@ -1,3 +1,10 @@
 from django.contrib import admin
 
-# Register your models here.
+from .models import Currency
+
+
+class CurrencyAdmin(admin.ModelAdmin):
+    list_display = ('symbol', 'suffix', 'description', 'value', 'base')
+
+
+admin.site.register(Currency, CurrencyAdmin)

InvenTree/common/migrations/0001_initial.py

@@ -0,0 +1,26 @@
+# Generated by Django 2.2.4 on 2019-09-02 23:02
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Currency',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('symbol', models.CharField(help_text='Currency Symbol e.g. $', max_length=10)),
+                ('suffix', models.CharField(help_text='Currency Suffix e.g. AUD', max_length=10, unique=True)),
+                ('description', models.CharField(help_text='Currency Description', max_length=100)),
+                ('value', models.DecimalField(decimal_places=5, help_text='Currency Value', max_digits=10, validators=[django.core.validators.MinValueValidator(1e-05), django.core.validators.MaxValueValidator(100000)])),
+                ('base', models.BooleanField(default=False, help_text='Use this currency as the base currency')),
+            ],
+        ),
+    ]

InvenTree/common/migrations/0002_auto_20190902_2304.py

@@ -0,0 +1,17 @@
+# Generated by Django 2.2.4 on 2019-09-02 23:04
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('common', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='currency',
+            options={'verbose_name_plural': 'Currencies'},
+        ),
+    ]

InvenTree/common/models.py

@@ -1,3 +1,79 @@
-from django.db import models
+"""
+Common database model definitions.
+These models are 'generic' and do not fit a particular business logic object.
+"""
 
-# Create your models here.
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models
+from django.utils.translation import ugettext as _
+from django.core.validators import MinValueValidator, MaxValueValidator
+
+
+class Currency(models.Model):
+    """
+    A Currency object represents a particular unit of currency.
+    Each Currency has a scaling factor which relates it to the base currency.
+    There must be one (and only one) currency which is selected as the base currency,
+    and each other currency is calculated relative to it.
+
+    Attributes:
+        symbol: Currency symbol e.g. $
+        suffix: Currency suffix e.g. AUD
+        description: Long-form description e.g. "Australian Dollars"
+        value: The value of this currency compared to the base currency.
+        base: True if this currency is the base currency
+
+    """
+
+    symbol = models.CharField(max_length=10, blank=False, unique=False, help_text=_('Currency Symbol e.g. $'))
+
+    suffix = models.CharField(max_length=10, blank=False, unique=True, help_text=_('Currency Suffix e.g. AUD'))
+
+    description = models.CharField(max_length=100, blank=False, help_text=_('Currency Description'))
+
+    value = models.DecimalField(max_digits=10, decimal_places=5, validators=[MinValueValidator(0.00001), MaxValueValidator(100000)], help_text=_('Currency Value'))
+
+    base = models.BooleanField(default=False, help_text=_('Use this currency as the base currency'))
+
+    class Meta:
+        verbose_name_plural = 'Currencies'
+
+    def __str__(self):
+        """ Format string for currency representation """
+        s = "{sym} {suf} - {desc}".format(
+            sym=self.symbol,
+            suf=self.suffix,
+            desc=self.description
+        )
+
+        if self.base:
+            s += " (Base)"
+        
+        else:
+            s += " = {v}".format(v=self.value)
+
+        return s
+
+    def save(self, *args, **kwargs):
+        """ Validate the model before saving
+
+        - Ensure that there is only one base currency!
+        """
+
+        # If this currency is set as the base currency, ensure no others are
+        if self.base:
+            for cur in Currency.objects.filter(base=True).exclude(pk=self.pk):
+                cur.base = False
+                cur.save()
+
+        # If there are no currencies set as the base currency, set this as base
+        if not Currency.objects.filter(base=True).exists():
+            self.base = True
+
+        # If this is the base currency, ensure value is set to unity
+        if self.base:
+            self.value = 1.0
+
+        super().save(*args, **kwargs)

Makefile

@@ -9,6 +9,7 @@ clean:
 
 # Perform database migrations (after schema changes are made)
 migrate:
+	python3 InvenTree/manage.py makemigrations common
 	python3 InvenTree/manage.py makemigrations company
 	python3 InvenTree/manage.py makemigrations part
 	python3 InvenTree/manage.py makemigrations stock
@@ -40,12 +41,12 @@ style:
 # Run unit tests
 test:
 	python3 InvenTree/manage.py check
-	python3 InvenTree/manage.py test build company part stock order
+	python3 InvenTree/manage.py test build common company order part stock 
 
 # Run code coverage
 coverage:
 	python3 InvenTree/manage.py check
-	coverage run InvenTree/manage.py test build company part stock order InvenTree
+	coverage run InvenTree/manage.py test build common company order part stock  InvenTree
 	coverage html
 
 # Install packages required to generate code docs