Custom migration for PartSellPriceBreak

InvenTree/part/migrations/0055_auto_20201110_1001.py

@@ -0,0 +1,24 @@
+# Generated by Django 3.0.7 on 2020-11-10 10:01
+
+from django.db import migrations
+import djmoney.models.fields
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0054_auto_20201109_1246'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='partsellpricebreak',
+            name='price',
+            field=djmoney.models.fields.MoneyField(decimal_places=4, default_currency='USD', help_text='Unit price at specified quantity', max_digits=19, null=True, verbose_name='Price'),
+        ),
+        migrations.AddField(
+            model_name='partsellpricebreak',
+            name='price_currency',
+            field=djmoney.models.fields.CurrencyField(choices=[('AUD', 'Australian Dollar'), ('CAD', 'Canadian Dollar'), ('EUR', 'Euro'), ('NZD', 'New Zealand Dollar'), ('GBP', 'Pound Sterling'), ('USD', 'US Dollar'), ('JPY', 'Yen')], default='USD', editable=False, max_length=3),
+        ),
+    ]

InvenTree/part/migrations/0056_auto_20201110_1125.py

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+# Generated by Django 3.0.7 on 2020-11-10 11:25
+
+from django.db import migrations
+
+from moneyed import CURRENCIES
+from django.db import migrations, connection
+from company.models import SupplierPriceBreak
+
+
+def migrate_currencies(apps, schema_editor):
+    """
+    Migrate from the 'old' method of handling currencies,
+    to the new method which uses the django-money library.
+
+    Previously, we created a custom Currency model,
+    which was very simplistic.
+
+    Here we will attempt to map each existing "currency" reference
+    for the SupplierPriceBreak model, to a new django-money compatible currency.
+    """
+
+    print("Updating currency references for SupplierPriceBreak model...")
+
+    # A list of available currency codes
+    currency_codes = CURRENCIES.keys()
+
+    cursor = connection.cursor()
+
+    # The 'suffix' field denotes the currency code
+    response = cursor.execute('SELECT id, suffix, description from common_currency;').fetchall()
+
+    remap = {}
+
+    for index, row in enumerate(response):
+        pk, suffix, description = row
+
+        suffix = suffix.strip().upper()
+
+        if suffix not in currency_codes:
+            print("Missing suffix:", suffix)
+
+            while suffix not in currency_codes:
+                # Ask the user to input a valid currency
+                print(f"Could not find a valid currency matching '{suffix}'.")
+                print("Please enter a valid currency code")
+                suffix = str(input("> ")).strip()
+
+        if pk not in remap.keys():
+            remap[pk] = suffix
+
+    # Now iterate through each PartSellPriceBreak and update the rows
+    response = cursor.execute('SELECT id, cost, currency_id, price, price_currency from part_partsellpricebreak;').fetchall()
+
+    count = 0
+
+    for index, row in enumerate(response):
+        pk, cost, currency_id, price, price_currency = row
+
+        # Copy the 'cost' field across to the 'price' field
+        response = cursor.execute(f'UPDATE part_partsellpricebreak set price={cost} where id={pk};')
+
+        # Extract the updated currency code
+        currency_code = remap.get(currency_id, 'USD')
+
+        # Update the currency code
+        response = cursor.execute(f'UPDATE part_partsellpricebreak set price_currency= "{currency_code}" where id={pk};')
+
+        count += 1
+
+    print(f"Updated {count} SupplierPriceBreak rows")
+
+def reverse_currencies(apps, schema_editor):
+    """
+    Reverse the "update" process.
+
+    Here we may be in the situation that the legacy "Currency" table is empty,
+    and so we have to re-populate it based on the new price_currency codes.
+    """
+
+    print("Reversing currency migration...")
+
+    cursor = connection.cursor()
+
+    # Extract a list of currency codes which are in use
+    response = cursor.execute(f'SELECT id, price, price_currency from part_partsellpricebreak;').fetchall()
+
+    codes_in_use = set()
+
+    for index, row in enumerate(response):
+        pk, price, code = row
+
+        codes_in_use.add(code)
+
+        # Copy the 'price' field back into the 'cost' field
+        response = cursor.execute(f'UPDATE part_partsellpricebreak set cost={price} where id={pk};')
+
+    # Keep a dict of which currency objects map to which code
+    code_map = {}
+
+    # For each currency code in use, check if we have a matching Currency object
+    for code in codes_in_use:
+        response = cursor.execute(f'SELECT id, suffix from common_currency where suffix="{code}";')
+        row = response.fetchone()
+
+        if row is not None:
+            # A match exists!
+            pk, suffix = row
+            code_map[suffix] = pk
+        else:
+            # No currency object exists!
+            description = CURRENCIES[code]
+
+            # Create a new object in the database
+            print(f"Creating new Currency object for {code}")
+        
+            # Construct a query to create a new Currency object
+            query = f'INSERT into common_currency (symbol, suffix, description, value, base) VALUES ("$", "{code}", "{description}", 1.0, False);'
+
+            response = cursor.execute(query)
+
+            code_map[code] = cursor.lastrowid
+
+    # Ok, now we know how each suffix maps to a Currency object
+    for suffix in code_map.keys():
+        pk = code_map[suffix]
+
+        # Update the table to point to the Currency objects
+        print(f"Currency {suffix} -> pk {pk}")
+
+        response = cursor.execute(f'UPDATE part_partsellpricebreak set currency_id={pk} where price_currency="{suffix}";')
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0055_auto_20201110_1001'),
+    ]
+
+    operations = [
+        migrations.RunPython(migrate_currencies, reverse_code=reverse_currencies),
+    ]