Update price monitor settings

pricemon/admin.py

@@ -4,7 +4,15 @@ from pricemon.models import PriceAlert, PriceSnapshot, PriceWatcher
 
 @admin.register(PriceWatcher)
 class PriceWatcherAdmin(admin.ModelAdmin):
-    list_display = ['name', 'url', 'last_price', 'last_checked_at', 'enabled', 'check_interval_hours']
+    list_display = [
+        'name',
+        'url',
+        'initial_price',
+        'last_price',
+        'last_checked_at',
+        'enabled',
+        'check_interval_hours',
+    ]
     list_filter = ['enabled', 'check_interval_hours']
     search_fields = ['name', 'url']
 

pricemon/migrations/0005_pricewatcher_initial_price.py

@@ -0,0 +1,41 @@
+from django.db import migrations, models
+
+
+def backfill_initial_price(apps, schema_editor):
+    PriceWatcher = apps.get_model('pricemon', 'PriceWatcher')
+    PriceSnapshot = apps.get_model('pricemon', 'PriceSnapshot')
+
+    for watcher in PriceWatcher.objects.all():
+        if watcher.initial_price is not None:
+            continue
+
+        snapshot = (
+            PriceSnapshot.objects.filter(watcher_id=watcher.pk, price__isnull=False)
+            .order_by('checked_at', 'pk')
+            .first()
+        )
+        if snapshot is None:
+            continue
+
+        watcher.initial_price = snapshot.price
+        watcher.save(update_fields=['initial_price'])
+
+
+def noop_reverse(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pricemon', '0004_alert_price_threshold_recurring'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='pricewatcher',
+            name='initial_price',
+            field=models.DecimalField(blank=True, decimal_places=2, max_digits=12, null=True),
+        ),
+        migrations.RunPython(backfill_initial_price, noop_reverse),
+    ]

pricemon/models.py

@@ -1,3 +1,5 @@
+from decimal import Decimal, ROUND_HALF_UP
+
 from django.db import models
 
 
@@ -19,15 +21,22 @@ class PriceWatcher(models.Model):
     )
     check_interval_hours = models.IntegerField(choices=INTERVAL_CHOICES, default=24)
     alert_price_threshold = models.DecimalField(
-        max_digits=12, decimal_places=2, null=True, blank=True,
+        max_digits=12,
+        decimal_places=2,
+        null=True,
+        blank=True,
         help_text='Send an alert when the detected price is at or below this value. Leave blank to disable alerts.',
     )
     recurring_notification = models.BooleanField(
         default=True,
-        help_text='Keep notifying on every check while the price meets the threshold. Disable to notify only once (until you dismiss the alert).',
+        help_text=(
+            'Keep notifying on every check while the price meets the threshold. '
+            'Disable to notify only once (until you dismiss the alert).'
+        ),
     )
     enabled = models.BooleanField(default=True)
     last_checked_at = models.DateTimeField(null=True, blank=True)
+    initial_price = models.DecimalField(max_digits=12, decimal_places=2, null=True, blank=True)
     last_price = models.DecimalField(max_digits=12, decimal_places=2, null=True, blank=True)
     created_at = models.DateTimeField(auto_now_add=True)
 
@@ -37,6 +46,34 @@ class PriceWatcher(models.Model):
     def __str__(self):
         return self.name
 
+    @property
+    def price_change_direction(self):
+        if self.initial_price is None or self.last_price is None:
+            return None
+        if self.last_price > self.initial_price:
+            return 'up'
+        if self.last_price < self.initial_price:
+            return 'down'
+        return 'flat'
+
+    @property
+    def price_change_pct(self):
+        if self.initial_price is None or self.last_price is None or self.initial_price == 0:
+            return None
+        pct = ((self.last_price - self.initial_price) / self.initial_price) * Decimal('100')
+        return abs(pct).quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
+
+    @property
+    def price_change_symbol(self):
+        direction = self.price_change_direction
+        if direction == 'up':
+            return '↑'
+        if direction == 'down':
+            return '↓'
+        if direction == 'flat':
+            return '→'
+        return ''
+
 
 class PriceSnapshot(models.Model):
     watcher = models.ForeignKey(PriceWatcher, on_delete=models.CASCADE, related_name='snapshots')

pricemon/tasks.py

@@ -53,6 +53,9 @@ def check_watcher(watcher_pk: int) -> None:
 
     update_fields = ['last_checked_at']
     if price is not None:
+        if watcher.initial_price is None:
+            watcher.initial_price = price
+            update_fields.append('initial_price')
         watcher.last_price = price
         update_fields.append('last_price')
     watcher.last_checked_at = now()

templates/pricemon/dashboard.html

@@ -92,6 +92,29 @@
             {% else %}
               <span class="text-gray-400 text-lg">—</span>
             {% endif %}
+            <div class="mt-1 text-xs text-gray-500">
+              {% if watcher.initial_price %}
+                <span class="block">{% trans "Initial" %} ${{ watcher.initial_price }}</span>
+              {% endif %}
+              {% if watcher.price_change_direction %}
+                {% if watcher.price_change_direction == 'up' %}
+                  <span class="block text-red-600">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    {% trans "up" %} {{ watcher.price_change_pct }}%
+                  </span>
+                {% elif watcher.price_change_direction == 'down' %}
+                  <span class="block text-green-600">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    {% trans "down" %} {{ watcher.price_change_pct }}%
+                  </span>
+                {% else %}
+                  <span class="block text-gray-500">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    0.00%
+                  </span>
+                {% endif %}
+              {% endif %}
+            </div>
           </div>
         </div>
         <!-- Actions row -->
@@ -168,6 +191,29 @@
             {% else %}
               <span class="text-gray-400">—</span>
             {% endif %}
+            <div class="mt-1 space-y-0.5 text-xs text-gray-500">
+              {% if watcher.initial_price %}
+                <div>{% trans "Initial" %} ${{ watcher.initial_price }}</div>
+              {% endif %}
+              {% if watcher.price_change_direction %}
+                {% if watcher.price_change_direction == 'up' %}
+                  <div class="font-medium text-red-600">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    {% trans "up" %} {{ watcher.price_change_pct }}%
+                  </div>
+                {% elif watcher.price_change_direction == 'down' %}
+                  <div class="font-medium text-green-600">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    {% trans "down" %} {{ watcher.price_change_pct }}%
+                  </div>
+                {% else %}
+                  <div class="font-medium text-gray-500">
+                    <span aria-hidden="true">{{ watcher.price_change_symbol }}</span>
+                    0.00%
+                  </div>
+                {% endif %}
+              {% endif %}
+            </div>
           </td>
           <td class="px-4 py-3 text-gray-500">
             {% if watcher.last_checked_at %}