Update seed data to include new cards, and modify hex codes for existing decks to be more different. Also add functionality to set a dark font color for card_badges if the bg color is too light

cards/signals.py

@@ -2,6 +2,36 @@ from django.db.models.signals import m2m_changed
 from django.dispatch import receiver
 from .models import Card
 
+def color_is_dark(bg_color):
+    """
+    Determine if a given hexadecimal color is dark.
+
+    This function accepts a 6-digit hex color string (with or without a leading '#').
+    It calculates the brightness using the formula:
+    
+        brightness = (0.299 * red) + (0.587 * green) + (0.114 * blue)
+    
+    A brightness value less than or equal to 186 indicates that the color is dark.
+
+    Args:
+        bg_color (str): A 6-digit hex color string (e.g. "#FFFFFF" or "FFFFFF").
+
+    Returns:
+        bool: True if the color is dark (brightness <= 186), False otherwise.
+    """
+    # Remove the leading '#' if it exists.
+    color = bg_color[1:7] if bg_color[0] == '#' else bg_color
+
+    # Convert the hex color components to integers.
+    r = int(color[0:2], 16)
+    g = int(color[2:4], 16)
+    b = int(color[4:6], 16)
+
+    # Compute brightness based on weighted RGB values.
+    brightness = (r * 0.299) + (g * 0.587) + (b * 0.114)
+    
+    return brightness <= 200
+
 @receiver(m2m_changed, sender=Card.decks.through)
 def update_card_style(sender, instance, action, **kwargs):
     if action == "post_add":
@@ -14,4 +44,6 @@ def update_card_style(sender, instance, action, **kwargs):
             instance.style = f"background: linear-gradient(to right, {', '.join(hex_colors)});"
         else:
             instance.style = "background: linear-gradient(to right, #AAAAAA, #AAAAAA, #AAAAAA);"
+        if not color_is_dark(decks.first().hex_color):
+            instance.style += "color: var(--color-gray-700);"
         instance.save(update_fields=["style"])