Fix CLI crash and add input validation

.Jules/palette.md

@@ -5,3 +5,7 @@
 ## 2024-05-23 - CLI Accessibility and Control
 **Learning:** While color and emojis enhance UX, they can be inaccessible (color blindness) or intrusive (automation logs). Providing `--no-color` and `--quiet` flags is essential for a robust CLI tool that respects user context and accessibility needs.
 **Action:** Always include flags to disable visual enhancements and suppress verbose output in CLI tools.
+
+## 2024-05-24 - CLI Error Handling
+**Learning:** Crashing with a stack trace is the worst possible UX for a CLI tool. Users expect friendly error messages when they provide invalid input.
+**Action:** Always validate CLI arguments and use `sys.exit(1)` with a clear, color-coded error message instead of letting exceptions bubble up.

bitcoin_trading_simulation.py

@@ -1,7 +1,7 @@
 import argparse
+import sys
 import numpy as np
 import pandas as pd
-import argparse
 
 
 class Colors:
@@ -109,7 +109,7 @@ def simulate_trading(signals, initial_cash=10000, quiet=False):
     return portfolio
 
 
-if __name__ == "__main__":
+def main():
     parser = argparse.ArgumentParser(description="Bitcoin Trading Simulation")
     parser.add_argument("--days", type=int, default=60, help="Number of days to simulate")
     parser.add_argument("--initial-cash", type=float, default=10000, help="Initial cash amount")
@@ -120,6 +120,23 @@ def simulate_trading(signals, initial_cash=10000, quiet=False):
 
     args = parser.parse_args()
 
+    # Input Validation
+    if args.days <= 0:
+        print(f"{Colors.RED}Error: Simulation days must be a positive integer.{Colors.ENDC}")
+        sys.exit(1)
+
+    if args.initial_cash < 0:
+        print(f"{Colors.RED}Error: Initial cash cannot be negative.{Colors.ENDC}")
+        sys.exit(1)
+
+    if args.initial_price <= 0:
+        print(f"{Colors.RED}Error: Initial Bitcoin price must be positive.{Colors.ENDC}")
+        sys.exit(1)
+
+    if args.volatility < 0:
+        print(f"{Colors.RED}Error: Volatility cannot be negative.{Colors.ENDC}")
+        sys.exit(1)
+
     if args.no_color:
         Colors.disable()
 
@@ -156,22 +173,6 @@ def simulate_trading(signals, initial_cash=10000, quiet=False):
     print(f"Buy and Hold Strategy Value: ${buy_and_hold_value:.2f}")
     print(f"{Colors.HEADER}-----------------------------------------{Colors.ENDC}")
 
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser(description='Bitcoin Trading Simulation')
-    parser.add_argument('--days', type=int, default=60, help='Number of days to simulate')
-    parser.add_argument('--initial-cash', type=float, default=10000, help='Initial cash amount')
-    parser.add_argument('--initial-price', type=float, default=50000, help='Initial Bitcoin price')
-    parser.add_argument('--volatility', type=float, default=0.02, help='Volatility factor')
-    parser.add_argument('--quiet', action='store_true', help='Suppress daily output')
-    parser.add_argument('--no-color', action='store_true', help='Disable colored output')
 
-    args = parser.parse_args()
-
-    main(
-        days=args.days,
-        initial_price=args.initial_price,
-        volatility=args.volatility,
-        initial_cash=args.initial_cash,
-        quiet=args.quiet,
-        no_color=args.no_color
-    )
+if __name__ == "__main__":
+    main()