# Full validation (all four principles)
/sc:principles src/

# KISS only validation
/sc:principles src/ --kiss-only

# Purity only validation
/sc:principles src/ --purity-only

# SOLID only validation
/sc:principles src/ --solid-only

# Let It Crash only validation
/sc:principles src/ --crash-only

# Strict mode (warnings become errors)
/sc:principles src/ --strict

# Generate detailed report
/sc:principles src/ --report

1. INITIALIZE
   ├── Detect scope root
   ├── Find changed Python files (git diff)
   └── Determine file contexts (core vs shell)

2. ANALYZE
   ├── Parse AST for each file
   ├── Calculate complexity metrics (KISS)
   ├── Detect I/O patterns (Purity)
   ├── Check structural patterns (SOLID)
   └── Analyze error handling (Let It Crash)

3. VALIDATE
   ├── Compare against thresholds
   ├── Classify violations (error vs warning)
   └── Apply context rules (core stricter than shell)

4. REPORT/BLOCK
   ├── Output violations with locations
   ├── Generate actionable recommendations
   └── Exit 0 (pass) or 2 (blocked)

python .claude/skills/sc-principles/scripts/validate_kiss.py \
  --scope-root . \
  --threshold 10 \
  --max-lines 50 \
  --json

python .claude/skills/sc-principles/scripts/validate_purity.py \
  --scope-root . \
  --core-only \
  --json

repos:
  - repo: local
    hooks:
      - id: kiss-check
        name: KISS Validation
        entry: python .claude/skills/sc-principles/scripts/validate_kiss.py --scope-root . --json
        language: python
        types: [python]
        pass_filenames: false

      - id: purity-check
        name: Purity Validation
        entry: python .claude/skills/sc-principles/scripts/validate_purity.py --scope-root . --json
        language: python
        types: [python]
        pass_filenames: false

def process(data, config, user):
    if data:
        if config.enabled:
            if user.has_permission:
                for item in data:
                    if item.valid:
                        # deep logic here

def process(data, config, user):
    if not can_process(data, config, user):
        return None
    return process_items(data)

def can_process(data, config, user):
    return data and config.enabled and user.has_permission

def process_items(data):
    return [process_item(item) for item in data if item.valid]

# In domain/calculator.py (CORE - should be pure)
def calculate_discount(user_id):
    user = db.query(User).get(user_id)  # I/O in core!
    print(f"Calculating for {user.name}")  # Side effect!
    return 0.2 if user.is_premium else 0.1

# In domain/calculator.py (CORE - now pure)
def calculate_discount(user: User) -> float:
    """Pure function - no I/O, just logic."""
    return 0.2 if user.is_premium else 0.1

# In adapters/discount_service.py (SHELL - I/O allowed)
def get_user_discount(user_id: int) -> float:
    user = user_repository.get(user_id)
    discount = calculate_discount(user)
    logger.info(f"Discount for {user.name}: {discount}")
    return discount

def process_payment(payment_type, amount):
    if payment_type == "credit":
        return process_credit(amount)
    elif payment_type == "debit":
        return process_debit(amount)
    elif payment_type == "crypto":  # New type = code change!
        return process_crypto(amount)

PROCESSORS = {
    "credit": process_credit,
    "debit": process_debit,
    "crypto": process_crypto,  # Add here, no function change
}

def process_payment(payment_type, amount):
    processor = PROCESSORS.get(payment_type)
    if not processor:
        raise ValueError(f"Unknown payment type: {payment_type}")
    return processor(amount)

def get_user(user_id):
    try:
        user = db.query(User).get(user_id)
        return user
    except:  # BAD: catches everything, hides bugs
        return None

def get_user(user_id):
    # Let database errors surface - they indicate real problems
    return db.query(User).get(user_id)

# Handle at the boundary (API layer)
@app.get("/users/{user_id}")
def api_get_user(user_id: int):
    try:
        return get_user(user_id)
    except DBError as e:
        logger.error("Database error", error=e, user_id=user_id)
        raise HTTPException(500, "Database unavailable")

$ /sc:principles src/ --report

KISS Validation: BLOCKED
Files analyzed: 12
Errors: 3, Warnings: 5

Violations:
  [ERROR] src/services/order.py:45 process_order: complexity = 15 (max: 10)
  [ERROR] src/utils/parser.py:12 parse_data: length = 78 (max: 50)
  [WARNING] src/domain/calc.py:8 calculate: parameters = 7 (max: 5)

Purity Validation: BLOCKED
Core violations: 2, Shell warnings: 1

Violations:
  [ERROR] src/domain/user.py:23 get_status: database - db.query (context: core)
  [ERROR] src/services/report.py:56 generate: file_io - open (context: core)

Recommendations:
  - COMPLEXITY: Extract helper functions, use early returns
  - DATABASE: Use repository pattern. Business logic receives data, not queries
  - FILE I/O: Move file operations to adapter layer

$ /sc:principles src/ --kiss-only --threshold 8

KISS Validation: PASSED
Files analyzed: 12
Errors: 0, Warnings: 2

$ /sc:principles src/ --strict

# All warnings become errors
# Any warning will block

python -m pytest .claude/skills/sc-principles/tests/ -v