error_handling_enhanced.ruff

# Enhanced Error Handling Features in Ruff
#
# This example demonstrates all new error handling capabilities:
# - Error properties: err.message, err.stack, err.line
# - Custom error types with structs
# - Error chaining with cause property
# - Stack traces from nested function calls

print("==================================================")
print("Enhanced Error Handling Examples")
print("==================================================")
print("")

# ==============================================================================
# Example 1: Accessing Error Properties
# ==============================================================================

print("--- Example 1: Error Properties ---")
try {
    throw("This is an error message")
} except err {
    print("Error message: " + err.message)
    print("Line number: " + err.line)
    print("Stack depth: " + len(err.stack))
}
print("")

# ==============================================================================
# Example 2: Custom Error Types with Structs
# ==============================================================================

print("--- Example 2: Custom Error Types ---")

struct ValidationError {
    field: string,
    message: string,
    value: string
}

func validate_email(email: string) {
    if !contains(email, "@") {
        error := ValidationError {
            field: "email",
            message: "Email must contain @ symbol",
            value: email
        }
        throw(error)
    }
    return true
}

try {
    validate_email("invalid-email")
} except err {
    print("Validation failed: " + err.message)
}

try {
    validate_email("user@example.com")
    print("Email validation passed!")
} except err {
    print("This won't print")
}
print("")

# ==============================================================================
# Example 3: Stack Traces in Function Calls
# ==============================================================================

print("--- Example 3: Stack Traces ---")

func function_a() {
    function_b()
}

func function_b() {
    function_c()
}

func function_c() {
    throw("Error from function_c")
}

try {
    function_a()
} except err {
    print("Caught error: " + err.message)
    print("Stack trace:")
    
    i := 0
    while i < len(err.stack) {
        frame := err.stack[i]
        print("  [" + i + "] " + frame)
        i := i + 1
    }
}
print("")

# ==============================================================================
# Example 4: Error Chaining
# ==============================================================================

print("--- Example 4: Error Chaining ---")

struct DatabaseError {
    message: string,
    cause: string
}

func query_database(query: string) {
    throw("Connection timeout")
}

func fetch_user_data(user_id: int) {
    try {
        query_database("SELECT * FROM users WHERE id = " + user_id)
    } except db_err {
        error := DatabaseError {
            message: "Failed to fetch user data for ID " + user_id,
            cause: db_err.message
        }
        throw(error)
    }
}

try {
    fetch_user_data(123)
} except err {
    print("Application error: " + err.message)
}
print("")

# ==============================================================================
# Example 5: Multiple Error Types
# ==============================================================================

print("--- Example 5: Multiple Error Types ---")

struct NetworkError {
    message: string,
    status: int
}

struct ParseError {
    message: string,
    data: string
}

func process_request(simulate_network: bool, simulate_parse: bool) {
    if simulate_network {
        error := NetworkError {
            message: "Failed to connect to server",
            status: 500
        }
        throw(error)
    }
    
    if simulate_parse {
        error := ParseError {
            message: "Invalid JSON format",
            data: "{invalid}"
        }
        throw(error)
    }
    
    return "Success"
}

try {
    process_request(true, false)
} except err {
    print("Network error: " + err.message)
}

try {
    process_request(false, true)
} except err {
    print("Parse error: " + err.message)
}

try {
    result := process_request(false, false)
    print("Request succeeded: " + result)
} except err {
    print("This won't print")
}
print("")

# ==============================================================================
# Example 6: Error Recovery Pattern
# ==============================================================================

print("--- Example 6: Error Recovery ---")

func safe_divide(a: float, b: float) {
    if b == 0.0 {
        throw("Division by zero")
    }
    return a / b
}

operations := [[10.0, 2.0], [20.0, 0.0], [15.0, 3.0], [8.0, 0.0]]
successful := 0
failed := 0

i := 0
while i < len(operations) {
    op := operations[i]
    a := op[0]
    b := op[1]
    
    try {
        result := safe_divide(a, b)
        print("✓ " + a + " / " + b + " = " + result)
        successful := successful + 1
    } except err {
        print("✗ " + a + " / " + b + " failed: " + err.message)
        failed := failed + 1
    }
    
    i := i + 1
}

print("Summary: " + successful + " succeeded, " + failed + " failed")
print("")

# ==============================================================================
# Example 7: Nested Try-Except
# ==============================================================================

print("--- Example 7: Nested Try-Except ---")

func risky_inner() {
    throw("Inner error")
}

func risky_outer() {
    throw("Outer error")
}

try {
    print("Outer try block started")
    
    try {
        print("Inner try block started")
        risky_inner()
    } except inner_err {
        print("Caught inner error: " + inner_err.message)
    }
    
    print("Between try-except blocks")
    risky_outer()
    
} except outer_err {
    print("Caught outer error: " + outer_err.message)
}
print("")

# ==============================================================================
# Example 8: Real-World Scenario - User Registration
# ==============================================================================

print("--- Example 8: User Registration Validation ---")

struct User {
    username: string,
    email: string,
    age: int
}

func validate_username(username: string) {
    if len(username) < 3 {
        throw("Username must be at least 3 characters long")
    }
    if len(username) > 20 {
        throw("Username cannot exceed 20 characters")
    }
}

func validate_user_email(email: string) {
    if len(email) == 0 {
        throw("Email is required")
    }
    if !contains(email, "@") {
        throw("Email must contain @ symbol")
    }
    if !contains(email, ".") {
        throw("Email must contain a domain")
    }
}

func validate_user_age(age: int) {
    if age < 13 {
        throw("User must be at least 13 years old")
    }
    if age > 120 {
        throw("Age must be realistic")
    }
}

func create_user(username: string, email: string, age: int) {
    validate_username(username)
    validate_user_email(email)
    validate_user_age(age)
    
    user := User {
        username: username,
        email: email,
        age: age
    }
    
    return user
}

# Test Case 1: Invalid username
print("Test 1: Invalid username")
try {
    user := create_user("ab", "test@example.com", 25)
    print("User created successfully")
} except err {
    print("Registration failed: " + err.message)
}

# Test Case 2: Invalid email
print("Test 2: Invalid email")
try {
    user := create_user("john_doe", "invalid-email", 25)
    print("User created successfully")
} except err {
    print("Registration failed: " + err.message)
}

# Test Case 3: Invalid age
print("Test 3: Invalid age")
try {
    user := create_user("john_doe", "john@example.com", 10)
    print("User created successfully")
} except err {
    print("Registration failed: " + err.message)
}

# Test Case 4: Valid user
print("Test 4: Valid user")
try {
    user := create_user("john_doe", "john@example.com", 25)
    print("✓ User created successfully!")
    print("  Username: john_doe")
    print("  Email: john@example.com")
    print("  Age: 25")
} except err {
    print("Registration failed: " + err.message)
}
print("")

print("==================================================")
print("All examples completed successfully!")
print("==================================================")