// Contract test for Core Calculator API
// This test should fail initially since the calculator module doesn't exist yet

// Define expected interface for calculator module
const expectedCalculatorInterface = [
  'evaluate',
  'add', 
  'subtract',
  'multiply',
  'divide',
  'percentage',
  'toggleSign',
  'clear',
  'getCurrentDisplay'
];

// Test if calculator module exists and has expected interface
function testCalculatorInterface() {
    try {
        // This will fail since calculator.js doesn't exist yet
        const calc = new Calculator();
        
        // Check if all expected methods exist
        for (const method of expectedCalculatorInterface) {
            if (typeof calc[method] !== 'function') {
                throw new Error(`Method ${method} does not exist on Calculator`);
            }
        }
        
        // Test basic functionality
        // Add should return sum of two numbers
        if (calc.add(2, 3) !== 5) {
            throw new Error('Calculator add method does not return correct result');
        }
        
        // Subtract should return difference
        if (calc.subtract(5, 3) !== 2) {
            throw new Error('Calculator subtract method does not return correct result');
        }
        
        // Multiply should return product
        if (calc.multiply(4, 5) !== 20) {
            throw new Error('Calculator multiply method does not return correct result');
        }
        
        // Divide should return quotient
        if (calc.divide(10, 2) !== 5) {
            throw new Error('Calculator divide method does not return correct result');
        }
        
        // Division by zero should return Infinity
        if (!isFinite(calc.divide(10, 0))) {
            // This is expected, division by zero returns Infinity
        } else {
            throw new Error('Calculator divide by zero does not return Infinity');
        }
        
        // Percentage should convert percentage to decimal
        if (calc.percentage(50) !== 0.5) {
            throw new Error('Calculator percentage method does not return correct result');
        }
        
        // ToggleSign should change sign
        if (calc.toggleSign(5) !== -5) {
            throw new Error('Calculator toggleSign method does not return correct result');
        }
        
        if (calc.toggleSign(-5) !== 5) {
            throw new Error('Calculator toggleSign method does not return correct result for negative number');
        }
        
        // Clear should reset to initial state
        calc.clear();
        if (calc.getCurrentDisplay() !== '0') {
            throw new Error('Calculator clear method does not reset to initial state');
        }
        
        // Evaluate should handle simple expressions
        if (calc.evaluate('2 + 3') !== 5) {
            throw new Error('Calculator evaluate method does not return correct result');
        }
        
        return true; // All tests passed
    } catch (error) {
        return { error: error.message };
    }
}

// Add test to global test collection
if (typeof addTest !== 'undefined') {
    addTest('Calculator Interface Contract', testCalculatorInterface);
} else {
    console.log('Test harness not loaded. Run with test runner.');
}