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

// Define expected interface for RPN calculator module
const expectedRPNCalculatorInterface = [
  'push',
  'pop',
  'operate', 
  'clear',
  'getStack',
  'evaluate'
];

// Test if RPN calculator module exists and has expected interface
function testRPNCalculatorInterface() {
    try {
        // This will fail since rpn-calculator.js doesn't exist yet
        const rpnCalc = new RPNCalculator();
        
        // Check if all expected methods exist
        for (const method of expectedRPNCalculatorInterface) {
            if (typeof rpnCalc[method] !== 'function') {
                throw new Error(`Method ${method} does not exist on RPNCalculator`);
            }
        }
        
        // Test basic RPN functionality
        // Push should add value to stack
        rpnCalc.push(3);
        const stackAfterPush = rpnCalc.getStack();
        if (stackAfterPush.length !== 1 || stackAfterPush[0] !== 3) {
            throw new Error('RPN calculator push method does not work correctly');
        }
        
        // Pop should remove and return top value from stack
        const poppedValue = rpnCalc.pop();
        if (poppedValue !== 3) {
            throw new Error('RPN calculator pop method does not return correct value');
        }
        
        // Stack should be empty after pop
        if (rpnCalc.getStack().length !== 0) {
            throw new Error('RPN calculator stack not empty after pop');
        }
        
        // Clear should empty the stack
        rpnCalc.push(1);
        rpnCalc.push(2);
        rpnCalc.clear();
        if (rpnCalc.getStack().length !== 0) {
            throw new Error('RPN calculator clear method does not empty the stack');
        }
        
        // Operate should perform operation on stack values
        rpnCalc.push(2);
        rpnCalc.push(3);
        const result = rpnCalc.operate('+');
        if (result !== 5) {
            throw new Error('RPN calculator operate method does not return correct result for addition');
        }
        
        // Evaluate should handle RPN expressions
        const evalResult = rpnCalc.evaluate('2 3 +');
        if (evalResult !== 5) {
            throw new Error('RPN 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('RPN Calculator Interface Contract', testRPNCalculatorInterface);
} else {
    console.log('Test harness not loaded. Run with test runner.');
}