#!/usr/bin/env node

const readline = require('readline');

function calculateEntropy(probabilities) {
    return -probabilities.reduce((acc, p) => acc + (p > 0 ? p * Math.log2(p) : 0), 0);
}

function validateProbabilities(probabilities) {
    if (probabilities.length === 0 || !probabilities.every(p => p >= 0 && p <= 1)) {
        throw new Error("每个概率必须在 0 和 1 之间");
    }
    const total = probabilities.reduce((acc, p) => acc + p, 0);
    if (total !== 1) {
        throw new Error("概率之和必须等于 1");
    }
}

function parseInput(args) {
    if (args.length === 0) {
        return promptUser();
    }
    
    if (args[0].includes(',')) {
        return args[0].split(',').map(Number);
    } else if (args[0].includes(' ')) {
        return args[0].split(' ').map(Number);
    } else {
        throw new Error("输入格式错误：请使用逗号或空格分隔概率，不要混合使用");
    }
}

function promptUser() {
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout
    });
    
    return new Promise((resolve) => {
        rl.question("请输入概率（用逗号或空格分隔）：", (answer) => {
            rl.close();
            resolve(answer.trim().split(/\s*[, ]\s*/).map(Number));
        });
    });
}

async function main() {
    try {
        const input_probs = parseInput(process.argv.slice(2));
        validateProbabilities(input_probs);
        const entropy = calculateEntropy(input_probs);
        console.log(`信源熵 H(p) = ${entropy}`);
    } catch (error) {
        console.error(`错误: ${error.message}`);
    }
}

main();