import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.net.URI;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.*;

public class AmazonAPISigner {
    
    private static final String HMAC_SHA256_ALGORITHM = "HmacSHA256";
    private static final String AWS4_HMAC_SHA256 = "AWS4-HMAC-SHA256";
    private static final String ISO8601_FORMAT = "yyyyMMdd'T'HHmmss'Z'";
    private static final String DATE_FORMAT = "yyyyMMdd";
    
    public static void main(String[] args) throws Exception {
        String accessKey = "YOUR_ACCESS_KEY";
        String secretKey = "YOUR_SECRET_KEY";
        String region = "us-west-2";
        String service = "ProductAdvertisingAPI";
        
        // 示例请求参数
        Map<String, String> params = new HashMap<>();
        params.put("Operation", "ItemSearch");
        params.put("Keywords", "Harry Potter");
        params.put("SearchIndex", "Books");
        params.put("ResponseGroup", "Images,ItemAttributes,Offers");
        
        // 生成签名请求
        SignedRequestHelper helper = new SignedRequestHelper(accessKey, secretKey, region, service);
        String url = helper.sign(params);
        
        System.out.println("Signed URL: " + url);
    }
    
    static class SignedRequestHelper {
        private final String accessKey;
        private final String secretKey;
        private final String region;
        private final String service;
        
        public SignedRequestHelper(String accessKey, String secretKey, String region, String service) {
            this.accessKey = accessKey;
            this.secretKey = secretKey;
            this.region = region;
            this.service = service;
        }
        
        public String sign(Map<String, String> params) throws Exception {
            // 添加必要参数
            params.put("Service", service);
            params.put("AWSAccessKeyId", accessKey);
            params.put("Timestamp", timestamp());
            params.put("SignatureVersion", "2");
            params.put("SignatureMethod", "HmacSHA256");
            
            // 对参数进行排序
            TreeMap<String, String> sortedParams = new TreeMap<>(params);
            
            // 创建规范查询字符串
            String canonicalQS = canonicalize(sortedParams);
            
            // 创建待签字符串
            String stringToSign = stringToSign(canonicalQS);
            
            // 计算签名
            String signature = sign(stringToSign, secretKey);
            
            // 将签名添加到查询字符串
            return "http://webservices.amazon.com/onca/xml?" + canonicalQS + "&Signature=" + URLEncoder.encode(signature, StandardCharsets.UTF_8.name());
        }
        
        private String timestamp() {
            SimpleDateFormat df = new SimpleDateFormat(ISO8601_FORMAT);
            df.setTimeZone(TimeZone.getTimeZone("UTC"));
            return df.format(new Date());
        }
        
        private String canonicalize(TreeMap<String, String> sortedParamMap) {
            StringBuilder sb = new StringBuilder();
            for (Map.Entry<String, String> entry : sortedParamMap.entrySet()) {
                if (sb.length() > 0) {
                    sb.append("&");
                }
                sb.append(URLEncoder.encode(entry.getKey(), StandardCharsets.UTF_8))
                  .append("=")
                  .append(URLEncoder.encode(entry.getValue(), StandardCharsets.UTF_8));
            }
            return sb.toString();
        }
        
        private String stringToSign(String canonicalQS) {
            return "GET\nwebservices.amazon.com\n/onca/xml\n" + canonicalQS;
        }
        
        private String sign(String data, String key) throws NoSuchAlgorithmException, InvalidKeyException {
            SecretKeySpec signingKey = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), HMAC_SHA256_ALGORITHM);
            Mac mac = Mac.getInstance(HMAC_SHA256_ALGORITHM);
            mac.init(signingKey);
            byte[] rawHmac = mac.doFinal(data.getBytes(StandardCharsets.UTF_8));
            return Base64.getEncoder().encodeToString(rawHmac);
        }
    }
}