//
//  KBSignUtils.m
//  keyBoard
//
//  Created by Mac on 2025/12/4.
//

#import "KBSignUtils.h"
#import <CommonCrypto/CommonCrypto.h>

@implementation KBSignUtils

+ (NSString *)urlEncode:(NSString *)value {
    if (!value) return @"";
    // 按 application/x-www-form-urlencoded 规则编码（更贴近后端常见实现）
    NSMutableCharacterSet *allowed = [NSMutableCharacterSet alphanumericCharacterSet];
    [allowed addCharactersInString:@"-._*"];
    NSString *encoded = [value stringByAddingPercentEncodingWithAllowedCharacters:allowed];
    if (!encoded) {
        return value;
    }
    // 空格改为 +（URLEncoder 风格）
    encoded = [encoded stringByReplacingOccurrencesOfString:@"%20" withString:@"+"];
    return encoded;
}

+ (NSString *)hmacSHA256:(NSString *)data secret:(NSString *)secret {
    const char *cKey  = [secret cStringUsingEncoding:NSUTF8StringEncoding];
    const char *cData = [data cStringUsingEncoding:NSUTF8StringEncoding];

    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];

    CCHmac(kCCHmacAlgSHA256,
           cKey,
           strlen(cKey),
           cData,
           strlen(cData),
           cHMAC);

    // 转十六进制小写字符串
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
        [output appendFormat:@"%02x", cHMAC[i]];
    }
    return output;
}

+ (NSString *)signWithParams:(NSDictionary<NSString *, NSString *> *)params
                      secret:(NSString *)secret {
    NSString *dataString = [self signSourceStringWithParams:params secret:secret];
    return [self hmacSHA256:dataString secret:secret];
}

+ (NSString *)signSourceStringWithParams:(NSDictionary<NSString *, NSString *> *)params
                                  secret:(NSString *)secret {

    // 1. 过滤空值 & sign 自身
    NSMutableDictionary<NSString *, NSString *> *filtered = [NSMutableDictionary dictionary];
    [params enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *obj, BOOL *stop) {
        if (!obj || obj.length == 0) return;
        if ([[key lowercaseString] isEqualToString:@"sign"]) return;
        filtered[key] = obj;
    }];

    // 2. 按 key 字典序排序
    NSArray<NSString *> *sortedKeys = [[filtered allKeys] sortedArrayUsingSelector:@selector(compare:)];

    // 3. 拼接 key=value&key2=value2...&secret=xxx
    NSMutableArray<NSString *> *components = [NSMutableArray array];
    for (NSString *key in sortedKeys) {
        NSString *value = filtered[key] ?: @"";
        NSString *encodedValue = [self urlEncode:value];
        NSString *part = [NSString stringWithFormat:@"%@=%@", key, encodedValue];
        [components addObject:part];
    }

    NSString *encodedSecret = [self urlEncode:secret ?: @""];
    NSString *secretPart = [NSString stringWithFormat:@"secret=%@", encodedSecret];
    [components addObject:secretPart];

    return [components componentsJoinedByString:@"&"];
}

+ (NSString *)currentTimestamp {
    NSTimeInterval ts = [[NSDate date] timeIntervalSince1970];
    long long seconds = (long long)ts;
    return [NSString stringWithFormat:@"%lld", seconds];
}

+ (NSString *)generateNonceWithLength:(NSUInteger)length {
    // 用 UUID 生成，去掉 - , 再截取前 length 位
    NSString *uuid = [[NSUUID UUID].UUIDString stringByReplacingOccurrencesOfString:@"-" withString:@""];
    if (length == 0 || length > uuid.length) {
        return uuid;
    }
    return [uuid substringToIndex:length];
}

@end