import Foundation
import Moya
import CommonCrypto

/// JiaMiKey 的 MD5，预计算避免每次请求都算
private let jiaMiKeyMD5: String = {
    let key = "857d69d374694c1de46486d3bdaaac43"
    return SignPlugin.md5(key)
}()

/// 请求签名 Plugin
final class SignPlugin: PluginType {

    func prepare(_ request: URLRequest, target: any TargetType) -> URLRequest {
        var mutableRequest = request

        guard let url = request.url else { return mutableRequest }

        let timestamp = String(format: "%.0lf", Date().timeIntervalSince1970)
        let nonce = randomString(length: 32)

        var queryDict: [String: String] = [
            "timestamp": timestamp,
            "nonce": nonce
        ]

        // 收集 URL 已有的 query 参数，一并纳入签名
        if let components = URLComponents(url: url, resolvingAgainstBaseURL: false),
           let queryItems = components.queryItems {
            for item in queryItems {
                queryDict[item.name] = item.value ?? ""
            }
        }

        let bodyString: String
        if let httpBody = request.httpBody, !httpBody.isEmpty {
            bodyString = String(data: httpBody, encoding: .utf8) ?? ""
        } else {
            bodyString = ""
        }

        let queryString = sortedQueryString(queryDict)
        let signStr: String
        if bodyString.isEmpty {
            signStr = queryString + "&" + jiaMiKeyMD5
        } else {
            signStr = queryString + "&" + bodyString + "&" + jiaMiKeyMD5
        }
        let signature = Self.md5(signStr)

        // 剥离旧 query，替换为完整的签名 query
        let signedQuery = queryString + "&signature=" + signature
        var components = URLComponents(url: url, resolvingAgainstBaseURL: false)
        components?.percentEncodedQuery = signedQuery.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)

        if let newURL = components?.url {
            mutableRequest.url = newURL
        }

        return mutableRequest
    }

    private func sortedQueryString(_ dict: [String: String]) -> String {
        dict
            .sorted { $0.key < $1.key }
            .map { "\($0.key)=\($0.value)" }
            .joined(separator: "&")
    }

    private func randomString(length: Int) -> String {
        let chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        return String((0..<length).map { _ in chars.randomElement()! })
    }

    fileprivate static func md5(_ string: String) -> String {
        let cStr = string.cString(using: .utf8)
        let length = CC_LONG(strlen(cStr!))
        var digest = [UInt8](repeating: 0, count: Int(CC_MD5_DIGEST_LENGTH))
        CC_MD5(cStr, length, &digest)
        return digest.map { String(format: "%02x", $0) }.joined()
    }
}