import Foundation
import Capacitor

public class CapacitorUrlRequest: NSObject, URLSessionTaskDelegate {
    private var request: URLRequest;
    private var headers: [String:String];
    
    enum CapacitorUrlRequestError: Error {
        case serializationError(String?)
    }

    init(_ url: URL, method: String) {
        request = URLRequest(url: url)
        request.httpMethod = method
        headers = [:]
        if let lang = Locale.autoupdatingCurrent.languageCode {
            if let country = Locale.autoupdatingCurrent.regionCode {
                headers["Accept-Language"] = "\(lang)-\(country),\(lang);q=0.5"
            } else {
                headers["Accept-Language"] = "\(lang);q=0.5"
            }
            request.addValue(headers["Accept-Language"]!, forHTTPHeaderField: "Accept-Language")
        }
    }
    
    private func getRequestDataAsJson(_ data: JSValue) throws -> Data? {
        // We need to check if the JSON is valid before attempting to serialize, as JSONSerialization.data will not throw an exception that can be caught, and will cause the application to crash if it fails.
        if JSONSerialization.isValidJSONObject(data) {
            return try JSONSerialization.data(withJSONObject: data)
        } else {
            throw CapacitorUrlRequest.CapacitorUrlRequestError.serializationError("[ data ] argument for request of content-type [ application/json ] must be serializable to JSON")
        }
    }
    
    private func getRequestDataAsFormUrlEncoded(_ data: JSValue) throws -> Data? {
        guard var components = URLComponents(url: request.url!, resolvingAgainstBaseURL: false) else { return nil }
        components.queryItems = []
        
        guard let obj = data as? JSObject else {
            // Throw, other data types explicitly not supported
            throw CapacitorUrlRequestError.serializationError("[ data ] argument for request with content-type [ multipart/form-data ] may only be a plain javascript object")
        }
        
        obj.keys.forEach { (key: String) in
            components.queryItems?.append(URLQueryItem(name: key, value: "\(obj[key] ?? "")"))
        }
        
        
        if components.query != nil {
            return Data(components.query!.utf8)
        }

        return nil
    }
    
    private func getRequestDataAsMultipartFormData(_ data: JSValue) throws -> Data {
        guard let obj = data as? JSObject else {
            // Throw, other data types explicitly not supported.
            throw CapacitorUrlRequestError.serializationError("[ data ] argument for request with content-type [ application/x-www-form-urlencoded ] may only be a plain javascript object")
        }
        
        let strings: [String: String] = obj.compactMapValues { any in
            any as? String
        }
        
        var data = Data()
        let boundary = UUID().uuidString
        let contentType = "multipart/form-data; boundary=\(boundary)"
        request.setValue(contentType, forHTTPHeaderField: "Content-Type")
        headers["Content-Type"] = contentType
        
        strings.forEach { key, value in
            data.append("\r\n--\(boundary)\r\n".data(using: .utf8)!)
            data.append("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n".data(using: .utf8)!)
            data.append(value.data(using: .utf8)!)
        }
        data.append("\r\n--\(boundary)--\r\n".data(using: .utf8)!)
        
        return data
    }
    
    private func getRequestDataAsString(_ data: JSValue) throws -> Data {
        guard let stringData = data as? String else {
            throw CapacitorUrlRequestError.serializationError("[ data ] argument could not be parsed as string")
        }
        return Data(stringData.utf8)
    }

    func getRequestHeader(_ index: String) -> Any? {
        var normalized = [:] as [String:Any]
        self.headers.keys.forEach { (key: String) in
            normalized[key.lowercased()] = self.headers[key]
        }

        return normalized[index.lowercased()]
    }
    
    func getRequestData(_ body: JSValue, _ contentType: String) throws -> Data? {
        // If data can be parsed directly as a string, return that without processing.
        if let strVal = try? getRequestDataAsString(body) {
            return strVal
        } else if contentType.contains("application/json") {
            return try getRequestDataAsJson(body)
        } else if contentType.contains("application/x-www-form-urlencoded") {
            return try getRequestDataAsFormUrlEncoded(body)
        } else if contentType.contains("multipart/form-data") {
            return try getRequestDataAsMultipartFormData(body)
        } else {
            throw CapacitorUrlRequestError.serializationError("[ data ] argument could not be parsed for content type [ \(contentType) ]")
        }
    }

    public func setRequestHeaders(_ headers: [String: String]) {
        headers.keys.forEach { (key: String) in
            let value = headers[key]
            request.addValue(value!, forHTTPHeaderField: key)
            self.headers[key] = value
        }
    }
    
    public func setRequestBody(_ body: JSValue) throws {
        let contentType = self.getRequestHeader("Content-Type") as? String

        if contentType != nil {
            request.httpBody = try getRequestData(body, contentType!)
        }
    }

    public func setContentType(_ data: String?) {
        request.setValue(data, forHTTPHeaderField: "Content-Type")
    }

    public func setTimeout(_ timeout: TimeInterval) {
        request.timeoutInterval = timeout;
    }

    public func getUrlRequest() -> URLRequest {
        return request;
    }
    
    public func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {
        completionHandler(nil)
    }

    public func getUrlSession(_ call: CAPPluginCall) -> URLSession {
        let disableRedirects = call.getBool("disableRedirects") ?? false
        if (!disableRedirects) {
            return URLSession.shared
        }
        return URLSession(configuration: URLSessionConfiguration.default, delegate: self, delegateQueue: nil)
    }
}