requester

type Client interface {
	// SetHTTPClient sets a private HTTP client instance for the current client.
	// If a nil is given, the built-in default HTTP client is used.
	SetHTTPClient(*http.Client) Client

	// SetTimeout sets a request timeout period for the current client.
	// Setting it to 0 will never time out.
	// This timeout period can be overridden by each request timeout setting.
	SetTimeout(time.Duration) Client

	// GetCommonHeaders returns the common request headers of the current client.
	GetCommonHeaders() http.Header

	// SetCommonHeader sets a common request header of the current client.
	// If the given request header value is an empty string, the corresponding request
	// header will be deleted.
	SetCommonHeader(string, string) Client

	// SetCommonHeaders resets the common request headers of the current client.
	// If nil is given, all common request headers will be deleted.
	SetCommonHeaders(http.Header) Client

	// SetResponder sets the given responder to the current client.
	SetResponder(Responder) Client

	// New returns a new request instance from the given uri.
	New(string) Request

	// Do obtains and initializes the request object from the global request object pool,
	// and will immediately reclaim the request object after the given closure is completed.
	// This method assumes that the request object will not be referenced by space outside the closure.
	Do(string, func(Request) (Response, error)) (Response, error)

	// Head uses the given parameters to send a request and return the Response.
	// This method will send the request using the HEAD method.
	Head(string, url.Values) (Response, error)

	// Get uses the given parameters to send a request and return the Response.
	// This method will send the request using the GET method.
	Get(string, url.Values) (Response, error)

	// Post uses the given parameters to send a request and return the Response.
	// This method will send the request using the POST method.
	Post(string, interface{}) (Response, error)

	// PostJSON uses the given parameters to send a request and return the Response.
	// This method will send the request using the POST method.
	// This method encodes the request body as json data and sends it.
	PostJSON(string, interface{}) (Response, error)

	// PostXML uses the given parameters to send a request and return the Response.
	// This method will send the request using the POST method.
	// This method encodes the request body as xml data and sends it.
	PostXML(string, interface{}) (Response, error)

	// PostForm uses the given parameters to send a request and return the Response.
	// This method will send the request using the POST method.
	// This method encodes the request body as form data (urlencoded) and sends it.
	PostForm(string, url.Values) (Response, error)

	// UploadFile uploads a file with the given parameters and returns the Response.
	// This method will send the request using the POST method.
	// This method encodes the request body as form data and sends it.
	// This method supports using string paths, opened file descriptors and downstream
	// uploaded files as upload targets.
	UploadFile(string, string, interface{}) (Response, error)
}

type Request interface {
	// WithMethod adds the default request method of the current request.
	WithMethod(string) Request

	// WithResponder adds the given responder to the current request.
	WithResponder(Responder) Request

	// WithHeader adds a request header to the current request.
	// If the given request header value is an empty string, the corresponding request
	// header will be deleted.
	WithHeader(string, string) Request

	// WithContentType adds the ContentType header information of the current request.
	WithContentType(string) Request

	// WithHeaders adds and replaces some headers to the current request.
	WithHeaders(http.Header) Request

	// WithContext adds a context to the current request.
	// If the given context is nil, context.Background() is automatically used.
	WithContext(context.Context) Request

	// WithQuery adds a query parameter to the current request.
	WithQuery(string, string) Request

	// WithQueryValue adds a query parameter to the current request.
	// This method will automatically convert the given parameter value to a string.
	WithQueryValue(string, interface{}) Request

	// WithQueries adds and replaces some query parameters to the current request.
	WithQueries(url.Values) Request

	// WithTimeout adds a timeout for the current request.
	// If the given timeout period is zero, the client's timeout setting is used.
	WithTimeout(time.Duration) Request

	// WithBody adds request body to the current request.
	WithBody(interface{}) Request

	// WithJSONBody adds the request body as json.
	// This method will force set "Content-Type" to "application/json".
	WithJSONBody(interface{}) Request

	// WithRawJSONBody adds the request body as raw json.
	// This method will force set "Content-Type" to "application/json".
	WithRawJSONBody([]byte) Request

	// WithXMLBody adds the request body as xml.
	// This method will force set "Content-Type" to "application/xml".
	WithXMLBody(interface{}) Request

	// WithRawXMLBody adds the request body as raw xml.
	// This method will force set "Content-Type" to "application/xml".
	WithRawXMLBody([]byte) Request

	// WithFormBody adds the request body as form (urlencoded).
	// This method will force set "Content-Type" to "application/x-www-form-urlencoded".
	WithFormBody(url.Values) Request

	// Head sends the current request and returns the received response.
	// This method will send the request using the HEAD method.
	Head() (Response, error)

	// Get sends the current request and returns the received response.
	// This method will send the request using the GET method.
	Get() (Response, error)

	// Post sends the current request and returns the received response.
	// This method will send the request using the POST method.
	Post() (Response, error)

	// Send sends the current request and returns the received response.
	Send() (Response, error)

	// SendBy sends the current request and returns the received response.
	// This method will send the request using the given request method.
	SendBy(string) (Response, error)

	// WithFormDataField adds a form data for uploading to the current request.
	// If the given form value is nil, delete the corresponding form key.
	WithFormDataField(string, interface{}) Request

	// WithFormDataFile adds a file target for uploading to the current request.
	// If the given form value is nil, delete the corresponding form key.
	// This method supports adding string paths, opened file descriptors and
	// downstream uploaded files as upload targets.
	WithFormDataFile(string, interface{}) Request

	// WithFormDataFileFromReader adds an upload target to the current request from
	// the given reader and file name.
	// If the given reader is nil, delete the corresponding form key.
	WithFormDataFileFromReader(string, string, io.Reader) Request

	// ClearFormData removes all uploaded form data from the current request.
	// If you need to reuse the current request instance to send multiple upload requests,
	// you should clean up each time before setting new form data (for the added file descriptor,
	// because the position of the cursor is uncertain, it may cause unexpected results ).
	ClearFormData() Request

	// Upload sends the current upload request and receives the response.
	// This method will send the request using the POST method.
	Upload() (Response, error)

	// UploadBy sends the current upload request and receives the response.
	// This method will send the request using the given request method.
	// This method only supports POST method and PUT method.
	UploadBy(string) (Response, error)

	// Clear cleans up the current request instance so that it can be reused.
	// This method will not cut the connection with the client, nor will it
	// change the request url.
	Clear() Request
}

type Responder func(r *http.Response, noBody bool) (Response, error)

type Response interface {
	fmt.Stringer

	// Headers method returns all response headers.
	Headers() http.Header

	// StatusCode returns the status code of the response.
	StatusCode() int

	// Status returns the status text of the response.
	Status() string

	// Body returns the response body, or nil if there is no response body.
	// For HEAD request, nil is always returned.
	Body() []byte

	// Len returns the length of the response body.
	Len() int

	// JSON binds the response body to the given object as json.
	JSON(interface{}) error

	// XML binds the response body to the given object as xml.
	XML(interface{}) error
}