func (prc *ResizeProcessor) getResampling(params imageserver.Params) (gift.Resampling, error) {
	if !params.Has("resampling") {
		if prc.DefaultResampling != nil {
			return prc.DefaultResampling, nil
		}
		return gift.NearestNeighborResampling, nil
	}
	rsp, err := params.GetString("resampling")
	if err != nil {
		return nil, err
	}
	switch rsp {
	case "nearest_neighbor":
		return gift.NearestNeighborResampling, nil
	case "box":
		return gift.BoxResampling, nil
	case "linear":
		return gift.LinearResampling, nil
	case "cubic":
		return gift.CubicResampling, nil
	case "lanczos":
		return gift.LanczosResampling, nil
	}
	return nil, &imageserver.ParamError{Param: "resampling", Message: "invalid value"}
}

func (server *Server) buildArgumentsMonochrome(arguments *list.List, params imageserver.Params) error {
	monochrome, _ := params.GetBool("monochrome")
	if monochrome {
		arguments.PushBack("-monochrome")
	}
	return nil
}

func (server *Server) buildArgumentsCrop(arguments *list.List, params imageserver.Params) error {
	if !params.Has("crop") {
		return nil
	}
	crop, _ := params.GetString("crop")
	cropArgs := strings.Split(crop, ",")
	cropArgsLen := len(cropArgs)
	if cropArgsLen != 2 && cropArgsLen != 4 {
		return &imageserver.ParamError{Param: "crop", Message: "Invalid crop request, parameters number mismatch"}
	}
	if cropArgsLen == 2 {
		width, _ := strconv.Atoi(cropArgs[0])
		height, _ := strconv.Atoi(cropArgs[1])
		arguments.PushBack("-crop")
		arguments.PushBack(fmt.Sprintf("%dx%d", width, height))
		arguments.PushBack("+repage")
	}
	if cropArgsLen == 4 {
		width, _ := strconv.Atoi(cropArgs[0])
		height, _ := strconv.Atoi(cropArgs[1])
		x, _ := strconv.Atoi(cropArgs[2])
		y, _ := strconv.Atoi(cropArgs[3])
		arguments.PushBack("-crop")
		arguments.PushBack(fmt.Sprintf("%dx%d+%d+%d", width, height, x, y))
		arguments.PushBack("+repage")
	}
	return nil
}

func (server *Server) buildArgumentsFlop(arguments *list.List, params imageserver.Params) error {
	flop, _ := params.GetBool("flop")
	if flop {
		arguments.PushBack("-flop")
	}
	return nil
}

func process(nim image.Image, params imageserver.Params) (image.Image, error) {
	if params.Empty() {
		return nim, nil
	}
	width, err := getDimension("width", params)
	if err != nil {
		return nil, err
	}
	height, err := getDimension("height", params)
	if err != nil {
		return nil, err
	}
	if width == 0 && height == 0 {
		return nim, nil
	}
	interp, err := getInterpolation(params)
	if err != nil {
		return nil, err
	}
	mode, err := getModeFunc(params)
	if err != nil {
		return nil, err
	}
	nim = mode(width, height, nim, interp)
	return nim, nil
}

func (prc *Processor) getInterpolation(params imageserver.Params) (resize.InterpolationFunction, error) {
	if !params.Has("interpolation") {
		return prc.DefaultInterpolation, nil
	}
	interpolation, err := params.GetString("interpolation")
	if err != nil {
		return 0, err
	}
	switch interpolation {
	case "nearest_neighbor":
		return resize.NearestNeighbor, nil
	case "bilinear":
		return resize.Bilinear, nil
	case "bicubic":
		return resize.Bicubic, nil
	case "mitchell_netravali":
		return resize.MitchellNetravali, nil
	case "lanczos2":
		return resize.Lanczos2, nil
	case "lanczos3":
		return resize.Lanczos3, nil
	default:
		return 0, &imageserver.ParamError{Param: "interpolation", Message: "invalid value"}
	}
}

func (server *Server) buildArgumentsGravity(arguments *list.List, params imageserver.Params) error {
	gravity, _ := params.GetString("gravity")
	var translatedGravity string
	if gravity != "" {
		switch {
		case gravity == "n":
			translatedGravity = "North"
		case gravity == "s":
			translatedGravity = "South"
		case gravity == "e":
			translatedGravity = "East"
		case gravity == "w":
			translatedGravity = "West"
		case gravity == "ne":
			translatedGravity = "NorthEast"
		case gravity == "se":
			translatedGravity = "SouthEast"
		case gravity == "nw":
			translatedGravity = "NorthWest"
		case gravity == "sw":
			translatedGravity = "SouthWest"
		}
		if translatedGravity == "" {
			return &imageserver.ParamError{Param: "gravity", Message: "gravity should n, s, e, w, ne, se, nw or sw"}
		}
	} else {
		// Default gravity is center.
		translatedGravity = "Center"
	}

	arguments.PushBack("-gravity")
	arguments.PushBack(fmt.Sprintf("%s", translatedGravity))
	return nil
}

func (server *Server) buildArgumentsGrey(arguments *list.List, params imageserver.Params) error {
	grey, _ := params.GetBool("grey")
	if grey {
		arguments.PushBack("-colorspace")
		arguments.PushBack("GRAY")
	}
	return nil
}

func (server *Server) buildArgumentsInterlace(arguments *list.List, params imageserver.Params) error {
	interlace, _ := params.GetBool("no_interlace")
	if !interlace {
		arguments.PushBack("-interlace")
		arguments.PushBack("Line")
	}
	return nil
}

func (server *Server) buildArgumentsTrim(arguments *list.List, params imageserver.Params) error {
	trim, _ := params.GetBool("trim")
	if trim {
		// We must execute trim first. (order of operations)
		arguments.PushFront("-trim")
	}
	return nil
}

// Get implements imageserver.Server.
func (s *Server) Get(params imageserver.Params) (*imageserver.Image, error) {
	src, err := params.Get(Param)
	if err != nil {
		return nil, err
	}
	params = imageserver.Params{Param: src}
	return s.Server.Get(params)
}

func (srv *Server) getPath(params imageserver.Params) (string, error) {
	src, err := params.GetString(imageserver_source.Param)
	if err != nil {
		return "", err
	}
	// This trick comes from net/http.Dir.Open().
	// It allows to "jail" the path inside the root.
	return filepath.Join(srv.Root, filepath.FromSlash(path.Clean("/"+src))), nil
}

func TestParseQueryStringUndefined(t *testing.T) {
	req, err := http.NewRequest("GET", "http://localhost", nil)
	if err != nil {
		t.Fatal(err)
	}
	params := imageserver.Params{}
	ParseQueryString("string", req, params)
	if params.Has("string") {
		t.Fatal("should not be set")
	}
}

// ParseQueryFloat takes the param from the query string, parse it as a float64 and add it to params.
func ParseQueryFloat(param string, req *http.Request, params imageserver.Params) error {
	s := req.URL.Query().Get(param)
	if s == "" {
		return nil
	}
	f, err := strconv.ParseFloat(s, 64)
	if err != nil {
		return newParseTypeParamError(param, "float", err)
	}
	params.Set(param, f)
	return nil
}

func (server *Server) buildArgumentsRotate(arguments *list.List, params imageserver.Params) error {
	rotate, _ := params.GetInt("rotate")
	if rotate != 0 {
		if rotate < 0 || rotate > 359 {
			return &imageserver.ParamError{Param: "rotate", Message: "Invalid rotate parameter"}
		}

		arguments.PushBack("-rotate")
		arguments.PushBack(strconv.Itoa(rotate))
	}
	return nil
}

// ParseQueryInt takes the param from the query string, parse it as an int and add it to params.
func ParseQueryInt(param string, req *http.Request, params imageserver.Params) error {
	s := req.URL.Query().Get(param)
	if s == "" {
		return nil
	}
	i, err := strconv.Atoi(s)
	if err != nil {
		return newParseTypeParamError(param, "int", err)
	}
	params.Set(param, i)
	return nil
}

// ParseQueryBool takes the param from the query string, parse it as an bool and add it to params.
func ParseQueryBool(param string, req *http.Request, params imageserver.Params) error {
	s := req.URL.Query().Get(param)
	if s == "" {
		return nil
	}
	b, err := strconv.ParseBool(s)
	if err != nil {
		return newParseTypeParamError(param, "bool", err)
	}
	params.Set(param, b)
	return nil
}

func getDimension(name string, params imageserver.Params) (int, error) {
	if !params.Has(name) {
		return 0, nil
	}
	dimension, err := params.GetInt(name)
	if err != nil {
		return 0, err
	}
	if dimension < 0 {
		return 0, &imageserver.ParamError{Param: name, Message: "must be greater than or equal to 0"}
	}
	return dimension, nil
}

// Get implements Server.
func (srv *ValidateParamsServer) Get(params imageserver.Params) (*imageserver.Image, error) {
	if params.Has(Param) {
		params, err := params.GetParams(Param)
		if err != nil {
			return nil, err
		}
		err = srv.validate(params)
		if err != nil {
			return nil, wrapParamError(err)
		}
	}
	return srv.Server.Get(params)
}

// Parse implements Parser.
func (parser *Parser) Parse(req *http.Request, params imageserver.Params) error {
	p := imageserver.Params{}
	err := parse(req, p)
	if err != nil {
		if err, ok := err.(*imageserver.ParamError); ok {
			err.Param = Param + "." + err.Param
		}
		return err
	}
	if !p.Empty() {
		params.Set(Param, p)
	}
	return nil
}