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package gus
import "context"
// Handler is a function which can turn a request into a response.
//
// A Handler can return a nil response, in which case the Server is expected
// to build the protocol-appropriate "Not Found" response.
type Handler func(context.Context, *Request) *Response
// Middleware is a handler decorator.
//
// It returns a handler which may call the passed-in handler or not, or may
// transform the request or response in some way.
type Middleware func(Handler) Handler
// FallthroughHandler builds a handler which tries multiple child handlers.
//
// The returned handler will invoke each of the passed-in handlers in order,
// stopping when it receives a non-nil response.
func FallthroughHandler(handlers ...Handler) Handler {
return func(ctx context.Context, request *Request) *Response {
for _, handler := range handlers {
if response := handler(ctx, request); response != nil {
return response
}
}
return nil
}
}
// Filter builds a middleware which only calls the wrapped under a condition.
//
// When the condition function returns false it instead invokes the
// test-failure handler. The failure handler may also be nil, in which case
// the final handler will return a nil response whenever the condition fails.
func Filter(
condition func(context.Context, *Request) bool,
failure Handler,
) Middleware {
return func(success Handler) Handler {
return func(ctx context.Context, request *Request) *Response {
if condition(ctx, request) {
return success(ctx, request)
}
if failure == nil {
return nil
}
return failure(ctx, request)
}
}
}
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