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72 lines
2.1 KiB
Go
72 lines
2.1 KiB
Go
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package middleware
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import (
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"context"
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)
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// Handler provides the interface for performing the logic to obtain an output,
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// or error for the given input.
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type Handler interface {
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// Handle performs logic to obtain an output for the given input. Handler
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// should be decorated with middleware to perform input specific behavior.
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Handle(ctx context.Context, input interface{}) (
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output interface{}, metadata Metadata, err error,
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)
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}
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// HandlerFunc provides a wrapper around a function pointer to be used as a
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// middleware handler.
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type HandlerFunc func(ctx context.Context, input interface{}) (
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output interface{}, metadata Metadata, err error,
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)
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// Handle invokes the underlying function, returning the result.
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func (fn HandlerFunc) Handle(ctx context.Context, input interface{}) (
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output interface{}, metadata Metadata, err error,
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) {
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return fn(ctx, input)
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}
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// Middleware provides the interface to call handlers in a chain.
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type Middleware interface {
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// ID provides a unique identifier for the middleware.
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ID() string
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// Performs the middleware's handling of the input, returning the output,
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// or error. The middleware can invoke the next Handler if handling should
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// continue.
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HandleMiddleware(ctx context.Context, input interface{}, next Handler) (
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output interface{}, metadata Metadata, err error,
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)
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}
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// decoratedHandler wraps a middleware in order to to call the next handler in
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// the chain.
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type decoratedHandler struct {
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// The next handler to be called.
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Next Handler
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// The current middleware decorating the handler.
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With Middleware
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}
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// Handle implements the Handler interface to handle a operation invocation.
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func (m decoratedHandler) Handle(ctx context.Context, input interface{}) (
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output interface{}, metadata Metadata, err error,
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) {
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return m.With.HandleMiddleware(ctx, input, m.Next)
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}
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// DecorateHandler decorates a handler with a middleware. Wrapping the handler
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// with the middleware.
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func DecorateHandler(h Handler, with ...Middleware) Handler {
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for i := len(with) - 1; i >= 0; i-- {
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h = decoratedHandler{
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Next: h,
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With: with[i],
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}
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}
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return h
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}
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