1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
package middleware
import (
"context"
)
// Handler provides the interface for performing the logic to obtain an output,
// or error for the given input.
type Handler interface {
// Handle performs logic to obtain an output for the given input. Handler
// should be decorated with middleware to perform input specific behavior.
Handle(ctx context.Context, input interface{}) (
output interface{}, metadata Metadata, err error,
)
}
// HandlerFunc provides a wrapper around a function pointer to be used as a
// middleware handler.
type HandlerFunc func(ctx context.Context, input interface{}) (
output interface{}, metadata Metadata, err error,
)
// Handle invokes the underlying function, returning the result.
func (fn HandlerFunc) Handle(ctx context.Context, input interface{}) (
output interface{}, metadata Metadata, err error,
) {
return fn(ctx, input)
}
// Middleware provides the interface to call handlers in a chain.
type Middleware interface {
// ID provides a unique identifier for the middleware.
ID() string
// Performs the middleware's handling of the input, returning the output,
// or error. The middleware can invoke the next Handler if handling should
// continue.
HandleMiddleware(ctx context.Context, input interface{}, next Handler) (
output interface{}, metadata Metadata, err error,
)
}
// decoratedHandler wraps a middleware in order to to call the next handler in
// the chain.
type decoratedHandler struct {
// The next handler to be called.
Next Handler
// The current middleware decorating the handler.
With Middleware
}
// Handle implements the Handler interface to handle a operation invocation.
func (m decoratedHandler) Handle(ctx context.Context, input interface{}) (
output interface{}, metadata Metadata, err error,
) {
return m.With.HandleMiddleware(ctx, input, m.Next)
}
// DecorateHandler decorates a handler with a middleware. Wrapping the handler
// with the middleware.
func DecorateHandler(h Handler, with ...Middleware) Handler {
for i := len(with) - 1; i >= 0; i-- {
h = decoratedHandler{
Next: h,
With: with[i],
}
}
return h
}
|
