86 lines
2.7 KiB
Go
86 lines
2.7 KiB
Go
package tcp
|
|
|
|
import (
|
|
"fmt"
|
|
)
|
|
|
|
// Constructor A constructor for a piece of TCP middleware.
|
|
// Some TCP middleware use this constructor out of the box,
|
|
// so in most cases you can just pass somepackage.New.
|
|
type Constructor func(Handler) (Handler, error)
|
|
|
|
// Chain is a chain for TCP handlers.
|
|
// Chain acts as a list of tcp.Handler constructors.
|
|
// Chain is effectively immutable:
|
|
// once created, it will always hold
|
|
// the same set of constructors in the same order.
|
|
type Chain struct {
|
|
constructors []Constructor
|
|
}
|
|
|
|
// NewChain creates a new TCP chain,
|
|
// memorizing the given list of TCP middleware constructors.
|
|
// New serves no other function,
|
|
// constructors are only called upon a call to Then().
|
|
func NewChain(constructors ...Constructor) Chain {
|
|
return Chain{constructors: constructors}
|
|
}
|
|
|
|
// Then adds an handler at the end of the chain.
|
|
func (c Chain) Then(h Handler) (Handler, error) {
|
|
if h == nil {
|
|
return nil, fmt.Errorf("cannot add a nil handler to the chain")
|
|
}
|
|
|
|
for i := range c.constructors {
|
|
handler, err := c.constructors[len(c.constructors)-1-i](h)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
h = handler
|
|
}
|
|
|
|
return h, nil
|
|
}
|
|
|
|
// Append extends a chain, adding the specified constructors
|
|
// as the last ones in the request flow.
|
|
//
|
|
// Append returns a new chain, leaving the original one untouched.
|
|
//
|
|
// stdChain := tcp.NewChain(m1, m2)
|
|
// extChain := stdChain.Append(m3, m4)
|
|
// // requests in stdChain go m1 -> m2
|
|
// // requests in extChain go m1 -> m2 -> m3 -> m4
|
|
func (c Chain) Append(constructors ...Constructor) Chain {
|
|
newCons := make([]Constructor, 0, len(c.constructors)+len(constructors))
|
|
newCons = append(newCons, c.constructors...)
|
|
newCons = append(newCons, constructors...)
|
|
|
|
return Chain{newCons}
|
|
}
|
|
|
|
// Extend extends a chain by adding the specified chain
|
|
// as the last one in the request flow.
|
|
//
|
|
// Extend returns a new chain, leaving the original one untouched.
|
|
//
|
|
// stdChain := tcp.NewChain(m1, m2)
|
|
// ext1Chain := tcp.NewChain(m3, m4)
|
|
// ext2Chain := stdChain.Extend(ext1Chain)
|
|
// // requests in stdChain go m1 -> m2
|
|
// // requests in ext1Chain go m3 -> m4
|
|
// // requests in ext2Chain go m1 -> m2 -> m3 -> m4
|
|
//
|
|
// Another example:
|
|
// aHtmlAfterNosurf := tcp.NewChain(m2)
|
|
// aHtml := tcp.NewChain(m1, func(h tcp.Handler) tcp.Handler {
|
|
// csrf := nosurf.New(h)
|
|
// csrf.SetFailureHandler(aHtmlAfterNosurf.ThenFunc(csrfFail))
|
|
// return csrf
|
|
// }).Extend(aHtmlAfterNosurf)
|
|
// // requests to aHtml hitting nosurfs success handler go m1 -> nosurf -> m2 -> target-handler
|
|
// // requests to aHtml hitting nosurfs failure handler go m1 -> nosurf -> m2 -> csrfFail
|
|
func (c Chain) Extend(chain Chain) Chain {
|
|
return c.Append(chain.constructors...)
|
|
}
|