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package stack
import "net/http"
type chainHandler func(*Context) http.Handler
type chainMiddleware func(*Context, http.Handler) http.Handler
type Chain struct {
mws []chainMiddleware
h chainHandler
}
func New(mws ...chainMiddleware) Chain {
return Chain{mws: mws}
}
func (c Chain) Append(mws ...chainMiddleware) Chain {
newMws := make([]chainMiddleware, len(c.mws)+len(mws))
copy(newMws[:len(c.mws)], c.mws)
copy(newMws[len(c.mws):], mws)
c.mws = newMws
return c
}
func (c Chain) Then(chf func(ctx *Context, w http.ResponseWriter, r *http.Request)) HandlerChain {
c.h = adaptContextHandlerFunc(chf)
return newHandlerChain(c)
}
func (c Chain) ThenHandler(h http.Handler) HandlerChain {
c.h = adaptHandler(h)
return newHandlerChain(c)
}
func (c Chain) ThenHandlerFunc(fn func(http.ResponseWriter, *http.Request)) HandlerChain {
c.h = adaptHandlerFunc(fn)
return newHandlerChain(c)
}
type HandlerChain struct {
context *Context
Chain
}
func newHandlerChain(c Chain) HandlerChain {
return HandlerChain{context: NewContext(), Chain: c}
}
func (hc HandlerChain) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Always take a copy of context (i.e. pointing to a brand new memory location)
ctx := hc.context.copy()
final := hc.h(ctx)
for i := len(hc.mws) - 1; i >= 0; i-- {
final = hc.mws[i](ctx, final)
}
final.ServeHTTP(w, r)
}
func Inject(hc HandlerChain, key string, val interface{}) HandlerChain {
hc.context = hc.context.copy().Put(key, val)
return hc
}
// Adapt third party middleware with the signature
// func(http.Handler) http.Handler into chainMiddleware
func Adapt(fn func(http.Handler) http.Handler) chainMiddleware {
return func(ctx *Context, h http.Handler) http.Handler {
return fn(h)
}
}
// Adapt http.Handler into a chainHandler
func adaptHandler(h http.Handler) chainHandler {
return func(ctx *Context) http.Handler {
return h
}
}
// Adapt a function with the signature
// func(http.ResponseWriter, *http.Request) into a chainHandler
func adaptHandlerFunc(fn func(w http.ResponseWriter, r *http.Request)) chainHandler {
return adaptHandler(http.HandlerFunc(fn))
}
// Adapt a function with the signature
// func(Context, http.ResponseWriter, *http.Request) into a chainHandler
func adaptContextHandlerFunc(fn func(ctx *Context, w http.ResponseWriter, r *http.Request)) chainHandler {
return func(ctx *Context) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fn(ctx, w, r)
})
}
}
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