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package reqctx
import (
"context"
"net/http"
"github.com/anacrolix/missinggo/futures"
)
var lazyValuesContextKey = new(byte)
func WithLazyMiddleware() func(http.Handler) http.Handler {
return func(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
r = WithLazy(r)
h.ServeHTTP(w, r)
})
}
}
func WithLazy(r *http.Request) *http.Request {
if r.Context().Value(lazyValuesContextKey) == nil {
r = r.WithContext(context.WithValue(r.Context(), lazyValuesContextKey, &LazyValues{r: r}))
}
return r
}
func GetLazyValues(ctx context.Context) *LazyValues {
return ctx.Value(lazyValuesContextKey).(*LazyValues)
}
type LazyValues struct {
values map[interface{}]*futures.F
r *http.Request
}
func (me *LazyValues) Get(val *lazyValue) *futures.F {
f := me.values[val.key]
if f != nil {
return f
}
f = futures.Start(func() (interface{}, error) {
return val.get(me.r)
})
if me.values == nil {
me.values = make(map[interface{}]*futures.F)
}
me.values[val.key] = f
return f
}
func NewLazyValue(get func(r *http.Request) (interface{}, error)) *lazyValue {
val := &lazyValue{
get: get,
}
val.key = val
return val
}
type lazyValue struct {
key interface{}
get func(r *http.Request) (interface{}, error)
}
func (me *lazyValue) Get(r *http.Request) *futures.F {
return me.GetContext(r.Context())
}
func (me *lazyValue) GetContext(ctx context.Context) *futures.F {
return GetLazyValues(ctx).Get(me)
}
func (me *lazyValue) Prefetch(r *http.Request) {
me.Get(r)
}
func (me *lazyValue) PrefetchMiddleware(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
me.Prefetch(r)
h.ServeHTTP(w, r)
})
}
|
