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middleware.go
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middleware.go
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/*
* Copyright (C) 2023 Intergral GmbH
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package frontend
import "net/http"
// middleware.go contains types and code related to building http pipelines
// RoundTripperFunc is like http.HandlerFunc, but for RoundTripper
// chosen for pipeline building over queryrange.Handler b/c of how similar queryrange.Handler is to this existing interface.
type RoundTripperFunc func(*http.Request) (*http.Response, error)
// RoundTrip implememnts http.RoundTripper
func (fn RoundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error) {
return fn(req)
}
// Middleware is used to build pipelines of http.Roundtrippers
type Middleware interface {
Wrap(http.RoundTripper) http.RoundTripper
}
// MiddlewareFunc is like http.HandlerFunc, but for Middleware.
type MiddlewareFunc func(http.RoundTripper) http.RoundTripper
// Wrap implements Middleware.
func (q MiddlewareFunc) Wrap(h http.RoundTripper) http.RoundTripper {
return q(h)
}
// MergeMiddlewares takes a set of ordered middlewares and merges them into a pipeline
func MergeMiddlewares(middleware ...Middleware) Middleware {
return MiddlewareFunc(func(next http.RoundTripper) http.RoundTripper {
for i := len(middleware) - 1; i >= 0; i-- {
next = middleware[i].Wrap(next)
}
return next
})
}
type roundTripper struct {
handler http.RoundTripper
}
// NewRoundTripper takes an ordered set of middlewares and builds a http.RoundTripper
// around them
func NewRoundTripper(next http.RoundTripper, middlewares ...Middleware) http.RoundTripper {
return roundTripper{
handler: MergeMiddlewares(middlewares...).Wrap(next),
}
}
func (q roundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
return q.handler.RoundTrip(r)
}