From 77c172b823b64ebface655681ab0749b9d2f7081 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ra=C3=BAl=20Benencia?= <raul@thousandeyes.com>
Date: Fri, 13 Apr 2018 16:30:31 -0700
Subject: First public commit

---
 vendor/github.com/justinas/alice/chain.go | 112 ++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 vendor/github.com/justinas/alice/chain.go

(limited to 'vendor/github.com/justinas/alice/chain.go')

diff --git a/vendor/github.com/justinas/alice/chain.go b/vendor/github.com/justinas/alice/chain.go
new file mode 100644
index 0000000..da0e2b5
--- /dev/null
+++ b/vendor/github.com/justinas/alice/chain.go
@@ -0,0 +1,112 @@
+// Package alice provides a convenient way to chain http handlers.
+package alice
+
+import "net/http"
+
+// A constructor for a piece of middleware.
+// Some middleware use this constructor out of the box,
+// so in most cases you can just pass somepackage.New
+type Constructor func(http.Handler) http.Handler
+
+// Chain acts as a list of http.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
+}
+
+// New creates a new chain,
+// memorizing the given list of middleware constructors.
+// New serves no other function,
+// constructors are only called upon a call to Then().
+func New(constructors ...Constructor) Chain {
+	return Chain{append(([]Constructor)(nil), constructors...)}
+}
+
+// Then chains the middleware and returns the final http.Handler.
+//     New(m1, m2, m3).Then(h)
+// is equivalent to:
+//     m1(m2(m3(h)))
+// When the request comes in, it will be passed to m1, then m2, then m3
+// and finally, the given handler
+// (assuming every middleware calls the following one).
+//
+// A chain can be safely reused by calling Then() several times.
+//     stdStack := alice.New(ratelimitHandler, csrfHandler)
+//     indexPipe = stdStack.Then(indexHandler)
+//     authPipe = stdStack.Then(authHandler)
+// Note that constructors are called on every call to Then()
+// and thus several instances of the same middleware will be created
+// when a chain is reused in this way.
+// For proper middleware, this should cause no problems.
+//
+// Then() treats nil as http.DefaultServeMux.
+func (c Chain) Then(h http.Handler) http.Handler {
+	if h == nil {
+		h = http.DefaultServeMux
+	}
+
+	for i := range c.constructors {
+		h = c.constructors[len(c.constructors)-1-i](h)
+	}
+
+	return h
+}
+
+// ThenFunc works identically to Then, but takes
+// a HandlerFunc instead of a Handler.
+//
+// The following two statements are equivalent:
+//     c.Then(http.HandlerFunc(fn))
+//     c.ThenFunc(fn)
+//
+// ThenFunc provides all the guarantees of Then.
+func (c Chain) ThenFunc(fn http.HandlerFunc) http.Handler {
+	if fn == nil {
+		return c.Then(nil)
+	}
+	return c.Then(fn)
+}
+
+// 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 := alice.New(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 := alice.New(m1, m2)
+//     ext1Chain := alice.New(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 := alice.New(m2)
+// 	aHtml := alice.New(m1, func(h http.Handler) http.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...)
+}
-- 
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