1 files changed, 89 insertions, 0 deletions
diff --git a/core/directives.go b/core/directives.go
new file mode 100644
index 000000000..96f4d910c
--- /dev/null
+++ b/core/directives.go
@@ -0,0 +1,89 @@
+package core
+
+import (
+	"github.com/miekg/coredns/core/https"
+	"github.com/miekg/coredns/core/parse"
+	"github.com/miekg/coredns/core/setup"
+	"github.com/miekg/coredns/middleware"
+)
+
+func init() {
+	// The parse package must know which directives
+	// are valid, but it must not import the setup
+	// or config package. To solve this problem, we
+	// fill up this map in our init function here.
+	// The parse package does not need to know the
+	// ordering of the directives.
+	for _, dir := range directiveOrder {
+		parse.ValidDirectives[dir.name] = struct{}{}
+	}
+}
+
+// Directives are registered in the order they should be
+// executed. Middleware (directives that inject a handler)
+// are executed in the order A-B-C-*-C-B-A, assuming
+// they all call the Next handler in the chain.
+//
+// Ordering is VERY important. Every middleware will
+// feel the effects of all other middleware below
+// (after) them during a request, but they must not
+// care what middleware above them are doing.
+//
+// For example, log needs to know the status code and
+// exactly how many bytes were written to the client,
+// which every other middleware can affect, so it gets
+// registered first. The errors middleware does not
+// care if gzip or log modifies its response, so it
+// gets registered below them. Gzip, on the other hand,
+// DOES care what errors does to the response since it
+// must compress every output to the client, even error
+// pages, so it must be registered before the errors
+// middleware and any others that would write to the
+// response.
+var directiveOrder = []directive{
+	// Essential directives that initialize vital configuration settings
+	{"root", setup.Root},
+	{"bind", setup.BindHost},
+	{"tls", https.Setup},
+
+	// Other directives that don't create HTTP handlers
+	{"startup", setup.Startup},
+	{"shutdown", setup.Shutdown},
+
+	// Directives that inject handlers (middleware)
+	{"prometheus", setup.Prometheus},
+	{"rewrite", setup.Rewrite},
+	{"file", setup.File},
+	{"reflect", setup.Reflect},
+	{"log", setup.Log},
+	{"errors", setup.Errors},
+	{"proxy", setup.Proxy},
+}
+
+// RegisterDirective adds the given directive to caddy's list of directives.
+// Pass the name of a directive you want it to be placed after,
+// otherwise it will be placed at the bottom of the stack.
+func RegisterDirective(name string, setup SetupFunc, after string) {
+	dir := directive{name: name, setup: setup}
+	idx := len(directiveOrder)
+	for i := range directiveOrder {
+		if directiveOrder[i].name == after {
+			idx = i + 1
+			break
+		}
+	}
+	newDirectives := append(directiveOrder[:idx], append([]directive{dir}, directiveOrder[idx:]...)...)
+	directiveOrder = newDirectives
+	parse.ValidDirectives[name] = struct{}{}
+}
+
+// directive ties together a directive name with its setup function.
+type directive struct {
+	name  string
+	setup SetupFunc
+}
+
+// SetupFunc takes a controller and may optionally return a middleware.
+// If the resulting middleware is not nil, it will be chained into
+// the HTTP handlers in the order specified in this package.
+type SetupFunc func(c *setup.Controller) (middleware.Middleware, error)