Refactor Caddyfile adapter and module registration

Use piles from which to draw config values.

Module values can return their name, so now we can do two-way mapping
from value to name and name to value; whereas before we could only map
name to value. This was problematic with the Caddyfile adapter since
it receives values and needs to know the name to put in the config.

2 files changed, 45 insertions, 41 deletions

diff --git a/modules/caddyhttp/headers/caddyfile.go b/modules/caddyhttp/headers/caddyfile.go
index 8d320e5..5eaf064 100644
--- a/modules/caddyhttp/headers/caddyfile.go
+++ b/modules/caddyhttp/headers/caddyfile.go
@@ -18,11 +18,15 @@ import (
 	"net/http"
 	"strings"
 
-	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
+	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
 )
 
-// UnmarshalCaddyfile sets up the handler from Caddyfile tokens. Syntax:
+func init() {
+	httpcaddyfile.RegisterHandlerDirective("headers", parseCaddyfile)
+}
+
+// parseCaddyfile sets up the handler from Caddyfile tokens. Syntax:
 //
 //     headers [<matcher>] [[+|-]<field> <value>] {
 //         [+][<field>] [<value>]
@@ -31,62 +35,57 @@ import (
 //
 // Either a block can be opened or a single header field can be configured
 // in the first line, but not both in the same directive.
-func (h *Headers) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
-	for d.Next() {
+func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error) {
+	hdr := new(Headers)
+	for h.Next() {
 		// first see if headers are in the initial line
 		var hasArgs bool
-		if d.NextArg() {
+		if h.NextArg() {
 			hasArgs = true
-			field := d.Val()
-			d.NextArg()
-			value := d.Val()
-			h.processCaddyfileLine(field, value)
+			field := h.Val()
+			h.NextArg()
+			value := h.Val()
+			processCaddyfileLine(hdr, field, value)
 		}
 
 		// if not, they should be in a block
-		for d.NextBlock() {
+		for h.NextBlock() {
 			if hasArgs {
-				return d.Err("cannot specify headers in both arguments and block")
+				return nil, h.Err("cannot specify headers in both arguments and block")
 			}
-			field := d.Val()
+			field := h.Val()
 			var value string
-			if d.NextArg() {
-				value = d.Val()
+			if h.NextArg() {
+				value = h.Val()
 			}
-			h.processCaddyfileLine(field, value)
+			processCaddyfileLine(hdr, field, value)
 		}
 	}
-	return nil
+	return hdr, nil
 }
 
-func (h *Headers) processCaddyfileLine(field, value string) {
+func processCaddyfileLine(hdr *Headers, field, value string) {
 	if strings.HasPrefix(field, "+") {
-		if h.Response == nil {
-			h.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
+		if hdr.Response == nil {
+			hdr.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
 		}
-		if h.Response.Add == nil {
-			h.Response.Add = make(http.Header)
+		if hdr.Response.Add == nil {
+			hdr.Response.Add = make(http.Header)
 		}
-		h.Response.Add.Set(field[1:], value)
+		hdr.Response.Add.Set(field[1:], value)
 	} else if strings.HasPrefix(field, "-") {
-		if h.Response == nil {
-			h.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
+		if hdr.Response == nil {
+			hdr.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
 		}
-		h.Response.Delete = append(h.Response.Delete, field[1:])
-		h.Response.Deferred = true
+		hdr.Response.Delete = append(hdr.Response.Delete, field[1:])
+		hdr.Response.Deferred = true
 	} else {
-		if h.Response == nil {
-			h.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
+		if hdr.Response == nil {
+			hdr.Response = &RespHeaderOps{HeaderOps: new(HeaderOps)}
 		}
-		if h.Response.Set == nil {
-			h.Response.Set = make(http.Header)
+		if hdr.Response.Set == nil {
+			hdr.Response.Set = make(http.Header)
 		}
-		h.Response.Set.Set(field, value)
+		hdr.Response.Set.Set(field, value)
 	}
 }
-
-// Bucket returns the HTTP Caddyfile handler bucket number.
-func (h Headers) Bucket() int { return 3 }
-
-// Interface guard
-var _ httpcaddyfile.HandlerDirective = (*Headers)(nil)
diff --git a/modules/caddyhttp/headers/headers.go b/modules/caddyhttp/headers/headers.go
index 8f4976a..e740004 100644
--- a/modules/caddyhttp/headers/headers.go
+++ b/modules/caddyhttp/headers/headers.go
@@ -23,10 +23,7 @@ import (
 )
 
 func init() {
-	caddy.RegisterModule(caddy.Module{
-		Name: "http.handlers.headers",
-		New:  func() interface{} { return new(Headers) },
-	})
+	caddy.RegisterModule(Headers{})
 }
 
 // Headers is a middleware which can mutate HTTP headers.
@@ -35,6 +32,14 @@ type Headers struct {
 	Response *RespHeaderOps `json:"response,omitempty"`
 }
 
+// CaddyModule returns the Caddy module information.
+func (Headers) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		Name: "http.handlers.headers",
+		New:  func() caddy.Module { return new(Headers) },
+	}
+}
+
 // HeaderOps defines some operations to
 // perform on HTTP headers.
 type HeaderOps struct {