Export Replacer and use concrete type instead of interface

The interface was only making things difficult; a concrete pointer is
probably best.

19 files changed, 128 insertions, 134 deletions

diff --git a/modules/caddyhttp/caddyauth/caddyauth.go b/modules/caddyhttp/caddyauth/caddyauth.go
index aefeec5..dc1dc99 100644
--- a/modules/caddyhttp/caddyauth/caddyauth.go
+++ b/modules/caddyhttp/caddyauth/caddyauth.go
@@ -76,7 +76,7 @@ func (a Authentication) ServeHTTP(w http.ResponseWriter, r *http.Request, next c
 		return caddyhttp.Error(http.StatusUnauthorized, fmt.Errorf("not authenticated"))
 	}
 
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	repl.Set("http.authentication.user.id", user.ID)
 
 	return next.ServeHTTP(w, r)
diff --git a/modules/caddyhttp/fileserver/browse.go b/modules/caddyhttp/fileserver/browse.go
index aa8372e..e5e137f 100644
--- a/modules/caddyhttp/fileserver/browse.go
+++ b/modules/caddyhttp/fileserver/browse.go
@@ -52,7 +52,7 @@ func (fsrv *FileServer) serveBrowse(dirPath string, w http.ResponseWriter, r *ht
 	}
 	defer dir.Close()
 
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// calling path.Clean here prevents weird breadcrumbs when URL paths are sketchy like /%2e%2e%2f
 	listing, err := fsrv.loadDirectoryContents(dir, path.Clean(r.URL.Path), repl)
@@ -87,7 +87,7 @@ func (fsrv *FileServer) serveBrowse(dirPath string, w http.ResponseWriter, r *ht
 	return nil
 }
 
-func (fsrv *FileServer) loadDirectoryContents(dir *os.File, urlPath string, repl caddy.Replacer) (browseListing, error) {
+func (fsrv *FileServer) loadDirectoryContents(dir *os.File, urlPath string, repl *caddy.Replacer) (browseListing, error) {
 	files, err := dir.Readdir(-1)
 	if err != nil {
 		return browseListing{}, err
diff --git a/modules/caddyhttp/fileserver/browselisting.go b/modules/caddyhttp/fileserver/browselisting.go
index b2349f8..9c7c4a2 100644
--- a/modules/caddyhttp/fileserver/browselisting.go
+++ b/modules/caddyhttp/fileserver/browselisting.go
@@ -27,7 +27,7 @@ import (
 	"github.com/dustin/go-humanize"
 )
 
-func (fsrv *FileServer) directoryListing(files []os.FileInfo, canGoUp bool, urlPath string, repl caddy.Replacer) browseListing {
+func (fsrv *FileServer) directoryListing(files []os.FileInfo, canGoUp bool, urlPath string, repl *caddy.Replacer) browseListing {
 	filesToHide := fsrv.transformHidePaths(repl)
 
 	var (
diff --git a/modules/caddyhttp/fileserver/matcher.go b/modules/caddyhttp/fileserver/matcher.go
index 5ca97f2..6c1e880 100644
--- a/modules/caddyhttp/fileserver/matcher.go
+++ b/modules/caddyhttp/fileserver/matcher.go
@@ -126,7 +126,7 @@ func (m MatchFile) Validate() error {
 //    - http.matchers.file.relative
 //    - http.matchers.file.absolute
 func (m MatchFile) Match(r *http.Request) bool {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	rel, abs, matched := m.selectFile(r)
 	if matched {
 		repl.Set("http.matchers.file.relative", rel)
@@ -140,7 +140,7 @@ func (m MatchFile) Match(r *http.Request) bool {
 // It returns the root-relative path to the matched file, the full
 // or absolute path, and whether a match was made.
 func (m MatchFile) selectFile(r *http.Request) (rel, abs string, matched bool) {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	root := repl.ReplaceAll(m.Root, ".")
 
diff --git a/modules/caddyhttp/fileserver/staticfiles.go b/modules/caddyhttp/fileserver/staticfiles.go
index f2722ba..d6cf4d6 100644
--- a/modules/caddyhttp/fileserver/staticfiles.go
+++ b/modules/caddyhttp/fileserver/staticfiles.go
@@ -106,7 +106,7 @@ func (fsrv *FileServer) Provision(ctx caddy.Context) error {
 }
 
 func (fsrv *FileServer) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	filesToHide := fsrv.transformHidePaths(repl)
 
@@ -293,7 +293,7 @@ func mapDirOpenError(originalErr error, name string) error {
 
 // transformHidePaths performs replacements for all the elements of
 // fsrv.Hide and returns a new list of the transformed values.
-func (fsrv *FileServer) transformHidePaths(repl caddy.Replacer) []string {
+func (fsrv *FileServer) transformHidePaths(repl *caddy.Replacer) []string {
 	hide := make([]string, len(fsrv.Hide))
 	for i := range fsrv.Hide {
 		hide[i] = repl.ReplaceAll(fsrv.Hide[i], "")
diff --git a/modules/caddyhttp/headers/headers.go b/modules/caddyhttp/headers/headers.go
index ad6c08b..8dec42c 100644
--- a/modules/caddyhttp/headers/headers.go
+++ b/modules/caddyhttp/headers/headers.go
@@ -88,7 +88,7 @@ func (h Handler) Validate() error {
 }
 
 func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	if h.Request != nil {
 		h.Request.ApplyToRequest(r)
@@ -182,7 +182,7 @@ type RespHeaderOps struct {
 }
 
 // ApplyTo applies ops to hdr using repl.
-func (ops HeaderOps) ApplyTo(hdr http.Header, repl caddy.Replacer) {
+func (ops HeaderOps) ApplyTo(hdr http.Header, repl *caddy.Replacer) {
 	// add
 	for fieldName, vals := range ops.Add {
 		fieldName = repl.ReplaceAll(fieldName, "")
@@ -249,7 +249,7 @@ func (ops HeaderOps) ApplyTo(hdr http.Header, repl caddy.Replacer) {
 // header which the standard library does not include with the
 // header map with all the others. This method mutates r.Host.
 func (ops HeaderOps) ApplyToRequest(r *http.Request) {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// capture the current Host header so we can
 	// reset to it when we're done
@@ -285,7 +285,7 @@ func (ops HeaderOps) ApplyToRequest(r *http.Request) {
 // operations until WriteHeader is called.
 type responseWriterWrapper struct {
 	*caddyhttp.ResponseWriterWrapper
-	replacer    caddy.Replacer
+	replacer    *caddy.Replacer
 	require     *caddyhttp.ResponseMatcher
 	headerOps   *HeaderOps
 	wroteHeader bool
diff --git a/modules/caddyhttp/matchers.go b/modules/caddyhttp/matchers.go
index 00f273e..170dbe7 100644
--- a/modules/caddyhttp/matchers.go
+++ b/modules/caddyhttp/matchers.go
@@ -118,7 +118,7 @@ func (m MatchHost) Match(r *http.Request) bool {
 		reqHost = strings.TrimSuffix(reqHost, "]")
 	}
 
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 outer:
 	for _, host := range m {
@@ -223,7 +223,7 @@ func (MatchPathRE) CaddyModule() caddy.ModuleInfo {
 
 // Match returns true if r matches m.
 func (m MatchPathRE) Match(r *http.Request) bool {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	return m.MatchRegexp.Match(r.URL.Path, repl)
 }
 
@@ -380,7 +380,7 @@ func (m *MatchHeaderRE) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 // Match returns true if r matches m.
 func (m MatchHeaderRE) Match(r *http.Request) bool {
 	for field, rm := range m {
-		repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+		repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 		match := rm.Match(r.Header.Get(field), repl)
 		if !match {
 			return false
@@ -652,10 +652,8 @@ func (mre *MatchRegexp) Validate() error {
 // Match returns true if input matches the compiled regular
 // expression in mre. It sets values on the replacer repl
 // associated with capture groups, using the given scope
-// (namespace). Capture groups stored to repl will take on
-// the name "http.matchers.<scope>.<mre.Name>.<N>" where
-// <N> is the name or number of the capture group.
-func (mre *MatchRegexp) Match(input string, repl caddy.Replacer) bool {
+// (namespace).
+func (mre *MatchRegexp) Match(input string, repl *caddy.Replacer) bool {
 	matches := mre.compiled.FindStringSubmatch(input)
 	if matches == nil {
 		return false
diff --git a/modules/caddyhttp/replacer.go b/modules/caddyhttp/replacer.go
index c8fae79..09837be 100644
--- a/modules/caddyhttp/replacer.go
+++ b/modules/caddyhttp/replacer.go
@@ -26,7 +26,7 @@ import (
 	"github.com/caddyserver/caddy/v2"
 )
 
-func addHTTPVarsToReplacer(repl caddy.Replacer, req *http.Request, w http.ResponseWriter) {
+func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.ResponseWriter) {
 	httpVars := func(key string) (string, bool) {
 		if req != nil {
 			// query string parameters
diff --git a/modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go b/modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go
index c0dda29..9a424b0 100644
--- a/modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go
+++ b/modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go
@@ -148,7 +148,7 @@ func (t Transport) RoundTrip(r *http.Request) (*http.Response, error) {
 
 // buildEnv returns a set of CGI environment variables for the request.
 func (t Transport) buildEnv(r *http.Request) (map[string]string, error) {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	var env map[string]string
 
diff --git a/modules/caddyhttp/reverseproxy/hosts.go b/modules/caddyhttp/reverseproxy/hosts.go
index e7c61fb..6e25c66 100644
--- a/modules/caddyhttp/reverseproxy/hosts.go
+++ b/modules/caddyhttp/reverseproxy/hosts.go
@@ -204,7 +204,7 @@ func (di DialInfo) String() string {
 
 // fillDialInfo returns a filled DialInfo for the given upstream, using
 // the given Replacer. Note that the returned value is not a pointer.
-func fillDialInfo(upstream *Upstream, repl caddy.Replacer) (DialInfo, error) {
+func fillDialInfo(upstream *Upstream, repl *caddy.Replacer) (DialInfo, error) {
 	dial := repl.ReplaceAll(upstream.Dial, "")
 	addr, err := caddy.ParseNetworkAddress(dial)
 	if err != nil {
diff --git a/modules/caddyhttp/reverseproxy/reverseproxy.go b/modules/caddyhttp/reverseproxy/reverseproxy.go
index 24389b2..238e86f 100644
--- a/modules/caddyhttp/reverseproxy/reverseproxy.go
+++ b/modules/caddyhttp/reverseproxy/reverseproxy.go
@@ -263,7 +263,7 @@ func (h *Handler) Cleanup() error {
 }
 
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// if enabled, buffer client request;
 	// this should only be enabled if the
@@ -507,7 +507,7 @@ func (h *Handler) reverseProxy(rw http.ResponseWriter, req *http.Request, di Dia
 	if h.Headers != nil && h.Headers.Response != nil {
 		if h.Headers.Response.Require == nil ||
 			h.Headers.Response.Require.Match(res.StatusCode, rw.Header()) {
-			repl := req.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+			repl := req.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 			h.Headers.Response.ApplyTo(rw.Header(), repl)
 		}
 	}
diff --git a/modules/caddyhttp/rewrite/rewrite.go b/modules/caddyhttp/rewrite/rewrite.go
index 03c54b1..b875adb 100644
--- a/modules/caddyhttp/rewrite/rewrite.go
+++ b/modules/caddyhttp/rewrite/rewrite.go
@@ -91,7 +91,7 @@ func (rewr Rewrite) Validate() error {
 }
 
 func (rewr Rewrite) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	logger := rewr.logger.With(
 		zap.Object("request", caddyhttp.LoggableHTTPRequest{Request: r}),
@@ -124,7 +124,7 @@ func (rewr Rewrite) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddy
 // rewrite performs the rewrites on r using repl, which
 // should have been obtained from r, but is passed in for
 // efficiency. It returns true if any changes were made to r.
-func (rewr Rewrite) rewrite(r *http.Request, repl caddy.Replacer, logger *zap.Logger) bool {
+func (rewr Rewrite) rewrite(r *http.Request, repl *caddy.Replacer, logger *zap.Logger) bool {
 	oldMethod := r.Method
 	oldURI := r.RequestURI
 
@@ -209,7 +209,7 @@ type replacer struct {
 }
 
 // do performs the replacement on r and returns true if any changes were made.
-func (rep replacer) do(r *http.Request, repl caddy.Replacer) bool {
+func (rep replacer) do(r *http.Request, repl *caddy.Replacer) bool {
 	if rep.Find == "" || rep.Replace == "" {
 		return false
 	}
diff --git a/modules/caddyhttp/server.go b/modules/caddyhttp/server.go
index 60ce07e..0c30139 100644
--- a/modules/caddyhttp/server.go
+++ b/modules/caddyhttp/server.go
@@ -451,7 +451,7 @@ func (*HTTPErrorConfig) WithError(r *http.Request, err error) *http.Request {
 	r = r.WithContext(c)
 
 	// add error values to the replacer
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	repl.Set("http.error", err.Error())
 	if handlerErr, ok := err.(HandlerError); ok {
 		repl.Set("http.error.status_code", strconv.Itoa(handlerErr.StatusCode))
diff --git a/modules/caddyhttp/staticerror.go b/modules/caddyhttp/staticerror.go
index 0ddebfe..306c3eb 100644
--- a/modules/caddyhttp/staticerror.go
+++ b/modules/caddyhttp/staticerror.go
@@ -51,7 +51,7 @@ func (StaticError) CaddyModule() caddy.ModuleInfo {
 }
 
 func (e StaticError) ServeHTTP(w http.ResponseWriter, r *http.Request, _ Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	statusCode := http.StatusInternalServerError
 	if codeStr := e.StatusCode.String(); codeStr != "" {
diff --git a/modules/caddyhttp/staticresp.go b/modules/caddyhttp/staticresp.go
index cc294d5..0ca2f43 100644
--- a/modules/caddyhttp/staticresp.go
+++ b/modules/caddyhttp/staticresp.go
@@ -86,7 +86,7 @@ func (s *StaticResponse) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 }
 
 func (s StaticResponse) ServeHTTP(w http.ResponseWriter, r *http.Request, _ Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// close the connection after responding
 	r.Close = s.Close
diff --git a/modules/caddyhttp/templates/templates.go b/modules/caddyhttp/templates/templates.go
index 6586302..d01b447 100644
--- a/modules/caddyhttp/templates/templates.go
+++ b/modules/caddyhttp/templates/templates.go
@@ -122,7 +122,7 @@ func (t *Templates) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddy
 func (t *Templates) executeTemplate(rr caddyhttp.ResponseRecorder, r *http.Request) error {
 	var fs http.FileSystem
 	if t.FileRoot != "" {
-		repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+		repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 		fs = http.Dir(repl.ReplaceAll(t.FileRoot, "."))
 	}
 
diff --git a/modules/caddyhttp/vars.go b/modules/caddyhttp/vars.go
index 6299dcf..cd0d8d0 100644
--- a/modules/caddyhttp/vars.go
+++ b/modules/caddyhttp/vars.go
@@ -40,7 +40,7 @@ func (VarsMiddleware) CaddyModule() caddy.ModuleInfo {
 
 func (t VarsMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request, next Handler) error {
 	vars := r.Context().Value(VarsCtxKey).(map[string]interface{})
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	for k, v := range t {
 		keyExpanded := repl.ReplaceAll(k, "")
 		valExpanded := repl.ReplaceAll(v, "")
@@ -64,7 +64,7 @@ func (VarsMatcher) CaddyModule() caddy.ModuleInfo {
 // Match matches a request based on variables in the context.
 func (m VarsMatcher) Match(r *http.Request) bool {
 	vars := r.Context().Value(VarsCtxKey).(map[string]string)
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	for k, v := range m {
 		keyExpanded := repl.ReplaceAll(k, "")
 		valExpanded := repl.ReplaceAll(v, "")
diff --git a/replacer.go b/replacer.go
index cabe089..8ed6d24 100644
--- a/replacer.go
+++ b/replacer.go
@@ -23,20 +23,9 @@ import (
 	"time"
 )
 
-// Replacer can replace values in strings.
-type Replacer interface {
-	Set(variable, value string)
-	Delete(variable string)
-	Map(ReplacerFunc)
-	ReplaceAll(input, empty string) string
-	ReplaceKnown(input, empty string) string
-	ReplaceOrErr(input string, errOnEmpty, errOnUnknown bool) (string, error)
-	ReplaceFunc(input string, f ReplacementFunc) (string, error)
-}
-
 // NewReplacer returns a new Replacer.
-func NewReplacer() Replacer {
-	rep := &replacer{
+func NewReplacer() *Replacer {
+	rep := &Replacer{
 		static: make(map[string]string),
 	}
 	rep.providers = []ReplacerFunc{
@@ -46,30 +35,44 @@ func NewReplacer() Replacer {
 	return rep
 }
 
-type replacer struct {
+// Replacer can replace values in strings.
+// A default/empty Replacer is not valid;
+// use NewReplacer to make one.
+type Replacer struct {
 	providers []ReplacerFunc
 	static    map[string]string
 }
 
 // Map adds mapFunc to the list of value providers.
 // mapFunc will be executed only at replace-time.
-func (r *replacer) Map(mapFunc ReplacerFunc) {
+func (r *Replacer) Map(mapFunc ReplacerFunc) {
 	r.providers = append(r.providers, mapFunc)
 }
 
 // Set sets a custom variable to a static value.
-func (r *replacer) Set(variable, value string) {
+func (r *Replacer) Set(variable, value string) {
 	r.static[variable] = value
 }
 
+// Get gets a value from the replacer. It returns
+// the value and whether the variable was known.
+func (r *Replacer) Get(variable string) (string, bool) {
+	for _, mapFunc := range r.providers {
+		if val, ok := mapFunc(variable); ok {
+			return val, true
+		}
+	}
+	return "", false
+}
+
 // Delete removes a variable with a static value
 // that was created using Set.
-func (r *replacer) Delete(variable string) {
+func (r *Replacer) Delete(variable string) {
 	delete(r.static, variable)
 }
 
 // fromStatic provides values from r.static.
-func (r *replacer) fromStatic(key string) (val string, ok bool) {
+func (r *Replacer) fromStatic(key string) (val string, ok bool) {
 	val, ok = r.static[key]
 	return
 }
@@ -77,14 +80,14 @@ func (r *replacer) fromStatic(key string) (val string, ok bool) {
 // ReplaceOrErr is like ReplaceAll, but any placeholders
 // that are empty or not recognized will cause an error to
 // be returned.
-func (r *replacer) ReplaceOrErr(input string, errOnEmpty, errOnUnknown bool) (string, error) {
+func (r *Replacer) ReplaceOrErr(input string, errOnEmpty, errOnUnknown bool) (string, error) {
 	return r.replace(input, "", false, errOnEmpty, errOnUnknown, nil)
 }
 
 // ReplaceKnown is like ReplaceAll but only replaces
 // placeholders that are known (recognized). Unrecognized
 // placeholders will remain in the output.
-func (r *replacer) ReplaceKnown(input, empty string) string {
+func (r *Replacer) ReplaceKnown(input, empty string) string {
 	out, _ := r.replace(input, empty, false, false, false, nil)
 	return out
 }
@@ -93,7 +96,7 @@ func (r *replacer) ReplaceKnown(input, empty string) string {
 // their values. All placeholders are replaced in the output
 // whether they are recognized or not. Values that are empty
 // string will be substituted with empty.
-func (r *replacer) ReplaceAll(input, empty string) string {
+func (r *Replacer) ReplaceAll(input, empty string) string {
 	out, _ := r.replace(input, empty, true, false, false, nil)
 	return out
 }
@@ -102,11 +105,11 @@ func (r *replacer) ReplaceAll(input, empty string) string {
 // their values. All placeholders are replaced in the output
 // whether they are recognized or not. Values that are empty
 // string will be substituted with empty.
-func (r *replacer) ReplaceFunc(input string, f ReplacementFunc) (string, error) {
+func (r *Replacer) ReplaceFunc(input string, f ReplacementFunc) (string, error) {
 	return r.replace(input, "", true, false, false, f)
 }
 
-func (r *replacer) replace(input, empty string,
+func (r *Replacer) replace(input, empty string,
 	treatUnknownAsEmpty, errOnEmpty, errOnUnknown bool,
 	f ReplacementFunc) (string, error) {
 	if !strings.Contains(input, string(phOpen)) {
@@ -138,48 +141,45 @@ func (r *replacer) replace(input, empty string,
 		// trim opening bracket
 		key := input[i+1 : end]
 
-		// try to get a value for this key,
-		// handle empty values accordingly
-		var found bool
-		for _, mapFunc := range r.providers {
-			if val, ok := mapFunc(key); ok {
-				found = true
-				if f != nil {
-					var err error
-					val, err = f(key, val)
-					if err != nil {
-						return "", err
-					}
-				}
-				if val == "" {
-					if errOnEmpty {
-						return "", fmt.Errorf("evaluated placeholder %s%s%s is empty",
-							string(phOpen), key, string(phClose))
-					} else if empty != "" {
-						sb.WriteString(empty)
-					}
-				} else {
-					sb.WriteString(val)
-				}
-				break
-			}
-		}
+		// try to get a value for this key, handle empty values accordingly
+		val, found := r.Get(key)
 		if !found {
-			// placeholder is unknown (unrecognized), handle accordingly
-			switch {
-			case errOnUnknown:
+			// placeholder is unknown (unrecognized); handle accordingly
+			if errOnUnknown {
 				return "", fmt.Errorf("unrecognized placeholder %s%s%s",
 					string(phOpen), key, string(phClose))
-			case treatUnknownAsEmpty:
+			} else if treatUnknownAsEmpty {
 				if empty != "" {
 					sb.WriteString(empty)
 				}
-			default:
+			} else {
 				lastWriteCursor = i
 				continue
 			}
 		}
 
+		// apply any transformations
+		if f != nil {
+			var err error
+			val, err = f(key, val)
+			if err != nil {
+				return "", err
+			}
+		}
+
+		// write the value; if it's empty, either return
+		// an error or write a default value
+		if val == "" {
+			if errOnEmpty {
+				return "", fmt.Errorf("evaluated placeholder %s%s%s is empty",
+					string(phOpen), key, string(phClose))
+			} else if empty != "" {
+				sb.WriteString(empty)
+			}
+		} else {
+			sb.WriteString(val)
+		}
+
 		// advance cursor to end of placeholder
 		i = end
 		lastWriteCursor = i + 1
diff --git a/replacer_test.go b/replacer_test.go
index 88e83f5..42e9ee1 100644
--- a/replacer_test.go
+++ b/replacer_test.go
@@ -132,7 +132,7 @@ func TestReplacerSet(t *testing.T) {
 }
 
 func TestReplacerReplaceKnown(t *testing.T) {
-	rep := replacer{
+	rep := Replacer{
 		providers: []ReplacerFunc{
 			// split our possible vars to two functions (to test if both functions are called)
 			func(key string) (val string, ok bool) {
@@ -204,7 +204,7 @@ func TestReplacerReplaceKnown(t *testing.T) {
 }
 
 func TestReplacerDelete(t *testing.T) {
-	rep := replacer{
+	rep := Replacer{
 		static: map[string]string{
 			"key1": "val1",
 			"key2": "val2",
@@ -264,59 +264,55 @@ func TestReplacerMap(t *testing.T) {
 }
 
 func TestReplacerNew(t *testing.T) {
-	var tc = NewReplacer()
+	rep := NewReplacer()
 
-	rep, ok := tc.(*replacer)
-	if ok {
-		if len(rep.providers) != 2 {
-			t.Errorf("Expected providers length '%v' got length '%v'", 2, len(rep.providers))
-		} else {
-			// test if default global replacements are added  as the first provider
-			hostname, _ := os.Hostname()
-			os.Setenv("CADDY_REPLACER_TEST", "envtest")
-			defer os.Setenv("CADDY_REPLACER_TEST", "")
+	if len(rep.providers) != 2 {
+		t.Errorf("Expected providers length '%v' got length '%v'", 2, len(rep.providers))
+	} else {
+		// test if default global replacements are added  as the first provider
+		hostname, _ := os.Hostname()
+		os.Setenv("CADDY_REPLACER_TEST", "envtest")
+		defer os.Setenv("CADDY_REPLACER_TEST", "")
 
-			for _, tc := range []struct {
-				variable string
-				value    string
-			}{
-				{
-					variable: "system.hostname",
-					value:    hostname,
-				},
-				{
-					variable: "system.slash",
-					value:    string(filepath.Separator),
-				},
-				{
-					variable: "system.os",
-					value:    runtime.GOOS,
-				},
-				{
-					variable: "system.arch",
-					value:    runtime.GOARCH,
-				},
-				{
-					variable: "env.CADDY_REPLACER_TEST",
-					value:    "envtest",
-				},
-			} {
-				if val, ok := rep.providers[0](tc.variable); ok {
-					if val != tc.value {
-						t.Errorf("Expected value '%s' for key '%s' got '%s'", tc.value, tc.variable, val)
-					}
-				} else {
-					t.Errorf("Expected key '%s' to be recognized by first provider", tc.variable)
+		for _, tc := range []struct {
+			variable string
+			value    string
+		}{
+			{
+				variable: "system.hostname",
+				value:    hostname,
+			},
+			{
+				variable: "system.slash",
+				value:    string(filepath.Separator),
+			},
+			{
+				variable: "system.os",
+				value:    runtime.GOOS,
+			},
+			{
+				variable: "system.arch",
+				value:    runtime.GOARCH,
+			},
+			{
+				variable: "env.CADDY_REPLACER_TEST",
+				value:    "envtest",
+			},
+		} {
+			if val, ok := rep.providers[0](tc.variable); ok {
+				if val != tc.value {
+					t.Errorf("Expected value '%s' for key '%s' got '%s'", tc.value, tc.variable, val)
 				}
+			} else {
+				t.Errorf("Expected key '%s' to be recognized by first provider", tc.variable)
 			}
 		}
-	} else {
-		t.Errorf("Expected type of replacer %T got %T ", &replacer{}, tc)
 	}
+
 }
 
-func testReplacer() replacer {
-	return replacer{
+func testReplacer() Replacer {
+	return Replacer{
 		providers: make([]ReplacerFunc, 0),
 		static:    make(map[string]string),
 	}