encode,staticfiles: Content negotiation, precompressed files (#4045)

* encode: implement prefer setting

* encode: minimum_length configurable via caddyfile

* encode: configurable content-types which to encode

* file_server: support precompressed files

* encode: use ReponseMatcher for conditional encoding of content

* linting error & documentation of encode.PrecompressedOrder

* encode: allow just one response matcher

also change the namespace of the encoders back, I accidently changed to precompressed >.>
default matchers include a *  to match to any charset, that may be appended

* rounding of the PR

* added integration tests for new caddyfile directives
* improved various doc strings (punctuation and typos)
* added json tag for file_server precompress order and encode matcher

* file_server: add vary header, remove accept-ranges when serving precompressed files

* encode: move Suffix implementation to precompressed modules

3 files changed, 114 insertions, 0 deletions

diff --git a/caddytest/integration/caddyfile_adapt/encode_options.txt b/caddytest/integration/caddyfile_adapt/encode_options.txt
new file mode 100644
index 0000000..a43c7e0
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/encode_options.txt
@@ -0,0 +1,66 @@
+:80
+
+encode gzip zstd {
+	minimum_length 256
+	prefer zstd gzip
+	match {
+		status 2xx 4xx 500
+		header Content-Type text/*
+		header Content-Type application/json*
+		header Content-Type application/javascript*
+		header Content-Type application/xhtml+xml*
+		header Content-Type application/atom+xml*
+		header Content-Type application/rss+xml*
+		header Content-Type image/svg+xml*
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":80"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"encodings": {
+										"gzip": {},
+										"zstd": {}
+									},
+									"handler": "encode",
+									"match": {
+										"headers": {
+											"Content-Type": [
+												"text/*",
+												"application/json*",
+												"application/javascript*",
+												"application/xhtml+xml*",
+												"application/atom+xml*",
+												"application/rss+xml*",
+												"image/svg+xml*"
+											]
+										},
+										"status_code": [
+											2,
+											4,
+											500
+										]
+									},
+									"minimum_length": 256,
+									"prefer": [
+										"zstd",
+										"gzip"
+									]
+								}
+							]
+						}
+					]
+				}
+			}
+		}
+	}
+}
diff --git a/caddytest/integration/caddyfile_adapt/file_server_precompressed.txt b/caddytest/integration/caddyfile_adapt/file_server_precompressed.txt
new file mode 100644
index 0000000..ac7d7ed
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/file_server_precompressed.txt
@@ -0,0 +1,41 @@
+:80
+
+file_server {
+	precompressed zstd br gzip
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":80"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "file_server",
+									"hide": [
+										"./Caddyfile"
+									],
+									"precompressed": {
+										"br": {},
+										"gzip": {},
+										"zstd": {}
+									},
+									"precompressed_order": [
+										"zstd",
+										"br",
+										"gzip"
+									]
+								}
+							]
+						}
+					]
+				}
+			}
+		}
+	}
+}
diff --git a/caddytest/integration/caddyfile_adapt_test.go b/caddytest/integration/caddyfile_adapt_test.go
index 8794fe9..e109899 100644
--- a/caddytest/integration/caddyfile_adapt_test.go
+++ b/caddytest/integration/caddyfile_adapt_test.go
@@ -1,7 +1,10 @@
 package integration
 
 import (
+	jsonMod "encoding/json"
+	"fmt"
 	"io/ioutil"
+	"path/filepath"
 	"regexp"
 	"strings"
 	"testing"
@@ -39,6 +42,10 @@ func TestCaddyfileAdaptToJSON(t *testing.T) {
 		// replace windows newlines in the json with unix newlines
 		json = winNewlines.ReplaceAllString(json, "\n")
 
+		// replace os-specific default path for file_server's hide field
+		replacePath, _ := jsonMod.Marshal(fmt.Sprint(".", string(filepath.Separator), "Caddyfile"))
+		json = strings.ReplaceAll(json, `"./Caddyfile"`, string(replacePath))
+
 		// run the test
 		ok := caddytest.CompareAdapt(t, filename, caddyfile, "caddyfile", json)
 		if !ok {