vendor dependencies with dep

vendor/github.com/go-chi/chi/middleware/compress.go

@@ -0,0 +1,212 @@
+package middleware
+
+import (
+	"bufio"
+	"compress/flate"
+	"compress/gzip"
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+)
+
+type encoding int
+
+const (
+	encodingNone encoding = iota
+	encodingGzip
+	encodingDeflate
+)
+
+var defaultContentTypes = map[string]struct{}{
+	"text/html":                struct{}{},
+	"text/css":                 struct{}{},
+	"text/plain":               struct{}{},
+	"text/javascript":          struct{}{},
+	"application/javascript":   struct{}{},
+	"application/x-javascript": struct{}{},
+	"application/json":         struct{}{},
+	"application/atom+xml":     struct{}{},
+	"application/rss+xml":      struct{}{},
+}
+
+// DefaultCompress is a middleware that compresses response
+// body of predefined content types to a data format based
+// on Accept-Encoding request header. It uses a default
+// compression level.
+func DefaultCompress(next http.Handler) http.Handler {
+	return Compress(flate.DefaultCompression)(next)
+}
+
+// Compress is a middleware that compresses response
+// body of a given content types to a data format based
+// on Accept-Encoding request header. It uses a given
+// compression level.
+func Compress(level int, types ...string) func(next http.Handler) http.Handler {
+	contentTypes := defaultContentTypes
+	if len(types) > 0 {
+		contentTypes = make(map[string]struct{}, len(types))
+		for _, t := range types {
+			contentTypes[t] = struct{}{}
+		}
+	}
+
+	return func(next http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			mcw := &maybeCompressResponseWriter{
+				ResponseWriter: w,
+				w:              w,
+				contentTypes:   contentTypes,
+				encoding:       selectEncoding(r.Header),
+				level:          level,
+			}
+			defer mcw.Close()
+
+			next.ServeHTTP(mcw, r)
+		}
+
+		return http.HandlerFunc(fn)
+	}
+}
+
+func selectEncoding(h http.Header) encoding {
+	enc := h.Get("Accept-Encoding")
+
+	switch {
+	// TODO:
+	// case "br":    // Brotli, experimental. Firefox 2016, to-be-in Chromium.
+	// case "lzma":  // Opera.
+	// case "sdch":  // Chrome, Android. Gzip output + dictionary header.
+
+	case strings.Contains(enc, "gzip"):
+		// TODO: Exception for old MSIE browsers that can't handle non-HTML?
+		// https://zoompf.com/blog/2012/02/lose-the-wait-http-compression
+		return encodingGzip
+
+	case strings.Contains(enc, "deflate"):
+		// HTTP 1.1 "deflate" (RFC 2616) stands for DEFLATE data (RFC 1951)
+		// wrapped with zlib (RFC 1950). The zlib wrapper uses Adler-32
+		// checksum compared to CRC-32 used in "gzip" and thus is faster.
+		//
+		// But.. some old browsers (MSIE, Safari 5.1) incorrectly expect
+		// raw DEFLATE data only, without the mentioned zlib wrapper.
+		// Because of this major confusion, most modern browsers try it
+		// both ways, first looking for zlib headers.
+		// Quote by Mark Adler: http://stackoverflow.com/a/9186091/385548
+		//
+		// The list of browsers having problems is quite big, see:
+		// http://zoompf.com/blog/2012/02/lose-the-wait-http-compression
+		// https://web.archive.org/web/20120321182910/http://www.vervestudios.co/projects/compression-tests/results
+		//
+		// That's why we prefer gzip over deflate. It's just more reliable
+		// and not significantly slower than gzip.
+		return encodingDeflate
+
+		// NOTE: Not implemented, intentionally:
+		// case "compress": // LZW. Deprecated.
+		// case "bzip2":    // Too slow on-the-fly.
+		// case "zopfli":   // Too slow on-the-fly.
+		// case "xz":       // Too slow on-the-fly.
+	}
+
+	return encodingNone
+}
+
+type maybeCompressResponseWriter struct {
+	http.ResponseWriter
+	w            io.Writer
+	encoding     encoding
+	contentTypes map[string]struct{}
+	level        int
+	wroteHeader  bool
+}
+
+func (w *maybeCompressResponseWriter) WriteHeader(code int) {
+	if w.wroteHeader {
+		return
+	}
+	w.wroteHeader = true
+	defer w.ResponseWriter.WriteHeader(code)
+
+	// Already compressed data?
+	if w.ResponseWriter.Header().Get("Content-Encoding") != "" {
+		return
+	}
+	// The content-length after compression is unknown
+	w.ResponseWriter.Header().Del("Content-Length")
+
+	// Parse the first part of the Content-Type response header.
+	contentType := ""
+	parts := strings.Split(w.ResponseWriter.Header().Get("Content-Type"), ";")
+	if len(parts) > 0 {
+		contentType = parts[0]
+	}
+
+	// Is the content type compressable?
+	if _, ok := w.contentTypes[contentType]; !ok {
+		return
+	}
+
+	// Select the compress writer.
+	switch w.encoding {
+	case encodingGzip:
+		gw, err := gzip.NewWriterLevel(w.ResponseWriter, w.level)
+		if err != nil {
+			w.w = w.ResponseWriter
+			return
+		}
+		w.w = gw
+		w.ResponseWriter.Header().Set("Content-Encoding", "gzip")
+
+	case encodingDeflate:
+		dw, err := flate.NewWriter(w.ResponseWriter, w.level)
+		if err != nil {
+			w.w = w.ResponseWriter
+			return
+		}
+		w.w = dw
+		w.ResponseWriter.Header().Set("Content-Encoding", "deflate")
+	}
+}
+
+func (w *maybeCompressResponseWriter) Write(p []byte) (int, error) {
+	if !w.wroteHeader {
+		w.WriteHeader(http.StatusOK)
+	}
+
+	return w.w.Write(p)
+}
+
+func (w *maybeCompressResponseWriter) Flush() {
+	if f, ok := w.w.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+func (w *maybeCompressResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if hj, ok := w.w.(http.Hijacker); ok {
+		return hj.Hijack()
+	}
+	return nil, nil, errors.New("chi/middleware: http.Hijacker is unavailable on the writer")
+}
+
+func (w *maybeCompressResponseWriter) CloseNotify() <-chan bool {
+	if cn, ok := w.w.(http.CloseNotifier); ok {
+		return cn.CloseNotify()
+	}
+
+	// If the underlying writer does not implement http.CloseNotifier, return
+	// a channel that never receives a value. The semantics here is that the
+	// client never disconnnects before the request is processed by the
+	// http.Handler, which is close enough to the default behavior (when
+	// CloseNotify() is not even called).
+	return make(chan bool, 1)
+}
+
+func (w *maybeCompressResponseWriter) Close() error {
+	if c, ok := w.w.(io.WriteCloser); ok {
+		return c.Close()
+	}
+	return errors.New("chi/middleware: io.WriteCloser is unavailable on the writer")
+}