implement support for _redirects file

core/corehttp/gateway_handler.go

@@ -258,6 +258,22 @@ func (i *gatewayHandler) getOrHeadHandler(w http.ResponseWriter, r *http.Request
 		}
 	}
 
+	redirects, err := i.searchUpTreeForRedirects(r, urlPath)
+	if err == nil {
+		redirected, newPath, err := i.redirect(w, r, redirects)
+		if err != nil {
+			// FIXME what to do here with errors ...
+		}
+
+		if redirected {
+			return
+		}
+
+		if newPath != "" {
+			urlPath = newPath
+		}
+	}
+
 	parsedPath := ipath.New(urlPath)
 	if pathErr := parsedPath.IsValid(); pathErr != nil {
 		if prefix == "" && fixupSuperfluousNamespace(w, urlPath, r.URL.RawQuery) {
@@ -497,6 +513,46 @@ func (i *gatewayHandler) getOrHeadHandler(w http.ResponseWriter, r *http.Request
 	}
 }
 
+// redirect returns redirected, newPath (if rewrite), error
+func (i *gatewayHandler) redirect(w http.ResponseWriter, r *http.Request, path ipath.Resolved) (bool, string, error) {
+	node, err := i.api.Unixfs().Get(r.Context(), path)
+	if err != nil {
+		return false, "", fmt.Errorf("could not get redirects file: %v", err)
+	}
+
+	defer node.Close()
+
+	f, ok := node.(files.File)
+
+	if !ok {
+		return false, "", fmt.Errorf("redirect, could not convert node to file")
+	}
+
+	redirs := newRedirs(f)
+
+	// extract "file" part of URL, typically the part after /ipfs/CID/...
+	g := strings.Split(r.URL.Path, "/")
+
+	if len(g) > 3 {
+		filePartPath := "/" + strings.Join(g[3:], "/")
+
+		to, code := redirs.search(filePartPath)
+		if code > 0 {
+			if code == 200 {
+				// rewrite
+				newPath := strings.Join(g[0:3], "/") + "/" + to
+				return false, newPath, nil
+			}
+
+			// redirect
+			http.Redirect(w, r, to, code)
+			return true, "", nil
+		}
+	}
+
+	return false, "", nil
+}
+
 func (i *gatewayHandler) serveFile(w http.ResponseWriter, req *http.Request, name string, modtime time.Time, file files.File) {
 	size, err := file.Size()
 	if err != nil {
@@ -790,6 +846,25 @@ func getFilename(s string) string {
 	return gopath.Base(s)
 }
 
+func (i *gatewayHandler) searchUpTreeForRedirects(r *http.Request, path string) (ipath.Resolved, error) {
+	pathComponents := strings.Split(path, "/")
+
+	for idx := len(pathComponents); idx >= 3; idx-- {
+		rdir := gopath.Join(append(pathComponents[0:idx], "_redirects")...)
+		rdirPath := ipath.New("/" + rdir)
+		if rdirPath.IsValid() != nil {
+			break
+		}
+		resolvedPath, err := i.api.ResolvePath(r.Context(), rdirPath)
+		if err != nil {
+			continue
+		}
+		return resolvedPath, nil
+	}
+
+	return nil, fmt.Errorf("no redirects in any parent folder")
+}
+
 func (i *gatewayHandler) searchUpTreeFor404(r *http.Request, parsedPath ipath.Path) (ipath.Resolved, string, error) {
 	filename404, ctype, err := preferred404Filename(r.Header.Values("Accept"))
 	if err != nil {

core/corehttp/redirect.go

@@ -1,8 +1,14 @@
 package corehttp
 
 import (
+	"bufio"
+	"fmt"
+	"io"
 	"net"
 	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
 
 	core "github.com/ipfs/go-ipfs/core"
 )
@@ -26,3 +32,66 @@ type redirectHandler struct {
 func (i *redirectHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, i.path, 302)
 }
+
+type redirLine struct {
+	matcher string
+	to      string
+	code    int
+}
+
+func (rdl redirLine) match(s string) (bool, error) {
+	re, err := regexp.Compile(rdl.matcher)
+	if err != nil {
+		return false, fmt.Errorf("Failed to compile %v: %v", rdl.matcher, err)
+	}
+
+	match := re.FindString(s)
+	if match == "" {
+		return false, nil
+	}
+
+	return true, nil
+}
+
+type redirs []redirLine
+
+func newRedirs(f io.Reader) *redirs {
+	ret := redirs{}
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanLines)
+	for scanner.Scan() {
+		t := scanner.Text()
+		if len(t) > 0 && t[0] == '#' {
+			// comment, skip line
+			continue
+		}
+		groups := strings.Fields(scanner.Text())
+		if len(groups) >= 2 {
+			matcher := groups[0]
+			to := groups[1]
+			// default to 302 (temporary redirect)
+			code := 302
+			if len(groups) >= 3 {
+				c, err := strconv.Atoi(groups[2])
+				if err == nil {
+					code = c
+				}
+			}
+			ret = append(ret, redirLine{matcher, to, code})
+		}
+	}
+
+	return &ret
+}
+
+// returns "" if no redir
+func (r redirs) search(path string) (string, int) {
+	for _, rdir := range r {
+		m, err := rdir.match(path)
+		if m && err == nil {
+			return rdir.to, rdir.code
+		}
+	}
+
+	return "", 0
+}

core/corehttp/redirect_test.go

@@ -0,0 +1,37 @@
+package corehttp
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestRedirline(t *testing.T) {
+	for _, tc := range []struct {
+		matcher string
+		s       string
+		exp     bool
+		errExp  bool
+	}{
+		{"hi", "hi", true, false},
+		{"hi", "hithere", true, false},
+		{"^hi$", "hithere", false, false},
+		{"^hi$", "hi", true, false},
+		{"hi.*", "hithere", true, false},
+		{"/hi", "/hi/there", true, false},
+		{"^/hi/", "/hi/there/now", true, false},
+		{"^/hi/", "/hithere", false, false},
+		{"^/hi/(.*", "/hi/there/now", false, true},
+	} {
+		r := redirLine{tc.matcher, "to", 200}
+		ok, err := r.match(tc.s)
+		if ok != tc.exp {
+			t.Errorf("%v %v, expected %v, got %v", tc.matcher, tc.s, tc.exp,
+				ok)
+		}
+
+		if err != nil != tc.errExp {
+			fmt.Printf("regexp error %v\n", err)
+			t.Errorf("%v %v, expected error %v, got %v", tc.matcher, tc.s, tc.errExp, err == nil)
+		}
+	}
+}