path: root/swarm/api/http/server.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

/*
A simple http server interface to Swarm
*/
package http

import (
    "archive/tar"
    "bufio"
    "bytes"
    "context"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "io/ioutil"
    "mime"
    "mime/multipart"
    "net/http"
    "os"
    "path"
    "regexp"
    "strconv"
    "strings"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/swarm/api"
    "github.com/ethereum/go-ethereum/swarm/log"
    "github.com/ethereum/go-ethereum/swarm/storage"
    "github.com/ethereum/go-ethereum/swarm/storage/mru"
    "github.com/pborman/uuid"
    "github.com/rs/cors"
)

type resourceResponse struct {
    Manifest storage.Address `json:"manifest"`
    Resource string          `json:"resource"`
    Update   storage.Address `json:"update"`
}

var (
    postRawCount    = metrics.NewRegisteredCounter("api.http.post.raw.count", nil)
    postRawFail     = metrics.NewRegisteredCounter("api.http.post.raw.fail", nil)
    postFilesCount  = metrics.NewRegisteredCounter("api.http.post.files.count", nil)
    postFilesFail   = metrics.NewRegisteredCounter("api.http.post.files.fail", nil)
    deleteCount     = metrics.NewRegisteredCounter("api.http.delete.count", nil)
    deleteFail      = metrics.NewRegisteredCounter("api.http.delete.fail", nil)
    getCount        = metrics.NewRegisteredCounter("api.http.get.count", nil)
    getFail         = metrics.NewRegisteredCounter("api.http.get.fail", nil)
    getFileCount    = metrics.NewRegisteredCounter("api.http.get.file.count", nil)
    getFileNotFound = metrics.NewRegisteredCounter("api.http.get.file.notfound", nil)
    getFileFail     = metrics.NewRegisteredCounter("api.http.get.file.fail", nil)
    getFilesCount   = metrics.NewRegisteredCounter("api.http.get.files.count", nil)
    getFilesFail    = metrics.NewRegisteredCounter("api.http.get.files.fail", nil)
    getListCount    = metrics.NewRegisteredCounter("api.http.get.list.count", nil)
    getListFail     = metrics.NewRegisteredCounter("api.http.get.list.fail", nil)
)

// ServerConfig is the basic configuration needed for the HTTP server and also
// includes CORS settings.
type ServerConfig struct {
    Addr       string
    CorsString string
}

// browser API for registering bzz url scheme handlers:
// https://developer.mozilla.org/en/docs/Web-based_protocol_handlers
// electron (chromium) api for registering bzz url scheme handlers:
// https://github.com/atom/electron/blob/master/docs/api/protocol.md

// starts up http server
func StartHTTPServer(api *api.API, config *ServerConfig) {
    var allowedOrigins []string
    for _, domain := range strings.Split(config.CorsString, ",") {
        allowedOrigins = append(allowedOrigins, strings.TrimSpace(domain))
    }
    c := cors.New(cors.Options{
        AllowedOrigins: allowedOrigins,
        AllowedMethods: []string{"POST", "GET", "DELETE", "PATCH", "PUT"},
        MaxAge:         600,
        AllowedHeaders: []string{"*"},
    })
    hdlr := c.Handler(NewServer(api))

    go http.ListenAndServe(config.Addr, hdlr)
}

func NewServer(api *api.API) *Server {
    return &Server{api}
}

type Server struct {
    api *api.API
}

// Request wraps http.Request and also includes the parsed bzz URI
type Request struct {
    http.Request

    uri  *api.URI
    ruid string // request unique id
}

// HandlePostRaw handles a POST request to a raw bzz-raw:/ URI, stores the request
// body in swarm and returns the resulting storage address as a text/plain response
func (s *Server) HandlePostRaw(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.post.raw", "ruid", r.ruid)

    postRawCount.Inc(1)

    toEncrypt := false
    if r.uri.Addr == "encrypt" {
        toEncrypt = true
    }

    if r.uri.Path != "" {
        postRawFail.Inc(1)
        Respond(w, r, "raw POST request cannot contain a path", http.StatusBadRequest)
        return
    }

    if r.uri.Addr != "" && r.uri.Addr != "encrypt" {
        postRawFail.Inc(1)
        Respond(w, r, "raw POST request addr can only be empty or \"encrypt\"", http.StatusBadRequest)
        return
    }

    if r.Header.Get("Content-Length") == "" {
        postRawFail.Inc(1)
        Respond(w, r, "missing Content-Length header in request", http.StatusBadRequest)
        return
    }
    addr, _, err := s.api.Store(ctx, r.Body, r.ContentLength, toEncrypt)
    if err != nil {
        postRawFail.Inc(1)
        Respond(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    log.Debug("stored content", "ruid", r.ruid, "key", addr)

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, addr)
}

// HandlePostFiles handles a POST request to
// bzz:/<hash>/<path> which contains either a single file or multiple files
// (either a tar archive or multipart form), adds those files either to an
// existing manifest or to a new manifest under <path> and returns the
// resulting manifest hash as a text/plain response
func (s *Server) HandlePostFiles(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.post.files", "ruid", r.ruid)

    postFilesCount.Inc(1)
    contentType, params, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
    if err != nil {
        postFilesFail.Inc(1)
        Respond(w, r, err.Error(), http.StatusBadRequest)
        return
    }

    toEncrypt := false
    if r.uri.Addr == "encrypt" {
        toEncrypt = true
    }

    var addr storage.Address
    if r.uri.Addr != "" && r.uri.Addr != "encrypt" {
        addr, err = s.api.Resolve(ctx, r.uri)
        if err != nil {
            postFilesFail.Inc(1)
            Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusInternalServerError)
            return
        }
        log.Debug("resolved key", "ruid", r.ruid, "key", addr)
    } else {
        addr, err = s.api.NewManifest(ctx, toEncrypt)
        if err != nil {
            postFilesFail.Inc(1)
            Respond(w, r, err.Error(), http.StatusInternalServerError)
            return
        }
        log.Debug("new manifest", "ruid", r.ruid, "key", addr)
    }

    newAddr, err := s.updateManifest(ctx, addr, func(mw *api.ManifestWriter) error {
        switch contentType {

        case "application/x-tar":
            return s.handleTarUpload(ctx, r, mw)

        case "multipart/form-data":
            return s.handleMultipartUpload(ctx, r, params["boundary"], mw)

        default:
            return s.handleDirectUpload(ctx, r, mw)
        }
    })
    if err != nil {
        postFilesFail.Inc(1)
        Respond(w, r, fmt.Sprintf("cannot create manifest: %s", err), http.StatusInternalServerError)
        return
    }

    log.Debug("stored content", "ruid", r.ruid, "key", newAddr)

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, newAddr)
}

func (s *Server) handleTarUpload(ctx context.Context, req *Request, mw *api.ManifestWriter) error {
    log.Debug("handle.tar.upload", "ruid", req.ruid)
    tr := tar.NewReader(req.Body)
    for {
        hdr, err := tr.Next()
        if err == io.EOF {
            return nil
        } else if err != nil {
            return fmt.Errorf("error reading tar stream: %s", err)
        }

        // only store regular files
        if !hdr.FileInfo().Mode().IsRegular() {
            continue
        }

        // add the entry under the path from the request
        path := path.Join(req.uri.Path, hdr.Name)
        entry := &api.ManifestEntry{
            Path:        path,
            ContentType: hdr.Xattrs["user.swarm.content-type"],
            Mode:        hdr.Mode,
            Size:        hdr.Size,
            ModTime:     hdr.ModTime,
        }
        log.Debug("adding path to new manifest", "ruid", req.ruid, "bytes", entry.Size, "path", entry.Path)
        contentKey, err := mw.AddEntry(ctx, tr, entry)
        if err != nil {
            return fmt.Errorf("error adding manifest entry from tar stream: %s", err)
        }
        log.Debug("stored content", "ruid", req.ruid, "key", contentKey)
    }
}

func (s *Server) handleMultipartUpload(ctx context.Context, req *Request, boundary string, mw *api.ManifestWriter) error {
    log.Debug("handle.multipart.upload", "ruid", req.ruid)
    mr := multipart.NewReader(req.Body, boundary)
    for {
        part, err := mr.NextPart()
        if err == io.EOF {
            return nil
        } else if err != nil {
            return fmt.Errorf("error reading multipart form: %s", err)
        }

        var size int64
        var reader io.Reader = part
        if contentLength := part.Header.Get("Content-Length"); contentLength != "" {
            size, err = strconv.ParseInt(contentLength, 10, 64)
            if err != nil {
                return fmt.Errorf("error parsing multipart content length: %s", err)
            }
            reader = part
        } else {
            // copy the part to a tmp file to get its size
            tmp, err := ioutil.TempFile("", "swarm-multipart")
            if err != nil {
                return err
            }
            defer os.Remove(tmp.Name())
            defer tmp.Close()
            size, err = io.Copy(tmp, part)
            if err != nil {
                return fmt.Errorf("error copying multipart content: %s", err)
            }
            if _, err := tmp.Seek(0, io.SeekStart); err != nil {
                return fmt.Errorf("error copying multipart content: %s", err)
            }
            reader = tmp
        }

        // add the entry under the path from the request
        name := part.FileName()
        if name == "" {
            name = part.FormName()
        }
        path := path.Join(req.uri.Path, name)
        entry := &api.ManifestEntry{
            Path:        path,
            ContentType: part.Header.Get("Content-Type"),
            Size:        size,
            ModTime:     time.Now(),
        }
        log.Debug("adding path to new manifest", "ruid", req.ruid, "bytes", entry.Size, "path", entry.Path)
        contentKey, err := mw.AddEntry(ctx, reader, entry)
        if err != nil {
            return fmt.Errorf("error adding manifest entry from multipart form: %s", err)
        }
        log.Debug("stored content", "ruid", req.ruid, "key", contentKey)
    }
}

func (s *Server) handleDirectUpload(ctx context.Context, req *Request, mw *api.ManifestWriter) error {
    log.Debug("handle.direct.upload", "ruid", req.ruid)
    key, err := mw.AddEntry(ctx, req.Body, &api.ManifestEntry{
        Path:        req.uri.Path,
        ContentType: req.Header.Get("Content-Type"),
        Mode:        0644,
        Size:        req.ContentLength,
        ModTime:     time.Now(),
    })
    if err != nil {
        return err
    }
    log.Debug("stored content", "ruid", req.ruid, "key", key)
    return nil
}

// HandleDelete handles a DELETE request to bzz:/<manifest>/<path>, removes
// <path> from <manifest> and returns the resulting manifest hash as a
// text/plain response
func (s *Server) HandleDelete(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.delete", "ruid", r.ruid)

    deleteCount.Inc(1)
    key, err := s.api.Resolve(ctx, r.uri)
    if err != nil {
        deleteFail.Inc(1)
        Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusInternalServerError)
        return
    }

    newKey, err := s.updateManifest(ctx, key, func(mw *api.ManifestWriter) error {
        log.Debug(fmt.Sprintf("removing %s from manifest %s", r.uri.Path, key.Log()), "ruid", r.ruid)
        return mw.RemoveEntry(r.uri.Path)
    })
    if err != nil {
        deleteFail.Inc(1)
        Respond(w, r, fmt.Sprintf("cannot update manifest: %s", err), http.StatusInternalServerError)
        return
    }

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, newKey)
}

// Parses a resource update post url to corresponding action
// possible combinations:
// /            add multihash update to existing hash
// /raw         add raw update to existing hash
// /#           create new resource with first update as mulitihash
// /raw/#       create new resource with first update raw
func resourcePostMode(path string) (isRaw bool, frequency uint64, err error) {
    re, err := regexp.Compile("^(raw)?/?([0-9]+)?$")
    if err != nil {
        return isRaw, frequency, err
    }
    m := re.FindAllStringSubmatch(path, 2)
    var freqstr = "0"
    if len(m) > 0 {
        if m[0][1] != "" {
            isRaw = true
        }
        if m[0][2] != "" {
            freqstr = m[0][2]
        }
    } else if len(path) > 0 {
        return isRaw, frequency, fmt.Errorf("invalid path")
    }
    frequency, err = strconv.ParseUint(freqstr, 10, 64)
    return isRaw, frequency, err
}

// Handles creation of new mutable resources and adding updates to existing mutable resources
// There are two types of updates available, "raw" and "multihash."
// If the latter is used, a subsequent bzz:// GET call to the manifest of the resource will return
// the page that the multihash is pointing to, as if it held a normal swarm content manifest
//
// The resource name will be verbatim what is passed as the address part of the url.
// For example, if a POST is made to /bzz-resource:/foo.eth/raw/13 a new resource with frequency 13
// and name "foo.eth" will be created
func (s *Server) HandlePostResource(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.post.resource", "ruid", r.ruid)
    var err error
    var addr storage.Address
    var name string
    var outdata []byte
    isRaw, frequency, err := resourcePostMode(r.uri.Path)
    if err != nil {
        Respond(w, r, err.Error(), http.StatusBadRequest)
        return
    }

    // new mutable resource creation will always have a frequency field larger than 0
    if frequency > 0 {

        name = r.uri.Addr

        // the key is the content addressed root chunk holding mutable resource metadata information
        addr, err = s.api.ResourceCreate(r.Context(), name, frequency)
        if err != nil {
            code, err2 := s.translateResourceError(w, r, "resource creation fail", err)

            Respond(w, r, err2.Error(), code)
            return
        }

        // we create a manifest so we can retrieve the resource with bzz:// later
        // this manifest has a special "resource type" manifest, and its hash is the key of the mutable resource
        // root chunk
        m, err := s.api.NewResourceManifest(ctx, addr.Hex())
        if err != nil {
            Respond(w, r, fmt.Sprintf("failed to create resource manifest: %v", err), http.StatusInternalServerError)
            return
        }

        // the key to the manifest will be passed back to the client
        // the client can access the root chunk key directly through its Hash member
        // the manifest key should be set as content in the resolver of the ENS name
        // \TODO update manifest key automatically in ENS
        outdata, err = json.Marshal(m)
        if err != nil {
            Respond(w, r, fmt.Sprintf("failed to create json response: %s", err), http.StatusInternalServerError)
            return
        }
    } else {
        // to update the resource through http we need to retrieve the key for the mutable resource root chunk
        // that means that we retrieve the manifest and inspect its Hash member.
        manifestAddr := r.uri.Address()
        if manifestAddr == nil {
            manifestAddr, err = s.api.Resolve(ctx, r.uri)
            if err != nil {
                getFail.Inc(1)
                Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
                return
            }
        } else {
            w.Header().Set("Cache-Control", "max-age=2147483648")
        }

        // get the root chunk key from the manifest
        addr, err = s.api.ResolveResourceManifest(ctx, manifestAddr)
        if err != nil {
            getFail.Inc(1)
            Respond(w, r, fmt.Sprintf("error resolving resource root chunk for %s: %s", r.uri.Addr, err), http.StatusNotFound)
            return
        }

        log.Debug("handle.post.resource: resolved", "ruid", r.ruid, "manifestkey", manifestAddr, "rootchunkkey", addr)

        name, _, err = s.api.ResourceLookup(r.Context(), addr, 0, 0, &mru.LookupParams{})
        if err != nil {
            Respond(w, r, err.Error(), http.StatusNotFound)
            return
        }
    }

    // Creation and update must send data aswell. This data constitutes the update data itself.
    data, err := ioutil.ReadAll(r.Body)
    if err != nil {
        Respond(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    // Multihash will be passed as hex-encoded data, so we need to parse this to bytes
    if isRaw {
        _, _, _, err = s.api.ResourceUpdate(r.Context(), name, data)
        if err != nil {
            Respond(w, r, err.Error(), http.StatusBadRequest)
            return
        }
    } else {
        bytesdata, err := hexutil.Decode(string(data))
        if err != nil {
            Respond(w, r, err.Error(), http.StatusBadRequest)
            return
        }
        _, _, _, err = s.api.ResourceUpdateMultihash(r.Context(), name, bytesdata)
        if err != nil {
            Respond(w, r, err.Error(), http.StatusBadRequest)
            return
        }
    }

    // If we have data to return, write this now
    // \TODO there should always be data to return here
    if len(outdata) > 0 {
        w.Header().Add("Content-type", "text/plain")
        w.WriteHeader(http.StatusOK)
        fmt.Fprint(w, string(outdata))
        return
    }
    w.WriteHeader(http.StatusOK)
}

// Retrieve mutable resource updates:
// bzz-resource://<id> - get latest update
// bzz-resource://<id>/<n> - get latest update on period n
// bzz-resource://<id>/<n>/<m> - get update version m of period n
// <id> = ens name or hash
func (s *Server) HandleGetResource(ctx context.Context, w http.ResponseWriter, r *Request) {
    s.handleGetResource(ctx, w, r)
}

// TODO: Enable pass maxPeriod parameter
func (s *Server) handleGetResource(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.get.resource", "ruid", r.ruid)
    var err error

    // resolve the content key.
    manifestAddr := r.uri.Address()
    if manifestAddr == nil {
        manifestAddr, err = s.api.Resolve(ctx, r.uri)
        if err != nil {
            getFail.Inc(1)
            Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
            return
        }
    } else {
        w.Header().Set("Cache-Control", "max-age=2147483648")
    }

    // get the root chunk key from the manifest
    key, err := s.api.ResolveResourceManifest(ctx, manifestAddr)
    if err != nil {
        getFail.Inc(1)
        Respond(w, r, fmt.Sprintf("error resolving resource root chunk for %s: %s", r.uri.Addr, err), http.StatusNotFound)
        return
    }

    log.Debug("handle.get.resource: resolved", "ruid", r.ruid, "manifestkey", manifestAddr, "rootchunk key", key)

    // determine if the query specifies period and version
    var params []string
    if len(r.uri.Path) > 0 {
        params = strings.Split(r.uri.Path, "/")
    }
    var name string
    var period uint64
    var version uint64
    var data []byte
    now := time.Now()

    switch len(params) {
    case 0: // latest only
        name, data, err = s.api.ResourceLookup(r.Context(), key, 0, 0, nil)
    case 2: // specific period and version
        version, err = strconv.ParseUint(params[1], 10, 32)
        if err != nil {
            break
        }
        period, err = strconv.ParseUint(params[0], 10, 32)
        if err != nil {
            break
        }
        name, data, err = s.api.ResourceLookup(r.Context(), key, uint32(period), uint32(version), nil)
    case 1: // last version of specific period
        period, err = strconv.ParseUint(params[0], 10, 32)
        if err != nil {
            break
        }
        name, data, err = s.api.ResourceLookup(r.Context(), key, uint32(period), uint32(version), nil)
    default: // bogus
        err = mru.NewError(storage.ErrInvalidValue, "invalid mutable resource request")
    }

    // any error from the switch statement will end up here
    if err != nil {
        code, err2 := s.translateResourceError(w, r, "mutable resource lookup fail", err)
        Respond(w, r, err2.Error(), code)
        return
    }

    // All ok, serve the retrieved update
    log.Debug("Found update", "name", name, "ruid", r.ruid)
    w.Header().Set("Content-Type", "application/octet-stream")
    http.ServeContent(w, &r.Request, "", now, bytes.NewReader(data))
}

func (s *Server) translateResourceError(w http.ResponseWriter, r *Request, supErr string, err error) (int, error) {
    code := 0
    defaultErr := fmt.Errorf("%s: %v", supErr, err)
    rsrcErr, ok := err.(*mru.Error)
    if !ok && rsrcErr != nil {
        code = rsrcErr.Code()
    }
    switch code {
    case storage.ErrInvalidValue:
        return http.StatusBadRequest, defaultErr
    case storage.ErrNotFound, storage.ErrNotSynced, storage.ErrNothingToReturn, storage.ErrInit:
        return http.StatusNotFound, defaultErr
    case storage.ErrUnauthorized, storage.ErrInvalidSignature:
        return http.StatusUnauthorized, defaultErr
    case storage.ErrDataOverflow:
        return http.StatusRequestEntityTooLarge, defaultErr
    }

    return http.StatusInternalServerError, defaultErr
}

// HandleGet handles a GET request to
// - bzz-raw://<key> and responds with the raw content stored at the
//   given storage key
// - bzz-hash://<key> and responds with the hash of the content stored
//   at the given storage key as a text/plain response
func (s *Server) HandleGet(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.get", "ruid", r.ruid, "uri", r.uri)
    getCount.Inc(1)
    var err error
    addr := r.uri.Address()
    if addr == nil {
        addr, err = s.api.Resolve(ctx, r.uri)
        if err != nil {
            getFail.Inc(1)
            Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
            return
        }
    } else {
        w.Header().Set("Cache-Control", "max-age=2147483648, immutable") // url was of type bzz://<hex key>/path, so we are sure it is immutable.
    }

    log.Debug("handle.get: resolved", "ruid", r.ruid, "key", addr)

    // if path is set, interpret <key> as a manifest and return the
    // raw entry at the given path
    if r.uri.Path != "" {
        walker, err := s.api.NewManifestWalker(ctx, addr, nil)
        if err != nil {
            getFail.Inc(1)
            Respond(w, r, fmt.Sprintf("%s is not a manifest", addr), http.StatusBadRequest)
            return
        }
        var entry *api.ManifestEntry
        walker.Walk(func(e *api.ManifestEntry) error {
            // if the entry matches the path, set entry and stop
            // the walk
            if e.Path == r.uri.Path {
                entry = e
                // return an error to cancel the walk
                return errors.New("found")
            }

            // ignore non-manifest files
            if e.ContentType != api.ManifestType {
                return nil
            }

            // if the manifest's path is a prefix of the
            // requested path, recurse into it by returning
            // nil and continuing the walk
            if strings.HasPrefix(r.uri.Path, e.Path) {
                return nil
            }

            return api.ErrSkipManifest
        })
        if entry == nil {
            getFail.Inc(1)
            Respond(w, r, fmt.Sprintf("manifest entry could not be loaded"), http.StatusNotFound)
            return
        }
        addr = storage.Address(common.Hex2Bytes(entry.Hash))
    }
    etag := common.Bytes2Hex(addr)
    noneMatchEtag := r.Header.Get("If-None-Match")
    w.Header().Set("ETag", fmt.Sprintf("%q", etag)) // set etag to manifest key or raw entry key.
    if noneMatchEtag != "" {
        if bytes.Equal(storage.Address(common.Hex2Bytes(noneMatchEtag)), addr) {
            Respond(w, r, "Not Modified", http.StatusNotModified)
            return
        }
    }

    // check the root chunk exists by retrieving the file's size
    reader, isEncrypted := s.api.Retrieve(ctx, addr)
    if _, err := reader.Size(nil); err != nil {
        getFail.Inc(1)
        Respond(w, r, fmt.Sprintf("root chunk not found %s: %s", addr, err), http.StatusNotFound)
        return
    }

    w.Header().Set("X-Decrypted", fmt.Sprintf("%v", isEncrypted))

    switch {
    case r.uri.Raw():
        // allow the request to overwrite the content type using a query
        // parameter
        contentType := "application/octet-stream"
        if typ := r.URL.Query().Get("content_type"); typ != "" {
            contentType = typ
        }
        w.Header().Set("Content-Type", contentType)
        http.ServeContent(w, &r.Request, "", time.Now(), reader)
    case r.uri.Hash():
        w.Header().Set("Content-Type", "text/plain")
        w.WriteHeader(http.StatusOK)
        fmt.Fprint(w, addr)
    }
}

// HandleGetFiles handles a GET request to bzz:/<manifest> with an Accept
// header of "application/x-tar" and returns a tar stream of all files
// contained in the manifest
func (s *Server) HandleGetFiles(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.get.files", "ruid", r.ruid, "uri", r.uri)
    getFilesCount.Inc(1)
    if r.uri.Path != "" {
        getFilesFail.Inc(1)
        Respond(w, r, "files request cannot contain a path", http.StatusBadRequest)
        return
    }

    addr, err := s.api.Resolve(ctx, r.uri)
    if err != nil {
        getFilesFail.Inc(1)
        Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
        return
    }
    log.Debug("handle.get.files: resolved", "ruid", r.ruid, "key", addr)

    walker, err := s.api.NewManifestWalker(ctx, addr, nil)
    if err != nil {
        getFilesFail.Inc(1)
        Respond(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    tw := tar.NewWriter(w)
    defer tw.Close()
    w.Header().Set("Content-Type", "application/x-tar")
    w.WriteHeader(http.StatusOK)

    err = walker.Walk(func(entry *api.ManifestEntry) error {
        // ignore manifests (walk will recurse into them)
        if entry.ContentType == api.ManifestType {
            return nil
        }

        // retrieve the entry's key and size
        reader, isEncrypted := s.api.Retrieve(ctx, storage.Address(common.Hex2Bytes(entry.Hash)))
        size, err := reader.Size(nil)
        if err != nil {
            return err
        }
        w.Header().Set("X-Decrypted", fmt.Sprintf("%v", isEncrypted))

        // write a tar header for the entry
        hdr := &tar.Header{
            Name:    entry.Path,
            Mode:    entry.Mode,
            Size:    size,
            ModTime: entry.ModTime,
            Xattrs: map[string]string{
                "user.swarm.content-type": entry.ContentType,
            },
        }
        if err := tw.WriteHeader(hdr); err != nil {
            return err
        }

        // copy the file into the tar stream
        n, err := io.Copy(tw, io.LimitReader(reader, hdr.Size))
        if err != nil {
            return err
        } else if n != size {
            return fmt.Errorf("error writing %s: expected %d bytes but sent %d", entry.Path, size, n)
        }

        return nil
    })
    if err != nil {
        getFilesFail.Inc(1)
        log.Error(fmt.Sprintf("error generating tar stream: %s", err))
    }
}

// HandleGetList handles a GET request to bzz-list:/<manifest>/<path> and returns
// a list of all files contained in <manifest> under <path> grouped into
// common prefixes using "/" as a delimiter
func (s *Server) HandleGetList(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.get.list", "ruid", r.ruid, "uri", r.uri)
    getListCount.Inc(1)
    // ensure the root path has a trailing slash so that relative URLs work
    if r.uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
        http.Redirect(w, &r.Request, r.URL.Path+"/", http.StatusMovedPermanently)
        return
    }

    addr, err := s.api.Resolve(ctx, r.uri)
    if err != nil {
        getListFail.Inc(1)
        Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
        return
    }
    log.Debug("handle.get.list: resolved", "ruid", r.ruid, "key", addr)

    list, err := s.getManifestList(ctx, addr, r.uri.Path)

    if err != nil {
        getListFail.Inc(1)
        Respond(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    // if the client wants HTML (e.g. a browser) then render the list as a
    // HTML index with relative URLs
    if strings.Contains(r.Header.Get("Accept"), "text/html") {
        w.Header().Set("Content-Type", "text/html")
        err := htmlListTemplate.Execute(w, &htmlListData{
            URI: &api.URI{
                Scheme: "bzz",
                Addr:   r.uri.Addr,
                Path:   r.uri.Path,
            },
            List: &list,
        })
        if err != nil {
            getListFail.Inc(1)
            log.Error(fmt.Sprintf("error rendering list HTML: %s", err))
        }
        return
    }

    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(&list)
}

func (s *Server) getManifestList(ctx context.Context, addr storage.Address, prefix string) (list api.ManifestList, err error) {
    walker, err := s.api.NewManifestWalker(ctx, addr, nil)
    if err != nil {
        return
    }

    err = walker.Walk(func(entry *api.ManifestEntry) error {
        // handle non-manifest files
        if entry.ContentType != api.ManifestType {
            // ignore the file if it doesn't have the specified prefix
            if !strings.HasPrefix(entry.Path, prefix) {
                return nil
            }

            // if the path after the prefix contains a slash, add a
            // common prefix to the list, otherwise add the entry
            suffix := strings.TrimPrefix(entry.Path, prefix)
            if index := strings.Index(suffix, "/"); index > -1 {
                list.CommonPrefixes = append(list.CommonPrefixes, prefix+suffix[:index+1])
                return nil
            }
            if entry.Path == "" {
                entry.Path = "/"
            }
            list.Entries = append(list.Entries, entry)
            return nil
        }

        // if the manifest's path is a prefix of the specified prefix
        // then just recurse into the manifest by returning nil and
        // continuing the walk
        if strings.HasPrefix(prefix, entry.Path) {
            return nil
        }

        // if the manifest's path has the specified prefix, then if the
        // path after the prefix contains a slash, add a common prefix
        // to the list and skip the manifest, otherwise recurse into
        // the manifest by returning nil and continuing the walk
        if strings.HasPrefix(entry.Path, prefix) {
            suffix := strings.TrimPrefix(entry.Path, prefix)
            if index := strings.Index(suffix, "/"); index > -1 {
                list.CommonPrefixes = append(list.CommonPrefixes, prefix+suffix[:index+1])
                return api.ErrSkipManifest
            }
            return nil
        }

        // the manifest neither has the prefix or needs recursing in to
        // so just skip it
        return api.ErrSkipManifest
    })

    return list, nil
}

// HandleGetFile handles a GET request to bzz://<manifest>/<path> and responds
// with the content of the file at <path> from the given <manifest>
func (s *Server) HandleGetFile(ctx context.Context, w http.ResponseWriter, r *Request) {
    log.Debug("handle.get.file", "ruid", r.ruid)
    getFileCount.Inc(1)
    // ensure the root path has a trailing slash so that relative URLs work
    if r.uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
        http.Redirect(w, &r.Request, r.URL.Path+"/", http.StatusMovedPermanently)
        return
    }
    var err error
    manifestAddr := r.uri.Address()

    if manifestAddr == nil {
        manifestAddr, err = s.api.Resolve(ctx, r.uri)
        if err != nil {
            getFileFail.Inc(1)
            Respond(w, r, fmt.Sprintf("cannot resolve %s: %s", r.uri.Addr, err), http.StatusNotFound)
            return
        }
    } else {
        w.Header().Set("Cache-Control", "max-age=2147483648, immutable") // url was of type bzz://<hex key>/path, so we are sure it is immutable.
    }

    log.Debug("handle.get.file: resolved", "ruid", r.ruid, "key", manifestAddr)

    reader, contentType, status, contentKey, err := s.api.Get(ctx, manifestAddr, r.uri.Path)

    etag := common.Bytes2Hex(contentKey)
    noneMatchEtag := r.Header.Get("If-None-Match")
    w.Header().Set("ETag", fmt.Sprintf("%q", etag)) // set etag to actual content key.
    if noneMatchEtag != "" {
        if bytes.Equal(storage.Address(common.Hex2Bytes(noneMatchEtag)), contentKey) {
            Respond(w, r, "Not Modified", http.StatusNotModified)
            return
        }
    }

    if err != nil {
        switch status {
        case http.StatusNotFound:
            getFileNotFound.Inc(1)
            Respond(w, r, err.Error(), http.StatusNotFound)
        default:
            getFileFail.Inc(1)
            Respond(w, r, err.Error(), http.StatusInternalServerError)
        }
        return
    }

    //the request results in ambiguous files
    //e.g. /read with readme.md and readinglist.txt available in manifest
    if status == http.StatusMultipleChoices {
        list, err := s.getManifestList(ctx, manifestAddr, r.uri.Path)

        if err != nil {
            getFileFail.Inc(1)
            Respond(w, r, err.Error(), http.StatusInternalServerError)
            return
        }

        log.Debug(fmt.Sprintf("Multiple choices! --> %v", list), "ruid", r.ruid)
        //show a nice page links to available entries
        ShowMultipleChoices(w, r, list)
        return
    }

    // check the root chunk exists by retrieving the file's size
    if _, err := reader.Size(nil); err != nil {
        getFileNotFound.Inc(1)
        Respond(w, r, fmt.Sprintf("file not found %s: %s", r.uri, err), http.StatusNotFound)
        return
    }

    w.Header().Set("Content-Type", contentType)
    http.ServeContent(w, &r.Request, "", time.Now(), newBufferedReadSeeker(reader, getFileBufferSize))
}

// The size of buffer used for bufio.Reader on LazyChunkReader passed to
// http.ServeContent in HandleGetFile.
// Warning: This value influences the number of chunk requests and chunker join goroutines
// per file request.
// Recommended value is 4 times the io.Copy default buffer value which is 32kB.
const getFileBufferSize = 4 * 32 * 1024

// bufferedReadSeeker wraps bufio.Reader to expose Seek method
// from the provied io.ReadSeeker in newBufferedReadSeeker.
type bufferedReadSeeker struct {
    r io.Reader
    s io.Seeker
}

// newBufferedReadSeeker creates a new instance of bufferedReadSeeker,
// out of io.ReadSeeker. Argument `size` is the size of the read buffer.
func newBufferedReadSeeker(readSeeker io.ReadSeeker, size int) bufferedReadSeeker {
    return bufferedReadSeeker{
        r: bufio.NewReaderSize(readSeeker, size),
        s: readSeeker,
    }
}

func (b bufferedReadSeeker) Read(p []byte) (n int, err error) {
    return b.r.Read(p)
}

func (b bufferedReadSeeker) Seek(offset int64, whence int) (int64, error) {
    return b.s.Seek(offset, whence)
}

func (s *Server) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
    ctx := context.TODO()

    defer metrics.GetOrRegisterResettingTimer(fmt.Sprintf("http.request.%s.time", r.Method), nil).UpdateSince(time.Now())
    req := &Request{Request: *r, ruid: uuid.New()[:8]}
    metrics.GetOrRegisterCounter(fmt.Sprintf("http.request.%s", r.Method), nil).Inc(1)
    log.Info("serving request", "ruid", req.ruid, "method", r.Method, "url", r.RequestURI)

    // wrapping the ResponseWriter, so that we get the response code set by http.ServeContent
    w := newLoggingResponseWriter(rw)

    if r.RequestURI == "/" && strings.Contains(r.Header.Get("Accept"), "text/html") {

        err := landingPageTemplate.Execute(w, nil)
        if err != nil {
            log.Error(fmt.Sprintf("error rendering landing page: %s", err))
        }
        return
    }

    if r.URL.Path == "/robots.txt" {
        w.Header().Set("Last-Modified", time.Now().Format(http.TimeFormat))
        fmt.Fprintf(w, "User-agent: *\nDisallow: /")
        return
    }

    if r.RequestURI == "/" && strings.Contains(r.Header.Get("Accept"), "application/json") {
        w.Header().Set("Content-Type", "application/json")
        w.WriteHeader(http.StatusOK)
        json.NewEncoder(w).Encode("Welcome to Swarm!")
        return
    }

    uri, err := api.Parse(strings.TrimLeft(r.URL.Path, "/"))
    if err != nil {
        Respond(w, req, fmt.Sprintf("invalid URI %q", r.URL.Path), http.StatusBadRequest)
        return
    }

    req.uri = uri

    log.Debug("parsed request path", "ruid", req.ruid, "method", req.Method, "uri.Addr", req.uri.Addr, "uri.Path", req.uri.Path, "uri.Scheme", req.uri.Scheme)

    switch r.Method {
    case "POST":
        if uri.Raw() {
            log.Debug("handlePostRaw")
            s.HandlePostRaw(ctx, w, req)
        } else if uri.Resource() {
            log.Debug("handlePostResource")
            s.HandlePostResource(ctx, w, req)
        } else if uri.Immutable() || uri.List() || uri.Hash() {
            log.Debug("POST not allowed on immutable, list or hash")
            Respond(w, req, fmt.Sprintf("POST method on scheme %s not allowed", uri.Scheme), http.StatusMethodNotAllowed)
        } else {
            log.Debug("handlePostFiles")
            s.HandlePostFiles(ctx, w, req)
        }

    case "PUT":
        Respond(w, req, fmt.Sprintf("PUT method to %s not allowed", uri), http.StatusBadRequest)
        return

    case "DELETE":
        if uri.Raw() {
            Respond(w, req, fmt.Sprintf("DELETE method to %s not allowed", uri), http.StatusBadRequest)
            return
        }
        s.HandleDelete(ctx, w, req)

    case "GET":

        if uri.Resource() {
            s.HandleGetResource(ctx, w, req)
            return
        }

        if uri.Raw() || uri.Hash() {
            s.HandleGet(ctx, w, req)
            return
        }

        if uri.List() {
            s.HandleGetList(ctx, w, req)
            return
        }

        if r.Header.Get("Accept") == "application/x-tar" {
            s.HandleGetFiles(ctx, w, req)
            return
        }

        s.HandleGetFile(ctx, w, req)

    default:
        Respond(w, req, fmt.Sprintf("%s method is not supported", r.Method), http.StatusMethodNotAllowed)
    }

    log.Info("served response", "ruid", req.ruid, "code", w.statusCode)
}

func (s *Server) updateManifest(ctx context.Context, addr storage.Address, update func(mw *api.ManifestWriter) error) (storage.Address, error) {
    mw, err := s.api.NewManifestWriter(ctx, addr, nil)
    if err != nil {
        return nil, err
    }

    if err := update(mw); err != nil {
        return nil, err
    }

    addr, err = mw.Store()
    if err != nil {
        return nil, err
    }
    log.Debug(fmt.Sprintf("generated manifest %s", addr))
    return addr, nil
}

type loggingResponseWriter struct {
    http.ResponseWriter
    statusCode int
}

func newLoggingResponseWriter(w http.ResponseWriter) *loggingResponseWriter {
    return &loggingResponseWriter{w, http.StatusOK}
}

func (lrw *loggingResponseWriter) WriteHeader(code int) {
    lrw.statusCode = code
    lrw.ResponseWriter.WriteHeader(code)
}