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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package sumweb implements the HTTP protocols for serving or accessing a go.sum database.
package sumweb
import (
"context"
"net/http"
"os"
"regexp"
"strings"
"golang.org/x/exp/sumdb/internal/tlog"
)
// A Server provides the external operations
// (underlying database access and so on)
// needed to implement the HTTP server Handler.
type Server interface {
// NewContext returns the context to use for the request r.
NewContext(r *http.Request) (context.Context, error)
// Signed returns the signed hash of the latest tree.
Signed(ctx context.Context) ([]byte, error)
// ReadRecords returns the content for the n records id through id+n-1.
ReadRecords(ctx context.Context, id, n int64) ([][]byte, error)
// Lookup looks up a record by its associated key ("module@version"),
// returning the record ID.
Lookup(ctx context.Context, key string) (int64, error)
// ReadTileData reads the content of tile t.
// It is only invoked for hash tiles (t.L ≥ 0).
ReadTileData(ctx context.Context, t tlog.Tile) ([]byte, error)
}
// A Handler is the go.sum database server handler,
// which should be invoked to serve the paths listed in Paths.
// The calling code is responsible for initializing Server.
type Handler struct {
Server Server
}
// Paths are the URL paths for which Handler should be invoked.
//
// Typically a server will do:
//
// handler := &sumweb.Handler{Server: srv}
// for _, path := range sumweb.Paths {
// http.HandleFunc(path, handler)
// }
var Paths = []string{
"/lookup/",
"/latest",
"/tile/",
}
var modVerRE = regexp.MustCompile(`^[^@]+@v[0-9]+\.[0-9]+\.[0-9]+(-[^@]*)?(\+incompatible)?$`)
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
ctx, err := h.Server.NewContext(r)
if err != nil {
http.Error(w, err.Error(), 500)
return
}
switch {
default:
http.NotFound(w, r)
case strings.HasPrefix(r.URL.Path, "/lookup/"):
mod := strings.TrimPrefix(r.URL.Path, "/lookup/")
if !modVerRE.MatchString(mod) {
http.Error(w, "invalid module@version syntax", http.StatusBadRequest)
return
}
i := strings.Index(mod, "@")
encPath, encVers := mod[:i], mod[i+1:]
path, err := decodePath(encPath)
if err != nil {
reportError(w, r, err)
return
}
vers, err := decodeVersion(encVers)
if err != nil {
reportError(w, r, err)
return
}
id, err := h.Server.Lookup(ctx, path+"@"+vers)
if err != nil {
reportError(w, r, err)
return
}
records, err := h.Server.ReadRecords(ctx, id, 1)
if err != nil {
// This should never happen - the lookup says the record exists.
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
if len(records) != 1 {
http.Error(w, "invalid record count returned by ReadRecords", http.StatusInternalServerError)
return
}
msg, err := tlog.FormatRecord(id, records[0])
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
signed, err := h.Server.Signed(ctx)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
w.Write(msg)
w.Write(signed)
case r.URL.Path == "/latest":
data, err := h.Server.Signed(ctx)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
w.Write(data)
case strings.HasPrefix(r.URL.Path, "/tile/"):
t, err := tlog.ParseTilePath(r.URL.Path[1:])
if err != nil {
http.Error(w, "invalid tile syntax", http.StatusBadRequest)
return
}
if t.L == -1 {
// Record data.
start := t.N << uint(t.H)
records, err := h.Server.ReadRecords(ctx, start, int64(t.W))
if err != nil {
reportError(w, r, err)
return
}
if len(records) != t.W {
http.Error(w, "invalid record count returned by ReadRecords", http.StatusInternalServerError)
return
}
var data []byte
for i, text := range records {
msg, err := tlog.FormatRecord(start+int64(i), text)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
data = append(data, msg...)
}
w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
w.Write(data)
return
}
data, err := h.Server.ReadTileData(ctx, t)
if err != nil {
reportError(w, r, err)
return
}
w.Header().Set("Content-Type", "application/octet-stream")
w.Write(data)
}
}
// reportError reports err to w.
// If it's a not-found, the reported error is 404.
// Otherwise it is an internal server error.
// The caller must only call reportError in contexts where
// a not-found err should be reported as 404.
func reportError(w http.ResponseWriter, r *http.Request, err error) {
if os.IsNotExist(err) {
http.Error(w, err.Error(), http.StatusNotFound)
return
}
http.Error(w, err.Error(), http.StatusInternalServerError)
}
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