// Copyright 2017 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/>.
/*
Show nicely (but simple) formatted HTML error pages (or respond with JSON
if the appropriate `Accept` header is set)) for the http package.
*/
package http
import (
"encoding/json"
"fmt"
"html/template"
"net/http"
"strings"
"time"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/metrics"
"github.com/ethereum/go-ethereum/swarm/api"
)
//templateMap holds a mapping of an HTTP error code to a template
var templateMap map[int]*template.Template
var caseErrors []CaseError
//metrics variables
var (
htmlCounter = metrics.NewRegisteredCounter("api.http.errorpage.html.count", nil)
jsonCounter = metrics.NewRegisteredCounter("api.http.errorpage.json.count", nil)
)
//parameters needed for formatting the correct HTML page
type ErrorParams struct {
Msg string
Code int
Timestamp string
template *template.Template
Details template.HTML
}
//a custom error case struct that would be used to store validators and
//additional error info to display with client responses.
type CaseError struct {
Validator func(*Request) bool
Msg func(*Request) string
}
//we init the error handling right on boot time, so lookup and http response is fast
func init() {
initErrHandling()
}
func initErrHandling() {
//pages are saved as strings - get these strings
genErrPage := GetGenericErrorPage()
notFoundPage := GetNotFoundErrorPage()
multipleChoicesPage := GetMultipleChoicesErrorPage()
//map the codes to the available pages
tnames := map[int]string{
0: genErrPage, //default
http.StatusBadRequest: genErrPage,
http.StatusNotFound: notFoundPage,
http.StatusMultipleChoices: multipleChoicesPage,
http.StatusInternalServerError: genErrPage,
}
templateMap = make(map[int]*template.Template)
for code, tname := range tnames {
//assign formatted HTML to the code
templateMap[code] = template.Must(template.New(fmt.Sprintf("%d", code)).Parse(tname))
}
caseErrors = []CaseError{
{
Validator: func(r *Request) bool { return r.uri != nil && r.uri.Addr != "" && strings.HasPrefix(r.uri.Addr, "0x") },
Msg: func(r *Request) string {
uriCopy := r.uri
uriCopy.Addr = strings.TrimPrefix(uriCopy.Addr, "0x")
return fmt.Sprintf(`The requested hash seems to be prefixed with '0x'. You will be redirected to the correct URL within 5 seconds.<br/>
Please click <a href='%[1]s'>here</a> if your browser does not redirect you.<script>setTimeout("location.href='%[1]s';",5000);</script>`, "/"+uriCopy.String())
},
}}
}
//ValidateCaseErrors is a method that process the request object through certain validators
//that assert if certain conditions are met for further information to log as an error
func ValidateCaseErrors(r *Request) string {
for _, err := range caseErrors {
if err.Validator(r) {
return err.Msg(r)
}
}
return ""
}
//ShowMultipeChoices is used when a user requests a resource in a manifest which results
//in ambiguous results. It returns a HTML page with clickable links of each of the entry
//in the manifest which fits the request URI ambiguity.
//For example, if the user requests bzz:/<hash>/read and that manifest contains entries
//"readme.md" and "readinglist.txt", a HTML page is returned with this two links.
//This only applies if the manifest has no default entry
func ShowMultipleChoices(w http.ResponseWriter, r *Request, list api.ManifestList) {
msg := ""
if list.Entries == nil {
ShowError(w, r, "Could not resolve", http.StatusInternalServerError)
return
}
//make links relative
//requestURI comes with the prefix of the ambiguous path, e.g. "read" for "readme.md" and "readinglist.txt"
//to get clickable links, need to remove the ambiguous path, i.e. "read"
idx := strings.LastIndex(r.RequestURI, "/")
if idx == -1 {
ShowError(w, r, "Internal Server Error", http.StatusInternalServerError)
return
}
//remove ambiguous part
base := r.RequestURI[:idx+1]
for _, e := range list.Entries {
//create clickable link for each entry
msg += "<a href='" + base + e.Path + "'>" + e.Path + "</a><br/>"
}
respond(w, &r.Request, &ErrorParams{
Code: http.StatusMultipleChoices,
Details: template.HTML(msg),
Timestamp: time.Now().Format(time.RFC1123),
template: getTemplate(http.StatusMultipleChoices),
})
}
//ShowError is used to show an HTML error page to a client.
//If there is an `Accept` header of `application/json`, JSON will be returned instead
//The function just takes a string message which will be displayed in the error page.
//The code is used to evaluate which template will be displayed
//(and return the correct HTTP status code)
func ShowError(w http.ResponseWriter, r *Request, msg string, code int) {
additionalMessage := ValidateCaseErrors(r)
if code == http.StatusInternalServerError {
log.Error(msg)
}
respond(w, &r.Request, &ErrorParams{
Code: code,
Msg: msg,
Details: template.HTML(additionalMessage),
Timestamp: time.Now().Format(time.RFC1123),
template: getTemplate(code),
})
}
//evaluate if client accepts html or json response
func respond(w http.ResponseWriter, r *http.Request, params *ErrorParams) {
w.WriteHeader(params.Code)
if r.Header.Get("Accept") == "application/json" {
respondJson(w, params)
} else {
respondHtml(w, params)
}
}
//return a HTML page
func respondHtml(w http.ResponseWriter, params *ErrorParams) {
htmlCounter.Inc(1)
err := params.template.Execute(w, params)
if err != nil {
log.Error(err.Error())
}
}
//return JSON
func respondJson(w http.ResponseWriter, params *ErrorParams) {
jsonCounter.Inc(1)
w.Header().Set("Content-Type", "application/json")
json.NewEncoder(w).Encode(params)
}
//get the HTML template for a given code
func getTemplate(code int) *template.Template {
if val, tmpl := templateMap[code]; tmpl {
return val
} else {
return templateMap[0]
}
}
