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// 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"
"time"
"github.com/ethereum/go-ethereum/log"
)
//templateMap holds a mapping of an HTTP error code to a template
var templateMap map[int]*template.Template
//parameters needed for formatting the correct HTML page
type ErrorParams struct {
Msg string
Code int
Timestamp string
template *template.Template
Details template.HTML
}
//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()
//map the codes to the available pages
tnames := map[int]string{
0: genErrPage, //default
400: genErrPage,
404: notFoundPage,
500: 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))
}
}
//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 *http.Request, msg string, code int) {
if code == http.StatusInternalServerError {
log.Error(msg)
}
respond(w, r, &ErrorParams{
Code: code,
Msg: msg,
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) {
err := params.template.Execute(w, params)
if err != nil {
log.Error(err.Error())
}
}
//return JSON
func respondJson(w http.ResponseWriter, params *ErrorParams) {
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]
}
}
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