package engine
import (
"bytes"
"net/http"
"strconv"
"strings"
)
const (
// Highlight of errors in the code
preHighlight = ""
postHighlight = ""
)
// Given a lowercase string for the language, return an approprite error page title
func errorPageTitle(lang string) string {
switch lang {
case "":
return "Error"
case "css":
return "CSS Error"
case "gcss":
return "GCSS Error"
case "html":
return "HTML Error"
case "jsx":
return "JSX Error"
default:
// string.Title(lang) was used here before, but staticcheck recommends against it
return lang + " Error"
}
}
// PrettyError serves an informative error page to the user
// Takes a ResponseWriter, title (can be empty), filename, filebytes, errormessage and
// programming/scripting/template language (i.e. "lua". Can be empty).
func (ac *Config) PrettyError(w http.ResponseWriter, req *http.Request, filename string, filebytes []byte, errormessage, lang string) {
// HTTP status
// w.WriteHeader(http.StatusInternalServerError)
w.WriteHeader(http.StatusOK)
// HTTP content type
w.Header().Add("Content-Type", "text/html;charset=utf-8")
var (
// If there is code to be displayed
code string
err error
)
// The line that the error refers to, for the case of Lua
linenr := -1
if len(filebytes) > 0 {
if lang == "lua" {
// If the first line of the error message has two colons, see if the second field is a number
fields := strings.SplitN(errormessage, ":", 3)
if len(fields) > 2 {
// Extract the line number from the error message, if possible
numberfield := fields[1]
if strings.Contains(numberfield, "(") {
numberfield = strings.Split(numberfield, "(")[0]
}
linenr, err = strconv.Atoi(numberfield)
// Subtract one to make it a slice index instead of human-friendly line number
linenr--
// Set linenumber to -1 if the conversion failed
if err != nil {
linenr = -1
}
}
} else if lang == "amber" {
// If the error contains "- Line: ", extract the line number
if strings.Contains(errormessage, "- Line: ") {
fields := strings.SplitN(errormessage, "- Line: ", 2)
if strings.Contains(fields[1], ",") {
numberfields := strings.SplitN(fields[1], ",", 2)
linenr, err = strconv.Atoi(strings.TrimSpace(numberfields[0]))
// Subtract one to make it a slice index instead of human-friendly line number
linenr--
// Set linenumber to -1 if the conversion failed
if err != nil {
linenr = -1
}
}
}
}
// Escape any HTML in the code, so that the pretty printer is not confused
filebytes = bytes.ReplaceAll(filebytes, []byte("<"), []byte("<"))
// Modify the line that is to be highlighted
bytelines := bytes.Split(filebytes, []byte("\n"))
if (linenr >= 0) && (linenr < len(bytelines)) {
bytelines[linenr] = []byte(preHighlight + string(bytelines[linenr]) + postHighlight)
}
// Build a string from the bytelines slice
code = string(bytes.Join(bytelines, []byte("\n")))
}
// Set an appropriate title
title := errorPageTitle(lang)
// Set the highlight class
langclass := lang
// Turn off highlighting for some languages
switch lang {
case "", "amber", "gcss":
langclass = "nohighlight"
}
// Highlighting for the error message
errorclass := "json" // "nohighlight"
// Inform the user of the error
htmldata := []byte(`
` + title + `
` + title + `
Contents of ` + filename + `:
` + code + `
Error message:
` + strings.TrimSpace(errormessage) + `
` + ac.versionString + `
`)
if ac.autoRefresh {
// Insert JavaScript for refreshing the page into the generated HTML
htmldata = ac.InsertAutoRefresh(req, htmldata)
}
w.Write(htmldata)
}