sprechstunden-go/templating/templates.go

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package templating
import (
"fmt"
"html/template"
"io"
"log"
"net/http"
"officeHours/models"
"os"
"time"
)
// parsed templates available for execution
var templates map[string]*template.Template = map[string]*template.Template{}
// Initialise and parse templates.
//
// Should only be called once.
//
// Since this is something which may error and feels like
// it should not be done automatically on import,
// put it into a function.
func InitTemplates() error {
const templateDir = "templating/templates/"
var funcs = template.FuncMap{
"DayName": models.DayName,
"divide": func(i int, j int) int { return i / j },
}
var emptyTemplate = template.New("").Funcs(funcs)
var baseTemplate, err = template.ParseFiles(templateDir + "base.html")
if err != nil {
return fmt.Errorf("parsing base template failed:\n%w", err)
}
baseTemplate.Funcs(funcs)
type toCache struct {
filename string
standalone bool
}
var toParse = map[string]toCache{
// full html templates
"addFailure": {"addFailure.html", false},
"addMask": {"addMask.html", false},
"addSuccess": {"addSuccess.html", false},
"deleteSuccess": {"deleteSuccess.html", false},
"executeFailure": {"executeFailure.html", false},
"executeSuccess": {"executeSuccess.html", false},
"index": {"index.html", false},
"requestNotFound": {"requestNotFound.html", false},
// standalone templates
"confirmationMail": {"confirmationMail", true},
"officeHourTable": {"officeHourTable.html", true},
"td": {"td.html", true},
}
// parse templates and add to global mapping
for key, tmpl := range toParse {
if _, exists := templates[key]; exists {
return fmt.Errorf("template '%s' already parsed", key)
}
fullName := templateDir + tmpl.filename
// check that template file
info, err := os.Stat(fullName)
if err != nil {
return fmt.Errorf("adding template %s failed:\n%w", tmpl.filename, err)
}
if info.IsDir() {
return fmt.Errorf("adding template %s failed: is a directory", tmpl.filename)
}
// parse
var parsed *template.Template
if tmpl.standalone {
parsed, err = emptyTemplate.Clone()
parsed = parsed.New(tmpl.filename)
} else {
parsed, err = baseTemplate.Clone()
}
if err != nil {
return fmt.Errorf("cloning base template failed:\n%w", err)
}
parsed, err = parsed.ParseFiles(fullName)
if err != nil {
return fmt.Errorf("parsing template %s failed:\n%w", tmpl.filename, err)
}
templates[key] = parsed
}
return nil
}
// Execute a template and write it to the given writer.
//
// Parameters:
// - name: name of the template to execute
// - data: passed through to the template
func WriteTemplate(w io.Writer, name string, data any) error {
tmpl, exists := templates[name]
if !exists {
return fmt.Errorf("template %s not available", name)
}
tmpl, err := tmpl.Clone()
if err != nil {
return fmt.Errorf("cloning template failed:\n%w", err)
}
err = tmpl.Execute(w, data)
if err != nil {
return fmt.Errorf("template execution failed:\n%w", err)
}
return nil
}
// Execute a template and write it to a http writer.
//
// Similar to WriteTemplate, but in error case this adds a corresponding
// status code and writes an error message to the writer.
//
// Typically, this is the final action in handling an http request.
//
// Parameters:
// - name: name of the template to execute
// - data: passed through to the template
func ServeTemplate(w http.ResponseWriter, name string, data any) {
// TODO: make this return an error, handle on top of every request handler
err := WriteTemplate(w, name, data)
if err != nil {
err = fmt.Errorf("writing template failed:\n%w", err)
log.Println(err.Error())
w.WriteHeader(http.StatusInternalServerError)
io.WriteString(w, `Internal Server Error.
Du kannst uns helfen, indem du folgende Fehlermeldung per Mail
an sprechstunden@mathebau.de sendest:
Fehler um\n
`+time.Now().String()+"\n"+err.Error())
return
}
}