templatehandler.go

package main

import (
	"bytes"
	"html/template"
	"log"
	"net/http"
	"os"
)

// TemplateHandler represents the handler of swagger URLs
type TemplateHandler struct {
	swaggerBaseDir    http.Dir
	swaggerBaseDirSet bool
	webuiBaseDir      http.Dir
	webuiBaseDirSet   bool
}

// NewTemplateHandler creates an TemplateHandler object
func NewTemplateHandler() *TemplateHandler {
	s := new(TemplateHandler)

	s.swaggerBaseDirSet = false
	s.webuiBaseDirSet = false

	return s
}

// SetSwaggerBaseDir configures swagger base dir
func (s *TemplateHandler) SetSwaggerBaseDir(swaggerBaseDir string) {
	s.swaggerBaseDir = http.Dir(swaggerBaseDir)

	s.swaggerBaseDirSet = true
}

// GetSwaggerOp GET swagger content
func (s *TemplateHandler) GetSwaggerOp() SupportedOp {
	return SupportedOp{"/swagger/swagger.yaml", "/swagger/swagger.yaml", "GET", s.ServeSwagger}
}

// SetSwaggerBaseDir configures webui base dir
func (s *TemplateHandler) setWebUIBaseDir(webuiBaseDir string) {
	s.webuiBaseDir = http.Dir(webuiBaseDir)

	s.webuiBaseDirSet = true
}

type swaggerParam struct {
	Scheme     string
	Hostname   string
	PathPrefix string
}

// ServeSwagger handles swagger yaml data file
func (s *TemplateHandler) ServeSwagger(w http.ResponseWriter, rq *http.Request) {

	if !s.swaggerBaseDirSet {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	f, err := s.swaggerBaseDir.Open("swagger.yaml")
	if err != nil {
		if os.IsNotExist(err) {
			w.WriteHeader(http.StatusNotFound)
		} else {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
		return
	}
	defer f.Close()

	tmpl := template.New("Swagger")

	// Read swagger template data
	buf := new(bytes.Buffer)
	if _, err := buf.ReadFrom(f); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	str := buf.String()

	// Try to guess original Scheme
	scheme := rq.URL.Scheme
	if len(rq.Header.Get("X-Forwarded-Proto")) > 0 {
		scheme = rq.Header.Get("X-Forwarded-Proto")
	}
	if len(scheme) == 0 {
		scheme = "http" // Default value
	}

	// Try to guess original Host
	host := rq.Host
	if len(rq.Header.Get("X-Forwarded-Host")) > 0 {
		host = rq.Header.Get("X-Forwarded-Host")
	}

	// Try to guess original Prefix
	prefix := "/"
	if len(rq.Header.Get("X-Forwarded-Prefix")) > 0 {
		prefix = rq.Header.Get("X-Forwarded-Prefix")
	}

	swP := swaggerParam{scheme, host, prefix}

	tmpl, err = tmpl.Parse(str) // Parse template file.
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if err := tmpl.Execute(w, swP); err != nil {
		log.Printf("Error executing swagger template: %v", err)
	}
}