// Copyright 2017 The Mellium Contributors.
// Use of this source code is governed by the BSD 2-clause
// license that can be found in the LICENSE file.

// +build ignore

// The gen command creates disco identity options from the disco-categories
// registry located at https://xmpp.org/registrar/disco-categories.html.
package main

import (
	"bytes"
	"encoding/xml"
	"flag"
	"go/format"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"text/template"
)

type registry struct {
	XMLName    xml.Name `xml:"registry"`
	Categories []struct {
		Name string `xml:"name"`
		Desc string `xml:"desc"`
		Type []struct {
			Name    string `xml:"name"`
			XMLLang string `xml:"http://www.w3.org/XML/1998/namespace lang"`
			Desc    string `xml:"desc"`
			Doc     string `xml:"doc"`
		} `xml:"type"`
	} `xml:"category"`
}

func main() {
	var (
		catURL  = `https://xmpp.org/registrar/disco-categories.xml`
		tmpDir  = os.TempDir()
		outPath = `./`
	)
	flag.StringVar(&catURL, "categories", catURL, "A link to the disco-categories registry")
	flag.StringVar(&tmpDir, "tmp", tmpDir, "A temporary directory to downlaod files to")
	flag.StringVar(&outPath, "out", outPath, "A directory to output Go files to")
	flag.Parse()

	ident := func(s string) string {
		return strings.Map(func(r rune) rune {
			switch r {
			case ' ', '-', '_':
				return rune(-1)
			}
			return r
		}, s)
	}

	tmpl := template.Must(template.New("categories").Funcs(map[string]interface{}{
		"ident": ident,
		"export": func(s string) string {
			s = strings.Title(s)
			// Manual tweaks to make the output more idiomatic Go.
			for _, cap := range []string{
				"Rss", "Xmpp", "Smtp", "Sms", "Qq", "Msn", "Lcs", "Irc", "Icq", "Aim",
				"S2s", "C2s", "Sm", "Pc", "Soap", "Pam", "Ntlm", "Ldap", "Http-Ws",
				"Mrim", "Ocs", "Pep", "Im",
			} {
				if strings.HasPrefix(s, cap) {
					s = strings.Replace(s, cap, strings.ToUpper(cap), 1)
					break
				}
			}
			return ident(s)
		},
	}).Parse(`// Code generated by running "go generate" in mellium.im/xmpp/disco. DO NOT EDIT.

package disco

// Predefined identities generated from the Service Discovery Identities
// Registry as registered with the XMPP Registrar.
var (
{{- range $cat := .Categories}}{{range .Type}}
	// Category: {{$cat.Desc}}
	// Type: {{.Desc}}
	{{export  $cat.Name}}{{export .Name}} = Identity{Category: {{printf "%q" $cat.Name}}, Type: {{printf "%q" .Name}}}
{{end}}{{end}}
)`))

	logger := log.New(os.Stderr, "", log.LstdFlags)
	if err := genFile(catURL, tmpDir, filepath.Join(outPath, "categories.go"), tmpl); err != nil {
		logger.Fatal(err)
	}
}

func genFile(regURL, tmpDir, outFile string, tmpl *template.Template) error {
	fd, err := openOrDownload(regURL, tmpDir)
	if err != nil {
		return err
	}
	defer fd.Close()

	out, err := os.Create(outFile)
	if err != nil {
		return err
	}
	defer fd.Close()

	reg := registry{}
	d := xml.NewDecoder(fd)
	if err = d.Decode(&reg); err != nil {
		return err
	}

	buf := new(bytes.Buffer)
	if err = tmpl.Execute(buf, reg); err != nil {
		return err
	}
	b, err := format.Source(buf.Bytes())
	if err != nil {
		return err
	}
	_, err = io.Copy(out, bytes.NewReader(b))
	return err
}

type writeCloser struct {
	io.Writer
	closer func() error
}

func (f writeCloser) Close() error {
	return f.closer()
}

// opens the provided registry URL (downloading it if it doesn't exist).
func openOrDownload(catURL, tmpDir string) (*os.File, error) {
	registryXML := filepath.Join(tmpDir, filepath.Base(catURL))
	fd, err := os.Open(registryXML)
	if err != nil {
		fd, err = os.Create(registryXML)
		if err != nil {
			return nil, err
		}
		// If we couldn't open it for reading, attempt to download it.
		resp, err := http.Get(catURL)
		if err != nil {
			return nil, err
		}
		_, err = io.Copy(fd, resp.Body)
		if err != nil {
			return nil, err
		}
		resp.Body.Close()
		_, err = fd.Seek(0, 0)
		if err != nil {
			return nil, err
		}
	}
	return fd, err
}