package main

import (
	"bytes"
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
	"ni/gmi2html"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	txt "text/template"
	"time"
)

var tplPage = `
{{ define "content" }}
{{ .Content }}
{{ if .Backlinks }}
<hr>
<p id="backlinks"><b>backlinks:</b></p>
<ul>
{{ range .Backlinks }}
<li><a href="{{ . }}">{{ . }}</a></li>
{{ end }}
</ul>
{{ end }}
{{ end }}
`

var tplChangelog = `
{{ define "content" }}
<ul>
{{ range . }}
<li><a href="{{ .Name }}">{{ .Name }}</a> {{ .TimeFormatted }}</li>
{{ end }}
</ul>
{{ end }}
`

var tplFeed = `
{{ define "content" }}
  <id>{{ .url }}</id>
  <updated>{{ .TimeRFC3339 }}</updated>
  <link rel="self" href="{{ .url }}atom.xml"/>
  {{ range .files }}
  <entry>
    <title>{{ .Name }}</title>
    <link rel="alternate" href="{{ $.url }}{{ .Name }}"/>
    <updated>{{ .TimeRFC3339 }}</updated>
    <id>{{ $.url }}{{ .Name }}</id>
  </entry>
  {{ end }}
{{ end }}
`

var filename = regexp.MustCompile(`^[a-z0-9\-]+\.gmi$`)
var re = regexp.MustCompile(`\[\[([a-z0-9\-]+)\]\]`)
var PageContent *template.Template
var PageChangelog *template.Template
var atomFeed *txt.Template

func backlinks(in, name string) []string {
	var rv []string
	bl, err := exec.Command("/bin/sh", "-c", "grep -l  '\\[\\["+name[:len(name)-4]+"\\]\\]' "+in+"/*.gmi").Output()
	if err != nil {
		return rv
	}
	for _, link := range strings.Fields(string(bl)) {
		oname := outputName(link[len(in+"/"):])
		if oname != outputName(name) {
			rv = append(rv, oname)
		}
	}
	return rv
}

func process(in, name string, d []byte) []byte {
	html := bytes.NewBufferString("")

	err := PageContent.Execute(html, map[string]interface{}{
		"Title":     name,
		"Content":   template.HTML(re.ReplaceAllString(gmi2html.Convert(string(d)), `<a href="$1.html">$1</a>`)),
		"Backlinks": backlinks(in, name),
	})
	if err != nil {
		log.Fatal(err)
	}
	return html.Bytes()
}

func buildChangelog(f []File) []byte {
	html := bytes.NewBufferString("")
	err := PageChangelog.Execute(html, f)
	if err != nil {
		log.Fatal(err)
	}
	return html.Bytes()
}

func buildAtomFeed(f []File, url string) []byte {
	html := bytes.NewBufferString("")
	err := atomFeed.Execute(html, map[string]interface{}{
		"TimeRFC3339": time.Now().Format(time.RFC3339),
		"files":       f,
		"url":         url,
	})
	if err != nil {
		log.Fatal(err)
	}
	return html.Bytes()
}

type File struct {
	Name          string
	UpdatedAt     time.Time
	TimeFormatted string
	TimeRFC3339   string
}

func outputName(inputName string) string {
	return inputName[:len(inputName)-3] + "html"
}

func main() {
	if len(os.Args) != 6 {
		log.Fatal("Usage: ni input output template.html atom-template.xml url")
	}

	in := os.Args[1]
	out := os.Args[2]
	tpl := os.Args[3]
	atomTpl := os.Args[4]
	url := os.Args[5]

	b, err := os.ReadFile(tpl)
	if err != nil {
		log.Fatal(err)
	}

	PageContent = template.Must(template.New("").Parse(string(b) + tplPage))
	PageChangelog = template.Must(template.New("").Parse(string(b) + tplChangelog))

	b, err = os.ReadFile(atomTpl)
	if err != nil {
		log.Fatal(err)
	}

	atomFeed = txt.Must(txt.New("").Parse(string(b) + tplFeed))

	files, err := ioutil.ReadDir(in)
	if err != nil {
		log.Fatal(err)
	}

	var changelog []File

	for _, file := range files {
		if !filename.MatchString(file.Name()) {
			continue
		}
		file, err := os.Stat(filepath.Join(in, file.Name()))
		if err != nil {
			log.Fatal(err)
		}
		updatedAt := file.ModTime()
		changelog = append(changelog, File{
			UpdatedAt:     updatedAt,
			TimeFormatted: updatedAt.Format("2006-01-02"),
			TimeRFC3339:   updatedAt.Format(time.RFC3339),
			Name:          outputName(file.Name()),
		})
		data, err := os.ReadFile(filepath.Join(in, file.Name()))
		if err != nil {
			log.Fatal(err)
		}
		output := process(in, file.Name(), data)
		err = os.WriteFile(filepath.Join(out, outputName(file.Name())), output, 0644)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Print(".")
	}
	sort.Slice(changelog, func(i, j int) bool {
		return changelog[i].UpdatedAt.After(changelog[j].UpdatedAt)
	})
	if err != nil {
		log.Fatal(err)
	}
	err = os.WriteFile(filepath.Join(out, "changelog.html"), buildChangelog(changelog), 0644)
	if err != nil {
		log.Fatal(err)
	}
	feed := changelog
	if len(changelog) > 20 {
		feed = feed[0:20]
	}
	err = os.WriteFile(filepath.Join(out, "atom.xml"), buildAtomFeed(feed, url), 0644)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Done")
}