package main

import (
	"bytes"
	"flag"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"text/template"
	"time"

	"git.sr.ht/~adnano/go-gemini"
)

const (
	srcDir    = "src"          // site source
	dstDir    = "dst"          // site destination
	htmlDst   = "dst.html"     // html destination
	indexPath = "index.gmi"    // path used for index files
	atomPath  = "atom.xml"     // path used for atom feeds
	tmplDir   = "templates"    // templates directory
	atomTmpl  = "/atom.xml"    // path to atom template
	indexTmpl = "/index.gmi"   // path to index template
	pageTmpl  = "/page.gmi"    // path to page template
	htmlTmpl  = "/output.html" // path to html template
)

// site config
var cfg struct {
	title     string // site title
	url       string // site URL
	toAtom    bool   // output Atom
	toHTML    bool   // output HTML
	serveSite bool   // serve the site
}

func init() {
	flag.StringVar(&cfg.title, "title", "", "site title")
	flag.StringVar(&cfg.url, "url", "", "site URL")
	flag.BoolVar(&cfg.toAtom, "atom", false, "output Atom feed")
	flag.BoolVar(&cfg.toHTML, "html", false, "output HTML")
	flag.BoolVar(&cfg.serveSite, "serve", false, "serve the site")
}

func main() {
	flag.Parse()
	if err := run(); err != nil {
		log.Fatal(err)
	}
	if cfg.serveSite {
		serve()
	}
}

// site metadata passed to templates
type site struct {
	Title string
	URL   string
}

// map of paths to templates
var templates = map[string]*template.Template{}

// template functions
var funcMap = template.FuncMap{
	"site": func() site {
		return site{
			Title: cfg.title,
			URL:   cfg.url,
		}
	},
}

// loadTemplate loads a template from the provided path and content.
func loadTemplate(path string, content string) {
	tmpl := template.New(path)
	tmpl.Funcs(funcMap)
	template.Must(tmpl.Parse(content))
	templates[path] = tmpl
}

// findTemplate searches recursively for a template for the given path.
func findTemplate(path string, tmpl string) *template.Template {
	for {
		tmplPath := filepath.Join(path, tmpl)
		if t, ok := templates[tmplPath]; ok {
			return t
		}
		slash := path == "/"
		path = filepath.Dir(path)
		if slash && path == "/" {
			break
		}
	}
	// shouldn't happen
	return nil
}

func run() error {
	// Load default templates
	loadTemplate(atomTmpl, atom_xml)
	loadTemplate(indexTmpl, index_gmi)
	loadTemplate(pageTmpl, page_gmi)
	loadTemplate(htmlTmpl, output_html)
	// Load templates
	filepath.Walk(tmplDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.Mode().IsRegular() {
			b, err := ioutil.ReadFile(path)
			if err != nil {
				return err
			}
			// Remove "templates/" from beginning of path
			path = strings.TrimPrefix(path, tmplDir)
			loadTemplate(path, string(b))
		}
		return nil
	})
	// Load content
	dir := NewDir("")
	if err := dir.read(srcDir, ""); err != nil {
		return err
	}
	// Sort content
	dir.sort()
	// Manipulate content
	if err := manipulate(dir); err != nil {
		return err
	}
	if cfg.toAtom {
		if err := createFeeds(dir); err != nil {
			return err
		}
	}
	// Write content
	if err := write(dir, dstDir, outputGemini); err != nil {
		return err
	}
	if cfg.toHTML {
		if err := write(dir, htmlDst, outputHTML); err != nil {
			return err
		}
	}
	return nil
}

// serve the site
func serve() error {
	var server gemini.Server
	server.Certificates.Load("/var/lib/gemini/certs")
	server.Register("localhost", gemini.FileServer(gemini.Dir("dst")))
	return server.ListenAndServe()
}

// write writes the contents of the Index to the provided destination directory.
func write(dir *Dir, dstDir string, format outputFormat) error {
	// Empty the destination directory
	if err := os.RemoveAll(dstDir); err != nil {
		return err
	}
	// Create the destination directory
	if err := os.MkdirAll(dstDir, 0755); err != nil {
		return err
	}
	// Write the directory
	return dir.write(dstDir, format)
}

// manipulate processes and manipulates the site's content.
func manipulate(dir *Dir) error {
	// Write the directory index file, if it doesn't exist
	if dir.index == nil {
		var b bytes.Buffer
		tmpl := findTemplate(dir.Permalink, indexTmpl)
		if err := tmpl.Execute(&b, dir); err != nil {
			return err
		}
		dir.index = &Page{
			Permalink: dir.Permalink,
			content:   b.Bytes(),
		}
	}
	// Manipulate pages
	for i := range dir.Pages {
		var b bytes.Buffer
		tmpl := findTemplate(dir.Pages[i].Permalink, pageTmpl)
		if err := tmpl.Execute(&b, dir.Pages[i]); err != nil {
			return err
		}
		dir.Pages[i].content = b.Bytes()
	}
	// Manipulate subdirectories
	for _, d := range dir.Dirs {
		if err := manipulate(d); err != nil {
			return err
		}
	}
	return nil
}

// feed represents an Atom feed.
type feed struct {
	Title   string    // Feed title.
	Path    string    // Feed path.
	URL     string    // Site URL.
	Updated time.Time // Last updated time.
	Entries []*Page   // Feed entries.
}

// createFeeds creates Atom feeds.
func createFeeds(dir *Dir) error {
	var b bytes.Buffer
	tmpl := templates[atomTmpl]
	feed := &feed{
		Title:   cfg.title,
		Path:    filepath.Join(dir.Permalink, atomPath),
		URL:     cfg.url,
		Updated: time.Now(),
		Entries: dir.Pages,
	}
	if err := tmpl.Execute(&b, feed); err != nil {
		return err
	}
	path := filepath.Join(dir.Permalink, atomPath)
	dir.Files[path] = b.Bytes()
	return nil
}

// Page represents a page.
type Page struct {
	Title     string    // The title of this page.
	Permalink string    // The permalink to this page.
	Date      time.Time // The date of the page.
	content   []byte    // The content of this page.
}

// Content returns the page content as a string.
// Used in templates.
func (p *Page) Content() string {
	return string(p.content)
}

// Regexp to parse title from Gemini files
var titleRE = regexp.MustCompile("^# ?([^#\r\n]+)\r?\n?\r?\n?")

// NewPage returns a new Page with the given path and content.
func NewPage(path string, content []byte) *Page {
	// Try to parse the date from the page filename
	var date time.Time
	const layout = "2006-01-02"
	base := filepath.Base(path)
	if len(base) >= len(layout) {
		dateStr := base[:len(layout)]
		if time, err := time.Parse(layout, dateStr); err == nil {
			date = time
		}
		// Remove the date from the path
		base = base[len(layout):]
		if len(base) > 0 {
			// Remove a leading dash
			if base[0] == '-' {
				base = base[1:]
			}
			if len(base) > 0 {
				dir := filepath.Dir(path)
				if dir == "." {
					dir = ""
				}
				path = filepath.Join(dir, base)
			}
		}
	}

	// Try to parse the title from the contents
	var title string
	if submatches := titleRE.FindSubmatch(content); submatches != nil {
		title = string(submatches[1])
		// Remove the title from the contents
		content = content[len(submatches[0]):]
	}

	permalink := strings.TrimSuffix(path, ".gmi")
	return &Page{
		Permalink: "/" + permalink + "/",
		Title:     title,
		Date:      date,
		content:   content,
	}
}

// Dir represents a directory.
type Dir struct {
	Permalink string            // Permalink to this directory.
	Pages     []*Page           // Pages in this directory.
	Dirs      []*Dir            // Subdirectories.
	Files     map[string][]byte // Static files.
	index     *Page             // The index file (index.gmi).
}

// NewDir returns a new Dir with the given path.
func NewDir(path string) *Dir {
	var permalink string
	if path == "" {
		permalink = "/"
	} else {
		permalink = "/" + path + "/"
	}
	return &Dir{
		Permalink: permalink,
		Files:     map[string][]byte{},
	}
}

// read reads from a directory and indexes the files and directories within it.
func (d *Dir) read(srcDir string, path string) error {
	entries, err := ioutil.ReadDir(filepath.Join(srcDir, path))
	if err != nil {
		return err
	}
	for _, entry := range entries {
		name := entry.Name()
		// Ignore names that start with "_"
		if strings.HasPrefix(name, "_") {
			continue
		}
		path := filepath.Join(path, name)
		if entry.IsDir() {
			// Gather directory data
			dir := NewDir(path)
			if err := dir.read(srcDir, path); err != nil {
				return err
			}
			d.Dirs = append(d.Dirs, dir)
		} else {
			srcPath := filepath.Join(srcDir, path)
			content, err := ioutil.ReadFile(srcPath)
			if err != nil {
				return err
			}
			if filepath.Ext(name) == ".gmi" {
				// Gather page data
				page := NewPage(path, content)
				if name == "index.gmi" {
					d.index = page
				} else {
					d.Pages = append(d.Pages, page)
				}
			} else {
				// Static file
				d.Files[path] = content
			}
		}
	}
	return nil
}

// write writes the Dir to the provided destination path.
func (d *Dir) write(dstDir string, format outputFormat) error {
	// Create the directory
	dirPath := filepath.Join(dstDir, d.Permalink)
	if err := os.MkdirAll(dirPath, 0755); err != nil {
		return err
	}

	// Write static files
	for path := range d.Files {
		dstPath := filepath.Join(dstDir, path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		data := d.Files[path]
		if _, err := f.Write(data); err != nil {
			return err
		}
	}

	// Write the pages
	for _, page := range d.Pages {
		path, content := format(page)
		dstPath := filepath.Join(dstDir, path)
		dir := filepath.Dir(dstPath)
		os.MkdirAll(dir, 0755)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		if _, err := f.Write(content); err != nil {
			return err
		}
	}

	// Write the index file
	if d.index != nil {
		path, content := format(d.index)
		dstPath := filepath.Join(dstDir, path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		if _, err := f.Write(content); err != nil {
			return err
		}
	}

	// Write subdirectories
	for _, dir := range d.Dirs {
		dir.write(dstDir, format)
	}
	return nil
}

// sort sorts the directory's pages by date.
func (d *Dir) sort() {
	sort.Slice(d.Pages, func(i, j int) bool {
		return d.Pages[i].Date.After(d.Pages[j].Date)
	})
	// Sort subdirectories
	for _, d := range d.Dirs {
		d.sort()
	}
}

// outputFormat represents an output format.
type outputFormat func(*Page) (path string, content []byte)

func outputGemini(p *Page) (path string, content []byte) {
	path = filepath.Join(p.Permalink, indexPath)
	content = p.content
	return
}

func outputHTML(p *Page) (path string, content []byte) {
	const indexPath = "index.html"
	path = filepath.Join(p.Permalink, indexPath)

	r := bytes.NewReader(p.content)
	text := gemini.ParseText(r)
	content = []byte(textToHTML(text))

	type tmplCtx struct {
		Title   string
		Content string
	}

	var b bytes.Buffer
	tmpl := templates[htmlTmpl]
	tmpl.Execute(&b, &tmplCtx{
		Title:   p.Title,
		Content: string(content),
	})
	content = b.Bytes()
	return
}