package main

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

	"git.sr.ht/~adnano/gmi"
)

// Site represents a kiln site.
type Site struct {
	URL       string             // Site URL
	Directory *Directory         // Site directory
	Templates *template.Template // Templates
}

// Load loads the Site from the specified source directory.
func (s *Site) Load(srcDir string) error {
	s.Directory = NewDirectory("")

	tmpl, err := template.New("templates").ParseGlob("templates/*.gmi")
	if err != nil {
		return err
	}
	s.Templates = tmpl

	if err := site.Directory.Read(""); err != nil {
		return err
	}
	return nil
}

// Write writes the contents of the Index to the provided destination directory.
func (s *Site) Write(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 s.Directory.Write(dstDir, format)
}

// Manipulate processes and manipulates the site's content.
func (s *Site) Manipulate(dir *Directory) error {
	// Write the directory index file, if it doesn't exist
	if dir.Index == nil {
		path := filepath.Join(dir.Permalink, "index.gmi")
		var b bytes.Buffer
		tmpl := s.Templates.Lookup("index.gmi")
		if tmpl == nil {
			tmpl = indexTmpl
		}
		if err := tmpl.Execute(&b, dir); err != nil {
			return err
		}
		content := b.Bytes()
		permalink := filepath.Dir(path)
		if permalink == "." {
			permalink = ""
		}
		page := &Page{
			Permalink: "/" + permalink,
			content:   content,
		}
		dir.Index = page
	}

	// Manipulate pages
	for i := range dir.Pages {
		var b bytes.Buffer
		tmpl := s.Templates.Lookup("page.gmi")
		if tmpl == nil {
			tmpl = pageTmpl
		}
		if err := tmpl.Execute(&b, dir.Pages[i]); err != nil {
			return err
		}
		dir.Pages[i].content = b.Bytes()
	}

	return nil
}

// Sort sorts the site's pages by date.
func (s *Site) Sort() {
	s.Directory.Sort()
}

type Feed struct {
	Title   string
	Path    string
	SiteURL string
	Updated time.Time
	Entries []*Page
}

// CreateFeeds creates Atom feeds.
func (s *Site) CreateFeeds() error {
	const atomPath = "atom.xml"
	var b bytes.Buffer
	tmpl := s.Templates.Lookup(atomPath)
	if tmpl == nil {
		tmpl = atomTmpl
	}
	feed := &Feed{
		Title:   "Example Feed",
		Path:    filepath.Join(s.Directory.Permalink, atomPath),
		SiteURL: s.URL,
		Updated: time.Now(),
		Entries: s.Directory.Pages,
	}
	if err := tmpl.Execute(&b, feed); err != nil {
		return err
	}
	path := filepath.Join(s.Directory.Permalink, atomPath)
	s.Directory.Static[path] = b.Bytes()
	return nil
}

// Page represents a page.
type Page struct {
	// The permalink to this page.
	Permalink string
	// The title of this page, parsed from the Gemini contents.
	Title string
	// The date of the page. Dates are specified in the filename.
	// Ex: 2020-09-22-hello-world.gmi
	Date time.Time
	// The content of this page.
	content []byte
}

func (p *Page) Content() string {
	return string(p.content)
}

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,
	}
}

// Directory represents a directory of pages.
type Directory struct {
	// The permalink to this directory.
	Permalink string
	// The pages in this directory.
	Pages []*Page
	// The subdirectories of this directory.
	Directories []*Directory
	// The index file (index.gmi).
	Index *Page
	// Static files
	Static map[string][]byte
}

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

// Read reads from a directory and indexes the files and directories within it.
func (d *Directory) Read(path string) error {
	entries, err := ioutil.ReadDir(filepath.Join("src", path))
	if err != nil {
		return err
	}

	for _, entry := range entries {
		name := entry.Name()
		if entry.IsDir() {
			// Gather directory data
			path := filepath.Join(path, name)
			dir := NewDirectory(path)
			if err := dir.Read(path); err != nil {
				return err
			}
			d.Directories = append(d.Directories, dir)
		} else {
			srcPath := filepath.Join("src", path, name)
			content, err := ioutil.ReadFile(srcPath)
			if err != nil {
				return err
			}

			switch filepath.Ext(name) {
			case ".gmi", ".gemini":
				path := filepath.Join(path, name)
				// Gather page data
				page := NewPage(path, content)

				if name == "index.gmi" {
					d.Index = page
				} else {
					d.Pages = append(d.Pages, page)
				}

			default:
				// Static file
				path := filepath.Join(path, name)
				d.Static[path] = content
			}
		}
	}
	return nil
}

// Write writes the Directory to the provided destination path.
func (d *Directory) 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.Static {
		dstPath := filepath.Join(dstDir, path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		data := d.Static[path]
		if _, err := f.Write(data); err != nil {
			return err
		}
	}

	// Write the files
	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.Directories {
		dir.Write(dstDir, format)
	}
	return nil
}

// Sort sorts the directory's pages by date.
func (d *Directory) 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.Directories {
		d.Sort()
	}
}

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

func OutputGemini(p *Page) (path string, content []byte) {
	const indexPath = "index.gmi"
	path = filepath.Join(p.Permalink, indexPath)
	content = p.content
	return
}

func OutputHTML(p *Page) (path string, content []byte) {
	const indexPath = "index.html"
	const meta = `<!DOCTYPE html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<link rel="stylesheet" href="/style.css">
<title>%s</title>

`

	path = filepath.Join(p.Permalink, indexPath)

	var b bytes.Buffer
	fmt.Fprintf(&b, meta, html.EscapeString(p.Title))

	var pre bool
	var list bool
	r := bytes.NewReader(p.content)
	text := gmi.Parse(r)
	for _, l := range text {
		if _, ok := l.(gmi.LineListItem); ok {
			if !list {
				list = true
				fmt.Fprint(&b, "<ul>\n")
			}
		} else if list {
			list = false
			fmt.Fprint(&b, "</ul>\n")
		}
		switch l.(type) {
		case gmi.LineLink:
			link := l.(gmi.LineLink)
			url := html.EscapeString(link.URL)
			name := html.EscapeString(link.Name)
			if name == "" {
				name = url
			}
			fmt.Fprintf(&b, "<p><a href='%s'>%s</a></p>\n", url, name)
		case gmi.LinePreformattingToggle:
			pre = !pre
			if pre {
				fmt.Fprint(&b, "<pre>\n")
			} else {
				fmt.Fprint(&b, "</pre>\n")
			}
		case gmi.LinePreformattedText:
			text := string(l.(gmi.LinePreformattedText))
			fmt.Fprintf(&b, "%s\n", html.EscapeString(text))
		case gmi.LineHeading1:
			text := string(l.(gmi.LineHeading1))
			fmt.Fprintf(&b, "<h1>%s</h1>\n", html.EscapeString(text))
		case gmi.LineHeading2:
			text := string(l.(gmi.LineHeading2))
			fmt.Fprintf(&b, "<h2>%s</h2>\n", html.EscapeString(text))
		case gmi.LineHeading3:
			text := string(l.(gmi.LineHeading3))
			fmt.Fprintf(&b, "<h3>%s</h3>\n", html.EscapeString(text))
		case gmi.LineListItem:
			text := string(l.(gmi.LineListItem))
			fmt.Fprintf(&b, "<li>%s</li>\n", html.EscapeString(text))
		case gmi.LineQuote:
			text := string(l.(gmi.LineQuote))
			fmt.Fprintf(&b, "<blockquote>%s</blockquote>\n", html.EscapeString(text))
		case gmi.LineText:
			text := string(l.(gmi.LineText))
			if text == "" {
				fmt.Fprint(&b, "<br>\n")
			} else {
				fmt.Fprintf(&b, "<p>%s</p>\n", html.EscapeString(text))
			}
		}
	}
	if pre {
		fmt.Fprint(&b, "</pre>\n")
	}
	if list {
		fmt.Fprint(&b, "</ul>\n")
	}
	content = b.Bytes()
	return
}