package main

import (
	"io/ioutil"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"text/template"
	"time"
)

type Site struct {
	Static    map[string][]byte  // Static files
	Directory *Directory         // Site directory
	Templates *template.Template // Templates
}

// LoadSite loads and returns a Site.
// It reads site content from the specified source directory.
func LoadSite(srcDir string) (*Site, error) {
	tmpl, err := template.New("templates").ParseGlob("templates/*.gmi")
	if err != nil {
		return nil, err
	}

	site := &Site{
		Static:    map[string][]byte{},
		Directory: NewDirectory(""),
		Templates: tmpl,
	}

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

	return site, nil
}

// Write writes the contents of the Index to the provided destination directory.
func (s *Site) Write(dstDir string) 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 static files
	for path := range s.Static {
		// Create any parent directories
		if dir := filepath.Dir(path); dir != "." {
			dstPath := filepath.Join(dstDir, dir)
			if err := os.MkdirAll(dstPath, 0755); err != nil {
				return err
			}
		}

		// Write the file
		dstPath := filepath.Join(dstDir, path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		data := s.Static[path]
		if _, err := f.Write(data); err != nil {
			return err
		}
	}

	// Write the directory
	return s.Directory.Write(dstDir)
}

// 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.Path, "index.gmi")
		builder := &strings.Builder{}
		tmpl := s.Templates.Lookup("directory.gmi")
		if err := tmpl.Execute(builder, dir); err != nil {
			return err
		}
		content := builder.String()
		permalink := filepath.Dir(path)
		if permalink == "." {
			permalink = ""
		}
		page := &Page{
			Path:      path,
			Permalink: "/" + permalink,
			Content:   content,
		}
		dir.Index = page
	}

	// Manipulate pages
	for i := range dir.Pages {
		builder := &strings.Builder{}
		tmpl := s.Templates.Lookup("page.gmi")
		if err := tmpl.Execute(builder, dir.Pages[i]); err != nil {
			return err
		}
		dir.Pages[i].Content = builder.String()
	}

	return nil
}

// Page represents a page.
type Page struct {
	// The path to this page.
	Path string
	// 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 string
}

var titleRE = regexp.MustCompile("^# ?([^#\r\n]+)\r?\n?\r?\n?")

func NewPage(path string, content string) *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.FindStringSubmatch(content); submatches != nil {
		title = submatches[1]
		// Remove the title from the contents
		content = content[len(submatches[0]):]
	}

	return &Page{
		Path:      path,
		Permalink: "/" + path,
		Title:     title,
		Date:      date,
		Content:   content,
	}
}

// Directory represents a directory of pages.
type Directory struct {
	// The path to this directory.
	Path string
	// 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
}

// NewSection returns a new Section with the given path.
func NewDirectory(path string) *Directory {
	var permalink string
	if path == "" {
		permalink = "/"
	} else {
		permalink = "/" + path + "/"
	}
	return &Directory{
		Path:      path,
		Permalink: permalink,
	}
}

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

	for _, entry := range entries {
		name := entry.Name()
		path := filepath.Join(path, name)
		srcPath := filepath.Join(srcDir, path)

		if entry.IsDir() {
			// Gather directory data
			dir := NewDirectory(path)
			dir.Read(site, srcPath, path)
			d.Directories = append(d.Directories, dir)
		} else {
			content, err := ioutil.ReadFile(srcPath)
			if err != nil {
				return err
			}

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

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

			default:
				// Static file
				site.Static[path] = content
			}
		}
	}
	return nil
}

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

	// Write the files
	for _, page := range d.Pages {
		dstPath := filepath.Join(dstDir, page.Path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		data := []byte(page.Content)
		if _, err := f.Write(data); err != nil {
			return err
		}
	}

	// Write the index file
	if d.Index != nil {
		dstPath := filepath.Join(dstDir, d.Index.Path)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		data := []byte(d.Index.Content)
		if _, err := f.Write(data); err != nil {
			return err
		}
	}

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