package main

import (
	"bytes"
	"io/ioutil"
	"os"
	pathpkg "path"
	"sort"
	"strings"
	"time"
)

// Dir represents a directory.
type Dir struct {
	Title   string  // Directory title.
	Content string  // Directory index content.
	Path    string  // Directory path.
	Pages   []*Page // Pages in this directory.
	Dirs    []*Dir  // Subdirectories.
	index   *Page   // The index page.
	feed    []byte  // Atom feed.

	inputExt    string // input file extension
	outputExt   string // output file extension
	templateExt string // template file extension
}

// NewDir returns a new Dir with the given path.
func NewDir(path string) *Dir {
	if path == "" {
		path = "/"
	} else {
		path = "/" + path + "/"
	}
	return &Dir{
		Path: path,
	}
}

// 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(pathpkg.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 := pathpkg.Join(path, name)
		if entry.IsDir() {
			// Gather directory data
			dir := NewDir(path)
			dir.inputExt = d.inputExt
			dir.outputExt = d.outputExt
			dir.templateExt = d.templateExt
			if err := dir.read(srcDir, path); err != nil {
				return err
			}
			d.Dirs = append(d.Dirs, dir)
		} else {
			srcPath := pathpkg.Join(srcDir, path)
			content, err := ioutil.ReadFile(srcPath)
			if err != nil {
				return err
			}
			if ext := pathpkg.Ext(name); ext == d.inputExt {
				// Gather page data
				if strings.TrimSuffix(name, ext) == "index" {
					d.index = NewPage(d.Path, content)
					d.Title = d.index.Title
					d.Content = d.index.Content
				} else {
					d.Pages = append(d.Pages, NewPage(path, content))
				}
			}
		}
	}
	return nil
}

// manipulate processes and manipulates the directory's contents.
func (d *Dir) manipulate(cfg *Config) error {
	if d.templateExt != "" {
		// Create index
		if d.index != nil {
			var b strings.Builder
			tmpl := cfg.Templates.FindTemplate(d.Path, "index"+d.templateExt)
			if err := tmpl.Execute(&b, d); err != nil {
				return err
			}
			d.index.Content = b.String()
		}

		// Manipulate pages
		for i := range d.Pages {
			var b strings.Builder
			tmpl := cfg.Templates.FindTemplate(d.Path, "page"+d.templateExt)
			if err := tmpl.Execute(&b, d.Pages[i]); err != nil {
				return err
			}
			d.Pages[i].Content = b.String()
		}
	}

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

	// Create feeds
	if title, ok := cfg.Feeds[d.Path]; ok {
		var b bytes.Buffer
		feed := &Feed{
			Title:   title,
			Path:    d.Path,
			Updated: time.Now(),
			Entries: d.Pages,
		}
		tmpl := cfg.Templates.FindTemplate(d.Path, "atom.xml")
		if err := tmpl.Execute(&b, feed); err != nil {
			return err
		}
		d.feed = b.Bytes()
	}

	// Manipulate subdirectories
	for _, d := range d.Dirs {
		if err := d.manipulate(cfg); err != nil {
			return err
		}
	}
	return nil
}

// Format represents an output format.
type Format interface {
	Format(*Page) (path string, content []byte)
}

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

	// Write pages
	for _, page := range d.Pages {
		path, content := format.Format(page)
		dstPath := pathpkg.Join(dstDir, path)
		dir := pathpkg.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.Format(d.index)
		dstPath := pathpkg.Join(dstDir, path)
		dir := pathpkg.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 atom feed
	if d.feed != nil {
		const path = "atom.xml"
		dstPath := pathpkg.Join(dstDir, path)
		os.MkdirAll(dstDir, 0755)
		f, err := os.Create(dstPath)
		if err != nil {
			return err
		}
		if _, err := f.Write(d.feed); 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()
	}
}