package post

import (
	"html/template"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"go.jolheiser.com/blog/markdown"

	"github.com/fsnotify/fsnotify"
	"github.com/rs/zerolog/log"
	"go.jolheiser.com/emdbed"
)

func NewBlog(basePath string) (*Blog, error) {
	posts, err := scan(basePath)
	if err != nil {
		return nil, err
	}

	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}
	if err := watcher.Add(basePath); err != nil {
		return nil, err
	}

	b := &Blog{
		Path:  basePath,
		posts: posts,
	}

	go func() {
		var debounce time.Time
		for {
			select {
			case event := <-watcher.Events:
				log.Debug().Str("op", event.Op.String()).Msgf("fsnotify %q", event.Name)
				debounce = time.Now()
			case err := <-watcher.Errors:
				log.Err(err).Msg("")
			default:
				if !debounce.IsZero() && time.Since(debounce) > (time.Second*5) {
					log.Info().Msg("reloading blog")
					if err := b.Scan(); err != nil {
						log.Err(err).Msg("")
					}
					debounce = time.Time{}
				}
			}
		}
	}()

	return b, nil
}

func scan(basePath string) (map[string]*Post, error) {
	posts := make(map[string]*Post)
	ents, err := os.ReadDir(basePath)
	if err != nil {
		return nil, err
	}
	for _, ent := range ents {
		var apn string
		if ent.IsDir() {
			apn = filepath.Join(basePath, ent.Name(), "index.md")
			if _, err := os.Stat(apn); err != nil {
				log.Error().Err(err).Msgf("could not parse %s", ent.Name())
				continue
			}
		} else {
			if !strings.HasSuffix(ent.Name(), ".md") {
				continue
			}
			apn = filepath.Join(basePath, ent.Name())
		}

		fi, err := os.Open(apn)
		if err != nil {
			log.Error().Err(err).Msg("could not open file")
			continue
		}
		post := &Post{Path: apn, Slug: strings.TrimSuffix(ent.Name(), ".md")}
		if err := markdown.Meta(fi, &post); err != nil {
			log.Error().Err(err).Msg("could not extract meta")
			continue
		}
		posts[post.Slug] = post

		if err := fi.Close(); err != nil {
			log.Error().Err(err).Msg("could not close file")
			continue
		}

		if err := post.Load(); err != nil {
			log.Err(err).Msg("could not load post")
			continue
		}
	}
	return posts, nil
}

type Blog struct {
	Path  string
	posts map[string]*Post
	mx    sync.RWMutex
}

func (b *Blog) Scan() error {
	posts, err := scan(b.Path)
	if err != nil {
		return err
	}
	b.mx.Lock()
	defer b.mx.Unlock()
	b.posts = posts
	return nil
}

func (b *Blog) SortedPosts() []*Post {
	posts := make([]*Post, 0, len(b.posts))
	for _, post := range b.posts {
		posts = append(posts, post)
	}
	sort.Slice(posts, func(i, j int) bool {
		return posts[i].Date.After(posts[j].Date)
	})
	return posts
}

func (b *Blog) Post(name string) (*Post, bool) {
	b.mx.RLock()
	defer b.mx.RUnlock()
	if post, ok := b.posts[name]; ok {
		return post, true
	}
	return nil, false
}

type Post struct {
	Path    string        `toml:"-"`
	Slug    string        `toml:"-"`
	Content template.HTML `toml:"-"`
	Title   string        `toml:"title"`
	Author  string        `toml:"author"`
	Date    time.Time     `toml:"date"`
	Tags    []string      `toml:"tags"`
}

func (p *Post) Load() error {
	fi, err := os.Open(p.Path)
	if err != nil {
		return err
	}
	defer fi.Close()

	mdContent, err := markdown.Content(fi)
	if err != nil {
		return err
	}

	emdbedContent, err := emdbed.Convert(filepath.Dir(p.Path), strings.NewReader(mdContent))
	if err != nil {
		return err
	}

	md, err := markdown.Convert(strings.NewReader(emdbedContent))
	if err != nil {
		return err
	}

	p.Content = template.HTML(md)
	return nil
}