package main

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"path"
	"path/filepath"
	"slices"
	"strings"
	"time"

	"github.com/PuerkitoBio/goquery"
	"github.com/adrg/frontmatter"
	mapset "github.com/deckarep/golang-set/v2"
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/extension"
)

type PostMatter struct {
	Date        time.Time `toml:"date"`
	Description string    `toml:"description"`
	Title       string    `toml:"title"`
	Taxonomies  struct {
		Tags []string `toml:"tags"`
	} `toml:"taxonomies"`
}

type Post struct {
	Input    string
	Output   string
	Basename string
	URL      string
	Content  string
	PostMatter
}

type Tags mapset.Set[string]

func check(err error) {
	if err != nil {
		log.Panic(err)
	}
}

func getPost(filename string) (PostMatter, []byte) {
	matter := PostMatter{}
	content, err := os.Open(filename)
	check(err)
	rest, err := frontmatter.Parse(content, &matter)
	check(err)

	return matter, rest
}

func readPosts(root string, inputDir string, outputDir string) ([]Post, Tags) {
	tags := mapset.NewSet[string]()
	posts := []Post{}
	subdir := filepath.Join(root, inputDir)
	files, err := os.ReadDir(subdir)
	outputReplacer := strings.NewReplacer(root, outputDir, ".md", "/index.html")
	urlReplacer := strings.NewReplacer(root, "", ".md", "/")
	check(err)
	md := goldmark.New(
		goldmark.WithExtensions(
			extension.GFM,
			extension.Footnote,
			extension.Typographer,
		),
	)
	for _, f := range files {
		pathFromRoot := filepath.Join(subdir, f.Name())
		check(err)
		if !f.IsDir() && path.Ext(pathFromRoot) == ".md" {
			output := outputReplacer.Replace(pathFromRoot)
			url := urlReplacer.Replace(pathFromRoot)
			matter, content := getPost(pathFromRoot)

			for _, tag := range matter.Taxonomies.Tags {
				tags.Add(strings.ToLower(tag))
			}

			var buf bytes.Buffer
			err := md.Convert(content, &buf)
			check(err)
			post := Post{
				Input:      pathFromRoot,
				Output:     output,
				Basename:   filepath.Base(url),
				URL:        url,
				PostMatter: matter,
				Content:    buf.String(),
			}

			posts = append(posts, post)
		}
	}
	slices.SortFunc(posts, func(a, b Post) int {
		return b.Date.Compare(a.Date)
	})
	return posts, tags
}

func layout(html string, config Config, pageTitle string) *goquery.Document {
	css, err := os.ReadFile("templates/style.css")
	check(err)
	doc, err := goquery.NewDocumentFromReader(strings.NewReader(html))
	check(err)
	doc.Find("html").SetAttr("lang", config.DefaultLanguage)
	doc.Find("head > link[rel=alternate]").Add(".title").SetAttr("title", config.Title)
	doc.Find("title").Add(".p-name").SetText(pageTitle)
	doc.Find("head > style").SetText(string(css))
	nav := doc.Find("nav")
	navLink := doc.Find("nav a")
	nav.Empty()
	for _, link := range config.Menus["main"] {
		nav.AppendSelection(navLink.Clone().SetAttr("href", link.URL).SetText(link.Name))
	}
	return doc
}

func renderPost(post Post, config Config) string {
	tbytes, err := os.ReadFile("templates/post.html")
	check(err)
	doc := layout(string(tbytes), config, post.PostMatter.Title)
	doc.Find(".title").AddClass("h-card p-author").SetAttr("rel", "author")
	datetime, err := post.PostMatter.Date.MarshalText()
	check(err)
	doc.Find(".h-entry .dt-published").SetAttr("datetime", string(datetime)).SetText(
		post.PostMatter.Date.Format("2006-01-02"),
	)
	doc.Find(".h-entry .e-content").SetHtml(post.Content)
	categories := doc.Find(".h-entry .p-categories")
	cat := categories.Find(".p-category").ParentsUntilSelection(categories)
	cat.Remove()
	for _, tag := range post.Taxonomies.Tags {
		categories.AppendSelection(cat.Clone().Find(".p-category").SetAttr("href", fmt.Sprintf("/tags/%s/", tag)).SetText("#" + tag)).Parent()
	}
	html, err := doc.Html()
	check(err)
	return html
}

func renderTags(tags Tags, config Config) string {
	tbytes, err := os.ReadFile("templates/tags.html")
	check(err)

	doc := layout(string(tbytes), config, config.Title)
	tagList := doc.Find(".tags")
	tpl := doc.Find(".h-feed")
	tpl.Remove()
	for _, tag := range mapset.Sorted(tags) {
		tagList.AppendSelection(
			tpl.Clone().SetAttr("href", fmt.Sprintf("/tags/%s/", tag)).SetText("#" + tag),
		)
	}
	html, err := doc.Html()
	check(err)
	return html
}

func renderListPage(tag string, config Config, posts []Post) string {
	tbytes, err := os.ReadFile("templates/list.html")
	check(err)
	var title string
	if len(tag) > 0 {
		title = tag
	} else {
		title = config.Title
	}
	doc := layout(string(tbytes), config, title)
	feed := doc.Find(".h-feed")
	tpl := feed.Find(".h-entry")
	tpl.Remove()

	doc.Find(".title").AddClass("h-card p-author").SetAttr("rel", "author")
	if tag == "" {
		doc.Find(".filter").Remove()
	} else {
		doc.Find(".filter").Find("h3").SetText("#" + tag)
	}

	for _, post := range posts {
		entry := tpl.Clone()
		datetime, err := post.PostMatter.Date.MarshalText()
		check(err)

		entry.Find(".p-name").SetText(post.Title).SetAttr("href", post.URL)
		entry.Find(".dt-published").SetAttr("datetime", string(datetime)).SetText(post.PostMatter.Date.Format("2006-01-02"))
		feed.AppendSelection(entry)
	}

	html, err := doc.Html()
	check(err)
	return html
}

func main() {
	config := getConfig()
	err := os.MkdirAll("public/post", 0755)
	check(err)
	log.Print("Generating site...")
	posts, tags := readPosts("content", "post", "public")
	for _, post := range posts {
		err := os.MkdirAll(path.Join("public", "post", post.Basename), 0755)
		check(err)
		// output := renderPost(post, config)
		// err = os.WriteFile(post.Output, []byte(output), 0755)
		// check(err)
	}
	err = os.MkdirAll("public/tags", 0755)
	check(err)
	// fmt.Printf("%+v\n", renderTags(tags, config))
	// err = os.WriteFile("public/tags/index.html", []byte(renderTags(tags, config)), 0755)
	// check(err)
	for _, tag := range tags.ToSlice() {
		matchingPosts := []Post{}
		for _, post := range posts {
			if slices.Contains(post.Taxonomies.Tags, tag) {
				matchingPosts = append(matchingPosts, post)
			}
		}
		err := os.MkdirAll(path.Join("public", "tags", tag), 0755)
		check(err)
		// tagPage := renderListPage(tag, config, matchingPosts)
		// fmt.Printf("%+v\n", tagPage)
		// err = os.WriteFile(path.Join("public", "tags", tag, "index.html"), []byte(tagPage), 0755)
		// check(err)

		// TODO: tag atom

		fmt.Printf("%+v\n", renderListPage("", config, posts))

		// TODO: atom

		// TODO: renderFeedStyles

		// TODO: renderHomepage

		// TODO: render404Page
	}

	fmt.Printf("%+v\n", tags)
}