package main

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

	"github.com/adrg/frontmatter"
	mapset "github.com/deckarep/golang-set/v2"
)

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

	return matter, string(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)
	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))
			}

			post := Post{
				Input:      pathFromRoot,
				Output:     output,
				Basename:   filepath.Base(url),
				URL:        url,
				PostMatter: matter,
				Content:    content,
			}

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

func main() {
	err := os.MkdirAll("public/post", 755)
	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), 755)
		check(err)
		fmt.Printf("%+v\n", post.Date)
	}
	fmt.Printf("%+v\n", tags)
}