website/articles.go

package main

import (
	"bytes"
	"fmt"
	"os"
	"path"
	"sort"
	"strings"
	"time"

	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/renderer/html"
	"github.com/yuin/goldmark/util"

	chromahtml "github.com/alecthomas/chroma/formatters/html"
	mathjax "github.com/litao91/goldmark-mathjax"
	highlighting "github.com/yuin/goldmark-highlighting"

	"gopkg.in/yaml.v3"
)

var md goldmark.Markdown

// https://github.com/yuin/goldmark-highlighting/blob/9216f9c5aa010c549cc9fc92bb2593ab299f90d4/highlighting_test.go#L27
func customCodeBlockWrapper(w util.BufWriter, c highlighting.CodeBlockContext, entering bool) {
	lang, ok := c.Language()
	if entering {
		if ok {
			w.WriteString(fmt.Sprintf(`<pre class="%s"><code>`, lang))
			return
		}
		w.WriteString("<pre><code>")
	} else {
		if ok {
			w.WriteString("</pre></code>")
			return
		}
		w.WriteString("</pre></code>")
	}
}

func init() {
	md = goldmark.New(
		goldmark.WithExtensions(
			extension.GFM,
			extension.Typographer,
			// Questo pacchetto ha un nome stupido perché in realtà si occupa solo del parsing lato server del Markdown mentre lato client usiamo KaTeX.
			mathjax.NewMathJax(),
			highlighting.NewHighlighting(
				highlighting.WithStyle("github"),
				highlighting.WithWrapperRenderer(customCodeBlockWrapper),
				highlighting.WithFormatOptions(
					chromahtml.PreventSurroundingPre(true),
				),
			),
		),
		goldmark.WithParserOptions(
			parser.WithAutoHeadingID(),
		),
		goldmark.WithRendererOptions(
			html.WithHardWraps(),
			html.WithXHTML(),
		),
	)
}

type ArticleFrontMatter struct {
	Title       string `yaml:"title"`
	Description string `yaml:"description"`
	Tags        string `yaml:"tags"`
	PublishDate string `yaml:"publish_date"`
}

type Article struct {
	Id          string
	Title       string
	Description string
	Tags        []string
	PublishDate time.Time

	MarkdownSource string
	renderedHTML   string
}

func (article *Article) HasTag(tag string) bool {
	for _, t := range article.Tags {
		if t == tag {
			return true
		}
	}

	return false
}

func (article *Article) Render() (string, error) {
	if article.renderedHTML == "" {
		var buf bytes.Buffer
		if err := md.Convert([]byte(article.MarkdownSource), &buf); err != nil {
			return "", err
		}

		article.renderedHTML = buf.String()
	}

	return article.renderedHTML, nil
}

type ArticleRenderer struct {
	RootPath string
}

func trimAll(vs []string) []string {
	r := []string{}
	for _, v := range vs {
		r = append(r, strings.TrimSpace(v))
	}
	return r
}

func removeBlanks(v []string) []string {
	r := []string{}

	for _, s := range v {
		if len(strings.TrimSpace(s)) > 0 {
			r = append(r, s)
		}
	}

	return r
}

func (registry *ArticleRenderer) Load(articlePath string) (*Article, error) {
	fileBytes, err := os.ReadFile(path.Join(registry.RootPath, articlePath+".md"))
	if err != nil {
		return nil, err
	}

	source := string(fileBytes)

	// TODO: Ehm bugia esiste "https://github.com/yuin/goldmark-meta" però boh per ora funge tutto
	parts := removeBlanks(strings.Split(source, "---"))

	frontMatterSource := parts[0]
	markdownSource := strings.Join(parts[1:], "---")

	var frontMatter ArticleFrontMatter
	if err := yaml.Unmarshal([]byte(frontMatterSource), &frontMatter); err != nil {
		return nil, err
	}

	publishDate, err := time.Parse("2006/01/02 15:04", frontMatter.PublishDate)
	if err != nil {
		return nil, err
	}

	tags := trimAll(strings.Split(frontMatter.Tags, ","))

	article := &Article{
		Id:             articlePath,
		Title:          frontMatter.Title,
		Description:    frontMatter.Description,
		Tags:           tags,
		PublishDate:    publishDate,
		MarkdownSource: markdownSource,
	}

	return article, nil
}

func (registry *ArticleRenderer) LoadAll() ([]*Article, error) {
	entries, err := os.ReadDir(registry.RootPath)
	if err != nil {
		return nil, err
	}

	articles := []*Article{}

	for _, entry := range entries {
		if !entry.IsDir() {
			name := strings.TrimRight(entry.Name(), ".md")
			article, err := registry.Load(name)
			if err != nil {
				return nil, err
			}

			articles = append(articles, article)
		}
	}

	sort.Slice(articles, func(i, j int) bool {
		return articles[i].PublishDate.After(articles[j].PublishDate)
	})

	return articles, nil
}

func NewArticleRenderer(rootPath string) *ArticleRenderer {
	return &ArticleRenderer{
		rootPath,
	}
}