article.go

package main

import (
	"errors"
	"fmt"
	"html/template"
	"net/http"
	"regexp"
)

func newArticleHandler(s storage, tmpl *template.Template) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		handleArticle(w, r, s, tmpl)
	})
}

func handleArticle(w http.ResponseWriter, r *http.Request, s storage, tmpl *template.Template) {
	if r.Method == "POST" {
		postArticle(w, r, s, tmpl)
	} else if r.Method == "GET" {
		getArticle(w, r, s, tmpl)
	} else {
		renderError(w, tmpl, fmt.Errorf("method must be POST or GET"))
	}
}

func postArticle(w http.ResponseWriter, r *http.Request, s storage, tmpl *template.Template) {
	title, err := articleTitle(r)
	if err != nil {
		renderError(w, tmpl, err)
		return
	}

	err = r.ParseForm()
	if err != nil {
		renderError(w, tmpl, fmt.Errorf("could not parse form values: %w", err))
		return
	}

	content := r.Form.Get("content")

	err = checkmd([]byte(content))
	if err != nil {
		renderError(w, tmpl, fmt.Errorf("article not saved: %w", err))
	}

	err = s.WriteArticle(title, []byte(content))
	if err != nil {
		renderError(w, tmpl, fmt.Errorf("could not write article content:  %w", err))
		return
	}

	http.Redirect(w, r, r.URL.Path, http.StatusFound)
}

type articleView struct {
	Title   string
	Content template.HTML
}

type editArticleView struct {
	Title   string
	Content string
}

func getArticle(w http.ResponseWriter, r *http.Request, s storage, tmpl *template.Template) {
	title, err := articleTitle(r)
	if err != nil {
		renderError(w, tmpl, err)
		return
	}

	content, err := s.ReadArticle(title)
	if errors.Is(err, errArticleDNE) {
		render(w, tmpl, "article_dne.tmpl", articleView{Title: title})
		return
	} else if err != nil {
		renderError(w, tmpl, fmt.Errorf("could not read article: %w", err))
		return
	}

	if r.URL.Query().Get("raw") == "true" {
		w.Write(content)
		return
	}

	if r.URL.Query().Get("edit") == "true" {
		render(
			w,
			tmpl,
			"edit_article.tmpl",
			editArticleView{
				Title:   title,
				Content: string(content),
			},
		)

		return
	}

	contentHTML, err := md2html(content)
	if err != nil {
		renderError(w, tmpl, err)
	}

	render(
		w,
		tmpl,
		"show_article.tmpl",
		articleView{
			Title:   title,
			Content: contentHTML,
		},
	)
}

var articlePathMatcher = regexp.MustCompile(`^/articles/([0-9a-zA-Z_]+)$`)

func articleTitle(r *http.Request) (string, error) {
	matches := articlePathMatcher.FindStringSubmatch(r.URL.Path)
	if matches == nil {
		return "", fmt.Errorf("invalid article URL")
	}

	return matches[1], nil
}