oEmbed API for blog.petitviolet.net

route.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"regexp"
	"strings"

	"github.com/mattn/go-jsonpointer"
)

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hello, World")
}
func main() {

	host := "0.0.0.0"
	port := os.Getenv("PORT")
	if port == "" {
		// local
		port = "8080"
		host = "127.0.0.1"
	}

	http.HandleFunc("/oembed", oEmbedHandler)
	http.HandleFunc("/", handler)
	log.Printf("Listening on port %s:%s", host, port)
	log.Fatal(http.ListenAndServe(fmt.Sprintf("%s:%s", host, port), nil))
}

func oEmbedHandler(w http.ResponseWriter, r *http.Request) {
	log.Printf("Handle HTTP request %s\n", r.URL)
	target := r.URL.Query()["url"][0]
	data, err := newOEmbedData(target)
	if err != nil {
		body, _ := json.Marshal(map[string]string{"error": err.Error()})
		w.WriteHeader(http.StatusNotFound)
		w.Header().Set("Content-Type", "application/json")
		w.Write(body)
	} else {
		body, _ := json.Marshal(data)
		w.Header().Set("Content-Type", "application/json")
		w.Write(body)
	}
}

type oEmbedData struct {
	Url          string   `json:"url"`
	Title        string   `json:"title"`
	Tags         []string `json:"tags"`
	Description  string   `json:"description"`
	Html         string   `json:"html"`
	Published    string   `json:"published"`
	BlogUrl      string   `json:"blog_url"`
	BlogTitle    string   `json:"blog_title"`
	AuthorUrl    string   `json:"author_url"`
	AuthorName   string   `json:"author_name"`
	ProviderName string   `json:"provider_name"`
	ProviderUrl  string   `json:"provider_url"`
	ImageUrl     string   `json:"image_url"`
	Width        string   `json:"width"`
	Height       string   `json:"height"`
	Version      string   `json:"version"`
	Type         string   `json:"type"`
}

func newOEmbedData(url string) (*oEmbedData, error) {
	post, err := findPost(url)
	if err != nil {
		log.Println(err.Error())
		return nil, err
	}
	oEmbedData := oEmbedData{
		Url:          url,
		Title:        post.Title,
		Description:  post.Description,
		Tags:         post.Tags,
		Published:    post.Date,
		Html:         buildHtml(url, post),
		BlogUrl:      "https://blog.petitviolet.net",
		BlogTitle:    "blog.petitviolet.net",
		AuthorUrl:    "https://petitviolet.net",
		AuthorName:   "petitviolet",
		ProviderName: "blog.petitviolet.net",
		ProviderUrl:  "https://blog.petitviolet.net",
		ImageUrl:     "https://s.gravatar.com/avatar/93bc8fb48f57c11e417dad9d26a2fb8a?s=480",
		Width:        "100%",
		Height:       "200px",
		Version:      "1.0",
		Type:         "rich",
	}

	return &oEmbedData, nil
}

type Post struct {
	Title       string
	Tags        []string
	Description string
	Excerpt     string
	Date        string
}

var urlPattern = regexp.MustCompile(`^https://blog.petitviolet.net/post/(\d{4}-\d{2}-\d{2})/(.+)$`)

func findPost(url string) (*Post, error) {
	res := urlPattern.FindStringSubmatch(url)
	if len(res) != 3 {
		return nil, fmt.Errorf("Invalid url. url: %s", url)
	}
	pageDataPath := buildPageDatePath(res[1], res[2])
	raw, err := ioutil.ReadFile(pageDataPath)
	if err != nil {
		err = fmt.Errorf("Failed to read file. file = %s, err = %s", pageDataPath, err.Error())
		return nil, err
	}
	return buildPost(raw), nil
}

func buildHtml(url string, post *Post) string {
	id := strings.Replace(post.Title, " ", "-", -1)
	return fmt.Sprintf(`
    <style type="text/css">
		  #oembed-container-%s {
				border: 1px solid #AAA;
				padding: 0.4em 1em 0.4em 1em;
				display: flex;
				flex-direction: column;
				box-shadow: 0px 0px 2px 2px rgba(100, 100, 100, 0.1);
				width: 80%%;
				color: #000;
				background-color: #FEFEFE;
			}
			#oembed-body-%s {
				display: flex;
				flex-direction: column;
				align-content: space-between;
			}
			#oembed-body-link-%s {
				text-decoration: underline;
				color: #5555FF;
				font-size: 18px;
				font-weight: 700;
			}
			#oembed-body-description-%s {
				font-weight: 500;
				font-size: 16px;
			}
			#oembed-body-excerpt-%s {
				font-size: 10px;
				color: #444;
			}
			#oembed-footer-%s {
				display: flex;
				margin-top: 8px;
				align-items: center;
			}
			#oembed-footer-logo-%s {
				margin-left: 0;
				margin-right: 16px;
				margin-top: 0;
				margin-bottom: 0;
			}
			#oembed-footer-text-%s {
			}
			#oembed-footer-link-%s {
			  text-decoration: underline;
				color: #5555FF;
				display: block;
				font-size: 16px;
			}
			#oembed-footer-text-meta-%s {
				display: block;
				font-size: 12px;
			}
		</style>
		<div id="oembed-container-%s">
			<div id="oembed-body-%s"> <!-- body -->
				<span>
					<a id="oembed-body-link-%s"
					   href="%s" target="_blank" rel="noopener noreferrer">
						%s
					</a>
				</span>
				<span id="oembed-body-description-%s">%s</span>
				<span id="oembed-body-excerpt-%s">%s</span>
			</div>
			<div id="oembed-footer-%s"> <!-- footer -->
				<img id="oembed-footer-logo-%s"
				     src="https://s.gravatar.com/avatar/93bc8fb48f57c11e417dad9d26a2fb8a?s=44" />
				<div id="oembed-footer-text-%s">
					<a id="oembed-footer-link-%s"
						href="https://blog.petitviolet.net">
						blog.petitviolet.net
					</a>
					<div id="oembed-footer-text-meta-%s">
						%s [%s]
					</div>
				</div>
			</div>
		</div>
	`, id, id, id, id, id, id, // CSS
		id, id, id, id, id, id, id, // CSS
		url, post.Title,
		id, post.Description,
		id, post.Excerpt,
		id, id, id, id, id, // CSS
		post.Date, strings.Join(post.Tags, ", "))
}

func buildPost(raw []byte) *Post {
	var pageData map[string]interface{}
	json.Unmarshal(raw, &pageData)

	title, _ := jsonpointer.Get(pageData, "/result/data/post/frontmatter/title")
	description, _ := jsonpointer.Get(pageData, "/result/data/post/frontmatter/description")
	excerpt, _ := jsonpointer.Get(pageData, "/result/data/post/excerpt")
	date, _ := jsonpointer.Get(pageData, "/result/data/post/frontmatter/date")
	_tags, _ := jsonpointer.Get(pageData, "/result/data/post/frontmatter/tags")
	tagIs := _tags.([]interface{})
	tagStrs := make([]string, len(tagIs))
	for i, v := range tagIs {
		tagStrs[i] = v.(string)
	}
	// fmt.Printf("pageDataPath: %s\n", pageDataPath)
	// fmt.Printf("raw: %s\n", raw)
	// fmt.Printf("title: %v\n", title)
	// fmt.Printf("description: %v\n", description)
	// fmt.Printf("date: %v\n", date)
	// fmt.Printf("tags: %v\n", tagStrs)
	post := Post{
		Title:       title.(string),
		Description: description.(string),
		Excerpt:     excerpt.(string),
		Date:        date.(string),
		Tags:        tagStrs,
	}
	return &post
}

func buildPageDatePath(date string, name string) string {
	return fmt.Sprintf("public/page-data/post/%s/%s/page-data.json", date, name)
}