package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"strconv"

	"golang.org/x/net/html"
)

type contentFetcher interface {
	fetchContent(url string) (content, error)
}

type content struct {
	title     string
	excerpt   string
	authors   []string
	imageURL  string
	wordCount int
}

type pocket struct {
	consumerKey string
	accessToken string
}

type Article struct {
	ItemId      string            `json:"item_id"`
	ResolvedId  string            `json:"resolved_id"`
	GivenUrl    string            `json:"given_url"`
	GivenTitle  string            `json:"given_title"`
	Title       string            `json:"title"`
	ResolvedUrl string            `json:"resolved_url"`
	Excerpt     string            `json:"excerpt"`
	IsArticle   string            `json:"is_article"`
	WordCount   string            `json:"word_count"`
	Authors     map[string]Author `json:"authors"`
	TopImageURL string            `json:"top_image_url"`
}

type Author struct {
	AuthorID string `json:"author_id"`
	Name     string `json:"name"`
	URL      string `json:"url"`
}

func newPocket(consumerKey, accessToken string) *pocket {
	return &pocket{consumerKey, accessToken}
}

func (p *pocket) fetchContent(url string) (cont content, err error) {
	article, err := p.addItem(url)
	if err != nil {
		return
	}

	cont.title = article.Title
	cont.excerpt = article.Excerpt
	cont.wordCount, _ = strconv.Atoi(article.WordCount)
	for _, author := range article.Authors {
		cont.authors = append(cont.authors, author.Name)
	}
	cont.imageURL = article.TopImageURL
	return
}

func (p *pocket) addItem(url string) (Article, error) {
	body := map[string]string{
		"access_token": p.accessToken,
		"consumer_key": p.consumerKey,
		"url":          url,
	}
	jsonBody, err := json.Marshal(body)
	if err != nil {
		return Article{}, err
	}

	res, err := http.Post("https://getpocket.com/v3/add", "application/json", bytes.NewBuffer(jsonBody))
	if err != nil {
		return Article{}, err
	}
	defer res.Body.Close()
	resBody, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return Article{}, fmt.Errorf("Unable to retrieve items: %v", err)
	}
	if res.StatusCode != http.StatusOK {
		return Article{}, fmt.Errorf("Could not add item to pocket (%d): %s", res.StatusCode, string(resBody))
	}

	var resItem struct {
		Item Article `json:"item"`
	}
	json.Unmarshal(resBody, &resItem)
	return resItem.Item, nil
}

type dummyContentFetcher struct{}

func (dc *dummyContentFetcher) fetchContent(url string) (content, error) {
	return content{
		title: getTitle(url),
	}, nil
}

func getTitle(url string) string {
	resp, err := http.Get(url)
	if err != nil {
		log.Printf("Error fetching %s: %v", url, err)
		return url
	}
	defer resp.Body.Close()

	doc, err := html.Parse(resp.Body)
	if err != nil {
		log.Printf("Error parsing %s: %v", url, err)
		return url
	}
	title, ok := traverse(doc)
	if ok {
		return title
	}
	return url
}

func traverse(n *html.Node) (string, bool) {
	if isTitleElement(n) && n.FirstChild != nil {
		return n.FirstChild.Data, true
	}

	for c := n.FirstChild; c != nil; c = c.NextSibling {
		result, ok := traverse(c)
		if ok {
			return result, ok
		}
	}

	return "", false
}

func isTitleElement(n *html.Node) bool {
	return n.Type == html.ElementNode && n.Data == "title"
}