package facebook

import (
	"errors"
	"fmt"
	"net/url"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"git.trj.tw/golang/go-crawler/modules/browser"
	"github.com/tebeka/selenium"
)

var fbURL = "https://www.facebook.com"

// PostInfo -
type PostInfo struct {
	Text string
	ID   string
	Link string
	Time int64
}

// ByPostInfo -
type ByPostInfo []PostInfo

// Len -
func (p ByPostInfo) Len() int { return len(p) }

// Swap -
func (p ByPostInfo) Swap(i, j int) { p[i], p[j] = p[j], p[i] }

// Less -
func (p ByPostInfo) Less(i, j int) bool { return p[i].Time < p[j].Time }

var (
	idRegexps []*regexp.Regexp
	qsRegexp  *regexp.Regexp
)

func init() {
	idRegexps = make([]*regexp.Regexp, 0, 4)
	idRegexps = append(idRegexps,
		regexp.MustCompile("[\\?|&]story_fbid\\=(\\d+)"),
		regexp.MustCompile("\\/posts\\/(\\d+)"),
		regexp.MustCompile("\\/photos\\/.+?\\/(\\d+)"),
		regexp.MustCompile("\\/videos\\/(\\d+)"))

	qsRegexp = regexp.MustCompile("id")
}

// GetLastPost -
func GetLastPost(page string) (info *PostInfo, err error) {
	if len(page) == 0 {
		return nil, errors.New("page id is empty")
	}

	pageURL, err := url.Parse(fbURL)
	if err != nil {
		return nil, err
	}
	pageURL, err = pageURL.Parse(fmt.Sprintf("/%s/posts", page))

	wd, err := browser.NewWD()
	if err != nil {
		return nil, err
	}
	defer wd.Quit()

	err = wd.Get(pageURL.String())
	if err != nil {
		return nil, err
	}

	elements, err := wd.FindElements(selenium.ByCSSSelector, "div.userContentWrapper")
	if err != nil {
		return nil, err
	}
	_ = elements
	posts := make([]PostInfo, 0, len(elements))

	for _, el := range elements {
		post := PostInfo{}

		// get timestamp
		timeEl, err := el.FindElement(selenium.ByTagName, "abbr")
		if err != nil {
			continue
		}
		timeStr, err := timeEl.GetAttribute("data-utime")
		if err != nil {
			continue
		}
		timestamp, err := strconv.Atoi(timeStr)
		if err != nil {
			continue
		}
		post.Time = int64(timestamp)

		// get link element
		linkEl, err := timeEl.FindElement(selenium.ByXPATH, "..")
		if err != nil {
			continue
		}
		post.Link, err = linkEl.GetAttribute("href")
		if err != nil {
			continue
		}

		// get post content
		postEl, err := el.FindElement(selenium.ByCSSSelector, "div.userContent")
		if err != nil {
			continue
		}
		post.Text, err = postEl.Text()
		if err != nil {
			continue
		}

		// get post id
		postChile, err := postEl.FindElement(selenium.ByXPATH, "./*")
		if err != nil {
			continue
		}
		id, err := postChile.GetAttribute("id")
		if err != nil || len(id) == 0 {
			for _, regex := range idRegexps {
				if regex.Match([]byte(post.Link)) {
					strs := regex.FindAllStringSubmatch(post.Link, -1)
					if len(strs) > 0 && len(strs[0]) > 1 {
						id = strs[0][1]
						break
					}
				}
			}
		}

		posts = append(posts, post)

	}

	sort.Slice(posts, func(i, j int) bool {
		return posts[i].Time > posts[j].Time
	})

	info = &posts[0]

	// remove qs
	urls := strings.Split(info.Link, "?")
	if len(urls) > 1 {
		qsStr := strings.Split(urls[1], "&")
		if len(qsStr) > 0 {
			qs := make([]string, 0)
			for _, val := range qsStr {
				items := strings.SplitN(val, "=", 1)
				if len(items) > 0 {
					if qsRegexp.MatchString(items[0]) {
						qs = append(qs, val)
					}
				}
			}

			if len(qs) > 0 {
				info.Link = urls[0] + "?" + strings.Join(qs, "&")
			}
		}
	}

	info.Link = fbURL + info.Link

	return info, nil
}