package web

import (
	"net/http"
	"strconv"
	"strings"

	"github.com/PuerkitoBio/goquery"
)

var ddgURL = urlMustParse("https://html.duckduckgo.com/html")

const uddgPrefix = "//duckduckgo.com/l/?uddg="

type DDG struct {
	keyword   string
	userAgent string
	page      int
	doc       *goquery.Document
	initDone  bool
	baseSel   *goquery.Selection
}

func (d *DDG) SetKeyword(keyword string) {
	d.keyword = keyword
}

func (d *DDG) SetPage(page int) {
	d.page = page * 30
}

func (d *DDG) SetUserAgent(ua string) {
	d.userAgent = "Opera/9.80 (Windows NT 5.1; U; zh-tw) Presto/2.8.131 Version/11.10" //ua
}

func (d *DDG) Init() error {
	initURL := copyURL(ddgURL)
	query := initURL.Query()
	query.Set("q", d.keyword)
	if d.page > 0 {
		query.Set("s", strconv.Itoa(d.page))
		query.Set("dc", strconv.Itoa(d.page+1))
	}
	initURL.RawQuery = query.Encode()

	req, err := http.NewRequest(
		http.MethodGet,
		initURL.String(),
		nil,
	)
	if err != nil {
		return err
	}
	if d.userAgent == "" {
		d.userAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
	}
	req.Header.Set("User-Agent", d.userAgent)

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer res.Body.Close()

	doc, err := goquery.NewDocumentFromReader(res.Body)
	if err != nil {
		return err
	}
	d.doc = doc
	d.baseSel = doc.Find(`#links > .result`)
	d.initDone = true
	return nil
}

func (d *DDG) Each(eachCb func(int) error) error {
	for i := 0; i < d.baseSel.Length(); i++ {
		err := eachCb(i)
		if err != nil {
			return err
		}
	}
	return nil
}

func (d *DDG) Title(i int) (string, error) {
	return strings.TrimSpace(get(d.baseSel, i).Children().First().ChildrenFiltered("h2").Text()), nil
}

func (d *DDG) Link(i int) (string, error) {
	link := get(d.baseSel, i).Children().First().ChildrenFiltered("a").AttrOr("href", "")
	if strings.HasPrefix(link, uddgPrefix) {
		link = urlMustParse(link).Query().Get("uddg")
	}
	return link, nil
}

func (d *DDG) Desc(i int) (string, error) {
	return get(d.baseSel, i).Children().First().ChildrenFiltered("a").Text(), nil
}

func (d *DDG) Name() string {
	return "ddg"
}