package htmlx

import (
	"io"
	"strings"

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

// ExtractAnchors returns all hrefs from <a> tags.
func ExtractAnchors(r io.Reader) []string {
	tokens := html.NewTokenizer(r)
	var hrefs []string
	for {
		t := tokens.Next()
		switch t {
		case html.StartTagToken, html.SelfClosingTagToken:
			tn, hasAttr := tokens.TagName()
			if string(tn) != "a" || !hasAttr {
				continue
			}
			for {
				key, val, more := tokens.TagAttr()
				if string(key) == "href" {
					v := strings.TrimSpace(string(val))
					if v != "" {
						hrefs = append(hrefs, v)
					}
				}
				if !more {
					break
				}
			}
		case html.ErrorToken:
			return hrefs
		}
	}
}