package useCases

import (
	"strings"
	"unicode/utf8"

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

type bodyFacts struct {
	spacedText       string
	textRunes        int
	hasSubheading    bool
	imagesWithoutAlt int
}

var blockElements = map[string]bool{
	"p": true, "div": true, "br": true, "li": true, "ul": true, "ol": true, "blockquote": true, "pre": true,
	"h1": true, "h2": true, "h3": true, "h4": true, "h5": true, "h6": true, "tr": true, "section": true, "article": true,
	"figure": true, "figcaption": true, "table": true, "hr": true,
}

var subheadings = map[string]bool{"h2": true, "h3": true, "h4": true, "h5": true, "h6": true}

var skippedElements = map[string]bool{"script": true, "style": true}

const sentenceTerminators = ".!?"

func analyzeBody(body string) bodyFacts {
	tokenizer := html.NewTokenizer(strings.NewReader(body))
	var plain, spaced strings.Builder
	facts := bodyFacts{}
	skipping := false
	for {
		kind := tokenizer.Next()
		if kind == html.ErrorToken {
			break
		}
		switch kind {
		case html.TextToken:
			if !skipping {
				text := string(tokenizer.Text())
				plain.WriteString(text)
				spaced.WriteString(text)
			}
		case html.StartTagToken, html.SelfClosingTagToken, html.EndTagToken:
			token := tokenizer.Token()
			skipping = nextSkipping(skipping, kind, token)
			if blockElements[token.Data] {
				spaced.WriteString(" ")
			}
			if kind == html.EndTagToken {
				continue
			}
			if subheadings[token.Data] {
				facts.hasSubheading = true
			}
			if token.Data == "img" && !hasAlt(token) {
				facts.imagesWithoutAlt++
			}
		}
	}
	facts.textRunes = utf8.RuneCountInString(strings.TrimSpace(plain.String()))
	facts.spacedText = strings.Join(strings.Fields(spaced.String()), " ")
	return facts
}

func nextSkipping(skipping bool, kind html.TokenType, token html.Token) bool {
	if !skippedElements[token.Data] {
		return skipping
	}
	switch kind {
	case html.StartTagToken:
		return true
	case html.EndTagToken:
		return false
	}
	return skipping
}

func hasAlt(token html.Token) bool {
	for _, attribute := range token.Attr {
		if attribute.Key == "alt" {
			return strings.TrimSpace(attribute.Val) != ""
		}
	}
	return false
}

func firstSentence(text string) string {
	runes := []rune(text)
	for index, character := range runes {
		if !strings.ContainsRune(sentenceTerminators, character) {
			continue
		}
		if index+1 == len(runes) || runes[index+1] == ' ' {
			return string(runes[:index+1])
		}
	}
	return text
}