package htmlx

import (
	"regexp"
	"sort"
	"strings"
	"unicode/utf8"

	"git.cloudyne.io/go/hiscaler-gox/stringx"
)

var (
	// Strip regexp
	rxStrip = regexp.MustCompile(`(?s)<sty(.*)/style>|<scr(.*)/script>|<link(.*)/>|<meta(.*)/>|<!--(.*)-->| style=['"]+(.*)['"]+`)

	// Spaceless regexp
	rxSpaceless = regexp.MustCompile(`/>\s+</`)

	// Clean regexp
	rxCleanCSS        = regexp.MustCompile(`(?s)<sty(.*)/style>|<link(.*)/>| style=['"]+(.*)['"]+`)
	rxCleanJavascript = regexp.MustCompile(`(?s)<script(.*)/script>`)
	rxCleanComment    = regexp.MustCompile(`(?s)<!--(.*)-->`)
	rxCleanMeta       = regexp.MustCompile(`(?s)<meta(.*)/>`)
)

type CleanMode uint32

const (
	CleanModeCSS CleanMode = 1 << (10 - iota) // 包括元素内嵌样式
	CleanModeJavascript
	CleanModeComment
	CleanModeMeta
	CleanModeSpace
	CleanModeAll = CleanModeCSS | CleanModeJavascript | CleanModeComment | CleanModeMeta | CleanModeSpace
)

// Strip Clean html tags
// https://stackoverflow.com/questions/55036156/how-to-replace-all-html-tag-with-empty-string-in-golang
func Strip(html string) string {
	html = strings.TrimSpace(html)
	if html != "" {
		html = rxStrip.ReplaceAllString(html, "")
	}
	if html == "" {
		return ""
	}

	const (
		htmlTagStart = 60 // Unicode `<`
		htmlTagEnd   = 62 // Unicode `>`
	)
	// Setup a string builder and allocate enough memory for the new string.
	var builder strings.Builder
	builder.Grow(len(html) + utf8.UTFMax)

	in := false // True if we are inside an HTML tag.
	start := 0  // The index of the previous start tag character `<`
	end := 0    // The index of the previous end tag character `>`

	for i, c := range html {
		// If this is the last character and we are not in an HTML tag, save it.
		if (i+1) == len(html) && end >= start && c != htmlTagStart && c != htmlTagEnd {
			builder.WriteString(html[end:])
		}

		// Keep going if the character is not `<` or `>`
		if c != htmlTagStart && c != htmlTagEnd {
			continue
		}

		if c == htmlTagStart {
			// Only update the start if we are not in a tag.
			// This make sure we strip out `<<br>` not just `<br>`
			if !in {
				start = i
			}
			in = true

			// Write the valid string between the close and start of the two tags.
			builder.WriteString(html[end:start])
			continue
		}
		// else c == htmlTagEnd
		in = false
		end = i + 1
	}
	s := builder.String()
	if s != "" {
		s = strings.TrimSpace(Spaceless(s))
	}
	return s
}

// Spaceless 移除多余的空格
func Spaceless(html string) string {
	html = stringx.RemoveExtraSpace(html)
	if html == "" {
		return ""
	}

	return rxSpaceless.ReplaceAllString(html, "><")
}

func Clean(html string, cleanMode CleanMode) string {
	if html == "" {
		return html
	}
	const n = 5
	modes := [n]bool{} // css, javascript, comment, meta, space, all
	for i := 0; i < n; i++ {
		if cleanMode&(1<<uint(10-i)) != 0 {
			modes[i] = true
		}
	}
	if modes[n-1] {
		html = Spaceless(rxStrip.ReplaceAllString(html, ""))
	} else {
		for i := 0; i < n-2; i++ {
			if modes[i] {
				switch i {
				case 0:
					html = rxCleanCSS.ReplaceAllString(html, "")
				case 1:
					html = rxCleanJavascript.ReplaceAllString(html, "")
				case 2:
					html = rxCleanComment.ReplaceAllString(html, "")
				case 3:
					html = rxCleanMeta.ReplaceAllString(html, "")
				case 4:
					html = Spaceless(html)
				}
			}
		}
	}
	return html
}

func Tag(tag, content string, attributes, styles map[string]string) string {
	var sb strings.Builder
	sb.Grow(len(tag)*2 + len(content) + 5)
	sb.WriteString("<")
	sb.WriteString(tag)
	fnSortedKeys := func(d map[string]string) []string {
		n := len(d)
		if n == 0 {
			return nil
		}

		keys := make([]string, n)
		i := 0
		for k := range d {
			keys[i] = k
			i++
		}
		if i > 1 {
			sort.Strings(keys)
		}
		return keys
	}

	for _, k := range fnSortedKeys(attributes) {
		sb.WriteString(" ")
		sb.WriteString(k)
		sb.WriteString(`="`)
		sb.WriteString(attributes[k])
		sb.WriteString(`"`)
	}

	keys := fnSortedKeys(styles)
	if len(keys) > 0 {
		sb.WriteString(` style="`)
		for _, k := range keys {
			sb.WriteString(k)
			sb.WriteString(":")
			sb.WriteString(styles[k])
			sb.WriteString(`;`)
		}
		sb.WriteString(`"`)
	}
	sb.WriteString(">")
	sb.WriteString(content)
	sb.WriteString("</")
	sb.WriteString(tag)
	sb.WriteString(">")
	return sb.String()
}