package logging

import (
	"bytes"
	"io"
	"net/url"
	"regexp"
	"strings"

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

// The HTML tokenizer also accepts XML-shaped response fragments. Raw token
// bytes are retained; only explicitly sensitive tags/attributes are replaced.
func redactMarkup(body string) string {
	if !strings.Contains(body, "<") {
		return body
	}
	z := html.NewTokenizer(strings.NewReader(body))
	var out strings.Builder
	hiddenTag := ""
	depth := 0
	for {
		kind := z.Next()
		raw := bytes.Clone(z.Raw())
		if kind == html.ErrorToken {
			if z.Err() == io.EOF {
				out.Write(raw)
			}
			break
		}
		token := z.Token()
		if hiddenTag != "" {
			if kind == html.StartTagToken && token.Data == hiddenTag {
				depth++
			}
			if kind == html.EndTagToken && token.Data == hiddenTag {
				depth--
				if depth == 0 {
					hiddenTag = ""
					out.Write(raw)
				}
			}
			continue
		}
		if kind == html.StartTagToken || kind == html.SelfClosingTagToken {
			tag := string(raw)
			hideValue := false
			for _, a := range token.Attr {
				if (a.Key == "name" && sensitive(a.Val)) || (a.Key == "type" && strings.EqualFold(a.Val, "password")) {
					hideValue = true
				}
			}
			for _, a := range token.Attr {
				if sensitive(a.Key) || (hideValue && a.Key == "value") {
					pattern := regexp.MustCompile(`(?i)(\b` + regexp.QuoteMeta(a.Key) + `\s*=\s*)(?:"[^"]*"|'[^']*'|[^\s>]+)`)
					tag = pattern.ReplaceAllString(tag, `${1}"[REDACTED]"`)
				}
			}
			out.WriteString(tag)
			// A named sensitive field owns both its value attribute and enclosed
			// content (textarea/select/custom controls). Void inputs own only value;
			// they must never swallow following non-sensitive business elements.
			if kind == html.StartTagToken && (sensitive(token.Data) || (hideValue && !voidMarkupElement(token.Data))) {
				out.WriteString(redacted)
				hiddenTag = token.Data
				depth = 1
			}
		} else {
			out.Write(raw)
		}
	}
	return out.String()
}

func voidMarkupElement(name string) bool {
	switch name {
	case "area", "base", "br", "col", "embed", "hr", "img", "input", "link", "meta", "param", "source", "track", "wbr":
		return true
	default:
		return false
	}
}

// A form can be identified without guessing semantic values. Untouched pairs
// preserve their original encoding and order, including duplicate field names.
func redactForm(body string) (string, bool) {
	if strings.ContainsAny(body, "\r\n<>") || !strings.Contains(body, "&") || !strings.Contains(body, "=") {
		return body, false
	}
	parts := strings.Split(body, "&")
	for i, part := range parts {
		key, value, ok := strings.Cut(part, "=")
		if !ok {
			return body, false
		}
		decodedKey, err := url.QueryUnescape(key)
		if err != nil {
			return body, false
		}
		if sensitive(decodedKey) {
			parts[i] = key + "=" + url.QueryEscape(redacted)
			continue
		}
		decoded, err := url.QueryUnescape(value)
		if err != nil {
			return body, false
		}
		safe := cleanString(redactConversationLines(decoded))
		if safe != decoded {
			parts[i] = key + "=" + url.QueryEscape(safe)
		}
	}
	return strings.Join(parts, "&"), true
}

var textFieldLine = regexp.MustCompile(`^\s*([A-Za-z_][A-Za-z0-9_.-]*)\s*[:=]`)

func redactConversationLines(body string) string {
	lines := strings.SplitAfter(body, "\n")
	hiding := false
	for i, line := range lines {
		// Whitespace separates paragraphs inside a conversation, not records.
		// Ownership ends only at the explicit non-conversation field below.
		field := textFieldLine.FindStringSubmatch(line)
		if hiding {
			// Continuation lines and conversation speaker labels are not business
			// fields. A distinct non-conversation key starts the next ordinary field.
			speaker := len(field) > 0 && (strings.EqualFold(field[1], "user") || strings.EqualFold(field[1], "assistant") || strings.EqualFold(field[1], "system") || strings.EqualFold(field[1], "agent"))
			if len(field) == 0 || speaker {
				lines[i] = ""
				continue
			}
			hiding = false
		}
		if len(field) > 0 && sensitive(field[1]) {
			lines[i] = "[REDACTED_FIELD]"
			if strings.HasSuffix(line, "\n") {
				lines[i] += "\n"
			}
			// Credentials/header fields own their single line, not unrelated
			// following diagnostics. Only conversational fields own continuation.
			hiding = conversationField(field[1])
		}
	}
	return strings.Join(lines, "")
}