package telegram

import (
	"encoding/base64"
	"fmt"
	"html"
	"strconv"
	"strings"
)

const TelegramMessageLimit = 4096
const TelegramHTMLMessageLimit = 3900

func EscapeHTML(text string) string {
	return html.EscapeString(text)
}

func SummaryDetailsHTML(summary, details string) string {
	summary = strings.TrimSpace(summary)
	details = strings.TrimSpace(details)
	if details == "" {
		return EscapeHTML(summary)
	}
	if summary == "" {
		return ExpandableQuoteHTML(details)
	}
	return EscapeHTML(summary) + "\n" + ExpandableQuoteHTML(details)
}

func ExpandableQuoteHTML(text string) string {
	text = strings.TrimSpace(text)
	if text == "" {
		return ""
	}
	return "<blockquote expandable>" + EscapeHTML(text) + "</blockquote>"
}

func SummaryDetailsHTMLLimited(summary, details string, limit int) string {
	if limit <= 0 {
		limit = TelegramHTMLMessageLimit
	}
	summary = strings.TrimSpace(summary)
	details = strings.TrimSpace(details)
	out := SummaryDetailsHTML(summary, details)
	if len([]rune(out)) <= limit || details == "" {
		return out
	}

	suffix := "\n...[truncated]"
	runes := []rune(details)
	for len(runes) > 0 {
		candidateLen := len(runes) - max(1, (len([]rune(out))-limit)/2)
		if candidateLen < 0 {
			candidateLen = 0
		}
		if candidateLen > len(runes) {
			candidateLen = len(runes)
		}
		candidate := strings.TrimSpace(string(runes[:candidateLen])) + suffix
		out = SummaryDetailsHTML(summary, candidate)
		if len([]rune(out)) <= limit || candidateLen == 0 {
			return out
		}
		runes = runes[:candidateLen]
	}
	return SummaryDetailsHTML(summary, suffix)
}

func FitHTMLMessage(htmlText string, limit int) string {
	if limit <= 0 {
		limit = TelegramHTMLMessageLimit
	}
	htmlText = strings.TrimSpace(htmlText)
	if len([]rune(htmlText)) <= limit {
		return htmlText
	}

	const open = "<blockquote expandable>"
	const close = "</blockquote>"
	const truncatedQuote = "...[truncated]"
	for len([]rune(htmlText)) > limit {
		contentStart, contentEnd, content := largestBlockquoteContent(htmlText, open, close)
		if contentStart < 0 {
			return truncateHTMLText(htmlText, limit)
		}

		contentRunes := []rune(strings.TrimSpace(html.UnescapeString(content)))
		over := len([]rune(htmlText)) - limit
		keep := len(contentRunes) - over - 80
		if keep < 0 {
			keep = 0
		}
		if keep >= len(contentRunes) {
			keep = len(contentRunes) - 1
		}
		replacementText := truncatedQuote
		if keep > 0 {
			replacementText = strings.TrimSpace(string(contentRunes[:keep])) + "\n" + truncatedQuote
		}
		replacement := EscapeHTML(replacementText)
		if replacement == content {
			return summaryOnlyHTML(htmlText, limit)
		}
		htmlText = htmlText[:contentStart] + replacement + htmlText[contentEnd:]
	}
	return htmlText
}

func largestBlockquoteContent(htmlText, open, close string) (int, int, string) {
	bestStart := -1
	bestEnd := -1
	bestContent := ""
	searchFrom := 0
	for {
		start := strings.Index(htmlText[searchFrom:], open)
		if start < 0 {
			break
		}
		start += searchFrom
		contentStart := start + len(open)
		end := strings.Index(htmlText[contentStart:], close)
		if end < 0 {
			break
		}
		end += contentStart
		content := htmlText[contentStart:end]
		if bestStart < 0 || len([]rune(content)) > len([]rune(bestContent)) {
			bestStart = contentStart
			bestEnd = end
			bestContent = content
		}
		searchFrom = end + len(close)
	}
	return bestStart, bestEnd, bestContent
}

func summaryOnlyHTML(htmlText string, limit int) string {
	const open = "<blockquote expandable>"
	const close = "</blockquote>"
	for {
		start := strings.Index(htmlText, open)
		if start < 0 {
			break
		}
		end := strings.Index(htmlText[start+len(open):], close)
		if end < 0 {
			break
		}
		end += start + len(open) + len(close)
		htmlText = strings.TrimRight(htmlText[:start], "\n") + "\n" + strings.TrimLeft(htmlText[end:], "\n")
	}
	return truncateHTMLText(strings.TrimSpace(htmlText), limit)
}

func truncateHTMLText(htmlText string, limit int) string {
	if limit <= 0 {
		limit = TelegramHTMLMessageLimit
	}
	suffix := "\n...[truncated]"
	runes := []rune(htmlText)
	if len(runes) <= limit {
		return htmlText
	}
	keep := limit - len([]rune(suffix))
	if keep < 0 {
		keep = 0
	}
	return string(runes[:keep]) + suffix
}

func ChunkText(text string, max int) []string {
	if max <= 0 {
		max = TelegramMessageLimit
	}
	runes := []rune(text)
	if len(runes) == 0 {
		return nil
	}
	var chunks []string
	for len(runes) > max {
		cut := max
		for i := max; i > max/2; i-- {
			if runes[i-1] == '\n' {
				cut = i
				break
			}
		}
		chunks = append(chunks, string(runes[:cut]))
		runes = runes[cut:]
	}
	if len(runes) > 0 {
		chunks = append(chunks, string(runes))
	}
	return chunks
}

func ApprovalCallbackData(id int64, decision string) string {
	return fmt.Sprintf("approval:%d:%s", id, decision)
}

func ParseApprovalCallbackData(data string) (int64, string, bool) {
	parts := strings.Split(data, ":")
	if len(parts) != 3 || parts[0] != "approval" {
		return 0, "", false
	}
	id, err := strconv.ParseInt(parts[1], 10, 64)
	if err != nil || id <= 0 {
		return 0, "", false
	}
	switch parts[2] {
	case "accept", "acceptForSession", "decline", "cancel", "details":
		return id, parts[2], true
	default:
		return 0, "", false
	}
}

func WorkspaceCallbackData(id int64) string {
	return fmt.Sprintf("workspace:%d", id)
}

func ParseWorkspaceCallbackData(data string) (int64, bool) {
	if !strings.HasPrefix(data, "workspace:") {
		return 0, false
	}
	id, err := strconv.ParseInt(strings.TrimPrefix(data, "workspace:"), 10, 64)
	return id, err == nil && id > 0
}

func ResumeThreadCallbackData(id int64) string {
	return fmt.Sprintf("resume:thread:%d", id)
}

func ParseResumeThreadCallbackData(data string) (int64, bool) {
	if !strings.HasPrefix(data, "resume:thread:") {
		return 0, false
	}
	id, err := strconv.ParseInt(strings.TrimPrefix(data, "resume:thread:"), 10, 64)
	return id, err == nil && id > 0
}

func ResumePageCallbackData(page int) string {
	return fmt.Sprintf("resume:page:%d", page)
}

func ParseResumePageCallbackData(data string) (int, bool) {
	if !strings.HasPrefix(data, "resume:page:") {
		return 0, false
	}
	page, err := strconv.Atoi(strings.TrimPrefix(data, "resume:page:"))
	return page, err == nil && page >= 0
}

func ModelCallbackData(modelID string) (string, bool) {
	encoded := base64.RawURLEncoding.EncodeToString([]byte(modelID))
	data := "model:" + encoded
	return data, len([]rune(data)) <= 64
}

func ParseModelCallbackData(data string) (string, bool) {
	if !strings.HasPrefix(data, "model:") {
		return "", false
	}
	decoded, err := base64.RawURLEncoding.DecodeString(strings.TrimPrefix(data, "model:"))
	if err != nil || len(decoded) == 0 {
		return "", false
	}
	return string(decoded), true
}

func EffortCallbackData(effort string) string {
	encoded := base64.RawURLEncoding.EncodeToString([]byte(effort))
	return "effort:" + encoded
}

func ParseEffortCallbackData(data string) (string, bool) {
	if !strings.HasPrefix(data, "effort:") {
		return "", false
	}
	decoded, err := base64.RawURLEncoding.DecodeString(strings.TrimPrefix(data, "effort:"))
	if err != nil || len(decoded) == 0 {
		return "", false
	}
	return string(decoded), true
}