package lib

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strings"
)

// InjectionDetection contains patterns that indicate potential LLM injection attacks
var injectionPatterns = []*regexp.Regexp{
	regexp.MustCompile(`(?i)(ignore|forget|disregard)\s+(all|previous|your)\s+(instructions|prompts|training)`),
	regexp.MustCompile(`(?i)system\s*:\s*you\s+are\s+now`),
	regexp.MustCompile(`(?i)<\s*(system|assistant|user)\s*>`),
	regexp.MustCompile(`(?i)\[\s*(system|assistant|user)\s*\]`),
	regexp.MustCompile(`(?i)\{\s*(system|assistant|user)\s*\}`),
	regexp.MustCompile(`(?i)you\s+are\s+(an?\s+)?(attacker|hacker|malicious)`),
	regexp.MustCompile(`(?i)output\s*:\s*.*(?:password|secret|key|token)`),
	regexp.MustCompile(`(?i)prompt\s*:\s*.*(?:override|bypass|ignore)`),
}

// SanitizeResult indicates the outcome of sanitization
type SanitizeResult struct {
	Cleaned    string
	Violations []string
	Blocked    bool
}

// SanitizeUserInput sanitizes user input for LLM prompts (chat endpoint).
// Implements defense-in-depth: validation, injection detection, and message delimiters.
func SanitizeUserInput(input string, maxLen int) SanitizeResult {
	result := SanitizeResult{Cleaned: input}

	// Layer 1: Length enforcement
	if maxLen <= 0 {
		maxLen = 4000 // Default limit
	}
	if len(input) > maxLen {
		result.Cleaned = input[:maxLen]
		result.Violations = append(result.Violations, "input_truncated")
	}

	// Layer 2: Injection pattern detection
	for _, pattern := range injectionPatterns {
		if matches := pattern.FindAllString(result.Cleaned, -1); len(matches) > 0 {
			result.Violations = append(result.Violations, "injection_pattern_detected")
			result.Blocked = true
			// Replace matches with safe placeholders
			result.Cleaned = pattern.ReplaceAllString(result.Cleaned, "[FILTERED]")
		}
	}

	// Layer 3: Escape XML-like delimiters that could confuse message boundaries
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "<system>", "&lt;system&gt;")
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "</system>", "&lt;/system&gt;")
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "<assistant>", "&lt;assistant&gt;")
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "</assistant>", "&lt;/assistant&gt;")
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "<user>", "&lt;user&gt;")
	result.Cleaned = strings.ReplaceAll(result.Cleaned, "</user>", "&lt;/user&gt;")

	return result
}

// WrapUserMessage wraps user input in XML-style delimiters for clear separation from system instructions.
// This makes it harder for user input to be interpreted as system/assistant messages.
func WrapUserMessage(content string) string {
	return fmt.Sprintf("<user_message>\n%s\n</user_message>", content)
}

// WrapSystemMessage wraps system content in XML-style delimiters.
func WrapSystemMessage(content string) string {
	return fmt.Sprintf("<system_instructions>\n%s\n</system_instructions>", content)
}

// SanitizeHTMLContent prepares HTML content for LLM processing (scrape endpoint).
// Removes scripts, styles, and other potentially malicious content before LLM sees it.
func SanitizeHTMLContent(html string, maxLen int) string {
	if maxLen <= 0 {
		maxLen = 50000 // Default limit for HTML
	}

	// Layer 1: Remove scripts (both <script> tags and event handlers)
	// Remove <script>...</script> blocks entirely
	scriptRegex := regexp.MustCompile(`(?is)<script[^>]*>.*?</script>`)
	cleaned := scriptRegex.ReplaceAllString(html, "")

	// Layer 2: Remove <style> tags
	styleRegex := regexp.MustCompile(`(?is)<style[^>]*>.*?</style>`)
	cleaned = styleRegex.ReplaceAllString(cleaned, "")

	// Layer 3: Remove onclick, onload, etc. event handlers
	eventRegex := regexp.MustCompile(`(?i)\s+on\w+\s*=\s*"[^"]*"`)
	cleaned = eventRegex.ReplaceAllString(cleaned, "")

	eventRegex2 := regexp.MustCompile(`(?i)\s+on\w+\s*=\s*'[^']*'`)
	cleaned = eventRegex2.ReplaceAllString(cleaned, "")

	// Layer 4: Remove javascript: URLs
	jsUrlRegex := regexp.MustCompile(`(?i)javascript\s*:\s*[^"'>\s]+`)
	cleaned = jsUrlRegex.ReplaceAllString(cleaned, "")

	// Layer 5: Remove data: URLs that could be SVG/script-based
	dataUrlRegex := regexp.MustCompile(`(?i)data\s*:\s*[^"'>\s]+`)
	cleaned = dataUrlRegex.ReplaceAllString(cleaned, "[data-url-removed]")

	// Layer 6: Remove comments that might hide injection attempts
	commentRegex := regexp.MustCompile(`(?s)<!--.*?-->`)
	cleaned = commentRegex.ReplaceAllString(cleaned, "")

	// Layer 7: Normalize whitespace to reduce hidden characters
	cleaned = regexp.MustCompile(`[\x00-\x08\x0b\x0c\x0e-\x1f\x7f]`).ReplaceAllString(cleaned, "")

	// Layer 8: Length enforcement
	if len(cleaned) > maxLen {
		cleaned = cleaned[:maxLen]
	}

	return cleaned
}

// BuildSafeChatMessages constructs a properly delimited message list for chat LLM calls.
// Takes raw user input and sanitizes it before inclusion in messages.
func BuildSafeChatMessages(systemPrompt string, history []map[string]string, userMessage string, maxUserLen int) ([]map[string]interface{}, []string) {
	messages := []map[string]interface{}{
		{"role": "system", "content": WrapSystemMessage(systemPrompt)},
	}

	// Process history through sanitization
	for _, msg := range history {
		role := msg["role"]
		content := msg["content"]

		// Sanitize based on role
		if role == "user" {
			result := SanitizeUserInput(content, maxUserLen)
			content = WrapUserMessage(result.Cleaned)
		}
		// Assistant messages are trusted (came from our system)

		messages = append(messages, map[string]interface{}{
			"role":    role,
			"content": content,
		})
	}

	// Sanitize current user message
	result := SanitizeUserInput(userMessage, maxUserLen)
	messages = append(messages, map[string]interface{}{
		"role":    "user",
		"content": WrapUserMessage(result.Cleaned),
	})

	return messages, result.Violations
}

// BuildSafeScrapePrompt constructs a safe prompt with sanitized HTML content for scraping.
// The HTML is wrapped in delimiters to isolate it from instructions.
func BuildSafeScrapePrompt(instructions string, htmlContent string, domain string, maxHtmlLen int) string {
	sanitizedHTML := SanitizeHTMLContent(htmlContent, maxHtmlLen)

	return fmt.Sprintf(`%s

The following is sanitized HTML content from %s, enclosed in delimiters. Analyze this content only.

<scraped_html>
%s
</scraped_html>`,
		instructions, domain, sanitizedHTML)
}

// CallOpenRouter sends a request to OpenRouter (OpenAI-compatible API).
func CallOpenRouter(apiKey, model string, messages []map[string]interface{}, maxTokens int) (string, error) {
	if apiKey == "" {
		return "", fmt.Errorf("OpenRouter API key not configured")
	}

	reqBody := map[string]interface{}{
		"model":       model,
		"messages":    messages,
		"max_tokens":  maxTokens,
		"temperature": 0.1,
	}

	jsonBody, err := json.Marshal(reqBody)
	if err != nil {
		return "", fmt.Errorf("marshal request: %w", err)
	}

	req, err := http.NewRequest("POST", "https://openrouter.ai/api/v1/chat/completions", bytes.NewReader(jsonBody))
	if err != nil {
		return "", fmt.Errorf("create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+apiKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("API request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("read response: %w", err)
	}
	if resp.StatusCode != 200 {
		return "", fmt.Errorf("OpenRouter API error %d: %s", resp.StatusCode, string(body))
	}

	var oaiResp struct {
		Choices []struct {
			Message struct {
				Content string `json:"content"`
			} `json:"message"`
		} `json:"choices"`
	}
	if err := json.Unmarshal(body, &oaiResp); err != nil {
		return "", fmt.Errorf("parse response: %w", err)
	}
	if len(oaiResp.Choices) == 0 {
		return "", fmt.Errorf("empty response from OpenRouter")
	}

	text := strings.TrimSpace(oaiResp.Choices[0].Message.Content)
	text = strings.TrimPrefix(text, "```json")
	text = strings.TrimPrefix(text, "```")
	text = strings.TrimSuffix(text, "```")
	return strings.TrimSpace(text), nil
}