package tools

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"regexp"
	"strings"
	"time"
)

const (
	userAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"

	// HTTP client timeouts for web tool providers.
	searchTimeout     = 10 * time.Second // Brave, Tavily, DuckDuckGo
	perplexityTimeout = 30 * time.Second // Perplexity (LLM-based, slower)
	fetchTimeout      = 60 * time.Second // WebFetchTool

	defaultMaxChars = 50000
	maxRedirects    = 5
)

// Pre-compiled regexes for HTML text extraction
var (
	reScript     = regexp.MustCompile(`<script[\s\S]*?</script>`)
	reStyle      = regexp.MustCompile(`<style[\s\S]*?</style>`)
	reTags       = regexp.MustCompile(`<[^>]+>`)
	reWhitespace = regexp.MustCompile(`[^\S\n]+`)
	reBlankLines = regexp.MustCompile(`\n{3,}`)

	// DuckDuckGo result extraction
	reDDGLink    = regexp.MustCompile(`<a[^>]*class="[^"]*result__a[^"]*"[^>]*href="([^"]+)"[^>]*>([\s\S]*?)</a>`)
	reDDGSnippet = regexp.MustCompile(`<a class="result__snippet[^"]*".*?>([\s\S]*?)</a>`)
)

// createHTTPClient creates an HTTP client with optional proxy support
func createHTTPClient(proxyURL string, timeout time.Duration) (*http.Client, error) {
	client := &http.Client{
		Timeout: timeout,
		Transport: &http.Transport{
			MaxIdleConns:        10,
			IdleConnTimeout:     30 * time.Second,
			DisableCompression:  false,
			TLSHandshakeTimeout: 15 * time.Second,
		},
	}

	if proxyURL != "" {
		proxy, err := url.Parse(proxyURL)
		if err != nil {
			return nil, fmt.Errorf("invalid proxy URL: %w", err)
		}
		scheme := strings.ToLower(proxy.Scheme)
		switch scheme {
		case "http", "https", "socks5", "socks5h":
		default:
			return nil, fmt.Errorf(
				"unsupported proxy scheme %q (supported: http, https, socks5, socks5h)",
				proxy.Scheme,
			)
		}
		if proxy.Host == "" {
			return nil, fmt.Errorf("invalid proxy URL: missing host")
		}
		client.Transport.(*http.Transport).Proxy = http.ProxyURL(proxy)
	} else {
		client.Transport.(*http.Transport).Proxy = http.ProxyFromEnvironment
	}

	return client, nil
}

type SearchProvider interface {
	Search(ctx context.Context, query string, count int) (string, error)
}

type BraveSearchProvider struct {
	apiKey string
	proxy  string
	client *http.Client
}

func (p *BraveSearchProvider) Search(ctx context.Context, query string, count int) (string, error) {
	searchURL := fmt.Sprintf("https://api.search.brave.com/res/v1/web/search?q=%s&count=%d",
		url.QueryEscape(query), count)

	req, err := http.NewRequestWithContext(ctx, "GET", searchURL, nil)
	if err != nil {
		return "", fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Accept", "application/json")
	req.Header.Set("X-Subscription-Token", p.apiKey)

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

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("failed to read response: %w", err)
	}

	var searchResp struct {
		Web struct {
			Results []struct {
				Title       string `json:"title"`
				URL         string `json:"url"`
				Description string `json:"description"`
			} `json:"results"`
		} `json:"web"`
	}

	if err := json.Unmarshal(body, &searchResp); err != nil {
		// Log error body for debugging
		fmt.Printf("Brave API Error Body: %s\n", string(body))
		return "", fmt.Errorf("failed to parse response: %w", err)
	}

	results := searchResp.Web.Results
	if len(results) == 0 {
		return fmt.Sprintf("No results for: %s", query), nil
	}

	var lines []string
	lines = append(lines, fmt.Sprintf("Results for: %s", query))
	for i, item := range results {
		if i >= count {
			break
		}
		lines = append(lines, fmt.Sprintf("%d. %s\n   %s", i+1, item.Title, item.URL))
		if item.Description != "" {
			lines = append(lines, fmt.Sprintf("   %s", item.Description))
		}
	}

	return strings.Join(lines, "\n"), nil
}

type TavilySearchProvider struct {
	apiKey  string
	baseURL string
	proxy   string
	client  *http.Client
}

func (p *TavilySearchProvider) Search(ctx context.Context, query string, count int) (string, error) {
	searchURL := p.baseURL
	if searchURL == "" {
		searchURL = "https://api.tavily.com/search"
	}

	payload := map[string]any{
		"api_key":             p.apiKey,
		"query":               query,
		"search_depth":        "advanced",
		"include_answer":      false,
		"include_images":      false,
		"include_raw_content": false,
		"max_results":         count,
	}

	bodyBytes, err := json.Marshal(payload)
	if err != nil {
		return "", fmt.Errorf("failed to marshal payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", searchURL, bytes.NewBuffer(bodyBytes))
	if err != nil {
		return "", fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("User-Agent", userAgent)

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

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("tavily api error (status %d): %s", resp.StatusCode, string(body))
	}

	var searchResp struct {
		Results []struct {
			Title   string `json:"title"`
			URL     string `json:"url"`
			Content string `json:"content"`
		} `json:"results"`
	}

	if err := json.Unmarshal(body, &searchResp); err != nil {
		return "", fmt.Errorf("failed to parse response: %w", err)
	}

	results := searchResp.Results
	if len(results) == 0 {
		return fmt.Sprintf("No results for: %s", query), nil
	}

	var lines []string
	lines = append(lines, fmt.Sprintf("Results for: %s (via Tavily)", query))
	for i, item := range results {
		if i >= count {
			break
		}
		lines = append(lines, fmt.Sprintf("%d. %s\n   %s", i+1, item.Title, item.URL))
		if item.Content != "" {
			lines = append(lines, fmt.Sprintf("   %s", item.Content))
		}
	}

	return strings.Join(lines, "\n"), nil
}

type DuckDuckGoSearchProvider struct {
	proxy  string
	client *http.Client
}

func (p *DuckDuckGoSearchProvider) Search(ctx context.Context, query string, count int) (string, error) {
	searchURL := fmt.Sprintf("https://html.duckduckgo.com/html/?q=%s", url.QueryEscape(query))

	req, err := http.NewRequestWithContext(ctx, "GET", searchURL, nil)
	if err != nil {
		return "", fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("User-Agent", userAgent)

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

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("failed to read response: %w", err)
	}

	return p.extractResults(string(body), count, query)
}

func (p *DuckDuckGoSearchProvider) extractResults(html string, count int, query string) (string, error) {
	// Simple regex based extraction for DDG HTML
	// Strategy: Find all result containers or key anchors directly

	// Try finding the result links directly first, as they are the most critical
	// Pattern: <a class="result__a" href="...">Title</a>
	// The previous regex was a bit strict. Let's make it more flexible for attributes order/content
	matches := reDDGLink.FindAllStringSubmatch(html, count+5)

	if len(matches) == 0 {
		return fmt.Sprintf("No results found or extraction failed. Query: %s", query), nil
	}

	var lines []string
	lines = append(lines, fmt.Sprintf("Results for: %s (via DuckDuckGo)", query))

	// Pre-compile snippet regex to run inside the loop
	// We'll search for snippets relative to the link position or just globally if needed
	// But simple global search for snippets might mismatch order.
	// Since we only have the raw HTML string, let's just extract snippets globally and assume order matches (risky but simple for regex)
	// Or better: Let's assume the snippet follows the link in the HTML

	// A better regex approach: iterate through text and find matches in order
	// But for now, let's grab all snippets too
	snippetMatches := reDDGSnippet.FindAllStringSubmatch(html, count+5)

	maxItems := min(len(matches), count)

	for i := range maxItems {
		urlStr := matches[i][1]
		title := stripTags(matches[i][2])
		title = strings.TrimSpace(title)

		// URL decoding if needed
		if strings.Contains(urlStr, "uddg=") {
			if u, err := url.QueryUnescape(urlStr); err == nil {
				_, after, ok := strings.Cut(u, "uddg=")
				if ok {
					urlStr = after
				}
			}
		}

		lines = append(lines, fmt.Sprintf("%d. %s\n   %s", i+1, title, urlStr))

		// Attempt to attach snippet if available and index aligns
		if i < len(snippetMatches) {
			snippet := stripTags(snippetMatches[i][1])
			snippet = strings.TrimSpace(snippet)
			if snippet != "" {
				lines = append(lines, fmt.Sprintf("   %s", snippet))
			}
		}
	}

	return strings.Join(lines, "\n"), nil
}

func stripTags(content string) string {
	return reTags.ReplaceAllString(content, "")
}

type PerplexitySearchProvider struct {
	apiKey string
	proxy  string
	client *http.Client
}

func (p *PerplexitySearchProvider) Search(ctx context.Context, query string, count int) (string, error) {
	searchURL := "https://api.perplexity.ai/chat/completions"

	payload := map[string]any{
		"model": "sonar",
		"messages": []map[string]string{
			{
				"role":    "system",
				"content": "You are a search assistant. Provide concise search results with titles, URLs, and brief descriptions in the following format:\n1. Title\n   URL\n   Description\n\nDo not add extra commentary.",
			},
			{
				"role":    "user",
				"content": fmt.Sprintf("Search for: %s. Provide up to %d relevant results.", query, count),
			},
		},
		"max_tokens": 1000,
	}

	payloadBytes, err := json.Marshal(payload)
	if err != nil {
		return "", fmt.Errorf("failed to marshal request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", searchURL, strings.NewReader(string(payloadBytes)))
	if err != nil {
		return "", fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+p.apiKey)
	req.Header.Set("User-Agent", userAgent)

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

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("Perplexity API error: %s", string(body))
	}

	var searchResp struct {
		Choices []struct {
			Message struct {
				Content string `json:"content"`
			} `json:"message"`
		} `json:"choices"`
	}

	if err := json.Unmarshal(body, &searchResp); err != nil {
		return "", fmt.Errorf("failed to parse response: %w", err)
	}

	if len(searchResp.Choices) == 0 {
		return fmt.Sprintf("No results for: %s", query), nil
	}

	return fmt.Sprintf("Results for: %s (via Perplexity)\n%s", query, searchResp.Choices[0].Message.Content), nil
}

type WebSearchTool struct {
	provider   SearchProvider
	maxResults int
}

type WebSearchToolOptions struct {
	BraveAPIKey          string
	BraveMaxResults      int
	BraveEnabled         bool
	TavilyAPIKey         string
	TavilyBaseURL        string
	TavilyMaxResults     int
	TavilyEnabled        bool
	DuckDuckGoMaxResults int
	DuckDuckGoEnabled    bool
	PerplexityAPIKey     string
	PerplexityMaxResults int
	PerplexityEnabled    bool
	Proxy                string
}

func NewWebSearchTool(opts WebSearchToolOptions) (*WebSearchTool, error) {
	var provider SearchProvider
	maxResults := 5

	// Priority: Perplexity > Brave > Tavily > DuckDuckGo
	if opts.PerplexityEnabled && opts.PerplexityAPIKey != "" {
		client, err := createHTTPClient(opts.Proxy, perplexityTimeout)
		if err != nil {
			return nil, fmt.Errorf("failed to create HTTP client for Perplexity: %w", err)
		}
		provider = &PerplexitySearchProvider{apiKey: opts.PerplexityAPIKey, proxy: opts.Proxy, client: client}
		if opts.PerplexityMaxResults > 0 {
			maxResults = opts.PerplexityMaxResults
		}
	} else if opts.BraveEnabled && opts.BraveAPIKey != "" {
		client, err := createHTTPClient(opts.Proxy, searchTimeout)
		if err != nil {
			return nil, fmt.Errorf("failed to create HTTP client for Brave: %w", err)
		}
		provider = &BraveSearchProvider{apiKey: opts.BraveAPIKey, proxy: opts.Proxy, client: client}
		if opts.BraveMaxResults > 0 {
			maxResults = opts.BraveMaxResults
		}
	} else if opts.TavilyEnabled && opts.TavilyAPIKey != "" {
		client, err := createHTTPClient(opts.Proxy, searchTimeout)
		if err != nil {
			return nil, fmt.Errorf("failed to create HTTP client for Tavily: %w", err)
		}
		provider = &TavilySearchProvider{
			apiKey:  opts.TavilyAPIKey,
			baseURL: opts.TavilyBaseURL,
			proxy:   opts.Proxy,
			client:  client,
		}
		if opts.TavilyMaxResults > 0 {
			maxResults = opts.TavilyMaxResults
		}
	} else if opts.DuckDuckGoEnabled {
		client, err := createHTTPClient(opts.Proxy, searchTimeout)
		if err != nil {
			return nil, fmt.Errorf("failed to create HTTP client for DuckDuckGo: %w", err)
		}
		provider = &DuckDuckGoSearchProvider{proxy: opts.Proxy, client: client}
		if opts.DuckDuckGoMaxResults > 0 {
			maxResults = opts.DuckDuckGoMaxResults
		}
	} else {
		return nil, nil
	}

	return &WebSearchTool{
		provider:   provider,
		maxResults: maxResults,
	}, nil
}

func (t *WebSearchTool) Name() string {
	return "web_search"
}

func (t *WebSearchTool) Description() string {
	return "Search the web for current information. Returns titles, URLs, and snippets from search results."
}

func (t *WebSearchTool) Parameters() map[string]any {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"query": map[string]any{
				"type":        "string",
				"description": "Search query",
			},
			"count": map[string]any{
				"type":        "integer",
				"description": "Number of results (1-10)",
				"minimum":     1.0,
				"maximum":     10.0,
			},
		},
		"required": []string{"query"},
	}
}

func (t *WebSearchTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
	query, ok := args["query"].(string)
	if !ok {
		return ErrorResult("query is required")
	}

	count := t.maxResults
	if c, ok := args["count"].(float64); ok {
		if int(c) > 0 && int(c) <= 10 {
			count = int(c)
		}
	}

	result, err := t.provider.Search(ctx, query, count)
	if err != nil {
		return ErrorResult(fmt.Sprintf("search failed: %v", err))
	}

	return &ToolResult{
		ForLLM:  result,
		ForUser: result,
	}
}

type WebFetchTool struct {
	maxChars        int
	proxy           string
	client          *http.Client
	fetchLimitBytes int64
}

func NewWebFetchTool(maxChars int, fetchLimitBytes int64) (*WebFetchTool, error) {
	// createHTTPClient cannot fail with an empty proxy string.
	return NewWebFetchToolWithProxy(maxChars, "", fetchLimitBytes)
}

func NewWebFetchToolWithProxy(maxChars int, proxy string, fetchLimitBytes int64) (*WebFetchTool, error) {
	if maxChars <= 0 {
		maxChars = defaultMaxChars
	}
	client, err := createHTTPClient(proxy, fetchTimeout)
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP client for web fetch: %w", err)
	}
	client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
		if len(via) >= maxRedirects {
			return fmt.Errorf("stopped after %d redirects", maxRedirects)
		}
		return nil
	}
	if fetchLimitBytes <= 0 {
		fetchLimitBytes = 10 * 1024 * 1024 // Security Fallback
	}
	return &WebFetchTool{
		maxChars:        maxChars,
		proxy:           proxy,
		client:          client,
		fetchLimitBytes: fetchLimitBytes,
	}, nil
}

func (t *WebFetchTool) Name() string {
	return "web_fetch"
}

func (t *WebFetchTool) Description() string {
	return "Fetch a URL and extract readable content (HTML to text). Use this to get weather info, news, articles, or any web content."
}

func (t *WebFetchTool) Parameters() map[string]any {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"url": map[string]any{
				"type":        "string",
				"description": "URL to fetch",
			},
			"maxChars": map[string]any{
				"type":        "integer",
				"description": "Maximum characters to extract",
				"minimum":     100.0,
			},
		},
		"required": []string{"url"},
	}
}

func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
	urlStr, ok := args["url"].(string)
	if !ok {
		return ErrorResult("url is required")
	}

	parsedURL, err := url.Parse(urlStr)
	if err != nil {
		return ErrorResult(fmt.Sprintf("invalid URL: %v", err))
	}

	if parsedURL.Scheme != "http" && parsedURL.Scheme != "https" {
		return ErrorResult("only http/https URLs are allowed")
	}

	if parsedURL.Host == "" {
		return ErrorResult("missing domain in URL")
	}

	maxChars := t.maxChars
	if mc, ok := args["maxChars"].(float64); ok {
		if int(mc) > 100 {
			maxChars = int(mc)
		}
	}

	req, err := http.NewRequestWithContext(ctx, "GET", urlStr, nil)
	if err != nil {
		return ErrorResult(fmt.Sprintf("failed to create request: %v", err))
	}

	req.Header.Set("User-Agent", userAgent)

	resp, err := t.client.Do(req)
	if err != nil {
		return ErrorResult(fmt.Sprintf("request failed: %v", err))
	}

	resp.Body = http.MaxBytesReader(nil, resp.Body, t.fetchLimitBytes)

	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		var maxBytesErr *http.MaxBytesError
		if errors.As(err, &maxBytesErr) {
			return ErrorResult(fmt.Sprintf("failed to read response: size exceeded %d bytes limit", t.fetchLimitBytes))
		}
		return ErrorResult(fmt.Sprintf("failed to read response: %v", err))
	}

	contentType := resp.Header.Get("Content-Type")

	var text, extractor string

	if strings.Contains(contentType, "application/json") {
		var jsonData any
		if err := json.Unmarshal(body, &jsonData); err == nil {
			formatted, _ := json.MarshalIndent(jsonData, "", "  ")
			text = string(formatted)
			extractor = "json"
		} else {
			text = string(body)
			extractor = "raw"
		}
	} else if strings.Contains(contentType, "text/html") || len(body) > 0 &&
		(strings.HasPrefix(string(body), "<!DOCTYPE") || strings.HasPrefix(strings.ToLower(string(body)), "<html")) {
		text = t.extractText(string(body))
		extractor = "text"
	} else {
		text = string(body)
		extractor = "raw"
	}

	truncated := len(text) > maxChars
	if truncated {
		text = text[:maxChars]
	}

	result := map[string]any{
		"url":       urlStr,
		"status":    resp.StatusCode,
		"extractor": extractor,
		"truncated": truncated,
		"length":    len(text),
		"text":      text,
	}

	resultJSON, _ := json.MarshalIndent(result, "", "  ")

	return &ToolResult{
		ForLLM: string(resultJSON),
		ForUser: fmt.Sprintf(
			"Fetched %d bytes from %s (extractor: %s, truncated: %v)",
			len(text),
			urlStr,
			extractor,
			truncated,
		),
	}
}

func (t *WebFetchTool) extractText(htmlContent string) string {
	result := reScript.ReplaceAllLiteralString(htmlContent, "")
	result = reStyle.ReplaceAllLiteralString(result, "")
	result = reTags.ReplaceAllLiteralString(result, "")

	result = strings.TrimSpace(result)

	result = reWhitespace.ReplaceAllString(result, " ")
	result = reBlankLines.ReplaceAllString(result, "\n\n")

	lines := strings.Split(result, "\n")
	var cleanLines []string
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line != "" {
			cleanLines = append(cleanLines, line)
		}
	}

	return strings.Join(cleanLines, "\n")
}