package engines

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"regexp"
	"strings"

	"github.com/metamorphosis-dev/kafka/internal/contracts"
)

// GSA User-Agent pool — these are Google Search Appliance identifiers
// that Google trusts for enterprise search appliance traffic.
var gsaUserAgents = []string{
	"Mozilla/5.0 (iPhone; CPU iPhone OS 17_5_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/399.2.845414227 Mobile/15E148 Safari/604.1",
	"Mozilla/5.0 (iPhone; CPU iPhone OS 17_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/406.0.862495628 Mobile/15E148 Safari/604.1",
	"Mozilla/5.0 (iPhone; CPU iPhone OS 17_7_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/406.0.862495628 Mobile/15E148 Safari/604.1",
	"Mozilla/5.0 (iPhone; CPU iPhone OS 18_0_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/406.0.862495628 Mobile/15E148 Safari/604.1",
	"Mozilla/5.0 (iPhone; CPU iPhone OS 18_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/399.2.845414227 Mobile/15E148 Safari/604.1",
	"Mozilla/5.0 (iPhone; CPU iPhone OS 18_5_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/406.0.862495628 Mobile/15E148 Safari/604.1",
}

func gsaUA() string {
	return gsaUserAgents[0] // deterministic for now; could rotate
}

type GoogleEngine struct {
	client *http.Client
}

func (e *GoogleEngine) Name() string { return "google" }

func (e *GoogleEngine) Search(ctx context.Context, req contracts.SearchRequest) (contracts.SearchResponse, error) {
	if strings.TrimSpace(req.Query) == "" {
		return contracts.SearchResponse{Query: req.Query}, nil
	}

	start := (req.Pageno - 1) * 10
	query := url.QueryEscape(req.Query)

	// Build URL like SearXNG does.
	u := fmt.Sprintf(
		"https://www.google.com/search?q=%s&filter=0&start=%d&hl=%s&lr=%s&safe=%s",
		query,
		start,
		googleHL(req.Language),
		googleUILanguage(req.Language),
		googleSafeSearchLevel(req.Safesearch),
	)

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	httpReq.Header.Set("User-Agent", gsaUA())
	httpReq.Header.Set("Accept", "*/*")
	httpReq.AddCookie(&http.Cookie{Name: "CONSENT", Value: "YES+"})

	resp, err := e.client.Do(httpReq)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	defer resp.Body.Close()

	// Check for Google block / CAPTCHA page.
	if detectGoogleSorry(resp) {
		return contracts.SearchResponse{
			Query:               req.Query,
			NumberOfResults:     0,
			Results:             nil,
			Answers:             []map[string]any{},
			Corrections:         []string{},
			Infoboxes:           []map[string]any{},
			Suggestions:         []string{},
			UnresponsiveEngines: [][2]string{{"google", "blocked by Google (CAPTCHA/sorry page)"}},
		}, nil
	}

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return contracts.SearchResponse{}, fmt.Errorf("google error: status=%d body=%q", resp.StatusCode, string(body))
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 128*1024))
	if err != nil {
		return contracts.SearchResponse{}, err
	}

	results := parseGoogleResults(string(body), req.Query)
	return contracts.SearchResponse{
		Query:               req.Query,
		NumberOfResults:     len(results),
		Results:             results,
		Answers:             []map[string]any{},
		Corrections:         []string{},
		Infoboxes:           []map[string]any{},
		Suggestions:         extractGoogleSuggestions(string(body)),
		UnresponsiveEngines: [][2]string{},
	}, nil
}

// detectGoogleSorry returns true if the response is a Google block/CAPTCHA page.
func detectGoogleSorry(resp *http.Response) bool {
	if resp.Request != nil {
		if resp.Request.URL.Host == "sorry.google.com" || strings.HasPrefix(resp.Request.URL.Path, "/sorry") {
			return true
		}
	}
	return false
}

// parseGoogleResults extracts search results from Google's HTML.
// Uses the same selectors as SearXNG: div.MjjYud for result containers.
func parseGoogleResults(body, query string) []contracts.MainResult {
	var results []contracts.MainResult

	// SearXNG selector: .//div[contains(@class, "MjjYud")]
	// Each result block contains a title link and snippet.
	// We simulate the XPath matching with regex-based extraction.

	// Find all MjjYud div blocks.
	mjjPattern := regexp.MustCompile(`<div[^>]*class="[^"]*MjjYud[^"]*"[^>]*>(.*?)</div>\s*(?=<div[^>]*class="[^"]*MjjYud|$)`)
	matches := mjjPattern.FindAllStringSubmatch(body, -1)

	for i, match := range matches {
		if len(match) < 2 {
			continue
		}
		block := match[1]

		// Extract title and URL from the result link.
		// Pattern: <a href="/url?q=ACTUAL_URL&amp;sa=..." ...>TITLE</a>
		urlPattern := regexp.MustCompile(`<a[^>]+href="(/url\?q=[^"&]+)`)
		urlMatch := urlPattern.FindStringSubmatch(block)
		if len(urlMatch) < 2 {
			continue
		}
		rawURL := urlMatch[1]
		// Remove /url?q= prefix and decode.
		actualURL := strings.TrimPrefix(rawURL, "/url?q=")
		if amp := strings.Index(actualURL, "&amp;"); amp != -1 {
			actualURL = actualURL[:amp]
		}
		if decoded, err := url.QueryUnescape(actualURL); err == nil {
			actualURL = decoded
		}

		if actualURL == "" || !strings.HasPrefix(actualURL, "http") {
			continue
		}

		// Extract title from the title tag.
		titlePattern := regexp.MustCompile(`<span[^>]*class="[^"]*qrStP[^"]*"[^>]*>([^<]+)</span>`)
		titleMatch := titlePattern.FindStringSubmatch(block)
		title := query
		if len(titleMatch) >= 2 {
			title = stripTags(titleMatch[1])
		} else {
			// Fallback: extract visible text from an <a> with data-title or role="link"
			linkTitlePattern := regexp.MustCompile(`<a[^>]+role="link"[^>]*>([^<]+)<`)
			ltMatch := linkTitlePattern.FindStringSubmatch(block)
			if len(ltMatch) >= 2 {
				title = stripTags(ltMatch[1])
			}
		}

		// Extract snippet from data-sncf divs (SearXNG's approach).
		snippet := extractGoogleSnippet(block)

		urlPtr := actualURL
		results = append(results, contracts.MainResult{
			Title:    title,
			URL:       &urlPtr,
			Content:   snippet,
			Engine:    "google",
			Score:     float64(len(matches) - i),
			Category:  "general",
			Engines:   []string{"google"},
			Template:  "default.html",
		})
	}

	return results
}

// extractGoogleSnippet extracts the snippet text from a Google result block.
func extractGoogleSnippet(block string) string {
	// Google's snippets live in divs with data-sncf attribute.
	// SearXNG looks for: .//div[contains(@data-sncf, "1")]
	snippetPattern := regexp.MustCompile(`<div[^>]+data-sncf="1"[^>]*>(.*?)</div>`)
	matches := snippetPattern.FindAllStringSubmatch(block, -1)
	var parts []string
	for _, m := range matches {
		if len(m) < 2 {
			continue
		}
		text := stripTags(m[1])
		if text != "" {
			parts = append(parts, text)
		}
	}
	return strings.Join(parts, " ")
}

// extractGoogleSuggestions extracts search suggestions from Google result cards.
func extractGoogleSuggestions(body string) []string {
	var suggestions []string
	// SearXNG xpath: //div[contains(@class, "ouy7Mc")]//a
	suggestionPattern := regexp.MustCompile(`<div[^>]*class="[^"]*ouy7Mc[^"]*"[^>]*>.*?<a[^>]*>([^<]+)</a>`, regexp.DotAll)
	matches := suggestionPattern.FindAllStringSubmatch(body, -1)
	seen := map[string]bool{}
	for _, m := range matches {
		if len(m) < 2 {
			continue
		}
		s := strings.TrimSpace(stripTags(m[1]))
		if s != "" && !seen[s] {
			seen[s] = true
			suggestions = append(suggestions, s)
		}
	}
	return suggestions
}

// googleHL maps SearXNG locale to Google hl (host language) parameter.
// e.g. "en-US" -> "en-US"
func googleHL(lang string) string {
	lang = strings.ToLower(strings.TrimSpace(lang))
	if lang == "" || lang == "auto" {
		return "en"
	}
	return lang
}

// googleUILanguage maps SearXNG language to Google lr (language restrict) parameter.
// e.g. "en" -> "lang_en", "de" -> "lang_de"
func googleUILanguage(lang string) string {
	lang = strings.ToLower(strings.Split(lang, "-")[0])
	if lang == "" || lang == "auto" {
		return ""
	}
	return "lang_" + lang
}

// googleSafeSearchLevel maps safesearch (0-2) to Google's safe parameter.
func googleSafeSearchLevel(safesearch int) string {
	switch safesearch {
	case 0:
		return "off"
	case 1:
		return "medium"
	case 2:
		return "high"
	default:
		return "medium"
	}
}

// stripTags removes HTML tags from a string.
func stripTags(s string) string {
	stripper := regexp.MustCompile(`<[^>]*>`)
	s = stripper.ReplaceAllString(s, "")
	s = strings.ReplaceAll(s, "&amp;", "&")
	s = strings.ReplaceAll(s, "&quot;", `"`)
	s = strings.ReplaceAll(s, "&#39;", "'")
	s = strings.ReplaceAll(s, "&nbsp;", " ")
	return strings.TrimSpace(s)
}