package engines

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"

	"github.com/ashie/gosearch/internal/contracts"
	"github.com/PuerkitoBio/goquery"
)

// QwantEngine implements a SearXNG-like `qwant` (web) adapter using
// Qwant v3 endpoint: https://api.qwant.com/v3/search/web.
//
// Qwant's API is not fully documented; this mirrors SearXNG's parsing logic
// for the `web` category from `.agent/searxng/searx/engines/qwant.py`.
type QwantEngine struct {
	client        *http.Client
	category      string // "web" (JSON API) or "web-lite" (HTML fallback)
	resultsPerPage int
}

func (e *QwantEngine) Name() string { return "qwant" }

func (e *QwantEngine) Search(ctx context.Context, req contracts.SearchRequest) (contracts.SearchResponse, error) {
	if e == nil || e.client == nil {
		return contracts.SearchResponse{}, errors.New("qwant engine not initialized")
	}

	q := strings.TrimSpace(req.Query)
	if q == "" {
		return contracts.SearchResponse{Query: req.Query}, nil
	}

	// For API parity we use SearXNG web defaults: count=10, offset=(pageno-1)*count.
	// The engine's config field exists so we can expand to news/images/videos later.
	count := e.resultsPerPage
	if count <= 0 {
		count = 10
	}
	offset := 0
	if req.Pageno > 1 {
		offset = (req.Pageno - 1) * count
	}
	mode := strings.TrimSpace(strings.ToLower(e.category))
	if mode == "" {
		mode = "web"
	}

	switch mode {
	case "web-lite":
		return e.searchWebLite(ctx, req)
	case "web":
		return e.searchWebAPI(ctx, req, count, offset)
	default:
		// Unknown mode: treat as unresponsive.
		return contracts.SearchResponse{
			Query: req.Query,
			UnresponsiveEngines: [][2]string{
				{e.Name(), "unknown_qwant_mode"},
			},
			Results:    []contracts.MainResult{},
			Answers:    []map[string]any{},
			Corrections: []string{},
			Infoboxes:  []map[string]any{},
			Suggestions: []string{},
		}, nil
	}
}

func (e *QwantEngine) searchWebAPI(ctx context.Context, req contracts.SearchRequest, count, offset int) (contracts.SearchResponse, error) {
	qLocale := qwantLocale(req.Language)
	args := url.Values{}
	args.Set("q", req.Query)
	args.Set("count", fmt.Sprintf("%d", count))
	args.Set("locale", qLocale)
	args.Set("safesearch", fmt.Sprintf("%d", req.Safesearch))
	args.Set("llm", "false")
	args.Set("tgp", "3")
	args.Set("offset", fmt.Sprintf("%d", offset))

	endpoint := "https://api.qwant.com/v3/search/web?" + args.Encode()

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	httpReq.Header.Set("User-Agent", "gosearch-go/0.1 (+https://github.com/ashie/gosearch)")

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

	// Qwant often returns a 403 captcha/JS block for the JSON API.
	if resp.StatusCode == http.StatusForbidden {
		return contracts.SearchResponse{
			Query: req.Query,
			UnresponsiveEngines: [][2]string{
				{e.Name(), "captcha_or_js_block"},
			},
			Results:    []contracts.MainResult{},
			Answers:    []map[string]any{},
			Corrections: []string{},
			Infoboxes:  []map[string]any{},
			Suggestions: []string{},
		}, nil
	}

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 16*1024))
		return contracts.SearchResponse{}, fmt.Errorf("qwant upstream error: status=%d body=%q", resp.StatusCode, string(body))
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
	if err != nil {
		return contracts.SearchResponse{}, err
	}

	var top map[string]any
	if err := json.Unmarshal(body, &top); err != nil {
		return contracts.SearchResponse{}, err
	}

	status, _ := top["status"].(string)
	if status != "success" {
		return contracts.SearchResponse{
			Query: req.Query,
			UnresponsiveEngines: [][2]string{
				{e.Name(), "api_error"},
			},
			Results:    []contracts.MainResult{},
			Answers:    []map[string]any{},
			Corrections: []string{},
			Infoboxes:  []map[string]any{},
			Suggestions: []string{},
		}, nil
	}

	data, _ := top["data"].(map[string]any)
	result, _ := data["result"].(map[string]any)
	items, _ := result["items"].(map[string]any)
	mainline := items["mainline"]

	rows := toSlice(mainline)
	if len(rows) == 0 {
		return contracts.SearchResponse{
			Query: req.Query,
			NumberOfResults: 0,
			Results: []contracts.MainResult{},
			Answers: []map[string]any{},
			Corrections: []string{},
			Infoboxes: []map[string]any{},
			Suggestions: []string{},
			UnresponsiveEngines: [][2]string{},
		}, nil
	}

	results := make([]contracts.MainResult, 0, len(rows))
	for _, row := range rows {
		rowMap, ok := row.(map[string]any)
		if !ok {
			continue
		}

		rowType, _ := rowMap["type"].(string)
		if rowType == "" {
			rowType = "web"
		}
		if rowType != "web" {
			continue
		}
		if rowType == "ads" {
			continue
		}

		rowItems := toSlice(rowMap["items"])
		for _, it := range rowItems {
			itemMap, ok := it.(map[string]any)
			if !ok {
				continue
			}
			title := toString(itemMap["title"])
			resURL := toString(itemMap["url"])
			desc := toString(itemMap["desc"])
			if resURL == "" {
				continue
			}
			urlPtr := resURL
			results = append(results, contracts.MainResult{
				Template: "default.html",
				Title:    title,
				Content:  desc,
				URL:      &urlPtr,
				Engine:   e.Name(),
				Score:    0,
				Category: "general",
				Engines:  []string{e.Name()},
			})
		}
	}

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

func (e *QwantEngine) searchWebLite(ctx context.Context, req contracts.SearchRequest) (contracts.SearchResponse, error) {
	qLocale := qwantLocale(req.Language)
	langBase := strings.SplitN(qLocale, "_", 2)[0]

	args := url.Values{}
	args.Set("q", req.Query)
	args.Set("locale", strings.ToLower(qLocale))
	args.Set("l", langBase)
	args.Set("s", fmt.Sprintf("%d", req.Safesearch))
	args.Set("p", fmt.Sprintf("%d", req.Pageno))

	endpoint := "https://lite.qwant.com/?" + args.Encode()
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	httpReq.Header.Set("User-Agent", "gosearch-go/0.1 (+https://github.com/ashie/gosearch)")

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

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 16*1024))
		return contracts.SearchResponse{}, fmt.Errorf("qwant lite upstream error: status=%d body=%q", resp.StatusCode, string(body))
	}

	doc, err := goquery.NewDocumentFromReader(resp.Body)
	if err != nil {
		return contracts.SearchResponse{}, err
	}

	results := make([]contracts.MainResult, 0)
	seen := map[string]bool{}

	// Pattern 1: legacy/known qwant-lite structure.
	doc.Find("section article").Each(func(_ int, item *goquery.Selection) {
		// ignore randomly interspersed advertising adds
		if item.Find("span.tooltip").Length() > 0 {
			return
		}

		// In SearXNG: "./span[contains(@class, 'url partner')]"
		urlText := strings.TrimSpace(item.Find("span.url.partner").First().Text())
		if urlText == "" {
			// fallback: any span with class containing both 'url' and 'partner'
			urlText = strings.TrimSpace(item.Find("span[class*='url'][class*='partner']").First().Text())
		}
		title := strings.TrimSpace(item.Find("h2 a").First().Text())
		content := strings.TrimSpace(item.Find("p").First().Text())

		if urlText == "" {
			return
		}
		if seen[urlText] {
			return
		}
		seen[urlText] = true
		u := urlText
		results = append(results, contracts.MainResult{
			Template: "default.html",
			Title:    title,
			Content:  content,
			URL:      &u,
			Engine:   e.Name(),
			Score:    0,
			Category: "general",
			Engines:  []string{e.Name()},
		})
	})

	// Pattern 2: broader fallback for updated lite markup:
	// any article/list item/div block containing an external anchor.
	// We keep this conservative by requiring non-empty title + URL.
	doc.Find("article, li, div").Each(func(_ int, item *goquery.Selection) {
		if len(results) >= 20 {
			return
		}
		// Skip ad-like blocks in fallback pass too.
		if item.Find("span.tooltip").Length() > 0 {
			return
		}

		// Skip obvious nav/footer blocks.
		classAttr, _ := item.Attr("class")
		classLower := strings.ToLower(classAttr)
		if strings.Contains(classLower, "nav") || strings.Contains(classLower, "footer") {
			return
		}

		a := item.Find("a[href]").First()
		if a.Length() == 0 {
			return
		}
		href, ok := a.Attr("href")
		if !ok {
			return
		}
		href = strings.TrimSpace(href)
		if href == "" {
			return
		}

		// Ignore in-page and relative links.
		if strings.HasPrefix(href, "/") || strings.HasPrefix(href, "#") {
			return
		}
		if !strings.HasPrefix(href, "http://") && !strings.HasPrefix(href, "https://") {
			return
		}
		// Skip known sponsored partner links surfaced in lite pages.
		if isKnownSponsoredURL(href) {
			return
		}
		if isQwantInternalURL(href) {
			// Ignore qwant nav/house links.
			return
		}

		title := strings.TrimSpace(a.Text())
		if title == "" {
			return
		}
		if isLikelyNavTitle(title) {
			return
		}

		if seen[href] {
			return
		}
		seen[href] = true

		// Best-effort snippet extraction from nearby paragraph/span text.
		content := strings.TrimSpace(item.Find("p").First().Text())
		if content == "" {
			content = strings.TrimSpace(item.Find("span").First().Text())
		}
		// If there is no snippet, still keep clearly external result links.
		// Qwant-lite frequently omits rich snippets for some entries.

		u := href
		results = append(results, contracts.MainResult{
			Template: "default.html",
			Title:    title,
			Content:  content,
			URL:      &u,
			Engine:   e.Name(),
			Score:    0,
			Category: "general",
			Engines:  []string{e.Name()},
		})
	})

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

func qwantLocale(lang string) string {
	lang = strings.TrimSpace(lang)
	if lang == "" || lang == "auto" {
		return "en_US"
	}
	lang = strings.ReplaceAll(lang, "-", "_")
	parts := strings.SplitN(lang, "_", 2)
	base := strings.ToLower(parts[0])
	country := "US"
	if len(parts) == 2 && strings.TrimSpace(parts[1]) != "" {
		country = strings.ToUpper(strings.TrimSpace(parts[1]))
	}
	// Qwant expects locales like en_US.
	return base + "_" + country
}

func toSlice(v any) []any {
	switch t := v.(type) {
	case []any:
		return t
	default:
		// Handle case where mainline might be a single object.
		if m, ok := v.(map[string]any); ok {
			return []any{m}
		}
		return nil
	}
}

func toString(v any) string {
	switch t := v.(type) {
	case string:
		return t
	case json.Number:
		return t.String()
	default:
		return ""
	}
}

func isQwantInternalURL(raw string) bool {
	u, err := url.Parse(raw)
	if err != nil {
		return false
	}
	host := strings.ToLower(u.Hostname())
	if host == "" {
		return false
	}
	return host == "qwant.com" || host == "www.qwant.com" || strings.HasSuffix(host, ".qwant.com") || host == "about.qwant.com"
}

func isLikelyNavTitle(title string) bool {
	t := strings.TrimSpace(strings.ToLower(title))
	switch t {
	case "qwant search", "search", "privacy", "discover the service", "better web", "discover":
		return true
	}
	if strings.HasPrefix(t, "get 20gb of free storage") {
		return true
	}
	return false
}

func isKnownSponsoredURL(raw string) bool {
	u, err := url.Parse(raw)
	if err != nil {
		return false
	}
	host := strings.ToLower(u.Hostname())
	switch host {
	case "shdw.me", "www.shdw.me":
		return true
	}
	if strings.Contains(strings.ToLower(raw), "qwant-tool") {
		return true
	}
	return false
}