samsa/internal/engines/brave.go

package engines

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

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

type BraveEngine struct {
	client *http.Client
}

func (e *BraveEngine) Name() string { return "brave" }

func (e *BraveEngine) 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) * 20
	u := fmt.Sprintf(
		"https://search.brave.com/search?q=%s&offset=%d&source=web",
		url.QueryEscape(req.Query),
		start,
	)

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	httpReq.Header.Set("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36")
	httpReq.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8")
	httpReq.Header.Set("Accept-Language", "en-US,en;q=0.9")

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

	if resp.StatusCode != http.StatusOK {
		io.Copy(io.Discard, io.LimitReader(resp.Body, 4096))
		return contracts.SearchResponse{}, fmt.Errorf("brave error: status %d", resp.StatusCode)
	}

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

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

func parseBraveResults(body string) []contracts.MainResult {
	var results []contracts.MainResult

	// Brave wraps each result in divs with data-type="web" or data-type="news".
	// Pattern: <div ... data-type="web"> ... <a class="result-title" href="URL">TITLE</a> ... <div class="snippet">SNIPPET</div>
	webPattern := regexp.MustCompile(`(?s)<div[^>]+data-type="web"[^>]*>(.*?)</div>\s*<div[^>]+data-type="(web|news)"`)
	matches := webPattern.FindAllStringSubmatch(body, -1)

	seen := map[string]bool{}

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

		// Extract title and URL from the result-title link.
		titlePattern := regexp.MustCompile(`<a[^>]+class="result-title"[^>]+href="([^"]+)"[^>]*>([^<]+)</a>`)
		titleMatch := titlePattern.FindStringSubmatch(block)
		if titleMatch == nil {
			continue
		}
		href := titleMatch[1]
		title := stripTags(titleMatch[2])

		if href == "" || !strings.HasPrefix(href, "http") {
			continue
		}
		if seen[href] {
			continue
		}
		seen[href] = true

		// Extract snippet.
		snippet := extractBraveSnippet(block)

		// Extract favicon URL.
		favicon := extractBraveFavicon(block)

		urlPtr := href
		results = append(results, contracts.MainResult{
			Title:     title,
			URL:       &urlPtr,
			Content:   snippet,
			Thumbnail: favicon,
			Engine:    "brave",
			Score:     1.0,
			Category:  "general",
			Engines:   []string{"brave"},
		})
	}

	return results
}

func extractBraveSnippet(block string) string {
	// Try various snippet selectors Brave uses.
	patterns := []string{
		`<div[^>]+class="snippet"[^>]*>(.*?)</div>`,
		`<p[^>]+class="[^"]*description[^"]*"[^>]*>(.*?)</p>`,
		`<span[^>]+class="[^"]*snippet[^"]*"[^>]*>(.*?)</span>`,
	}

	for _, pat := range patterns {
		re := regexp.MustCompile(`(?s)` + pat)
		m := re.FindStringSubmatch(block)
		if len(m) >= 2 {
			text := stripTags(m[1])
			if text != "" {
				return strings.TrimSpace(text)
			}
		}
	}
	return ""
}

func extractBraveFavicon(block string) string {
	imgPattern := regexp.MustCompile(`<img[^>]+class="[^"]*favicon[^"]*"[^>]+src="([^"]+)"`)
	m := imgPattern.FindStringSubmatch(block)
	if len(m) >= 2 {
		return m[1]
	}
	return ""
}

func extractBraveSuggestions(body string) []string {
	var suggestions []string
	// Brave suggestions appear in a dropdown or related searches section.
	suggestPattern := regexp.MustCompile(`(?s)<li[^>]+class="[^"]*suggestion[^"]*"[^>]*>.*?<a[^>]*>([^<]+)</a>`)
	matches := suggestPattern.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
}