package sources

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

	"golang.org/x/time/rate"

	"github.com/salvacybersec/keyhunter/pkg/providers"
	"github.com/salvacybersec/keyhunter/pkg/recon"
)

// PastebinSource scrapes pastebin.com search results for API key leaks.
//
// Two-phase approach per keyword:
//   - Phase A: search pastebin for keyword, extract paste IDs from result links
//   - Phase B: fetch raw paste content, keyword-match against provider registry
//
// Auth: none (credential-free). Rate: Every(3s), Burst 1 (conservative scraping).
type PastebinSource struct {
	BaseURL  string
	Registry *providers.Registry
	Limiters *recon.LimiterRegistry
	Client   *Client
}

// pastebinIDRE matches Pastebin paste links: /XXXXXXXX (8 alphanumeric chars).
var pastebinIDRE = regexp.MustCompile(`^/[A-Za-z0-9]{8}$`)

// Compile-time assertion.
var _ recon.ReconSource = (*PastebinSource)(nil)

func (s *PastebinSource) Name() string          { return "pastebin" }
func (s *PastebinSource) RateLimit() rate.Limit { return rate.Every(3 * time.Second) }
func (s *PastebinSource) Burst() int            { return 1 }
func (s *PastebinSource) RespectsRobots() bool  { return true }

// Enabled always returns true: Pastebin scraping requires no credentials.
func (s *PastebinSource) Enabled(_ recon.Config) bool { return true }

// Sweep searches Pastebin for each provider keyword and scans raw paste content.
func (s *PastebinSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
	base := s.BaseURL
	if base == "" {
		base = "https://pastebin.com"
	}
	client := s.Client
	if client == nil {
		client = NewClient()
	}

	queries := BuildQueries(s.Registry, "pastebin")
	if len(queries) == 0 {
		return nil
	}

	keywords := pastebinKeywordSet(s.Registry)
	if len(keywords) == 0 {
		return nil
	}

	for _, q := range queries {
		if err := ctx.Err(); err != nil {
			return err
		}
		if s.Limiters != nil {
			if err := s.Limiters.Wait(ctx, s.Name(), s.RateLimit(), s.Burst(), false); err != nil {
				return err
			}
		}

		// Phase A: search for paste links.
		searchURL := fmt.Sprintf("%s/search?q=%s", base, url.QueryEscape(q))
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, searchURL, nil)
		if err != nil {
			return fmt.Errorf("pastebin: build search req: %w", err)
		}
		resp, err := client.Do(ctx, req)
		if err != nil {
			return fmt.Errorf("pastebin: search fetch: %w", err)
		}
		ids, err := extractAnchorHrefs(resp.Body, pastebinIDRE)
		_ = resp.Body.Close()
		if err != nil {
			return fmt.Errorf("pastebin: parse search html: %w", err)
		}

		// Phase B: fetch raw content and keyword-match.
		for _, idPath := range ids {
			if err := ctx.Err(); err != nil {
				return err
			}
			if s.Limiters != nil {
				if err := s.Limiters.Wait(ctx, s.Name(), s.RateLimit(), s.Burst(), false); err != nil {
					return err
				}
			}

			rawURL := fmt.Sprintf("%s/raw%s", base, idPath)
			rawReq, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
			if err != nil {
				return fmt.Errorf("pastebin: build raw req: %w", err)
			}
			rawResp, err := client.Do(ctx, rawReq)
			if err != nil {
				// Skip this paste on fetch error, continue to next.
				continue
			}
			body, readErr := io.ReadAll(io.LimitReader(rawResp.Body, 256*1024))
			_ = rawResp.Body.Close()
			if readErr != nil {
				continue
			}

			content := string(body)
			for kw, provName := range keywords {
				if strings.Contains(content, kw) {
					out <- recon.Finding{
						ProviderName: provName,
						Source:       fmt.Sprintf("%s%s", base, idPath),
						SourceType:   "recon:pastebin",
						Confidence:   "low",
						DetectedAt:   time.Now(),
					}
					break // one finding per paste
				}
			}
		}
	}
	return nil
}

// pastebinKeywordSet builds keyword->providerName map from registry.
func pastebinKeywordSet(reg *providers.Registry) map[string]string {
	out := make(map[string]string)
	if reg == nil {
		return out
	}
	for _, p := range reg.List() {
		for _, k := range p.Keywords {
			if k == "" {
				continue
			}
			if _, ok := out[k]; !ok {
				out[k] = p.Name
			}
		}
	}
	return out
}