package sources

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

	"golang.org/x/time/rate"

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

// GitHubSource implements recon.ReconSource against the GitHub Code Search
// REST API. It iterates provider keyword queries (via BuildQueries) and emits
// a recon.Finding for every /search/code item returned.
//
// RECON-CODE-01: refactors the logic from pkg/dorks/github.go (Phase 8's
// GitHubExecutor) into the Phase 10 recon framework. Retries/429/5xx handling
// is delegated to the shared sources.Client; per-source rate limiting is
// delegated to recon.LimiterRegistry. Registration with recon.Engine happens
// in Plan 10-09.
//
// A missing token disables the source — Sweep returns nil and Enabled reports
// false. This keeps GitHub optional in sweeps that only need credential-free
// sources (Codeberg, Replit, etc.).
type GitHubSource struct {
	Token    string
	BaseURL  string
	Registry *providers.Registry
	Limiters *recon.LimiterRegistry
	client   *Client
}

// NewGitHubSource constructs a GitHubSource pointing at api.github.com with
// the shared retry/backoff HTTP client.
func NewGitHubSource(token string, reg *providers.Registry, lim *recon.LimiterRegistry) *GitHubSource {
	return &GitHubSource{
		Token:    token,
		BaseURL:  "https://api.github.com",
		Registry: reg,
		Limiters: lim,
		client:   NewClient(),
	}
}

// Name returns the stable source identifier used by the engine and limiter
// registry.
func (s *GitHubSource) Name() string { return "github" }

// RateLimit returns 1 request every 2 seconds — GitHub's authenticated code
// search endpoint allows 30 req/min.
func (s *GitHubSource) RateLimit() rate.Limit { return rate.Every(2 * time.Second) }

// Burst returns 1; GitHub code search does not tolerate bursts.
func (s *GitHubSource) Burst() int { return 1 }

// RespectsRobots is false — this source talks to an authenticated REST API,
// not a scraped website.
func (s *GitHubSource) RespectsRobots() bool { return false }

// Enabled returns true only when a token is configured. A missing token is not
// an error — the source is simply skipped.
func (s *GitHubSource) Enabled(_ recon.Config) bool { return s.Token != "" }

// Sweep issues one /search/code request per provider keyword and emits a
// Finding for every item returned. The `query` parameter is ignored because
// GitHubSource builds its own queries from the provider registry; this keeps
// recon.Engine's common signature.
func (s *GitHubSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
	if s.Token == "" {
		return nil
	}
	base := s.BaseURL
	if base == "" {
		base = "https://api.github.com"
	}

	queries := BuildQueries(s.Registry, "github")
	kwIndex := githubKeywordIndex(s.Registry)

	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
			}
		}

		endpoint := fmt.Sprintf("%s/search/code?q=%s&per_page=30", base, url.QueryEscape(q))
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
		if err != nil {
			return fmt.Errorf("github: build request: %w", err)
		}
		req.Header.Set("Accept", "application/vnd.github.v3.text-match+json")
		req.Header.Set("Authorization", "Bearer "+s.Token)
		req.Header.Set("User-Agent", "keyhunter-recon")

		resp, err := s.client.Do(ctx, req)
		if err != nil {
			// 401 → unauthorized, abort the whole sweep (token is bad).
			if errors.Is(err, ErrUnauthorized) {
				return err
			}
			// Ctx cancellation during retry backoff also aborts.
			if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
				return err
			}
			// Transient failures: log-and-continue per Phase 10 context
			// (sources downgrade, not abort the whole sweep).
			continue
		}

		var parsed ghSearchResponse
		decErr := json.NewDecoder(resp.Body).Decode(&parsed)
		_ = resp.Body.Close()
		if decErr != nil {
			continue
		}

		provName := kwIndex[strings.ToLower(extractGitHubKeyword(q))]
		for _, it := range parsed.Items {
			f := recon.Finding{
				ProviderName: provName,
				Confidence:   "low",
				Source:       it.HTMLURL,
				SourceType:   "recon:github",
				DetectedAt:   time.Now(),
			}
			select {
			case out <- f:
			case <-ctx.Done():
				return ctx.Err()
			}
		}
	}
	return nil
}

// ghSearchResponse mirrors the subset of GitHub's /search/code JSON response
// that this source consumes. It is kept private to avoid cross-package
// coupling with pkg/dorks (which carries its own identical shapes).
type ghSearchResponse struct {
	Items []ghCodeItem `json:"items"`
}

type ghCodeItem struct {
	HTMLURL     string             `json:"html_url"`
	Repository  ghRepository       `json:"repository"`
	TextMatches []ghTextMatchEntry `json:"text_matches"`
}

type ghRepository struct {
	FullName string `json:"full_name"`
}

type ghTextMatchEntry struct {
	Fragment string `json:"fragment"`
}

// githubKeywordIndex maps every provider keyword (lowercased) to its provider
// name for Finding.ProviderName population. A nil registry returns an empty
// map. Named distinctly from any sibling source's helper to avoid symbol
// collisions across the sources package.
func githubKeywordIndex(reg *providers.Registry) map[string]string {
	m := make(map[string]string)
	if reg == nil {
		return m
	}
	for _, p := range reg.List() {
		for _, k := range p.Keywords {
			kl := strings.ToLower(strings.TrimSpace(k))
			if kl == "" {
				continue
			}
			if _, exists := m[kl]; !exists {
				m[kl] = p.Name
			}
		}
	}
	return m
}

// extractGitHubKeyword reverses BuildQueries("github", k) — it strips the
// surrounding quotes and the trailing ` in:file` qualifier. For any other
// shape it falls back to the trimmed input so new formats degrade safely.
func extractGitHubKeyword(q string) string {
	s := strings.TrimSuffix(q, " in:file")
	s = strings.TrimPrefix(s, "\"")
	s = strings.TrimSuffix(s, "\"")
	return s
}