package runner

// catalogue_refresh.go — independent loop that walks the full novelfire.net
// catalogue, scrapes per-book metadata, downloads cover images to MinIO, and
// indexes every book in Meilisearch.
//
// Design:
//   - Runs on its own ticker (CatalogueRefreshInterval, default 24h) inside Run().
//   - Also fires once on startup.
//   - ScrapeCatalogue streams CatalogueEntry values over a channel — we iterate
//     and call ScrapeMetadata for each entry.
//   - Per-request random jitter (1–3s) prevents hammering novelfire.net.
//   - Cover images are fetched from the URL embedded in BookMeta.Cover and
//     stored in MinIO (browse bucket, key: covers/{slug}.jpg).
//   - WriteMetadata + UpsertBook are called for every successfully scraped book.
//   - Errors for individual books are logged and skipped; the loop continues.
//   - The cover URL stored in BookMeta.Cover is rewritten to the internal proxy
//     path (/api/cover/novelfire.net/{slug}) so the UI always fetches via the
//     backend, which will serve from MinIO.

import (
	"context"
	"fmt"
	"io"
	"math/rand"
	"net/http"
	"time"
)

// runCatalogueRefresh performs one full catalogue walk: scrapes metadata for
// every book on novelfire.net, downloads covers to MinIO, and upserts to
// Meilisearch. Errors for individual books are logged and skipped.
func (r *Runner) runCatalogueRefresh(ctx context.Context) {
	if r.deps.Novel == nil {
		r.deps.Log.Warn("runner: catalogue refresh skipped — Novel scraper not configured")
		return
	}
	if r.deps.BookWriter == nil {
		r.deps.Log.Warn("runner: catalogue refresh skipped — BookWriter not configured")
		return
	}

	log := r.deps.Log.With("op", "catalogue_refresh")
	log.Info("runner: catalogue refresh starting")

	entries, errCh := r.deps.Novel.ScrapeCatalogue(ctx)

	ok, skipped, errCount := 0, 0, 0
	for entry := range entries {
		if ctx.Err() != nil {
			break
		}

		// Skip books already present in Meilisearch — they were indexed on a
		// previous run. Re-indexing only happens when a scrape task is
		// explicitly enqueued (e.g. via the admin UI or API).
		if r.deps.SearchIndex.BookExists(ctx, entry.Slug) {
			skipped++
			continue
		}

		// Random jitter between books to avoid rate-limiting.
		jitter := time.Duration(1000+rand.Intn(2000)) * time.Millisecond
		select {
		case <-ctx.Done():
			break
		case <-time.After(jitter):
		}

		meta, err := r.deps.Novel.ScrapeMetadata(ctx, entry.URL)
		if err != nil {
			log.Warn("runner: catalogue refresh: metadata scrape failed",
				"url", entry.URL, "err", err)
			errCount++
			continue
		}

		// Rewrite cover URL to backend proxy path so UI never hits CDN directly.
		originalCover := meta.Cover
		meta.Cover = fmt.Sprintf("/api/cover/novelfire.net/%s", meta.Slug)

		// Persist to PocketBase.
		if err := r.deps.BookWriter.WriteMetadata(ctx, meta); err != nil {
			log.Warn("runner: catalogue refresh: WriteMetadata failed",
				"slug", meta.Slug, "err", err)
			errCount++
			continue
		}

		// Index in Meilisearch.
		if err := r.deps.SearchIndex.UpsertBook(ctx, meta); err != nil {
			log.Warn("runner: catalogue refresh: UpsertBook failed",
				"slug", meta.Slug, "err", err)
			// non-fatal — continue
		}

		// Download and store cover image in MinIO if we have a cover URL
		// and a CoverStore is wired in.
		if r.deps.CoverStore != nil && originalCover != "" {
			if !r.deps.CoverStore.CoverExists(ctx, meta.Slug) {
				if err := r.downloadCover(ctx, meta.Slug, originalCover); err != nil {
					log.Warn("runner: catalogue refresh: cover download failed",
						"slug", meta.Slug, "url", originalCover, "err", err)
					// non-fatal
				}
			}
		}

		ok++
		if ok%100 == 0 {
			log.Info("runner: catalogue refresh progress",
				"scraped", ok, "errors", errCount)
		}
	}

	if err := <-errCh; err != nil {
		log.Warn("runner: catalogue refresh: catalogue stream error", "err", err)
	}

	log.Info("runner: catalogue refresh finished",
		"ok", ok, "skipped", skipped, "errors", errCount)
}

// downloadCover fetches the cover image from coverURL and stores it in MinIO
// under covers/{slug}.jpg. It retries up to 3 times with exponential backoff
// on transient errors (5xx, network failures).
func (r *Runner) downloadCover(ctx context.Context, slug, coverURL string) error {
	const maxRetries = 3
	delay := 2 * time.Second

	var lastErr error
	for attempt := 0; attempt < maxRetries; attempt++ {
		if ctx.Err() != nil {
			return ctx.Err()
		}
		if attempt > 0 {
			select {
			case <-ctx.Done():
				return ctx.Err()
			case <-time.After(delay):
			}
			delay *= 2
		}

		data, err := fetchCoverBytes(ctx, coverURL)
		if err != nil {
			lastErr = err
			continue
		}

		if err := r.deps.CoverStore.PutCover(ctx, slug, data, ""); err != nil {
			return fmt.Errorf("put cover: %w", err)
		}
		return nil
	}
	return fmt.Errorf("download cover after %d retries: %w", maxRetries, lastErr)
}

// fetchCoverBytes performs a single HTTP GET for coverURL and returns the body.
func fetchCoverBytes(ctx context.Context, coverURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, coverURL, nil)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("User-Agent", "Mozilla/5.0 (compatible; libnovel-runner/2)")
	req.Header.Set("Referer", "https://novelfire.net/")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("http get: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 500 {
		_, _ = io.Copy(io.Discard, resp.Body)
		return nil, fmt.Errorf("upstream %d for %s", resp.StatusCode, coverURL)
	}
	if resp.StatusCode != http.StatusOK {
		_, _ = io.Copy(io.Discard, resp.Body)
		return nil, fmt.Errorf("unexpected status %d for %s", resp.StatusCode, coverURL)
	}

	return io.ReadAll(io.LimitReader(resp.Body, 5<<20)) // 5 MiB cap
}