// Podcast feed poller (plan §7 task 1.6): one periodic worker ticking
// on the podcast_poll_interval_seconds system setting (re-read each
// cycle — the settings API path keeps the registry cache honest),
// polling every non-complete feed and applying subscriber auto-download
// policies after each successful fetch (D6).
//
// RLS: detached work under the first-admin identity — the service's
// adminCtx supplies it (invariant 12). Back-off: itunes:complete feeds
// are skipped by the ticker (explicit refresh still works).
package services

import (
	"context"
	"log"
	"time"

	"bookhoard/internal/database"
)

type PodcastPoller struct {
	db       *database.Queries
	svc      *PodcastService
	worker   *PodcastDownloadWorker
	settings *database.SettingsRegistry
}

func NewPodcastPoller(db *database.Queries, svc *PodcastService, worker *PodcastDownloadWorker, settings *database.SettingsRegistry) *PodcastPoller {
	return &PodcastPoller{db: db, svc: svc, worker: worker, settings: settings}
}

// Start launches the poll loop; exits when ctx is cancelled.
func (p *PodcastPoller) Start(ctx context.Context) {
	go func() {
		for {
			interval := p.settings.PodcastPollInterval()
			if interval < time.Minute {
				interval = time.Minute // floor against bad settings rows
			}
			select {
			case <-ctx.Done():
				return
			case <-time.After(interval):
			}
			p.tick(ctx)
		}
	}()
}

// tick polls every non-complete feed once.
func (p *PodcastPoller) tick(ctx context.Context) {
	actx, err := p.svc.adminCtx(ctx)
	if err != nil {
		log.Printf("[PODCAST-POLL] no acting identity, skipping tick: %v", err)
		return
	}
	feeds, err := p.db.ListPodcastFeedsForPolling(actx)
	if err != nil {
		log.Printf("[PODCAST-POLL] worklist: %v", err)
		return
	}
	for _, feed := range feeds {
		if ctx.Err() != nil {
			return
		}
		if feed.IsComplete {
			continue // back off ended feeds (explicit refresh still works)
		}
		if err := p.svc.PollFeed(actx, &feed); err != nil {
			log.Printf("[PODCAST-POLL] %s: %v", feed.Title, err)
			continue
		}
		// Fresh episodes → apply the subscriber policy union (auto-
		// download without waiting for the next tick).
		if _, err := p.worker.ApplyAutoPolicies(actx, feed.ID); err != nil {
			log.Printf("[PODCAST-POLL] auto-download policies for %s: %v", feed.Title, err)
		}
	}
}