package placement

import (
	"context"
	"math/rand"
	"sync"
	"time"
)

const (
	CrawlerMinQueryInterval = 8 * time.Second
	CrawlerMaxQueryJitter   = 4 * time.Second
)

// WrapPoliteCrawler spaces out Playwright keyword searches to reduce Threads rate limits.
func WrapPoliteCrawler(inner CrawlerSearchFn) CrawlerSearchFn {
	if inner == nil {
		return nil
	}
	guard := &crawlerPacing{inner: inner}
	return guard.search
}

type crawlerPacing struct {
	inner CrawlerSearchFn
	mu    sync.Mutex
	last  time.Time
}

func (p *crawlerPacing) search(ctx context.Context, member MemberContext, keyword string, limit int) ([]DiscoverPost, error) {
	p.mu.Lock()
	defer p.mu.Unlock()

	if !p.last.IsZero() {
		elapsed := time.Since(p.last)
		wait := CrawlerMinQueryInterval + jitterDuration(CrawlerMaxQueryJitter) - elapsed
		if wait > 0 {
			timer := time.NewTimer(wait)
			defer timer.Stop()
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-timer.C:
			}
		}
	}

	posts, err := p.inner(ctx, member, keyword, limit)
	p.last = time.Now()
	return posts, err
}

func jitterDuration(max time.Duration) time.Duration {
	if max <= 0 {
		return 0
	}
	return time.Duration(rand.Int63n(int64(max)))
}