veola/internal/handlers/preview_cache.go

package handlers

import (
	"sync"
	"time"

	"veola/internal/apify"
)

// previewKey caches the *raw* apify result set (post-decode, post-merge,
// pre-filter). Filters like min_price and exclude_keywords are applied after
// the cache lookup so the operator can iterate on them without burning credits.
//
// Condition and Region are part of the key, not post-filters: they are
// server-side eBay Browse API filters that change the result set the API
// returns, so a different condition/region must miss the cache.
type previewKey struct {
	Queries, URL, Marketplace, ListingType, ActorIDs string
	Condition, Region                                string
	MaxResults                                       int
}

type previewEntry struct {
	results []apify.UnifiedResult
	source  string
	stored  time.Time
}

type PreviewCache struct {
	ttl     time.Duration
	mu      sync.Mutex
	entries map[previewKey]previewEntry
}

func NewPreviewCache(ttl time.Duration) *PreviewCache {
	return &PreviewCache{
		ttl:     ttl,
		entries: make(map[previewKey]previewEntry),
	}
}

func (c *PreviewCache) Get(k previewKey) ([]apify.UnifiedResult, string, bool) {
	c.mu.Lock()
	defer c.mu.Unlock()
	e, ok := c.entries[k]
	if !ok {
		return nil, "", false
	}
	if time.Since(e.stored) > c.ttl {
		delete(c.entries, k)
		return nil, "", false
	}
	return e.results, e.source, true
}

func (c *PreviewCache) Put(k previewKey, results []apify.UnifiedResult, source string) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.entries[k] = previewEntry{results: results, source: source, stored: time.Now()}
	if len(c.entries) > 64 {
		c.evictExpired()
	}
}

func (c *PreviewCache) evictExpired() {
	for k, e := range c.entries {
		if time.Since(e.stored) > c.ttl {
			delete(c.entries, k)
		}
	}
}