package checker

import (
	"context"
	"net/url"
	"strings"
	"sync"
	"time"
)

// feedCache is a generic URL-feed cache shared between phishing-feed
// sources (OpenPhish, PhishTank). It holds a hostname-indexed snapshot
// of the feed, refreshes on TTL expiry, and ensures only one refresh is
// in flight at a time so concurrent lookups still serve stale data
// during a refresh.
type feedCache struct {
	mu            sync.Mutex
	urls          []string
	byHost        map[string][]string
	fetchedAt     time.Time
	lastAttemptAt time.Time
	refreshing    bool
	ttl           time.Duration
	failBackoff   time.Duration
	fetchFn       func(ctx context.Context) (urls []string, byHost map[string][]string, err error)
}

func newFeedCache(ttl time.Duration, fetch func(context.Context) ([]string, map[string][]string, error)) *feedCache {
	if ttl <= 0 {
		ttl = time.Hour
	}
	return &feedCache{
		ttl:         ttl,
		failBackoff: time.Minute,
		fetchFn:     fetch,
	}
}

func (c *feedCache) setTTL(d time.Duration) {
	c.mu.Lock()
	c.ttl = d
	c.mu.Unlock()
}

func (c *feedCache) lookup(ctx context.Context, domain string) (urls []string, size int, fetchedAt time.Time, err error) {
	domain = strings.ToLower(strings.TrimSuffix(domain, "."))

	c.mu.Lock()
	stale := c.byHost == nil || time.Since(c.fetchedAt) > c.ttl
	doRefresh := stale && !c.refreshing && time.Since(c.lastAttemptAt) > c.failBackoff
	if doRefresh {
		c.refreshing = true
	}
	c.mu.Unlock()

	if doRefresh {
		newURLs, newByHost, ferr := c.fetchFn(ctx)
		c.mu.Lock()
		c.refreshing = false
		c.lastAttemptAt = time.Now()
		if ferr == nil {
			c.urls = newURLs
			c.byHost = newByHost
			c.fetchedAt = c.lastAttemptAt
		} else {
			err = ferr
		}
		c.mu.Unlock()
	}

	c.mu.Lock()
	for host, hostURLs := range c.byHost {
		if host == domain || strings.HasSuffix(host, "."+domain) {
			urls = append(urls, hostURLs...)
		}
	}
	size = len(c.urls)
	fetchedAt = c.fetchedAt
	c.mu.Unlock()
	return urls, size, fetchedAt, err
}

func hostOfURL(s string) string {
	u, err := url.Parse(s)
	if err != nil {
		return ""
	}
	return strings.ToLower(u.Hostname())
}