// selector_test.go：P2C + sticky LRU 单测（无外网，固定随机源）。
package proxymanager

import (
	"testing"
	"time"
)

// fixedRnd 固定序列随机源（可复现）。
func fixedRnd(seq []int) func(int) int {
	i := 0
	return func(n int) int {
		v := seq[i%len(seq)] % n
		i++
		return v
	}
}

func TestPickLowestDelay(t *testing.T) {
	cands := []string{"A", "B", "C"}
	delays := map[string]int{"A": 200, "B": 100, "C": 300}
	picked := Pick(cands, func(n string) int { return delays[n] }, fixedRnd([]int{0, 1}))
	if picked != "B" {
		t.Errorf("P2C picked = %s, want B(最低延迟)", picked)
	}
}

func TestPickUnknownDelayNotPreferred(t *testing.T) {
	// 未探测节点（<=0）视为最差：A 已探测 500ms，B 未探测 → 应选 A
	cands := []string{"A", "B"}
	picked := Pick(cands, func(n string) int {
		if n == "A" {
			return 500
		}
		return 0
	}, fixedRnd([]int{0, 1}))
	if picked != "A" {
		t.Errorf("picked = %s, want A（未探测节点不应霸占选择）", picked)
	}
}

func TestPickSingleCandidate(t *testing.T) {
	if got := Pick([]string{"only"}, func(string) int { return 1 }, fixedRnd([]int{0})); got != "only" {
		t.Errorf("单候选 picked = %s", got)
	}
	if got := Pick(nil, func(string) int { return 0 }, fixedRnd([]int{0})); got != "" {
		t.Errorf("空候选 picked = %q, want 空串", got)
	}
}

func TestPickNeverSameIndexTwice(t *testing.T) {
	// rnd 恒返同值时，两样本必须不同（j=(i+1)%n 兜底）
	cands := []string{"A", "B", "C"}
	delays := map[string]int{"A": 100, "B": 200, "C": 300}
	picked := Pick(cands, func(n string) int { return delays[n] }, func(int) int { return 0 })
	if picked != "A" {
		t.Errorf("picked = %s, want A（0 与 1 比较取低）", picked)
	}
}

func TestStickyTTLExpiry(t *testing.T) {
	s := NewStickyTable(time.Minute, 10)
	s.Set("k", "node1")
	if n, ok := s.Get("k"); !ok || n != "node1" {
		t.Fatalf("Get = %q,%v", n, ok)
	}
	// TTL 过期（直接改 ExpireAt 模拟时钟前进）
	s.mu.Lock()
	e := s.m["k"]
	e.ExpireAt = time.Now().Add(-time.Second)
	s.m["k"] = e
	s.mu.Unlock()
	if _, ok := s.Get("k"); ok {
		t.Fatal("过期条目应失效")
	}
}

func TestStickyLRUEviction(t *testing.T) {
	s := NewStickyTable(time.Hour, 3)
	s.Set("a", "1")
	s.Set("b", "2")
	s.Set("c", "3")
	s.Get("a") // touch a → b 变最旧
	s.Set("d", "4")
	if _, ok := s.Get("b"); ok {
		t.Fatal("LRU 应淘汰 b（容量 3）")
	}
	if _, ok := s.Get("a"); !ok {
		t.Fatal("a 被访问过不应被淘汰")
	}
	if s.Len() != 3 {
		t.Errorf("Len = %d, want 3", s.Len())
	}
}

func TestStickyReset(t *testing.T) {
	s := NewStickyTable(time.Hour, 10)
	s.Set("k", "v")
	s.Reset()
	if s.Len() != 0 {
		t.Fatal("Reset 后应为空")
	}
}

func TestStickyKey(t *testing.T) {
	if StickyKey("sess1", "d.com") != "s:sess1" {
		t.Error("session 优先")
	}
	if StickyKey("", "d.com") != "d:d.com" {
		t.Error("无 session 用 domain")
	}
}

func TestStickyDefaultCapacity(t *testing.T) {
	s := NewStickyTable(0, 0) // 走默认值：TTL 10min / 容量 1000
	for i := 0; i < 1200; i++ {
		s.Set(string(rune('a'+i%26))+itoa(i), "n")
	}
	if s.Len() > 1000 {
		t.Errorf("容量上限失效: Len=%d", s.Len())
	}
}

func itoa(n int) string {
	if n == 0 {
		return "0"
	}
	var b []byte
	for n > 0 {
		b = append([]byte{byte('0' + n%10)}, b...)
		n /= 10
	}
	return string(b)
}