package pipelinedb

import (
	"sync"
	"testing"
	"time"
)

// TestNewPageCache 测试页面缓存的创建
func TestNewPageCache(t *testing.T) {
	tests := []struct {
		name     string
		capacity int
		wantSize int
	}{
		{
			name:     "创建小容量缓存",
			capacity: 10,
			wantSize: 0,
		},
		{
			name:     "创建中等容量缓存",
			capacity: 100,
			wantSize: 0,
		},
		{
			name:     "创建大容量缓存",
			capacity: 1000,
			wantSize: 0,
		},
		{
			name:     "创建零容量缓存",
			capacity: 0,
			wantSize: 0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			cache := NewPageCache(tt.capacity)

			if cache == nil {
				t.Fatal("NewPageCache returned nil")
			}

			if cache.capacity != tt.capacity {
				t.Errorf("capacity = %d, want %d", cache.capacity, tt.capacity)
			}

			if cache.Size() != tt.wantSize {
				t.Errorf("initial size = %d, want %d", cache.Size(), tt.wantSize)
			}

			// 验证统计信息初始状态
			hits, misses, hitRate := cache.Stats()
			if hits != 0 || misses != 0 || hitRate != 0.0 {
				t.Errorf("initial stats: hits=%d, misses=%d, hitRate=%f, want all zero", hits, misses, hitRate)
			}
		})
	}
}

// TestPageCachePutGet 测试基本的Put和Get操作
func TestPageCachePutGet(t *testing.T) {
	cache := NewPageCache(10)

	// 测试数据
	testData := []byte("test page data")
	pageNo := uint16(1)

	// 测试Put操作
	cache.Put(pageNo, testData, false)

	// 验证缓存大小
	if cache.Size() != 1 {
		t.Errorf("size after put = %d, want 1", cache.Size())
	}

	// 测试Get操作
	data, found := cache.Get(pageNo)
	if !found {
		t.Fatal("Get returned false, want true")
	}

	if string(data) != string(testData) {
		t.Errorf("Get returned %s, want %s", string(data), string(testData))
	}

	// 验证统计信息
	hits, misses, hitRate := cache.Stats()
	if hits != 1 || misses != 0 {
		t.Errorf("stats after get: hits=%d, misses=%d, want hits=1, misses=0", hits, misses)
	}
	if hitRate != 1.0 {
		t.Errorf("hit rate = %f, want 1.0", hitRate)
	}
}

// TestPageCacheGetMiss 测试缓存未命中的情况
func TestPageCacheGetMiss(t *testing.T) {
	cache := NewPageCache(10)

	// 尝试获取不存在的页面
	data, found := cache.Get(999)
	if found {
		t.Error("Get returned true for non-existent page, want false")
	}
	if data != nil {
		t.Error("Get returned non-nil data for non-existent page, want nil")
	}

	// 验证统计信息
	hits, misses, hitRate := cache.Stats()
	if hits != 0 || misses != 1 {
		t.Errorf("stats after miss: hits=%d, misses=%d, want hits=0, misses=1", hits, misses)
	}
	if hitRate != 0.0 {
		t.Errorf("hit rate = %f, want 0.0", hitRate)
	}
}

// TestPageCacheLRUEviction 测试LRU淘汰机制
func TestPageCacheLRUEviction(t *testing.T) {
	cache := NewPageCache(3) // 小容量缓存便于测试淘汰

	// 添加3个页面，填满缓存
	for i := uint16(1); i <= 3; i++ {
		data := []byte("page " + string(rune('0'+i)))
		cache.Put(i, data, false)
	}

	// 验证缓存已满
	if cache.Size() != 3 {
		t.Errorf("size after filling cache = %d, want 3", cache.Size())
	}

	// 访问页面1，使其成为最近使用的
	cache.Get(1)

	// 添加第4个页面，应该淘汰页面2（最久未使用）
	cache.Put(4, []byte("page 4"), false)

	// 验证缓存大小仍为3
	if cache.Size() != 3 {
		t.Errorf("size after eviction = %d, want 3", cache.Size())
	}

	// 验证页面1仍然存在（最近访问过）
	_, found := cache.Get(1)
	if !found {
		t.Error("page 1 was evicted, but it should be kept (recently accessed)")
	}

	// 验证页面2被淘汰
	_, found = cache.Get(2)
	if found {
		t.Error("page 2 should be evicted")
	}

	// 验证页面3和4仍然存在
	_, found = cache.Get(3)
	if !found {
		t.Error("page 3 should still exist")
	}

	_, found = cache.Get(4)
	if !found {
		t.Error("page 4 should exist (just added)")
	}
}

// TestPageCacheDirtyPages 测试脏页管理
func TestPageCacheDirtyPages(t *testing.T) {
	cache := NewPageCache(10)

	// 添加一个干净页面
	cache.Put(1, []byte("clean page"), false)

	// 添加一个脏页面
	cache.Put(2, []byte("dirty page"), true)

	// 更新页面1为脏页
	cache.Put(1, []byte("updated page"), true)

	// 验证缓存大小
	if cache.Size() != 2 {
		t.Errorf("size = %d, want 2", cache.Size())
	}

	// 测试Flush操作
	flushedPages := make(map[uint16][]byte)
	flushFunc := func(pageNo uint16, data []byte) error {
		flushedPages[pageNo] = make([]byte, len(data))
		copy(flushedPages[pageNo], data)
		return nil
	}

	err := cache.Flush(flushFunc)
	if err != nil {
		t.Errorf("Flush returned error: %v", err)
	}

	// 验证脏页被刷新
	if len(flushedPages) != 2 {
		t.Errorf("flushed %d pages, want 2", len(flushedPages))
	}

	if string(flushedPages[1]) != "updated page" {
		t.Errorf("flushed page 1 = %s, want 'updated page'", string(flushedPages[1]))
	}

	if string(flushedPages[2]) != "dirty page" {
		t.Errorf("flushed page 2 = %s, want 'dirty page'", string(flushedPages[2]))
	}
}

// TestPageCacheInvalidate 测试页面失效操作
func TestPageCacheInvalidate(t *testing.T) {
	cache := NewPageCache(10)

	// 添加几个页面
	cache.Put(1, []byte("page 1"), false)
	cache.Put(2, []byte("page 2"), true)
	cache.Put(3, []byte("page 3"), false)

	// 验证初始状态
	if cache.Size() != 3 {
		t.Errorf("initial size = %d, want 3", cache.Size())
	}

	// 使页面2失效
	cache.Invalidate(2)

	// 验证页面2被移除
	if cache.Size() != 2 {
		t.Errorf("size after invalidate = %d, want 2", cache.Size())
	}

	_, found := cache.Get(2)
	if found {
		t.Error("invalidated page 2 should not be found")
	}

	// 验证其他页面仍然存在
	_, found = cache.Get(1)
	if !found {
		t.Error("page 1 should still exist")
	}

	_, found = cache.Get(3)
	if !found {
		t.Error("page 3 should still exist")
	}

	// 测试失效不存在的页面（应该是幂等操作）
	cache.Invalidate(999)
	if cache.Size() != 2 {
		t.Errorf("size after invalidating non-existent page = %d, want 2", cache.Size())
	}
}

// TestPageCacheClear 测试清空缓存操作
func TestPageCacheClear(t *testing.T) {
	cache := NewPageCache(10)

	// 添加一些页面
	for i := uint16(1); i <= 5; i++ {
		cache.Put(i, []byte("page"), false)
	}

	// 产生一些统计数据
	cache.Get(1)
	cache.Get(999) // miss

	// 验证初始状态
	if cache.Size() != 5 {
		t.Errorf("initial size = %d, want 5", cache.Size())
	}

	hits, misses, _ := cache.Stats()
	if hits == 0 && misses == 0 {
		t.Error("should have some stats before clear")
	}

	// 清空缓存
	cache.Clear()

	// 验证缓存被清空
	if cache.Size() != 0 {
		t.Errorf("size after clear = %d, want 0", cache.Size())
	}

	// 验证统计信息被重置
	hits, misses, hitRate := cache.Stats()
	if hits != 0 || misses != 0 || hitRate != 0.0 {
		t.Errorf("stats after clear: hits=%d, misses=%d, hitRate=%f, want all zero", hits, misses, hitRate)
	}

	// 验证页面不再存在
	_, found := cache.Get(1)
	if found {
		t.Error("page should not exist after clear")
	}
}

// TestPageCacheDataIsolation 测试数据隔离（副本机制）
func TestPageCacheDataIsolation(t *testing.T) {
	cache := NewPageCache(10)

	// 原始数据
	originalData := []byte("original data")
	pageNo := uint16(1)

	// 存储数据
	cache.Put(pageNo, originalData, false)

	// 修改原始数据
	originalData[0] = 'X'

	// 获取缓存数据
	cachedData, found := cache.Get(pageNo)
	if !found {
		t.Fatal("page not found in cache")
	}

	// 验证缓存数据未被修改
	if cachedData[0] == 'X' {
		t.Error("cached data was modified when original data changed")
	}

	if string(cachedData) != "original data" {
		t.Errorf("cached data = %s, want 'original data'", string(cachedData))
	}

	// 修改获取到的数据
	cachedData[0] = 'Y'

	// 再次获取，验证缓存中的数据未被修改
	cachedData2, found := cache.Get(pageNo)
	if !found {
		t.Fatal("page not found in cache")
	}

	if cachedData2[0] == 'Y' {
		t.Error("cached data was modified when returned data changed")
	}

	if string(cachedData2) != "original data" {
		t.Errorf("cached data = %s, want 'original data'", string(cachedData2))
	}
}

// TestPageCacheConcurrency 测试并发安全性
func TestPageCacheConcurrency(t *testing.T) {
	cache := NewPageCache(100)

	const numGoroutines = 10
	const numOperations = 100

	var wg sync.WaitGroup

	// 启动多个goroutine进行并发操作
	for i := 0; i < numGoroutines; i++ {
		wg.Add(1)
		go func(id int) {
			defer wg.Done()

			for j := 0; j < numOperations; j++ {
				pageNo := uint16(id*numOperations + j)
				data := []byte("data from goroutine " + string(rune('0'+id)))

				// 并发Put操作
				cache.Put(pageNo, data, j%2 == 0) // 一半是脏页

				// 并发Get操作
				cache.Get(pageNo)

				// 偶尔进行Invalidate操作
				if j%10 == 0 {
					cache.Invalidate(pageNo)
				}
			}
		}(i)
	}

	// 同时进行统计查询
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 50; i++ {
			cache.Stats()
			cache.Size()
			time.Sleep(time.Millisecond)
		}
	}()

	// 等待所有goroutine完成
	wg.Wait()

	// 验证缓存仍然可用
	cache.Put(9999, []byte("final test"), false)
	data, found := cache.Get(9999)
	if !found || string(data) != "final test" {
		t.Error("cache corrupted after concurrent operations")
	}
}

// TestPageCacheStatsAccuracy 测试统计信息的准确性
func TestPageCacheStatsAccuracy(t *testing.T) {
	cache := NewPageCache(10)

	// 执行一系列操作
	cache.Put(1, []byte("page 1"), false)
	cache.Put(2, []byte("page 2"), false)

	// 2次命中
	cache.Get(1)
	cache.Get(2)

	// 3次未命中
	cache.Get(3)
	cache.Get(4)
	cache.Get(5)

	// 1次命中
	cache.Get(1)

	// 验证统计信息
	hits, misses, hitRate := cache.Stats()

	expectedHits := int64(3)
	expectedMisses := int64(3)
	expectedHitRate := float64(3) / float64(6)

	if hits != expectedHits {
		t.Errorf("hits = %d, want %d", hits, expectedHits)
	}

	if misses != expectedMisses {
		t.Errorf("misses = %d, want %d", misses, expectedMisses)
	}

	if hitRate != expectedHitRate {
		t.Errorf("hit rate = %f, want %f", hitRate, expectedHitRate)
	}
}

// TestPageCacheUpdateExisting 测试更新已存在页面
func TestPageCacheUpdateExisting(t *testing.T) {
	cache := NewPageCache(10)

	pageNo := uint16(1)

	// 添加初始页面
	cache.Put(pageNo, []byte("original"), false)

	// 验证初始数据
	data, found := cache.Get(pageNo)
	if !found || string(data) != "original" {
		t.Errorf("initial data = %s, want 'original'", string(data))
	}

	// 更新页面数据
	cache.Put(pageNo, []byte("updated"), true)

	// 验证缓存大小没有增加
	if cache.Size() != 1 {
		t.Errorf("size after update = %d, want 1", cache.Size())
	}

	// 验证数据已更新
	data, found = cache.Get(pageNo)
	if !found || string(data) != "updated" {
		t.Errorf("updated data = %s, want 'updated'", string(data))
	}

	// 验证脏页标记
	flushedCount := 0
	flushFunc := func(pageNo uint16, data []byte) error {
		flushedCount++
		return nil
	}

	cache.Flush(flushFunc)
	if flushedCount != 1 {
		t.Errorf("flushed %d pages, want 1 (dirty page)", flushedCount)
	}
}

// BenchmarkPageCacheGet 性能测试：Get操作
func BenchmarkPageCacheGet(b *testing.B) {
	cache := NewPageCache(1000)

	// 预填充缓存
	for i := uint16(0); i < 1000; i++ {
		cache.Put(i, []byte("benchmark data"), false)
	}

	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		cache.Get(uint16(i % 1000))
	}
}

// BenchmarkPageCachePut 性能测试：Put操作
func BenchmarkPageCachePut(b *testing.B) {
	cache := NewPageCache(1000)
	data := []byte("benchmark data")

	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		cache.Put(uint16(i%1000), data, false)
	}
}

// BenchmarkPageCacheConcurrentAccess 性能测试：并发访问
func BenchmarkPageCacheConcurrentAccess(b *testing.B) {
	cache := NewPageCache(1000)
	data := []byte("benchmark data")

	// 预填充缓存
	for i := uint16(0); i < 1000; i++ {
		cache.Put(i, data, false)
	}

	b.ResetTimer()

	b.RunParallel(func(pb *testing.PB) {
		i := 0
		for pb.Next() {
			if i%2 == 0 {
				cache.Get(uint16(i % 1000))
			} else {
				cache.Put(uint16(i%1000), data, false)
			}
			i++
		}
	})
}