// Copyright 2024 GoEdge CDN goedge.cdn@gmail.com. All rights reserved. Official site: https://goedge.cn .
//go:build plus

package mmap

import (
	"github.com/TeaOSLab/EdgeNode/internal/utils/fnv"
	fsutils "github.com/TeaOSLab/EdgeNode/internal/utils/fs"
	"github.com/TeaOSLab/EdgeNode/internal/utils/zero"
	"sync"
)

// TODO 当缓存文件更新时在mmap map中删除对应mmap，以便于及时更新？修改inotify相关代码？

const mmapMuShards = 32
const enableShareMode = false // 暂时不启用，需要更多时间的测试

var mmapMaps = [mmapMuShards]map[string]map[*SharedMMAP]zero.Zero{} //  [{ filename => { mmap => Zero } }, ...]
var mmapMapMu = [mmapMuShards]*sync.RWMutex{}

func init() {
	for i := 0; i < mmapMuShards; i++ {
		mmapMaps[i] = map[string]map[*SharedMMAP]zero.Zero{}
		mmapMapMu[i] = &sync.RWMutex{}
	}
}

func OpenSharedMMAP(filename string) (*SharedMMAP, error) {
	var mod = fnv.HashString(filename) % mmapMuShards
	var mu = mmapMapMu[mod]
	var m *SharedMMAP
	var mmapMap map[string]map[*SharedMMAP]zero.Zero

	if enableShareMode {
		mu.RLock()
		mmapMap = mmapMaps[mod]
		bucket, ok := mmapMap[filename]
		if ok && len(bucket) > 0 {
			for firstM := range bucket {
				m = firstM
				break
			}
		}
		mu.RUnlock()
		if m != nil && m.AddRef() {
			return m, nil
		}
	}

	fp, err := fsutils.Open(filename)
	if err != nil {
		return nil, err
	}

	stat, err := fp.Stat()
	if err != nil {
		_ = fp.Close()
		return nil, err
	}

	reader, err := OpenFile(fp, stat.Size())
	if err != nil {
		return nil, err
	}

	m = NewSharedMMAP(filename, stat, reader, mod)

	if enableShareMode {
		mu.Lock()
		if mmapMap[filename] == nil {
			mmapMap[filename] = map[*SharedMMAP]zero.Zero{
				m: {},
			}
		} else {
			mmapMap[filename][m] = zero.Zero{}
		}
		mu.Unlock()
	}

	return m, nil
}

func CountSharedMMAP() int {
	var count int
	for i := 0; i < mmapMuShards; i++ {
		mmapMapMu[i].RLock()
		for _, bucket := range mmapMaps[i] {
			count += len(bucket)
		}
		mmapMapMu[i].RUnlock()
	}
	return count
}