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

package mmap

import (
	"io"
	"os"
)

type SharedMMAP struct {
	filename  string
	stat      os.FileInfo
	rawReader *ReaderAt
	countRefs int32
	mod       uint64
}

func NewSharedMMAP(filename string, stat os.FileInfo, reader *ReaderAt, mod uint64) *SharedMMAP {
	return &SharedMMAP{
		filename:  filename,
		stat:      stat,
		rawReader: reader,
		countRefs: 1,
		mod:       mod,
	}
}

func (this *SharedMMAP) ReadAt(p []byte, off int64) (n int, err error) {
	n, err = this.rawReader.ReadAt(p, off)
	return
}

func (this *SharedMMAP) Size() int64 {
	return this.stat.Size()
}

func (this *SharedMMAP) Stat() os.FileInfo {
	return this.stat
}

func (this *SharedMMAP) Name() string {
	return this.filename
}

// AddRef increase one reference
func (this *SharedMMAP) AddRef() (ok bool) {
	mmapMapMu[this.mod].Lock()
	if this.countRefs > 0 { // not closing
		this.countRefs++
		ok = true
	}
	mmapMapMu[this.mod].Unlock()

	return
}

func (this *SharedMMAP) Write(writer io.Writer, offset int) (int, error) {
	return this.rawReader.Write(writer, offset)
}

// Close release one reference
// 单个引用 必须 只能close一次，防止提前close
func (this *SharedMMAP) Close() error {
	if !enableShareMode {
		return this.rawReader.Close()
	}

	mmapMapMu[this.mod].Lock()

	this.countRefs--
	var shouldClose = this.countRefs == 0

	if shouldClose {
		var mmapMap = mmapMaps[this.mod]
		delete(mmapMap[this.filename], this)
		if len(mmapMap[this.filename]) == 0 {
			delete(mmapMap, this.filename)
		}
	}

	mmapMapMu[this.mod].Unlock()

	if shouldClose {
		return this.rawReader.Close()
	}

	return nil
}