// Copyright 2022 Liuxiangchao iwind.liu@gmail.com. All rights reserved.

package caches

import (
	"encoding/binary"
	fsutils "github.com/TeaOSLab/EdgeNode/internal/utils/fs"
	"github.com/iwind/TeaGo/types"
	"io"
	"os"
	"sync"
)

type PartialFileWriter struct {
	rawWriter *os.File
	key       string

	metaHeaderSize int
	headerSize     int64

	metaBodySize int64
	bodySize     int64

	expiredAt int64
	endFunc   func()
	once      sync.Once

	isNew      bool
	isPartial  bool
	bodyOffset int64

	ranges    *PartialRanges
	rangePath string
}

func NewPartialFileWriter(rawWriter *os.File, key string, expiredAt int64, metaHeaderSize int, metaBodySize int64, isNew bool, isPartial bool, bodyOffset int64, ranges *PartialRanges, endFunc func()) *PartialFileWriter {
	return &PartialFileWriter{
		key:            key,
		rawWriter:      rawWriter,
		expiredAt:      expiredAt,
		endFunc:        endFunc,
		isNew:          isNew,
		isPartial:      isPartial,
		bodyOffset:     bodyOffset,
		ranges:         ranges,
		rangePath:      PartialRangesFilePath(rawWriter.Name()),
		metaHeaderSize: metaHeaderSize,
		metaBodySize:   metaBodySize,
	}
}

// WriteHeader 写入数据
func (this *PartialFileWriter) WriteHeader(data []byte) (n int, err error) {
	if !this.isNew {
		return
	}
	fsutils.WriteBegin()
	n, err = this.rawWriter.Write(data)
	fsutils.WriteEnd()
	this.headerSize += int64(n)
	if err != nil {
		_ = this.Discard()
	}
	return
}

func (this *PartialFileWriter) AppendHeader(data []byte) error {
	fsutils.WriteBegin()
	_, err := this.rawWriter.Write(data)
	fsutils.WriteEnd()
	if err != nil {
		_ = this.Discard()
	} else {
		var c = len(data)
		this.headerSize += int64(c)
		err = this.WriteHeaderLength(int(this.headerSize))
		if err != nil {
			_ = this.Discard()
		}
	}
	return err
}

// WriteHeaderLength 写入Header长度数据
func (this *PartialFileWriter) WriteHeaderLength(headerLength int) error {
	if this.metaHeaderSize > 0 && this.metaHeaderSize == headerLength {
		return nil
	}

	var bytes4 = make([]byte, 4)
	binary.BigEndian.PutUint32(bytes4, uint32(headerLength))
	_, err := this.rawWriter.Seek(SizeExpiresAt+SizeStatus+SizeURLLength, io.SeekStart)
	if err != nil {
		_ = this.Discard()
		return err
	}
	_, err = this.rawWriter.Write(bytes4)
	if err != nil {
		_ = this.Discard()
		return err
	}
	return nil
}

// Write 写入数据
func (this *PartialFileWriter) Write(data []byte) (n int, err error) {
	fsutils.WriteBegin()
	n, err = this.rawWriter.Write(data)
	fsutils.WriteEnd()
	this.bodySize += int64(n)
	if err != nil {
		_ = this.Discard()
	}
	return
}

// WriteAt 在指定位置写入数据
func (this *PartialFileWriter) WriteAt(offset int64, data []byte) error {
	var c = int64(len(data))
	if c == 0 {
		return nil
	}
	var end = offset + c - 1

	// 是否已包含在内
	if this.ranges.Contains(offset, end) {
		return nil
	}

	// prevent extending too much space in a single writing
	var maxOffset = this.ranges.Max()
	if offset-maxOffset > 16<<20 {
		var maxExtendSize int64 = 32 << 20
		if fsutils.DiskIsExtremelyFast() {
			maxExtendSize = 128 << 20
		} else if fsutils.DiskIsFast() {
			maxExtendSize = 64 << 20
		}
		if offset-maxOffset > maxExtendSize {
			stat, err := this.rawWriter.Stat()
			if err != nil {
				return nil
			}

			// extend min size to prepare for file tail
			const extendSizePerStep = 8 << 20
			if stat.Size()+extendSizePerStep <= this.bodyOffset+offset+int64(len(data)) {
				fsutils.WriteBegin()
				_ = this.rawWriter.Truncate(stat.Size() + extendSizePerStep)
				fsutils.WriteEnd()
				return nil
			}
		}
	}

	if this.bodyOffset == 0 {
		var keyLength = 0
		if this.ranges.Version == 0 { // 以往的版本包含有Key
			keyLength = len(this.key)
		}
		this.bodyOffset = SizeMeta + int64(keyLength) + this.headerSize
	}

	fsutils.WriteBegin()
	_, err := this.rawWriter.WriteAt(data, this.bodyOffset+offset)
	fsutils.WriteEnd()
	if err != nil {
		return err
	}

	this.ranges.Add(offset, end)

	return nil
}

// SetBodyLength 设置内容总长度
func (this *PartialFileWriter) SetBodyLength(bodyLength int64) {
	this.bodySize = bodyLength
}

// WriteBodyLength 写入Body长度数据
func (this *PartialFileWriter) WriteBodyLength(bodyLength int64) error {
	if this.metaBodySize > 0 && this.metaBodySize == bodyLength {
		return nil
	}
	var bytes8 = make([]byte, 8)
	binary.BigEndian.PutUint64(bytes8, uint64(bodyLength))
	_, err := this.rawWriter.Seek(SizeExpiresAt+SizeStatus+SizeURLLength+SizeHeaderLength, io.SeekStart)
	if err != nil {
		_ = this.Discard()
		return err
	}
	_, err = this.rawWriter.Write(bytes8)
	if err != nil {
		_ = this.Discard()
		return err
	}
	return nil
}

// Close 关闭
func (this *PartialFileWriter) Close() error {
	defer this.once.Do(func() {
		this.endFunc()
	})

	this.ranges.BodySize = this.bodySize
	err := this.ranges.WriteToFile(this.rangePath)
	if err != nil {
		fsutils.WriteBegin()
		_ = this.rawWriter.Close()
		fsutils.WriteEnd()
		this.remove()
		return err
	}

	// 关闭当前writer
	if this.isNew {
		err = this.WriteHeaderLength(types.Int(this.headerSize))
		if err != nil {
			fsutils.WriteBegin()
			_ = this.rawWriter.Close()
			fsutils.WriteEnd()
			this.remove()
			return err
		}
		err = this.WriteBodyLength(this.bodySize)
		if err != nil {
			fsutils.WriteBegin()
			_ = this.rawWriter.Close()
			fsutils.WriteEnd()
			this.remove()
			return err
		}
	}

	fsutils.WriteBegin()
	err = this.rawWriter.Close()
	fsutils.WriteEnd()
	if err != nil {
		this.remove()
	}

	return err
}

// Discard 丢弃
func (this *PartialFileWriter) Discard() error {
	defer this.once.Do(func() {
		this.endFunc()
	})

	fsutils.WriteBegin()
	_ = this.rawWriter.Close()
	fsutils.WriteEnd()

	SharedPartialRangesQueue.Delete(this.rangePath)
	_ = os.Remove(this.rangePath)

	err := os.Remove(this.rawWriter.Name())
	return err
}

func (this *PartialFileWriter) HeaderSize() int64 {
	return this.headerSize
}

func (this *PartialFileWriter) BodySize() int64 {
	return this.bodySize
}

func (this *PartialFileWriter) ExpiredAt() int64 {
	return this.expiredAt
}

func (this *PartialFileWriter) Key() string {
	return this.key
}

// ItemType 获取内容类型
func (this *PartialFileWriter) ItemType() ItemType {
	return ItemTypeFile
}

func (this *PartialFileWriter) IsNew() bool {
	return this.isNew && len(this.ranges.Ranges) == 0
}

func (this *PartialFileWriter) remove() {
	_ = os.Remove(this.rawWriter.Name())

	SharedPartialRangesQueue.Delete(this.rangePath)
	_ = os.Remove(this.rangePath)
}