package chunk

import (
	"archive/tar"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"time"

	"git.cheetah.cat/worksucc/gma-puzzles/common"
	"github.com/klauspost/compress/zstd"
)

type PoolRecoveryData struct {
	PoolID  string    `json:"_key"`
	Size    uint64    `json:"size"`
	Created time.Time `json:"date"`
	Hash    string    `json:"hash"`

	ItemCount    int              `json:"itemCount"`
	Items        []string         `json:"items"`
	RecoveryData []common.DB_File `json:"recoveryData"`
}

type ChunkReader struct {
	FileHandle   *os.File
	ExpectedHash *string
	ExpectedSize *uint64
}

func NewChunkReader(fileName string) (_ ChunkReader, err error) {
	return ChunkReader{}.NewReader(fileName)
}
func (r ChunkReader) NewReader(fileName string) (_ ChunkReader, err error) {
	r.FileHandle, err = os.Open(fileName)
	if err != nil {
		return r, err
	}

	return r, nil
}
func (r ChunkReader) NewReaderFrom(fileHandle *os.File) (_ ChunkReader, err error) {
	r.FileHandle = fileHandle
	return r, nil
}
func (r *ChunkReader) LoadRecoveryFile(fileName string) (err error) {
	var poolRecoveryData PoolRecoveryData

	readJSONFile, err := os.Open(fileName)
	if err != nil {
		return err
	}
	defer readJSONFile.Close()

	readBytes, err := io.ReadAll(readJSONFile)
	if err != nil {
		return err
	}
	err = json.Unmarshal(readBytes, &poolRecoveryData)
	if err != nil {
		return err
	}

	r.ExpectedHash = &poolRecoveryData.Hash
	r.ExpectedSize = &poolRecoveryData.Size
	return nil
}

func (r *ChunkReader) CheckIntegrity() (err error) {
	// re-open and check
	r.FileHandle.Seek(0, 0)
	shaHasher := sha256.New()
	hashedBytes, err := io.Copy(shaHasher, r.FileHandle)
	if err != nil {
		return err
	}
	readHash := fmt.Sprintf("%x", shaHasher.Sum(nil))
	//fmt.Printf("PackPoolTar hash is %s\n", readHash)
	if readHash != *r.ExpectedHash {
		return fmt.Errorf("WORM Hash %s != Hash %s", readHash, *r.ExpectedHash)
	}
	packFileStats, err := r.FileHandle.Stat()
	if err != nil {
		return err
	}
	readSize := packFileStats.Size()
	if readSize != int64(*r.ExpectedSize) {
		return fmt.Errorf("WORM Copy FileSize %d != FileSize %d", readSize, *r.ExpectedSize)
	}
	// validate written tar-chunk
	_, err = r.FileHandle.Seek(0, 0)
	if err != nil {
		return err
	}

	decompressor, err := zstd.NewReader(r.FileHandle, zstd.WithDecoderConcurrency(8))
	if err != nil {
		return err
	}
	defer decompressor.Close()
	tarFileCheckReader := tar.NewReader(decompressor)

	//filenamesReadBackList := []string{}
	for {
		header, err := tarFileCheckReader.Next()
		//header.PAXRecords
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		hasher := sha256.New()
		hashedBytes, err := io.Copy(hasher, tarFileCheckReader)
		if err != nil {
			return err
		}
		readBackChecksum := fmt.Sprintf("%x", hasher.Sum(nil))
		if hashedBytes != header.Size {
			return fmt.Errorf("validation on output archive, incorrect size file %s has %d should be %d", header.Name, hashedBytes, header.Size)
		}
		if header.Name != readBackChecksum {
			return fmt.Errorf("validation on output archive, incorrect checksum file %s has %s", header.Name, readBackChecksum)
		}
		//filenamesReadBackList = append(filenamesReadBackList, header.Name)
	}

	if hashedBytes != int64(*r.ExpectedSize) {
		return fmt.Errorf("WORM Copy HashedBytes %d != FileSize %d", hashedBytes, *r.ExpectedSize)
	}
	return nil
}

func (r *ChunkReader) Close() {
	r.FileHandle.Close()
}