package util

import (
	"encoding/hex"
	"hash/crc32"
	"io"
	"os"
	"path/filepath"
	"strings"
)

type CRC32Result struct {
	value uint32
	err   error
}

func (c *CRC32Result) Value() uint32 {
	if c.err != nil {
		return 0
	}
	return c.value
}

func (c *CRC32Result) Array() [4]byte {
	if c.err != nil {
		return [4]byte{}
	}
	return UInt32ToBytesArray(c.value)
}

func (c *CRC32Result) Slice() []byte {
	if c.err != nil {
		return []byte{}
	}
	return UInt32ToBytesSlice(c.value)
}

func (c *CRC32Result) Upper() string {
	if c.err != nil {
		return ""
	}
	return strings.ToUpper(hex.EncodeToString(c.Slice()))
}

func (c *CRC32Result) Lower() string {
	if c.err != nil {
		return ""
	}
	return strings.ToLower(hex.EncodeToString(c.Slice()))
}

func (c *CRC32Result) Error() error {
	return c.err
}

func NewCRC32Result(result uint32, err error) *CRC32Result {
	return &CRC32Result{
		value: result,
		err:   err,
	}
}

type CRC32 struct{}

func NewCRC32() *CRC32 {
	return &CRC32{}
}

func (c *CRC32) FromReader(r io.Reader) *CRC32Result {
	return c.FromReaderChunk(r, 1024*8)
}

func (c *CRC32) FromFile(filename string) *CRC32Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewCRC32Result(0, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return c.FromReader(file)
}

func (c *CRC32) FromReaderChunk(r io.Reader, chunksize int) *CRC32Result {
	val := uint32(0)
	buf := make([]byte, chunksize)
	var n int
	var err error
	for {
		n, err = r.Read(buf)
		if err != nil {
			if err != io.EOF {
				return NewCRC32Result(0, err)
			}
			if n > 0 {
				val = crc32.Update(val, crc32.IEEETable, buf[:n])
			}
			break
		}
		val = crc32.Update(val, crc32.IEEETable, buf[:n])
	}
	return NewCRC32Result(val, nil)
}

func (c *CRC32) FromFileChunk(filename string, chunksize int) *CRC32Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewCRC32Result(0, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return c.FromReaderChunk(file, chunksize)
}

func (c *CRC32) FromBytes(data []byte) *CRC32Result {
	return NewCRC32Result(crc32.ChecksumIEEE(data), nil)
}

func (c *CRC32) FromString(data string) *CRC32Result {
	return NewCRC32Result(crc32.ChecksumIEEE([]byte(data)), nil)
}

type CRC32Pip struct {
	crc uint32
}

func NewCRC32Pip() *CRC32Pip {
	return &CRC32Pip{crc: 0}
}

func (c *CRC32Pip) Write(data []byte) (n int, err error) {
	c.crc = crc32.Update(c.crc, crc32.IEEETable, data)
	return len(data), nil
}

func (c *CRC32Pip) WriteBytes(data []byte) {
	c.crc = crc32.Update(c.crc, crc32.IEEETable, data)
}

func (c *CRC32Pip) WriteString(data string) {
	c.crc = crc32.Update(c.crc, crc32.IEEETable, []byte(data))
}

func (c *CRC32Pip) Result() *CRC32Result {
	return NewCRC32Result(c.crc, nil)
}