package wireproto

import (
	`bytes`
	`cmp`
	`fmt`
	`hash/crc32`
	`io`
	`strings`

	`r00t2.io/goutils/multierr`
)

// GenChecksum (re-)generates and returns the checksum. The body that is checksummed is returned in buf.
func (r *Response) GenChecksum() (cksum uint32, buf *bytes.Buffer, err error) {

	var b []byte
	var size int

	buf = new(bytes.Buffer)

	_ = r.Size()

	for _, p := range r.RecordGroups {
		size += p.Size()
	}

	if _, err = buf.Write(hdrBODYSTART); err != nil {
		return
	}

	if _, err = buf.Write(PackInt(len(r.RecordGroups))); err != nil {
		return
	}
	if _, err = buf.Write(PackInt(size)); err != nil {
		return
	}

	for _, rg := range r.RecordGroups {
		if b, err = rg.MarshalBinary(); err != nil {
			return
		}
		if _, err = buf.Write(b); err != nil {
			return
		}
	}

	if _, err = buf.Write(hdrBODYEND); err != nil {
		return
	}

	cksum = crc32.ChecksumIEEE(buf.Bytes())

	r.Checksum = cksum

	return
}

// RespStat trawls the KVP for a field name with "error" and updates the status to reflect an error was found.
func (r *Response) RespStat() {

	r.Status = RespStatusByteOK

	for _, rg := range r.RecordGroups {
		for _, rec := range rg.Records {
			for _, kvp := range rec.Pairs {
				if strings.ToLower(kvp.Name.String()) == "error" {
					r.Status = RespStatusByteErr
					return
				}
			}
		}
	}

}

// MarshalBinary renders a Response into a byte-packed format.
func (r *Response) MarshalBinary() (data []byte, err error) {

	var b []byte
	var msgSize int
	var hasErr bool
	var mErr *multierr.MultiError = multierr.NewMultiError(nil)
	var buf *bytes.Buffer = new(bytes.Buffer)
	var msgBuf *bytes.Buffer = new(bytes.Buffer)

	_ = r.Size()

	for _, i := range r.RecordGroups {
		msgSize += i.Size()
	}

	// The message "body" - this is done first so it can be checksummed.
	if _, err = msgBuf.Write(hdrBODYSTART); err != nil {
		return
	}
	// Record group count
	if _, err = msgBuf.Write(PackInt(len(r.RecordGroups))); err != nil {
		return
	}
	// And size.
	if _, err = msgBuf.Write(PackInt(msgSize)); err != nil {
		return
	}
	for _, i := range r.RecordGroups {
		if b, err = i.MarshalBinary(); err != nil {
			mErr.AddError(err)
			err = nil
			hasErr = true
		}
		if _, err = msgBuf.Write(b); err != nil {
			mErr.AddError(err)
			err = nil
			hasErr = true
		}
	}
	if _, err = msgBuf.Write(hdrBODYEND); err != nil {
		mErr.AddError(err)
		err = nil
		hasErr = true
	}

	// Now write the response as a whole.

	// Status
	if r.Status == RespStatusByteOK && hasErr {
		r.Status = RespStatusByteErr
	}
	if _, err = buf.Write([]byte{r.Status}); err != nil {
		return
	}

	// Checksum; ALWAYS present for responses!
	if _, _, err = r.GenChecksum(); err != nil {
		return
	}
	if _, err = buf.Write(hdrCKSUM); err != nil {
		return
	}
	if _, err = buf.Write(cksumBytes(r.Checksum)); err != nil {
		return
	}

	// Message start
	if _, err = buf.Write(hdrMSGSTART); err != nil {
		return
	}

	// Protocol version
	if _, err = buf.Write(PackUint32(r.ProtocolVersion)); err != nil {
		return
	}

	// Then copy the msgBuf in.
	if _, err = msgBuf.WriteTo(buf); err != nil {
		return
	}
	// And then the message end.
	if _, err = buf.Write(hdrMSGEND); err != nil {
		return
	}

	data = buf.Bytes()

	if !mErr.IsEmpty() {
		err = mErr
		return
	}

	return
}

// Model returns an indented string representation of the model.
func (r *Response) Model() (out string) {

	out = r.ModelCustom(IndentChars, SeparatorChars, indentR)

	return
}

// ModelCustom is like Model with user-defined formatting.
func (r *Response) ModelCustom(indent, sep string, level uint) (out string) {

	var maxFtr int
	var size int
	var sb strings.Builder

	for _, rg := range r.RecordGroups {
		size += rg.Size()
	}

	_, _, _ = r.GenChecksum()

	// HDR: RESPSTART/RESPERR (RESPSTATUS)
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight([]byte{byte(r.Status)}, 8))
	sb.WriteString(sep)
	switch r.Status {
	case RespStatusByteOK:
		sb.WriteString("// HDR:RESPSTART      (Status: OK)\n")
	case RespStatusByteErr:
		sb.WriteString("// HDR:RESPERR        (Status: Error)\n")
	}

	// HDR: CKSUM
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(hdrCKSUM, 8))
	sb.WriteString(sep)
	sb.WriteString("// HDR:CKSUM\n")
	// Checksum
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(cksumBytes(r.Checksum), 8))
	sb.WriteString(sep)
	sb.WriteString(fmt.Sprintf("// Checksum Value     (%d)\n", r.Checksum))

	// Header: MSGSTART
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(hdrMSGSTART, 8))
	sb.WriteString(sep)
	sb.WriteString("// HDR:MSGSTART\n")

	// Protocol Version
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padIntRight(int(r.ProtocolVersion), 8))
	sb.WriteString(sep)
	sb.WriteString(fmt.Sprintf("// Protocol Version   (%d)\n", r.ProtocolVersion))

	// Header: BODYSTART
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(hdrBODYSTART, 8))
	sb.WriteString(sep)
	sb.WriteString("// HDR:BODYSTART\n")

	// Count
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padIntRight(len(r.RecordGroups), 8))
	sb.WriteString(sep)
	sb.WriteString(fmt.Sprintf("// Record Group Count (%d)\n", len(r.RecordGroups)))
	// Size
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padIntRight(size, 8))
	sb.WriteString(sep)
	sb.WriteString(fmt.Sprintf("// Record Groups Size (%d)\n", size))

	// VALUES
	for idx, rg := range r.RecordGroups {
		sb.WriteString(fmt.Sprintf("// Record Group %d (%d)\n", idx+1, rg.Size()))
		sb.WriteString(rg.ModelCustom(indent, sep, level+1))
	}

	// Make the footers a little more nicely aligned.
	switch cmp.Compare(len(hdrBODYEND), len(hdrMSGEND)) {
	case -1:
		maxFtr = len(hdrMSGEND)
	case 1, 0:
		maxFtr = len(hdrBODYEND)
	}

	// Footer: BODYEND
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(hdrBODYEND, maxFtr))
	sb.WriteString(sep)
	sb.WriteString("// HDR:BODYEND\n")

	// Footer: MSGEND
	sb.WriteString(strings.Repeat(indent, int(level)))
	sb.WriteString(padBytesRight(hdrMSGEND, maxFtr))
	sb.WriteString(sep)
	sb.WriteString("// HDR:MSGEND\n")

	out = sb.String()

	return
}

// Resolve associates children with parents.
func (r *Response) Resolve() {
	for idx, i := range r.RecordGroups {
		i.parent = r
		i.rgIdx = idx
		i.Resolve()
	}
}

// Size returns the Response's calculated size (in bytes) and updates the size field if 0.
func (r *Response) Size() (size int) {

	if r == nil {
		return
	}

	// Response Status
	size += 1

	// Checksum
	size += len(hdrCKSUM)
	size += CksumPackedSize

	// Message header
	size += len(hdrMSGSTART)

	// Protocol version
	size += PackedNumSize

	// Count and Size uint32s
	size += PackedNumSize * 2

	// Message begin
	size += len(hdrBODYSTART)

	for _, p := range r.RecordGroups {
		size += p.Size()
	}

	// Message end
	size += len(hdrBODYEND)

	// And closing sequence.
	size += len(hdrMSGEND)

	if r.common == nil || r.size == 0 {
		r.common = new(common)
	}

	r.size = uint32(size)

	return
}

// ToMap returns a slice of slice of slice of FVP maps for this Message.
func (r *Response) ToMap() (m [][][]map[string]interface{}) {

	m = make([][][]map[string]interface{}, len(r.RecordGroups))
	for idx, rg := range r.RecordGroups {
		m[idx] = rg.ToMap()
	}

	return
}

// UnmarshalBinary populates a Response from packed bytes.
func (r *Response) UnmarshalBinary(data []byte) (err error) {

	if data == nil || len(data) == 0 {
		return
	}

	var b []byte
	var rgCnt, bodySize int
	var rgSize int
	var rgBuf *bytes.Buffer
	var buf *bytes.Reader = bytes.NewReader(data)
	var msgBuf *bytes.Buffer = new(bytes.Buffer)

	if r == nil {
		*r = Response{}
	}
	r.common = new(common)
	r.size = 0

	// Get the status.
	if r.Status, err = buf.ReadByte(); err != nil {
		return
	}

	// And the checksum -- responses *always* have checksums per spec!
	// Toss the checksum header (after confirming).
	b = make([]byte, len(hdrCKSUM))
	if _, err = buf.Read(b); err != nil {
		return
	}
	if !bytes.Equal(b, hdrCKSUM) {
		err = ErrBadHdr
		return
	}
	// And get the checksum.
	b = make([]byte, CksumPackedSize)
	if _, err = buf.Read(b); err != nil {
		return
	}
	r.Checksum = UnpackUint32(b)

	// Read (and toss) the message start header.
	if _, err = buf.Read(make([]byte, len(hdrMSGSTART))); err != nil {
		return
	}

	// Get the protocol version.
	b = make([]byte, PackedNumSize)
	if _, err = buf.Read(b); err != nil {
		return
	}
	r.ProtocolVersion = UnpackUint32(b)

	// Skip over the BODYSTART (but write it to msgBuf).
	if _, err = io.CopyN(msgBuf, buf, int64(len(hdrBODYSTART))); err != nil {
		return
	}
	// Get the count of record groups
	b = make([]byte, PackedNumSize)
	if _, err = buf.Read(b); err != nil {
		return
	}
	rgCnt = UnpackInt(b)
	if _, err = msgBuf.Write(b); err != nil {
		return
	}
	// Get the size of record groups
	b = make([]byte, PackedNumSize)
	if _, err = buf.Read(b); err != nil {
		return
	}
	bodySize = UnpackInt(b)
	if _, err = msgBuf.Write(b); err != nil {
		return
	}

	// And the record groups themselves.
	if _, err = io.CopyN(msgBuf, buf, int64(bodySize+len(hdrBODYEND))); err != nil {
		return
	}

	// Now validate the checksum before continuing.
	if crc32.ChecksumIEEE(msgBuf.Bytes()) != r.Checksum {
		err = ErrBadCksum
		return
	}

	// Now that the checksum has validated, trim the msgBuf to only RGs.
	// Skip over the BODYSTART, record group count, and record group size.
	if _, err = msgBuf.Read(make([]byte, len(hdrBODYSTART)+(PackedNumSize*2))); err != nil {
		return
	}
	// Then truncate.
	msgBuf.Truncate(bodySize)

	r.RecordGroups = make([]*ResponseRecordGroup, rgCnt)

	for idx := 0; idx < rgCnt; idx++ {
		rgBuf = new(bytes.Buffer)

		// The RG unmarshaler handles the record count, but it needs to be in msgBuf to do that.
		if _, err = io.CopyN(rgBuf, msgBuf, int64(PackedNumSize)); err != nil {
			return
		}

		b = make([]byte, PackedNumSize)
		if _, err = msgBuf.Read(b); err != nil {
			return
		}
		if _, err = rgBuf.Write(b); err != nil {
			return
		}
		rgSize = UnpackInt(b)

		if _, err = io.CopyN(rgBuf, msgBuf, int64(rgSize)); err != nil {
			return
		}

		r.RecordGroups[idx] = new(ResponseRecordGroup)
		if err = r.RecordGroups[idx].UnmarshalBinary(rgBuf.Bytes()); err != nil {
			return
		}
	}

	_ = r.Size()

	return
}

// getIdx is a NOOP for Messages, but is used for Model conformance.
func (r *Response) getIdx() (idx int) {
	return
}

// getRecordGroups returns the RecordGroups in this Message.
func (r *Response) getRecordGroups() (recordGroups []RecordGroup) {

	recordGroups = make([]RecordGroup, len(r.RecordGroups))
	for idx, rg := range r.RecordGroups {
		recordGroups[idx] = rg
	}

	return
}