// Copyright 2016-2019 Alex Stocks
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package hessian

import (
	"bufio"
	"bytes"
	"io"
	"reflect"
)

import (
	perrors "github.com/pkg/errors"
)

// Decoder struct
type Decoder struct {
	reader        *bufio.Reader
	refs          []interface{}
	classInfoList []classInfo
}

// Error part
var (
	ErrNotEnoughBuf    = perrors.Errorf("not enough buf")
	ErrIllegalRefIndex = perrors.Errorf("illegal ref index")
)

// NewDecoder generate a decoder instance
func NewDecoder(b []byte) *Decoder {
	return &Decoder{reader: bufio.NewReader(bytes.NewReader(b))}
}

/////////////////////////////////////////
// utilities
/////////////////////////////////////////

// peek a byte
func (d *Decoder) peekByte() byte {
	return d.peek(1)[0]
}

// get the buffer length
func (d *Decoder) len() int {
	d.peek(1) // peek one byte to get the buffer length
	return d.reader.Buffered()
}

// read a byte from Decoder, advance the ptr
func (d *Decoder) readByte() (byte, error) {
	return d.reader.ReadByte()
}

// unread a byte
func (d *Decoder) unreadByte() error {
	return d.reader.UnreadByte()
}

// read byte arr, and return the length of b
func (d *Decoder) next(b []byte) (int, error) {
	return d.reader.Read(b)
}

// peek n bytes, will not advance the read ptr
func (d *Decoder) peek(n int) []byte {
	b, _ := d.reader.Peek(n)
	return b
}

// read utf8 len(s) of array
func (d *Decoder) nextRune(s []rune) []rune {
	var (
		n   int
		i   int
		r   rune
		ri  int
		err error
	)

	n = len(s)
	s = s[:0]
	for i = 0; i < n; i++ {
		if r, ri, err = d.reader.ReadRune(); err == nil && ri > 0 {
			s = append(s, r)
		}
	}

	return s
}

// read the type of data, used to decode list or map
func (d *Decoder) decType() (string, error) {
	var (
		err error
		arr [1]byte
		buf []byte
		tag byte
		idx int32
		typ reflect.Type
	)

	buf = arr[:1]
	if _, err = io.ReadFull(d.reader, buf); err != nil {
		return "", perrors.WithStack(err)
	}
	tag = buf[0]
	if (tag >= BC_STRING_DIRECT && tag <= STRING_DIRECT_MAX) ||
		(tag >= 0x30 && tag <= 0x33) || (tag == BC_STRING) || (tag == BC_STRING_CHUNK) {
		return d.decString(int32(tag))
	}

	if idx, err = d.decInt32(TAG_READ); err != nil {
		return "", perrors.WithStack(err)
	}

	typ, _, err = d.getStructDefByIndex(int(idx))
	if err == nil {
		return typ.String(), nil
	}

	return "", err
}

// Decode parse hessian data, and ensure the reflection value unpacked
func (d *Decoder) Decode() (interface{}, error) {
	return EnsureInterface(d.DecodeValue())
}

// DecodeValue parse hessian data, the return value maybe a reflection value when it's a map, list, object, or ref.
func (d *Decoder) DecodeValue() (interface{}, error) {
	var (
		err error
		tag byte
	)

	tag, err = d.readByte()
	if err == io.EOF {
		return nil, err
	}

	switch {
	case tag == BC_END:
		// return EOF error for end flag 'Z'
		return nil, io.EOF

	case tag == BC_NULL: // 'N': //null
		return nil, nil

	case tag == BC_TRUE: // 'T': //true
		return true, nil

	case tag == BC_FALSE: //'F': //false
		return false, nil

	case tag == BC_REF: // 'R': //ref, a int which represents the previous list or map
		return d.decRef(int32(tag))

	case (0x80 <= tag && tag <= 0xbf) || (0xc0 <= tag && tag <= 0xcf) ||
		(0xd0 <= tag && tag <= 0xd7) || tag == BC_INT: //'I': //int
		return d.decInt32(int32(tag))

	case (tag >= 0xd8 && tag <= 0xef) || (tag >= 0xf0 && tag <= 0xff) ||
		(tag >= 0x38 && tag <= 0x3f) || (tag == BC_LONG_INT) || (tag == BC_LONG): //'L': //long
		return d.decInt64(int32(tag))

	case (tag == BC_DATE_MINUTE) || (tag == BC_DATE): //'d': //date
		return d.decDate(int32(tag))

	case (tag == BC_DOUBLE_ZERO) || (tag == BC_DOUBLE_ONE) || (tag == BC_DOUBLE_BYTE) ||
		(tag == BC_DOUBLE_SHORT) || (tag == BC_DOUBLE_MILL) || (tag == BC_DOUBLE): //'D': //double
		return d.decDouble(int32(tag))

	// case 'S', 's', 'X', 'x': //string,xml
	case (tag == BC_STRING_CHUNK || tag == BC_STRING) ||
		(tag >= BC_STRING_DIRECT && tag <= STRING_DIRECT_MAX) ||
		(tag >= 0x30 && tag <= 0x33):
		return d.decString(int32(tag))

		// case 'B', 'b': //binary
	case (tag == BC_BINARY) || (tag == BC_BINARY_CHUNK) || (tag >= 0x20 && tag <= 0x2f) ||
		(tag >= BC_BINARY_SHORT && tag <= 0x3f):
		return d.decBinary(int32(tag))

	// case 'V': //list
	case (tag >= BC_LIST_DIRECT && tag <= 0x77) || (tag == BC_LIST_FIXED || tag == BC_LIST_VARIABLE) ||
		(tag >= BC_LIST_DIRECT_UNTYPED && tag <= 0x7f) ||
		(tag == BC_LIST_FIXED_UNTYPED || tag == BC_LIST_VARIABLE_UNTYPED):
		return d.decList(int32(tag))

	case (tag == BC_MAP) || (tag == BC_MAP_UNTYPED):
		return d.decMap(int32(tag))

	case (tag == BC_OBJECT_DEF) || (tag == BC_OBJECT) ||
		(BC_OBJECT_DIRECT <= tag && tag <= (BC_OBJECT_DIRECT+OBJECT_DIRECT_MAX)):
		return d.decObject(int32(tag))

	default:
		return nil, perrors.Errorf("Invalid type: %v,>>%v<<<", string(tag), d.peek(d.len()))
	}
}