/*
 * Copyright 2021 ByteDance Inc.
 *
 * 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 ast

import (
	`sync`
)

const (
	_MaxBuffer = 4 * 1024    // 4KB buffer size
)

var (
	bytesNull   = []byte("null")
	bytesTrue   = []byte("true")
	bytesFalse  = []byte("false")
	bytesObject = []byte("{}")
	bytesArray  = []byte("[]")

	lenNull   = len("null")
	lenTrue   = len("true")
	lenFalse  = len("false")
	lenObject = len("{}")
	lenArray  = len("[]")
)

var bytesPool   = sync.Pool{}

func (self *Node) MarshalJSON() ([]byte, error) {
	buf := newBuffer()
	err := self.encode(buf)
	ret := make([]byte, len(*buf))
	copy(ret, *buf)
	freeBuffer(buf)
	return ret, err
}

func newBuffer() *[]byte {
    if ret := bytesPool.Get(); ret != nil {
        return ret.(*[]byte)
    } else {
		buf := make([]byte, 0, _MaxBuffer)
		return &buf
    }
}

func freeBuffer(buf *[]byte) {
    *buf = (*buf)[:0]
    bytesPool.Put(buf)
}

func (self *Node) encode(buf *[]byte) error {
	if self.IsRaw() {
		return self.encodeRaw(buf)
	}
	switch self.Type() {
		case V_NONE  : return ErrNotExist
		case V_ERROR : return self.Check()
		case V_NULL  : return self.encodeNull(buf)
		case V_TRUE  : return self.encodeTrue(buf)
		case V_FALSE : return self.encodeFalse(buf)
		case V_ARRAY : return self.encodeArray(buf)
		case V_OBJECT: return self.encodeObject(buf)
		case V_STRING: return self.encodeString(buf)
		case V_NUMBER: return self.encodeNumber(buf)
		default      : return ErrUnsupportType 
	}
}

func (self *Node) encodeRaw(buf *[]byte) error {
	raw, err := self.Raw()
	if err != nil {
		return err
	}
	*buf = append(*buf, raw...)
	return nil
}

func (self *Node) encodeNull(buf *[]byte) error {
	*buf = append(*buf, bytesNull...)
	return nil
}

func (self *Node) encodeTrue(buf *[]byte) error {
	*buf = append(*buf, bytesTrue...)
	return nil
}

func (self *Node) encodeFalse(buf *[]byte) error {
	*buf = append(*buf, bytesFalse...)
	return nil
}

func (self *Node) encodeNumber(buf *[]byte) error {
	str := addr2str(self.p, self.v)
	*buf = append(*buf, str...)
	return nil
}

func (self *Node) encodeString(buf *[]byte) error {
	str := addr2str(self.p, self.v)
	*buf = append(*buf, '"')
	*buf = append(*buf, str...)
	*buf = append(*buf, '"')
	return nil
}

func (self *Node) encodeArray(buf *[]byte) error {
	if self.isLazy() {
		if err := self.skipAllIndex(); err != nil {
			return err
		}
	}

	nb := self.len()
	if nb == 0 {
		*buf = append(*buf, bytesArray...)
		return nil
	}
	
	*buf = append(*buf, '[')

    var p = (*Node)(self.p)
	err := p.encode(buf)
	if err != nil {
		return err
	}
    for i := 1; i < nb; i++ {
		*buf = append(*buf, ',')
        p = p.unsafe_next()
        err := p.encode(buf)
		if err != nil {
			return err
		}
	}

	*buf = append(*buf, ']')
    return nil
}

func (self *Pair) encode(buf *[]byte) error {
	*buf = append(*buf, '"')
	*buf = append(*buf, self.Key...)
	*buf = append(*buf, '"', ':')
	return self.Value.encode(buf)
}

func (self *Node) encodeObject(buf *[]byte) error {
	if self.isLazy() {
		if err := self.skipAllKey(); err != nil {
			return err
		}
	}
	
	nb := self.len()
	if nb == 0 {
		*buf = append(*buf, bytesObject...)
		return nil
	}
	
	*buf = append(*buf, '{')

    var p = (*Pair)(self.p)
	err := p.encode(buf)
	if err != nil {
		return err
	}
    for i := 1; i < nb; i++ {
		*buf = append(*buf, ',')
        p = p.unsafe_next()
        err := p.encode(buf)
		if err != nil {
			return err
		}
	}

	*buf = append(*buf, '}')
    return nil
}