// ------------------------------------------------------------------------
//   Project atila
//   Active Thing (activething.com) git.activething.com/go
//
//   File name  buffer.go
//   Created by DEV
//   Modified   16/01/2024
//
//   Copyright 2024 activething.com
// ------------------------------------------------------------------------
// 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 bins

import (
	"activething.com/go/gogo/core/bins/chars"
	"bytes"

	"io"
	"unicode/utf8"
)

const (
	maxInt = int(^uint(0) >> 1)

	MinRead = 512
)


type (


	Buffer struct {
		data   []byte
		off    int
		ini    [64]byte
		lastOp bufferOp
	}

)

func NewBuffer() *Buffer {
	return &Buffer{} }


func (b *Buffer) Len() int {
	return len(b.data) - b.off }


func (b *Buffer) Cap() int {
	return cap(b.data) }


func (b *Buffer) isEmpty() bool {
	return len(b.data) <= b.off }


func (b *Buffer) Bytes() []byte {
	return b.data[b.off:] }


func (b *Buffer) String() string {
	if b == nil {
		return "<nil>"
	}
	return string(b.data[b.off:])
}


func (b *Buffer) Reset() {
	b.data = b.data[:0]
	b.off = 0
	b.lastOp = opInvalid
}


func (b *Buffer) Truncate(size int) {
	if size == 0 {
		b.Reset()
		return
	}
	b.lastOp = opInvalid
	if size < 0 || size > b.Len() {
		panic(G.ErrOutOfRange)
	}
	b.data = b.data[:b.off+size]
}


func (b *Buffer) Read(data []byte) (count int, err error) {
	b.lastOp = opInvalid
	if b.isEmpty() {
		b.Reset()
		if len(data) == 0 {
			return 0, nil
		}
		return 0, io.EOF
	}
	count = copy(data, b.data[b.off:])
	b.off += count
	if count > 0 {
		b.lastOp = opRead
	}
	return count, nil
}


func (b *Buffer) ReadFrom(reader io.Reader) (count int64, err error) {
	b.lastOp = opInvalid
	for {
		i := b.tryGrowByStrategy(MinRead)
		b.data = b.data[:i]
		m, e := reader.Read(b.data[i:cap(b.data)])
		if m < 0 {
			panic(G.ErrNegativeRead)
		}
		b.data = b.data[:i+m]
		count += int64(m)
		if e == io.EOF {
			return count, nil
		}
		if e != nil {
			return count, e
		}
	}
}


func (b *Buffer) ReadByte() (byte, error) {
	if b.isEmpty() {
		b.Reset()
		return 0, io.EOF
	}
	c := b.data[b.off]
	b.off++
	b.lastOp = opRead
	return c, nil
}


func (b *Buffer) ReadBytes(delimiter byte) (result []byte, er error) {
	slice, er := b.readSlice(delimiter)
	result = append(result, slice...)
	return result, er
}


func (b *Buffer) ReadString(delimiter byte) (result string, err error) {
	slice, err := b.readSlice(delimiter)
	return string(slice), err
}


func (b *Buffer) ReadRune() (run rune, size int, err error) {
	if b.isEmpty() {
		b.Reset()
		return 0, 0, io.EOF
	}
	c := b.data[b.off]
	if c < utf8.RuneSelf {
		b.off++
		b.lastOp = opRune
		return rune(c), 1, nil
	}
	r, n := utf8.DecodeRune(b.data[b.off:])
	b.off += n
	b.lastOp = bufferOp(n)
	return r, n, nil
}


func (b *Buffer) readSlice(delimiter byte) (ln []byte, er error) {
	i := bytes.IndexByte(b.data[b.off:], delimiter)
	end := b.off + i + 1
	if i < 0 {
		end = len(b.data)
		er = io.EOF
	}
	ln = b.data[b.off:end]
	b.off = end
	b.lastOp = opRead
	return ln, er
}


func (b *Buffer) UnreadRune() error {
	if b.lastOp <= opInvalid {
		return G.ErrUnreadInvalid
	}
	if b.off >= int(b.lastOp) {
		b.off -= int(b.lastOp)
	}
	b.lastOp = opInvalid
	return nil
}


func (b *Buffer) UnreadByte() error {
	if b.lastOp == opInvalid {
		return G.ErrUnreadInvalid
	}
	b.lastOp = opInvalid
	if b.off > 0 {
		b.off--
	}
	return nil
}


func (b *Buffer) AppendWith(appender Appender) {
	b.lastOp = opInvalid
	if appender != nil {
		b.data = appender.Append(b.data)
	}
}


func (b *Buffer) Write(value []byte) (int, error) {
	b.lastOp = opInvalid
	return copy(b.data[b.tryGrow(len(value)):], value), nil
}


func (b *Buffer) W (value []byte) {
	b.lastOp = opInvalid
	copy(b.data[b.tryGrow(len(value)):], value)
}


// WOQ With Optional Quoted
func (b *Buffer) WOQ (add bool, quote byte, value []byte) {
	b.lastOp = opInvalid
	if !add {
		copy(b.data[b.tryGrow(len(value)):], value)
		return
	}
	b.WriteByte(quote)
	sz := b.tryGrow(len(value)+2)
	copy(b.data[sz:],value)
	b.WriteByte(quote)
}


func (b *Buffer) WriteHTML(source []byte) {
	st := 0
	for i,c := range source {
		if c == '<' || c == '>' || c == '&' {
			if st < i {
				b.W(source[st:i])
			}
			b.WriteString(`\u00`)
			b.WriteByte(chars.G.HEX[c>>4])
			b.WriteByte(chars.G.HEX[c&0xF])
			st = i + 1
		}
		if c == 0xE2 && i+2 < len(source) && source[i+1] == 0x80 && source[i+2]&^1 == 0xA8 {
			if st < i {
				b.W(source[st:i])
			}
			b.WriteString(`\u202`)
			b.WriteByte(chars.G.HEX[source[i+2]&0xF])
			st = i + 3
		}
		if st < len(source) {
			b.W(source[st:])
		}
	}
}


func (b *Buffer) WriteByte(value byte) {
	b.lastOp = opInvalid
	b.data[b.tryGrow(1)] = value
}


func (b *Buffer) Write2Byte(valueA, valueB byte) {
	b.lastOp = opInvalid
	p := b.tryGrow(2)
	b.data[p] = valueA
	b.data[p+1] = valueB
}


func (b *Buffer) WriteString(value string)  {
 	b.W([]byte(value)) }


func (b *Buffer) WriteTo(writer io.Writer) (int64, error) {
	return b.writeTo(writer, false) }


func (b *Buffer) FlushTo(writer io.Writer) (int64, error) {
	return b.writeTo(writer, true) }







func (b *Buffer) writeTo(writer io.Writer, reset bool) (count int64, err error) {
	if reset {
		b.lastOp = opInvalid
	}
	if nBytes := b.Len(); nBytes > 0 {
		m, e := writer.Write(b.data[b.off:])
		if m > nBytes {
			panic(G.ErrWriteCount)
		}
		b.off += m
		count = int64(m)
		if e != nil {
			return count, e
		}
		if m != nBytes {
			return count, G.ErrTooShort
		}
	}
	if reset {
		b.Reset()
	}
	return count, nil
}


func (b *Buffer) tryGrow(size int) int {
	m := len(b.data)
	if size <= cap(b.data)-m {
		b.data = b.data[:m+size]
		return m
	}
	m = b.Len()
	if m == 0 && b.off != 0 {
		b.Reset()
	}
	if i, ok := b.tryGrowByResize(size); ok {
		return i
	}
	if b.data == nil && size <= len(b.ini) {
		b.data = b.ini[:size]
		return 0
	}
	c := cap(b.data)
	if size <= c/2-m {
		copy(b.data, b.data[b.off:])
	} else if c > maxInt-c-size {
		panic(G.ErrTooLarge)
	} else {
		buf := makeSlice(2*c + size)
		copy(buf, b.data[b.off:])
		b.data = buf
	}
	b.off = 0
	b.data = b.data[:m+size]
	return m
}


func (b *Buffer) tryGrowByResize(size int) (int, bool) {
	if l := len(b.data); size <= cap(b.data)-l {
		b.data = b.data[:l+size]
		return l, true
	}
	return 0, false
}


func (b *Buffer) tryGrowByStrategy(size int) int {
	m := len(b.data)
	if m == 0 && b.off != 0 {
		b.Reset()
	}

	if i, ok := b.tryGrowByResize(size); ok {
		return i
	}

	if b.data == nil && size <= len(b.ini) {
		b.data = b.ini[:size]
		return 0
	}

	c := cap(b.data)
	if size <= c/2-m {
		copy(b.data, b.data[b.off:])
	} else if c > maxInt-c-size {
		panic(G.ErrTooLarge)
	} else {
		buf := makeSlice(2*c + size)
		copy(buf, b.data[b.off:])
		b.data = buf
	}
	b.off = 0
	b.data = b.data[:m+size]
	return m
}


func makeSlice(size int) (result []byte) {
	dn := false
	defer func(d *bool) {
		if !(*d) && recover() != nil {
			panic(G.ErrTooLarge)
		}
	}(&dn)
	result = make([]byte, size)
	dn = true
	return
}