//
// Copyright (c) SAS Institute 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 comdoc

import (
	"unicode/utf16"
)

type SecID int32
type DirType uint8
type Color uint8

const (
	SecIDFree       SecID = -1
	SecIDEndOfChain SecID = -2
	SecIDSAT        SecID = -3
	SecIDMSAT       SecID = -4

	DirEmpty   DirType = 0
	DirStorage DirType = 1
	DirStream  DirType = 2
	DirRoot    DirType = 5

	Red   Color = 0
	Black Color = 1

	byteOrderMarker uint16 = 0xfffe
	msatInHeader           = 109
)

var fileMagic = []byte{0xd0, 0xcf, 0x11, 0xe0, 0xa1, 0xb1, 0x1a, 0xe1}

// Raw CDF file header
type Header struct {
	Magic            [8]byte
	UID              [16]byte
	Revision         uint16
	Version          uint16
	ByteOrder        uint16
	SectorSize       uint16 // power of 2
	ShortSectorSize  uint16 // power of 2
	Reserved1        [6]byte
	DirSectorCount   uint32 // undocumented?
	SATSectors       uint32
	DirNextSector    SecID
	Reserved2        uint32
	MinStdStreamSize uint32
	SSATNextSector   SecID
	SSATSectorCount  uint32
	MSATNextSector   SecID
	MSATSectorCount  uint32
	MSAT             [msatInHeader]SecID
}

// Raw CDF directory entry
type RawDirEnt struct {
	NameRunes   [32]uint16
	NameLength  uint16
	Type        DirType
	Color       Color
	LeftChild   int32
	RightChild  int32
	StorageRoot int32
	UID         [16]byte
	UserFlags   uint32
	CreateTime  uint64
	ModifyTime  uint64
	NextSector  SecID
	StreamSize  uint32
	_           uint32
}

// Return the UTF8 name of this entry
func (e RawDirEnt) Name() string {
	used := e.NameLength/2 - 1
	if e.Type == DirEmpty || used > 32 {
		return ""
	}
	return string(utf16.Decode(e.NameRunes[:used]))
}

// Parsed CDF directory entry
type DirEnt struct {
	RawDirEnt
	// Index into the directory stream holding this entry
	Index int
	name  string
}

// Return the UTF8 name of this entry
func (e DirEnt) Name() string {
	return e.name
}