// Copyright 2024 Martin Riedl
//
// 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 gomp4

import (
	"encoding/binary"
	"time"
)

// TrackHeaderBox track header box struct
//
// 8.3.2 Track Header Box
//
// Box Type: ‘tkhd’
// Container: Track Box (‘trak’)
// Mandatory: Yes
// Quantity: Exactly one
//
// This box specifies the characteristics of a single track. Exactly one Track Header Box is contained in a
// track.
//
// In the absence of an edit list, the presentation of a track starts at the beginning of the overall
// presentation. An empty edit is used to offset the start time of a track.
//
// The default value of the track header flags for media tracks is 7 (track_enabled, track_in_movie,
// track_in_preview). If in a presentation all tracks have neither track_in_movie nor track_in_preview set,
// then all tracks shall be treated as if both flags were set on all tracks. Server hint tracks should have the
// track_in_movie and track_in_preview set to 0, so that they are ignored for local playback and
// preview.
//
// Under the ‘iso3’ brand or brands that share its requirements, the width and height in the track header
// are measured on a notional 'square' (uniform) grid. Track video data is normalized to these dimensions
// (logically) before any transformation or placement caused by a layup or composition system. Track
// (and movie) matrices, if used, also operate in this uniformly‐scaled space.
//
// The duration field here does not include the duration of following movie fragments, if any, but only of
// the media in the enclosing Movie Box. The Movie Extends Header box may be used to document the
// duration including movie fragments, when desired and possible.
type TrackHeaderBox struct {
	*FullBox
	// is an integer that declares the creation time of this track (in seconds since
	// midnight, Jan. 1, 1904, in UTC time).
	CreationTimeV0 time.Time
	// is an integer that declares the creation time of this track (in seconds since
	// midnight, Jan. 1, 1904, in UTC time).
	CreationTimeV1 time.Time
	// is an integer that declares the most recent time the track was modified (in
	// seconds since midnight, Jan. 1, 1904, in UTC time).
	ModificationTimeV0 time.Time
	// is an integer that declares the most recent time the track was modified (in
	// seconds since midnight, Jan. 1, 1904, in UTC time).
	ModificationTimeV1 time.Time
	// is an integer that uniquely identifies this track over the entire life‐time of this
	// presentation. Track IDs are never re‐used and cannot be zero.
	TrackID uint32
	// is an integer that indicates the duration of this track (in the timescale indicated in the
	// Movie Header Box). The value of this field is equal to the sum of the durations of all of the track’s
	// edits. If there is no edit list, then the duration is the sum of the sample durations, converted into
	// the timescale in the Movie Header Box. If the duration of this track cannot be determined then
	// duration is set to all 1s.
	DurationV0 uint32
	// is an integer that indicates the duration of this track (in the timescale indicated in the
	// Movie Header Box). The value of this field is equal to the sum of the durations of all of the track’s
	// edits. If there is no edit list, then the duration is the sum of the sample durations, converted into
	// the timescale in the Movie Header Box. If the duration of this track cannot be determined then
	// duration is set to all 1s.
	DurationV1 uint64
	// specifies the front‐to‐back ordering of video tracks; tracks with lower numbers are closer
	// to the viewer. 0 is the normal value, and ‐1 would be in front of track 0, and so on.
	Layer int16
	// is an integer that specifies a group or collection of tracks. If this field is 0
	// there is no information on possible relations to other tracks. If this field is not 0, it should be the
	// same for tracks that contain alternate data for one another and different for tracks belonging to
	// different such groups. Only one track within an alternate group should be played or streamed at
	// any one time, and must be distinguishable from other tracks in the group via attributes such as
	// bitrate, codec, language, packet size etc. A group may have only one member.
	AlternativeGroup int16
	// is a fixed 8.8 value specifying the track's relative audio volume. Full volume is 1.0
	// (0x0100) and is the normal value. Its value is irrelevant for a purely visual track. Tracks may be
	// composed by combining them according to their volume, and then using the overall Movie
	// Header Box volume setting; or more complex audio composition (e.g. MPEG‐4 BIFS) may be
	// used.
	Volume Fixed88
	// provides a transformation matrix for the video; (u,v,w) are restricted here to (0,0,1), hex
	// (0,0,0x40000000).
	Matrix []int32
	// fixed‐point 16.16 values are track‐dependent as follows:
	//
	// For text and subtitle tracks, they may, depending on the coding format, describe the suggested
	// size of the rendering area. For such tracks, the value 0x0 may also be used to indicate that the
	// data may be rendered at any size, that no preferred size has been indicated and that the actual
	// size may be determined by the external context or by reusing the width and height of another
	// track. For those tracks, the flag track_size_is_aspect_ratio may also be used.
	// For non‐visual tracks (e.g. audio), they should be set to zero.
	// For all other tracks, they specify the track's visual presentation size. These need not be the same
	// as the pixel dimensions of the images, which is documented in the sample description(s); all
	// images in the sequence are scaled to this size, before any overall transformation of the track
	// represented by the matrix. The pixel dimensions of the images are the default values.
	Width Fixed1616
	// fixed‐point 16.16 values are track‐dependent as follows:
	//
	// For text and subtitle tracks, they may, depending on the coding format, describe the suggested
	// size of the rendering area. For such tracks, the value 0x0 may also be used to indicate that the
	// data may be rendered at any size, that no preferred size has been indicated and that the actual
	// size may be determined by the external context or by reusing the width and height of another
	// track. For those tracks, the flag track_size_is_aspect_ratio may also be used.
	// For non‐visual tracks (e.g. audio), they should be set to zero.
	// For all other tracks, they specify the track's visual presentation size. These need not be the same
	// as the pixel dimensions of the images, which is documented in the sample description(s); all
	// images in the sequence are scaled to this size, before any overall transformation of the track
	// represented by the matrix. The pixel dimensions of the images are the default values.
	Height Fixed1616
}

const (
	// TrackHeaderBoxFlagTrackEnabled Track Enabled Flag
	// Indicates that the track is enabled. Flag value is 0x000001. A disabled track (the
	// low bit is zero) is treated as if it were not present.
	TrackHeaderBoxFlagTrackEnabled uint32 = 0x00000001

	// TrackHeaderBoxFlagTrackInMovie Track in Movie
	// Indicates that the track is used in the presentation. Flag value is 0x000002.
	TrackHeaderBoxFlagTrackInMovie uint32 = 0x00000002

	// TrackHeaderBoxFlagTrackInPreview Track in Preview
	// Indicates that the track is used when previewing the presentation. Flag value
	// is 0x000004.
	TrackHeaderBoxFlagTrackInPreview uint32 = 0x00000004

	// TrackHeaderBoxFlagTrackSizeIsAspectRatio Track Size is Aspect Ratio
	// Indicates that the width and height fields are not expressed in
	// pixel units. The values have the same units but these units are not specified. The values are
	// only an indication of the desired aspect ratio. If the aspect ratios of this track and other
	// related tracks are not identical, then the respective positioning of the tracks is undefined,
	// possibly defined by external contexts. Flag value is 0x000008.
	TrackHeaderBoxFlagTrackSizeIsAspectRatio uint32 = 0x00000008
)

// ParseTrackHeaderBox creates a new Track Header Box struct
func ParseTrackHeaderBox(filePosition uint64, headerSize uint32, content []byte) *TrackHeaderBox {
	box := &TrackHeaderBox{
		FullBox: newFullBox(&Box{filePosition, headerSize}, content[0:4]),
	}

	position := 4
	if box.Version == 1 {
		box.CreationTimeV1 = since1904ToTime(int64(binary.BigEndian.Uint64(content[4:12])))
		box.ModificationTimeV1 = since1904ToTime(int64(binary.BigEndian.Uint64(content[12:20])))
		box.TrackID = binary.BigEndian.Uint32(content[20:24])
		// uint32 reserved
		box.DurationV1 = binary.BigEndian.Uint64(content[28:36])
		position += 32
	} else { // version == 0
		box.CreationTimeV0 = since1904ToTime(int64(binary.BigEndian.Uint32(content[4:8])))
		box.ModificationTimeV0 = since1904ToTime(int64(binary.BigEndian.Uint32(content[8:12])))
		box.TrackID = binary.BigEndian.Uint32(content[12:16])
		// uint32 reserved
		box.DurationV0 = binary.BigEndian.Uint32(content[20:24])
		position += 20
	}

	// skip 2 reserved uint32
	position += 4 + 4

	// parse next fields
	box.Layer = int16(binary.BigEndian.Uint16(content[position : position+2]))
	box.AlternativeGroup = int16(binary.BigEndian.Uint16(content[position+2 : position+4]))
	box.Volume = NewFixed88ByBytes(content[position+4 : position+6])
	position += 2 + 2 + 2 + 2 // 4 bytes for layer, 2 bytes for alternative group, 2 bytes for volume and 2 bytes reserved

	// parse matrix
	for i := 0; i < 9; i++ {
		box.Matrix = append(box.Matrix, int32(binary.BigEndian.Uint32(content[position:position+4])))
		position += 4
	}

	// parse width/height
	box.Width = NewFixed1616ByBytes(content[position : position+4])
	box.Height = NewFixed1616ByBytes(content[position+4 : position+8])

	return box
}