use std::fmt;
use std::io::{BufReader, SeekFrom, Seek, Read};
use std::fs::File;
use byteorder::{BigEndian, ReadBytesExt};
use std::char::{decode_utf16, REPLACEMENT_CHARACTER};
use crate::{Error, read_box_header, BoxHeader, HEADER_SIZE};

pub type Result<T> = std::result::Result<T, Error>;

#[derive(Clone, Copy, PartialEq)]
pub enum BoxType {
    FtypBox,
    MvhdBox,
    FreeBox,
    MdatBox,
    MoovBox,
    MoofBox,
    TkhdBox,
    EdtsBox,
    MdiaBox,
    ElstBox,
    MdhdBox,
    HdlrBox,
    MinfBox,
    VmhdBox,
    StblBox,
    StsdBox,
    SttsBox,
    TrakBox,
    UdtaBox,
    DinfBox,
    SmhdBox,
    Avc1Box,
    Mp4aBox,
    UnknownBox(u32),
}

impl From<u32> for BoxType {
    fn from(t: u32) -> BoxType {
        use self::BoxType::*;
        match t {
            0x66747970 => FtypBox,
            0x6d766864 => MvhdBox,
            0x66726565 => FreeBox,
            0x6d646174 => MdatBox,
            0x6d6f6f76 => MoovBox,
            0x6d6f6f66 => MoofBox ,
            0x746b6864 => TkhdBox,
            0x65647473 => EdtsBox,
            0x6d646961 => MdiaBox,
            0x656c7374 => ElstBox,
            0x6d646864 => MdhdBox,
            0x68646c72 => HdlrBox,
            0x6d696e66 => MinfBox,
            0x766d6864 => VmhdBox,
            0x7374626c => StblBox,
            0x73747364 => StsdBox,
            0x73747473 => SttsBox,
            0x7472616b => TrakBox,
            0x75647461 => UdtaBox,
            0x64696e66 => DinfBox,
            0x736d6864 => SmhdBox,
            0x61766331 => Avc1Box,
            0x6d703461 => Mp4aBox,
            _ => UnknownBox(t),
        }
    }
}

impl Into<u32> for BoxType {
    fn into(self) -> u32 {
        use self::BoxType::*;
        match self {
            FtypBox => 0x66747970,
            MvhdBox => 0x6d766864,
            FreeBox => 0x66726565,
            MdatBox => 0x6d646174,
            MoovBox => 0x6d6f6f76,
            MoofBox => 0x6d6f6f66,
            TkhdBox => 0x746b6864,
            EdtsBox => 0x65647473,
            MdiaBox => 0x6d646961,
            ElstBox => 0x656c7374,
            MdhdBox => 0x6d646864,
            HdlrBox => 0x68646c72,
            MinfBox => 0x6d696e66,
            VmhdBox => 0x766d6864,
            StblBox => 0x7374626c,
            StsdBox => 0x73747364,
            SttsBox => 0x73747473,
            TrakBox => 0x7472616b,
            UdtaBox => 0x75647461,
            DinfBox => 0x64696e66,
            SmhdBox => 0x736d6864,
            Avc1Box => 0x61766331,
            Mp4aBox => 0x6d703461,

            UnknownBox(t) => t,
        }
    }
}

impl fmt::Debug for BoxType {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let fourcc: FourCC = From::from(self.clone());
        write!(f, "{}", fourcc)
    }
}

#[derive(Default, PartialEq, Clone)]
pub struct FourCC {
    pub value: String
}

impl From<u32> for FourCC {
    fn from(number: u32) -> FourCC {
        let mut box_chars = Vec::new();
        for x in 0..4 {
            let c = (number >> (x * 8) & 0x0000_00FF) as u8;
            box_chars.push(c);
        }
        box_chars.reverse();

        let box_string = match String::from_utf8(box_chars) {
            Ok(t) => t,
            _ => String::from("null"), // error to retrieve fourcc
        };

        FourCC {
            value: box_string
        }
    }
}

impl From<BoxType> for FourCC {
    fn from(t: BoxType) -> FourCC {
        let box_num: u32 = Into::into(t);
        From::from(box_num)
    }
}

impl fmt::Debug for FourCC {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.value)
    }
}

impl fmt::Display for FourCC {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.value)
    }
}

#[derive(Debug, Default)]
pub struct FtypBox {
    pub major_brand: FourCC,
    pub minor_version: u32,
    pub compatible_brands: Vec<FourCC>,
}

#[derive(Debug, Default)]
pub struct MoovBox {
    pub mvhd: MvhdBox,
    pub traks: Vec<TrakBox>,
}

impl MoovBox {
    pub(crate) fn new() -> MoovBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct MvhdBox {
    pub version: u8,
    pub flags: u32,
    pub creation_time: u32,
    pub modification_time: u32,
    pub timescale: u32,
    pub duration: u32,
    pub rate: u32,
}

#[derive(Debug, Default)]
pub struct TrakBox {
    pub tkhd: Option<TkhdBox>,
    pub edts: Option<EdtsBox>,
    pub mdia: Option<MdiaBox>,
}

impl TrakBox {
    pub(crate) fn new() -> TrakBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct TkhdBox {
    pub version: u8,
    pub flags: u32,
    pub creation_time: u32,
    pub modification_time: u32,
    pub track_id: u32,
    pub duration: u64,
    pub layer:  u16,
    pub alternate_group: u16,
    pub volume: u16,
    pub matrix: Matrix,
    pub width: u32,
    pub height: u32,
}

#[derive(Debug, Default)]
pub struct Matrix {
    pub a: i32,
    pub b: i32,
    pub u: i32,
    pub c: i32,
    pub d: i32,
    pub v: i32,
    pub x: i32,
    pub y: i32,
    pub w: i32,
}

#[derive(Debug, Default)]
pub struct EdtsBox {
    pub elst: Option<ElstBox>,
}

impl EdtsBox {
    pub(crate) fn new() -> EdtsBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct ElstBox {
    pub version: u32,
    pub entry_count: u32,
    pub entries: Vec<ElstEntry>,
}

#[derive(Debug, Default)]
pub struct ElstEntry {
    pub segment_duration: u32,
    pub media_time: u32,
    pub media_rate: u16,
    pub media_rate_fraction: u16,
}

#[derive(Debug, Default)]
pub struct MdiaBox {
    pub mdhd: Option<MdhdBox>,
    pub hdlr: Option<HdlrBox>,
    pub minf: Option<MinfBox>,
}

impl MdiaBox {
    pub(crate) fn new() -> MdiaBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct MdhdBox {
    pub version: u8,
    pub flags: u32,
    pub creation_time: u32,
    pub modification_time: u32,
    pub timescale: u32,
    pub duration: u32,
    pub language: u16,
    pub language_string: String,
}

#[derive(Debug, Default)]
pub struct HdlrBox {
    pub version: u8,
    pub flags: u32,
    pub handler_type: FourCC,
    pub name: String,
}

#[derive(Debug, Default)]
pub struct MinfBox {
    pub vmhd: Option<VmhdBox>,
    pub stbl: Option<StblBox>,
}

impl MinfBox {
    pub(crate) fn new() -> MinfBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct VmhdBox {
    pub version: u8,
    pub flags: u32,
    pub graphics_mode: u16,
    pub op_color: u16,
}

#[derive(Debug, Default)]
pub struct StblBox {
    pub stts: Option<SttsBox>,
    pub stsd: Option<StsdBox>,
}

impl StblBox {
    pub(crate) fn new() -> StblBox {
        Default::default()
    }
}

#[derive(Debug, Default)]
pub struct SttsBox {
    pub version: u8,
    pub flags: u32,
    pub entry_count: u32,
    pub sample_counts: Vec<u32>,
    pub sample_deltas: Vec<u32>,
}

#[derive(Debug, Default)]
pub struct StsdBox {
    pub version: u8,
    pub flags: u32,
}

pub fn parse_ftyp_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<FtypBox> {
    let major = f.read_u32::<BigEndian>().unwrap();
    let minor = f.read_u32::<BigEndian>().unwrap();
    if size % 4 != 0 {
        return Err(Error::InvalidData("invalid ftyp size"));
    }
    let brand_count = (size - 16) / 4; // header + major + minor

    let mut brands = Vec::new();
    for _ in 0..brand_count {
        let b = f.read_u32::<BigEndian>().unwrap();
        brands.push(From::from(b));
    }

    Ok(FtypBox {
        major_brand: From::from(major),
        minor_version: minor,
        compatible_brands: brands,
    })
}

pub(crate) fn parse_moov_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<MoovBox> {
    let mut moov = MoovBox::new();

    let mut start = 0u64;
    while start < size as u64 {

        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::MvhdBox => {
                moov.mvhd = parse_mvhd_box(f, 0, s as u32).unwrap();
            }
            BoxType::TrakBox => {
                let trak = parse_trak_box(f, 0, s as u32).unwrap();
                moov.traks.push(trak);
            }
            BoxType::UdtaBox => {
                start = (s as u32 - HEADER_SIZE) as u64;
            }
            _ => break
        }
    }
    Ok(moov)
}

fn parse_mvhd_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<MvhdBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    let creation_time = f.read_u32::<BigEndian>().unwrap();
    let modification_time = f.read_u32::<BigEndian>().unwrap();
    let timescale = f.read_u32::<BigEndian>().unwrap();
    let duration = f.read_u32::<BigEndian>().unwrap();
    let rate = f.read_u32::<BigEndian>().unwrap();

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(MvhdBox{
        version,
        flags,
        creation_time,
        modification_time,
        timescale,
        duration,
        rate,
    })
}

fn parse_trak_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<TrakBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.
    let mut trak = TrakBox::new();

    let start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::TkhdBox => {
                let tkhd = parse_tkhd_box(f, 0, s as u32).unwrap();
                trak.tkhd = Some(tkhd);
            }
            BoxType::EdtsBox => {
                let edts = parse_edts_box(f, 0, s as u32).unwrap();
                trak.edts = Some(edts);
            }
            BoxType::MdiaBox => {
                let mdia = parse_mdia_box(f, 0, s as u32).unwrap();
                trak.mdia = Some(mdia);
            }
            _ => break
        }
    }

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();
    Ok(trak)
}


fn parse_tkhd_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<TkhdBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    let creation_time = f.read_u32::<BigEndian>().unwrap();
    let modification_time = f.read_u32::<BigEndian>().unwrap();
    let track_id = f.read_u32::<BigEndian>().unwrap();
    let duration = f.read_u64::<BigEndian>().unwrap();
    f.read_u64::<BigEndian>().unwrap(); // skip.
    let layer = f.read_u16::<BigEndian>().unwrap();
    let alternate_group = f.read_u16::<BigEndian>().unwrap();
    let volume = f.read_u16::<BigEndian>().unwrap() >> 8;

    f.read_u8().unwrap(); // skip.
    let matrix = Matrix{
        a: f.read_i32::<byteorder::LittleEndian>().unwrap(),
        b: f.read_i32::<BigEndian>().unwrap(),
        u: f.read_i32::<BigEndian>().unwrap(),
        c: f.read_i32::<BigEndian>().unwrap(),
        d: f.read_i32::<BigEndian>().unwrap(),
        v: f.read_i32::<BigEndian>().unwrap(),
        x: f.read_i32::<BigEndian>().unwrap(),
        y: f.read_i32::<BigEndian>().unwrap(),
        w: f.read_i32::<BigEndian>().unwrap(),
    };

    let width = f.read_u32::<BigEndian>().unwrap() >> 8;
    let height = f.read_u32::<BigEndian>().unwrap() >> 8;

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(TkhdBox {
        version,
        flags,
        creation_time,
        modification_time,
        track_id,
        duration,
        layer,
        alternate_group,
        volume,
        matrix,
        width,
        height,
    })
}

fn parse_edts_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<EdtsBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.
    let mut edts = EdtsBox::new();

    let start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::ElstBox => {
                let elst = parse_elst_box(f, 0, s as u32).unwrap();
                edts.elst = Some(elst);
            }
            _ => break
        }
    }

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();
    Ok(edts)
}

fn parse_elst_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<ElstBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u32::<BigEndian>().unwrap();
    let entry_count = f.read_u32::<BigEndian>().unwrap();

    let mut entries = Vec::new();

    for _i in 0..entry_count {
        let entry = ElstEntry{
            segment_duration: f.read_u32::<BigEndian>().unwrap(),
            media_time: f.read_u32::<BigEndian>().unwrap(),
            media_rate: f.read_u16::<BigEndian>().unwrap(),
            media_rate_fraction: f.read_u16::<BigEndian>().unwrap(),
        };
        entries.push(entry);
    }

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(ElstBox {
        version,
        entry_count,
        entries,
    })
}

fn parse_mdia_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<MdiaBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.
    let mut mdia = MdiaBox::new();

    let start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::MdhdBox => {
                let mdhd = parse_mdhd_box(f, 0, s as u32).unwrap();
                mdia.mdhd = Some(mdhd);
            }
            BoxType::HdlrBox => {
                let hdlr = parse_hdlr_box(f, 0, s as u32).unwrap();
                mdia.hdlr = Some(hdlr);
            }
            BoxType::MinfBox => {
                let minf = parse_minf_box(f, 0, s as u32).unwrap();
                mdia.minf = Some(minf);
            }
            _ => break
        }
    }

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();
    Ok(mdia)
}

fn parse_mdhd_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<MdhdBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    let creation_time = f.read_u32::<BigEndian>().unwrap();
    let modification_time = f.read_u32::<BigEndian>().unwrap();
    let timescale = f.read_u32::<BigEndian>().unwrap();
    let duration = f.read_u32::<BigEndian>().unwrap();
    let language = f.read_u16::<BigEndian>().unwrap();
    let language_string = get_language_string(language);

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(MdhdBox {
        version,
        flags,
        creation_time,
        modification_time,
        timescale,
        duration,
        language,
        language_string,
    })
}

fn get_language_string(language: u16) -> String {
    let mut lang: [u16; 3] = [0; 3];

    lang[0] = ((language >> 10) & 0x1F) + 0x60;
    lang[1] = ((language >> 5) & 0x1F) + 0x60;
    lang[2] = ((language) & 0x1F) + 0x60;

    // Decode utf-16 encoded bytes into a string.
    let lang_str = decode_utf16(lang.iter().cloned())
        .map(|r| r.unwrap_or(REPLACEMENT_CHARACTER))
        .collect::<String>();

    return lang_str;
}

fn parse_hdlr_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<HdlrBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    f.read_u32::<BigEndian>().unwrap(); // skip.
    let handler = f.read_u32::<BigEndian>().unwrap();

    let n = f.seek(SeekFrom::Current(12)).unwrap(); // 12 bytes reserved.
    let buf_size = (size as u64 - (n - current)) - HEADER_SIZE as u64;
    let mut buf = vec![0u8; buf_size as usize];
    f.read_exact(&mut buf).unwrap();

    let handler_string = match String::from_utf8(buf) {
        Ok(t) => t,
        _ => String::from("null"),
    };

    // Skip remaining bytes.
    let after = f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(HdlrBox {
        version,
        flags,
        handler_type: From::from(handler),
        name: handler_string,
    })
}

fn parse_minf_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<MinfBox> {
    let current =  f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.
    let mut minf = MinfBox::new();

    let mut start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::VmhdBox => {
                let vmhd = parse_vmhd_box(f, 0, s as u32).unwrap();
                minf.vmhd = Some(vmhd);
            }
            BoxType::SmhdBox => {
                start = (s as u32 - HEADER_SIZE) as u64;
            }
            BoxType::DinfBox => {
                start = (s as u32 - HEADER_SIZE) as u64;
            }
            BoxType::StblBox => {
                let stbl = parse_stbl_box(f, 0, s as u32).unwrap();
                minf.stbl = Some(stbl);
            }
            _ => break
        }
    }

    // Skip remaining bytes.
    let after =  f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();
    Ok(minf)
}

fn parse_vmhd_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<VmhdBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    let graphics_mode = f.read_u16::<BigEndian>().unwrap();
    let op_color = f.read_u16::<BigEndian>().unwrap();

    // Skip remaining bytes.
    let after = f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(VmhdBox {
        version,
        flags,
        graphics_mode,
        op_color,
    })
}

fn parse_stbl_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<StblBox> {
    let mut stbl = StblBox::new();

    let start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::StsdBox => {
                let stsd = parse_stsd_box(f, 0, s as u32).unwrap();
                stbl.stsd = Some(stsd);
            }
            BoxType::SttsBox => {
                let stts = parse_stts_box(f, 0, s as u32).unwrap();
                stbl.stts = Some(stts);
            }
            _ => break
        }
    }
    Ok(stbl)
}

fn parse_stts_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<SttsBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    let entry_count = f.read_u32::<BigEndian>().unwrap();
    let mut sample_counts = Vec::new();
    let mut sample_deltas = Vec::new();

    for _i in 0..entry_count {
        let sc = f.read_u32::<BigEndian>().unwrap();
        let sd = f.read_u32::<BigEndian>().unwrap();
        sample_counts.push(sc);
        sample_deltas.push(sd);
    }

    // Skip remaining bytes.
    let after = f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();

    Ok(SttsBox {
        version,
        flags,
        entry_count,
        sample_counts,
        sample_deltas,
    })
}

fn parse_stsd_box(f: &mut BufReader<File>, _offset: u64, size: u32) -> Result<StsdBox> {
    let current = f.seek(SeekFrom::Current(0)).unwrap(); // Current cursor position.

    let version = f.read_u8().unwrap();
    let flags_a = f.read_u8().unwrap();
    let flags_b = f.read_u8().unwrap();
    let flags_c = f.read_u8().unwrap();
    let flags = u32::from(flags_a) << 16 | u32::from(flags_b) << 8 | u32::from(flags_c);
    f.read_u32::<BigEndian>().unwrap(); // skip.

    let mut start = 0u64;
    while start < size as u64 {
        // Get box header.
        let header = read_box_header(f, start).unwrap();
        let BoxHeader{ name, size: s, offset: _ } = header;

        match name {
            BoxType::Avc1Box => {
                start = (s as u32 - HEADER_SIZE) as u64;
            }
            BoxType::Mp4aBox => {
                start = (s as u32 - HEADER_SIZE) as u64;
            }
            _ => break
        }
    }

    // Skip remaining bytes.
    let after = f.seek(SeekFrom::Current(0)).unwrap();
    let remaining_bytes = (size as u64 - (after - current)) as i64;
    f.seek(SeekFrom::Current(remaining_bytes - HEADER_SIZE as i64)).unwrap();
    Ok(StsdBox {
        version,
        flags,
    })
}