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// Copyright 2017 Brian Langenberger
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::io;
use std::string::FromUtf8Error;

use bitstream_io::{BitReader, BE};
use chrono::DateTime;
use chrono::offset::Utc;

/// An EBML tree element
#[derive(Debug)]
pub struct Element {
    pub id: u32,
    pub size: u64, /*total size of element, including header*/
    pub val: ElementType
}

impl Element {
    pub fn parse(r: &mut io::Read) -> Result<Element,MatroskaError> {
        let (id, size, header_len) = read_element_id_size(r)?;
        let data = Element::parse_body(r, id, size)?;
        Ok(Element{id: id, size: header_len + size, val: data})
    }

    pub fn parse_body(r: &mut io::Read, id: u32, size: u64) ->
        Result<ElementType,MatroskaError> {
        match id {
            0x80 | 0x8E | 0x8F | 0xA0 | 0xA6 | 0xAE | 0xB6 | 0xB7 | 0xBB |
            0xC8 | 0xDB | 0xE0 | 0xE1 | 0xE2 | 0xE3 | 0xE4 | 0xE8 | 0xE9 |
            0x45B9 | 0x4DBB | 0x5034 | 0x5035 | 0x55B0 | 0x55D0 | 0x5854 |
            0x61A7 | 0x6240 | 0x63C0 | 0x6624 | 0x67C8 | 0x6911 | 0x6924 |
            0x6944 | 0x6D80 | 0x7373 | 0x75A1 | 0x7E5B | 0x7E7B |
            0x1043A770 | 0x114D9B74 | 0x1254C367 | 0x1549A966 | 0x1654AE6B |
            0x18538067 | 0x1941A469 | 0x1A45DFA3 | 0x1B538667 | 0x1C53BB6B |
            0x1F43B675 => {
                Element::parse_master(r, size).map(|e| ElementType::Master(e))
            }
            0xFB | 0xFD | 0x537F | 0x75A2 => {
                read_int(r, size).map(|i| ElementType::Int(i))
            }
            0x83 | 0x88 | 0x89 | 0x91 | 0x92 | 0x96 | 0x97 | 0x98 | 0x9A |
            0x9B | 0x9C | 0x9D | 0x9F | 0xA7 | 0xAA | 0xAB | 0xB0 | 0xB2 |
            0xB3 | 0xB9 | 0xBA | 0xC0 | 0xC6 | 0xC7 | 0xC9 | 0xCA | 0xCB |
            0xCC | 0xCD | 0xCE | 0xCF | 0xD7 | 0xE5 | 0xE6 | 0xE7 | 0xEA |
            0xEB | 0xED | 0xEE | 0xF0 | 0xF1 | 0xF7 | 0xFA |
            0x4254 | 0x4285 | 0x4286 | 0x4287 | 0x42F2 | 0x42F3 | 0x42F7 |
            0x4484 | 0x4598 | 0x45BC | 0x45BD | 0x45DB | 0x45DD | 0x4661 |
            0x4662 | 0x46AE | 0x47E1 | 0x47E5 | 0x47E6 | 0x5031 | 0x5032 |
            0x5033 | 0x535F | 0x5378 | 0x53AC | 0x53B8 | 0x53B9 | 0x53C0 |
            0x54AA | 0x54B0 | 0x54B2 | 0x54B3 | 0x54BA | 0x54BB | 0x54CC |
            0x54DD | 0x55AA | 0x55B1 | 0x55B2 | 0x55B3 | 0x55B4 | 0x55B5 |
            0x55B6 | 0x55B7 | 0x55B8 | 0x55B9 | 0x55BA | 0x55BB | 0x55BC |
            0x55BD | 0x55EE | 0x56AA | 0x56BB | 0x58D7 | 0x6264 | 0x63C3 |
            0x63C4 | 0x63C5 | 0x63C6 | 0x63C9 | 0x66BF | 0x66FC | 0x68CA |
            0x6922 | 0x6955 | 0x69BF | 0x69FC | 0x6DE7 | 0x6DF8 | 0x6EBC |
            0x6FAB | 0x73C4 | 0x73C5 | 0x7446 | 0x7E8A | 0x7E9A |
            0x234E7A | 0x23E383 | 0x2AD7B1 => {
                read_uint(r, size).map(|u| ElementType::UInt(u))
            }
            0x86 | 0x4282 | 0x437C | 0x437E | 0x447A | 0x4660 | 0x63CA |
            0x22B59C | 0x26B240 | 0x3B4040 => {
                read_string(r, size).map(|s| ElementType::String(s))
            }
            0x85 |
            0x4487 | 0x45A3 | 0x466E | 0x467E | 0x4D80 |
            0x536E | 0x5654 | 0x5741 | 0x7384 | 0x7BA9 |
            0x258688 | 0x3A9697 | 0x3C83AB | 0x3E83BB => {
                read_utf8(r, size).map(|u| ElementType::UTF8(u))
            }
            0xA1 | 0xA2 | 0xA3 | 0xA4 | 0xA5 |
            0xAF | 0xBF | 0xC1 | 0xC4 | 0xEC |
            0x4255 | 0x4444 | 0x4485 | 0x450D | 0x465C | 0x4675 | 0x47E2 |
            0x47E3 | 0x47E4 | 0x53AB | 0x63A2 | 0x6532 | 0x66A5 | 0x6933 |
            0x69A5 | 0x6E67 | 0x73A4 | 0x7D7B | 0x7EA5 | 0x7EB5 |
            0x2EB524 | 0x3CB923 | 0x3EB923 => {
                read_bin(r, size).map(|b| ElementType::Binary(b))
            }
            0xB5 | 0x4489 | 0x55D1 | 0x55D2 | 0x55D3 | 0x55D4 | 0x55D5 |
            0x55D6 | 0x55D7 | 0x55D8 | 0x55D9 | 0x55DA | 0x78B5 |
            0x23314F | 0x2383E3 | 0x2FB523 => {
                read_float(r, size).map(|f| ElementType::Float(f))
            }
            0x4461 => {
                read_date(r, size).map(|d| ElementType::Date(d))
            }
            _ => {
                read_bin(r, size).map(|b| ElementType::Binary(b))
            }
        }
    }

    pub fn parse_master(r: &mut io::Read, mut size: u64) ->
        Result<Vec<Element>,MatroskaError> {
        let mut elements = Vec::new();
        while size > 0 {
            let e = Element::parse(r)?;
            assert!(e.size <= size);
            size -= e.size;
            elements.push(e);
        }
        Ok(elements)
    }

}

#[derive(Debug)]
pub enum ElementType {
    Master(Vec<Element>),
    Int(i64),
    UInt(u64),
    String(String),
    UTF8(String),
    Binary(Vec<u8>),
    Float(f64),
    Date(DateTime<Utc>)
}

/// A possible error when parsing a Matroska file
#[derive(Debug)]
pub enum MatroskaError {
    /// An I/O error
    Io(io::Error),
    /// An error decoding a UTF-8 string
    UTF8(FromUtf8Error),
    /// An invalid element ID
    InvalidID,
    /// An invalid element size
    InvalidSize,
    /// An invalid unsigned integer
    InvalidUint,
    /// An invalid floating point value
    InvalidFloat,
    /// An invalid date value
    InvalidDate
}

pub fn read_element_id_size(reader: &mut io::Read) ->
    Result<(u32,u64,u64),MatroskaError> {
    let mut r = BitReader::<BE>::new(reader);
    let (id, id_len) = read_element_id(&mut r)?;
    let (size, size_len) = read_element_size(&mut r)?;
    Ok((id, size, id_len + size_len))
}

fn read_element_id(r: &mut BitReader<BE>) -> Result<(u32,u64),MatroskaError> {
    match r.read_unary1() {
        Ok(0) => {
            r.read::<u32>(7)
             .map_err(MatroskaError::Io)
             .map(|u| (0b10000000 | u, 1))
        }
        Ok(1) => {
            r.read::<u32>(6 + 8)
             .map_err(MatroskaError::Io)
             .map(|u| ((0b01000000 << 8) | u, 2))
        }
        Ok(2) => {
            r.read::<u32>(5 + 16)
             .map_err(MatroskaError::Io)
             .map(|u| ((0b00100000 << 16) | u, 3))
        }
        Ok(3) => {
            r.read::<u32>(4 + 24)
             .map_err(MatroskaError::Io)
             .map(|u| ((0b00010000 << 24) | u, 4))
        }
        Ok(_) => {Err(MatroskaError::InvalidID)}
        Err(err) => {Err(MatroskaError::Io(err))}
    }
}

fn read_element_size(r: &mut BitReader<BE>) -> Result<(u64,u64),MatroskaError> {
    match r.read_unary1() {
        Ok(0) => {r.read(7 + (0 * 8))
                   .map(|s| (s, 1))
                   .map_err(MatroskaError::Io)}
        Ok(1) => {r.read(6 + (1 * 8))
                   .map(|s| (s, 2))
                   .map_err(MatroskaError::Io)}
        Ok(2) => {r.read(5 + (2 * 8))
                   .map(|s| (s, 3))
                   .map_err(MatroskaError::Io)}
        Ok(3) => {r.read(4 + (3 * 8))
                   .map(|s| (s, 4))
                   .map_err(MatroskaError::Io)}
        Ok(4) => {r.read(3 + (4 * 8))
                   .map(|s| (s, 5))
                   .map_err(MatroskaError::Io)}
        Ok(5) => {r.read(2 + (5 * 8))
                   .map(|s| (s, 6))
                   .map_err(MatroskaError::Io)}
        Ok(6) => {r.read(1 + (6 * 8))
                   .map(|s| (s, 7))
                   .map_err(MatroskaError::Io)}
        Ok(7) => {r.read(0 + (7 * 8))
                   .map(|s| (s, 8))
                   .map_err(MatroskaError::Io)}
        Ok(_) => {Err(MatroskaError::InvalidSize)}
        Err(err) => {Err(MatroskaError::Io(err))}
    }
}

pub fn read_int(r: &mut io::Read, size: u64) -> Result<i64,MatroskaError> {
    let mut r = BitReader::<BE>::new(r);
    match size {
        0 => {Ok(0)}
        s @ 1...8 => {r.read_signed(s as u32 * 8).map_err(MatroskaError::Io)}
        _ => {Err(MatroskaError::InvalidUint)}
    }
}

pub fn read_uint(r: &mut io::Read, size: u64) -> Result<u64,MatroskaError> {
    let mut r = BitReader::<BE>::new(r);
    match size {
        0 => {Ok(0)}
        s @ 1...8 => {r.read(s as u32 * 8).map_err(MatroskaError::Io)}
        _ => {Err(MatroskaError::InvalidUint)}
    }
}

pub fn read_float(r: &mut io::Read, size: u64) -> Result<f64,MatroskaError> {
    use std::mem;

    let mut r = BitReader::<BE>::new(r);
    match size {
        4 => {
            let i: u32 = r.read(32).map_err(MatroskaError::Io)?;
            let f: f32 = unsafe {mem::transmute(i)};
            Ok(f as f64)
        }
        8 => {
            let i: u64 = r.read(64).map_err(MatroskaError::Io)?;
            let f: f64 = unsafe {mem::transmute(i)};
            Ok(f)
        }
        _ => {Err(MatroskaError::InvalidFloat)}
    }
}

pub fn read_string(r: &mut io::Read, size: u64) ->
    Result<String,MatroskaError> {
    /*FIXME - limit this to ASCII set*/
    read_bin(r, size).and_then(
        |bytes| String::from_utf8(bytes).map_err(MatroskaError::UTF8))
}

pub fn read_utf8(r: &mut io::Read, size: u64) ->
    Result<String,MatroskaError> {
    read_bin(r, size).and_then(
        |bytes| String::from_utf8(bytes).map_err(MatroskaError::UTF8))
}

pub fn read_date(r: &mut io::Read, size: u64) ->
    Result<DateTime<Utc>,MatroskaError> {
    if size == 8 {
        use chrono::Duration;
        use chrono::TimeZone;

        read_int(r, size)
        .map(|d|
            Utc.ymd(2001, 1, 1)
               .and_hms(0, 0, 0) + Duration::nanoseconds(d))
    } else {
        Err(MatroskaError::InvalidDate)
    }
}

pub fn read_bin(r: &mut io::Read, size: u64) -> Result<Vec<u8>,MatroskaError> {
    /*FIXME - need to read this in chunks*/
    let mut buf = Vec::with_capacity(size as usize);
    buf.resize(size as usize, 0);
    r.read_exact(&mut buf).map(|()| buf).map_err(MatroskaError::Io)
}