use std::io::{Read, Seek, SeekFrom, Write};

use super::*;

/// An enum representing the different types of content an atom might have.
#[derive(Clone, Debug, Eq, PartialEq)]
pub(super) enum Content<'a> {
    /// A value containing a list of children atoms.
    Atoms(Vec<Atom<'a>>),
    /// A value containing a list of children atoms.
    AtomDataRef(&'a [AtomData]),
    /// A value containing raw data.
    RawData(Data),
    /// A value containing data defined by a
    /// [Table 3-5 Well-known data types](https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/Metadata/Metadata.html#//apple_ref/doc/uid/TP40000939-CH1-SW34)
    /// code.
    TypedData(Data),
    /// A value containing mp4 audio information.
    Mp4Audio(Mp4aInfo),
    /// A value containing mp4 audio information.
    MovieHeader(MvhdInfo),
    /// Empty content.
    Empty,
}

impl Default for Content<'_> {
    fn default() -> Self {
        Self::Empty
    }
}

impl<'a> Content<'a> {
    /// Creates new content of type [`Self::Atoms`] containing the atom.
    pub fn atom(atom: Atom<'a>) -> Self {
        Self::Atoms(vec![atom])
    }

    /// Creates new content of type [`Self::Atoms`] containing a data [`Atom`] with the data.
    pub fn data_atom_with(data: Data) -> Self {
        Self::atom(Atom::data_atom_with(data))
    }

    /// Returns the length in bytes.
    pub fn len(&self) -> u64 {
        match self {
            Self::Atoms(v) => v.iter().map(|a| a.len()).sum(),
            Self::AtomDataRef(v) => v.iter().map(|a| a.len()).sum(),
            Self::RawData(d) => d.len(),
            Self::TypedData(d) => 8 + d.len(),
            Self::Mp4Audio(_) => 0,
            Self::MovieHeader(_) => 0,
            Self::Empty => 0,
        }
    }

    /// Returns an iterator over the children atoms.
    pub fn atoms(&self) -> impl Iterator<Item = &Atom<'a>> {
        match self {
            Self::Atoms(v) => v.iter(),
            _ => [].iter(),
        }
    }

    pub fn into_atoms(self) -> impl Iterator<Item = Atom<'a>> {
        match self {
            Self::Atoms(v) => v.into_iter(),
            _ => Vec::new().into_iter(),
        }
    }

    /// Returns a reference to the first children atom matching the identifier, if present.
    pub fn child(&self, ident: Fourcc) -> Option<&Atom<'a>> {
        self.atoms().find(|a| a.ident == ident)
    }

    /// Consumes self and returns the first children atom matching the identifier, if present.
    pub fn take_child(self, ident: Fourcc) -> Option<Atom<'a>> {
        self.into_atoms().find(|a| a.ident == ident)
    }

    /// Return a data reference if `self` is of type [`Self::RawData`] or [`Self::TypedData`].
    pub fn data(&self) -> Option<&Data> {
        match self {
            Self::TypedData(d) => Some(d),
            Self::RawData(d) => Some(d),
            _ => None,
        }
    }

    /// Consumes self and returns data if `self` is of type [`Self::RawData`] or [`Self::TypedData`].
    pub fn take_data(self) -> Option<Data> {
        match self {
            Self::TypedData(d) => Some(d),
            Self::RawData(d) => Some(d),
            _ => None,
        }
    }

    /// Attempts to write the content to the writer.
    pub fn write_to(&self, writer: &mut impl Write) -> crate::Result<()> {
        match self {
            Self::Atoms(v) => {
                for a in v {
                    a.write_to(writer)?;
                }
            }
            Self::AtomDataRef(v) => {
                for a in *v {
                    a.write_to(writer)?;
                }
            }
            Self::RawData(d) => d.write_raw(writer)?,
            Self::TypedData(d) => d.write_typed(writer)?,
            Self::Mp4Audio(_) => {
                return Err(crate::Error::new(
                    crate::ErrorKind::UnwritableData,
                    "Mp4 audio information cannot be written".to_owned(),
                ))
            }
            Self::MovieHeader(_) => {
                return Err(crate::Error::new(
                    crate::ErrorKind::UnwritableData,
                    "Movie header information cannot be written".to_owned(),
                ))
            }
            Self::Empty => (),
        }

        Ok(())
    }
}

/// A template representing the different types of content an atom template might have.
#[derive(Clone, Debug, Eq, PartialEq)]
pub(super) enum ContentT {
    /// A value containing a list of children atom templates.
    Atoms(Vec<AtomT>),
    /// A template for raw data containing a datatype definded by
    /// [Table 3-5 Well-known data types](https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/Metadata/Metadata.html#//apple_ref/doc/uid/TP40000939-CH1-SW34)
    RawData(u32),
    /// A template representing typed data that is defined by a
    /// [Table 3-5 Well-known data types](https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/Metadata/Metadata.html#//apple_ref/doc/uid/TP40000939-CH1-SW34)
    /// code prior to the data parsed.
    TypedData,
    /// A template representing mp4 audio information.
    Mp4Audio,
    /// A template representing movie header information.
    MovieHeader,
    /// A template for ignoring all data inside.
    Ignore,
    /// Empty content.
    Empty,
}

impl Default for ContentT {
    fn default() -> Self {
        Self::Empty
    }
}

impl ContentT {
    /// Creates a new empty content template of type [`Self::Atoms`].
    pub const fn atoms_t() -> Self {
        Self::Atoms(Vec::new())
    }

    /// Creates a new content template of type [`Self::Atoms`] containing the atom template.
    pub fn atom_t(atom: AtomT) -> Self {
        Self::Atoms(vec![atom])
    }

    /// Attempts to parse corresponding content from the reader.
    pub fn parse<'a>(
        &self,
        reader: &mut (impl Read + Seek),
        len: u64,
    ) -> crate::Result<Content<'a>> {
        Ok(match self {
            Self::Atoms(v) => Content::Atoms(parse_atoms(reader, v, len)?),
            Self::RawData(d) => Content::RawData(data::parse_data(reader, *d, len)?),
            Self::TypedData => {
                if len >= 8 {
                    let datatype = match data::read_u32(reader) {
                        Ok(d) => d,
                        Err(e) => {
                            return Err(crate::Error::new(
                                e.kind,
                                "Error reading typed data head".to_owned(),
                            ));
                        }
                    };

                    // Skipping 4 byte locale indicator
                    reader.seek(SeekFrom::Current(4))?;

                    Content::TypedData(data::parse_data(reader, datatype, len - 8)?)
                } else {
                    return Err(crate::Error::new(
                        ErrorKind::Parsing,
                        "Typed data head to short".to_owned(),
                    ));
                }
            }
            Self::Mp4Audio => Content::Mp4Audio(Mp4aInfo::parse(reader, len)?),
            Self::MovieHeader => Content::MovieHeader(MvhdInfo::parse(reader, len)?),
            Self::Ignore => {
                reader.seek(SeekFrom::Current(len as i64))?;
                Content::Empty
            }
            Self::Empty => {
                if len != 0 {
                    return Err(crate::Error::new(
                        crate::ErrorKind::Parsing,
                        format!("Expected empty content found content of length: {}", len),
                    ));
                }
                Content::Empty
            }
        })
    }
}