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use dicom_core::value::C;
use snafu::Snafu;

pub mod rle_lossless;

#[derive(Debug, Snafu)]
#[non_exhaustive]
pub enum DecodeError {
    /// A custom error when decoding fails
    #[snafu(display("Error decoding pixel data: {}", message))]
    CustomDecodeError { message: &'static str },

    /// A required attribute is missing from the DICOM
    #[snafu(display("Missing required attribute: {}", name))]
    MissingAttribute { name: &'static str },
}

#[derive(Debug, Snafu)]
#[non_exhaustive]
pub enum EncodeError {
    /// A custom error when encoding fails
    #[snafu(display("Error encoding pixel data {}", message))]
    CustomEncodeError {
        message: &'static str,
    },

    NotImplementedError,
}

pub type DecodeResult<T, E = DecodeError> = Result<T, E>;

pub type EncodeResult<T, E = EncodeError> = Result<T, E>;

#[derive(Debug)]
pub struct RawPixelData {
    /// Either a byte slice/vector if native pixel data
    /// or byte fragments if encapsulated
    pub fragments: C<Vec<u8>>,

    /// The offset table for the fragments,
    /// or empty if there is none
    pub offset_table: C<u32>,
}

/// PixelDataObject trait contains all
/// relevant data to decode pixel data
pub trait PixelDataObject {
    /// Return the Rows attribute or None if it is not found
    fn rows(&self) -> Option<u16>;

    /// Return the Columns attribute or None if it is not found
    fn cols(&self) -> Option<u16>;

    /// Return the SamplesPerPixel attribute or None if it is not found
    fn samples_per_pixel(&self) -> Option<u16>;

    /// Return the BitsAllocated attribute or None if it is not set
    fn bits_allocated(&self) -> Option<u16>;

    /// Return the NumberOfFrames attribute or None if it is not set
    fn number_of_frames(&self) -> Option<u16>;

    /// Returns the number of fragments or None for native pixel data
    fn number_of_fragments(&self) -> Option<u32>;

    /// Return a specific encoded pixel fragment by index as Vec<u8>
    /// or None if no pixel data is found
    fn fragment(&self, fragment: usize) -> Option<Vec<u8>>;

    /// Should return either a byte slice/vector if native pixel data
    /// or byte fragments if encapsulated.
    /// Returns None if no pixel data is found
    fn raw_pixel_data(&self) -> Option<RawPixelData>;
}

/// Trait object responsible for decoding and encoding
/// pixel data based on the Transfersyntax.
/// Every TS with encapsulated pixel data should implement this.
pub trait PixelRWAdapter {
    /// Decode complete byte stream to native pixel data
    fn decode(&self, src: &dyn PixelDataObject, dst: &mut Vec<u8>) -> DecodeResult<()>;

    /// Write byte stream
    fn encode(&self, src: &[u8], dst: &mut Vec<u8>) -> EncodeResult<()>;
}

/// Alias type for a dynamically dispatched data adapter.
pub type DynPixelRWAdapter = Box<dyn PixelRWAdapter + Send + Sync>;

/// An immaterial type representing an adapter which is never required.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum NeverPixelAdapter {}

impl PixelRWAdapter for NeverPixelAdapter {
    fn decode(&self, _src: &dyn PixelDataObject, _dst: &mut Vec<u8>) -> DecodeResult<()> {
        unreachable!();
    }

    fn encode(&self, _src: &[u8], _dst: &mut Vec<u8>) -> EncodeResult<()> {
        unreachable!();
    }
}