// Copyright 2021-2023 Colin Finck <colin@reactos.org>
// SPDX-License-Identifier: MIT OR Apache-2.0
//
//! Readers for attribute value types.

mod attribute_list_non_resident;
mod non_resident;
mod resident;

pub use attribute_list_non_resident::*;
pub use non_resident::*;
pub use resident::*;

use binrw::io;
use binrw::io::{Read, Seek, SeekFrom};

use crate::error::{NtfsError, Result};
use crate::traits::NtfsReadSeek;
use crate::types::NtfsPosition;

/// Reader that abstracts over all attribute value types, returned by [`NtfsAttribute::value`].
///
/// [`NtfsAttribute::value`]: crate::NtfsAttribute::value
#[allow(clippy::large_enum_variant)]
#[derive(Clone, Debug)]
pub enum NtfsAttributeValue<'n, 'f> {
    /// A resident attribute value (which is entirely contained in the NTFS File Record).
    Resident(NtfsResidentAttributeValue<'f>),
    /// A non-resident attribute value (whose data is in a cluster range outside the File Record).
    NonResident(NtfsNonResidentAttributeValue<'n, 'f>),
    /// A non-resident attribute value that is part of an Attribute List (and may span multiple connected attributes).
    AttributeListNonResident(NtfsAttributeListNonResidentAttributeValue<'n, 'f>),
}

impl<'n, 'f> NtfsAttributeValue<'n, 'f> {
    /// Returns a variant of this reader that implements [`Read`] and [`Seek`]
    /// by mutably borrowing the filesystem reader.
    pub fn attach<'a, T>(self, fs: &'a mut T) -> NtfsAttributeValueAttached<'n, 'f, 'a, T>
    where
        T: Read + Seek,
    {
        NtfsAttributeValueAttached::new(fs, self)
    }

    /// Returns the absolute current data seek position within the filesystem, in bytes.
    /// This may be `None` if:
    ///   * The current seek position is outside the valid range, or
    ///   * The attribute does not have a Data Run, or
    ///   * The current Data Run is a "sparse" Data Run.
    pub fn data_position(&self) -> NtfsPosition {
        match self {
            Self::Resident(inner) => inner.data_position(),
            Self::NonResident(inner) => inner.data_position(),
            Self::AttributeListNonResident(inner) => inner.data_position(),
        }
    }

    /// Returns `true` if the attribute value contains no data.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Returns the total length of the attribute value data, in bytes.
    pub fn len(&self) -> u64 {
        match self {
            Self::Resident(inner) => inner.len(),
            Self::NonResident(inner) => inner.len(),
            Self::AttributeListNonResident(inner) => inner.len(),
        }
    }
}

impl<'n, 'f> NtfsReadSeek for NtfsAttributeValue<'n, 'f> {
    fn read<T>(&mut self, fs: &mut T, buf: &mut [u8]) -> Result<usize>
    where
        T: Read + Seek,
    {
        match self {
            Self::Resident(inner) => inner.read(fs, buf),
            Self::NonResident(inner) => inner.read(fs, buf),
            Self::AttributeListNonResident(inner) => inner.read(fs, buf),
        }
    }

    fn seek<T>(&mut self, fs: &mut T, pos: SeekFrom) -> Result<u64>
    where
        T: Read + Seek,
    {
        match self {
            Self::Resident(inner) => inner.seek(fs, pos),
            Self::NonResident(inner) => inner.seek(fs, pos),
            Self::AttributeListNonResident(inner) => inner.seek(fs, pos),
        }
    }

    fn stream_position(&self) -> u64 {
        match self {
            Self::Resident(inner) => inner.stream_position(),
            Self::NonResident(inner) => inner.stream_position(),
            Self::AttributeListNonResident(inner) => inner.stream_position(),
        }
    }
}

/// A variant of [`NtfsAttributeValue`] that implements [`Read`] and [`Seek`]
/// by mutably borrowing the filesystem reader.
#[derive(Debug)]
pub struct NtfsAttributeValueAttached<'n, 'f, 'a, T: Read + Seek> {
    fs: &'a mut T,
    value: NtfsAttributeValue<'n, 'f>,
}

impl<'n, 'f, 'a, T> NtfsAttributeValueAttached<'n, 'f, 'a, T>
where
    T: Read + Seek,
{
    fn new(fs: &'a mut T, value: NtfsAttributeValue<'n, 'f>) -> Self {
        Self { fs, value }
    }

    /// Returns the absolute current data seek position within the filesystem, in bytes.
    /// This may be `None` if:
    ///   * The current seek position is outside the valid range, or
    ///   * The attribute does not have a Data Run, or
    ///   * The current Data Run is a "sparse" Data Run.
    pub fn data_position(&self) -> NtfsPosition {
        self.value.data_position()
    }

    /// Consumes this reader and returns the inner [`NtfsAttributeValue`].
    pub fn detach(self) -> NtfsAttributeValue<'n, 'f> {
        self.value
    }

    /// Returns `true` if the attribute value contains no data.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Returns the total length of the attribute value, in bytes.
    pub fn len(&self) -> u64 {
        self.value.len()
    }
}

impl<'n, 'f, 'a, T> Read for NtfsAttributeValueAttached<'n, 'f, 'a, T>
where
    T: Read + Seek,
{
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.value.read(self.fs, buf).map_err(io::Error::from)
    }
}

impl<'n, 'f, 'a, T> Seek for NtfsAttributeValueAttached<'n, 'f, 'a, T>
where
    T: Read + Seek,
{
    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
        self.value.seek(self.fs, pos).map_err(io::Error::from)
    }
}

pub(crate) fn seek_contiguous(
    stream_position: &mut u64,
    length: u64,
    pos: SeekFrom,
) -> Result<u64> {
    // This implementation is taken from https://github.com/rust-lang/rust/blob/18c524fbae3ab1bf6ed9196168d8c68fc6aec61a/library/std/src/io/cursor.rs
    // It handles all signed/unsigned arithmetics properly and outputs the known `io` error message.
    let (base_pos, offset) = match pos {
        SeekFrom::Start(n) => {
            *stream_position = n;
            return Ok(n);
        }
        SeekFrom::End(n) => (length, n),
        SeekFrom::Current(n) => (*stream_position, n),
    };

    let new_pos = if offset >= 0 {
        base_pos.checked_add(offset as u64)
    } else {
        base_pos.checked_sub(offset.wrapping_neg() as u64)
    };

    match new_pos {
        Some(n) => {
            *stream_position = n;
            Ok(*stream_position)
        }
        None => Err(NtfsError::Io(io::Error::new(
            io::ErrorKind::InvalidInput,
            "invalid seek to a negative or overflowing position",
        ))),
    }
}