//! A simple way to specify the sizes or offsets of up to three dimensions.
use std::convert::From;
use std::fmt::Debug;
use std::ops::Index;
use num_traits::{Num, ToPrimitive};
use error::{Result as OclResult};
use standard::{MemLen, WorkDims};
use core::util;


#[derive(Debug, Fail)]
#[fail(display = "Cannot convert to a valid set of dimensions. \
    Please specify some dimensions.")]
pub struct UnspecifiedDimensionsError;


/// Specifies a size or offset in up to three dimensions.
///
/// Using `SpatialDims` to specify dimensions for your application may not be
/// appropriate. Custom types implementing the traits `MemLen` and `WorkDims`
/// should be created to express more complex relationships between data shape
/// and work size for kernels which do not have a 1:1 correspondence between
/// data set length and global work size.
///
/// [FIXME]: Describe the ways a `SpatialDims` can be created using various
/// `From` implementations.
///
/// [UNSTABLE]: This type and its methods may be renamed or otherwise changed
/// at any time. This is still a work in progress.
///
#[derive(Clone, Debug, Copy, PartialEq, Eq)]
pub enum SpatialDims {
    Unspecified,
    One     (usize),
    Two     (usize, usize),
    Three   (usize, usize, usize),
}

impl SpatialDims {
    /// Returns a new `SpatialDims`.
    ///
    /// Dimensions must be specified in order from d0 -> d1 -> d2; i.e. `d1`
    /// cannot be `Some(x)` if `d0` is `None`.
    ///
    /// Explicitly setting all zeros as values is not recommended as it is
    /// invalid to OpenCL functions. Use `::Unspecified` to represent `NULL`
    /// instead.
    ///
    pub fn new(d0: Option<usize>, d1: Option<usize>, d2: Option<usize>) -> OclResult<SpatialDims> {
        let std_err_msg = "Dimensions must be defined from left to right. If you define the 2nd \
            dimension, you must also define the 1st, etc.";

        if d2.is_some() {
            if d1.is_some() && d0.is_some() {
                Ok(SpatialDims::Three(d0.unwrap(), d1.unwrap(), d2.unwrap()))
            } else {
                Err(std_err_msg.into())
            }
        } else if d1.is_some() {
            if d0.is_some() {
                Ok(SpatialDims::Two(d1.unwrap(), d0.unwrap()))
            } else {
                Err(std_err_msg.into())
            }
        } else if d0.is_some() {
            Ok(SpatialDims::One(d0.unwrap()))
        } else {
            Ok(SpatialDims::Unspecified)
        }
    }

    /// Returns the number of dimensions defined by this `SpatialDims`.
    pub fn dim_count(&self) -> u32 {
        match *self {
            SpatialDims::Unspecified => 0,
            SpatialDims::One(..) => 1,
            SpatialDims::Two(..) => 2,
            SpatialDims::Three(..) => 3,
        }
    }

    /// Returns a 3D size or an error if unspecified.
    pub fn to_lens(&self) -> Result<[usize; 3], UnspecifiedDimensionsError> {
        match *self {
            SpatialDims::Unspecified => Err(UnspecifiedDimensionsError),
            SpatialDims::One(x) => Ok([x, 1, 1]),
            SpatialDims::Two(x, y) => Ok([x, y, 1]),
            SpatialDims::Three(x, y, z) => Ok([x, y, z]),
        }
    }

    /// Returns a 3D offset or an error if unspecified.
    pub fn to_offset(&self) -> Result<[usize; 3], UnspecifiedDimensionsError> {
        match *self {
            SpatialDims::Unspecified => Err(UnspecifiedDimensionsError),
            SpatialDims::One(x) => Ok([x, 0, 0]),
            SpatialDims::Two(x, y) => Ok([x, y, 0]),
            SpatialDims::Three(x, y, z) => Ok([x, y, z]),
        }
    }

    /// Returns the product of all contained dimensional values (equivalent to
    /// a length, area, or volume) or zero if unspecified.
    ///
    /// Check `::is_unspecified` if it matters whether or not the zero length
    /// has been explicitly set however, explicitly setting all zeros as
    /// dimensions is not recommended as it is an invalid value to OpenCL
    /// functions. Use `::Unspecified` to represent `NULL` instead.
    ///
    pub fn to_len(&self) -> usize {
        match *self {
            SpatialDims::Unspecified => 0,
            SpatialDims::Three(d0, d1, d2) => d0 * d1 * d2,
            SpatialDims::Two(d0, d1) => d0 * d1,
            SpatialDims::One(d0) => d0,
        }
    }

    /// Takes the length and rounds it up to the nearest `incr` or an error.
    pub fn try_to_padded_len(&self, incr: usize) -> OclResult<usize> {
        Ok(util::padded_len(self.to_len(), incr))
    }

    /// Returns `true` if this `SpatialDims` is an `Unspecified` variant.
    pub fn is_unspecified(&self) -> bool {
        if let SpatialDims::Unspecified = *self { true } else { false }
    }
}

impl MemLen for SpatialDims {
    fn to_len_padded(&self, incr: usize) -> usize {
        self.try_to_padded_len(incr).expect("ocl::SpatialDims::to_len_padded()")
    }

    fn to_len(&self) -> usize {
        self.to_len()
    }

    fn to_lens(&self) -> [usize; 3] {
        self.to_lens().expect("SpatialDims::<MemLen>::to_lens()")
    }
}

impl WorkDims for SpatialDims {
    fn dim_count(&self) -> u32 {
        self.dim_count()
    }

    fn to_work_size(&self) -> Option<[usize; 3]> {
        self.to_lens().ok()
    }

    fn to_work_offset(&self) -> Option<[usize; 3]> {
        self.to_offset().ok()
    }
}


impl Index<usize> for SpatialDims {
    type Output = usize;

    fn index(&self, index: usize) -> &usize {
        match *self {
            SpatialDims::Unspecified => panic!("ocl::SpatialDims::index(): \
                Cannot index. No dimensions have been specified."),
            SpatialDims::One(ref x) => {
                assert!(index == 0, "ocl::SpatialDims::index(): Index: [{}], out of range. \
                    Only one dimension avaliable.", index);
                x
            },
            SpatialDims::Two(ref x, ref y) => {
                match index {
                    0 => x,
                    1 => y,
                    _ => panic!("ocl::SpatialDims::index(): Index: [{}], out of range. \
                    Only two dimensions avaliable.", index),
                }
            },
            SpatialDims::Three(ref x, ref y, ref z) => {
                match index {
                    0 => x,
                    1 => y,
                    2 => z,
                    _ => panic!("ocl::SpatialDims::index(): Index: [{}], out of range. \
                    Only three dimensions avaliable.", index),
                }
            },
        }
    }
}

impl<'a> From<&'a SpatialDims> for SpatialDims {
    fn from(sd: &'a SpatialDims) -> SpatialDims {
        sd.clone()
    }
}

// [FIXME]: Quit being lazy and implement FromPrimitive.
impl From<usize> for SpatialDims {
    fn from(val: usize) -> SpatialDims {
        SpatialDims::One(val)
    }
}

// [FIXME]: Quit being lazy and implement FromPrimitive.
impl From<isize> for SpatialDims {
    fn from(val: isize) -> SpatialDims {
        assert!(val > 0, "Invalid 'SpatialDims' value: {}. \
            Dimensions must be greater than zero.", val);
        (val as usize).into()
    }
}

// [FIXME]: Quit being lazy and implement FromPrimitive.
impl From<u32> for SpatialDims {
    fn from(val: u32) -> SpatialDims {
        (val as usize).into()
    }
}

// [FIXME]: Quit being lazy and implement FromPrimitive.
impl From<i32> for SpatialDims {
    fn from(val: i32) -> SpatialDims {
        (val as isize).into()
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<(T, )> for SpatialDims {
    fn from(val: (T, )) -> SpatialDims {
        SpatialDims::One(to_usize(val.0))
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a (T, )> for SpatialDims {
    fn from(val: &(T, )) -> SpatialDims {
        SpatialDims::One(to_usize(val.0))
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<[T; 1]> for SpatialDims {
    fn from(val: [T; 1]) -> SpatialDims {
        SpatialDims::One(to_usize(val[0]))
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a [T; 1]> for SpatialDims {
    fn from(val: &[T; 1]) -> SpatialDims {
        SpatialDims::One(to_usize(val[0]))
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<(T, T)> for SpatialDims {
    fn from(pair: (T, T)) -> SpatialDims {
        SpatialDims::Two(
            to_usize(pair.0),
            to_usize(pair.1),
        )
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a (T, T)> for SpatialDims {
    fn from(pair: &(T, T)) -> SpatialDims {
        SpatialDims::Two(
            to_usize(pair.0),
            to_usize(pair.1),
        )
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<[T; 2]> for SpatialDims {
    fn from(pair: [T; 2]) -> SpatialDims {
        SpatialDims::Two(
            to_usize(pair[0]),
            to_usize(pair[1]),
        )
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a [T; 2]> for SpatialDims {
    fn from(pair: &[T; 2]) -> SpatialDims {
        SpatialDims::Two(
            to_usize(pair[0]),
            to_usize(pair[1]),
        )
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<(T, T, T)> for SpatialDims {
    fn from(set: (T, T, T)) -> SpatialDims {
        SpatialDims::Three(
            to_usize(set.0),
            to_usize(set.1),
            to_usize(set.2),
        )
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a (T, T, T)> for SpatialDims {
    fn from(set: &(T, T, T)) -> SpatialDims {
        SpatialDims::Three(
            to_usize(set.0),
            to_usize(set.1),
            to_usize(set.2),
        )
    }
}

impl<T: Num + ToPrimitive + Debug + Copy> From<[T; 3]> for SpatialDims {
    fn from(set: [T; 3]) -> SpatialDims {
        SpatialDims::Three(
            to_usize(set[0]),
            to_usize(set[1]),
            to_usize(set[2]),
        )
    }
}

impl<'a, T: Num + ToPrimitive + Debug + Copy> From<&'a [T; 3]> for SpatialDims {
    fn from(set: &[T; 3]) -> SpatialDims {
        SpatialDims::Three(
            to_usize(set[0]),
            to_usize(set[1]),
            to_usize(set[2]),
        )
    }
}


#[inline]
pub fn to_usize<T: Num + ToPrimitive + Debug + Copy>(val: T) -> usize {
    val.to_usize().expect(&format!("Unable to convert the value '{:?}' into a 'SpatialDims'. \
        Dimensions must have positive values.", val))
}