morok-ir 0.1.0-alpha.2

//! Shape manipulation: reshape, permute, expand, pad, shrink, flip.
//!
//! These operations manipulate tensor shapes and layouts without changing
//! the underlying data (except for padding which may add values).

use std::sync::Arc;

use crate::Result;
use crate::op::Op;
use crate::uop::UOp;

// Low-level constructors (pub(crate) - not yet used but will be needed for optimization passes)
#[allow(dead_code)]
impl UOp {
    /// Reshape tensor to new shape (low-level, UOp-based constructor).
    ///
    /// Takes a UOp for the shape parameter (used internally by compiler passes).
    /// For the public API with validation, use `try_reshape`.
    pub(crate) fn reshape(src: Arc<Self>, new_shape: Arc<Self>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Reshape { src, new_shape }, dtype)
    }

    /// Permute dimensions (low-level, UOp-based constructor).
    ///
    /// For the public API with validation, use `try_permute`.
    pub(crate) fn permute(src: Arc<Self>, axes: Vec<usize>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Permute { src, axes }, dtype)
    }

    /// Expand (broadcast) dimensions (low-level, UOp-based constructor).
    ///
    /// Takes a UOp for the shape parameter (used internally by compiler passes).
    /// For the public API with validation, use `try_expand`.
    pub(crate) fn expand(src: Arc<Self>, new_shape: Arc<Self>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Expand { src, new_shape }, dtype)
    }

    /// Pad tensor (low-level, UOp-based constructor).
    ///
    /// Takes UOps for padding parameters (used internally by compiler passes).
    /// For the public API with validation, use `try_pad`.
    pub(crate) fn pad(src: Arc<Self>, begin_pads: Arc<Self>, end_pads: Arc<Self>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Pad { src, begin_pads, end_pads }, dtype)
    }

    /// Shrink (slice) tensor (low-level, UOp-based constructor).
    ///
    /// Takes UOps for range parameters (used internally by compiler passes).
    /// For the public API with validation, use `try_shrink`.
    pub(crate) fn shrink(src: Arc<Self>, begins: Arc<Self>, ends: Arc<Self>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Shrink { src, begins, ends }, dtype)
    }

    /// Flip (reverse) axes (low-level, UOp-based constructor).
    ///
    /// For the public API with validation, use `try_flip`.
    pub(crate) fn flip(src: Arc<Self>, axes: Vec<bool>) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Flip { src, axes }, dtype)
    }
}

// Primary Movement Operation Constructors (with validation)
impl UOp {
    /// Reshape with strict validation (fail-fast).
    ///
    /// Validates:
    /// - No negative dimensions in new_shape
    /// - Product of input shape == product of output shape
    pub fn try_reshape(self: &Arc<Self>, new_shape: &crate::shape::Shape) -> Result<Arc<Self>> {
        use crate::error::ReshapeSizeMismatchSnafu;
        use crate::shape::shape_to_uop;
        use snafu::ensure;

        // Validate product equality if source shape is known
        if let Some(src_shape) = self.shape()? {
            // Identity reshape: skip if shapes already match.
            // Exclude BUFFER and CONST: the rangeify pipeline requires RESHAPE(BUFFER) to
            // generate INDEX operations for ASSIGN targets. Bare BUFFER can't be indexed.
            // Tinygrad avoids this because their BUFFER carries shape natively and their
            // rangeify handles bare BUFFER → INDEX directly.
            if src_shape.as_slice() == new_shape.as_slice()
                && !matches!(self.op(), crate::Op::Buffer { .. } | crate::Op::Param { .. } | crate::Op::Const(_))
            {
                return Ok(self.clone());
            }

            let src_product = crate::sint_prod(src_shape);
            let dst_product = crate::sint_prod(new_shape);

            // If both are concrete, validate equality
            if let (Some(src_prod), Some(dst_prod)) = (src_product.as_const(), dst_product.as_const()) {
                ensure!(src_prod == dst_prod, ReshapeSizeMismatchSnafu { input_size: src_prod, output_size: dst_prod });
            }
            // Symbolic products can't be validated at compile time
        }

        let shape_uop = shape_to_uop(new_shape);
        let dtype = self.dtype();
        Ok(Self::new(Op::Reshape { src: self.clone(), new_shape: shape_uop }, dtype))
    }

    /// Expand (broadcast) with strict validation.
    ///
    /// Validates:
    /// - Number of dimensions matches
    /// - Each dimension either matches or src dimension is 1
    pub fn try_expand(self: &Arc<Self>, new_shape: &crate::shape::Shape) -> Result<Arc<Self>> {
        use crate::error::ExpandDimensionMismatchSnafu;
        use crate::error::ExpandInvalidDimensionSnafu;
        use crate::shape::shape_to_uop;
        use snafu::ensure;

        if let Some(src_shape) = self.shape()? {
            // Check dimension count
            ensure!(
                src_shape.len() == new_shape.len(),
                ExpandDimensionMismatchSnafu { input_dims: src_shape.len(), output_dims: new_shape.len() }
            );

            // Check each dimension can be expanded
            for (dim_idx, (src_dim, new_dim)) in src_shape.iter().zip(new_shape.iter()).enumerate() {
                // If both are concrete, validate expand rule
                if let (Some(s), Some(ns)) = (src_dim.as_const(), new_dim.as_const()) {
                    ensure!(s == ns || s == 1, ExpandInvalidDimensionSnafu { dim: dim_idx, input: s, output: ns });
                }
                // Symbolic dimensions assumed compatible
            }

            // Identity expand: skip if shapes already match
            if src_shape.as_slice() == new_shape.as_slice() {
                return Ok(self.clone());
            }
        }

        let shape_uop = shape_to_uop(new_shape);
        let dtype = self.dtype();
        Ok(Self::new(Op::Expand { src: self.clone(), new_shape: shape_uop }, dtype))
    }

    /// Permute with strict validation.
    ///
    /// Validates:
    /// - Permutation is valid (contains each index 0..n exactly once)
    pub fn try_permute(self: &Arc<Self>, axes: Vec<usize>) -> Result<Arc<Self>> {
        // Validate permutation if source shape is known
        if let Some(src_shape) = self.shape()? {
            Self::validate_permutation(&axes, src_shape.len())?;

            // Identity permute: skip if axes is [0, 1, 2, ..., n-1]
            if axes.iter().enumerate().all(|(i, &a)| a == i) {
                return Ok(self.clone());
            }
        }

        let dtype = self.dtype();
        Ok(Self::new(Op::Permute { src: self.clone(), axes }, dtype))
    }

    /// Pad with strict validation.
    ///
    /// Validates:
    /// - Padding values are concrete (not symbolic)
    /// - Number of padding pairs matches dimensions
    pub fn try_pad(self: &Arc<Self>, padding: &[(crate::SInt, crate::SInt)]) -> Result<Arc<Self>> {
        use crate::error::{PadDimensionMismatchSnafu, SymbolicPaddingUnsupportedSnafu};
        use crate::shape::ranges_to_uops;
        use snafu::ensure;

        // Empty padding (scalar) → identity
        if padding.is_empty() {
            return Ok(self.clone());
        }

        // Check for symbolic padding values
        for (begin, end) in padding {
            ensure!(begin.is_const(), SymbolicPaddingUnsupportedSnafu);
            ensure!(end.is_const(), SymbolicPaddingUnsupportedSnafu);
        }

        // All-zero padding: no-op
        if padding.iter().all(|(b, e)| b.as_const() == Some(0) && e.as_const() == Some(0)) {
            return Ok(self.clone());
        }

        if let Some(src_shape) = self.shape()? {
            // Check dimension count
            ensure!(
                padding.len() == src_shape.len(),
                PadDimensionMismatchSnafu { padding_dims: padding.len(), shape_dims: src_shape.len() }
            );
        }

        let (begin_pads, end_pads) = ranges_to_uops(padding);
        let dtype = self.dtype();
        Ok(Self::new(Op::Pad { src: self.clone(), begin_pads, end_pads }, dtype))
    }

    /// Shrink (slice) with strict validation.
    ///
    /// Validates:
    /// - Range values are concrete (not symbolic)
    /// - begin <= end for each dimension
    /// - 0 <= begin, end <= dimension_size
    pub fn try_shrink(self: &Arc<Self>, ranges: &[(crate::SInt, crate::SInt)]) -> Result<Arc<Self>> {
        use crate::error::ShrinkBoundsViolationSnafu;
        use crate::shape::ranges_to_uops;
        use snafu::ensure;

        // Empty ranges (scalar) → identity
        if ranges.is_empty() {
            return Ok(self.clone());
        }

        // Symbolic shrink ranges are allowed — the rangeify pipeline handles
        // symbolic range ends. Only concrete ranges are bounds-checked.
        if let Some(src_shape) = self.shape()? {
            for (dim_idx, ((begin, end), dim_size)) in ranges.iter().zip(src_shape.iter()).enumerate() {
                if let (Some(b), Some(e), Some(s)) = (begin.as_const(), end.as_const(), dim_size.as_const()) {
                    ensure!(
                        b <= e && e <= s,
                        ShrinkBoundsViolationSnafu { dim: dim_idx, begin: b, end: e, shape_size: s }
                    );
                }
            }

            // Identity shrink: skip if all ranges span the full dimension
            if ranges.iter().zip(src_shape.iter()).all(|((b, e), d)| b.as_const() == Some(0) && *e == *d) {
                return Ok(self.clone());
            }
        }

        let (begins, ends) = ranges_to_uops(ranges);
        let dtype = self.dtype();
        let result = Self::new(Op::Shrink { src: self.clone(), begins, ends }, dtype);
        // Tinygrad (movement.py:128): return self if ret.shape == self.shape else ret
        if result.shape().ok().flatten() == self.shape().ok().flatten() {
            return Ok(self.clone());
        }
        Ok(result)
    }

    /// Flip with strict validation.
    ///
    /// Validates:
    /// - Flip specification length matches shape dimensions
    pub fn try_flip(self: &Arc<Self>, axes: Vec<bool>) -> Result<Arc<Self>> {
        // All-false flip: no-op
        if !axes.iter().any(|&a| a) {
            return Ok(self.clone());
        }

        if let Some(src_shape) = self.shape()? {
            Self::validate_flip_axes(&axes, src_shape.len())?;
        }

        let dtype = self.dtype();
        Ok(Self::new(Op::Flip { src: self.clone(), axes }, dtype))
    }

    /// Split tensor across multiple devices along specified axis.
    ///
    /// Creates a multi-device tensor where each device holds a shard.
    /// Use with MSTACK/MSELECT for distributed tensor operations.
    pub fn multi(src: Arc<Self>, axis: usize) -> Arc<Self> {
        let dtype = src.dtype();
        Self::new(Op::Multi { src, axis }, dtype)
    }
}