vyre-primitives 0.6.1

//! Functorial data migration primitive (#52).
//!
//! Categorical data migration (Spivak 2012, Patterson 2022 Catlab.jl):
//! treat schema migrations between databases as functors `F: C → D`.
//! Each instance migration is a graph rewrite.
//!
//! This file ships the **per-cell functor application** primitive  -
//! given a source-instance row, a functor encoded as a column-mapping
//! lookup table, emit the target-instance row. Composes with
//! `level_wave_program` for whole-schema migration.

use std::sync::Arc;

use vyre_foundation::ir::model::expr::Ident;
use vyre_foundation::ir::{BufferAccess, BufferDecl, DataType, Expr, Node, Program};

/// Op id.
pub const OP_ID: &str = "vyre-primitives::graph::functor_apply";

/// Apply column-mapping functor to a source-instance row.
/// `source_row[i]` becomes `target_row[mapping[i]]` for `i ∈ 0..n_cols`.
#[must_use]
pub fn functor_apply(source_row: &str, mapping: &str, target_row: &str, n_cols: u32) -> Program {
    functor_apply_sized(source_row, mapping, target_row, n_cols, n_cols)
}

/// Apply a column-mapping functor to a source-instance row with an explicit
/// target row width.
///
/// This emits a target-centric gather rather than a source-centric scatter:
/// lane `t` scans all source columns and takes the last source whose mapping is
/// `t`. That preserves the CPU reference's deterministic last-wins contract
/// while avoiding data races when several source columns alias the same target.
#[must_use]
pub fn functor_apply_sized(
    source_row: &str,
    mapping: &str,
    target_row: &str,
    n_cols: u32,
    target_n_cols: u32,
) -> Program {
    if n_cols == 0 {
        return crate::invalid_output_program(
            OP_ID,
            target_row,
            DataType::U32,
            "Fix: functor_apply requires n_cols > 0, got 0.".to_string(),
        );
    }
    if target_n_cols == 0 {
        return crate::invalid_output_program(
            OP_ID,
            target_row,
            DataType::U32,
            "Fix: functor_apply requires target_n_cols > 0, got 0.".to_string(),
        );
    }

    let t = Expr::InvocationId { axis: 0 };

    let body = vec![Node::if_then(
        Expr::lt(t.clone(), Expr::u32(target_n_cols)),
        vec![
            Node::let_bind("value", Expr::u32(0)),
            Node::loop_for(
                "src",
                Expr::u32(0),
                Expr::u32(n_cols),
                vec![Node::if_then(
                    Expr::eq(Expr::load(mapping, Expr::var("src")), t.clone()),
                    vec![Node::assign(
                        "value",
                        Expr::load(source_row, Expr::var("src")),
                    )],
                )],
            ),
            Node::store(target_row, t, Expr::var("value")),
        ],
    )];

    Program::wrapped(
        vec![
            BufferDecl::storage(source_row, 0, BufferAccess::ReadOnly, DataType::U32)
                .with_count(n_cols),
            BufferDecl::storage(mapping, 1, BufferAccess::ReadOnly, DataType::U32)
                .with_count(n_cols),
            BufferDecl::storage(target_row, 2, BufferAccess::ReadWrite, DataType::U32)
                .with_count(target_n_cols),
        ],
        [256, 1, 1],
        vec![Node::Region {
            generator: Ident::from(OP_ID),
            source_region: None,
            body: Arc::new(body),
        }],
    )
}

/// CPU reference.
#[must_use]
#[cfg(any(test, feature = "cpu-parity"))]
pub fn functor_apply_cpu(source_row: &[u32], mapping: &[u32], target_size: u32) -> Vec<u32> {
    try_functor_apply_cpu(source_row, mapping, target_size)
        .unwrap_or_else(|error| panic!("{error}"))
}

/// Fallible CPU reference.
#[cfg(any(test, feature = "cpu-parity"))]
pub fn try_functor_apply_cpu(
    source_row: &[u32],
    mapping: &[u32],
    target_size: u32,
) -> Result<Vec<u32>, String> {
    let mut out = Vec::new();
    try_functor_apply_cpu_into(source_row, mapping, target_size, &mut out)?;
    Ok(out)
}

/// Fallible CPU reference using caller-owned storage.
#[cfg(any(test, feature = "cpu-parity"))]
pub fn try_functor_apply_cpu_into(
    source_row: &[u32],
    mapping: &[u32],
    target_size: u32,
    out: &mut Vec<u32>,
) -> Result<(), String> {
    out.clear();
    resize_functor_cpu_vec(out, target_size as usize, 0u32, "functor_apply CPU output")?;
    for (&src, &dst) in source_row.iter().zip(mapping.iter()) {
        if let Some(slot) = out.get_mut(dst as usize) {
            *slot = src;
        }
    }
    Ok(())
}

#[cfg(any(test, feature = "cpu-parity"))]
fn resize_functor_cpu_vec<T: Clone>(
    out: &mut Vec<T>,
    len: usize,
    value: T,
    context: &str,
) -> Result<(), String> {
    if len > out.len() {
        crate::graph::scratch::reserve_graph_items(
            out,
            len - out.len(),
            "functorial migration CPU oracle",
            context,
        )?;
    }
    out.resize(len, value);
    Ok(())
}

#[cfg(feature = "inventory-registry")]
inventory::submit! {
    crate::harness::OpEntry::new(
        OP_ID,
        || functor_apply("source_row", "mapping", "target_row", 4),
        Some(|| {
            let to_bytes = |w: &[u32]| crate::wire::pack_u32_slice(w);
            vec![vec![
                to_bytes(&[10, 20, 30, 40]), // source_row
                to_bytes(&[2, 0, 1, 3]),     // mapping
                to_bytes(&[0, 0, 0, 0]),     // target_row
            ]]
        }),
        Some(|| {
            let to_bytes = |w: &[u32]| crate::wire::pack_u32_slice(w);
            vec![vec![to_bytes(&[20, 30, 10, 40])]]
        }),
    )
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn cpu_identity_mapping() {
        let src = vec![10u32, 20, 30];
        let map = vec![0u32, 1, 2];
        let out = functor_apply_cpu(&src, &map, 3);
        assert_eq!(out, src);
    }

    #[test]
    fn cpu_permutation_mapping() {
        let src = vec![10u32, 20, 30];
        let map = vec![2u32, 0, 1];
        let out = functor_apply_cpu(&src, &map, 3);
        assert_eq!(out, vec![20, 30, 10]);
    }

    #[test]
    fn cpu_target_larger_than_source_zero_padded() {
        let src = vec![10u32, 20];
        let map = vec![0u32, 2];
        let out = functor_apply_cpu(&src, &map, 4);
        assert_eq!(out, vec![10, 0, 20, 0]);
    }

    #[test]
    fn cpu_mismatched_or_out_of_range_mapping_is_ignored() {
        let out = functor_apply_cpu(&[7, 8], &[3], 2);
        assert_eq!(out, vec![0, 0]);
    }

    #[test]
    fn cpu_duplicate_mapping_is_last_wins() {
        let out = functor_apply_cpu(&[7, 8, 9], &[1, 1, 1], 3);
        assert_eq!(out, vec![0, 9, 0]);
    }

    #[test]
    fn generated_cpu_oracle_preserves_last_wins_and_ignores_oob() {
        let mut out = Vec::new();
        for case in 0..4096usize {
            let source_len = case % 65;
            let map_len = (case / 3) % 65;
            let target_size = ((case / 11) % 65) as u32;
            let source_row: Vec<u32> = (0..source_len)
                .map(|idx| (idx as u32).wrapping_mul(17).wrapping_add(case as u32))
                .collect();
            let mapping: Vec<u32> = (0..map_len)
                .map(|idx| ((idx * 7 + case) % 83) as u32)
                .collect();

            try_functor_apply_cpu_into(&source_row, &mapping, target_size, &mut out)
                .expect("Fix: caller must pre-size buffers; use fallible reserve or return ResourceExhausted - generated functor CPU oracle should reserve and evaluate");
            let expected = independent_functor_apply(&source_row, &mapping, target_size);

            assert_eq!(out, expected, "case {case}: functor CPU oracle mismatch");
        }
    }

    fn independent_functor_apply(
        source_row: &[u32],
        mapping: &[u32],
        target_size: u32,
    ) -> Vec<u32> {
        let mut out = Vec::new();
        out.resize(target_size as usize, 0);
        for idx in 0..source_row.len().min(mapping.len()) {
            let dst = mapping[idx] as usize;
            if dst < out.len() {
                out[dst] = source_row[idx];
            }
        }
        out
    }

    #[test]
    fn ir_program_buffer_layout() {
        let p = functor_apply("s", "m", "t", 8);
        assert_eq!(p.workgroup_size, [256, 1, 1]);
        for buf in p.buffers.iter() {
            assert_eq!(buf.count(), 8);
        }
    }

    #[test]
    fn sized_ir_program_buffer_layout() {
        let p = functor_apply_sized("s", "m", "t", 3, 5);
        assert_eq!(p.workgroup_size, [256, 1, 1]);
        assert_eq!(p.buffers[0].count(), 3);
        assert_eq!(p.buffers[1].count(), 3);
        assert_eq!(p.buffers[2].count(), 5);
    }

    #[test]
    fn zero_n_cols_traps() {
        let p = functor_apply("s", "m", "t", 0);
        assert!(p.stats().trap());
    }

    #[test]
    fn functor_cpu_source_uses_fallible_reusable_target_row() {
        let source = include_str!("functorial.rs");
        let cpu_source = source
            .split("/// CPU reference.")
            .nth(1)
            .expect("Fix: functor CPU source must be present")
            .split("#[cfg(feature = \"inventory-registry\")]")
            .next()
            .expect("Fix: functor CPU source must precede registry entry");

        assert!(
            cpu_source.contains("try_functor_apply_cpu_into")
                && cpu_source.contains("resize_functor_cpu_vec")
                && cpu_source.contains("crate::graph::scratch::reserve_graph_items")
                && !cpu_source.contains("fn reserve_functor_cpu_vec")
                && !cpu_source.contains("vec![0u32; target_size as usize]")
                && !cpu_source.contains("Vec::with_capacity")
                && !cpu_source.contains(".reserve("),
            "Fix: functor CPU oracle must use fallible caller-owned target storage."
        );
    }
}