jyafn 0.3.1

Computational graphs for Data Science that compile to machine code
Documentation 
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use std::collections::HashMap;
use std::fmt::{self, Display};

use crate::Ref;

use super::{Layout, Struct, ISOFORMAT};

/// A ref value represents jyafn [`Ref`]s in a structured way, similar to [`serde_json::Value`].
#[derive(Debug)]
pub enum RefValue {
    /// An empty value.
    Unit,
    /// A floating point reference.
    Scalar(Ref),
    /// A boolean reference.
    Bool(Ref),
    /// A datetime reference.
    DateTime(Ref),
    /// A symbol reference.
    Symbol(Ref),
    /// A struct of values.
    Struct(HashMap<String, RefValue>),
    /// Atuple of values.
    Tuple(Vec<RefValue>),
    /// A list of values, all of the same layout.
    List(Vec<RefValue>),
}

impl Display for RefValue {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Unit => write!(f, "unit"),
            Self::Scalar(s) => write!(f, "scalar {s}"),
            Self::Bool(s) => write!(f, "bool {s}"),
            Self::DateTime(s) => write!(f, "datetime {s}"),
            Self::Symbol(s) => write!(f, "symbol {s}"),
            Self::Struct(fields) => {
                write!(f, "{{ ")?;
                for (name, field) in fields {
                    write!(f, "{name}: {field}, ")?;
                }
                write!(f, "}}")
            }
            Self::Tuple(fields) => {
                write!(f, "( ")?;
                for field in fields {
                    write!(f, "{field}, ")?;
                }
                write!(f, ")")
            }
            Self::List(list) => {
                write!(f, "[ ")?;
                for field in list {
                    write!(f, "{field}, ")?;
                }
                write!(f, "]")
            }
        }
    }
}

impl RefValue {
    /// Creates a possible layout for this ref value. The putative layout is guaranteed
    /// to structurally match `self`.
    pub fn putative_layout(&self) -> Layout {
        match self {
            Self::Unit => Layout::Unit,
            Self::Scalar(_) => Layout::Scalar,
            Self::Bool(_) => Layout::Bool,
            Self::DateTime(_) => Layout::DateTime(ISOFORMAT.to_string()),
            Self::Symbol(_) => Layout::Symbol,
            Self::Struct(fields) => Layout::Struct(Struct({
                let mut strct = fields
                    .iter()
                    .map(|(name, field)| (name.clone(), field.putative_layout()))
                    .collect::<Vec<_>>();
                strct.sort_unstable_by_key(|(n, _)| n.clone());
                strct
            })),
            Self::Tuple(fields) => {
                Layout::Tuple(fields.iter().map(Self::putative_layout).collect())
            }
            Self::List(list) => {
                if let Some(first) = list.first() {
                    Layout::List(Box::new(first.putative_layout()), list.len())
                } else {
                    Layout::List(Box::new(Layout::Scalar), 0)
                }
            }
        }
    }

    /// Given a layout, creates a list of [`Ref`]s of this ref value. Returns `None` if
    /// that is not possible.
    pub fn output_vec(&self, layout: &Layout) -> Option<Vec<Ref>> {
        let mut buffer = vec![];
        self.build_output_vec(layout, &mut buffer)?;
        Some(buffer)
    }

    /// Does the heavy lifting for [`RefVa;ue::output_vec`].
    fn build_output_vec(&self, layout: &Layout, buf: &mut Vec<Ref>) -> Option<()> {
        match (self, layout) {
            (Self::Unit, Layout::Unit) => {}
            (Self::Scalar(s), Layout::Scalar) => buf.push(*s),
            (Self::Bool(s), Layout::Bool) => buf.push(*s),
            (Self::DateTime(s), Layout::DateTime(_)) => buf.push(*s),
            (Self::Symbol(s), Layout::Symbol) => buf.push(*s),
            (Self::Struct(vals), Layout::Struct(fields)) => {
                for (name, field) in &fields.0 {
                    vals.get(name)?.build_output_vec(field, buf);
                }
            }
            (Self::Tuple(vals), Layout::Tuple(fields)) => {
                if vals.len() != fields.len() {
                    return None;
                }

                for (val, field) in vals.iter().zip(fields) {
                    val.build_output_vec(field, buf)?;
                }
            }
            (Self::List(list), Layout::List(element, size)) if list.len() == *size => {
                for item in list {
                    item.build_output_vec(element, buf)?;
                }
            }
            _ => return None,
        }

        Some(())
    }
}