hdf5-pure 0.18.0

//! Public Rust views over decoded MATLAB MCOS opaque value classes.
//!
//! When [`crate::mat::from_bytes`] reads a MATLAB `datetime`, `duration`, or
//! `categorical` variable, it decodes the hidden `#subsystem#/MCOS` object into
//! its logical components. These structs deserialize from that decoded form, so
//! a field of one of these types in your `#[derive(Deserialize)]` struct picks
//! up the corresponding MATLAB variable directly:
//!
//! ```no_run
//! # #[cfg(feature = "serde")] {
//! use hdf5_pure::mat::{self, MatDatetime, MatCategorical};
//! use serde::Deserialize;
//!
//! #[derive(Deserialize)]
//! struct Log {
//!     timestamps: MatDatetime,
//!     labels: MatCategorical,
//! }
//!
//! let log: Log = mat::from_bytes(&std::fs::read("log.mat").unwrap()).unwrap();
//! let epoch_ns = log.timestamps.nanoseconds();
//! let resolved = log.labels.labels(); // Vec<Option<String>>
//! # let _ = (epoch_ns, resolved);
//! # }
//! ```
//!
//! The representations are lossless: the raw MATLAB storage (milliseconds since
//! the Unix epoch, category codes, …) is preserved, and helper methods offer the
//! common derived views.

use serde::Deserialize;

/// A decoded MATLAB `datetime` array.
///
/// MATLAB stores datetimes as milliseconds since the Unix epoch (1970-01-01
/// UTC, with no time-zone offset folded in) using a two-part "double-double"
/// value: the true millisecond count of each element is [`millis_utc`] `+`
/// [`sub_ms`]. [`millis_utc`] already carries sub-millisecond precision in its
/// fractional part; [`sub_ms`] is the residual below that part's `f64` ULP.
/// Both are preserved losslessly, and this split has been validated against
/// real MATLAB output. [`tz`] and [`fmt`] are display metadata and do not shift
/// the stored instant.
///
/// `NaT` (not-a-time) elements appear as `NaN` in [`millis_utc`].
///
/// [`millis_utc`]: MatDatetime::millis_utc
/// [`sub_ms`]: MatDatetime::sub_ms
/// [`tz`]: MatDatetime::tz
/// [`fmt`]: MatDatetime::fmt
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct MatDatetime {
    /// Milliseconds since 1970-01-01 UTC (the high part of the double-double;
    /// may be fractional), one per element in row-major order.
    pub millis_utc: Vec<f64>,
    /// Sub-millisecond residual (the low part of the double-double) per element,
    /// paired with `millis_utc`. Usually below the `f64` ULP of `millis_utc`.
    #[serde(default)]
    pub sub_ms: Vec<f64>,
    /// Time-zone name when the datetime is zoned (display metadata only).
    #[serde(default)]
    pub tz: Option<String>,
    /// Display format string, when present.
    #[serde(default)]
    pub fmt: Option<String>,
}

impl MatDatetime {
    /// Nanoseconds since the Unix epoch for each element.
    ///
    /// The true millisecond value is `millis_utc + sub_ms` (MATLAB's
    /// double-double), so this returns `(millis_utc + sub_ms) * 1e6`.
    /// `millis_utc` already carries sub-millisecond precision in its fractional
    /// part, which this preserves; the much smaller `sub_ms` residual is below
    /// the `f64` ULP at present-day epochs and so does not survive the
    /// arithmetic. For lossless sub-millisecond work read `millis_utc` and
    /// `sub_ms` directly. For whole-millisecond datetimes the result is exact.
    #[must_use]
    pub fn nanoseconds(&self) -> Vec<f64> {
        self.millis_utc
            .iter()
            .enumerate()
            .map(|(i, &millis)| {
                let sub = self.sub_ms.get(i).copied().unwrap_or(0.0);
                (millis + sub) * 1e6
            })
            .collect()
    }
}

/// A decoded MATLAB `duration` array.
///
/// MATLAB stores durations as milliseconds. [`millis`] is preserved losslessly;
/// [`fmt`] is the display unit and does not change the stored value.
///
/// [`millis`]: MatDuration::millis
/// [`fmt`]: MatDuration::fmt
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct MatDuration {
    /// Length of each element in milliseconds (row-major order).
    pub millis: Vec<f64>,
    /// Display unit (`s`/`m`/`h`/`d`/`y`), when present.
    #[serde(default)]
    pub fmt: Option<String>,
}

impl MatDuration {
    /// Each element's length in seconds.
    #[must_use]
    pub fn seconds(&self) -> Vec<f64> {
        self.millis.iter().map(|&m| m / 1000.0).collect()
    }
}

/// A decoded MATLAB `categorical` array.
///
/// [`codes`] holds the 1-based category index of each element (`0` is
/// `<undefined>`); [`categories`] is the category-name pool. [`is_ordinal`] and
/// [`is_protected`] mirror the MATLAB flags.
///
/// [`codes`]: MatCategorical::codes
/// [`categories`]: MatCategorical::categories
/// [`is_ordinal`]: MatCategorical::is_ordinal
/// [`is_protected`]: MatCategorical::is_protected
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct MatCategorical {
    /// 1-based category index per element (`0` = `<undefined>`), row-major.
    pub codes: Vec<u32>,
    /// The category-name pool, indexed by `code - 1`.
    pub categories: Vec<String>,
    /// Whether the categories are ordered (an ordinal categorical).
    #[serde(default)]
    pub is_ordinal: bool,
    /// Whether the category set is protected (no implicit new categories).
    #[serde(default)]
    pub is_protected: bool,
}

impl MatCategorical {
    /// The category label of each element, `None` for `<undefined>` (code `0`)
    /// or an out-of-range code.
    #[must_use]
    pub fn labels(&self) -> Vec<Option<String>> {
        self.codes
            .iter()
            .map(|&code| {
                if code == 0 {
                    None
                } else {
                    self.categories.get((code - 1) as usize).cloned()
                }
            })
            .collect()
    }
}

/// A decoded MATLAB enumeration array.
///
/// MATLAB enumerations (`classdef … enumeration … end`) store each element as a
/// named member of an enumeration class. [`class_name`] is the fully qualified
/// class (e.g. `"MyPkg.Color"`, or a bare `"Weekday"` for an unpackaged class);
/// [`names`] is the member name of each element (e.g. `"Red"`) in row-major
/// order.
///
/// The member name is the enumeration's identity, so it is what this view
/// surfaces. The underlying value backing each member (the `double` / integer
/// the member maps to) is not decoded.
///
/// [`class_name`]: MatEnum::class_name
/// [`names`]: MatEnum::names
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct MatEnum {
    /// The fully qualified enumeration class name.
    pub class_name: String,
    /// The member name of each element, row-major.
    pub names: Vec<String>,
}

impl MatEnum {
    /// The number of elements in the enumeration array.
    #[must_use]
    pub fn len(&self) -> usize {
        self.names.len()
    }

    /// Whether the enumeration array is empty (`0×0`).
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.names.is_empty()
    }
}