qubit-codec 0.17.4

// =============================================================================
//    Copyright (c) 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================

//! Local immutable value-codec registry.

use std::collections::BTreeMap;

use crate::ValueCodecId;
use crate::ValueCodecRegistration;
use crate::ValueCodecRegistryError;

// Implements process-wide lookup for the bytes-wire specialization.
#[path = "value_codec_registry/value_bytes_codec_registry.rs"]
mod value_bytes_codec_registry;
// Implements process-wide lookup for the string-wire specialization.
#[path = "value_codec_registry/value_string_codec_registry.rs"]
mod value_string_codec_registry;

pub use value_bytes_codec_registry::ValueBytesCodecRegistry;
pub use value_string_codec_registry::ValueStringCodecRegistry;

/// An immutable value-codec registry sorted by stable ID.
///
/// # Type Parameters
///
/// - `D`: Static descriptor type identifying one wire representation. The
///   registry API is implemented for descriptors that also satisfy `Copy`.
///
/// # Examples
///
/// ```
/// use qubit_codec::ValueCodecRegistry;
/// use qubit_codec::ValueStringCodecDescriptor;
/// use qubit_codec::ValueStringCodecRegistry;
///
/// let registry: ValueCodecRegistry<ValueStringCodecDescriptor> =
///     ValueStringCodecRegistry::empty();
/// assert!(registry.get("missing.example").is_none());
/// ```
#[derive(Debug)]
pub struct ValueCodecRegistry<D: 'static> {
    /// Owned registrations sorted once by stable ID during construction.
    registrations: Box<[ValueCodecRegistration<D>]>,
    /// Stable ID to position mapping into the immutable registration slice.
    indices: BTreeMap<ValueCodecId, usize>,
}

impl<D: Copy + 'static> ValueCodecRegistry<D> {
    /// Builds a local registry from static registrations without consulting
    /// or modifying the process-wide registry.
    ///
    /// # Parameters
    ///
    /// - `registrations`: Static entries copied into this registry; input order
    ///   is ignored.
    ///
    /// # Returns
    ///
    /// An owned, immutable registry sorted by ID, independent of the iterator.
    ///
    /// # Errors
    ///
    /// Returns a duplicate-ID error when multiple entries claim one ID.
    ///
    /// # Examples
    ///
    /// This example uses a local static registration; it does not submit an
    /// entry to the process-wide inventory.
    ///
    /// ```
    /// use std::convert::Infallible;
    /// use qubit_codec::ValueCodecId;
    /// use qubit_codec::ValueCodecRegistration;
    /// use qubit_codec::ValueCodecRegistrationSource;
    /// use qubit_codec::ValueDecoder;
    /// use qubit_codec::ValueEncoder;
    /// use qubit_codec::ValueStringCodecDescriptor;
    /// use qubit_codec::ValueStringCodecRegistration;
    /// use qubit_codec::ValueStringCodecRegistry;
    ///
    /// #[derive(Default)]
    /// struct LocalText;
    ///
    /// impl ValueEncoder<String> for LocalText {
    ///     type Output = String;
    ///     type Error = Infallible;
    ///
    ///     fn encode(&mut self, input: &String) -> Result<String, Infallible> {
    ///         Ok(input.clone())
    ///     }
    /// }
    ///
    /// impl ValueDecoder<str> for LocalText {
    ///     type Output = String;
    ///     type Error = Infallible;
    ///
    ///     fn decode(&mut self, input: &str) -> Result<String, Infallible> {
    ///         Ok(input.to_owned())
    ///     }
    /// }
    ///
    /// static DESCRIPTOR: ValueStringCodecDescriptor =
    ///     ValueStringCodecDescriptor::of::<LocalText, String>();
    /// static REGISTRATION: ValueStringCodecRegistration = ValueCodecRegistration::new(
    ///     ValueCodecId::new("example.local.text"),
    ///     &DESCRIPTOR,
    ///     ValueCodecRegistrationSource::new("local-example", "example", file!(), line!()),
    /// );
    ///
    /// let registry = ValueStringCodecRegistry::from_registrations([&REGISTRATION])
    ///     .expect("unique local registration");
    /// let descriptor = registry.get("example.local.text")
    ///     .expect("registered locally").descriptor();
    /// let encoded = descriptor.encode(&String::from("hello")).expect("encode");
    /// assert_eq!("hello", encoded);
    /// let decoded = descriptor.decode(&encoded).expect("decode");
    /// assert_eq!("hello", *decoded.downcast::<String>().expect("String output"));
    /// assert!(registry.get("example.missing").is_none());
    /// ```
    pub fn from_registrations(
        registrations: impl IntoIterator<Item = &'static ValueCodecRegistration<D>>,
    ) -> Result<Self, ValueCodecRegistryError> {
        Self::build(registrations.into_iter().copied().collect())
    }

    /// Returns an empty local registry.
    ///
    /// # Returns
    ///
    /// A local registry with no registrations or indexed IDs.
    #[must_use]
    #[inline]
    pub fn empty() -> Self {
        Self {
            registrations: Box::new([]),
            indices: BTreeMap::new(),
        }
    }

    /// Freezes registrations and rejects duplicate IDs.
    ///
    /// # Parameters
    ///
    /// - `registrations`: Owned entries sorted in place before indexing.
    ///
    /// # Returns
    ///
    /// An immutable registry owning the sorted entries and their lookup index.
    ///
    /// # Errors
    ///
    /// Returns `DuplicateId` with the lexically first conflicting ID and all
    /// of its sources sorted by source fields. Repeated identical sources are
    /// retained because each registration is reported.
    pub(super) fn build(mut registrations: Vec<ValueCodecRegistration<D>>) -> Result<Self, ValueCodecRegistryError> {
        registrations.sort_by_key(ValueCodecRegistration::id);
        for (index, pair) in registrations.windows(2).enumerate() {
            if pair[0].id() == pair[1].id() {
                let id = pair[0].id();
                let mut sources = registrations[index..]
                    .iter()
                    .take_while(|registration| registration.id() == id)
                    .map(ValueCodecRegistration::source)
                    .collect::<Vec<_>>();
                sources.sort_unstable();
                return Err(ValueCodecRegistryError::DuplicateId {
                    id: id.as_str(),
                    sources,
                });
            }
        }
        let indices = registrations
            .iter()
            .enumerate()
            .map(|(index, registration)| (registration.id(), index))
            .collect();
        Ok(Self {
            registrations: registrations.into_boxed_slice(),
            indices,
        })
    }

    /// Finds a registration by stable ID.
    ///
    /// # Parameters
    ///
    /// - `id`: Exact stable ID to look up, without normalization.
    ///
    /// # Returns
    ///
    /// `Some` borrows the matching registration from this registry; `None`
    /// means the ID is absent. Lookup uses a logarithmic tree search.
    #[inline]
    pub fn get(&self, id: &str) -> Option<&ValueCodecRegistration<D>> {
        let index = *self.indices.get(id)?;
        self.registrations.get(index)
    }

    /// Returns registrations in deterministic ID order.
    ///
    /// # Returns
    ///
    /// The immutable registration slice borrowed from this registry without
    /// allocation.
    #[must_use]
    #[inline]
    pub fn registrations(&self) -> &[ValueCodecRegistration<D>] {
        &self.registrations
    }
}