ogc-cql2 0.7.0

OGC CQL2 Text + JSON Encoding parser and interpreter in Rust
Documentation 
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// SPDX-License-Identifier: Apache-2.0

#![warn(missing_docs)]

//! Groups artifacts providing Features and Resources from known types used in
//! the geospatial ecosystem such as CSV, and GeoPackage files.
//!

#[cfg(feature = "csv_ds")]
mod csv;
#[cfg(feature = "gpkg_ds")]
mod gpkg;
#[cfg(feature = "pg_ds")]
mod pg;
#[cfg(any(feature = "gpkg_ds", feature = "pg_ds"))]
mod sql;
#[cfg(feature = "pg_ds")]
mod types;

#[cfg(feature = "csv_ds")]
pub use csv::*;
#[cfg(feature = "gpkg_ds")]
pub use gpkg::*;
#[cfg(feature = "pg_ds")]
pub use pg::*;
#[cfg(feature = "pg_ds")]
pub use types::*;

use crate::{Expression, Q};
use async_trait::async_trait;
use futures::stream::BoxStream;
use std::collections::HashMap;

/// A dictionary of queryable property names (strings) to [`Queryable`][Q] values.
pub type Resource = HashMap<String, Q>;

/// Trait for a type that can act as a data source provider of _Features_
/// and [`Resource`]s, including a _Geometry_ attribute, in the context of
/// processing CQL2 filter expressions.
///
/// A CSV file, and a GeoPackage autonomous database file are examples of this.
pub trait DataSource {
    /// Return SRID of this if it was known at construction; `None` otherwise.
    fn srid(&self) -> Option<u32>;
}

/// Capability of a [`DataSource`] to provide an iterator over a collection of
/// _Features_ or [Resources][Resource].
pub trait IterableDS {
    /// Type representing a Feature which must be convertible to a [Resource].
    type Item: TryInto<Resource, Error = Self::Err>;
    /// Error raised by this.
    type Err;

    /// Return an iterator over this data source _Features_.
    fn iter(&self) -> Result<impl Iterator<Item = Result<Self::Item, Self::Err>>, Self::Err>;
}

/// Capability of a [`DataSource`] to asynchronously stream _Features_ or
/// [Resources][Resource].
#[async_trait]
pub trait StreamableDS {
    /// Type representing a _Feature_ which must be convertible to a [`Resource`].
    type Item: TryInto<Resource, Error = Self::Err>;
    /// Error raised by this.
    type Err;

    /// Return an unfiltered stream of all data source _Features_.
    async fn fetch(&self) -> Result<BoxStream<'_, Result<Self::Item, Self::Err>>, Self::Err>;

    /// Return an unfiltered stream of all data source _Resources_.
    async fn stream(&self) -> Result<BoxStream<'_, Result<Resource, Self::Err>>, Self::Err>;

    /// Return a filtered stream of _Features_ satisfying a CQL2 filter [Expression].
    async fn fetch_where(
        &self,
        exp: &Expression,
    ) -> Result<BoxStream<'_, Result<Self::Item, Self::Err>>, Self::Err>;

    /// Return a filtered stream of _Resources_ satisfying a CQL2 filter [Expression].
    async fn stream_where(
        &self,
        exp: &Expression,
    ) -> Result<BoxStream<'_, Result<Resource, Self::Err>>, Self::Err>;
}