pedant-core 0.20.1

//! The snapshot-bound resolution result, and the one core validation boundary
//! that produces it.
//!
//! A report is only meaningful beside the snapshot it describes, so every
//! resolver entry point returns this wrapper and nothing else. Construction
//! rebinds the report's units to snapshot units by their stable keys and proves
//! every site coordinate exists in the exact snapshotted source; a report built
//! against another snapshot cannot pass.

use std::collections::BTreeMap;
use std::sync::Arc;

use pedant_types::{
    ResolutionReport, ResolutionUnit, ResolutionUnitId, SourceSpan, SymbolDefinition,
    SymbolReference,
};

use crate::resolution::rust::identity::{PackageId, TargetId, position};
use crate::resolution::rust::snapshot::{
    RustResolutionSnapshot, RustResolutionUnit, RustSnapshotUnitId,
};
use crate::resolution::rust::warning;

use super::coordinates::LineIndex;
use super::error::RustResolutionError;

/// The stable key one snapshot unit is identified by across reports.
pub(super) fn unit_key(unit: &RustResolutionUnit) -> Arc<str> {
    warning::unit_key(unit)
}

/// The canonical Cargo crate name one target compiles under.
pub(super) fn crate_name(unit: &RustResolutionUnit) -> Arc<str> {
    Arc::from(unit.name().replace('-', "_"))
}

/// What one report-local unit identifier binds to in the snapshot.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct RustUnitBinding {
    unit: ResolutionUnitId,
    snapshot_unit: RustSnapshotUnitId,
    package: PackageId,
    target: TargetId,
}

impl RustUnitBinding {
    /// The report-local identifier this binding answers for.
    pub fn unit(&self) -> ResolutionUnitId {
        self.unit
    }

    /// The snapshot unit the report unit describes.
    pub fn snapshot_unit(&self) -> RustSnapshotUnitId {
        self.snapshot_unit
    }

    /// The package that declares the bound Cargo target.
    pub fn package(&self) -> PackageId {
        self.package
    }

    /// The Cargo target the report unit compiles.
    pub fn target(&self) -> TargetId {
        self.target
    }
}

/// One resolution result, bound to the snapshot it describes.
#[derive(Debug, Clone)]
pub struct RustTargetResolution {
    root_target: TargetId,
    units: Box<[RustUnitBinding]>,
    report: Arc<ResolutionReport>,
}

impl RustTargetResolution {
    /// Bind `report` to `snapshot`, or refuse every disagreement between them.
    pub fn try_new(
        snapshot: &RustResolutionSnapshot,
        report: ResolutionReport,
    ) -> Result<Self, RustResolutionError> {
        let units = bind_units(snapshot, report.units())?;
        validate_sites(snapshot, &report)?;
        Ok(Self {
            root_target: snapshot.root_target(),
            units,
            report: Arc::new(report),
        })
    }

    /// The target this resolution was requested for.
    pub fn root_target(&self) -> TargetId {
        self.root_target
    }

    /// Every report-local unit identifier and the Cargo target it names.
    pub fn units(&self) -> &[RustUnitBinding] {
        &self.units
    }

    /// The binding one report-local unit identifier selects.
    pub fn unit(&self, unit: ResolutionUnitId) -> Option<&RustUnitBinding> {
        self.units.get(usize::try_from(unit.index()).ok()?)
    }

    /// The validated report, shared rather than copied.
    pub fn report(&self) -> &ResolutionReport {
        &self.report
    }

    /// A second handle on the same validated report.
    pub fn shared_report(&self) -> Arc<ResolutionReport> {
        Arc::clone(&self.report)
    }
}

fn bind_units(
    snapshot: &RustResolutionSnapshot,
    units: &[ResolutionUnit],
) -> Result<Box<[RustUnitBinding]>, RustResolutionError> {
    if units.len() != snapshot.units().len() {
        return Err(RustResolutionError::UnitMapping {
            unit: position(units.len()),
            reason: Box::from("the report and the snapshot hold different unit counts"),
        });
    }
    let keyed = keyed_units(snapshot);
    units.iter().map(|unit| bind_unit(&keyed, unit)).collect()
}

/// Every snapshot unit under its stable key, so binding a report of N units
/// formats N keys rather than one key per candidate per report unit.
fn keyed_units(snapshot: &RustResolutionSnapshot) -> BTreeMap<Arc<str>, &RustResolutionUnit> {
    snapshot
        .units()
        .iter()
        .map(|unit| (unit_key(unit), unit))
        .collect()
}

fn bind_unit(
    keyed: &BTreeMap<Arc<str>, &RustResolutionUnit>,
    unit: &ResolutionUnit,
) -> Result<RustUnitBinding, RustResolutionError> {
    let found = keyed
        .get(unit.key())
        .ok_or_else(|| RustResolutionError::UnitMapping {
            unit: unit.id().index(),
            reason: Box::from("no snapshot unit carries this key"),
        })?;
    Ok(RustUnitBinding {
        unit: unit.id(),
        snapshot_unit: found.id(),
        package: found.package(),
        target: found.target(),
    })
}

/// Prove every stated coordinate against the exact snapshotted source.
///
/// Each source is indexed once rather than once per site: a report states many
/// thousands of sites over the same files, and building the line table per site
/// rescanned whole sources for coordinates derived from those same tables.
fn validate_sites(
    snapshot: &RustResolutionSnapshot,
    report: &ResolutionReport,
) -> Result<(), RustResolutionError> {
    let lines = indexed_sources(snapshot);
    for definition in report.definitions() {
        validate_span(snapshot, &lines, SymbolDefinition::span(definition))?;
    }
    for reference in report.references() {
        validate_span(snapshot, &lines, SymbolReference::span(reference))?;
    }
    Ok(())
}

fn indexed_sources(snapshot: &RustResolutionSnapshot) -> BTreeMap<&str, LineIndex> {
    snapshot
        .sources()
        .iter()
        .map(|source| (source.path(), LineIndex::new(source.text())))
        .collect()
}

fn validate_span(
    snapshot: &RustResolutionSnapshot,
    lines: &BTreeMap<&str, LineIndex>,
    span: &SourceSpan,
) -> Result<(), RustResolutionError> {
    let stated = snapshot
        .source(span.file())
        .zip(lines.get(span.file()))
        .ok_or_else(|| RustResolutionError::UnknownFile {
            file: Box::from(span.file()),
        })?;
    let (source, index) = stated;
    for at in [span.start(), span.end()] {
        if !index.holds(source.text(), at) {
            return Err(RustResolutionError::InvalidCoordinate {
                file: Box::from(span.file()),
                line: at.line(),
                column: at.column(),
            });
        }
    }
    Ok(())
}