mant-query 0.11.0

//! Budgeted occurrence projection; never loads destinations or builds `SemanticIndex`.

mod resolution;
#[cfg(test)]
mod tests;

use mant_ir::{
    ContentRevealRef, Document, DocumentAddress, LinkOccurrenceRef, LinkTarget, NavigationEvent,
    NavigationScanOptions, ReferenceFormAssociationState, ReferenceLinkFilter, ReferenceScanLimits,
    ReferenceScope, ReferenceTargetType, ReferenceWorkBudget, reference_form_associations,
    scan_navigation_scope_with_budget,
};
use mant_protocol::{
    ReferenceAssociation, ReferenceCount, ReferenceCoverage, ReferenceInventory,
    ReferencePageLimit, ReferenceProjection, ReferenceProjectionMode, ReferenceRecord,
    ReferenceUnknownReason,
};
use std::{collections::BTreeSet, ops::ControlFlow};

/// Independent reference operation budgets; input-file size is not a substitute.
#[derive(Debug, Clone, Copy)]
pub struct ReferenceProjectionLimits {
    /// Shared traversal, label, form and local-destination inspection limits.
    pub scan: ReferenceScanLimits,
    /// Distinct typed-target keys; clamped to 4,096.
    pub distinct_targets: usize,
    /// Total retained distinct key text/metadata; clamped to 1 MiB.
    pub distinct_bytes: usize,
    /// Total materialized records/positions/labels; default 256 KiB, ceiling 1 MiB.
    pub materialization_bytes: usize,
}

impl Default for ReferenceProjectionLimits {
    fn default() -> Self {
        Self {
            scan: ReferenceScanLimits::default(),
            distinct_targets: 4096,
            distinct_bytes: 1024 * 1024,
            materialization_bytes: 256 * 1024,
        }
    }
}

/// Project selected original links without catalog I/O or implicit document loading.
/// Invalid policies return an unscanned inventory; process boundaries validate first.
#[must_use]
pub fn project_references(
    document: &Document,
    source_address: Option<&DocumentAddress>,
    scope: ReferenceScope<'_>,
    policy: &ReferenceProjection,
) -> ReferenceInventory {
    project_references_with_limits(
        document,
        source_address,
        scope,
        policy,
        ReferenceProjectionLimits::default(),
    )
}

/// Project under explicit hard-clamped budgets, including all skipped offset work.
#[must_use]
pub fn project_references_with_limits(
    document: &Document,
    source_address: Option<&DocumentAddress>,
    scope: ReferenceScope<'_>,
    policy: &ReferenceProjection,
    mut limits: ReferenceProjectionLimits,
) -> ReferenceInventory {
    limits.distinct_targets = limits.distinct_targets.min(4096);
    limits.distinct_bytes = limits.distinct_bytes.min(1024 * 1024);
    limits.materialization_bytes = limits.materialization_bytes.min(1024 * 1024);
    if policy.validate().is_err() {
        return invalid_policy(policy);
    }
    let mut result = ReferenceInventory::not_scanned(policy.clone());
    if policy.mode == ReferenceProjectionMode::None {
        return result;
    }
    let mut budget = ReferenceWorkBudget::new(limits.scan);
    let mut targets = BTreeSet::new();
    let mut target_bytes = 0usize;
    let mut targets_complete = true;
    let mut occurrences = 0usize;
    let mut retained_bytes = 0usize;
    let source_bytes = source_address.map_or(0, address_bytes);
    let report = scan_navigation_scope_with_budget(
        document,
        scope,
        &mut budget,
        NavigationScanOptions {
            links: ReferenceLinkFilter::from_types(&policy.target_types),
            ..Default::default()
        },
        |event, budget| {
            let NavigationEvent::Link(occurrence) = event else {
                return ControlFlow::Continue(());
            };
            let index = occurrences;
            occurrences += 1;
            if targets_complete {
                // At most 4,096 keys: reserve bounded comparisons and insert
                // inspection, not just the single scanner visit to this text.
                if budget
                    .consume(
                        occurrence.location.depth(),
                        1,
                        target_size(occurrence.target).saturating_mul(16),
                    )
                    .is_err()
                {
                    return ControlFlow::Break(());
                }
                let key = target_key(occurrence.target);
                if !targets.contains(&key) {
                    let bytes = target_size(occurrence.target).saturating_add(32);
                    if targets.len() >= limits.distinct_targets
                        || bytes > limits.distinct_bytes.saturating_sub(target_bytes)
                    {
                        targets_complete = false;
                    } else {
                        targets.insert(key);
                        target_bytes += bytes;
                    }
                }
            }
            if policy.mode != ReferenceProjectionMode::All
                || index < (policy.offset as usize)
                || result.page.limited.is_some()
            {
                return ControlFlow::Continue(());
            }
            if result.records.len() >= policy.limit as usize {
                result.page.limited = Some(ReferencePageLimit::Records);
                return ControlFlow::Continue(());
            }
            match materialize(
                occurrence,
                source_address,
                source_bytes,
                budget,
                &mut retained_bytes,
                limits.materialization_bytes,
            ) {
                Ok(record) => result.records.push(record),
                Err(limit) => result.page.limited = Some(limit),
            }
            ControlFlow::Continue(())
        },
    );
    finish_inventory(
        &mut result,
        report,
        occurrences,
        targets.len(),
        targets_complete,
    );
    result.target_coverage = resolution::validate_local(
        document,
        source_address,
        &mut result.records,
        &mut budget,
        &mut retained_bytes,
        limits.materialization_bytes,
    );
    result
}

fn invalid_policy(policy: &ReferenceProjection) -> ReferenceInventory {
    // Never clone an invalid caller-provided, potentially huge type vector.
    let mut invalid = ReferenceInventory::not_scanned(ReferenceProjection {
        mode: policy.mode,
        target_types: Vec::new(),
        offset: policy.offset,
        limit: policy.limit.clamp(1, 1000),
    });
    invalid.occurrences = ReferenceCount::Unknown {
        reason: ReferenceUnknownReason::InvalidPolicy,
    };
    invalid.targets = ReferenceCount::Unknown {
        reason: ReferenceUnknownReason::InvalidPolicy,
    };
    invalid
}

fn finish_inventory(
    result: &mut ReferenceInventory,
    report: mant_ir::ReferenceScanReport,
    occurrences: usize,
    targets: usize,
    targets_complete: bool,
) {
    let count = |value, exact| {
        if exact {
            ReferenceCount::Exact { value }
        } else {
            ReferenceCount::LowerBound { value }
        }
    };
    result.occurrences = count(occurrences as u64, report.complete());
    result.targets = count(targets as u64, report.complete() && targets_complete);
    result.coverage = ReferenceCoverage::from_report(report);
    result.page.returned = u32::try_from(result.records.len()).unwrap_or(u32::MAX);
    if !report.complete()
        && result.policy.mode == ReferenceProjectionMode::All
        && result.page.limited.is_none()
    {
        result.page.limited = Some(ReferencePageLimit::Scan);
    }
    let next = result.policy.offset.saturating_add(result.page.returned);
    // Only a completed scan proves that a fresh operation can reach the next
    // source position; zero-progress materialization never advertises a loop.
    if report.complete() && result.page.returned > 0 && (next as usize) < occurrences {
        result.page.next_offset = Some(next);
    }
}

fn materialize(
    occurrence: LinkOccurrenceRef<'_, '_>,
    source_address: Option<&DocumentAddress>,
    source_bytes: usize,
    budget: &mut ReferenceWorkBudget,
    retained: &mut usize,
    limit: usize,
) -> Result<ReferenceRecord, ReferencePageLimit> {
    let owner = occurrence
        .content_owner
        .map(|owner| ContentRevealRef::Owner(owner.location));
    let semantic_owner = occurrence
        .semantic_owner
        .map(|owner| ContentRevealRef::Owner(owner.location));
    budget
        .consume(
            occurrence.location.depth(),
            occurrence
                .location
                .depth()
                .saturating_add(owner.map_or(0, ContentRevealRef::depth))
                .saturating_add(semantic_owner.map_or(0, ContentRevealRef::depth))
                .saturating_mul(4),
            source_bytes,
        )
        .map_err(|_| ReferencePageLimit::Scan)?;
    let owner_bytes = owner.map_or(0, ContentRevealRef::encoded_size_bound);
    let forms_reservation = occurrence
        .semantic_owner
        .and_then(|owner| owner.owner.facts())
        .map_or(0, |facts| {
            facts
                .forms
                .len()
                .min(mant_ir::MAX_REFERENCE_FORM_ASSOCIATIONS)
                .saturating_mul(12)
        });
    let bytes = occurrence
        .location
        .encoded_len()
        .saturating_mul(2)
        .saturating_add(owner_bytes)
        .saturating_add(semantic_owner.map_or(0, ContentRevealRef::encoded_size_bound))
        .saturating_add(target_size(occurrence.target).saturating_mul(3))
        .saturating_add(source_bytes.saturating_mul(2))
        .saturating_add(forms_reservation)
        .saturating_add(256);
    if bytes > limit.saturating_sub(*retained) {
        return Err(ReferencePageLimit::MaterializationBytes);
    }
    let origin = occurrence
        .location
        .to_owned()
        .ok_or(ReferencePageLimit::Position)?;
    let owner = match owner {
        Some(owner) => Some(owner.to_owned().ok_or(ReferencePageLimit::Position)?),
        None => None,
    };
    let label = mant_ir::reference_label(
        occurrence.label,
        occurrence.location.depth(),
        budget,
        4096.min(limit.saturating_sub(*retained).saturating_sub(bytes)),
    )
    .map_err(|_| ReferencePageLimit::Scan)?;
    let label_truncated = label.truncated;
    let label = label.text;
    let association = reference_form_associations(occurrence, budget);
    let association = match association.state {
        ReferenceFormAssociationState::Unrecorded => ReferenceAssociation::Unrecorded {},
        ReferenceFormAssociationState::Complete => ReferenceAssociation::Valid {
            forms: association.forms,
            owner: semantic_owner
                .and_then(ContentRevealRef::to_owned)
                .ok_or(ReferencePageLimit::Position)?,
        },
        ReferenceFormAssociationState::Invalid => ReferenceAssociation::Invalid {},
        ReferenceFormAssociationState::Limited(_)
        | ReferenceFormAssociationState::MaterializationLimit => ReferenceAssociation::Limited {},
    };
    let total = bytes.saturating_add(label.len());
    if total > limit.saturating_sub(*retained) {
        return Err(ReferencePageLimit::MaterializationBytes);
    }
    *retained += total;
    Ok(ReferenceRecord {
        source_read: source_read(occurrence.location),
        origin,
        owner,
        label,
        label_truncated,
        target: occurrence.target.clone(),
        association,
        resolution: resolution::initial(occurrence.target, source_address),
    })
}

fn source_read(location: mant_ir::ContentLocationRef<'_>) -> mant_protocol::ContentSelector {
    use std::fmt::Write;
    let sections = match location {
        mant_ir::ContentLocationRef::DocumentHeading { .. } => &[][..],
        mant_ir::ContentLocationRef::SectionHeading { sections, .. }
        | mant_ir::ContentLocationRef::Content { sections, .. } => sections,
    };
    let mut path = String::new();
    for index in sections {
        let number = u64::from(*index) + 1;
        let digits = number.ilog10() as usize + 1;
        // Deep positions can exceed the readable selector's 512-byte contract;
        // return the nearest representable ancestor, not an invalid selector.
        if path.len() + usize::from(!path.is_empty()) + digits > 512 {
            break;
        }
        if !path.is_empty() {
            path.push('.');
        }
        write!(&mut path, "{number}").expect("String write cannot fail");
    }
    mant_protocol::ContentSelector::path(if path.is_empty() {
        "root".to_owned()
    } else {
        path
    })
}

fn target_key(target: &LinkTarget) -> (ReferenceTargetType, &str, Option<&str>) {
    match target {
        LinkTarget::Document { name, fragment } => {
            (ReferenceTargetType::Document, name, fragment.as_deref())
        }
        LinkTarget::Manual {
            name,
            manual_section,
        } => (ReferenceTargetType::Manual, name, manual_section.as_deref()),
        LinkTarget::Section { id } => (ReferenceTargetType::Local, id.as_str(), None),
        LinkTarget::External { uri } => (ReferenceTargetType::External, uri, None),
        LinkTarget::Email { address } => (ReferenceTargetType::Email, address, None),
    }
}

fn target_size(target: &LinkTarget) -> usize {
    let (_, a, b) = target_key(target);
    a.len().saturating_add(b.map_or(0, str::len))
}
fn address_bytes(address: &DocumentAddress) -> usize {
    match address {
        DocumentAddress::Manual {
            name,
            manual_section,
        } => name.len().saturating_add(manual_section.len()),
        DocumentAddress::Markdown { path, origin } => path.len().saturating_add(match origin {
            mant_ir::MarkdownOrigin::Documents => 0,
            mant_ir::MarkdownOrigin::Source { name } => name.len(),
        }),
    }
}