rto-render 5.8.1

//! Inspect an OKF bundle **as a bundle**, without importing it.
//!
//! [`read`](super::read) answers "what would this add to the graph". This module
//! answers questions about the bundle itself — what it claims, whether it hangs
//! together, how it differs from another copy — and answers them with somebody
//! else's implementation of the specification.
//!
//! # Why an independent implementation is the whole value
//!
//! Roteiro both *writes* OKF (`render okf`) and *reads* it (`import --from
//! okf`). A reader of our own construction, run over our own output, would
//! agree with us about a format we also invent: it can only catch a mistake we
//! did not make twice. `okf-core` is an independent reading of the same
//! specification by an author who is not us, so its disagreement is
//! *information*.
//!
//! That is not hypothetical here. ADR-0021 records that deriving a concept's
//! path from its node key "guessed wrong for 43 links" in a real render, and the
//! reader's own YAML subset silently dropped every human sign-off in Google's
//! published bundles until an independent oracle was pointed at it. Both were
//! found by checking our output against something that did not share our
//! assumptions.
//!
//! # What is here, and what is not
//!
//! [`trust_summary`], [`link_report`] and [`diff_report`], all built on
//! `okf-core` — **one crate, zero transitive dependencies**.
//!
//! Conformance checking and hygiene linting are **not** here. They live
//! upstream in a second crate, `okf-validator`, whose dependencies are not
//! optional and which syntax-checks fenced code blocks in eight languages.
//! Taking it means taking `rustpython-parser`: 61 crates, `LGPL-3.0-only`
//! through the `malachite` tree, and six unmaintained advisories whose own text
//! says no safe upgrade exists. `cargo deny` refuses it on both counts, and
//! ADR-0017 §3 is explicit that a licence is not admitted merely to turn CI
//! green.
//!
//! That price bought two of the validator's thirty-four checks, both of them
//! about whether embedded *code* parses rather than whether the *bundle*
//! conforms. See `Cargo.toml` for the full measurement.
//!
//! # Subcommand names are upstream's
//!
//! `trust`, `links` and `diff` match the `okf` CLI's own names for the same
//! operations, so somebody who knows that tool already knows this one. The
//! library is called **in-process**; Roteiro is a self-contained offline binary
//! and requiring `okf` on `PATH` would reintroduce exactly the coupling the
//! vendored interop fixtures exist to avoid.

use std::path::Path;

use okf_core::{Bundle, TrustTier};
use serde::Serialize;

/// Why a bundle could not be inspected.
///
/// One variant today: every failure here is "the path is not a bundle we could
/// load". The underlying [`okf_core::BundleError`] is rendered into the message
/// rather than wrapped, so this type stays free of the dependency in its public
/// shape.
///
/// `#[non_exhaustive]` because that set is closed by nothing but current
/// implementation — unlike [`super::Actor`], whose three variants are closed by
/// §7 of the specification and which is deliberately exhaustive for that reason.
/// A second failure mode here (a bundle that loads but declares an OKF version
/// this crate cannot read, say) is an ordinary addition, and these crates are
/// published, so it must not be a breaking change.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum InspectError {
    /// The path could not be loaded as an OKF bundle.
    #[error("`{path}` is not a readable OKF bundle: {detail}")]
    Unreadable {
        /// The path as the caller gave it.
        path: String,
        /// What `okf-core` said went wrong.
        detail: String,
    },
    /// `--today` was given a value that is not an ISO `YYYY-MM-DD` date.
    ///
    /// Refused rather than silently falling back to the real clock: the flag
    /// exists so a run is reproducible, and a typo that quietly restored
    /// today's date would make a green pipeline mean nothing.
    #[error("`{given}` is not an ISO date (expected YYYY-MM-DD)")]
    BadDate {
        /// The value as the caller gave it.
        given: String,
    },
    /// The host clock could not be read and no `--today` was given.
    #[error("cannot read the current date; pass --today YYYY-MM-DD")]
    NoClock,
}

/// Load a bundle, naming the path in the error rather than only the cause.
pub(super) fn load(root: &Path) -> Result<Bundle, InspectError> {
    Bundle::load(root).map_err(|e| InspectError::Unreadable {
        path: root.display().to_string(),
        detail: e.to_string(),
    })
}

/// A concept's trust claim, as the bundle states it.
#[derive(Debug, Clone, Serialize)]
pub struct ConceptTrust {
    /// The concept's path within the bundle, minus `.md`.
    pub id: String,
    /// §5.3's tier: `human-reviewed`, `machine-confirmed` or `unverified`.
    pub tier: &'static str,
    /// The lifecycle `status` §5.4 resolves for this concept.
    pub status: String,
    /// Every actor named in `verified`, in the order the document wrote them.
    ///
    /// Present even when the tier is `unverified`: an event with an unparseable
    /// timestamp does not count toward the tier but is still an attribution the
    /// bundle made, and dropping it would hide *why* the tier came out low.
    pub verified_by: Vec<String>,
    /// The `stale_after` timestamp exactly as the document wrote it, if any.
    pub stale_after: Option<String>,
    /// Whether `today >= stale_after` (§5.4).
    ///
    /// Independent of `tier`: a concept can be human-reviewed *and* stale, and
    /// that combination is the one most worth seeing before an import, because
    /// the tier alone reads as reassurance.
    pub stale: bool,
}

/// What a bundle claims about its own trustworthiness.
///
/// This is the answer to "should I trust this bundle", stated per concept and in
/// aggregate, and it is deliberately a **plain data type over a path**: it is
/// exactly the information a consent prompt wants at the moment it asks, and
/// nothing here needs the import machinery to have run first.
#[derive(Debug, Clone, Serialize)]
pub struct TrustSummary {
    /// The bundle root, as the caller named it.
    pub root: String,
    /// The `okf_version` the root `index.md` declares (§10), if any.
    pub okf_version: Option<String>,
    /// Concepts read, excluding the reserved `index.md` / `log.md` files.
    pub total: usize,
    /// Concepts carrying at least one valid `human:` verifier.
    pub human_reviewed: usize,
    /// Concepts verified only by non-`human:` actors.
    pub machine_confirmed: usize,
    /// Concepts with no valid `verified` event.
    pub unverified: usize,
    /// Concepts whose `stale_after` has passed, as of `today`.
    pub stale: usize,
    /// The date staleness was judged against, as `YYYY-MM-DD`.
    ///
    /// Always reported, whether it came from `--today` or the host clock, so a
    /// captured summary says what it was true *of*. A tiered count with no date
    /// beside it cannot be compared with the same bundle read a month later.
    pub today: String,
    /// Every concept, in bundle order.
    pub concepts: Vec<ConceptTrust>,
}

/// Derive [`TrustSummary`] for the bundle at `root`.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if the path is not a loadable OKF bundle,
/// [`InspectError::BadDate`] if `today` is given and is not an ISO date, and
/// [`InspectError::NoClock`] if `today` is `None` and the host date cannot be
/// read. The last is the one worth handling deliberately: it is the only way
/// this fails on a perfectly good bundle, and the remedy is to pass `today`.
pub fn trust_summary(root: &Path, today: Option<&str>) -> Result<TrustSummary, InspectError> {
    let today = resolve_today(today)?;
    Ok(summarise_trust(
        &load(root)?,
        &root.display().to_string(),
        today,
    ))
}

/// The date staleness is judged against: `--today` when given, else the host's
/// UTC date.
///
/// Separated out because it is the only non-deterministic input in this module,
/// and every report that mentions staleness takes it the same way.
fn resolve_today(given: Option<&str>) -> Result<okf_core::Date, InspectError> {
    match given {
        Some(raw) => okf_core::Date::parse(raw).ok_or_else(|| InspectError::BadDate {
            given: raw.to_owned(),
        }),
        None => okf_core::Date::today_utc().ok_or(InspectError::NoClock),
    }
}

/// The bundle-in-hand half of [`trust_summary`].
///
/// Split out so a caller that has already loaded a [`Bundle`] — to validate it,
/// or to ask a person whether to import it — pays for the directory walk once.
#[must_use]
pub fn summarise_trust(bundle: &Bundle, root: &str, today: okf_core::Date) -> TrustSummary {
    let mut summary = TrustSummary {
        root: root.to_owned(),
        okf_version: bundle.okf_version().map(ToOwned::to_owned),
        total: bundle.concepts().len(),
        human_reviewed: 0,
        machine_confirmed: 0,
        unverified: 0,
        stale: 0,
        today: today.to_string(),
        concepts: Vec::with_capacity(bundle.concepts().len()),
    };
    for concept in bundle.concepts() {
        let tier = concept.trust_tier();
        match tier {
            TrustTier::HumanReviewed => summary.human_reviewed += 1,
            TrustTier::MachineConfirmed => summary.machine_confirmed += 1,
            TrustTier::Unverified => summary.unverified += 1,
        }
        let stale = concept.is_stale_on(today);
        if stale {
            summary.stale += 1;
        }
        summary.concepts.push(ConceptTrust {
            id: concept.id.to_string(),
            tier: tier.as_str(),
            status: concept.status().to_string(),
            stale_after: concept
                .document
                .frontmatter
                .stale_after()
                .map(|d| d.to_string()),
            stale,
            verified_by: concept
                .document
                .frontmatter
                .verified()
                .into_iter()
                .filter_map(|v| v.by.map(|by| by.as_str().to_owned()))
                .collect(),
        });
    }
    summary
}

/// A markdown link that names a concept the bundle does not contain.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct BrokenLink {
    /// The concept whose body carries the link.
    pub from: String,
    /// The link target, exactly as written.
    pub target: String,
}

/// Whether an emitted bundle's internal links resolve.
///
/// Roteiro's own link checking (`roteiro check`) covers the **graph** and the
/// **rendered site**. Neither looks at an emitted OKF bundle, which is a third
/// artefact produced by a third code path — the one ADR-0021 records guessing
/// wrong for 43 links.
#[derive(Debug, Clone, Serialize)]
pub struct LinkReport {
    /// The bundle root, as the caller named it.
    pub root: String,
    /// Concepts read.
    pub concepts: usize,
    /// Internal concept links found across every body.
    pub links: usize,
    /// Those that resolve to no concept in the bundle.
    pub broken: Vec<BrokenLink>,
}

impl LinkReport {
    /// `true` when every internal link resolves.
    #[must_use]
    pub const fn is_clean(&self) -> bool {
        self.broken.is_empty()
    }
}

/// Resolve every internal link in the bundle at `root`.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if the path is not a loadable OKF bundle.
pub fn link_report(root: &Path) -> Result<LinkReport, InspectError> {
    let bundle = load(root)?;
    let links = bundle
        .concepts()
        .iter()
        .map(|c| bundle.links_from(&c.id).len())
        .sum();
    Ok(LinkReport {
        root: root.display().to_string(),
        concepts: bundle.concepts().len(),
        links,
        broken: bundle
            .broken_links()
            .into_iter()
            .map(|(from, target)| BrokenLink {
                from: from.to_string(),
                target,
            })
            .collect(),
    })
}

/// A concept whose trust tier or lifecycle status moved between two bundles.
#[derive(Debug, Clone, Serialize)]
pub struct TrustMove {
    /// The concept that moved.
    pub id: String,
    /// `(before, after)` tiers, when the tier changed.
    pub tier: Option<(String, String)>,
    /// `(before, after)` statuses, when the status changed.
    pub status: Option<(String, String)>,
}

/// What changed between two bundles, semantically rather than by bytes.
///
/// ADR-0021 made `render okf` byte-deterministic specifically so "a consumer can
/// diff two downloads and learn something". This is that diff, and it is the
/// first thing in the workspace to exercise the determinism: `review --base`
/// diffs code, not bundles.
///
/// A **rename** is the interesting field. A textual diff of two bundles reports
/// a moved concept as one deletion and one unrelated addition; this reports it
/// as a rename, which is the difference between "we lost a concept" and "we
/// moved one".
#[derive(Debug, Clone, Serialize)]
pub struct DiffReport {
    /// The bundle taken as "before".
    pub before: String,
    /// The bundle taken as "after".
    pub after: String,
    /// Concepts present only in `after`.
    pub added: Vec<String>,
    /// Concepts present only in `before`.
    pub removed: Vec<String>,
    /// Concepts whose path changed, as `(from, to)`.
    pub renamed: Vec<(String, String)>,
    /// Concepts whose body changed.
    pub content_changed: Vec<String>,
    /// Concepts whose frontmatter keys changed.
    pub frontmatter_changed: Vec<String>,
    /// Concepts whose tier or status moved. The one to read first.
    pub trust_changed: Vec<TrustMove>,
    /// Links that broke between `before` and `after`, as `(concept, target)`.
    pub links_broken: Vec<(String, String)>,
    /// Links that were broken in `before` and resolve in `after`.
    pub links_mended: Vec<(String, String)>,
}

impl DiffReport {
    /// `true` when the two bundles are semantically identical.
    #[must_use]
    pub fn is_unchanged(&self) -> bool {
        self.added.is_empty()
            && self.removed.is_empty()
            && self.renamed.is_empty()
            && self.content_changed.is_empty()
            && self.frontmatter_changed.is_empty()
            && self.trust_changed.is_empty()
            && self.links_broken.is_empty()
            && self.links_mended.is_empty()
    }
}

/// Compare two bundles semantically.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if either path is not a loadable OKF bundle.
pub fn diff_report(before: &Path, after: &Path) -> Result<DiffReport, InspectError> {
    let a = load(before)?;
    let b = load(after)?;
    let d = okf_core::bundle_diff(&a, &b);
    let ids = |v: Vec<okf_core::ConceptId>| v.iter().map(ToString::to_string).collect::<Vec<_>>();
    let pairs = |v: Vec<(okf_core::ConceptId, String)>| {
        v.into_iter()
            .map(|(id, t)| (id.to_string(), t))
            .collect::<Vec<_>>()
    };
    Ok(DiffReport {
        before: before.display().to_string(),
        after: after.display().to_string(),
        added: ids(d.added),
        removed: ids(d.removed),
        renamed: d
            .renamed
            .into_iter()
            .map(|r| (r.from.to_string(), r.to.to_string()))
            .collect(),
        content_changed: ids(d.content),
        frontmatter_changed: d.frontmatter.iter().map(|c| c.id.to_string()).collect(),
        trust_changed: d
            .trust
            .into_iter()
            .map(|t| TrustMove {
                id: t.id.to_string(),
                tier: t
                    .tier
                    .map(|(a, b)| (a.as_str().to_owned(), b.as_str().to_owned())),
                status: t.status.map(|(a, b)| (a.to_string(), b.to_string())),
            })
            .collect(),
        links_broken: pairs(d.broken_links),
        links_mended: pairs(d.mended_links),
    })
}

/// One code block that did not parse.
#[derive(Debug, Clone, Serialize)]
pub struct SyntaxFinding {
    /// The concept the block belongs to.
    pub concept: String,
    /// The concept's file, relative to the bundle root.
    pub path: String,
    /// 1-indexed line of the block's opening fence within that file's body,
    /// when it could be determined.
    ///
    /// `None` for a computation whose code this crate could not locate in the
    /// body — an indented block with no `# Computation` heading to anchor it.
    /// Reporting a confident `1` there was worse than reporting nothing: it sent
    /// a reader to the frontmatter for a fault further down the file.
    pub line: Option<usize>,
    /// The language the block was tagged with, canonicalised.
    pub language: String,
    /// What the parser said.
    pub message: String,
}

/// The result of syntax-checking a bundle's code blocks.
///
/// `checked` and `skipped` are both reported, deliberately. A language with no
/// backend compiled in is *not checked* rather than *clean*, and a report that
/// conflated the two would be a check that passes by not looking.
#[derive(Debug, Clone, Serialize)]
pub struct SyntaxReport {
    /// The bundle root, as the caller named it.
    pub root: String,
    /// `computations` or `all-blocks` — what was looked at.
    pub scope: &'static str,
    /// Blocks a backend actually parsed.
    pub checked: usize,
    /// Blocks left alone, for any of three reasons: the block carried no
    /// language tag, this build has no backend for the language it carried, or
    /// the computation named a file rather than inlining its code.
    ///
    /// All three are "not looked at" rather than "looked at and clean", which is
    /// the distinction the whole report exists to keep.
    pub skipped: usize,
    /// The languages this build can check, so a reader can tell why.
    pub languages: Vec<String>,
    /// Findings, in bundle order.
    pub findings: Vec<SyntaxFinding>,
}

impl SyntaxReport {
    /// `true` when nothing failed to parse.
    #[must_use]
    pub const fn passed(&self) -> bool {
        self.findings.is_empty()
    }
}

/// The language an untagged computation block should be read as.
///
/// Only `bigquery` is mapped, and only because the corpus justifies it: every
/// `runtime:` in the four bundles published with the specification is
/// `bigquery`, and the spec's own Attested Computation example writes its query
/// as an *indented* block, which carries no info string. Without this the one
/// case that matters most would never be checked.
///
/// Deliberately not a general runtime→language table. Inventing a mapping for
/// runtimes nobody has written yet is how a reader ends up with a confident
/// diagnostic about a language the author never claimed.
fn language_for_runtime(runtime: Option<&str>) -> Option<&'static str> {
    // Case-insensitive, because every other tag here is: `Language::from_tag`
    // lowercases, so `runtime: BigQuery` reading differently from `bigquery`
    // would be an inconsistency inside one function's worth of code.
    match runtime.map(|r| r.trim().to_ascii_lowercase()).as_deref() {
        Some("bigquery") => Some("sql"),
        _ => None,
    }
}

/// Syntax-check the code blocks in a bundle.
///
/// With `computations_only`, just the bodies of Attested Computations — the
/// concepts that declare a `runtime:` and that an agent is expected to *run*, so
/// the ones where "does this parse" is a question about the bundle rather than
/// about its prose. Otherwise every fenced block in every document.
///
/// Findings are the checker's, not conformance: a bundle can be perfectly
/// conformant and contain a code sample that does not parse, which is why this
/// is its own command rather than part of validation.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if the path is not a loadable OKF bundle.
pub fn syntax_report(root: &Path, computations_only: bool) -> Result<SyntaxReport, InspectError> {
    let bundle = load(root)?;
    let languages = rto_okf_syntax::checkable_languages()
        .into_iter()
        .map(|l| l.as_str().to_owned())
        .collect();
    let mut report = SyntaxReport {
        root: root.display().to_string(),
        scope: if computations_only {
            "computations"
        } else {
            "all-blocks"
        },
        checked: 0,
        skipped: 0,
        languages,
        findings: Vec::new(),
    };

    for concept in bundle.concepts() {
        let rel = concept
            .path
            .strip_prefix(bundle.root())
            .unwrap_or(&concept.path)
            .display()
            .to_string();

        if computations_only {
            let Some(computation) = concept.attested_computation() else {
                continue;
            };
            let okf_core::ComputationSource::Inline(inline) = &computation.computation else {
                // A `computation:` file reference is checked by whatever owns
                // that file, and a `Missing` one has no code to check at all.
                // Counted as **skipped** rather than passed over silently: a
                // bundle whose computations all name files would otherwise
                // report "0 checked, 0 skipped" and print "nothing to check",
                // which reads as "there were none" when there were several.
                report.skipped += 1;
                continue;
            };
            // An indented block carries no info string, so fall back to the
            // declared runtime — see `language_for_runtime`.
            let tag = inline
                .language
                .as_deref()
                .or_else(|| language_for_runtime(computation.runtime.as_deref()))
                .unwrap_or("");
            let line = computation_line(&concept.document.body, &inline.code);
            record(
                &mut report,
                &concept.id.to_string(),
                &rel,
                line,
                tag,
                &inline.code,
            );
        } else {
            for block in rto_okf_syntax::extract_fenced_code_blocks(&concept.document.body) {
                let tag = block.language.as_deref().unwrap_or("");
                record(
                    &mut report,
                    &concept.id.to_string(),
                    &rel,
                    Some(block.start_line),
                    tag,
                    &block.code,
                );
            }
        }
    }

    Ok(report)
}

/// Where a computation's code starts in its document.
///
/// The fenced case is exact: the same extractor the all-blocks path uses finds
/// the block whose contents are the computation's, and reports its opening
/// fence. The indented case cannot be — `okf-core` dedents the code, so it no
/// longer matches the file byte for byte — and the `# Computation` heading is the
/// honest anchor there: it is where a reader should look, even though it is not
/// where the parser stopped.
///
/// `None` rather than a confident `1` when neither is found. Pointing a reader at
/// the frontmatter for a fault further down the file is worse than admitting the
/// line is unknown.
fn computation_line(body: &str, code: &str) -> Option<usize> {
    let wanted = code.trim();
    if let Some(block) = rto_okf_syntax::extract_fenced_code_blocks(body)
        .into_iter()
        .find(|b| b.code.trim() == wanted)
    {
        return Some(block.start_line);
    }
    body.lines().enumerate().find_map(|(i, l)| {
        l.trim_start()
            .strip_prefix('#')
            .is_some_and(|rest| rest.trim().eq_ignore_ascii_case("computation"))
            .then_some(i + 1)
    })
}

/// Check one block and fold the outcome into the report.
fn record(
    report: &mut SyntaxReport,
    concept: &str,
    path: &str,
    line: Option<usize>,
    tag: &str,
    code: &str,
) {
    let language = rto_okf_syntax::Language::from_tag(tag);
    if !rto_okf_syntax::is_checkable(language) {
        report.skipped += 1;
        return;
    }
    report.checked += 1;
    if let Err(err) = rto_okf_syntax::check_syntax(tag, code) {
        report.findings.push(SyntaxFinding {
            concept: concept.to_owned(),
            path: path.to_owned(),
            line,
            language: err.language.clone(),
            message: err.to_string(),
        });
    }
}

/// One concept's Attested Computation (§10), as the bundle declares it.
#[derive(Debug, Clone, Serialize)]
pub struct ComputationEntry {
    /// The concept carrying the contract.
    pub concept: String,
    /// The bundle-relative file it lives in.
    pub path: String,
    /// §10's `runtime`, which decides how everything else is interpreted.
    ///
    /// `None` is a conformance error, not an absence — the spec makes it
    /// REQUIRED — and it is surfaced here rather than skipped so a listing and
    /// `okf validate` agree about what the bundle contains.
    pub runtime: Option<String>,
    /// `inline`, `file` or `missing`.
    pub source: &'static str,
    /// The file named by a `computation:` key, when `source` is `file`.
    pub file: Option<String>,
    /// The fenced language of an inline block, when it declared one.
    pub language: Option<String>,
    /// Lines of code in an inline block.
    pub lines: Option<usize>,
    /// The named holes an agent may fill.
    pub parameters: Vec<String>,
    /// Whether an executor is declared.
    pub has_executor: bool,
    /// Whether an attester is declared.
    pub has_attester: bool,
    /// `true` when the concept carries **both** an inline block and a
    /// `computation:` file key.
    ///
    /// The spec asks for one or the other, so the two halves can disagree with
    /// nothing to arbitrate between them. Listed rather than merely counted
    /// because the fix is per concept.
    pub redundant_inline: bool,
}

/// Every Attested Computation a bundle declares.
#[derive(Debug, Clone, Serialize)]
pub struct ComputationReport {
    /// The bundle root, as the caller named it.
    pub root: String,
    /// Concepts read.
    pub concepts: usize,
    /// Concepts carrying a computation contract.
    pub computations: usize,
    /// Of those, how many carry the code inline.
    pub inline: usize,
    /// Of those, how many name a file instead.
    pub file: usize,
    /// Of those, how many declare neither — an incomplete contract.
    pub missing: usize,
    /// Every distinct `runtime`, sorted.
    pub runtimes: Vec<String>,
    /// The contracts themselves, in bundle order.
    pub entries: Vec<ComputationEntry>,
}

impl ComputationReport {
    /// Whether every contract found is complete: a runtime, and code somewhere.
    ///
    /// This is what `--check` gates on. A bundle with **no** computations is
    /// clean by this measure, which is the right answer: §10 is optional, and
    /// failing a bundle for not using an optional feature would make the gate
    /// unusable on the three of four published bundles that declare none.
    #[must_use]
    pub fn is_clean(&self) -> bool {
        self.incomplete() == 0
    }

    /// Contracts that are declared but not usable: no `runtime`, no code, or
    /// both an inline block and a file with nothing to arbitrate between them.
    #[must_use]
    pub fn incomplete(&self) -> usize {
        self.entries
            .iter()
            .filter(|e| e.runtime.is_none() || e.source == "missing" || e.redundant_inline)
            .count()
    }
}

/// List the Attested Computations in the bundle at `root`.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if the path is not a loadable OKF bundle.
pub fn computation_report(root: &Path) -> Result<ComputationReport, InspectError> {
    let bundle = load(root)?;
    let mut report = ComputationReport {
        root: root.display().to_string(),
        concepts: bundle.concepts().len(),
        computations: 0,
        inline: 0,
        file: 0,
        missing: 0,
        runtimes: Vec::new(),
        entries: Vec::new(),
    };
    let mut runtimes = std::collections::BTreeSet::new();

    for concept in bundle.concepts() {
        let Some(computation) = concept.attested_computation() else {
            continue;
        };
        report.computations += 1;
        if let Some(runtime) = computation.runtime.as_deref() {
            runtimes.insert(runtime.to_owned());
        }
        let (source, file, language, lines) = match &computation.computation {
            okf_core::ComputationSource::Inline(inline) => {
                report.inline += 1;
                (
                    "inline",
                    None,
                    inline.language.clone(),
                    Some(inline.code.lines().count()),
                )
            }
            okf_core::ComputationSource::File(path) => {
                report.file += 1;
                ("file", Some(path.clone()), None, None)
            }
            okf_core::ComputationSource::Missing => {
                report.missing += 1;
                ("missing", None, None, None)
            }
        };
        report.entries.push(ComputationEntry {
            concept: concept.id.to_string(),
            path: concept
                .path
                .strip_prefix(bundle.root())
                .unwrap_or(&concept.path)
                .display()
                .to_string(),
            runtime: computation.runtime.clone(),
            source,
            file,
            language,
            lines,
            // An unnamed parameter is dropped rather than rendered as a hole:
            // §10 requires the name, so `okf validate` is what reports its
            // absence, and repeating it here as an empty slot in a listing would
            // read as a parameter called "".
            parameters: computation
                .parameters
                .iter()
                .filter_map(|p| p.name.clone())
                .collect(),
            has_executor: computation.executor.is_some(),
            has_attester: computation.attester.is_some(),
            redundant_inline: computation.has_redundant_inline,
        });
    }
    report.runtimes = runtimes.into_iter().collect();
    Ok(report)
}

/// A file a bundle carries that is not one of its concepts.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct BundleFile {
    /// Bundle-relative path.
    pub path: String,
    /// Size in bytes, or `None` when it could not be read.
    ///
    /// Distinguished from zero rather than conflated with it, because an empty
    /// file and an unstattable one are different facts and only one of them is
    /// reassuring — the same reason the walk reports what it could not open. A
    /// caller summing sizes treats `None` as contributing nothing; a caller
    /// printing one says so.
    pub bytes: Option<u64>,
    /// Lowercased extension, or `""` when the file has none.
    pub extension: String,
}

/// What a bundle carries that is not one of its concepts.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize)]
pub struct BundleContents {
    /// Every non-markdown file, ordered by path.
    pub files: Vec<BundleFile>,
    /// Everything the walk could not inspect, so the inventory above is
    /// **incomplete**.
    ///
    /// Reported rather than swallowed. An inventory that answers "none" because
    /// something would not open is the same false reassurance this feature exists
    /// to remove — a reader would take silence for absence, which is precisely
    /// what "0 violations" over an unread PDF did.
    ///
    /// Three failures land here, not one: a directory that will not list, a
    /// directory entry that will not yield, and an entry whose type cannot be
    /// read. The first was the obvious case and the other two are the same defect
    /// one level in — `entries.flatten()` and a `let Ok(kind) = … else continue`
    /// each discard an error and leave `is_complete()` saying the walk saw
    /// everything.
    ///
    /// A file whose **size** cannot be read is not here: the file itself was
    /// seen, named and reported, so the inventory is complete. See
    /// [`BundleFile::bytes`].
    pub unreadable: Vec<String>,
}

impl BundleContents {
    /// Whether the walk saw everything it tried to.
    #[must_use]
    pub fn is_complete(&self) -> bool {
        self.unreadable.is_empty()
    }
}

/// Every file in the bundle that is not markdown.
///
/// **Nothing here is opened.** The path, the size and the extension come from
/// the directory entry and its metadata; the bytes are never read, so this adds
/// no parser and no attack surface of its own.
///
/// It exists because a bundle is **not** markdown, whatever the four published
/// ones happen to contain: `okf-core`'s `resolve_path_field` resolves a
/// frontmatter path to any file with `is_file()` and no extension filter, and
/// §10's `computation:` names a file. So a conformant bundle can cite a document
/// nobody here can read — and until now every report we produced would call that
/// bundle clean without mentioning the document existed (ADR-0024).
///
/// **What it costs**, because it looks cheaper than it is and has more than one
/// caller: one walk of this repository's own 9,633-file bundle measures **5.9 ms
/// warm** (40 ms cold), against the `Bundle::load` of the same bundle at
/// **1.29 s** — which every caller has already paid before reaching here, since
/// there is nothing to report about a bundle that did not load. Two walks in a
/// run is under one percent of what the run already spent, so this is not cached.
/// If that ratio changes, cache it then and put the new number here.
///
/// Symlinked directories are **not** followed: this walks a directory a peer
/// controls, and `loop -> ..` inside one would otherwise never terminate.
/// Entries are classified with `file_type()`, which reads the directory entry
/// rather than the link's target, and a symlink is counted as the file it is.
///
/// The walk keeps its own stack rather than recursing. Review raised a deep-tree
/// stack overflow, and it does **not** reproduce — `PATH_MAX` caps the depth an
/// attacker can build (509 here) and `Bundle::load` refuses such a tree before
/// this ever runs, with `File name too long`. It is iterative anyway, because
/// "bounded by the filesystem's path limit" is a platform accident rather than a
/// property of this function, and an explicit stack costs nothing to make it one.
#[must_use]
pub fn bundle_files(root: &Path) -> BundleContents {
    let mut out = BundleContents::default();
    let mut stack = vec![root.to_path_buf()];
    while let Some(dir) = stack.pop() {
        let Ok(entries) = std::fs::read_dir(&dir) else {
            out.unreadable.push(relative(root, &dir));
            continue;
        };
        for entry in entries {
            // Both of these were `flatten()` and `else continue`, which discard
            // an error and then let `is_complete()` claim the walk saw
            // everything — the swallowed-failure defect this type exists to
            // report, one level further in.
            let Ok(entry) = entry else {
                out.unreadable.push(relative(root, &dir));
                continue;
            };
            let path = entry.path();
            let Ok(kind) = entry.file_type() else {
                out.unreadable.push(relative(root, &path));
                continue;
            };
            if kind.is_dir() {
                stack.push(path);
                continue;
            }
            let extension = path
                .extension()
                .and_then(|e| e.to_str())
                .map(str::to_ascii_lowercase)
                .unwrap_or_default();
            if extension == "md" {
                continue;
            }
            out.files.push(BundleFile {
                path: relative(root, &path),
                bytes: std::fs::symlink_metadata(&path).map(|m| m.len()).ok(),
                extension,
            });
        }
    }
    // Sorted so two reads of one bundle, and two bundles with the same contents,
    // report identically — the same determinism `render okf` guarantees. The
    // stack alone gives no order at all, since it pops depth-first in whatever
    // order the filesystem returned each directory.
    out.files.sort_by(|a, b| a.path.cmp(&b.path));
    // A directory that failed to yield several entries names itself once per
    // failure, and the count is not information a reader can act on.
    out.unreadable.sort();
    out.unreadable.dedup();
    out
}

/// A bundle-relative path, with `/` separators on every platform.
///
/// `Path::display()` alone emits `\` on Windows, and this string is compared
/// against the `/`-separated paths a bundle's own frontmatter and links use — so
/// on Windows an inventory entry would not match the document that cited it.
///
/// A path that is somehow **not** under `root` is rendered as the bare file name
/// rather than falling back to the whole path: the fallback would print an
/// absolute path from the host into a report about a peer's bundle, which is a
/// small disclosure to make in a message whose subject is what a stranger can
/// see.
///
/// The **root itself** renders as `"."`, never as the empty string. It reaches
/// here when the bundle root is the thing that will not list, and `strip_prefix`
/// against itself yields an empty path — so the report read `1 entry could not be
/// inspected:` followed by a blank line, which is a worse failure than the one
/// being reported, in the one message whose whole job is to say what could not be
/// seen. `"."` is the spelling `AdrHome::dir` already uses for "the root" here.
fn relative(root: &Path, path: &Path) -> String {
    let rel = path
        .strip_prefix(root)
        .unwrap_or_else(|_| Path::new(path.file_name().unwrap_or(std::ffi::OsStr::new("?"))));
    let joined = rel
        .components()
        .map(|c| c.as_os_str().to_string_lossy())
        .collect::<Vec<_>>()
        .join("/");
    // The root itself yields an empty path from `strip_prefix` against itself.
    if joined.is_empty() {
        ".".to_owned()
    } else {
        joined
    }
}

/// What a bundle is, in one answer.
///
/// Composed from the reports the other commands already produce rather than
/// re-deriving anything: this is the command you run *first*, on a bundle
/// somebody handed you, to decide which of the others is worth running.
#[derive(Debug, Clone, Serialize)]
pub struct BundleInfo {
    /// The bundle root, as the caller named it.
    pub root: String,
    /// The `okf_version` the root `index.md` declares (§10), if any.
    ///
    /// Absent is conformant — §8 and §12 make it MAY — so this is reported and
    /// never warned about.
    pub okf_version: Option<String>,
    /// The bundle's title, from `index.md`.
    pub title: Option<String>,
    /// Concepts, excluding the reserved `index.md` / `log.md`.
    pub concepts: usize,
    /// Trust tiers and staleness, as of `today`.
    pub trust: TrustSummary,
    /// How many concepts carry each `status`, sorted by status.
    pub statuses: Vec<(String, usize)>,
    /// Internal links, and how many resolve to nothing.
    pub links: (usize, usize),
    /// Attested Computations, and how many are incomplete.
    pub computations: (usize, usize),
    /// Every distinct computation `runtime`, sorted.
    pub runtimes: Vec<String>,
    /// Files the bundle carries that are not concepts, and any directory the
    /// walk could not list — see [`bundle_files`].
    ///
    /// Reported whether or not there are any, because "no unscreenable files" is
    /// information and a line that appears only sometimes is one a reader learns
    /// to stop looking for.
    pub files: BundleContents,
}

/// Summarise the bundle at `root`.
///
/// # Errors
///
/// [`InspectError::Unreadable`] if the path is not a loadable OKF bundle,
/// [`InspectError::BadDate`] if `today` is given and is not an ISO date, and
/// [`InspectError::NoClock`] if `today` is `None` and the host date cannot be
/// read — the same three as [`trust_summary`], which this calls.
pub fn bundle_info(root: &Path, today: Option<&str>) -> Result<BundleInfo, InspectError> {
    let today = resolve_today(today)?;
    let bundle = load(root)?;
    let trust = summarise_trust(&bundle, &root.display().to_string(), today);
    let links = link_report(root)?;
    let computations = computation_report(root)?;

    let mut statuses: std::collections::BTreeMap<String, usize> = std::collections::BTreeMap::new();
    for concept in bundle.concepts() {
        *statuses.entry(concept.status().to_string()).or_default() += 1;
    }

    Ok(BundleInfo {
        root: root.display().to_string(),
        okf_version: bundle.okf_version().map(ToOwned::to_owned),
        title: bundle_title(&bundle),
        concepts: bundle.concepts().len(),
        trust,
        statuses: statuses.into_iter().collect(),
        links: (links.links, links.broken.len()),
        computations: (computations.computations, computations.incomplete()),
        runtimes: computations.runtimes,
        files: bundle_files(root),
    })
}

/// The bundle's own title, from the `title` of its root `index.md`.
///
/// Read through `Document::parse` — the same parser `Bundle::load` uses — rather
/// than a second reader of the same bytes, so the two cannot disagree about what
/// the file says. `okf-core` exposes the index only as a path, so this re-reads
/// one small file; that is cheap next to the directory walk, and a bundle whose
/// index is unreadable simply has no title here, because `okf validate` is what
/// reports a broken index.
fn bundle_title(bundle: &Bundle) -> Option<String> {
    let path = bundle.index_files().first()?;
    let text = std::fs::read_to_string(path).ok()?;
    let document = okf_core::Document::parse(&text).ok()?;
    document
        .frontmatter
        .title()
        .map(std::borrow::Cow::into_owned)
}