tix-tracker 0.12.0

//! Estimate mode: the shared unit conversion, and the series estimate mode folds
//! (mission `burndown-scope-analytics-01M3C9J1`, WP03 T013–T015).
//!
//! # What estimate mode is, and what it is not
//!
//! Count mode ([`crate::analytics::series`]) values every counted contribution at
//! `1`. Estimate mode runs the **same fold over the same recorded contributions**
//! and values each one at the estimated size of the issue it belongs to, in one
//! explicitly selected unit:
//!
//! | the fold sees | count mode | estimate mode |
//! |---|---|---|
//! | a recorded scope addition | `+1` on the day | `+` the issue's estimate |
//! | a recorded completion | `+1` on the day | `+` the issue's estimate |
//! | a contribution the record cannot quantify (`delta: None`) | nothing; the day is limited | nothing; the day is limited |
//! | a recorded estimate change | nothing | nothing; the day is limited, and it is reported |
//! | any other recorded event | nothing; reported | nothing; reported |
//!
//! The two modes therefore agree on the **days**, on the provenance of every day and
//! on what they can and cannot answer; they differ only in what a contribution is
//! worth. On a project where every counted contribution is worth the same `n`, the
//! estimate series is exactly `n` times the count series — the parity the package's
//! tests anchor.
//!
//! # The conversion is the crate's, not a second rule (T013, C-003)
//!
//! An issue's size is read by [`EstimateValue::parse`] (the raw text kept verbatim;
//! human duration words like `day` fold to the board symbol `d`, and each term is
//! converted separately) and turned into the series' unit by
//! [`EstimateValue::converted_to`], whose arithmetic is
//! [`crate::wip::WipConfig::convert`] — the **same** board registry `tix capacity`
//! converts through, resolved from [`Config::default_config`] once per series
//! ([`EstimateConversion::resolve`]). Nothing here invents a unit, a factor or a
//! rounding rule, and a unit the board does not declare is reported rather than
//! guessed.
//!
//! # A missing or mixed unit is a finding, not a number (T015)
//!
//! * A series whose **unit the board does not declare** cannot count anything: the
//!   fold returns no point at all and says why (C-003's "never invent arithmetic").
//! * A member whose stated estimate **cannot be converted** contributes nothing, is
//!   reported once per (reason, unit, field) group, and limits the coverage of every
//!   day its contributions fall on.
//! * An **unestimated** member is not a zero either: its contributions have no size,
//!   which is a finding and a coverage marker, never a `0` in the sum.
//!
//! Every number the series publishes is a **lower bound over the contributions the
//! shared conversion could value**, exactly as [`crate::capacity::calculate`]
//! publishes `committed` beside its `uncounted_issues`/`unestimated_issues` counts —
//! with the coverage marker and the finding standing in for the counts a
//! [`DailyPoint`] cannot carry. A day with no recorded history keeps `None` for its
//! day's changes and is `coverage_limited`, as in count mode; a day whose arithmetic
//! was refused is `coverage_limited` with the finding beside it. Nothing
//! unanswerable is rendered as a zero.
//!
//! # An estimate change is reported, never replayed
//!
//! `estimate_changed` records a before/after pair in its detail. Replaying those
//! pairs into per-day sizes would be a **new formula** (`spec.md` §6: "Escalate any
//! formula that treats missing events as known"), and it would double-count the
//! change against the stated estimate that every other contribution is valued at.
//! The fold therefore values every contribution at the estimate the issue states
//! **now** and reports any re-sizing recorded inside the period, limiting the day it
//! was recorded on: the caveat stays visible and no level is invented.
//!
//! # Determinism (C-007)
//!
//! Members are read in the snapshot's own `(number, filename)` order, the recorded
//! contributions in the index's first-seen order, group tallies are `BTreeMap`s, and
//! the findings are sorted by their own `Ord` — so two runs over one snapshot, in
//! any input order, produce the same bytes.
//!
//! # Findings
//!
//! The estimate fold speaks the **one** vocabulary
//! [`crate::analytics::diagnostics`] fixes — `missing_conversion` for a value the
//! shared conversion could not state, `missing_history` for a contribution the
//! record cannot size, `unclassified_event` for an event that moves no line — and
//! invents no seventh name, so WP02's `diagnostics.rs` needs no edit for this
//! package.
//!
//! # Why the day grid comes from the count fold
//!
//! Which days a series covers is not a property of a mode: it is the scope's period
//! and the recorded days ([`ScopeSnapshot`]). The estimate fold therefore takes its
//! day list from [`ScopeSnapshot::series`]'s count fold — the crate's one period
//! enumeration, including its refusal of a period it cannot enumerate — instead of
//! re-implementing the calendar rules beside it, and it reports a gap of days with
//! no recorded history in the count fold's own sentence, because that fact is the
//! same in both modes.
//!
//! An estimate series therefore carries **everything a count series carries** —
//! the snapshot's own findings, the gap findings — and adds the findings only its
//! valuation can produce. A reader that switches `--mode` on one scope keeps the
//! context and gains the unit caveats.

use std::collections::{BTreeMap, BTreeSet};

use crate::capacity::estimate::EstimateValue;
use crate::config::Config;
use crate::model::Issue;
use crate::wip::WipConfig;

use super::diagnostics::{AnalyticsDiagnostic, AnalyticsDiagnosticKind};
use super::events::{AnalyticsEvent, AnalyticsScope, EventClass};
use super::series::{
    BurndownSeries, Coverage, DailyPoint, ESTIMATE_FORMULA_VERSION, Mode, ScopeSnapshot,
    event_id_key,
};

/// The board's declared estimate units, in the order the board carries them.
///
/// The board is [`Config::default_config`] — the one [`crate::capacity`]'s issue
/// snapshot converts under — so a surface validating a `--unit` before folding asks
/// the same table the fold will ask (C-008). A loaded configuration normalizes the
/// order, so this is stable for one config rather than necessarily the order the file
/// was written in; the finding below quotes it as the declared table.
#[must_use]
pub fn declared_units(config: &Config) -> Vec<String> {
    config.default_config().wip.units.keys().cloned().collect()
}

/// One series' resolved estimate conversion (T013).
///
/// Resolved **once per series**: the board's registry is read at resolve time, and
/// every member's estimate is then converted through [`EstimateConversion::value_of`],
/// so a 10,000-issue series does not re-read the configuration per issue.
#[derive(Debug, Clone)]
pub struct EstimateConversion {
    registry: WipConfig,
    unit: String,
}

impl EstimateConversion {
    /// Resolve the shared conversion for `unit`, or `None` when the board does not
    /// declare that unit.
    ///
    /// `None` is not a fallback: the registry has no factor for the unit, so
    /// [`crate::wip::WipConfig::convert`] would refuse every value anyway (C-003).
    /// The caller reports it once instead of converting per issue.
    #[must_use]
    pub fn resolve(config: &Config, unit: &str) -> Option<Self> {
        let registry = config.default_config().wip.clone();
        let unit = unit.trim();
        registry.factor(unit)?;
        Some(Self {
            registry,
            unit: unit.to_string(),
        })
    }

    /// The unit every value in the series counts in.
    #[must_use]
    pub fn unit(&self) -> &str {
        &self.unit
    }

    /// One issue's stated estimate, read and converted in this unit.
    ///
    /// The crate's one estimate seam: [`EstimateValue::parse`] (raw text kept
    /// verbatim; prose units fold to their board symbol and every term is converted
    /// separately) followed by [`EstimateValue::converted_to`] (the registry's
    /// arithmetic). A blank or absent statement is
    /// [`EstimateValue::unestimated`] — "no estimate" is not an error, and it never
    /// becomes a zero.
    #[must_use]
    pub fn value_of(&self, number: u32, stated: Option<&str>) -> EstimateValue {
        match stated {
            Some(raw) if !raw.trim().is_empty() => {
                EstimateValue::parse(number, raw).converted_to(number, &self.registry, &self.unit)
            }
            _ => EstimateValue::unestimated(),
        }
    }

    /// How one member's stated estimate reads in this unit.
    fn size_of(&self, number: u32, stated: Option<&str>) -> MemberSize {
        let value = self.value_of(number, stated);
        if let Some(size) = value.converted_value {
            return MemberSize::Sized(i64::from(size));
        }
        if value.is_unestimated() {
            return MemberSize::Unestimated;
        }
        // A stated estimate that could not be read or converted. The registry's own
        // finding is kept verbatim (it already names the issue), with its
        // machine-readable kind and its own remedy.
        let Some(finding) = value.diagnostics().first() else {
            // Unreachable for the shared seam: a value that is neither unestimated
            // nor converted carries the finding that refused it. Reported as the
            // conversion problem it must have been rather than dropped.
            return MemberSize::Refused(Refused {
                key: RefusalKey {
                    kind: "missing_conversion",
                    spelled: value.unit().map(str::to_string),
                },
                reason: format!("issue #{number} states `{}`", value.render()),
                remedy: None,
            });
        };
        MemberSize::Refused(Refused {
            key: RefusalKey {
                kind: finding.kind.as_str(),
                spelled: value.unit().map(str::to_string),
            },
            reason: finding.message.clone(),
            remedy: finding.because.clone(),
        })
    }
}

/// Fold `snapshot` into an **estimate-mode** series counting in `unit` (T014/T015).
///
/// `issues` is the same slice [`ScopeSnapshot::build`] read, so a member's stated
/// estimate is looked up in the record the snapshot was folded from and nothing is
/// re-read from a store. `config` supplies the board whose unit table the conversion
/// runs under (the same one `tix capacity` uses).
///
/// The result is a [`BurndownSeries`] — the crate's one series shape — with
/// `mode: Estimate`, `unit: Some(unit)`, the documented
/// [`ESTIMATE_FORMULA_VERSION`], the days and coverage the count fold would report,
/// and this fold's own findings beside them.
#[must_use]
pub fn estimate_series(
    snapshot: &ScopeSnapshot,
    issues: &[Issue],
    config: &Config,
    unit: &str,
) -> BurndownSeries {
    let scope = snapshot.scope();
    let Some(conversion) = EstimateConversion::resolve(config, unit) else {
        let mut diagnostics = snapshot.diagnostics().to_vec();
        diagnostics.push(undeclared_unit(scope, unit.trim(), config));
        diagnostics.sort();
        return empty(scope, unit.trim(), diagnostics);
    };

    // The days come from the count fold: one period enumeration for the whole
    // module, and its refusal when the period cannot be enumerated at all.
    let days = snapshot.series(Mode::Count);
    if days.is_empty() {
        return empty(scope, conversion.unit(), days.diagnostics);
    }

    let sizes = size_members(snapshot, issues, &conversion);
    let valued = value_days(snapshot, &sizes);

    let origin_known = scope.period_start().is_some();
    let global_weak = snapshot.unplaced_events() > 0;
    let mut points = Vec::with_capacity(days.points.len());
    let mut scope_total = 0i64;
    let mut completed = 0i64;
    let mut first_unanswerable: Option<(&str, i64, i64)> = None;
    let mut level_overflow: Option<&str> = None;
    for covered in &days.points {
        let date = covered.date.as_str();
        let observed = snapshot.observed_days().contains(date);
        let added = valued.added.get(date).copied();
        let done = valued.completed.get(date).copied();
        if observed
            && level_overflow.is_none()
            && (!super::series::carry_level(&mut scope_total, added.unwrap_or(0))
                || !super::series::carry_level(&mut completed, done.unwrap_or(0)))
        {
            level_overflow = Some(date);
        }

        let (total, remaining, done_level) = if level_overflow.is_some() {
            (None, None, None)
        } else if origin_known {
            let remaining = scope_total - completed;
            if remaining < 0 {
                first_unanswerable.get_or_insert((date, scope_total, completed));
                (Some(scope_total), None, Some(completed))
            } else {
                (Some(scope_total), Some(remaining), Some(completed))
            }
        } else {
            (None, None, None)
        };

        // The day's provenance is the crate's recorded order — issue number, then entry
        // index — never the order the caller loaded the issues in, so a point, and the
        // document built from it, does not depend on that order. `DailyPoint::event_ids`
        // documents exactly this, and the count fold orders its ids through the same key;
        // without it the estimate fold reported a day's ids first-seen, and two runs over
        // one snapshot disagreed on a reversed input (C-007).
        let mut event_ids = valued.event_ids.get(date).cloned().unwrap_or_default();
        event_ids.sort_by(|left, right| event_id_key(left).cmp(&event_id_key(right)));

        let point = DailyPoint {
            date: date.to_string(),
            scope_total: total,
            remaining,
            completed: done_level,
            scope_added: observed.then(|| added.unwrap_or(0)),
            completions: observed.then(|| done.unwrap_or(0)),
            coverage: Coverage::Known,
            event_ids,
        };
        let weak = global_weak || valued.weak.contains(date);
        points.push(DailyPoint {
            coverage: coverage_of(&point, weak),
            ..point
        });
    }

    let mut diagnostics = snapshot.diagnostics().to_vec();
    diagnostics.extend(gap_findings(scope, &points, snapshot.observed_days()));
    diagnostics.extend(valued.findings(scope, conversion.unit()));
    if let Some((day, total, done)) = first_unanswerable {
        diagnostics.push(level_finding(scope, conversion.unit(), day, total, done));
    }
    if let Some(day) = level_overflow {
        diagnostics.push(
            AnalyticsDiagnostic::new(
                AnalyticsDiagnosticKind::MissingHistory,
                scope.id.clone(),
                format!(
                    "on {day} the carried estimate level exceeded the i64 range, so remaining \
                     work cannot be answered without wrapping or inventing a value"
                ),
            )
            .on(day)
            .with_remedy(
                "reduce the synthetic fixture: persisted estimates use u32 values, so a \
                 realistic project is orders of magnitude below this bound",
            ),
        );
    }
    diagnostics.sort();

    BurndownSeries {
        scope: scope.clone(),
        mode: Mode::Estimate,
        unit: Some(conversion.unit().to_string()),
        points,
        diagnostics,
        formula_version: ESTIMATE_FORMULA_VERSION.to_string(),
    }
}

/// The series an estimate-mode request that cannot be answered returns.
fn empty(
    scope: &AnalyticsScope,
    unit: &str,
    diagnostics: Vec<AnalyticsDiagnostic>,
) -> BurndownSeries {
    BurndownSeries {
        scope: scope.clone(),
        mode: Mode::Estimate,
        unit: Some(unit.to_string()),
        points: Vec::new(),
        diagnostics,
        formula_version: ESTIMATE_FORMULA_VERSION.to_string(),
    }
}

/// The finding for a unit the board does not declare: no point is folded at all.
fn undeclared_unit(scope: &AnalyticsScope, unit: &str, config: &Config) -> AnalyticsDiagnostic {
    let declared = declared_units(config);
    let table = if declared.is_empty() {
        "the board declares no estimate unit".to_string()
    } else {
        format!(
            "the board declares {}",
            declared
                .iter()
                .map(|unit| format!("`{unit}`"))
                .collect::<Vec<_>>()
                .join(", ")
        )
    };
    AnalyticsDiagnostic::new(
        AnalyticsDiagnosticKind::MissingConversion,
        scope.id.clone(),
        format!(
            "estimate mode cannot count in `{unit}`: {table}, so no day is folded and no \
             estimate total is fabricated"
        ),
    )
    .with_remedy(
        "choose `--mode count`, or declare the unit under `[kanban.<board>.wip.units]` and \
         state the estimates in it",
    )
}

/// One finding per unbroken run of days with no recorded contribution.
///
/// A run, not a day: one quiet week says "7 days" once rather than seven times. The
/// sentence is the one [`crate::analytics::series`] uses for the count fold's own
/// gaps — the fact is the same in both modes, and a reader comparing two series for
/// one scope should not have to learn a second phrasing for one gap.
fn gap_findings(
    scope: &AnalyticsScope,
    points: &[DailyPoint],
    observed: &BTreeSet<String>,
) -> Vec<AnalyticsDiagnostic> {
    let mut findings = Vec::new();
    let mut run: Option<(String, String, usize)> = None;
    for point in points {
        if observed.contains(&point.date) {
            if let Some((first, last, days)) = run.take() {
                findings.push(gap_finding(scope, &first, &last, days));
            }
        } else {
            run = match run {
                Some((first, _, days)) => Some((first, point.date.clone(), days + 1)),
                None => Some((point.date.clone(), point.date.clone(), 1)),
            };
        }
    }
    if let Some((first, last, days)) = run {
        findings.push(gap_finding(scope, &first, &last, days));
    }
    findings
}

/// One gap's finding.
fn gap_finding(
    scope: &AnalyticsScope,
    first: &str,
    last: &str,
    days: usize,
) -> AnalyticsDiagnostic {
    let span = if first == last {
        first.to_string()
    } else {
        format!("{first}..{last}")
    };
    AnalyticsDiagnostic::new(
        AnalyticsDiagnosticKind::MissingHistory,
        scope.id.clone(),
        format!("{days} day(s) in {span} carry no recorded history"),
    )
    .on(first)
}

/// The finding for a level the period cannot answer: recorded completions outweigh
/// recorded additions, so the remaining work has no origin inside the period.
fn level_finding(
    scope: &AnalyticsScope,
    unit: &str,
    day: &str,
    total: i64,
    done: i64,
) -> AnalyticsDiagnostic {
    AnalyticsDiagnostic::new(
        AnalyticsDiagnosticKind::MissingHistory,
        scope.id.clone(),
        format!(
            "on {day} the period records `{done}` `{unit}` of completion but only `{total}` \
             `{unit}` of scope addition, so the remaining work cannot be answered from the \
             period alone"
        ),
    )
    .on(day)
}

/// Classify a point's coverage from what it can actually say.
///
/// The rule [`crate::analytics::series`] applies to a count point, kept identical
/// here so a reader gets the same three states from either mode: every value known
/// is known (unless the day is weak), no value known is unknown, and anything in
/// between is coverage-limited.
fn coverage_of(point: &DailyPoint, weak: bool) -> Coverage {
    let values = [
        point.scope_total,
        point.remaining,
        point.completed,
        point.scope_added,
        point.completions,
    ];
    let known = values.iter().filter(|value| value.is_some()).count();
    match known {
        0 => Coverage::Unknown,
        5 if !weak => Coverage::Known,
        _ => Coverage::CoverageLimited,
    }
}

/// The scope's members, each with the size its stated estimate resolves to.
fn size_members(
    snapshot: &ScopeSnapshot,
    issues: &[Issue],
    conversion: &EstimateConversion,
) -> BTreeMap<u32, MemberSize> {
    let records: BTreeMap<u32, &Issue> = issues.iter().map(|issue| (issue.number, issue)).collect();
    snapshot
        .members()
        .iter()
        .map(|&number| match records.get(&number) {
            Some(issue) => (
                number,
                conversion.size_of(number, issue.estimate.as_deref()),
            ),
            // The snapshot's members came from the same slice, so this is a caller
            // that passed a narrower slice; the contribution is reported, not sized.
            None => (number, MemberSize::Unrecorded),
        })
        .collect()
}

/// The valued contributions of one scope (T014), and everything the fold could not
/// value.
#[derive(Debug, Default)]
struct ValuedDays {
    /// The `scope_added` values carried per day, in the selected unit.
    added: BTreeMap<String, i64>,
    /// The `completions` values carried per day, in the selected unit.
    completed: BTreeMap<String, i64>,
    /// Every contribution's stable id per day, in first-seen order.
    event_ids: BTreeMap<String, Vec<String>>,
    /// The days whose change set the fold could not fully value.
    weak: BTreeSet<String>,
    /// Refused values, by (field, shared reason).
    refusals: BTreeMap<(Field, RefusalKey), Tally>,
    /// Contributions of an unestimated member, by field.
    unestimated: BTreeMap<Field, Tally>,
    /// Contributions no loaded issue can be sized from, by field.
    unattributed: BTreeMap<Field, Tally>,
    /// Contributions the record carries no count-level value for, by field.
    unquantified: BTreeMap<Field, Tally>,
    /// Recorded estimate changes inside the period.
    rescoped: Tally,
    /// Every other recorded event.
    unclassified: Tally,
}

impl ValuedDays {
    /// The findings this fold's own valuation produced, in a stable order.
    fn findings(&self, scope: &AnalyticsScope, unit: &str) -> Vec<AnalyticsDiagnostic> {
        let mut diagnostics = Vec::new();

        for ((field, key), tally) in &self.refusals {
            let reason = tally
                .reason
                .as_deref()
                .unwrap_or("the shared conversion refused it");
            let mut diagnostic = AnalyticsDiagnostic::new(
                AnalyticsDiagnosticKind::MissingConversion,
                scope.id.clone(),
                format!(
                    "{} recorded `{}` contribution(s) are left out of the estimate series in \
                     `{unit}`: {reason}",
                    tally.count,
                    field.as_str()
                ),
            );
            if let Some(event) = tally.first_event.as_deref() {
                diagnostic = diagnostic.about_event(event);
            }
            // The registry's own "what to do about it" when it gave one, and a
            // shape-naming remedy otherwise: a conversion the board cannot make is
            // fixed where the unit or the estimate is declared, not here.
            diagnostic = match tally.remedy.as_deref() {
                Some(remedy) => diagnostic.with_remedy(remedy),
                None if key.kind == "malformed_estimate" => diagnostic.with_remedy(
                    "rewrite the issue's `estimate:` as `<number><unit>`, or run `tix lint`",
                ),
                None => diagnostic,
            };
            diagnostics.push(diagnostic);
        }

        for (field, tally) in &self.unestimated {
            diagnostics.push(sized_finding(
                scope,
                tally,
                format!(
                    "{} recorded `{}` contribution(s) belong to an unestimated issue, so \
                         their size in `{unit}` is unknown and their days are coverage-limited",
                    tally.count,
                    field.as_str()
                ),
                "state the estimate on the issue (`tix edit <n> --estimate <number><unit>`) \
                     so its work can be sized",
            ));
        }

        for (field, tally) in &self.unattributed {
            diagnostics.push(sized_finding(
                scope,
                tally,
                format!(
                    "{} recorded `{}` contribution(s) name no issue this series can size (a \
                     closed snapshot's contribution carries no issue), so they are not valued in \
                     `{unit}`",
                    tally.count,
                    field.as_str()
                ),
                "read the day as coverage-limited: only the recorded per-issue contributions can \
                 be sized",
            ));
        }

        for (field, tally) in &self.unquantified {
            diagnostics.push(sized_finding(
                scope,
                tally,
                format!(
                    "{} recorded `{}` contribution(s) carry no count-level value, so their size in \
                     `{unit}` is unknown and their days are coverage-limited",
                    tally.count,
                    field.as_str()
                ),
                "read the day as coverage-limited: the recorded detail names the change but not \
                 its size in this unit",
            ));
        }

        if self.rescoped.count > 0 {
            let tally = &self.rescoped;
            let mut diagnostic = AnalyticsDiagnostic::new(
                AnalyticsDiagnosticKind::MissingHistory,
                scope.id.clone(),
                format!(
                    "{} recorded estimate change(s) inside the period re-sized an issue; the series \
                     values every contribution at the estimate the issue states now, so a level \
                     before such a change is not the level the record held then",
                    tally.count
                ),
            );
            if let Some(event) = tally.first_event.as_deref() {
                diagnostic = diagnostic.about_event(event);
            }
            diagnostics.push(diagnostic);
        }

        if self.unclassified.count > 0 {
            let tally = &self.unclassified;
            let mut diagnostic = AnalyticsDiagnostic::new(
                AnalyticsDiagnosticKind::UnclassifiedEvent,
                scope.id.clone(),
                format!(
                    "{} recorded event(s) in the period carry no scope, completion or estimate \
                     meaning and move no line",
                    tally.count
                ),
            );
            if let Some(event) = tally.first_event.as_deref() {
                diagnostic = diagnostic.about_event(event);
            }
            diagnostics.push(diagnostic);
        }

        diagnostics
    }
}

/// One contribution-group finding, with the first contributing event as provenance.
///
/// The message already names the field the value would have landed in, so the group
/// is reported once per (reason, field) with a count rather than once per issue.
fn sized_finding(
    scope: &AnalyticsScope,
    tally: &Tally,
    message: String,
    remedy: &str,
) -> AnalyticsDiagnostic {
    let mut diagnostic = AnalyticsDiagnostic::new(
        AnalyticsDiagnosticKind::MissingHistory,
        scope.id.clone(),
        message,
    )
    .with_remedy(remedy);
    if let Some(event) = tally.first_event.as_deref() {
        diagnostic = diagnostic.about_event(event);
    }
    diagnostic
}

/// Value every recorded contribution of the scope on its day.
fn value_days(snapshot: &ScopeSnapshot, sizes: &BTreeMap<u32, MemberSize>) -> ValuedDays {
    let mut valued = ValuedDays::default();
    for event in snapshot.event_index().events() {
        // A contribution with no readable day is a service-level finding (the
        // snapshot reports it) and weakens every day through `unplaced_events`.
        let Some(date) = event.date.as_deref() else {
            continue;
        };
        valued
            .event_ids
            .entry(date.to_string())
            .or_default()
            .push(event.event_id.clone());
        match event.class {
            EventClass::ScopeAddition | EventClass::Completion => {
                let field = match event.class {
                    EventClass::ScopeAddition => Field::Added,
                    _ => Field::Completed,
                };
                if event.delta.is_none() {
                    valued.weak.insert(date.to_string());
                    valued.unquantified.entry(field).or_default().record(event);
                    continue;
                }
                match event.issue.and_then(|number| sizes.get(&number)) {
                    Some(MemberSize::Sized(size)) => {
                        let bucket = match field {
                            Field::Added => &mut valued.added,
                            Field::Completed => &mut valued.completed,
                        };
                        *bucket.entry(date.to_string()).or_default() += size;
                    }
                    Some(MemberSize::Unestimated) => {
                        valued.weak.insert(date.to_string());
                        valued.unestimated.entry(field).or_default().record(event);
                    }
                    Some(MemberSize::Refused(refusal)) => {
                        valued.weak.insert(date.to_string());
                        valued
                            .refusals
                            .entry((field, refusal.key.clone()))
                            .or_default()
                            .record_refusal(event, refusal);
                    }
                    Some(MemberSize::Unrecorded) | None => {
                        valued.weak.insert(date.to_string());
                        valued.unattributed.entry(field).or_default().record(event);
                    }
                }
            }
            // A re-sizing recorded inside the period: reported, and the day limited.
            // It is never replayed into the levels (see the module documentation).
            EventClass::EstimateChange => {
                valued.weak.insert(date.to_string());
                valued.rescoped.record(event);
            }
            EventClass::Unclassified => valued.unclassified.record(event),
        }
    }
    valued
}

/// How one member's stated estimate reads in the series' unit (T013).
#[derive(Debug, Clone)]
enum MemberSize {
    /// Converted: the size every counted contribution of this member carries.
    Sized(i64),
    /// The member states no estimate at all.
    Unestimated,
    /// Stated but not countable in this unit, with the registry's own finding.
    Refused(Refused),
    /// The member's record was not among the issues this series was given.
    Unrecorded,
}

/// Why a stated estimate could not be counted, in the shared vocabulary.
#[derive(Debug, Clone)]
struct Refused {
    /// What refused it: the registry's kind and the unit spelling the issue used.
    key: RefusalKey,
    /// The registry's sentence, verbatim (it already names the issue).
    reason: String,
    /// The registry's own remedy, when it gave one.
    remedy: Option<String>,
}

/// The grouping key of a refusal: the shared reason and the spelling behind it.
///
/// Two issues that wrote the same undeclared unit, or that both failed the same
/// arithmetic, group into one finding — the count is the actionable part, and one
/// finding per issue would bury it.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct RefusalKey {
    /// The registry's machine-readable kind (`missing_conversion`, `unknown_unit`,
    /// `ambiguous_conversion`, `malformed_estimate`).
    kind: &'static str,
    /// The unit the issue named, when it named one.
    spelled: Option<String>,
}

/// The `DailyPoint` field a contribution's value lands in.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum Field {
    /// `scope_added` (and, carried, `scope_total`).
    Added,
    /// `completions` (and, carried, `completed`).
    Completed,
}

impl Field {
    /// The stable field name the finding quotes.
    const fn as_str(self) -> &'static str {
        match self {
            Field::Added => "scope_added",
            Field::Completed => "completions",
        }
    }
}

/// One group of contributions the fold could not value: how many, and the first.
#[derive(Debug, Clone, Default)]
struct Tally {
    /// How many contributions the group holds.
    count: usize,
    /// The stable id of the first contribution in the group.
    first_event: Option<String>,
    /// The registry's sentence for the first contribution, when it gave one.
    reason: Option<String>,
    /// The registry's own remedy for the first contribution, when it gave one.
    remedy: Option<String>,
}

impl Tally {
    /// Count one contribution, keeping the first as the group's provenance.
    fn record(&mut self, event: &AnalyticsEvent) {
        self.count += 1;
        if self.first_event.is_none() {
            self.first_event = Some(event.event_id.clone());
        }
    }

    /// Count one refused contribution, keeping the first refusal's own words.
    fn record_refusal(&mut self, event: &AnalyticsEvent, refusal: &Refused) {
        let first = self.count == 0;
        self.record(event);
        if first {
            self.reason = Some(refusal.reason.clone());
            self.remedy = refusal.remedy.clone();
        }
    }
}