lemma-engine 0.10.2

use crate::computation::{OperationResult, VetoType};
use crate::evaluation::explanations::Explanation;

use crate::parsing::ast::DateTimeValue;
use crate::planning::execution_plan::ExecutionPlan;
use crate::planning::semantics::{
    DataDefinition, DataPath, LemmaType, LiteralValue, PathSegment, RowInstance, RulePath, Source,
    SpecInstance, SpecValue, ValueKind,
};
use crate::planning::unit_family::FamilyUnitCatalog;
use crate::result_value::{
    rule_result_value_failure_message, rule_result_value_from_literal, RowReference, RowResult,
    RuleResultValue, RuleResultValueFailure, SpecResult, SpecRuleResult,
};
use indexmap::IndexMap;
use std::collections::HashMap;
use std::sync::Arc;

/// Rule info with resolved expressions for use in evaluation response.
/// Evaluation uses only semantics types; no parsing types.
#[derive(Debug, Clone)]
pub struct EvaluatedRule {
    pub name: String,
    pub path: RulePath,
    pub source_location: Source,
    pub rule_type: Arc<LemmaType>,
}

/// Response from evaluating a Lemma spec
#[derive(Debug, Clone)]
pub struct Response {
    pub spec_name: String,
    pub effective: String,
    /// Declared temporal window `[spec_effective_from, spec_effective_to)` of the
    /// resolved spec version. Set by [`crate::Engine::evaluate`] after evaluation;
    /// `None` here (evaluation-internal construction) until that assignment.
    pub spec_effective_from: Option<DateTimeValue>,
    pub spec_effective_to: Option<DateTimeValue>,
    pub results: IndexMap<String, RuleResult>,
    /// Rows reached by `results`, indexed by [`RowReference::index`].
    pub rows: Vec<RowResult>,
}

/// Result of evaluating a single rule. Struct fields match the API JSON shape.
#[derive(Debug, Clone)]
pub struct RuleResult {
    pub rule: EvaluatedRule,
    pub veto_detail: Option<VetoType>,

    pub vetoed: bool,
    pub veto_reason: Option<String>,
    pub rule_type: String,

    /// Flattened value fields, including `result` when the rule is not vetoed.
    pub result: Option<RuleResultValue>,
    pub explanation: Option<Explanation>,
    /// Unbound caller data paths still live for this rule under the current run data
    /// (`DataPath::input_key` strings; subset of `Show.data` keys with non-empty
    /// `needed_by_rules`). Ordered by evaluation / decision-tree preorder (first key =
    /// next fact the live tree needs); `Show.data` stays declaration order.
    missing_data: Vec<String>,
}

impl RuleResult {
    /// Engine-rendered one-liner from the flattened [`RuleResultValue`].
    #[must_use]
    pub fn result(&self) -> Option<&str> {
        self.result
            .as_ref()
            .and_then(|value| value.result.as_deref())
    }

    /// True when this result is a [`VetoType::MissingData`] or [`VetoType::MissingRowData`] veto.
    ///
    /// Value and other vetoes are settled answers; leftover live keys in
    /// [`Self::missing_data`] must not drive prompts or human "Missing data" display.
    #[must_use]
    pub fn is_missing_data(&self) -> bool {
        matches!(
            self.veto_detail.as_ref(),
            Some(VetoType::MissingData { .. } | VetoType::MissingRowData { .. })
        )
    }

    /// Unbound caller data paths still live for this rule (`DataPath::input_key`),
    /// in evaluation / decision-tree order (contrast `Show.data` declaration order).
    #[must_use]
    pub fn missing_data(&self) -> &[String] {
        &self.missing_data
    }

    /// Build a [`RuleResult`] for API output from a rule evaluation result.
    ///
    /// Measure and ratio payloads expand into every unit in the result type's family.
    pub(crate) fn from_operation_result(
        rule: EvaluatedRule,
        operation_result: &OperationResult,
        rule_type: &LemmaType,
        family_units: &FamilyUnitCatalog,
        explanation: Option<Explanation>,
        missing_data: Vec<String>,
    ) -> Self {
        match operation_result {
            OperationResult::Veto(VetoType::MissingData { data, .. }) => {
                let key = data.input_key();
                if !missing_data.iter().any(|listed| listed == &key) {
                    panic!("BUG: MissingData path {key} not in missing_data {missing_data:?}");
                }
            }
            OperationResult::Veto(VetoType::MissingRowData { key }) => {
                if !missing_data.contains(key) {
                    panic!("BUG: missing row field {key} not in missing_data {missing_data:?}");
                }
            }
            _ => {
                if !missing_data.is_empty() {
                    panic!(
                        "BUG: missing_data must be empty when result is not MissingData: {missing_data:?}"
                    );
                }
            }
        }
        let rule_type_name = rule_type.name().to_string();
        match operation_result {
            OperationResult::Veto(veto) => Self::vetoed_with(
                rule,
                veto.clone(),
                rule_type_name,
                explanation,
                missing_data,
            ),
            OperationResult::Value(bound) => {
                match rule_result_value_from_literal(&bound.to_literal(), rule_type, family_units) {
                    Ok(value) => Self {
                        rule,
                        veto_detail: None,
                        vetoed: false,
                        veto_reason: None,
                        rule_type: rule_type_name,
                        result: Some(value),
                        explanation,
                        missing_data,
                    },
                    Err(failure) => vetoed_rule_result_for_rule_result_value_failure(
                        rule,
                        rule_type,
                        explanation,
                        failure,
                        missing_data,
                    ),
                }
            }
        }
    }

    fn vetoed_with(
        rule: EvaluatedRule,
        veto: VetoType,
        rule_type: String,
        explanation: Option<Explanation>,
        missing_data: Vec<String>,
    ) -> Self {
        Self {
            rule,
            veto_reason: match &veto {
                VetoType::UserDefined { message: None } => None,
                _ => Some(veto.to_string()),
            },
            veto_detail: Some(veto),
            vetoed: true,
            rule_type,
            result: None,
            explanation,
            missing_data,
        }
    }

    /// Reconstruct the evaluated [`LiteralValue`] from committed [`RuleResultValue`] fields.
    ///
    /// Panics if the rule is vetoed or fields cannot be reconstructed.
    pub fn to_literal(&self) -> LiteralValue {
        assert!(
            !self.vetoed,
            "BUG: to_literal called on vetoed rule '{}'",
            self.rule.name
        );
        let value = self
            .result
            .as_ref()
            .unwrap_or_else(|| panic!("BUG: non-vetoed rule '{}' missing result", self.rule.name));
        value.to_literal(&self.rule.rule_type)
    }
}

fn vetoed_rule_result_for_rule_result_value_failure(
    rule: EvaluatedRule,
    rule_type: &LemmaType,
    explanation: Option<Explanation>,
    failure: RuleResultValueFailure,
    missing_data: Vec<String>,
) -> RuleResult {
    RuleResult::vetoed_with(
        rule,
        VetoType::computation(rule_result_value_failure_message(failure).to_string()),
        rule_type.name().to_string(),
        explanation,
        missing_data,
    )
}

impl Response {
    /// Looks up a rule result by name.
    ///
    /// Returns an error if the rule is not found.
    pub fn get(&self, rule_name: &str) -> Result<&RuleResult, crate::error::Error> {
        self.results
            .get(rule_name)
            .ok_or_else(|| crate::error::Error::rule_not_found(rule_name, None::<String>))
    }

    pub fn add_result(&mut self, result: RuleResult) {
        self.results.insert(result.rule.name.clone(), result);
    }
}

/// Distinct rows reached by one response, in first-reached order. Each row is filled
/// once and referenced by index everywhere else, so output grows with the number of
/// rows, not with the number of paths that reach them.
#[derive(Default)]
pub(crate) struct RowTable {
    index: HashMap<Arc<RowInstance>, usize>,
    rows: Vec<Option<RowResult>>,
}

impl RowTable {
    pub(crate) fn into_rows(self) -> Vec<RowResult> {
        self.rows
            .into_iter()
            .enumerate()
            .map(|(index, row)| row.unwrap_or_else(|| panic!("BUG: row {index} never filled")))
            .collect()
    }
}

/// Fill every spec value inside `literal`'s API `value`: a fixed instance gets its data
/// and rules inline, a list row a reference into `table`.
pub(crate) fn fill_spec_values(
    literal: &ValueKind,
    value: &mut RuleResultValue,
    plan: &ExecutionPlan,
    ctx: &mut crate::evaluation::EvaluationContext,
    table: &mut RowTable,
    stack: &mut Vec<SpecInstance>,
) {
    if matches!(
        literal,
        ValueKind::Number(_)
            | ValueKind::Measure(_)
            | ValueKind::Ratio(_)
            | ValueKind::Text(_)
            | ValueKind::Date(_)
            | ValueKind::Time(_)
            | ValueKind::Boolean(_)
            | ValueKind::Range(_, _)
    ) {
        return;
    }
    let mut walk = Walk {
        base: ctx,
        table,
        row_contexts: Vec::new(),
        ancestors: std::mem::take(stack),
    };
    let root = Frame::fill(plan, literal.clone(), std::mem::take(value));
    *value = walk.run(root).into_value();
    *stack = walk.ancestors;
}

/// Shared state of one fill walk. `base` is the caller's context; a row being walked
/// runs in its own context on `row_contexts`, innermost last.
struct Walk<'b> {
    base: &'b mut crate::evaluation::EvaluationContext,
    table: &'b mut RowTable,
    row_contexts: Vec<crate::evaluation::EvaluationContext>,
    ancestors: Vec<SpecInstance>,
}

impl Walk<'_> {
    fn ctx(&mut self) -> &mut crate::evaluation::EvaluationContext {
        match self.row_contexts.last_mut() {
            Some(row_ctx) => row_ctx,
            None => &mut *self.base,
        }
    }

    fn run<'a>(&mut self, root: Frame<'a>) -> Output {
        let mut frames = vec![root];
        let mut input = None;
        loop {
            let frame = frames.last_mut().expect("BUG: fill walk frame stack empty");
            match frame.resume(self, input.take()) {
                Step::Call(child) => frames.push(child),
                Step::Return(output) => {
                    frames.pop();
                    if frames.is_empty() {
                        return output;
                    }
                    input = Some(output);
                }
            }
        }
    }
}

enum Frame<'a> {
    Fill(Box<FillFrame<'a>>),
    Spec(SpecFrame<'a>),
    Row(RowFrame<'a>),
    Members(Box<MembersFrame<'a>>),
}

impl<'a> Frame<'a> {
    fn fill(plan: &'a ExecutionPlan, literal: ValueKind, value: RuleResultValue) -> Self {
        Frame::Fill(Box::new(FillFrame::new(plan, literal, value)))
    }

    fn members(
        plan: &'a ExecutionPlan,
        prefix: Vec<PathSegment>,
        row: Option<Arc<RowInstance>>,
    ) -> Self {
        Frame::Members(Box::new(MembersFrame::new(plan, prefix, row)))
    }

    fn resume(&mut self, walk: &mut Walk<'_>, input: Option<Output>) -> Step<'a> {
        match self {
            Frame::Fill(frame) => frame.resume(input),
            Frame::Spec(frame) => frame.resume(walk, input),
            Frame::Row(frame) => frame.resume(walk, input),
            Frame::Members(frame) => frame.resume(walk, input),
        }
    }
}

enum Step<'a> {
    Call(Frame<'a>),
    Return(Output),
}

enum Output {
    Value(Box<RuleResultValue>),
    Spec(SpecResult),
    Row(RowReference),
    Members(FilledMembers),
}

impl Output {
    fn into_value(self) -> RuleResultValue {
        match self {
            Output::Value(value) => *value,
            _ => panic!("BUG: fill walk expected a value output"),
        }
    }

    fn into_spec(self) -> SpecResult {
        match self {
            Output::Spec(spec) => spec,
            _ => panic!("BUG: fill walk expected a spec output"),
        }
    }

    fn into_row(self) -> RowReference {
        match self {
            Output::Row(row) => row,
            _ => panic!("BUG: fill walk expected a row output"),
        }
    }

    fn into_members(self) -> FilledMembers {
        match self {
            Output::Members(members) => members,
            _ => panic!("BUG: fill walk expected a members output"),
        }
    }
}

fn child_output(input: Option<Output>) -> Output {
    input.expect("BUG: fill walk frame resumed without child output")
}

enum FillState {
    Start(ValueKind),
    AwaitSpec,
    AwaitRow,
    Items(
        std::vec::IntoIter<(ValueKind, RuleResultValue)>,
        Vec<RuleResultValue>,
    ),
}

/// Fills one value: a fixed instance gets its data and rules inline, a list row a
/// reference into the table, a list fills each entry in order.
struct FillFrame<'a> {
    plan: &'a ExecutionPlan,
    value: RuleResultValue,
    state: Option<FillState>,
}

impl<'a> FillFrame<'a> {
    fn new(plan: &'a ExecutionPlan, literal: ValueKind, value: RuleResultValue) -> Self {
        Self {
            plan,
            value,
            state: Some(FillState::Start(literal)),
        }
    }

    fn resume(&mut self, input: Option<Output>) -> Step<'a> {
        match self
            .state
            .take()
            .expect("BUG: fill frame resumed after completion")
        {
            FillState::Start(literal) => {
                assert!(
                    input.is_none(),
                    "BUG: fill frame started with a child output"
                );
                self.start(literal)
            }
            FillState::AwaitSpec => {
                self.value.spec = Some(Box::new(child_output(input).into_spec()));
                self.finish()
            }
            FillState::AwaitRow => {
                self.value.row = Some(child_output(input).into_row());
                self.finish()
            }
            FillState::Items(items, mut filled) => {
                filled.push(child_output(input).into_value());
                self.next_item(items, filled)
            }
        }
    }

    fn start(&mut self, literal: ValueKind) -> Step<'a> {
        let plan = self.plan;
        match literal {
            ValueKind::Spec(SpecValue::Fixed(instance)) => {
                assert!(
                    self.value.spec.is_some(),
                    "BUG: fixed spec value '{instance}' without spec arm"
                );
                self.state = Some(FillState::AwaitSpec);
                Step::Call(Frame::Spec(SpecFrame::new(plan, instance)))
            }
            ValueKind::Spec(SpecValue::Row(row)) => {
                assert!(
                    self.value.row.is_none(),
                    "BUG: row '{}' filled twice",
                    row.origin
                );
                self.state = Some(FillState::AwaitRow);
                Step::Call(Frame::Row(RowFrame::new(plan, row)))
            }
            ValueKind::List(rows) => {
                let entries = self
                    .value
                    .list
                    .take()
                    .expect("BUG: list value without list arm");
                assert_eq!(
                    entries.len(),
                    rows.len(),
                    "BUG: list arm row count differs from the list value"
                );
                let filled = Vec::with_capacity(entries.len());
                let items: Vec<(ValueKind, RuleResultValue)> =
                    rows.into_iter().map(|row| row.value).zip(entries).collect();
                self.next_item(items.into_iter(), filled)
            }
            ValueKind::Number(_)
            | ValueKind::Measure(_)
            | ValueKind::Ratio(_)
            | ValueKind::Text(_)
            | ValueKind::Date(_)
            | ValueKind::Time(_)
            | ValueKind::Boolean(_)
            | ValueKind::Range(_, _) => self.finish(),
        }
    }

    fn next_item(
        &mut self,
        mut items: std::vec::IntoIter<(ValueKind, RuleResultValue)>,
        filled: Vec<RuleResultValue>,
    ) -> Step<'a> {
        match items.next() {
            Some((literal, entry)) => {
                self.state = Some(FillState::Items(items, filled));
                Step::Call(Frame::fill(self.plan, literal, entry))
            }
            None => {
                self.value.list = Some(filled);
                self.finish()
            }
        }
    }

    fn finish(&mut self) -> Step<'a> {
        Step::Return(Output::Value(Box::new(std::mem::take(&mut self.value))))
    }
}

/// Data and rules of one spec instance: its ancestors entry is held for the walk of its
/// members.
struct SpecFrame<'a> {
    plan: &'a ExecutionPlan,
    instance: SpecInstance,
    identity: Option<(Option<String>, String, String)>,
}

impl<'a> SpecFrame<'a> {
    fn new(plan: &'a ExecutionPlan, instance: SpecInstance) -> Self {
        Self {
            plan,
            instance,
            identity: None,
        }
    }

    fn resume(&mut self, walk: &mut Walk<'_>, input: Option<Output>) -> Step<'a> {
        let plan = self.plan;
        match input {
            None => {
                if walk.ancestors.iter().any(|seen| seen == &self.instance) {
                    panic!("BUG: spec result walked instance '{}' twice", self.instance);
                }
                walk.ancestors.push(self.instance.clone());
                self.identity = Some(instance_identity(plan, &self.instance));
                Step::Call(Frame::members(plan, self.instance.prefix.clone(), None))
            }
            Some(output) => {
                walk.ancestors.pop();
                let (data, rules) = output.into_members();
                let (repository, spec, effective) = self
                    .identity
                    .take()
                    .expect("BUG: spec frame finished before it started");
                Step::Return(Output::Spec(SpecResult {
                    repository,
                    spec,
                    effective,
                    instance: self.instance.to_string(),
                    path: self
                        .instance
                        .prefix
                        .iter()
                        .map(crate::api::PathSegment::from)
                        .collect(),
                    data,
                    rules,
                }))
            }
        }
    }
}

/// Reference to `row` in the table, filling the row through its template plan when
/// first reached. The row's members walk in their own context and ancestor scope.
struct RowFrame<'a> {
    plan: &'a ExecutionPlan,
    row: Arc<RowInstance>,
    index: usize,
    saved_ancestors: Vec<SpecInstance>,
}

impl<'a> RowFrame<'a> {
    fn new(plan: &'a ExecutionPlan, row: Arc<RowInstance>) -> Self {
        Self {
            plan,
            row,
            index: 0,
            saved_ancestors: Vec::new(),
        }
    }

    fn resume(&mut self, walk: &mut Walk<'_>, input: Option<Output>) -> Step<'a> {
        match input {
            None => {
                if let Some(index) = walk.table.index.get(&self.row).copied() {
                    return Step::Return(Output::Row(row_reference(&self.row, index)));
                }
                let index = walk.table.rows.len();
                walk.table.index.insert(Arc::clone(&self.row), index);
                walk.table.rows.push(None);
                self.index = index;
                let plan = self.plan;
                let template = plan.row_template(&self.row.identity);
                let row_ctx =
                    crate::evaluation::rows::take_row_context(&self.row, template, walk.ctx());
                walk.row_contexts.push(row_ctx);
                self.saved_ancestors = std::mem::take(&mut walk.ancestors);
                Step::Call(Frame::members(
                    template,
                    Vec::new(),
                    Some(Arc::clone(&self.row)),
                ))
            }
            Some(output) => {
                let (data, rules) = output.into_members();
                walk.ancestors = std::mem::take(&mut self.saved_ancestors);
                let row_ctx = walk
                    .row_contexts
                    .pop()
                    .expect("BUG: row context stack empty when its row ends");
                walk.ctx()
                    .row_contexts
                    .insert(Arc::clone(&self.row), row_ctx);
                walk.table.rows[self.index] = Some(RowResult {
                    repository: self.row.identity.repository.clone(),
                    spec: self.row.identity.spec.clone(),
                    effective: self.row.identity.effective.to_string(),
                    data,
                    rules,
                });
                Step::Return(Output::Row(row_reference(&self.row, self.index)))
            }
        }
    }
}

fn row_reference(row: &RowInstance, index: usize) -> RowReference {
    RowReference {
        repository: row.identity.repository.clone(),
        spec: row.identity.spec.clone(),
        effective: row.identity.effective.to_string(),
        instance: row.origin.to_string(),
        index,
    }
}

/// An entry whose value is being filled, with the key it is inserted under once filled.
enum Awaiting {
    Data(String, SpecRuleResult),
    Rule(RulePath, SpecRuleResult),
}

/// Data then rules of `plan` under `prefix`, keyed relative to it. For a row, `plan` is
/// its template and missing data is reported under the row's number.
struct MembersFrame<'a> {
    plan: &'a ExecutionPlan,
    prefix: Vec<PathSegment>,
    row: Option<Arc<RowInstance>>,
    data_keys: std::vec::IntoIter<(DataPath, &'a DataDefinition)>,
    rule_paths: std::vec::IntoIter<RulePath>,
    data: IndexMap<String, SpecRuleResult>,
    rules: IndexMap<String, SpecRuleResult>,
    awaiting: Option<Awaiting>,
}

impl<'a> MembersFrame<'a> {
    fn new(
        plan: &'a ExecutionPlan,
        prefix: Vec<PathSegment>,
        row: Option<Arc<RowInstance>>,
    ) -> Self {
        let rule_paths: Vec<RulePath> = plan
            .rules
            .keys()
            .filter(|path| path_under_prefix(&path.segments, &prefix))
            .cloned()
            .collect();
        Self {
            plan,
            // Named-`uses` fields live on templates; enumerate via nested_input_keys.
            data_keys: plan.nested_input_keys().into_iter(),
            rule_paths: rule_paths.into_iter(),
            prefix,
            row,
            data: IndexMap::new(),
            rules: IndexMap::new(),
            awaiting: None,
        }
    }

    fn resume(&mut self, walk: &mut Walk<'_>, input: Option<Output>) -> Step<'a> {
        match (self.awaiting.take(), input) {
            (None, None) => {}
            (Some(Awaiting::Data(key, mut entry)), Some(output)) => {
                entry.result = Some(output.into_value());
                self.data.insert(key, entry);
            }
            (Some(Awaiting::Rule(path, mut entry)), Some(output)) => {
                entry.result = Some(output.into_value());
                self.rules
                    .insert(relative_rule_key(&path, &self.prefix), entry);
            }
            _ => panic!("BUG: members frame resumed with an unexpected child output"),
        }
        while let Some((path, definition)) = self.data_keys.next() {
            if let Some(step) = self.data_item(walk, path, definition) {
                return step;
            }
        }
        while let Some(path) = self.rule_paths.next() {
            if let Some(step) = self.rule_item(walk, path) {
                return step;
            }
        }
        Step::Return(Output::Members((
            std::mem::take(&mut self.data),
            std::mem::take(&mut self.rules),
        )))
    }

    fn data_item(
        &mut self,
        walk: &mut Walk<'_>,
        path: DataPath,
        definition: &'a DataDefinition,
    ) -> Option<Step<'a>> {
        let plan = self.plan;
        if path.segments.len() != self.prefix.len()
            || !path_under_prefix(&path.segments, &self.prefix)
        {
            return None;
        }
        definition.schema_type()?;
        let relative = relative_data_key(&path, &self.prefix);
        let slot = match walk.ctx().data_slot(plan, &path).cloned() {
            Some(slot) => slot,
            None if !path.segments.is_empty() => {
                crate::evaluation::imports::eval_import_member(&path, plan, walk.ctx())
            }
            None => return None,
        };
        if matches!(slot, OperationResult::Veto(VetoType::MissingData { .. })) {
            return None;
        }
        let display_type =
            crate::evaluation::EvaluationContext::data_display_type(plan, &path, &slot);
        let mut entry = spec_entry(
            &slot,
            path.input_key(),
            RulePath {
                segments: path.segments.clone(),
                rule: path.data.clone(),
            },
            definition.source().clone(),
            display_type.as_ref(),
            &plan.family_units,
            Vec::new(),
        );
        let OperationResult::Value(bound) = slot else {
            self.data.insert(relative, entry);
            return None;
        };
        let Some(value) = entry.result.take() else {
            self.data.insert(relative, entry);
            return None;
        };
        self.awaiting = Some(Awaiting::Data(relative, entry));
        Some(Step::Call(Frame::fill(plan, bound.value, value)))
    }

    fn rule_item(&mut self, walk: &mut Walk<'_>, path: RulePath) -> Option<Step<'a>> {
        let plan = self.plan;
        let row = self.row.as_deref();
        let exec = plan
            .rules
            .get(&path)
            .expect("BUG: rule path missing from plan");
        crate::evaluation::tree::ensure_rule_values(plan.rule_index(&path), plan, walk.ctx());
        let local = walk.ctx().rule_value(plan, &path).clone();
        let missing_data = if local.is_missing_data() {
            let keys = walk.ctx().missing_data_for_rule(plan, exec.normal_form);
            match row {
                Some(row) => keys
                    .iter()
                    .map(|key| crate::evaluation::rows::row_key(row, key))
                    .collect(),
                None => keys,
            }
        } else {
            Vec::new()
        };
        let operation = match row {
            Some(row) => crate::evaluation::rows::row_result(local, row, plan),
            None => local,
        };
        let mut entry = spec_entry(
            &operation,
            path.input_key(),
            path.clone(),
            exec.source.clone(),
            exec.rule_type.as_ref(),
            &plan.family_units,
            missing_data,
        );
        match operation {
            OperationResult::Value(bound) => match entry.result.take() {
                Some(value) => {
                    self.awaiting = Some(Awaiting::Rule(path, entry));
                    Some(Step::Call(Frame::fill(plan, bound.value, value)))
                }
                None => {
                    self.rules
                        .insert(relative_rule_key(&path, &self.prefix), entry);
                    None
                }
            },
            OperationResult::Veto(_) => {
                self.rules
                    .insert(relative_rule_key(&path, &self.prefix), entry);
                None
            }
        }
    }
}

type FilledMembers = (
    IndexMap<String, SpecRuleResult>,
    IndexMap<String, SpecRuleResult>,
);

fn instance_identity(
    plan: &ExecutionPlan,
    instance: &SpecInstance,
) -> (Option<String>, String, String) {
    let last = instance
        .prefix
        .last()
        .unwrap_or_else(|| panic!("BUG: spec instance '{instance}' has no uses hop"));
    let import_path = DataPath {
        segments: instance.prefix[..instance.prefix.len() - 1].to_vec(),
        data: last.uses.clone(),
    };
    let Some(crate::planning::semantics::DataDefinition::Import { identity, .. }) =
        crate::planning::normalize::lookup_data_definition(
            &plan.data,
            &plan.row_templates,
            &import_path,
        )
    else {
        panic!(
            "BUG: spec instance '{instance}' is not an import at '{}'",
            import_path.input_key()
        );
    };
    (
        identity.repository.clone(),
        identity.spec.clone(),
        identity.effective.to_string(),
    )
}

fn spec_entry(
    operation: &OperationResult,
    name: String,
    path: RulePath,
    source: Source,
    display_type: &LemmaType,
    family_units: &FamilyUnitCatalog,
    missing_data: Vec<String>,
) -> SpecRuleResult {
    let built = RuleResult::from_operation_result(
        EvaluatedRule {
            name,
            path,
            source_location: source,
            rule_type: Arc::new(display_type.clone()),
        },
        operation,
        display_type,
        family_units,
        None,
        missing_data,
    );
    SpecRuleResult {
        vetoed: built.vetoed,
        veto_reason: built.veto_reason.clone(),
        rule_type: built.rule_type.clone(),
        result: built.result.clone(),
    }
}

fn path_under_prefix(segments: &[PathSegment], prefix: &[PathSegment]) -> bool {
    segments.len() >= prefix.len() && segments[..prefix.len()] == prefix[..]
}

fn relative_data_key(path: &DataPath, prefix: &[PathSegment]) -> String {
    assert!(
        path_under_prefix(&path.segments, prefix),
        "BUG: data '{}' is under its instance but path_under_prefix is false",
        path.input_key()
    );
    let mut key = String::new();
    for segment in &path.segments[prefix.len()..] {
        key.push_str(&segment.uses);
        key.push('.');
    }
    key.push_str(&path.data);
    key
}

fn relative_rule_key(path: &RulePath, prefix: &[PathSegment]) -> String {
    assert!(
        path_under_prefix(&path.segments, prefix),
        "BUG: rule '{}' is under its instance but path_under_prefix is false",
        path.input_key()
    );
    let mut key = String::new();
    for segment in &path.segments[prefix.len()..] {
        key.push_str(&segment.uses);
        key.push('.');
    }
    key.push_str(&path.rule);
    key
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::literals::DateGranularity;
    use crate::parsing::ast::Span;
    use crate::planning::semantics::{
        primitive_number_arc, BaseMeasureVector, DataPath, LemmaType, LiteralValue, MeasureUnit,
        MeasureUnits, RatioUnit, RatioUnits, RulePath, TypeExtends, TypeSpecification, ValueKind,
    };
    use crate::planning::unit_family::FamilyUnitCatalog;
    use crate::planning::unit_index::{UnitIndex, UnitOwner};
    use rust_decimal::Decimal;
    use std::str::FromStr;
    use std::sync::Arc;

    fn dec(s: &str) -> Decimal {
        Decimal::from_str(s).expect("BUG: test decimal literal")
    }

    fn empty_family_catalog() -> FamilyUnitCatalog {
        FamilyUnitCatalog::default()
    }

    fn family_catalog_for_index(index: &UnitIndex) -> FamilyUnitCatalog {
        FamilyUnitCatalog::build(index)
    }

    fn family_catalog_for_money(money: &LemmaType) -> FamilyUnitCatalog {
        family_catalog_for_index(&unit_index_for_money(money))
    }

    fn family_catalog_for_ratio(ratio_type: &LemmaType) -> FamilyUnitCatalog {
        family_catalog_for_index(&unit_index_for_ratio(ratio_type))
    }

    fn unit_index_for_money(money: &LemmaType) -> UnitIndex {
        let mut index = UnitIndex::new();
        let arc = Arc::new(money.clone());
        for unit_name in money.measure_unit_names().into_iter().flatten() {
            index.insert_owner(
                unit_name.to_string(),
                UnitOwner::Named {
                    import_path: Vec::new(),
                    type_name: "money".into(),
                    lemma_type: Arc::clone(&arc),
                },
            );
        }
        index
    }

    fn unit_index_for_ratio(ratio_type: &LemmaType) -> UnitIndex {
        let mut index = UnitIndex::new();
        let arc = Arc::new(ratio_type.clone());
        let type_name = ratio_type.name();
        for unit_name in ratio_type.ratio_unit_names().into_iter().flatten() {
            index.insert_owner(
                unit_name.to_string(),
                UnitOwner::Named {
                    import_path: Vec::new(),
                    type_name: type_name.clone(),
                    lemma_type: Arc::clone(&arc),
                },
            );
        }
        index
    }

    fn dummy_source() -> Source {
        Source::new(
            crate::parsing::source::SourceType::Volatile,
            Span {
                start: 0,
                end: 0,
                line: 1,
                col: 1,
            },
        )
    }

    fn dummy_evaluated_rule(name: &str, rule_type: &LemmaType) -> EvaluatedRule {
        EvaluatedRule {
            name: name.to_string(),
            path: RulePath::new(vec![], name.to_string()),
            source_location: dummy_source(),
            rule_type: Arc::new(rule_type.clone()),
        }
    }

    #[test]
    fn test_response_serialization() {
        let mut results = IndexMap::new();
        results.insert(
            "test_rule".to_string(),
            RuleResult::from_operation_result(
                dummy_evaluated_rule("test_rule", primitive_number_arc().as_ref()),
                &OperationResult::from_literal(LiteralValue::number_from_decimal(Decimal::from(
                    42,
                ))),
                primitive_number_arc().as_ref(),
                &empty_family_catalog(),
                None,
                Vec::new(),
            ),
        );
        let response = Response {
            spec_name: "test_spec".to_string(),
            effective: "2026-01-01".to_string(),
            spec_effective_from: None,
            spec_effective_to: None,
            results,
            rows: Vec::new(),
        };

        let json = serde_json::to_string(&crate::api::Response::from(&response)).unwrap();
        assert!(json.contains("test_spec"));
        assert!(json.contains("test_rule"));
        assert!(json.contains("\"number\":\"42\""));
        assert!(!json.contains("lemma_type"));
    }

    #[test]
    fn response_number_json_never_uses_fraction_notation() {
        use crate::computation::rational::decimal_to_rational;

        let rational = decimal_to_rational(Decimal::new(1, 1) / Decimal::new(3, 1)).unwrap();
        let decimal_string = rational.try_to_decimal().unwrap().to_string();
        let mut results = IndexMap::new();
        results.insert(
            "third".to_string(),
            RuleResult::from_operation_result(
                dummy_evaluated_rule("third", primitive_number_arc().as_ref()),
                &OperationResult::from_literal(LiteralValue::number_from_decimal(
                    rational.try_to_decimal().unwrap(),
                )),
                primitive_number_arc().as_ref(),
                &empty_family_catalog(),
                None,
                Vec::new(),
            ),
        );
        // Override committed decimal number field to match serialization path under test
        if let Some(rule) = results.get_mut("third") {
            let decimal = rational.try_to_decimal().unwrap();
            rule.result = Some(crate::result_value::RuleResultValue {
                result: Some(decimal_string.clone()),
                number: Some(decimal),
                ..Default::default()
            });
        }

        let response = Response {
            spec_name: "test".to_string(),
            effective: "test".to_string(),
            spec_effective_from: None,
            spec_effective_to: None,
            results,
            rows: Vec::new(),
        };

        let json: serde_json::Value = serde_json::from_str(
            &serde_json::to_string(&crate::api::Response::from(&response)).unwrap(),
        )
        .unwrap();
        let number = json["results"]["third"]["number"]
            .as_str()
            .expect("number must be a JSON string");
        assert!(
            !number.contains('/'),
            "API decimal string must not use fraction notation, got {number}"
        );
    }

    #[test]
    fn test_rule_result_veto() {
        let missing = RuleResult::from_operation_result(
            dummy_evaluated_rule("rule3", &LemmaType::veto_type()),
            &OperationResult::Veto(VetoType::missing_data(
                DataPath::new(vec![], "data1".to_string()),
                None,
            )),
            &LemmaType::veto_type(),
            &empty_family_catalog(),
            None,
            vec!["data1".to_string()],
        );
        assert!(missing.vetoed);
        assert!(missing.veto_reason.as_ref().unwrap().contains("data1"));

        let veto = RuleResult::from_operation_result(
            dummy_evaluated_rule("rule4", &LemmaType::veto_type()),
            &OperationResult::Veto(VetoType::UserDefined {
                message: Some("Vetoed".to_string()),
            }),
            &LemmaType::veto_type(),
            &empty_family_catalog(),
            None,
            Vec::new(),
        );
        assert_eq!(veto.veto_reason.as_deref(), Some("Vetoed"));
    }

    /// Attach hole: MissingData + empty missing_data is a BUG, not a silent stall.
    #[test]
    #[should_panic(expected = "BUG: MissingData")]
    fn missing_data_veto_must_not_attach_empty_missing_data_list() {
        RuleResult::from_operation_result(
            dummy_evaluated_rule("rule3", &LemmaType::veto_type()),
            &OperationResult::Veto(VetoType::missing_data(
                DataPath::new(vec![], "data1".to_string()),
                None,
            )),
            &LemmaType::veto_type(),
            &empty_family_catalog(),
            None,
            Vec::new(),
        );
    }

    #[test]
    #[should_panic(expected = "BUG: MissingData")]
    fn missing_data_veto_must_include_veto_path_in_list() {
        RuleResult::from_operation_result(
            dummy_evaluated_rule("rule3", &LemmaType::veto_type()),
            &OperationResult::Veto(VetoType::missing_data(
                DataPath::new(vec![], "data1".to_string()),
                None,
            )),
            &LemmaType::veto_type(),
            &empty_family_catalog(),
            None,
            vec!["other".to_string()],
        );
    }

    #[test]
    #[should_panic(expected = "BUG: missing_data must be empty")]
    fn non_missing_data_result_must_not_attach_leftover_missing_data() {
        RuleResult::from_operation_result(
            dummy_evaluated_rule("rule4", &LemmaType::veto_type()),
            &OperationResult::Veto(VetoType::UserDefined {
                message: Some("Vetoed".to_string()),
            }),
            &LemmaType::veto_type(),
            &empty_family_catalog(),
            None,
            vec!["leftover".to_string()],
        );
    }

    #[test]
    fn rule_result_value_out_of_memory_is_not_decimal_limit_veto() {
        let result = vetoed_rule_result_for_rule_result_value_failure(
            dummy_evaluated_rule("rule", primitive_number_arc().as_ref()),
            primitive_number_arc().as_ref(),
            None,
            RuleResultValueFailure::OutOfMemory,
            Vec::new(),
        );
        assert_eq!(
            result.veto_reason.as_deref(),
            Some("The calculation ran out of memory.")
        );
        assert_ne!(
            result.veto_reason.as_deref(),
            Some("The calculated result exceeds the decimal value limit.")
        );
    }

    #[test]
    fn rule_result_value_decimal_limit_uses_commit_message() {
        let result = vetoed_rule_result_for_rule_result_value_failure(
            dummy_evaluated_rule("rule", primitive_number_arc().as_ref()),
            primitive_number_arc().as_ref(),
            None,
            RuleResultValueFailure::DecimalLimit,
            Vec::new(),
        );
        assert_eq!(
            result.veto_reason.as_deref(),
            Some("The calculated result exceeds the decimal value limit.")
        );
    }

    fn test_money_type() -> LemmaType {
        LemmaType::new(
            "money".to_string(),
            TypeSpecification::Measure {
                minimum: None,
                maximum: None,
                decimals: Some(2),
                units: MeasureUnits::from(vec![
                    MeasureUnit {
                        name: "eur".to_string(),
                        factor: crate::computation::rational::rational_one(),
                        derived_measure_factors: Vec::new(),
                        decomposition: BaseMeasureVector::new(),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                    MeasureUnit {
                        name: "usd".to_string(),
                        factor: crate::computation::rational::decimal_to_rational(Decimal::new(
                            91, 2,
                        ))
                        .expect("factor"),
                        derived_measure_factors: Vec::new(),
                        decomposition: BaseMeasureVector::new(),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                ]),
                traits: Vec::new(),
                decomposition: Some(BaseMeasureVector::new()),
                unit: None,
                help: String::new(),
            },
            TypeExtends::Primitive,
        )
    }

    #[test]
    fn measure_rule_result_value_uses_rule_type_when_expression_index_empty() {
        let money = test_money_type();
        let family_units = family_catalog_for_money(&money);
        let ten_usd = LiteralValue {
            value: ValueKind::Measure(
                crate::computation::rational::checked_mul(
                    &crate::computation::rational::decimal_to_rational(Decimal::from(10))
                        .expect("ten"),
                    &crate::computation::rational::decimal_to_rational(Decimal::new(91, 2))
                        .expect("usd factor"),
                )
                .expect("canonical usd"),
            ),
        };
        let result = RuleResult::from_operation_result(
            dummy_evaluated_rule("total", &money),
            &OperationResult::from_literal(ten_usd),
            &money,
            &family_units,
            None,
            Vec::new(),
        );
        let measure = result
            .result
            .as_ref()
            .expect("value")
            .measure
            .clone()
            .expect("measure map");
        assert_eq!(measure.get("usd"), Some(&dec("10.00")));
        assert!(measure.contains_key("eur"));
    }

    #[test]
    fn test_measure_rule_result_value_multi_unit() {
        let money = test_money_type();
        let family_units = family_catalog_for_money(&money);
        let ten_eur = LiteralValue {
            value: ValueKind::Measure(
                crate::computation::rational::decimal_to_rational(Decimal::from(10)).expect("ten"),
            ),
        };
        let result = RuleResult::from_operation_result(
            dummy_evaluated_rule("total", &money),
            &OperationResult::from_literal(ten_eur),
            &money,
            &family_units,
            None,
            Vec::new(),
        );
        let measure = result
            .result
            .as_ref()
            .expect("value")
            .measure
            .clone()
            .expect("measure map");
        assert_eq!(measure.get("eur"), Some(&dec("10.00")));
        assert_eq!(measure.get("usd"), Some(&dec("10.99")));
    }

    #[test]
    fn measure_rule_result_value_respects_decimals_on_unit_conversion() {
        let money = LemmaType::new(
            "money".to_string(),
            TypeSpecification::Measure {
                minimum: None,
                maximum: None,
                decimals: Some(2),
                units: MeasureUnits::from(vec![
                    MeasureUnit {
                        name: "eur".to_string(),
                        factor: crate::computation::rational::rational_one(),
                        derived_measure_factors: Vec::new(),
                        decomposition: BaseMeasureVector::new(),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                    MeasureUnit {
                        name: "usd".to_string(),
                        factor: crate::computation::rational::decimal_to_rational(Decimal::new(
                            84, 2,
                        ))
                        .expect("usd factor"),
                        derived_measure_factors: Vec::new(),
                        decomposition: BaseMeasureVector::new(),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                ]),
                traits: Vec::new(),
                decomposition: Some(BaseMeasureVector::new()),
                unit: None,
                help: String::new(),
            },
            TypeExtends::Primitive,
        );
        let family_units = family_catalog_for_money(&money);
        let three_twelve_eur = LiteralValue {
            value: ValueKind::Measure(
                crate::computation::rational::decimal_to_rational(Decimal::new(312, 2))
                    .expect("3.12 eur canonical"),
            ),
        };
        let result = RuleResult::from_operation_result(
            dummy_evaluated_rule("delivery_cost", &money),
            &OperationResult::from_literal(three_twelve_eur),
            &money,
            &family_units,
            None,
            Vec::new(),
        );
        let measure = result
            .result
            .as_ref()
            .expect("value")
            .measure
            .clone()
            .expect("measure map");
        assert_eq!(measure.get("eur"), Some(&dec("3.12")));
        assert_eq!(measure.get("usd"), Some(&dec("3.71")));
    }

    #[test]
    fn test_ratio_rule_result_value_multi_unit() {
        let ratio_type = LemmaType::new(
            "rate".to_string(),
            TypeSpecification::Ratio {
                minimum: None,
                maximum: None,
                decimals: None,
                units: RatioUnits::from(vec![
                    RatioUnit {
                        name: "percent".to_string(),
                        value: crate::computation::rational::decimal_to_rational(Decimal::from(
                            100,
                        ))
                        .expect("percent"),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                    RatioUnit {
                        name: "basis_points".to_string(),
                        value: crate::computation::rational::decimal_to_rational(Decimal::from(
                            10_000,
                        ))
                        .expect("bp"),
                        minimum: None,
                        maximum: None,
                        suggestion_magnitude: None,
                    },
                ]),
                unit: None,
                help: String::new(),
            },
            TypeExtends::Primitive,
        );
        let family_units = family_catalog_for_ratio(&ratio_type);
        let half = crate::computation::rational::rational_new(1, 2);
        let lit = LiteralValue {
            value: ValueKind::Ratio(half),
        };
        let result = RuleResult::from_operation_result(
            dummy_evaluated_rule("rate_out", &ratio_type),
            &OperationResult::from_literal(lit),
            &ratio_type,
            &family_units,
            None,
            Vec::new(),
        );
        let ratio = result
            .result
            .as_ref()
            .expect("value")
            .ratio
            .clone()
            .expect("ratio map");
        assert_eq!(ratio.get("percent"), Some(&dec("50")));
        assert_eq!(ratio.get("basis_points"), Some(&dec("5000")));
    }

    #[test]
    fn test_measure_rule_result_value_cross_spec_import() {
        use crate::parsing::source::SourceType;
        use crate::Engine;

        let mut engine = Engine::new();
        engine
            .load([(
                SourceType::Path(std::sync::Arc::new(std::path::PathBuf::from("t.lemma"))),
                r#"
spec consumer 2025-01-01
uses d: dep 2025-10-01
rule out: d.doubled

spec dep 2025-01-01
uses c: child 2025-06-01
data money: c.money
data p: 5 usd
rule doubled: p * 2

spec child 2025-01-01
data money: measure
 -> unit eur: 1.00
 -> decimals 2

spec child 2025-06-01
data money: measure
 -> unit eur: 1.00
 -> unit usd: 0.91
 -> decimals 2
"#
                .to_string(),
            )])
            .expect("load");
        let effective = crate::literals::DateTimeValue {
            year: 2025,
            month: 3,
            day: 1,
            hour: 0,
            minute: 0,
            second: 0,
            microsecond: 0,
            timezone: None,

            granularity: DateGranularity::Full,
        };
        let response = engine
            .evaluate(
                None,
                "consumer",
                Some(&effective),
                IndexMap::new(),
                None,
                false,
            )
            .expect("evaluate");
        let out = response.results.get("out").expect("out rule");
        assert!(!out.vetoed);
        let measure = out
            .result
            .as_ref()
            .expect("value")
            .measure
            .as_ref()
            .expect("measure map");
        assert!(measure.contains_key("usd"));
        assert!(measure.contains_key("eur"));
    }

    #[test]
    fn to_literal_roundtrips_number() {
        let literal = LiteralValue::number_from_decimal(Decimal::from(42));
        let rule_result = RuleResult::from_operation_result(
            dummy_evaluated_rule("answer", primitive_number_arc().as_ref()),
            &OperationResult::from_literal(literal.clone()),
            primitive_number_arc().as_ref(),
            &empty_family_catalog(),
            None,
            Vec::new(),
        );
        assert_eq!(rule_result.to_literal(), literal);
    }

    #[test]
    fn to_literal_roundtrips_measure() {
        let money = test_money_type();
        let family_units = family_catalog_for_money(&money);
        let literal = LiteralValue::measure(crate::computation::rational::rational_new(60, 1));
        let rule_result = RuleResult::from_operation_result(
            dummy_evaluated_rule("pay", &money),
            &OperationResult::from_literal(literal.clone()),
            &money,
            &family_units,
            None,
            Vec::new(),
        );
        assert_eq!(rule_result.to_literal(), literal);
    }
}