BREP_app 0.4.0

//! The assembly BOM panel — the parts list on the shared
//! [`crate::column_tree`] widget.
//!
//! This module is the BOM-shaped half: it turns the engine's component
//! projection into the widget's generic rows, and turns the widget's generic
//! edits back into the two attribute stores. The widget itself knows none of
//! this, which is what lets a second consumer (the wire-harness connection
//! list) reuse it untouched.
//!
//! # Packed and unpacked
//!
//! Two views of the same occurrences.
//!
//! * **Unpacked** — one row per placement. `Quantity` reads 1.
//! * **Packed** — one row per DISTINCT part **whose occurrence data matches**.
//!   Two occurrences roll up only when they agree on EVERY occurrence field;
//!   one differing Reference Designator and they stay two rows. `Quantity` is
//!   the size of the group, read-only in both views because it is derived and
//!   so can never disagree with the model.
//!
//! Editing a packed row applies to every occurrence it rolls up, and that
//! fan-out is ONE undo step, not N — `EngineState::set_occurrence_attribute`
//! takes the whole group and checkpoints once. A part-level edit is inherently
//! the same shape (the value lives on the part, so every occurrence of it sees
//! the change) and is one undo step for the same reason.
//!
//! # Nested sub-assembly rows are READ-ONLY
//!
//! A rigid sub-assembly's internal components appear as child rows, so the BOM
//! reads as the tree it is — but their part and occurrence data lives in the
//! SUB-ASSEMBLY's own document, not this one. That is the rigid-nesting model
//! (the same reason `EngineState::export_bom_csv` reports a sub-assembly as one
//! row at this level), not a limit of the widget: editing them means opening
//! that document. They are drawn weak and take no edit.
//!
//! # The row ACTION MENU
//!
//! The rightmost column's `⋯` opens a menu — and so does a right-click
//! anywhere on the row; both are the widget's ONE menu, declared here as
//! [`RowAction`]s. Its entries are the SHARED component actions
//! ([`crate::panels::component_actions`], the same dispatcher the assembly
//! structure tree's row buttons route through) plus this panel's own
//! "Edit feature" — the `✎` button the menu replaced.
//!
//! Availability is decided PER ROW here, because only this panel knows what
//! refuses what: a fixed component will not Move, an embedded-only part has no
//! source document to Open, and a PACKED row standing for several placements
//! refuses the per-instance actions rather than guessing which placement was
//! meant (and Delete across a group would be N undo steps, not the one this
//! panel promises). Refused entries are greyed with the reason, never hidden.
//!
//! # The write lanes
//!
//! * occurrence field → `set_occurrence_attribute(ids, key, value)`.
//! * part field → `set_part_attribute(part, key, value)`, then the shared
//!   write-through lane ([`crate::panels::parts_library::write_through`]) so
//!   the part's file and the entry's signature keep agreeing. There is no
//!   second write path.

use crate::automation::hit_keys::HitKeyDoc;
use crate::column_tree::{self, CellEdit, ColumnLayout, ColumnTreeSpec, RowAction, RowNode};
use crate::panels::parts_library;
use crate::panels::component_actions::{
    run_component_action, ComponentAction, ComponentActionRequest,
};
use crate::panels::assembly_components::{self, ChainNode, ComponentRow};
use crate::panels::update_components::UpdateComponents;
use crate::panels::bom_columns::{
    self, ParsedColumns, Scope, FLAGS_KEY, ITEM_KEY, QUANTITY_KEY, VISIBLE_KEY,
};
use crate::store::ModelStore;
use brep_render::engine_state::EngineState;
use eframe::egui;
use serde_json::Value;
use std::collections::{BTreeMap, HashMap, HashSet};

/// The row menu's own entry: roll to the component's feature and open it in
/// the history tree. Not a [`ComponentAction`] — the shared set is the
/// COMPONENT vocabulary (spec §8.5) and the context bar draws a button per
/// member of it, so a document-navigation entry does not belong in there. The
/// assembly structure tree keeps this action locally for the same reason.
const EDIT_FEATURE: &str = "edit-feature";

/// What a BOM frame hands back to the shell.
#[derive(Default)]
pub struct BomOutcome {
    /// A feature id to roll to + expand in the history tree (the row menu's
    /// "Edit feature") — the structure panel's `focus` contract, verbatim, so
    /// the shell routes both the same way.
    pub focus: Option<String>,
    /// A document-level flow the SHELL owns (Edit Part → open the part's own
    /// document tab), handed
    /// back by the shared component-action dispatcher exactly as the selection
    /// context bar hands it back.
    pub component: Option<ComponentActionRequest>,
}

/// One occurrence, flattened out of the engine's projection.
#[derive(Clone)]
struct Occurrence {
    /// The owning ACOMP feature id.
    id: String,
    part_name: String,
    /// This occurrence's own attribute record.
    attributes: Value,
    selected: bool,
    /// Grounded (the ⏚ badge, and what refuses Move).
    fixed: bool,
    /// The library entry no longer matches its store source (the ↻ badge).
    outdated: bool,
    /// Worst constraint status referencing this component, if any.
    status: Option<String>,
    /// Every member solid currently visible.
    visible: bool,
    /// Member scene names, for the visibility toggle.
    solids: Vec<String>,
    /// Read-only nested component rows, from the member name chains. FULL
    /// depth: a sub-assembly inside a sub-assembly renders as such.
    children: Vec<ChainNode>,
}

/// The BOM panel's transient UI state. The data lives in the document; the
/// column arrangement lives in the settings text; this holds only what is true
/// for this session.
pub struct BomPanel {
    hits: HashMap<String, egui::Rect>,
    /// The widget's live column arrangement. Rebuilt from the settings text
    /// whenever that text changes, keeping session-only widths + sort.
    layout: ColumnLayout,
    /// The settings text `layout` was built from — the change detector.
    layout_source: String,
    /// The parsed configuration for `layout_source`.
    parsed: ParsedColumns,
    /// Packed (one row per distinct part + occurrence data) or unpacked (one
    /// row per placement).
    packed: bool,
    /// Rows explicitly collapsed, by row id (absent = open).
    collapsed: HashSet<String>,
}

impl Default for BomPanel {
    fn default() -> Self {
        Self::new()
    }
}

impl BomPanel {
    pub fn new() -> Self {
        Self {
            hits: HashMap::new(),
            layout: ColumnLayout::default(),
            layout_source: String::new(),
            parsed: ParsedColumns::default(),
            // Packed is the BOM a person asks for: a parts list, not a
            // placement list.
            packed: true,
            collapsed: HashSet::new(),
        }
    }

    /// Draw the BOM. Snapshots the projection, draws the column tree, then
    /// applies at most one deferred engine mutation — the shared panel
    /// pattern, and the reason the draw can borrow `state` immutably.
    pub fn show(
        &mut self,
        ui: &mut egui::Ui,
        state: &mut EngineState,
        store: &dyn ModelStore,
        updates: &UpdateComponents,
    ) -> BomOutcome {
        self.hits.clear();
        // What is actually VISIBLE of this pane. Every other rect below is a
        // raw LAYOUT rect, so a widget scrolled past the pane's edge is still
        // published while being unclickable — a headed verifier has to scroll
        // it into this rect first. (The constraints panel publishes
        // `acon:panel:clip` for exactly the same reason.)
        self.hits.insert("bom:panel:clip".into(), ui.clip_rect());
        let mut outcome = BomOutcome::default();
        state.ensure_assembly_synced();

        self.sync_columns(state);
        let component_rows = assembly_components::snapshot(state, updates);
        let occurrences = occurrences_from(state, &component_rows);
        let groups = group(&occurrences, self.packed, &self.packing_fields());

        // --- header: the packed/unpacked switch ------------------------------
        ui.horizontal(|ui| {
            let packed = ui
                .selectable_label(self.packed, "Packed")
                .on_hover_text("One row per part, rolled up where every occurrence field matches");
            self.hits.insert("bom:packed".into(), packed.rect);
            if packed.clicked() {
                self.packed = true;
            }
            let unpacked = ui
                .selectable_label(!self.packed, "Unpacked")
                .on_hover_text("One row per individual instance");
            self.hits.insert("bom:unpacked".into(), unpacked.rect);
            if unpacked.clicked() {
                self.packed = false;
            }
            let expand = ui
                .button("Expand all")
                .on_hover_text("Expand every row with nested components");
            self.hits.insert("bom:expand-all".into(), expand.rect);
            if expand.clicked() {
                self.collapsed.clear();
            }
            let collapse = ui
                .button("Collapse all")
                .on_hover_text("Collapse every row with nested components");
            self.hits.insert("bom:collapse-all".into(), collapse.rect);
            if collapse.clicked() {
                // Every key the tree can hold: the group rows and, beneath
                // them, every nested chain node — collapse-all has to fold the
                // WHOLE tree, at every depth, with no key drift.
                self.collapsed = collapsible_keys(&groups);
            }
            ui.label(
                egui::RichText::new(format!("{} rows / {} occurrences", groups.len(), occurrences.len()))
                    .weak(),
            );
        });
        ui.add_space(2.0);

        // --- the tree ---------------------------------------------------------
        let rows: Vec<RowNode> = groups
            .iter()
            .map(|group| self.row_for(state, group))
            .collect();
        let specs = bom_columns::column_specs(&self.parsed);
        let mut root_cells: HashMap<String, Value> = HashMap::new();
        root_cells.insert(
            QUANTITY_KEY.to_string(),
            Value::from(occurrences.len() as u64),
        );
        let spec = ColumnTreeSpec {
            id: "bom",
            columns: &specs,
            root_label: Some("Assembly"),
            root_cells: Some(&root_cells),
            empty_hint: Some("(no components — insert one via Add new feature)"),
            hits_prefix: "",
        };
        let out = column_tree::column_tree(
            ui,
            &spec,
            &mut self.layout,
            &rows,
            Some(&mut self.hits),
        );

        // --- act on what the widget reported ---------------------------------
        if out.layout_changed {
            self.persist_layout(state, store);
        }
        if let Some(id) = &out.toggled {
            if !self.collapsed.remove(id) {
                self.collapsed.insert(id.clone());
            }
        }
        if let Some(id) = &out.clicked {
            if let Some(group) = groups.iter().find(|group| group.key == *id) {
                state.select_components(&group.ids);
            }
        }
        // The row menu. Engine-mutating actions run in the SHARED dispatcher
        // (one truth, one undo lane, the same one the structure tree's buttons
        // and the context bar use); the two document-level flows come back as
        // a request for the shell.
        let mut acted = false;
        for click in &out.actions {
            let Some(group) = groups.iter().find(|group| group.key == click.row_id) else {
                continue;
            };
            let Some(first) = group.ids.first() else {
                continue;
            };
            acted = true;
            if click.action == EDIT_FEATURE {
                if let Some(index) = state.history.index_of(first) {
                    state.roll_to(index);
                }
                outcome.focus = Some(first.clone());
            } else if let Some(action) = ComponentAction::from_id(&click.action) {
                outcome.component = run_component_action(state, action, first);
            }
        }
        // At most ONE edit lands per frame (egui gives one widget the focus),
        // and applying it re-runs the history, so take the first and let the
        // next frame carry any other. An action that just deleted the feature
        // this edit names would make the write fail loudly, so the action wins
        // the frame and the edit comes back on the next one.
        if !acted {
            if let Some(edit) = out.edits.first() {
                if edit.column == VISIBLE_KEY {
                    // Scene state, not a stored attribute: write it straight
                    // through to every member solid the row stands for.
                    let visible = edit.value.as_bool().unwrap_or(true);
                    if let Some(group) = groups.iter().find(|g| g.key == edit.row_id) {
                        for solid in &group.solids {
                            state.set_visible(solid, visible);
                        }
                    }
                } else {
                    self.apply_edit(state, store, &groups, edit);
                }
            }
        }

        // The component oracle the headed verifiers read. Published from the
        // shared projection rather than from these rows, so it stays engine
        // truth: `verify_bom_menu` uses it to prove a menu action reached the
        // engine, and proving that against the BOM's own rendering would be
        // checking the panel against itself.
        assembly_components::publish_tree(&component_rows);

        if crate::automation::registry::enabled() {
            let listing: Vec<Value> = groups
                .iter()
                .map(|group| {
                    serde_json::json!({
                        "key": group.key,
                        "partName": group.part_name,
                        "ids": group.ids,
                        "quantity": group.ids.len(),
                    })
                })
                .collect();
            crate::automation::registry::publish("__brepBom", "BOM groups {key, partName, ids, quantity}", &Value::Array(listing).to_string());
            crate::automation::registry::publish("__brepBomHit", "BOM widget rects (BOM:, cell:)", &self.hits_json());
        }

        outcome
    }

    /// Rebuild the column layout when the settings text has changed. Widths
    /// and sort are session state and survive the rebuild — a re-parse must
    /// not resize the table under the user's hands.
    fn sync_columns(&mut self, state: &EngineState) {
        let text = bom_columns::effective_text(&state.settings.bom_columns);
        if text == self.layout_source {
            return;
        }
        self.parsed = bom_columns::parse(&text);
        self.layout = bom_columns::layout_from(&self.parsed, &self.layout);
        self.layout_source = text;
    }

    /// Fold a layout the user changed BY DRAGGING back into the settings text,
    /// so the table and the configuration can never disagree.
    fn persist_layout(&mut self, state: &mut EngineState, store: &dyn ModelStore) {
        let columns = bom_columns::columns_from_layout(&self.parsed, &self.layout);
        let text = bom_columns::serialize(
            &columns,
            &self.parsed.preserved,
            // Dragging a column across the freeze boundary moves the marker,
            // exactly as dragging one across another moves its line.
            bom_columns::frozen_from_layout(&self.layout),
        );
        let mut settings: Value =
            serde_json::from_str(&state.settings_json()).unwrap_or(Value::Null);
        let Some(object) = settings.as_object_mut() else {
            return;
        };
        object.insert("bomColumns".into(), Value::String(text.clone()));
        let json = settings.to_string();
        let _ = state.apply_settings_json(&json);
        let _ = store.write(crate::store::SETTINGS_KEY, &json);
        // Adopt it as our own source so `sync_columns` does not now rebuild
        // (and discard) the very layout the user just dragged.
        self.parsed = bom_columns::parse(&text);
        self.layout_source = text;
    }

    /// The occurrence fields a packed row is keyed by: the VISIBLE
    /// occurrence-scoped columns, in the arrangement's order.
    ///
    /// Visible, not every field: a BOM row stands for what the table SHOWS, so
    /// two placements that differ only in a column nobody is looking at are one
    /// line. Part-scoped columns are identical across every placement of a part
    /// by definition, so they cannot split a row and are not consulted; the
    /// derived quantity is not a field at all.
    fn packing_fields(&self) -> Vec<String> {
        self.parsed
            .columns
            .iter()
            .filter(|column| column.scope == Scope::Occurrence)
            .filter(|column| column.key() != QUANTITY_KEY)
            .filter(|column| !self.layout.hidden.contains(&column.key()))
            .map(|column| column.field.clone())
            .collect()
    }

    /// Build one widget row for a group: the tree cell, every configured
    /// column's value, and the read-only nested component rows beneath.
    fn row_for(&self, state: &EngineState, group: &Group) -> RowNode {
        let mut cells: HashMap<String, Value> = HashMap::new();
        let label = if self.packed {
            group.part_name.clone()
        } else {
            format!("{} ({})", group.part_name, group.key)
        };
        cells.insert(ITEM_KEY.to_string(), Value::String(label));
        cells.insert(VISIBLE_KEY.to_string(), Value::Bool(group.visible));
        cells.insert(FLAGS_KEY.to_string(), Value::Array(badges(group)));
        // Quantity is DERIVED — the size of the roll-up — and never stored.
        cells.insert(
            QUANTITY_KEY.to_string(),
            Value::from(group.ids.len() as u64),
        );

        let part_attributes = state.part_attributes(&group.part_name);
        for column in &self.parsed.columns {
            let key = column.key();
            if key == QUANTITY_KEY {
                continue;
            }
            let source = match column.scope {
                Scope::Part => &part_attributes,
                Scope::Occurrence => &group.attributes,
            };
            if let Some(value) = source.get(&column.field) {
                cells.insert(key, value.clone());
            }
        }

        RowNode {
            id: group.key.clone(),
            cells,
            editable: true,
            selected: group.selected,
            expanded: !self.collapsed.contains(&group.key),
            actions: actions_for(state, group),
            // Nested components belong to the sub-assembly's own document, so
            // they show but never take an edit (rigid nesting). Rendered to
            // FULL depth: a sub-assembly inside a sub-assembly is a real thing
            // in the model and the list has to be able to show it.
            children: chain_rows(&group.key, &group.children),
        }
    }

    /// Route ONE cell edit to its store. The column's scope decides which:
    /// occurrence fields fan out across the group's ACOMPs in one undo step,
    /// part fields go to the part document and then through the shared
    /// write-through.
    fn apply_edit(
        &self,
        state: &mut EngineState,
        store: &dyn ModelStore,
        groups: &[Group],
        edit: &CellEdit,
    ) {
        let Some(group) = groups.iter().find(|group| group.key == edit.row_id) else {
            return; // a nested sub-assembly row — read-only, nothing to write
        };
        let Some(column) = self
            .parsed
            .columns
            .iter()
            .find(|column| column.key() == edit.column)
        else {
            return;
        };
        match column.scope {
            Scope::Occurrence => {
                // The fan-out: EVERY occurrence the packed row rolls up, as
                // ONE undo step.
                if let Err(error) =
                    state.set_occurrence_attribute(&group.ids, &column.field, edit.value.clone())
                {
                    state.push_notice(format!("BOM: {error}"));
                }
            }
            Scope::Part => {
                // The part's `(sourceKey, signature-as-inserted)` must be read
                // BEFORE the edit re-stamps the signature — that pair is what
                // the write-through compares the file against.
                let target = state.part_source(&group.part_name).and_then(|(key, sig)| {
                    (!key.is_empty()).then_some((key, sig))
                });
                if let Err(error) =
                    state.set_part_attribute(&group.part_name, &column.field, edit.value.clone())
                {
                    state.push_notice(format!("BOM: {error}"));
                    return;
                }
                // The part document that just changed is saved back to the file
                // it came from, through the shared write-through lane, so the
                // entry's signature and the file agree.
                if let Some(document) = state.part_document_json(&group.part_name) {
                    parts_library::write_through(
                        state,
                        store,
                        &group.part_name,
                        target.as_ref(),
                        &document,
                    );
                }
            }
        }
    }

    /// The published widget hit-rects for the headed verifier.
    pub fn hits_json(&self) -> String {
        crate::automation::hit_rects::hits_json(&self.hits)
    }
}

/// The row menu for one group: "Edit feature" (this panel's own) then the
/// SHARED component actions in bar order, each refused-with-a-reason where this
/// row cannot honour it.
///
/// The per-INSTANCE actions (Move, Fix/Unfix, Delete) are refused on a PACKED
/// row that rolls up more than one placement: acting on "the first" of four is
/// a trap, and fanning Delete or Fix out across the group would be N undo steps
/// where every other BOM edit is one. The part-level flows (Edit in place, Open
/// Part) mean the same thing for every placement, so they stay live; and
/// "Edit feature" only rolls the history, which is what the ✎ button it
/// replaced always did.
fn actions_for(state: &EngineState, group: &Group) -> Vec<RowAction> {
    let Some(first) = group.ids.first() else {
        return Vec::new();
    };
    let fixed = state
        .component_info(first)
        .map(|info| info.fixed)
        .unwrap_or(false);
    let rolled_up = group.ids.len() > 1;
    let unpack = |verb: &str| {
        format!(
            "{} placements on this row — switch to Unpacked to {verb} one",
            group.ids.len()
        )
    };
    // An embedded-only part (no `sourceKey`) has no document to open.
    let embedded = !state
        .part_source(&group.part_name)
        .is_some_and(|(key, _)| !key.is_empty());

    let mut actions = vec![RowAction::new(EDIT_FEATURE, "\u{270E} Edit feature")
        .tooltip("Roll to this component's feature and open it in the history")];
    for action in ComponentAction::ALL {
        let entry = RowAction::new(action.id(), action.label(fixed)).tooltip(action.tooltip());
        let entry = match action {
            ComponentAction::Move if fixed => {
                entry.disabled("This component is fixed — unfix it before moving it")
            }
            ComponentAction::Move if rolled_up => entry.disabled(unpack("move")),
            ComponentAction::ToggleFixed if rolled_up => entry.disabled(unpack("fix or unfix")),
            ComponentAction::Delete if rolled_up => entry.disabled(unpack("delete")),
            ComponentAction::OpenPart if embedded => {
                entry.disabled("This part is embedded in the assembly — it has no source document")
            }
            _ => entry,
        };
        actions.push(match action {
            // The destructive tail, fenced off from the rest.
            ComponentAction::Delete => entry.separator_above().destructive(),
            _ => entry,
        });
    }
    actions
}

/// Every key the tree can place in `collapsed`: each group row that has nested
/// components, and every nested chain node beneath it that has children of its
/// own. Collapse-all writes exactly this set.
fn collapsible_keys(groups: &[Group]) -> HashSet<String> {
    /// Does this node own a nested COMPONENT anywhere below it? Bodies do not
    /// count — they are not drawn, so a node holding only bodies has nothing to
    /// collapse and must not claim a key.
    fn owns_component(nodes: &[ChainNode]) -> bool {
        nodes
            .iter()
            .any(|node| assembly_components::is_acomp_segment(&node.label))
    }
    fn walk(parent: &str, nodes: &[ChainNode], out: &mut HashSet<String>) {
        for node in nodes
            .iter()
            .filter(|node| assembly_components::is_acomp_segment(&node.label))
        {
            let id = format!("{parent}:{}", node.label);
            if owns_component(&node.children) {
                out.insert(id.clone());
            }
            walk(&id, &node.children, out);
        }
    }
    let mut out = HashSet::new();
    for group in groups {
        if owns_component(&group.children) {
            out.insert(group.key.clone());
        }
        walk(&group.key, &group.children, &mut out);
    }
    out
}

/// The row's status glyphs: grounded, outdated, and the worst constraint
/// status referencing it. Colour carries the meaning for the last two, which is
/// why these are badges rather than text.
fn badges(group: &Group) -> Vec<Value> {
    let mut out = Vec::new();
    if group.fixed {
        out.push(serde_json::json!({
            "glyph": assembly_components::FIXED_GLYPH,
            "tooltip": "Grounded — unfix it before moving it",
        }));
    }
    if group.outdated {
        out.push(serde_json::json!({
            "glyph": assembly_components::OUTDATED_GLYPH,
            "color": color_hex(assembly_components::OUTDATED_AMBER),
            "tooltip": "The source part has changed since this was inserted",
        }));
    }
    if let Some(status) = &group.status {
        out.push(serde_json::json!({
            "glyph": "\u{25CF}",
            "color": brep_render::assembly_status::status_color_hex(status),
            "tooltip": format!("Constraint status: {status}"),
        }));
    }
    out
}

/// `Color32` → the `#rrggbb` the widget's badge cell parses. (Constraint
/// statuses have their own [`brep_render::assembly_status::status_color_hex`];
/// this is for the badge colours the app owns.)
fn color_hex(color: egui::Color32) -> String {
    crate::color::rgb_to_hex([color.r(), color.g(), color.b()])
}

/// Nested COMPONENT rows for one group, to full depth. Read-only throughout:
/// these belong to the sub-assembly's own document, so they carry no cells the
/// BOM may edit and offer no actions in THIS document.
///
/// Only `ACOMP<n>` nodes appear. A BOM lists PARTS and the sub-assemblies a
/// part contains — the bodies inside a part are that part's internals and live
/// on the Scene tree, not here. Filtering recursively also means a part whose
/// chain holds nothing but bodies ends up with no children at all, so the
/// widget draws no collapse box on a row with nothing behind it.
fn chain_rows(parent: &str, nodes: &[ChainNode]) -> Vec<RowNode> {
    nodes
        .iter()
        .filter(|node| assembly_components::is_acomp_segment(&node.label))
        .map(|node| {
            let id = format!("{parent}:{}", node.label);
            let mut cells = HashMap::new();
            cells.insert(ITEM_KEY.to_string(), Value::String(node.label.clone()));
            RowNode {
                children: chain_rows(&id, &node.children),
                id,
                cells,
                editable: false,
                selected: false,
                expanded: false,
                actions: Vec::new(),
            }
        })
        .collect()
}

/// Is `candidate` a worse constraint status than `current`? Uses the ONE status
/// map's severity ordering, so a rolled-up row shows the worst of what it
/// stands for rather than whichever placement happened to be first.
fn worse_status(current: Option<&str>, candidate: Option<&str>) -> bool {
    let Some(candidate) = candidate else {
        return false;
    };
    match current {
        None => true,
        Some(current) => {
            brep_render::assembly_status::status_severity(candidate)
                > brep_render::assembly_status::status_severity(current)
        }
    }
}

/// One BOM row's occurrences: the whole group in the packed view, exactly one
/// in the unpacked view.
struct Group {
    /// The row id. In the packed view this is a synthetic group key; in the
    /// unpacked view it is the ACOMP id itself.
    key: String,
    part_name: String,
    /// Every ACOMP this row stands for — what a packed edit fans out across.
    ids: Vec<String>,
    /// The occurrence attributes shared by the whole group (identical by
    /// construction — that is what made them one group).
    attributes: Value,
    selected: bool,
    /// Rolled up across the group: grounded only when EVERY placement is.
    fixed: bool,
    outdated: bool,
    /// Worst status across the group's placements.
    status: Option<String>,
    /// Visible only when EVERY member solid of every placement is.
    visible: bool,
    /// Every member solid the row stands for — what the toggle writes to.
    solids: Vec<String>,
    children: Vec<ChainNode>,
}

/// Flatten the engine's component projection into occurrences.
///
/// The per-component truth (fixed, outdated, constraint-status rollup,
/// visibility, the nested chain) comes from the SHARED projection in
/// [`assembly_components`] — the same rows the headed verifiers read as
/// `__brepAssemblyTree`. The BOM adds only what is its own: the attribute
/// records it edits.
fn occurrences_from(state: &mut EngineState, rows: &[ComponentRow]) -> Vec<Occurrence> {
    rows.iter()
        .map(|row| Occurrence {
            attributes: state.occurrence_attributes(&row.id),
            selected: row.selected,
            fixed: row.fixed,
            outdated: row.outdated,
            status: row.rollup_status.clone(),
            visible: row.visible,
            solids: row.solids.clone(),
            children: row.children.clone(),
            part_name: row.part_name.clone(),
            id: row.id.clone(),
        })
        .collect()
}

/// Group occurrences into BOM rows.
///
/// PACKED rolls up by `(part name, EVERY occurrence field)` — the owner's rule:
/// occurrences that differ in ANY occurrence field stay separate rows, because
/// a rolled-up row would have to show one of two different values and an edit
/// to it would silently overwrite the other. UNPACKED is one row each.
///
/// Group order follows first appearance, which is the engine's deterministic
/// id order, so the table is stable frame to frame before any sort.
fn group(occurrences: &[Occurrence], packed: bool, fields: &[String]) -> Vec<Group> {
    if !packed {
        return occurrences
            .iter()
            .map(|occurrence| Group {
                key: occurrence.id.clone(),
                part_name: occurrence.part_name.clone(),
                ids: vec![occurrence.id.clone()],
                attributes: occurrence.attributes.clone(),
                selected: occurrence.selected,
                fixed: occurrence.fixed,
                outdated: occurrence.outdated,
                status: occurrence.status.clone(),
                visible: occurrence.visible,
                solids: occurrence.solids.clone(),
                children: occurrence.children.clone(),
            })
            .collect();
    }
    let mut order: Vec<String> = Vec::new();
    let mut groups: HashMap<String, Group> = HashMap::new();
    for occurrence in occurrences {
        let key = format!(
            "{}\u{1}{}",
            occurrence.part_name,
            canonical_over(&occurrence.attributes, fields)
        );
        match groups.get_mut(&key) {
            Some(group) => {
                group.ids.push(occurrence.id.clone());
                group.selected |= occurrence.selected;
                // A rolled-up row states what is true of EVERY placement it
                // stands for: grounded only if all are, visible only if all
                // are. Anything else would let one row claim a state a
                // placement behind it does not have.
                group.fixed &= occurrence.fixed;
                group.visible &= occurrence.visible;
                group.outdated |= occurrence.outdated;
                group.solids.extend(occurrence.solids.iter().cloned());
                if worse_status(group.status.as_deref(), occurrence.status.as_deref()) {
                    group.status = occurrence.status.clone();
                }
                for child in &occurrence.children {
                    if !group.children.iter().any(|kept| kept == child) {
                        group.children.push(child.clone());
                    }
                }
            }
            None => {
                order.push(key.clone());
                groups.insert(
                    key,
                    Group {
                        key: String::new(), // filled below, from the group order
                        part_name: occurrence.part_name.clone(),
                        ids: vec![occurrence.id.clone()],
                        attributes: occurrence.attributes.clone(),
                        selected: occurrence.selected,
                        fixed: occurrence.fixed,
                        outdated: occurrence.outdated,
                        status: occurrence.status.clone(),
                        visible: occurrence.visible,
                        solids: occurrence.solids.clone(),
                        children: occurrence.children.clone(),
                    },
                );
            }
        }
    }
    order
        .into_iter()
        .filter_map(|key| groups.remove(&key))
        .map(|mut group| {
            // The row id must be STABLE across frames (it keys collapse state
            // and every out-value) but must not be a raw attribute dump. The
            // first ACOMP of the group is both — deterministic, because the
            // projection is in id order.
            group.key = format!(
                "pack:{}",
                group.ids.first().cloned().unwrap_or_default()
            );
            group
        })
        .collect()
}

/// The packing key's value half: the named fields, in the given order, with a
/// missing field spelled explicitly. Order comes from the column arrangement
/// rather than the record, so two placements whose attributes were WRITTEN in a
/// different order still key the same. (serde_json runs with `preserve_order`
/// in this workspace, so a naive `to_string` of the record would not.)
fn canonical_over(attributes: &Value, fields: &[String]) -> String {
    fields
        .iter()
        .map(|field| {
            let value = attributes
                .get(field)
                .map(Value::to_string)
                .unwrap_or_default();
            format!("{field}={value}")
        })
        .collect::<Vec<_>>()
        .join("\u{2}")
}

// BREP private tests: 3c26b46ba10327e2

/// The hit keys this panel publishes (see `automation::hit_keys`).
pub static HIT_KEYS: &[HitKeyDoc] = &[
    HitKeyDoc { panel: "bom", prefix: "bom:expand-all", meaning: "expand every group", command: None },
    HitKeyDoc { panel: "bom", prefix: "bom:collapse-all", meaning: "collapse every group", command: None },
    HitKeyDoc { panel: "bom", prefix: "bom:packed", meaning: "packed view", command: None },
    HitKeyDoc { panel: "bom", prefix: "bom:unpacked", meaning: "unpacked view", command: None },
    HitKeyDoc { panel: "bom", prefix: "bom:panel:clip", meaning: "the visible region of the pane", command: None },
    HitKeyDoc { panel: "bom", prefix: "BOM:", meaning: "a row action", command: None },
    HitKeyDoc { panel: "bom", prefix: "cell:", meaning: "a table cell (cell:row:column)", command: Some("bom_set_occurrence_attribute") },
    HitKeyDoc { panel: "bom", prefix: "row:", meaning: "a structure-tree row (row:node key)", command: Some("component_select") },
    HitKeyDoc { panel: "bom", prefix: "box:", meaning: "a structure-tree row's expander (box:node key)", command: None },
    HitKeyDoc { panel: "bom", prefix: "col:", meaning: "a table column header (col:field) — click to sort", command: None },
    HitKeyDoc { panel: "bom", prefix: "grip:", meaning: "a column's resize grip (grip:field)", command: None },
    HitKeyDoc { panel: "bom", prefix: "freeze:divider", meaning: "the frozen-column divider", command: None },
];