BREP_app 0.2.1

//! The MULTI-DOCUMENT model — the app holds N open models, exactly ONE of which
//! is active.
//!
//! Before this, the shell owned a single `EngineState` and the document's
//! IDENTITY (its store name + the clean baseline the dirty flag compares
//! against) lived on the file dialog. That pairing is what a document IS, so it
//! moves here: [`Document`] = one engine + its identity, [`Documents`] = the
//! open list + the active index.
//!
//! # Why the accessor lives on `Documents` and not on `BrepApp`
//!
//! Half the shell passes DISJOINT `&mut` borrows of its own fields in one call
//! (`self.history.show(ui, self.docs.engine_mut(), …)`, and the whole
//! [`DockContext`](crate::panels::dock::DockContext)). A `BrepApp::engine_mut()`
//! would borrow ALL of `self` and every one of those sites would stop compiling.
//! `self.docs.engine_mut()` borrows only the `docs` FIELD, so it composes with a
//! borrow of any other field exactly as `self.state` used to.
//!
//! # One runner per document
//!
//! Each engine installs its own history runner (a native thread, or — on wasm —
//! its own web worker), because a runner owns the RESIDENT kernel state for the
//! document it executes: sharing one would make a background document's reply
//! land against the wrong resident registry. The shell therefore pumps EVERY
//! open document each frame, not just the active one, so a run that outlives a
//! tab switch is applied to the engine that submitted it. The cost is real and
//! deliberately unpaid-for here: N documents means N runner threads/workers and
//! N full scenes in memory. Opening a large assembly in a second tab costs what
//! opening it in a second window would.
//!
//! # Display settings are the SESSION's; the workbench is the DOCUMENT's
//!
//! Theme / UI scale / colors / wireframe / lod live on `EngineState.settings`,
//! so without a rule they would silently become per-tab (change the theme, switch
//! tabs, watch it flip back). [`carry_settings`] copies them from the outgoing
//! engine to the incoming one on every activation, and `workbench` is EXCLUDED
//! there: a saved document remembers the workbench it was authored in and
//! restores it on open, which is what makes the Assembly panes appear when you
//! switch to an assembly tab and vanish when you switch back to a part.
//!
//! A BRAND NEW tab is the one place the workbench IS carried — by
//! [`Documents::spawn_engine`], BEFORE the caller loads anything into the
//! engine, so a document that declares a workbench still overrides it during
//! the load and one that does not (a New document, a file saved before the
//! field existed) simply continues the session you were working in.

use crate::store::ModelStore;
use brep_render::engine_state::EngineState;

/// Builds a fresh engine for a new document — the platform runner, the viewcube,
/// and the persisted display settings, all applied before anything is loaded
/// into it. Injected by the shell so tests (which need the SYNCHRONOUS inline
/// runner) can construct documents without a background thread.
pub type EngineFactory = Box<dyn Fn() -> EngineState>;

/// The empty model a **New** document starts from.
pub const EMPTY_DOCUMENT: &str = r#"{"expressions":"","configurator":{},"features":[]}"#;

/// ONE open model: the engine that owns it plus the identity the file lane needs
/// — the store name it was opened from / saved to, and the clean baseline.
pub struct Document {
    /// The windowing-agnostic brain for THIS document (scene, camera, history,
    /// settings, selection). Panels borrow it; it is never forked.
    pub engine: EngineState,
    /// The store identity (`None` = a never-saved "untitled" model). The RAW
    /// identity, not the display name — a native dialog hands back a full path
    /// and a plain Save must write back to it.
    name: Option<String>,
    /// The model request JSON as of the last New / Open / Save — the baseline
    /// the dirty flag compares the live history against.
    saved_signature: Option<String>,
    /// The cached tab-strip dirty dot. See [`Document::dirty_marker`] for why
    /// this is not simply `is_dirty()`.
    dirty_marker: bool,
    /// The applied-run generation `dirty_marker` was computed at.
    marker_generation: Option<u64>,
    /// A process-unique handle, so the shell can notice "the active document is
    /// a different one now" without comparing indices (closing a tab BEFORE the
    /// active one moves the index without changing the document).
    id: u64,
}

impl Document {
    /// Wrap `engine` as a document, taking its CURRENT model as the clean
    /// baseline — so a freshly loaded (or freshly emptied) document is clean and
    /// the first edit marks it dirty.
    pub fn new(engine: EngineState) -> Self {
        let saved_signature = Some(engine.history_request_json());
        Self {
            engine,
            name: None,
            saved_signature,
            dirty_marker: false,
            marker_generation: None,
            id: next_document_id(),
        }
    }

    /// The raw store identity, or `None` for a never-saved document.
    pub fn name(&self) -> Option<&str> {
        self.name.as_deref()
    }

    pub fn set_name(&mut self, name: Option<String>) {
        self.name = name;
    }

    /// The tab label: the bare display name, or `untitled`.
    pub fn title(&self) -> String {
        match &self.name {
            Some(name) => crate::store::model_display_name(name),
            None => "untitled".to_string(),
        }
    }

    /// Snapshot the current model as the clean baseline (after New / Open /
    /// Save, or a `?loadModel=` boot-load).
    pub fn mark_clean(&mut self) {
        self.saved_signature = Some(self.engine.history_request_json());
        self.dirty_marker = false;
        self.marker_generation = Some(self.engine.applied_generation());
    }

    /// Dirty = the live model differs from the last saved/opened baseline.
    /// (Rolling the history does NOT change the request document, so navigating
    /// steps never marks dirty — only real edits/add/delete/reorder do.)
    ///
    /// HONEST but not free: it serializes the whole request document, which for
    /// an assembly carrying an embedded parts library is megabytes. Every place
    /// where being wrong would cost the user work — the close prompt, Save —
    /// calls THIS. The per-frame tab dot calls [`Self::dirty_marker`] instead.
    pub fn is_dirty(&self) -> bool {
        match &self.saved_signature {
            Some(saved) => *saved != self.engine.history_request_json(),
            None => true,
        }
    }

    /// The cached dirty flag the tab strip draws, recomputed only when the
    /// document's APPLIED RUN generation moved. Every ordinary edit (a param
    /// change, add, delete, reorder, undo) re-runs the history and bumps that
    /// generation, so the dot tracks editing; a mutation that changes the
    /// document WITHOUT a re-run (an object-metadata write) can leave the dot
    /// one edit behind. That is a marker being briefly optimistic, never a lost
    /// edit: [`Self::is_dirty`] is recomputed honestly at the close prompt.
    ///
    /// The alternative — serializing every open document every frame — is a
    /// per-frame multi-megabyte cost per tab, and the app pays no such cost today.
    pub fn refresh_dirty_marker(&mut self) {
        let generation = self.engine.applied_generation();
        if self.marker_generation == Some(generation) {
            return;
        }
        self.marker_generation = Some(generation);
        self.dirty_marker = self.is_dirty();
    }

    pub fn dirty_marker(&self) -> bool {
        self.dirty_marker
    }

    /// The document's process-unique handle (identity across index shuffles).
    pub fn id(&self) -> u64 {
        self.id
    }
}

/// Every open document + which one is active. Always holds AT LEAST ONE
/// document: closing the last tab leaves a fresh untitled one in its place, so
/// [`Documents::engine_mut`] is infallible and the shell never has to render a
/// "no document" state that would be an empty viewport with extra steps.
pub struct Documents {
    open: Vec<Document>,
    active: usize,
    /// How a new tab's engine is built (platform runner + persisted settings).
    new_engine: EngineFactory,
}

impl Documents {
    /// A session holding ONE empty document built by `new_engine`.
    pub fn new(new_engine: EngineFactory) -> Self {
        let first = Document::new(new_engine());
        Self {
            open: vec![first],
            active: 0,
            new_engine,
        }
    }

    /// A fresh engine for a document about to be opened — the caller loads into
    /// it and hands the result to [`Self::open_document`].
    ///
    /// Seeded with the WHOLE of the session's settings, workbench included, so
    /// a new tab continues what you were doing. The load that follows overrides
    /// the workbench if the document names one (see the module header).
    pub fn spawn_engine(&self) -> EngineState {
        let mut engine = (self.new_engine)();
        carry_settings(&self.engine().settings_json(), &mut engine, true);
        engine
    }

    pub fn engine(&self) -> &EngineState {
        &self.open[self.active].engine
    }

    pub fn engine_mut(&mut self) -> &mut EngineState {
        &mut self.open[self.active].engine
    }

    pub fn active(&self) -> &Document {
        &self.open[self.active]
    }

    pub fn active_mut(&mut self) -> &mut Document {
        &mut self.open[self.active]
    }

    pub fn active_index(&self) -> usize {
        self.active
    }

    /// The ACTIVE document's handle — the shell compares it frame to frame to
    /// notice a switch from ANY source (a tab click, a close, New, Open, Open
    /// Part, the session restore) with one check instead of a hook per site.
    pub fn active_id(&self) -> u64 {
        self.open[self.active].id
    }

    pub fn len(&self) -> usize {
        self.open.len()
    }

    pub fn get(&self, index: usize) -> Option<&Document> {
        self.open.get(index)
    }

    pub fn get_mut(&mut self, index: usize) -> Option<&mut Document> {
        self.open.get_mut(index)
    }

    pub fn iter(&self) -> std::slice::Iter<'_, Document> {
        self.open.iter()
    }

    pub fn iter_mut(&mut self) -> std::slice::IterMut<'_, Document> {
        self.open.iter_mut()
    }

    /// The tab holding the document stored under `name`, if any.
    pub fn index_of(&self, name: &str) -> Option<usize> {
        self.open
            .iter()
            .position(|doc| doc.name.as_deref() == Some(name))
    }

    /// Activate the tab already holding `name`; `false` when it is not open.
    /// The "focus the existing tab" half of open-or-focus.
    pub fn focus_named(&mut self, name: &str) -> bool {
        match self.index_of(name) {
            Some(index) => {
                self.activate(index);
                true
            }
            None => false,
        }
    }

    /// Add `doc` as a new tab and make it active.
    pub fn open_document(&mut self, doc: Document) -> usize {
        self.open.push(doc);
        let index = self.open.len() - 1;
        self.activate(index);
        index
    }

    /// Make tab `index` active, carrying the session's display settings over to
    /// it. Out-of-range indices are ignored (a stale click never panics).
    pub fn activate(&mut self, index: usize) {
        if index >= self.open.len() || index == self.active {
            return;
        }
        let settings = self.open[self.active].engine.settings_json();
        self.active = index;
        carry_settings(&settings, &mut self.open[index].engine, false);
    }

    /// Close tab `index`. Closing the LAST document leaves a fresh untitled one
    /// (the always-one-document invariant); closing a tab before the active one
    /// keeps the same document active at its new index.
    ///
    /// The caller is responsible for the unsaved-changes prompt — this is the
    /// mechanical close (`panels::file` owns the confirmation).
    pub fn close(&mut self, index: usize) {
        if index >= self.open.len() {
            return;
        }
        // Taken BEFORE the removal: if the closing tab was the active one, its
        // settings are the session's and must survive into whatever is shown next.
        let settings = self.open[self.active].engine.settings_json();
        let closed_active = index == self.active;
        self.open.remove(index);
        // The replacement for a session closed down to nothing is a brand-new
        // tab, so it takes the WHOLE of the session's settings — workbench
        // included — exactly as `New` does through `spawn_engine`.
        let refilled = self.open.is_empty();
        if refilled {
            self.open.push(Document::new((self.new_engine)()));
            self.active = 0;
        } else if closed_active {
            self.active = index.min(self.open.len() - 1);
        } else if index < self.active {
            self.active -= 1;
        }
        if closed_active {
            let active = self.active;
            carry_settings(&settings, &mut self.open[active].engine, refilled);
        }
    }

    /// Refresh every tab's dirty dot (see [`Document::refresh_dirty_marker`]).
    pub fn refresh_dirty_markers(&mut self) {
        for doc in &mut self.open {
            doc.refresh_dirty_marker();
        }
    }

    // --- session persistence --------------------------------------------------

    /// The persisted session: the NAMED documents in tab order plus the active
    /// one's name. A never-saved document has no store identity, so it cannot be
    /// restored and is not listed — reloading loses an unsaved scratch document
    /// exactly as it did when the app held one document and persisted none.
    pub fn session_json(&self) -> String {
        let open: Vec<&str> = self.open.iter().filter_map(Document::name).collect();
        serde_json::json!({
            "open": open,
            "active": self.active().name(),
        })
        .to_string()
    }

    /// Restore a persisted session, REPLACING the current open list. Names the
    /// store no longer holds (or cannot load) are skipped — a deleted file must
    /// not stop the rest of the session coming back — and the count of documents
    /// actually restored is returned, so the caller can seed instead when it is 0.
    pub fn restore_session(&mut self, store: &dyn ModelStore, json: &str) -> usize {
        let Ok(session) = serde_json::from_str::<serde_json::Value>(json) else {
            return 0;
        };
        let names: Vec<String> = session["open"]
            .as_array()
            .map(|list| {
                list.iter()
                    .filter_map(|name| name.as_str().map(str::to_string))
                    .collect()
            })
            .unwrap_or_default();
        let wanted_active = session["active"].as_str().unwrap_or_default().to_string();

        let mut restored: Vec<Document> = Vec::new();
        let mut active = 0usize;
        for name in names {
            let Some(contents) = store.read(&name) else {
                continue;
            };
            let mut engine = (self.new_engine)();
            if engine.load_model_and_fit(&contents).is_err() {
                continue;
            }
            let mut doc = Document::new(engine);
            doc.set_name(Some(name.clone()));
            if name == wanted_active {
                active = restored.len();
            }
            restored.push(doc);
        }
        if restored.is_empty() {
            return 0;
        }
        self.open = restored;
        self.active = active;
        self.open.len()
    }
}

/// Copy the SESSION-scoped display settings (theme, UI scale, colors, wireframe,
/// projection, lod…) from a `settings_json()` snapshot into `target`.
/// `with_workbench` is true ONLY when seeding a brand-new engine — see the
/// module header for why activation must never carry it.
fn carry_settings(settings_json: &str, target: &mut EngineState, with_workbench: bool) {
    let Ok(mut settings) = serde_json::from_str::<serde_json::Value>(settings_json) else {
        return;
    };
    if !with_workbench {
        if let Some(object) = settings.as_object_mut() {
            object.remove("workbench");
        }
    }
    let _ = target.apply_settings_json(&settings.to_string());
}

/// Hand out the next document handle. A plain process counter: handles only ever
/// need to be distinct WITHIN a session, and they never reach storage.
fn next_document_id() -> u64 {
    use std::sync::atomic::{AtomicU64, Ordering};
    static NEXT: AtomicU64 = AtomicU64::new(1);
    NEXT.fetch_add(1, Ordering::Relaxed)
}

#[cfg(all(test, not(target_arch = "wasm32")))]
mod tests {
    use super::*;
    use crate::store::MemModelStore;

    /// The test factory: the SYNCHRONOUS inline runner, so a load's solids are
    /// resident by the time the call returns.
    fn documents() -> Documents {
        Documents::new(Box::new(EngineState::new))
    }

    const BOX_SEED: &str = r#"{"expressions":"","configurator":{},"features":[
        {"type":"P.CU","inputParams":{"id":"Box","sizeX":8.0,"sizeY":8.0,"sizeZ":8.0,
         "transform":{"position":[0,0,0],"rotationEuler":[0,0,0],"scale":[1,1,1]},
         "boolean":{"targets":[],"operation":"NONE"}},"persistentData":{}}
    ]}"#;

    fn named(docs: &mut Documents, name: &str) -> usize {
        let mut engine = docs.spawn_engine();
        engine.set_history_json(BOX_SEED).unwrap();
        let mut doc = Document::new(engine);
        doc.set_name(Some(name.to_string()));
        docs.open_document(doc)
    }

    /// A session starts with exactly one (empty, untitled, clean) document, and
    /// every opened document becomes the active tab.
    #[test]
    fn a_session_always_holds_at_least_one_document() {
        let mut docs = documents();
        assert_eq!(docs.len(), 1);
        assert_eq!(docs.active_index(), 0);
        assert_eq!(docs.active().title(), "untitled");
        assert!(!docs.active().is_dirty(), "a fresh document is clean");

        named(&mut docs, "part-a");
        assert_eq!(docs.len(), 2);
        assert_eq!(docs.active_index(), 1, "an opened document takes focus");
        assert_eq!(docs.active().title(), "part-a");
    }

    /// Open-or-focus: a name already open activates ITS tab instead of adding a
    /// second one.
    #[test]
    fn focus_named_activates_the_existing_tab() {
        let mut docs = documents();
        named(&mut docs, "part-a");
        named(&mut docs, "part-b");
        assert_eq!(docs.active_index(), 2);

        assert!(docs.focus_named("part-a"), "already open");
        assert_eq!(docs.active_index(), 1);
        assert_eq!(docs.len(), 3, "focusing never adds a tab");
        assert!(!docs.focus_named("part-z"), "never opened");
        assert_eq!(docs.active_index(), 1, "a miss leaves the focus alone");
    }

    /// The index fixup: closing a tab BEFORE the active one keeps the same
    /// document active (its handle is unchanged); closing the active one falls
    /// to its neighbour; closing the last one leaves a fresh untitled document.
    #[test]
    fn closing_fixes_up_the_active_index() {
        let mut docs = documents();
        named(&mut docs, "part-a"); // index 1
        named(&mut docs, "part-b"); // index 2
        docs.activate(2);
        let active_id = docs.active_id();

        // Close the untitled tab BEFORE the active one: same document, new index.
        docs.close(0);
        assert_eq!(docs.len(), 2);
        assert_eq!(docs.active_index(), 1);
        assert_eq!(docs.active_id(), active_id, "the same document stays active");
        assert_eq!(docs.active().title(), "part-b");

        // Close the ACTIVE (last) tab: focus falls back to its neighbour.
        docs.close(1);
        assert_eq!(docs.len(), 1);
        assert_eq!(docs.active_index(), 0);
        assert_eq!(docs.active().title(), "part-a");
        assert_ne!(docs.active_id(), active_id, "a different document is active");

        // Close the ONLY tab: a fresh untitled document takes its place.
        docs.close(0);
        assert_eq!(docs.len(), 1, "there is always a document");
        assert_eq!(docs.active().title(), "untitled");
        assert_eq!(docs.active().engine.history_len(), 0);

        // Out-of-range indices are ignored rather than panicking.
        docs.close(7);
        assert_eq!(docs.len(), 1);
    }

    /// Dirty tracking is per document: editing one tab never marks another, and
    /// the cached tab-strip marker follows the honest flag across a re-run.
    #[test]
    fn dirty_tracking_is_per_document() {
        let mut docs = documents();
        named(&mut docs, "part-a");
        named(&mut docs, "part-b");
        docs.refresh_dirty_markers();
        assert!(docs.iter().all(|doc| !doc.is_dirty()), "all clean");
        assert!(docs.iter().all(|doc| !doc.dirty_marker()));

        // Edit the ACTIVE document (part-b).
        docs.engine_mut()
            .update_feature_params(
                "Box",
                r#"{"id":"Box","sizeX":19.0,"sizeY":8.0,"sizeZ":8.0,"transform":{"position":[0,0,0],"rotationEuler":[0,0,0],"scale":[1,1,1]},"boolean":{"targets":[],"operation":"NONE"}}"#,
            )
            .unwrap();
        docs.refresh_dirty_markers();
        assert!(docs.active().is_dirty(), "the edited document is dirty");
        assert!(docs.active().dirty_marker(), "…and its tab dot lights");
        assert!(!docs.get(1).unwrap().is_dirty(), "the other tab is untouched");
        assert!(!docs.get(1).unwrap().dirty_marker());

        // Saving (marking clean) clears both the flag and the dot.
        docs.active_mut().mark_clean();
        docs.refresh_dirty_markers();
        assert!(!docs.active().is_dirty());
        assert!(!docs.active().dirty_marker());
    }

    /// Display settings are the SESSION's: a theme change follows a tab switch.
    /// The workbench is the DOCUMENT's and must NOT follow it — that is what
    /// makes the Assembly panes appear on an assembly tab and vanish on a part.
    #[test]
    fn switching_carries_display_settings_but_not_the_workbench() {
        let mut docs = documents();
        docs.engine_mut()
            .apply_settings_json(r#"{"workbench":"assembly","wireframe":true}"#)
            .unwrap();
        named(&mut docs, "part-a");
        docs.engine_mut()
            .apply_settings_json(r#"{"workbench":"sheetMetal"}"#)
            .unwrap();
        assert!(
            docs.engine().settings.wireframe,
            "the new tab inherited the session's display settings"
        );

        // Back to the first tab: it keeps its own workbench, and picks up the
        // display setting changed while it was in the background.
        docs.engine_mut()
            .apply_settings_json(r#"{"wireframe":false}"#)
            .unwrap();
        docs.activate(0);
        assert_eq!(docs.engine().settings.workbench, "assembly", "per document");
        assert!(!docs.engine().settings.wireframe, "per session");

        docs.activate(1);
        assert_eq!(docs.engine().settings.workbench, "sheetMetal");
    }

    /// The session round-trips through the store: only NAMED documents are
    /// listed, the active one comes back active, and a name whose file has gone
    /// is skipped rather than failing the whole restore.
    #[test]
    fn the_session_round_trips_and_tolerates_a_missing_file() {
        let store = MemModelStore::new();
        store.put("part-a", BOX_SEED);
        store.put("part-b", BOX_SEED);

        let mut docs = documents();
        named(&mut docs, "part-a");
        named(&mut docs, "part-b");
        docs.activate(1);
        let session = docs.session_json();
        let parsed: serde_json::Value = serde_json::from_str(&session).unwrap();
        assert_eq!(
            parsed["open"].as_array().unwrap().len(),
            2,
            "the untitled tab is not persistable: {session}"
        );
        assert_eq!(parsed["active"], "part-a");

        let mut restored = documents();
        assert_eq!(restored.restore_session(&store, &session), 2);
        assert_eq!(restored.len(), 2);
        assert_eq!(restored.active().title(), "part-a");
        assert!(!restored.active().is_dirty(), "a restored document is clean");
        assert_eq!(restored.active().engine.scene.solids().len(), 1);

        // One file removed: the rest of the session still comes back.
        store.remove("part-a").unwrap();
        let mut partial = documents();
        assert_eq!(partial.restore_session(&store, &session), 1);
        assert_eq!(partial.active().title(), "part-b");

        // Nothing restorable → 0, and the caller seeds instead.
        store.remove("part-b").unwrap();
        let mut none = documents();
        assert_eq!(none.restore_session(&store, &session), 0);
        assert_eq!(none.len(), 1, "the untouched boot document survives");
        assert_eq!(none.restore_session(&store, "not json"), 0);
    }
}