//! Explicit, semantics-preserving arrangement of one or more Allocation cards.
//!
//! The App must admit the entire original typed selection before converting it
//! to placement/element identities. These values do not grant input authority.
use super::*;

#[derive(Debug)]
pub struct Plan {
    accepted: Project,
    diagram: Id,
    selected: BTreeMap<Id, Id>,
    anchor: Id,
    placements: BTreeMap<Id, NodePlacement>,
    expanded_ids: BTreeSet<Id>,
    index: ViewIndex,
    before_visible: ProjectedView,
    before_expanded: ProjectedView,
}

impl Plan {
    pub fn project(&self) -> &Project {
        &self.accepted
    }

    pub fn index(&self) -> &ViewIndex {
        &self.index
    }

    pub fn affected(&self) -> &BTreeMap<Id, NodePlacement> {
        &self.placements
    }

    pub fn selected(&self) -> &BTreeMap<Id, Id> {
        &self.selected
    }

    pub fn anchor(&self) -> Id {
        self.anchor
    }

    pub fn diagram(&self) -> &Diagram {
        &self.accepted.diagrams[&self.diagram]
    }
}

/// Capture every original placement identity before normalizing semantic roots.
/// Document/revision/selection-generation and clean-owner guards belong to App.
pub fn capture(
    p: &Project,
    diagram: Id,
    selected: &BTreeMap<Id, Id>,
    anchor: Id,
) -> Result<Plan, Refusal> {
    validate_candidate(p).map_err(|e| Refusal::InvalidCandidate(e.to_string()))?;
    let d = p.diagrams.get(&diagram).ok_or(Refusal::StaleScope)?;
    if d.projection != ProjectionKind::Allocation
        || selected.is_empty()
        || !selected.contains_key(&anchor)
    {
        return Err(Refusal::Ineligible(
            "Arrange requires selected placements and a selected anchor in an Allocation view."
                .into(),
        ));
    }
    let index = ViewIndex::new(p);
    let before_visible = projection::project_diagram_with_index(p, d, &index);
    let visible: BTreeMap<_, _> = before_visible
        .nodes
        .iter()
        .map(|n| (n.id, n.element))
        .collect();
    let mut work = BTreeMap::new();
    let mut performers = Vec::new();
    for (placement, element) in selected {
        let node = d.nodes.get(placement).ok_or(Refusal::StaleScope)?;
        let record = p.elements.get(element).ok_or(Refusal::StaleScope)?;
        if node.element != *element || visible.get(placement) != Some(element) {
            return Err(Refusal::StaleScope);
        }
        if record.layer() != d.layer || !(record.kind().is_work() || record.kind().is_performer()) {
            return Err(Refusal::Ineligible(
                "Arrange requires only activities, functions or performers in this layer.".into(),
            ));
        }
        if record.kind().is_work() {
            work.insert(*element, *placement);
        } else {
            performers.push(*placement);
        }
    }

    let mut placements = BTreeMap::new();
    for (element, placement) in &work {
        let root = &p.elements[element];
        let mut ancestor = root.parent;
        let mut covered = false;
        let mut seen = BTreeSet::new();
        while let Some(id) = ancestor {
            if !seen.insert(id) {
                return Err(Refusal::StaleScope);
            }
            let parent = p.elements.get(&id).ok_or(Refusal::StaleScope)?;
            if parent.kind() != root.kind() {
                break;
            }
            if work.contains_key(&id) {
                covered = true;
                break;
            }
            ancestor = parent.parent;
        }
        if !covered {
            placements.extend(capture_validated(p, diagram, *element, *placement)?.placements);
        }
    }
    for performer in performers {
        for id in
            std::iter::once(performer).chain(projection::descendant_nodes(p, diagram, performer))
        {
            placements.insert(id, d.nodes.get(&id).ok_or(Refusal::StaleScope)?.clone());
        }
    }

    // Arrange preserves ancestry, so accepted diagnostic identities also apply
    // to every translated candidate.
    let expanded_ids = geometry::expansion_ids(p, d, &index, &placements)?;
    let before_expanded = geometry::expanded_view(p, d, &index, &expanded_ids);
    Ok(Plan {
        accepted: p.clone(),
        diagram,
        selected: selected.clone(),
        anchor,
        placements,
        expanded_ids,
        index,
        before_visible,
        before_expanded,
    })
}

/// Snap the captured anchor once; preview the complete union without cloning or
/// validating a Project, rebuilding its semantic index, or expanding scope.
pub fn place(
    plan: &Plan,
    requested: Position,
    presentation: PresentationContext,
) -> Result<PlacementPlan, Refusal> {
    if presentation.target.is_some() {
        return Err(Refusal::Ineligible(
            "Arrange only has no performer destination.".into(),
        ));
    }
    if !requested.x.is_finite()
        || !requested.y.is_finite()
        || !presentation.viewport.valid()
        || !presentation.zoom.is_finite()
        || presentation.zoom <= 0.
    {
        return Err(Refusal::LayoutRequired(
            "Make room or adjust the view, then drag again.".into(),
        ));
    }
    let geometry::Translation {
        diagram,
        commands,
        delta,
    } = geometry::translate(
        &plan.accepted,
        plan.diagram(),
        plan.diagram(),
        &plan.placements,
        plan.anchor,
        requested,
    )?;
    let view = projection::project_diagram_with_index(&plan.accepted, &diagram, &plan.index);
    let expanded =
        geometry::expanded_view(&plan.accepted, &diagram, &plan.index, &plan.expanded_ids);
    // Preserve Arrange's refusal precedence: projected bounds, then rigidity,
    // then overlap growth. The shared scene check combines bounds and overlaps.
    let scenes = match geometry::check_scenes(
        &plan.before_visible,
        &plan.before_expanded,
        &view,
        &expanded,
    ) {
        Err(error @ Refusal::InvalidCandidate(_)) => return Err(error),
        result => result,
    };
    geometry::check_rigid(&plan.before_expanded, &expanded, &plan.placements, delta)?;
    scenes?;
    geometry::check_headers(&view, &plan.selected, presentation.viewport)?;
    Ok(PlacementPlan {
        diagram,
        view,
        delta,
        unfolded: None,
        requested,
        presentation,
        commands,
    })
}

/// Recompute the candidate and compare the complete expected Project before the
/// caller performs one source-admitted transaction. None means no history entry.
pub fn finish(
    plan: &Plan,
    live: &Project,
    placement: &PlacementPlan,
) -> Result<Option<Command>, Refusal> {
    if live != &plan.accepted {
        return Err(Refusal::StaleScope);
    }
    let checked = place(plan, placement.requested, placement.presentation)?;
    if checked.diagram != placement.diagram
        || checked.view != placement.view
        || checked.delta != placement.delta
        || checked.unfolded != placement.unfolded
        || checked.commands != placement.commands
    {
        return Err(Refusal::StaleScope);
    }
    let mut expected = plan.accepted.clone();
    expected
        .diagrams
        .insert(checked.diagram.id, checked.diagram);
    let command = Command::Batch(checked.commands);
    let actual = prepare_command(live, &command)
        .map_err(|e| Refusal::InvalidCandidate(e.to_string()))?
        .project;
    exact_project(&expected, &actual)?;
    Ok((actual != *live).then_some(command))
}