//! Navigation is derived from the same opaque-reference scene that is painted.
use super::*;
use crate::diagram_usage::{Surface, Target, Usage};

/// The renderer collapses whitespace before shortening. Require at least one
/// actual character of this field, rather than an ellipsis at its start.
fn label_field_visible(full: &str, prefix: &str, value: &str) -> bool {
    if value.trim().is_empty() {
        return false;
    }
    let normalized = full.split_whitespace().collect::<Vec<_>>().join(" ");
    let normalized_prefix = prefix.split_whitespace().collect::<Vec<_>>().join(" ");
    let start = normalized_prefix.len()
        + usize::from(prefix.ends_with(char::is_whitespace) && !normalized_prefix.is_empty());
    let painted = crate::views::short(full, 32);
    let retained = normalized
        .chars()
        .zip(painted.chars())
        .take_while(|(a, b)| a == b)
        .map(|(c, _)| c.len_utf8())
        .sum::<usize>();
    start < retained
}

fn usages(p: &Project, owner: Id, subject: Id, scene: &Scene) -> Vec<Usage> {
    let mut result = Vec::new();
    let mut add = |id, bounds, role: &str| {
        // Activation bars share the occurrence identity with a labelled message;
        // they must not inflate its target count.
        if !result
            .iter()
            .any(|u: &Usage| u.target == Target::ScenarioObject(id))
        {
            result.push(Usage {
                subject,
                surface: Surface::Scenario(owner),
                target: Target::ScenarioObject(id),
                role: role.into(),
                bounds,
            });
        }
    };
    for item in scene.boxes.iter().filter(|item| !item.title.is_empty()) {
        let Some(element) = p.elements.get(&item.id) else {
            continue;
        };
        if subject == item.id {
            // A fragment's selectable header is useful even when its frame is
            // much larger than the viewport.
            let mut bounds = item.rect;
            if item.marker == Some(Kind::Occurrence) {
                bounds.height = bounds.height.min(38.);
            }
            add(item.id, bounds, "scenario object");
        }
        let represented = match element.shared() {
            Some(SharedBody::Lifeline { represented }) => represented.map(|id| (id, "lifeline")),
            Some(SharedBody::Occurrence { body, .. }) => match body {
                OccurrenceBody::Action { action, .. } => action.map(|id| (id, "action occurrence")),
                OccurrenceBody::State { state, .. } => state.map(|id| (id, "state observation")),
                OccurrenceBody::SequenceReference { sequence } => {
                    sequence.map(|id| (id, "process reference"))
                }
                OccurrenceBody::ScenarioUse { scenario, .. } => {
                    scenario.map(|id| (id, "scenario reference"))
                }
                // An incomplete message fallback box only paints the occurrence
                // name and a repair hint, not its exchange or operation.
                _ => None,
            },
            _ => None,
        };
        if let Some((id, role)) = represented.filter(|(id, _)| *id == subject) {
            let _ = id;
            add(item.id, item.rect, role);
        }
    }
    for line in scene.lines.iter().filter(|line| !line.label.is_empty()) {
        let Some(element) = p.elements.get(&line.id) else {
            continue;
        };
        let Some(SharedBody::Occurrence {
            body: OccurrenceBody::Exchange { exchange, .. },
            ..
        }) = element.shared()
        else {
            continue;
        };
        let bounds = line.label_bounds();
        if subject == line.id || *exchange == Some(subject) {
            add(line.id, bounds, "message occurrence");
        }
        // Replies derive their operation from the exact call, matching the
        // operation label formatter rather than scanning raw reference fields.
        if let Ok(operations::OperationResolution::Selected(operation)) =
            operations::resolve(p, line.id)
            && let Some(label) = crate::data_values::operation_label(p, element)
            && let Some(prefix) = line.label.strip_suffix(&label)
        {
            let allocation = &p.relations[&operation.allocation];
            let operation_prefix = if matches!(
                element.shared(),
                Some(SharedBody::Occurrence {
                    body: OccurrenceBody::Exchange {
                        message_kind: MessageKind::Reply,
                        ..
                    },
                    ..
                })
            ) {
                "Reply operation from Call: "
            } else {
                "Operation: "
            };
            let fields = [
                (allocation.source(), format!("{prefix}{operation_prefix}")),
                (
                    allocation.target(),
                    format!(
                        "{prefix}{operation_prefix}{} / ",
                        p.named(allocation.source())
                    ),
                ),
                (
                    allocation.id,
                    format!(
                        "{prefix}{operation_prefix}{} / {} · ",
                        p.named(allocation.source()),
                        p.named(allocation.target())
                    ),
                ),
            ];
            for (id, prefix) in fields {
                if id == subject && label_field_visible(&line.label, &prefix, p.named(id)) {
                    add(line.id, bounds, "operation label");
                }
            }
        }
    }
    if subject == owner {
        result.insert(
            0,
            Usage {
                subject,
                surface: Surface::Scenario(owner),
                target: Target::Whole,
                role: "scenario".into(),
                bounds: Rectangle::new(Point::ORIGIN, scene.size),
            },
        );
    }
    result
}

impl State {
    pub(crate) fn diagram_usages(&self, p: &Project, owner: Id, subject: Id) -> Vec<Usage> {
        if !p
            .elements
            .get(&owner)
            .is_some_and(|e| e.kind() == Kind::Scenario)
        {
            return vec![];
        }
        usages(p, owner, subject, &Scene::sequence(p, owner, subject))
    }

    pub(crate) fn reveal_usage(
        &mut self,
        p: &Project,
        document: Id,
        owner: Id,
        target: &Target,
    ) -> bool {
        if self.draft.is_some()
            || !p
                .elements
                .get(&owner)
                .is_some_and(|e| e.kind() == Kind::Scenario)
        {
            return false;
        }
        let id = match target {
            Target::Whole => owner,
            Target::ScenarioObject(id) => *id,
            _ => return false,
        };
        let Some(usage) = self
            .diagram_usages(p, owner, id)
            .into_iter()
            .find(|u| &u.target == target)
        else {
            return false;
        };
        // Preserve an existing mounted viewport across enter's owner reset.
        let viewport = self.presentation.viewport.unwrap_or(Size::new(500., 300.));
        self.enter(document, owner);
        self.presentation.viewport = Some(viewport);
        self.canvas_tool = Some((owner, CanvasTool::Select));
        let (zoom, pan) = crate::diagram_usage::camera_for(target, usage.bounds, viewport);
        self.presentation.zoom(Some(zoom));
        self.presentation.pan = pan;
        true
    }
}

#[cfg(test)]
mod tests;