gpui-rhai 0.1.4

use std::collections::{BTreeMap, BTreeSet};

use rhai::{CustomType, ImmutableString, TypeBuilder};
use thiserror::Error;

use crate::{ComponentInstancePath, NodeId};

#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ElementRefId {
    component: ComponentInstancePath,
    key: String,
}

impl ElementRefId {
    /// Construct a stable component-local reference identity.
    ///
    /// # Errors
    ///
    /// Returns [`ElementRefError::InvalidKey`] for unsafe keys.
    pub fn new(
        component: ComponentInstancePath,
        key: impl Into<String>,
    ) -> Result<Self, ElementRefError> {
        let key = key.into();
        if key.is_empty()
            || key.len() > 128
            || !key.chars().all(|character| {
                character.is_ascii_alphanumeric() || matches!(character, '_' | '-' | '.' | ':')
            })
        {
            return Err(ElementRefError::InvalidKey(key));
        }
        Ok(Self { component, key })
    }

    #[must_use]
    pub const fn component(&self) -> &ComponentInstancePath {
        &self.component
    }

    #[must_use]
    pub fn key(&self) -> &str {
        &self.key
    }
}

/// Non-owning reference to a retained node in one formal component scope.
#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ElementRef {
    id: ElementRefId,
}

impl ElementRef {
    #[must_use]
    pub const fn new(id: ElementRefId) -> Self {
        Self { id }
    }

    #[must_use]
    pub const fn id(&self) -> &ElementRefId {
        &self.id
    }
}

impl CustomType for ElementRef {
    fn build(mut builder: TypeBuilder<Self>) {
        builder
            .with_name("ElementRef")
            .with_get("key", |reference: &mut Self| {
                ImmutableString::from(reference.id.key.as_str())
            });
    }
}

#[derive(Clone, Debug, Default)]
pub struct ElementRefRegistry {
    active: BTreeMap<ElementRefId, NodeId>,
    pending_geometry_readers: BTreeMap<ElementRefId, BTreeSet<ComponentInstancePath>>,
}

impl ElementRefRegistry {
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    #[must_use]
    pub fn len(&self) -> usize {
        self.active.len()
    }

    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.active.is_empty()
    }

    pub fn iter(&self) -> impl ExactSizeIterator<Item = (&ElementRefId, &NodeId)> {
        self.active.iter()
    }

    /// Resolve the last committed retained identity.
    ///
    /// # Errors
    ///
    /// Returns [`ElementRefError::Stale`] after unmount or before commit.
    pub fn resolve(&self, reference: &ElementRef) -> Result<NodeId, ElementRefError> {
        self.active
            .get(reference.id())
            .copied()
            .ok_or_else(|| ElementRefError::Stale(reference.id().clone()))
    }

    /// Resolve a mounted component-local ref key.
    ///
    /// # Errors
    ///
    /// Returns [`ElementRefError::UnknownKey`] when no binding is committed.
    pub fn resolve_key(
        &self,
        component: &ComponentInstancePath,
        key: &str,
    ) -> Result<ElementRef, ElementRefError> {
        self.active
            .keys()
            .find(|id| id.component() == component && id.key() == key)
            .cloned()
            .map(ElementRef::new)
            .ok_or_else(|| ElementRefError::UnknownKey {
                component: component.clone(),
                key: key.to_owned(),
            })
    }

    pub(crate) fn resolve_and_track_geometry(
        &mut self,
        reference: &ElementRef,
        reader: &ComponentInstancePath,
    ) -> Option<NodeId> {
        self.pending_geometry_readers
            .entry(reference.id().clone())
            .or_default()
            .insert(reader.clone());
        self.active.get(reference.id()).copied()
    }

    pub(crate) fn reconcile(
        &mut self,
        root: &ComponentInstancePath,
        candidate: BTreeMap<ElementRefId, NodeId>,
    ) -> BTreeMap<NodeId, BTreeSet<ComponentInstancePath>> {
        self.active.retain(|id, _| !id.component.is_within(root));
        self.active.extend(candidate);
        let pending = self
            .pending_geometry_readers
            .keys()
            .filter(|id| id.component.is_within(root))
            .cloned()
            .collect::<Vec<_>>();
        let mut resolved = BTreeMap::<NodeId, BTreeSet<ComponentInstancePath>>::new();
        for id in pending {
            let readers = self
                .pending_geometry_readers
                .remove(&id)
                .unwrap_or_default();
            if let Some(node) = self.active.get(&id) {
                resolved.entry(*node).or_default().extend(readers);
            }
        }
        resolved
    }

    pub(crate) fn remove_scope(&mut self, root: &ComponentInstancePath) {
        self.active.retain(|id, _| !id.component.is_within(root));
        self.pending_geometry_readers.retain(|id, readers| {
            if id.component.is_within(root) {
                return false;
            }
            readers.retain(|reader| !reader.is_within(root));
            !readers.is_empty()
        });
    }
}

#[derive(Clone, Debug, Error, Eq, PartialEq)]
pub enum ElementRefError {
    #[error("element-ref key `{0}` must be 1-128 ASCII letters, digits, `_`, `-`, `.`, or `:`")]
    InvalidKey(String),
    #[error("element ref `{0:?}` is stale or unmounted")]
    Stale(ElementRefId),
    #[error("element ref `{0:?}` was not declared by the active formal component render")]
    Undeclared(ElementRefId),
    #[error("element ref `{0:?}` is bound to more than one node")]
    DuplicateBinding(ElementRefId),
    #[error("element ref `{0:?}` requires a stable node key")]
    MissingNodeKey(ElementRefId),
    #[error("component `{component}` has no mounted element ref `{key}`")]
    UnknownKey {
        component: ComponentInstancePath,
        key: String,
    },
}

#[derive(Clone, Debug, PartialEq)]
pub(crate) enum ElementCommand {
    Focus {
        window: String,
        node: NodeId,
    },
    ScrollTo {
        window: String,
        node: NodeId,
        x: f64,
        y: f64,
    },
    ScrollIntoView {
        window: String,
        node: NodeId,
    },
}

impl ElementCommand {
    pub(crate) fn window(&self) -> &str {
        match self {
            Self::Focus { window, .. }
            | Self::ScrollTo { window, .. }
            | Self::ScrollIntoView { window, .. } => window,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn stale_refs_do_not_rebind_after_scope_removal() {
        let component = ComponentInstancePath::root("Panel", "main");
        let reference = ElementRef::new(ElementRefId::new(component.clone(), "field").unwrap());
        let mut tree = crate::RetainedUiTree::new();
        tree.reconcile(crate::UiNode::text("field")).unwrap();
        let mut registry = ElementRefRegistry::new();
        registry.reconcile(
            &component,
            BTreeMap::from([(reference.id().clone(), tree.root_id().unwrap())]),
        );
        assert!(registry.resolve(&reference).is_ok());
        registry.remove_scope(&component);
        assert!(matches!(
            registry.resolve(&reference),
            Err(ElementRefError::Stale(_))
        ));
    }

    #[test]
    fn pending_geometry_reader_binds_after_the_ref_commits() {
        let component = ComponentInstancePath::root("Panel", "main");
        let reader = component.child("Inspector", "reader");
        let reference = ElementRef::new(ElementRefId::new(component.clone(), "field").unwrap());
        let mut tree = crate::RetainedUiTree::new();
        tree.reconcile(crate::UiNode::text("field")).unwrap();
        let node = tree.root_id().unwrap();
        let mut refs = ElementRefRegistry::new();
        assert_eq!(refs.resolve_and_track_geometry(&reference, &reader), None);

        let resolved = refs.reconcile(&component, BTreeMap::from([(reference.id().clone(), node)]));
        let geometry = crate::GeometryRegistry::new();
        for (node, readers) in resolved {
            geometry.register_readers(node, readers);
        }
        geometry.update(
            node,
            crate::ElementGeometry {
                layout: crate::GeometryBounds::new(0.0, 0.0, 120.0, 24.0).unwrap(),
                visual: crate::GeometryBounds::new(0.0, 0.0, 120.0, 24.0).unwrap(),
                clip: None,
            },
        );
        assert_eq!(geometry.take_dirty(), BTreeSet::from([reader.clone()]));

        assert_eq!(
            refs.resolve_and_track_geometry(&reference, &reader),
            Some(node)
        );
        tree.reconcile(crate::UiNode::box_node(Vec::new())).unwrap();
        let replacement = tree.root_id().unwrap();
        assert_ne!(replacement, node);
        let resolved = refs.reconcile(
            &component,
            BTreeMap::from([(reference.id().clone(), replacement)]),
        );
        for (node, readers) in resolved {
            geometry.register_readers(node, readers);
        }
        geometry.retain_nodes(&BTreeSet::from([replacement]));
        geometry.update(
            replacement,
            crate::ElementGeometry {
                layout: crate::GeometryBounds::new(0.0, 0.0, 160.0, 24.0).unwrap(),
                visual: crate::GeometryBounds::new(0.0, 0.0, 160.0, 24.0).unwrap(),
                clip: None,
            },
        );
        assert_eq!(geometry.take_dirty(), BTreeSet::from([reader]));
    }
}