use super::*;

fn port_id(choice: &CommunicationPortChoice) -> Id {
    match choice {
        CommunicationPortChoice::Reuse { port } => *port,
        CommunicationPortChoice::Create { id, .. } => *id,
    }
}

pub(super) fn prepare_ports(
    original: &Project,
    working: &mut Project,
    targets: &BTreeMap<Id, Id>,
    plan: &mut TransitionPlan,
) -> BTreeMap<Id, (Id, Id)> {
    let mut pairs = BTreeMap::new();
    for decision in plan.request.communication_endpoints.clone() {
        let result = (|| -> Result<(Id, Id), String> {
            if plan.request.direction != TransitionDirection::OaToSa {
                return Err(
                    "SA endpoint choices apply only to OA→SA communication transition.".into(),
                );
            }
            let means = original
                .relations
                .get(&decision.source)
                .filter(|r| r.kind() == RelationKind::CommunicationMean)
                .ok_or("Endpoint decision must select an OA communication means.")?;
            if !plan.request.sources.contains(&means.id) && !targets.contains_key(&means.id) {
                return Err("Endpoint decision is outside this transition selection.".into());
            }
            if pairs.contains_key(&decision.source) {
                return Err("Choose one component-port pair per communication means.".into());
            }
            let mut pending = vec![];
            for (participant, choice) in [
                (means.source(), &decision.source_port),
                (means.target(), &decision.target_port),
            ] {
                let owner = targets.get(&participant).copied().ok_or("Review each OA participant's SA counterpart before selecting its component port.")?;
                if working.elements.get(&owner).is_some_and(|e| {
                    e.layer() != Layer::Sa || !matches!(e.kind(), Kind::System | Kind::SystemActor)
                }) {
                    return Err(
                        "Component-port owner must be the reviewed SA participant counterpart."
                            .into(),
                    );
                }
                match choice {
                    CommunicationPortChoice::Reuse { port } => {
                        let e = working
                            .elements
                            .get(port)
                            .ok_or("Selected component port does not exist.")?;
                        if e.parent != Some(owner)
                            || e.layer() != Layer::Sa
                            || !matches!(
                                crate::ports::port_contract(e),
                                Some(PortContract::Component { .. })
                            )
                        {
                            return Err("Selected component port must belong to the reviewed SA participant and have an explicit component contract.".into());
                        }
                    }
                    CommunicationPortChoice::Create {
                        id,
                        alias,
                        name,
                        description,
                        kind,
                        orientation,
                    } => {
                        if id.is_nil()
                            || working.contains(*id)
                            || pending.iter().any(|e: &Element| e.id == *id)
                        {
                            return Err("New component-port identity must be unused; choose Reuse for an existing port.".into());
                        }
                        pending.push(Element {
                            id: *id,
                            alias: alias.clone(),
                            name: name.clone(),
                            description: description.clone(),
                            parent: Some(owner),
                            body: ElementBody::shared_in(
                                Layer::Sa,
                                SharedBody::Port {
                                    contract: PortContract::Component {
                                        kind: *kind,
                                        orientation: *orientation,
                                    },
                                    legacy: None,
                                },
                            ),
                        });
                    }
                }
            }
            let pair = (
                port_id(&decision.source_port),
                port_id(&decision.target_port),
            );
            if pair.0 == pair.1 || targets.get(&means.source()) == targets.get(&means.target()) {
                return Err("Communication counterparts must have different participant owners; review the participant boundary mapping.".into());
            }
            for e in pending {
                working.elements.insert(e.id, e.clone());
                plan.commands.push(Command::CreateElement(e));
            }
            Ok(pair)
        })();
        match result {
            Ok(pair) => {
                pairs.insert(decision.source, pair);
            }
            Err(message) => conflict(
                plan,
                Some(decision.source),
                targets.get(&decision.source).copied(),
                None,
                message,
            ),
        }
    }
    pairs
}

/// Adapt only the transferred endpoint value. Reviewed baseline facts continue
/// to retain the actual participant/port identities on their respective sides.
pub(crate) fn review_endpoint_fact(
    project: &Project,
    request: &TransitionRequest,
    map: &BTreeMap<Id, Id>,
    source: Id,
    target: Id,
    fact: &FacetReview,
) -> Result<Option<FacetReview>, String> {
    let (Some(a), Some(b)) = (
        project.relations.get(&source),
        project.relations.get(&target),
    ) else {
        return Ok(None);
    };
    let forward =
        a.kind() == RelationKind::CommunicationMean && b.kind() == RelationKind::BoundaryExchange;
    let reverse =
        a.kind() == RelationKind::BoundaryExchange && b.kind() == RelationKind::CommunicationMean;
    if !forward && !reverse {
        return Ok(None);
    }
    let (endpoint, is_source) = match fact {
        FacetReview::Relation(RelationReview::Source(_)) => (a.source(), true),
        FacetReview::Relation(RelationReview::Target(_)) => (a.target(), false),
        _ => return Ok(None),
    };
    let mapped = if forward {
        let decision = request.communication_endpoints.iter().find(|d| d.source == source)
            .ok_or("Taking an OA endpoint requires this exchange's explicit SA component-port decision.")?;
        let port = port_id(if is_source {
            &decision.source_port
        } else {
            &decision.target_port
        });
        let expected_owner = map.get(&endpoint).ok_or(
            "Review the participant counterpart before taking its communication endpoint.",
        )?;
        let e = project
            .elements
            .get(&port)
            .ok_or("Selected communication endpoint port does not exist.")?;
        if e.parent != Some(*expected_owner)
            || e.layer() != Layer::Sa
            || !matches!(
                crate::ports::port_contract(e),
                Some(PortContract::Component { .. })
            )
        {
            return Err(
                "Selected component port disagrees with the reviewed participant counterpart."
                    .into(),
            );
        }
        port
    } else {
        let owner = project
            .elements
            .get(&endpoint)
            .and_then(|e| e.parent)
            .ok_or("SA boundary port needs a participant owner.")?;
        let participant = *map.get(&owner).ok_or(
            "Review the SA port owner's OA participant counterpart before taking this endpoint.",
        )?;
        if !project.elements.get(&participant).is_some_and(|e| {
            e.layer() == Layer::Oa && matches!(e.kind(), Kind::Entity | Kind::Actor)
        }) {
            return Err("Boundary endpoint owner must map to an OA entity or actor.".into());
        }
        participant
    };
    let mut result = fact.clone();
    if let FacetReview::Relation(RelationReview::Source(values) | RelationReview::Target(values)) =
        &mut result
    {
        match request.direction.source_layer() {
            Layer::Oa => values.oa = Observed::Value(mapped),
            Layer::Sa => values.sa = Observed::Value(mapped),
        }
    }
    Ok(Some(result))
}