//! Rebuild-queue cancel endpoint for the dashboard.

use axum::{
    extract::{Path as AxumPath, State},
    response::{IntoResponse, Response},
};

use super::AppState;

#[derive(serde::Serialize, utoipa::ToSchema)]
pub(super) struct CancelResultBody {
    cancelled: bool,
}

/// Drop still-queued work from the job
/// queue.
///
/// `id` is a **node** id. A DAG's root cancels the whole group (the scheduler
/// cascades to pending descendants), which is what the dashboard's cancel
/// button sends today — a DAG id *is* its root node's id. An interior node
/// cancels just that branch.
///
/// Refuses `Running` / terminal nodes: an
/// in-flight node owns the agent's nix store + nixos-container update
/// lock and can't be safely interrupted from the queue side. Always
/// returns 200; the body is `{"cancelled": true}` on a successful
/// flip to Cancelled, `{"cancelled": false}` when the DAG was
/// Running / terminal / gone. On success a fresh `RebuildQueueChanged`
/// snapshot fires so the state flip surfaces live.
#[utoipa::path(
    post,
    path = "/api/rebuild-queue/{id}/cancel",
    params(("id" = u64, Path, description = "job-queue node id (a DAG's root cancels the group)")),
    responses((status = 200, description = "whether the DAG was cancelled", body = CancelResultBody)),
    tag = "rebuild_queue"
)]
pub(super) async fn post_rebuild_queue_cancel(
    State(state): State<AppState>,
    AxumPath(id): AxumPath<u64>,
) -> Response {
    if state.coord.job_queue.cancel(id) {
        // Any terminal side effect is the DAG's own spared tail node, which the
        // scheduler picks up on its next pass — nothing to fire from here.
        state.coord.emit_rebuild_queue_snapshot();
        axum::Json(CancelResultBody { cancelled: true }).into_response()
    } else {
        axum::Json(CancelResultBody { cancelled: false }).into_response()
    }
}