/**
 * Per-corridor-edge physical load of a train: tare + length of the wagons
 * spanning each edge, plus the cargo weight riding it. Used to validate that
 * a planned mid-route COUPLE keeps every leg within the locomotives' pull
 * weight and train length limits — a wagon cut at Mojo frees its tare/length
 * on the edges past Mojo, a wagon coupled there adds its own only from there.
 */

export interface EdgeLoad {
  weightTons: number;
  lengthMeters: number;
}

export interface EdgeWagonSpan {
  /** Half-open edge span [fromEdge, toEdge) the wagon physically rides. */
  fromEdge: number;
  toEdge: number;
  tareTons: number;
  lengthMeters: number;
}

export interface EdgeCargoLeg {
  fromEdge: number;
  toEdge: number;
  weightTons: number;
}

export function computeEdgeLoads(
  edgeCount: number,
  wagonSpans: readonly EdgeWagonSpan[],
  cargoLegs: readonly EdgeCargoLeg[],
): EdgeLoad[] {
  const loads: EdgeLoad[] = Array.from({ length: Math.max(1, edgeCount) }, () => ({
    weightTons: 0,
    lengthMeters: 0,
  }));
  const clamp = (edge: number) => Math.min(Math.max(edge, 0), loads.length);
  for (const span of wagonSpans) {
    for (let e = clamp(span.fromEdge); e < clamp(span.toEdge); e += 1) {
      loads[e].weightTons += span.tareTons;
      loads[e].lengthMeters += span.lengthMeters;
    }
  }
  for (const cargo of cargoLegs) {
    for (let e = clamp(cargo.fromEdge); e < clamp(cargo.toEdge); e += 1) {
      loads[e].weightTons += cargo.weightTons;
    }
  }
  return loads;
}