import {
  orderWaypointsAlongRoute,
  type Coordinate,
  type RouteResult,
  type VoyageHarbour
} from "@watermaps/shared";
import type { RouteBridgeAssessment } from "./routeWeatherReport";
import type { RouteLock } from "./voyageHarbours";

export type RouteEventKind = "harbour" | "lock" | "bridge";

export type RouteEventCorridors = Record<RouteEventKind, number>;

export const DEFAULT_ROUTE_EVENT_CORRIDORS_NM: Readonly<RouteEventCorridors> = Object.freeze({
  harbour: 1.5,
  lock: 0.25,
  bridge: 0.08
});

export type RouteEventEtaSpeedSource = "gps-sog" | "vessel-cruise-speed";
export type RouteEventEtaReferenceSource = "current-time" | "route-departure";

/**
 * ETA assumptions are deliberately supplied by the caller. This prevents a
 * stale GPS speed or a planned cruise speed from being presented without its
 * provenance.
 */
export type RouteEventEtaBasis = {
  speedKn: number;
  speedSource: RouteEventEtaSpeedSource;
  referenceTime: string | number | Date;
  referenceSource: RouteEventEtaReferenceSource;
};

export type RouteEventEta = {
  estimatedAt: string;
  minutesFromProgress: number;
  speedKn: number;
  speedSource: RouteEventEtaSpeedSource;
  referenceTime: string;
  referenceSource: RouteEventEtaReferenceSource;
};

type RouteEventBase = {
  kind: RouteEventKind;
  id: string;
  name: string;
  coordinate: Coordinate;
  /** Position of the projected feature along the routed geometry. */
  routeDistanceNm: number;
  /** Shortest lateral distance between the feature and the route. */
  distanceFromRouteNm: number;
  remainingNm: number;
  eta: RouteEventEta | null;
};

export type HarbourRouteEvent = RouteEventBase & {
  kind: "harbour";
  feature: VoyageHarbour;
};

export type LockRouteEvent = RouteEventBase & {
  kind: "lock";
  feature: RouteLock;
};

export type BridgeRouteEvent = RouteEventBase & {
  kind: "bridge";
  feature: RouteBridgeAssessment;
};

export type UpcomingRouteEvent =
  | HarbourRouteEvent
  | LockRouteEvent
  | BridgeRouteEvent;

export type NextRouteEventsByKind = {
  harbour: HarbourRouteEvent | null;
  lock: LockRouteEvent | null;
  bridge: BridgeRouteEvent | null;
};

export type UpcomingRouteEventsInput = {
  route: Pick<RouteResult, "geometry" | "distanceNm">;
  harbours?: readonly VoyageHarbour[];
  locks?: readonly RouteLock[];
  bridges?: readonly RouteBridgeAssessment[];
  /** Progress along the route. Invalid or negative values resolve to zero. */
  progressNm?: number | null;
  corridorsNm?: Partial<RouteEventCorridors>;
  etaBasis?: RouteEventEtaBasis | null;
};

type RouteEventCandidate =
  | {
      projectionId: string;
      kind: "harbour";
      id: string;
      name: string;
      coordinate: Coordinate;
      feature: VoyageHarbour;
    }
  | {
      projectionId: string;
      kind: "lock";
      id: string;
      name: string;
      coordinate: Coordinate;
      feature: RouteLock;
    }
  | {
      projectionId: string;
      kind: "bridge";
      id: string;
      name: string;
      coordinate: Coordinate;
      feature: RouteBridgeAssessment;
    };

/**
 * Projects all supplied facilities onto the route, applies a corridor per
 * facility type and returns only the current or upcoming facilities in route
 * order.
 *
 * Every feature is projected again. In particular,
 * RouteBridgeAssessment.distanceNm is intentionally ignored because it is the
 * bridge's lateral distance to the route, not its distance along the route.
 */
export function upcomingRouteEvents(
  input: UpcomingRouteEventsInput
): UpcomingRouteEvent[] {
  const progressNm = normalizeProgress(input.progressNm);
  const corridors = resolveCorridors(input.corridorsNm);
  const candidates = routeEventCandidates(input);
  if (candidates.length === 0) {
    return [];
  }

  const candidatesByProjectionId = new Map(
    candidates.map((candidate) => [candidate.projectionId, candidate])
  );
  const projected = orderWaypointsAlongRoute(
    candidates.map((candidate) => ({
      id: candidate.projectionId,
      name: candidate.name,
      coordinate: candidate.coordinate
    })),
    input.route
  );

  return projected.flatMap<UpcomingRouteEvent>((projection) => {
    const candidate = candidatesByProjectionId.get(projection.id);
    if (
      !candidate ||
      projection.distanceFromRouteNm > corridors[candidate.kind] ||
      projection.routeDistanceNm < progressNm
    ) {
      return [];
    }

    const remainingNm = Math.max(0, projection.routeDistanceNm - progressNm);
    const common = {
      kind: candidate.kind,
      id: candidate.id,
      name: candidate.name,
      coordinate: candidate.coordinate,
      routeDistanceNm: projection.routeDistanceNm,
      distanceFromRouteNm: projection.distanceFromRouteNm,
      remainingNm,
      eta: estimateRouteEventEta(remainingNm, input.etaBasis)
    };

    switch (candidate.kind) {
      case "harbour":
        return [{ ...common, kind: candidate.kind, feature: candidate.feature }];
      case "lock":
        return [{ ...common, kind: candidate.kind, feature: candidate.feature }];
      case "bridge":
        return [{ ...common, kind: candidate.kind, feature: candidate.feature }];
    }
  });
}

export function nextRouteEventsByKind(
  events: readonly UpcomingRouteEvent[]
): NextRouteEventsByKind {
  const next: NextRouteEventsByKind = {
    harbour: null,
    lock: null,
    bridge: null
  };

  for (const event of events) {
    switch (event.kind) {
      case "harbour":
        next.harbour ??= event;
        break;
      case "lock":
        next.lock ??= event;
        break;
      case "bridge":
        next.bridge ??= event;
        break;
    }
  }
  return next;
}

function routeEventCandidates(input: UpcomingRouteEventsInput): RouteEventCandidate[] {
  const candidates: RouteEventCandidate[] = [];

  input.harbours?.forEach((feature, index) => {
    candidates.push({
      projectionId: projectionId("harbour", index, feature.id),
      kind: "harbour",
      id: feature.id,
      name: feature.name,
      coordinate: feature.coordinate,
      feature
    });
  });
  input.locks?.forEach((feature, index) => {
    candidates.push({
      projectionId: projectionId("lock", index, feature.id),
      kind: "lock",
      id: feature.id,
      name: feature.name,
      coordinate: feature.coordinate,
      feature
    });
  });
  input.bridges?.forEach((feature, index) => {
    candidates.push({
      projectionId: projectionId("bridge", index, feature.id),
      kind: "bridge",
      id: feature.id,
      name: feature.name ?? feature.label ?? "Brücke",
      coordinate: feature.coordinate,
      feature
    });
  });

  return candidates;
}

function projectionId(kind: RouteEventKind, index: number, featureId: string) {
  return `${kind}:${index}:${featureId}`;
}

function resolveCorridors(
  overrides: Partial<RouteEventCorridors> | undefined
): RouteEventCorridors {
  return {
    harbour: nonNegativeOrDefault(
      overrides?.harbour,
      DEFAULT_ROUTE_EVENT_CORRIDORS_NM.harbour
    ),
    lock: nonNegativeOrDefault(
      overrides?.lock,
      DEFAULT_ROUTE_EVENT_CORRIDORS_NM.lock
    ),
    bridge: nonNegativeOrDefault(
      overrides?.bridge,
      DEFAULT_ROUTE_EVENT_CORRIDORS_NM.bridge
    )
  };
}

function normalizeProgress(value: number | null | undefined) {
  return typeof value === "number" && Number.isFinite(value)
    ? Math.max(0, value)
    : 0;
}

function nonNegativeOrDefault(value: number | undefined, fallback: number) {
  return typeof value === "number" && Number.isFinite(value) && value >= 0
    ? value
    : fallback;
}

function estimateRouteEventEta(
  remainingNm: number,
  basis: RouteEventEtaBasis | null | undefined
): RouteEventEta | null {
  if (
    !basis ||
    !Number.isFinite(basis.speedKn) ||
    basis.speedKn <= 0
  ) {
    return null;
  }
  const referenceTimestamp = timestampValue(basis.referenceTime);
  if (referenceTimestamp === null) {
    return null;
  }

  const minutesFromProgress = (remainingNm / basis.speedKn) * 60;
  const estimatedTimestamp =
    referenceTimestamp + minutesFromProgress * 60_000;
  if (!Number.isFinite(estimatedTimestamp)) {
    return null;
  }

  return {
    estimatedAt: new Date(estimatedTimestamp).toISOString(),
    minutesFromProgress,
    speedKn: basis.speedKn,
    speedSource: basis.speedSource,
    referenceTime: new Date(referenceTimestamp).toISOString(),
    referenceSource: basis.referenceSource
  };
}

function timestampValue(value: string | number | Date): number | null {
  const timestamp =
    value instanceof Date
      ? value.getTime()
      : typeof value === "number"
        ? value
        : Date.parse(value);
  return Number.isFinite(timestamp) ? timestamp : null;
}