frontend/src/hooks/useWorldSimulation.ts

import { useCallback, useEffect, useMemo, useRef, useState } from "react";

import {
  ApiResponseError,
  fetchAdminModels,
  fetchWorldSnapshot,
  setNpcModelProfile,
  tickWorld,
} from "../api";
import type { GameLogEventSnapshot, ModelProfileSnapshot, WorldSnapshot } from "../types";

// When enabled, the manual tick controls are hidden and the world advances on its
// own. Defaults to on; set VITE_WORLD_SIMULATOR_AUTOPLAY=0/false/no to show the
// manual controls instead.
const AUTOPLAY = !["0", "false", "no"].includes(
  String(import.meta.env.VITE_WORLD_SIMULATOR_AUTOPLAY ?? "").toLowerCase(),
);

export function useWorldSimulation() {
  const [snapshot, setSnapshot] = useState<WorldSnapshot | null>(null);
  const [isTickPending, setIsTickPending] = useState(false);
  const [isAutoTicking, setIsAutoTicking] = useState(AUTOPLAY);
  const [isModelSwitchPending, setIsModelSwitchPending] = useState(false);
  const [modelProfiles, setModelProfiles] = useState<ModelProfileSnapshot[]>([]);
  const [error, setError] = useState<string | null>(null);
  const [selectedId, setSelectedId] = useState<string | null>(null);
  const isTickingRef = useRef(false);
  const eventHistory = useEventHistory(snapshot);

  const refresh = useCallback(async () => {
    const nextSnapshot = await fetchWorldSnapshot();
    setSnapshot(nextSnapshot);
    setError(null);
  }, []);

  const isServerTickPending = snapshot?.simulation.tick_in_progress ?? false;
  const isWaitingForTick = isTickPending || isServerTickPending;
  const isWorldCommandPending = isWaitingForTick;

  const step = useCallback(async () => {
    if (isTickingRef.current || snapshot?.simulation.tick_in_progress) {
      return;
    }
    isTickingRef.current = true;
    setIsTickPending(true);
    setError(null);
    try {
      await tickWorld();
      await refresh();
    } catch (nextError) {
      if (nextError instanceof ApiResponseError && nextError.status === 409) {
        await refresh().catch((refreshError: unknown) => {
          setError(refreshError instanceof Error ? refreshError.message : "World refresh failed");
        });
      } else {
        setError(nextError instanceof Error ? nextError.message : "World update failed");
        setIsAutoTicking(false);
      }
    } finally {
      isTickingRef.current = false;
      setIsTickPending(false);
    }
  }, [refresh, snapshot?.simulation.tick_in_progress]);

  const refreshModelProfiles = useCallback(async () => {
    const adminModels = await fetchAdminModels();
    setModelProfiles(adminModels.profiles);
  }, []);

  const setNpcModel = useCallback(
    async (npcId: string, profileId: string) => {
      setIsModelSwitchPending(true);
      setError(null);
      try {
        await setNpcModelProfile(npcId, profileId);
        await refresh();
        await refreshModelProfiles();
      } catch (nextError) {
        setError(nextError instanceof Error ? nextError.message : "NPC model switch failed");
      } finally {
        setIsModelSwitchPending(false);
      }
    },
    [refresh, refreshModelProfiles],
  );

  useInitialSnapshot(setSnapshot, setSelectedId, setError);
  useInitialModelProfiles(setModelProfiles);
  useSelectedEntityFallback(snapshot, setSelectedId);
  useServerTickPolling(isServerTickPending, refresh, setError);
  useIdleSnapshotPolling({
    isIdle: snapshot !== null && !isAutoTicking && !isWaitingForTick,
    refresh,
    setError,
  });
  useAutoTicks({
    currentTick: snapshot?.tick ?? null,
    isAutoTicking,
    isWaitingForTick,
    hasSnapshot: snapshot !== null,
    step,
    setError,
    setIsAutoTicking,
  });
  useModelStatusPolling(snapshot, refresh, setError);
  useAutoplayRearm(isAutoTicking, snapshot !== null, setIsAutoTicking);

  const selectedEntity = useMemo(
    () => snapshot?.entities.find((entity) => entity.id === selectedId) ?? null,
    [selectedId, snapshot],
  );

  const selectedBeast = useMemo(
    () => snapshot?.beasts?.find((beast) => beast.id === selectedId) ?? null,
    [selectedId, snapshot],
  );

  const selectedResource = useMemo(
    () => snapshot?.resource_nodes?.find((node) => node.id === selectedId) ?? null,
    [selectedId, snapshot],
  );

  const selectedHouse = useMemo(
    () => snapshot?.houses?.find((house) => house.id === selectedId) ?? null,
    [selectedId, snapshot],
  );

  return {
    error,
    eventHistory,
    hideTickControls: AUTOPLAY,
    isAutoTicking,
    isModelSwitchPending,
    isWaitingForTick,
    isWorldCommandPending,
    modelProfiles,
    selectedBeast,
    selectedEntity,
    selectedHouse,
    selectedResource,
    selectedId,
    setIsAutoTicking,
    setNpcModel,
    setSelectedId,
    snapshot,
    step,
  };
}

function useInitialModelProfiles(
  setModelProfiles: (profiles: ModelProfileSnapshot[]) => void,
) {
  useEffect(() => {
    const abortController = new AbortController();
    fetchAdminModels(abortController.signal)
      .then((adminModels) => {
        setModelProfiles(adminModels.profiles);
      })
      .catch(() => {
        if (!abortController.signal.aborted) {
          setModelProfiles([]);
        }
      });

    return () => abortController.abort();
  }, [setModelProfiles]);
}

function useEventHistory(snapshot: WorldSnapshot | null): GameLogEventSnapshot[] {
  const seenKeysRef = useRef<Set<string>>(new Set());
  const [history, setHistory] = useState<GameLogEventSnapshot[]>([]);

  useEffect(() => {
    const log = snapshot?.event_log ?? [];
    if (log.length === 0) {
      return;
    }
    const fresh: GameLogEventSnapshot[] = [];
    for (const event of log) {
      const key = [
        event.tick,
        event.type,
        event.actor_id ?? "",
        event.target_id ?? "",
        event.summary,
      ].join("|");
      if (!seenKeysRef.current.has(key)) {
        seenKeysRef.current.add(key);
        fresh.push(event);
      }
    }
    if (fresh.length > 0) {
      setHistory((current) => [...current, ...fresh].slice(-500));
    }
  }, [snapshot]);

  return history;
}

function useInitialSnapshot(
  setSnapshot: (snapshot: WorldSnapshot) => void,
  setSelectedId: (id: string | null) => void,
  setError: (error: string | null) => void,
) {
  useEffect(() => {
    const abortController = new AbortController();
    fetchWorldSnapshot(abortController.signal, { warmup: true })
      .then((nextSnapshot) => {
        setSnapshot(nextSnapshot);
        setSelectedId(nextSnapshot.entities[0]?.id ?? null);
        setError(null);
      })
      .catch((nextError: unknown) => {
        if (!abortController.signal.aborted) {
          setError(nextError instanceof Error ? nextError.message : "World load failed");
        }
      });

    return () => abortController.abort();
  }, [setError, setSelectedId, setSnapshot]);
}

function useSelectedEntityFallback(
  snapshot: WorldSnapshot | null,
  setSelectedId: (updater: (currentId: string | null) => string | null) => void,
) {
  useEffect(() => {
    if (!snapshot) {
      return;
    }

    setSelectedId((currentId) => {
      if (!currentId) {
        return null;
      }
      const stillExists =
        snapshot.entities.some((entity) => entity.id === currentId) ||
        (snapshot.beasts ?? []).some((beast) => beast.id === currentId) ||
        (snapshot.resource_nodes ?? []).some((node) => node.id === currentId) ||
        (snapshot.houses ?? []).some((house) => house.id === currentId);
      return stillExists ? currentId : null;
    });
  }, [snapshot, setSelectedId]);
}

function useServerTickPolling(
  isServerTickPending: boolean,
  refresh: () => Promise<void>,
  setError: (error: string | null) => void,
) {
  useEffect(() => {
    if (!isServerTickPending) {
      return undefined;
    }
    return pollEvery(1500, refresh, setError);
  }, [isServerTickPending, refresh, setError]);
}

type IdleSnapshotPollingOptions = {
  isIdle: boolean;
  refresh: () => Promise<void>;
  setError: (error: string | null) => void;
};

function useIdleSnapshotPolling(options: IdleSnapshotPollingOptions) {
  const { isIdle, refresh, setError } = options;
  useEffect(() => {
    if (!isIdle) {
      return undefined;
    }
    return pollEvery(2000, refresh, setError);
  }, [isIdle, refresh, setError]);
}

type AutoTickOptions = {
  currentTick: number | null;
  isAutoTicking: boolean;
  isWaitingForTick: boolean;
  hasSnapshot: boolean;
  step: () => Promise<void>;
  setError: (error: string | null) => void;
  setIsAutoTicking: (value: boolean) => void;
};

function useAutoTicks(options: AutoTickOptions) {
  const {
    currentTick,
    isAutoTicking,
    isWaitingForTick,
    hasSnapshot,
    step,
    setError,
    setIsAutoTicking,
  } = options;

  useEffect(() => {
    if (!isAutoTicking || !hasSnapshot || isWaitingForTick) {
      return undefined;
    }

    const timeoutId = window.setTimeout(() => {
      step().catch((nextError: unknown) => {
        setError(nextError instanceof Error ? nextError.message : "World update failed");
        setIsAutoTicking(false);
      });
    }, 500);

    return () => window.clearTimeout(timeoutId);
  }, [
    currentTick,
    hasSnapshot,
    isAutoTicking,
    isWaitingForTick,
    setError,
    setIsAutoTicking,
    step,
  ]);
}

// In autoplay mode the manual controls are hidden, so a transient error that
// pauses auto-ticking must be recovered automatically; otherwise the world would
// halt with no way to restart it.
function useAutoplayRearm(
  isAutoTicking: boolean,
  hasSnapshot: boolean,
  setIsAutoTicking: (value: boolean) => void,
) {
  useEffect(() => {
    if (!AUTOPLAY || isAutoTicking || !hasSnapshot) {
      return undefined;
    }
    const timeoutId = window.setTimeout(() => setIsAutoTicking(true), 2000);
    return () => window.clearTimeout(timeoutId);
  }, [isAutoTicking, hasSnapshot, setIsAutoTicking]);
}

function useModelStatusPolling(
  snapshot: WorldSnapshot | null,
  refresh: () => Promise<void>,
  setError: (error: string | null) => void,
) {
  const modelStatuses = snapshot?.simulation.models ?? [];
  useEffect(() => {
    if (!snapshot || !modelStatuses.some((model) => model.status !== "ready")) {
      return undefined;
    }
    return pollEvery(2000, refresh, setError);
  }, [modelStatuses, refresh, setError, snapshot]);
}

function pollEvery(
  intervalMs: number,
  refresh: () => Promise<void>,
  setError: (error: string | null) => void,
) {
  const intervalId = window.setInterval(() => {
    refresh().catch((nextError: unknown) => {
      setError(nextError instanceof Error ? nextError.message : "World refresh failed");
    });
  }, intervalMs);

  return () => window.clearInterval(intervalId);
}