"use client";

import { useCallback, useRef, useState } from "react";
import { useRouter } from "next/navigation";
import { useQueryClient } from "@tanstack/react-query";
import { berlinCalendarDay } from "@/lib/dates";
import { ApiError } from "@/lib/auth/api-client";
import { useCurrentUserId } from "@/lib/auth/auth-context";
import { hiveConflictOf, hiveKeys, postHiveChange } from "@/lib/hive/api";
import { deriveHiveFacts } from "@/lib/hive/facts";
import { hasQueuedHiveChange } from "@/lib/hive/pending";
import { applyHiveOps } from "@/lib/hive/ops";
import { fetchColonyTreatments } from "@/lib/treatments/api";
import { queueHiveChange } from "@/lib/offline/db";
import { newIdempotencyKey } from "@/lib/offline/idempotency";
import { syncPendingEntries } from "@/lib/offline/sync";
import { OFFLINE_QUEUE_QUERY_KEY } from "@/lib/offline/use-capture-mutation";
import type {
  ClientHiveChangeSource,
  HiveApplyResult,
  HiveCatalog,
  HiveOp,
  HiveSetupView,
  HiveState,
} from "@/lib/hive/types";
import { showHiveFollowUps } from "./follow-up-toast";

/** The server refused the ops against its newer state (409 HIVE_CONFLICT). */
export interface HiveConflict {
  /** The state the server holds now. */
  current: { version: number; state: HiveState };
  /** The user's own ops. */
  ops: HiveOp[];
  /** The ops re-applied to `current.state`; a failure carries op index and reason. */
  preview: HiveApplyResult;
}

export interface HiveMutation {
  /** Resolves with the saved setup; null when the change was queued and no setup is loaded to show it on. */
  submit(
    ops: HiveOp[],
    source: ClientHiveChangeSource,
    occurredOn?: string,
  ): Promise<HiveSetupView | null>;
  conflict: HiveConflict | null;
  /** "retry" sends the ops again against the current state (new key); "discard" drops them. */
  resolveConflict(action: "retry" | "discard"): Promise<void>;
  isPending: boolean;
}

interface Attempt {
  ops: HiveOp[];
  source: ClientHiveChangeSource;
  occurredOn: string;
}

/** Thrown for a submit while another one of this hook is still running. */
export const HIVE_BUSY_MESSAGE = "HIVE_BUSY";

/** Same ops, source and day: a manual re-press after a network error. */
function signatureOf(attempt: Attempt): string {
  return JSON.stringify([attempt.source, attempt.occurredOn, attempt.ops]);
}

/** No verdict from the server (network, timeout, 5xx): the change may or may not be saved. */
function isAmbiguousFailure(error: unknown): boolean {
  return !(error instanceof ApiError) || error.status >= 500;
}

function withState(view: HiveSetupView, state: HiveState, version: number, catalog: HiveCatalog): HiveSetupView {
  return { ...view, version, state, facts: deriveHiveFacts(state, catalog) };
}

/**
 * Posts a change of the colony's hive. The cache shows the result at once
 * (optimistic); a failure refetches it. One submit at a time. An attempt keeps
 * its idempotency key across manual re-presses after a network error or 5xx;
 * a retry after a conflict gets a fresh one. Follow-up toasts are suggestions only.
 * A card change that fails at network level goes into the offline queue
 * `pending-hive-changes` under the same key (spec 10); the card shows it from
 * there, so the cache keeps the state it had.
 */
export function useHiveMutation(colonyId: string, catalog: HiveCatalog): HiveMutation {
  const queryClient = useQueryClient();
  const router = useRouter();
  const ownerUserId = useCurrentUserId();
  const [conflict, setConflict] = useState<HiveConflict | null>(null);
  const [pendingCount, setPendingCount] = useState(0);
  const lastAttempt = useRef<Attempt | null>(null);
  const inFlight = useRef(false);
  // Key of an attempt that failed without a verdict (network, 5xx): a re-press reuses it.
  const failedKey = useRef<{ signature: string; key: string } | null>(null);
  const queryKey = hiveKeys.detail(colonyId);

  const hasOpenTreatment = useCallback(async (): Promise<boolean> => {
    try {
      const treatments = await queryClient.fetchQuery({
        queryKey: ["colonies", colonyId, "treatments"],
        queryFn: () => fetchColonyTreatments(colonyId),
      });
      return treatments.some((treatment) => treatment.endDate == null);
    } catch {
      return false;
    }
  }, [colonyId, queryClient]);

  const suggestFollowUps = useCallback(
    async (attempt: Attempt, before: HiveState, after: HiveState): Promise<void> => {
      const { ops, occurredOn } = attempt;
      const open = ops.some((op) => op.op === "removePart") ? await hasOpenTreatment() : false;
      showHiveFollowUps(ops, before, after, catalog, {
        colonyId,
        occurredOn,
        navigate: (href) => router.push(href),
        hasOpenTreatment: open,
      });
    },
    [catalog, colonyId, hasOpenTreatment, router],
  );

  const run = useCallback(
    async (attempt: Attempt): Promise<HiveSetupView | null> => {
      if (inFlight.current) throw new Error(HIVE_BUSY_MESSAGE);
      inFlight.current = true;
      const { ops, source, occurredOn } = attempt;
      const signature = signatureOf(attempt);
      const key =
        failedKey.current?.signature === signature ? failedKey.current.key : newIdempotencyKey();
      setPendingCount((count) => count + 1);
      try {
        // A running refetch must not overwrite the optimistic state.
        await queryClient.cancelQueries({ queryKey });
        const previous = queryClient.getQueryData<HiveSetupView>(queryKey);
        // Behind an earlier queued change of this colony it must not overtake: queue it too,
        // whether or not the card has a setup loaded.
        if (ownerUserId && source === "CARD" && (await hasQueuedHiveChange(colonyId, ownerUserId))) {
          await queueHiveChange({ colonyId, occurredOn, source, ops }, key, ownerUserId);
          void queryClient.invalidateQueries({ queryKey: OFFLINE_QUEUE_QUERY_KEY });
          // Online again, the queue goes out in order.
          void syncPendingEntries(ownerUserId, { afterChange: true }).catch(() => undefined);
          if (!previous) return null;
          const queued = applyHiveOps(previous.state, ops, catalog);
          return queued.ok ? withState(previous, queued.state, previous.version, catalog) : previous;
        }
        if (previous) {
          const applied = applyHiveOps(previous.state, ops, catalog);
          if (applied.ok) {
            queryClient.setQueryData(queryKey, withState(previous, applied.state, previous.version, catalog));
          }
        }
        let optimistic: HiveSetupView | undefined;
        if (previous) optimistic = queryClient.getQueryData<HiveSetupView>(queryKey);
        try {
          const view = await postHiveChange(colonyId, { occurredOn, source, ops }, key);
          queryClient.setQueryData(queryKey, view);
          setConflict(null);
          lastAttempt.current = null;
          failedKey.current = null;
          void queryClient.invalidateQueries({ queryKey: hiveKeys.history(colonyId) });
          if (previous) {
            // Follow-ups are best effort: a failing suggestion must not fail the saved change.
            suggestFollowUps(attempt, previous.state, view.state).catch(() => {});
          }
          return view;
        } catch (error) {
          const body = hiveConflictOf(error);
          if (body) {
            failedKey.current = null;
            lastAttempt.current = attempt;
            if (previous) {
              queryClient.setQueryData(
                queryKey,
                withState(previous, body.current.state, body.current.version, catalog),
              );
            }
            setConflict({
              current: body.current,
              ops,
              preview: applyHiveOps(body.current.state, ops, catalog),
            });
          } else if (previous && ownerUserId && source === "CARD" && !(error instanceof ApiError)) {
            // No network: queue it. The pending ops are shown on top of the loaded state.
            await queueHiveChange({ colonyId, occurredOn, source, ops }, key, ownerUserId);
            failedKey.current = null;
            lastAttempt.current = null;
            if (optimistic && queryClient.getQueryData(queryKey) === optimistic) {
              queryClient.setQueryData(queryKey, previous);
            }
            void queryClient.invalidateQueries({ queryKey: OFFLINE_QUEUE_QUERY_KEY });
            return optimistic ?? previous;
          } else {
            failedKey.current = isAmbiguousFailure(error) ? { signature, key } : null;
            // Restore only if nobody changed the cache since our optimistic write; then refetch.
            if (previous && optimistic && queryClient.getQueryData(queryKey) === optimistic) {
              queryClient.setQueryData(queryKey, previous);
            }
            void queryClient.invalidateQueries({ queryKey });
          }
          throw error;
        }
      } finally {
        inFlight.current = false;
        setPendingCount((count) => count - 1);
      }
    },
    [catalog, colonyId, ownerUserId, queryClient, queryKey, suggestFollowUps],
  );

  const submit = useCallback(
    (ops: HiveOp[], source: ClientHiveChangeSource, occurredOn?: string) =>
      run({ ops, source, occurredOn: occurredOn ?? berlinCalendarDay(new Date().toISOString()) }),
    [run],
  );

  const resolveConflict = useCallback(
    async (action: "retry" | "discard"): Promise<void> => {
      const attempt = lastAttempt.current;
      if (action === "discard" || !attempt) {
        lastAttempt.current = null;
        setConflict(null);
        return;
      }
      if (conflict && !conflict.preview.ok) return;
      try {
        await run(attempt);
      } catch (error) {
        // A new conflict is already in `conflict`; anything else is for the caller.
        if (!hiveConflictOf(error)) throw error;
      }
    },
    [conflict, run],
  );

  return { submit, conflict, resolveConflict, isPending: pendingCount > 0 };
}