import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
import type { BackendStatus } from '../../app/app-state';
import { AssessorApiClient } from '../../api/assessor-api-client';
import type {
  RegulatoryMappingCandidate,
  RegulatoryMappingDecisionValue,
  RegulatoryMappingResponse
} from '../../domain/regulatory-mapping';

const assessorApi = new AssessorApiClient();

export function useRegulatoryMapping(
  projectId: string,
  occurrenceId: string | undefined,
  backendStatus: BackendStatus
) {
  const [open, setOpen] = useState(false);
  const [storedResponse, setStoredResponse] = useState<{ scope: { key: string }; value: RegulatoryMappingResponse }>();
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState('');
  const resultProjectionId = occurrenceId ? `scanner-finding:${occurrenceId}` : '';
  const scopeKey = `${projectId}\u0000${resultProjectionId}\u0000${backendStatus}`;
  const activeScope = useRef({ key: scopeKey });
  if (activeScope.current.key !== scopeKey) activeScope.current = { key: scopeKey };
  const requestScope = activeScope.current;
  const response = storedResponse?.scope === requestScope ? storedResponse.value : undefined;

  useEffect(() => {
    setOpen(false);
    setStoredResponse(undefined);
    setLoading(false);
    setError('');
  }, [scopeKey]);

  const load = useCallback(async () => {
    if (!projectId || !resultProjectionId || backendStatus !== 'connected' || activeScope.current !== requestScope) return;
    setLoading(true);
    try {
      const next = await assessorApi.getRegulatoryMappings(projectId, resultProjectionId);
      if (activeScope.current !== requestScope) return;
      setStoredResponse({ scope: requestScope, value: next });
      setError('');
    } catch (reason) {
      if (activeScope.current !== requestScope) return;
      setError(reason instanceof Error ? reason.message : 'Regulatory mapping could not be loaded.');
    } finally {
      if (activeScope.current === requestScope) setLoading(false);
    }
  }, [backendStatus, projectId, requestScope, resultProjectionId]);

  useEffect(() => { if (open && !response && !loading && !error) void load(); }, [error, load, loading, open, response]);
  useEffect(() => {
    if (!open || !response || !['queued', 'running'].includes(response.state)) return;
    const timeout = window.setTimeout(() => void load(), response.pollAfterMs ?? 1_500);
    return () => window.clearTimeout(timeout);
  }, [load, open, response]);

  const start = useCallback(async () => {
    if (!projectId || !resultProjectionId || activeScope.current !== requestScope) return;
    setLoading(true);
    try {
      const next = await assessorApi.generateRegulatoryMappings(projectId, { resultProjectionId });
      if (activeScope.current !== requestScope) return;
      setStoredResponse({ scope: requestScope, value: next });
      setError('');
    } catch (reason) {
      if (activeScope.current !== requestScope) return;
      setError(reason instanceof Error ? reason.message : 'Regulatory mapping could not be started.');
    } finally {
      if (activeScope.current === requestScope) setLoading(false);
    }
  }, [projectId, requestScope, resultProjectionId]);

  const decide = useCallback(async (candidate: RegulatoryMappingCandidate, decision: RegulatoryMappingDecisionValue, comment?: string) => {
    if (!projectId || !resultProjectionId || !response?.run || activeScope.current !== requestScope) return;
    const latest = response.decisions.find(item => item.controlId === candidate.controlId);
    setLoading(true);
    try {
      const next = await assessorApi.saveRegulatoryMappingDecision(projectId, {
        resultProjectionId,
        controlId: candidate.controlId,
        decision,
        ...(comment?.trim() ? { comment: comment.trim() } : {}),
        ...(latest ? { expectedLatestDecisionId: latest.id } : {})
      });
      if (activeScope.current !== requestScope) return;
      setStoredResponse({ scope: requestScope, value: next });
      setError('');
    } catch (reason) {
      if (activeScope.current !== requestScope) return;
      setError(reason instanceof Error ? reason.message : 'The mapping decision could not be saved.');
    } finally {
      if (activeScope.current === requestScope) setLoading(false);
    }
  }, [projectId, requestScope, response, resultProjectionId]);

  const acceptedCount = useMemo(() => {
    const latest = new Map<string, RegulatoryMappingDecisionValue>();
    response?.decisions.forEach(item => { if (!latest.has(item.controlId)) latest.set(item.controlId, item.decision); });
    return [...latest.values()].filter(value => value === 'accepted').length;
  }, [response]);

  const localDisabledReason = !occurrenceId ? 'This record has no canonical finding occurrence.'
    : backendStatus !== 'connected' ? 'The backend is not connected.'
      : response && !response.generationEnabled ? response.disabledReason ?? 'Regulatory mapping is unavailable.' : undefined;

  return {
    open,
    setOpen,
    response,
    loading,
    error,
    start,
    decide,
    acceptedCount,
    disabledReason: localDisabledReason
  };
}