import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
import type { BackendStatus } from '../../app/app-state';
import type { FindingRecord } from '../../domain/finding';
import { AssessorApiClient } from '../../api/assessor-api-client';
import { useEnginePreferences } from '../../app/engine-preferences';
import { mappingRunKey, subscribeRegulatoryMappingRuns, trackRegulatoryMappingRun } from './mapping-run-tracker';
import { markRegulatoryDecisionSaved } from './decision-revision';
import {
  acceptedControlIds,
  type RegulatoryMappingCandidate,
  type RegulatoryMappingDecisionValue,
  type RegulatoryMappingResponse
} from '../regulatory-mapping';

/** An accepted control as the Finding Reader names it. */
export interface AcceptedRegulatoryControl {
  controlId: string;
  annexAControlId: string;
  title?: string;
}

const assessorApi = new AssessorApiClient();

export function useRegulatoryMapping(
  projectId: string,
  /** Result DB row of the record: a scanner finding occurrence or a GPO baseline comparison. */
  resultProjectionId: string,
  backendStatus: BackendStatus
) {
  // A switched-off Compliance Engine shows no control, opens nothing and sends no request.
  const available = useEnginePreferences().compliance;
  const [requestedOpen, setOpen] = useState(false);
  const open = requestedOpen && available;
  // Re-enabling the engine starts with the window closed again.
  useEffect(() => { if (!available) setOpen(false); }, [available]);
  const [storedResponse, setStoredResponse] = useState<{ scope: { key: string }; value: RegulatoryMappingResponse }>();
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState('');
  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);
      trackRegulatoryMappingRun(projectId, resultProjectionId, next);
      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]);

  // Loaded with the finding, so the reader can name its accepted controls. A running mapping is polled
  // once by the run tracker, which keeps its activity entry until the backend ends it.
  useEffect(() => { if (available && !response && !loading && !error) void load(); }, [available, error, load, loading, response]);
  useEffect(() => subscribeRegulatoryMappingRuns((key, next) => {
    if (key === mappingRunKey(projectId, resultProjectionId) && activeScope.current === requestScope) setStoredResponse({ scope: requestScope, value: next });
  }), [projectId, requestScope, resultProjectionId]);

  const start = useCallback(async () => {
    if (!projectId || !resultProjectionId || activeScope.current !== requestScope) return;
    setLoading(true);
    try {
      const next = await assessorApi.generateRegulatoryMappings(projectId, { resultProjectionId });
      trackRegulatoryMappingRun(projectId, resultProjectionId, next);
      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 } : {})
      });
      markRegulatoryDecisionSaved();
      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 acceptedControls = useMemo<AcceptedRegulatoryControl[]>(() => available && response
    ? acceptedControlIds(response.decisions).map(controlId => {
      const candidate = response.run?.candidates.find(item => item.controlId === controlId);
      return { controlId, annexAControlId: candidate?.annexAControlId ?? `A.${controlId}`, ...(candidate?.title ? { title: candidate.title } : {}) };
    }).sort((left, right) => left.controlId.localeCompare(right.controlId, 'en', { numeric: true }))
    : [], [available, response]);

  const localDisabledReason = !resultProjectionId ? 'This record has no stored finding or current GPO baseline comparison.'
    : backendStatus !== 'connected' ? 'The backend is not connected.'
      : response && !response.generationEnabled ? response.disabledReason ?? 'Regulatory mapping is unavailable.' : undefined;

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

/** Names the stored Result DB row an ISO mapping is keyed from; empty when the record has none. */
export function regulatoryMappingResultId(record: Pick<FindingRecord, 'findingOccurrenceId' | 'policyComparisonId'>): string {
  if (record.findingOccurrenceId) return `scanner-finding:${record.findingOccurrenceId}`;
  return record.policyComparisonId ? `policy-evaluation-comparison:${record.policyComparisonId}` : '';
}