'use client';
import { createContext, useCallback, useContext, useMemo, useState, type ReactNode } from 'react';
import type { FormatSpec, ObservationStatus, Provenance } from '@/lib/types';

/** Indicator description the sheet needs (built from a MetricValue or an IndicatorCard). */
export interface ProvenanceIndicator extends FormatSpec {
  slug: string;
  name: string;
  methodology?: string | null;
  description?: string | null;
}

/** The value being explained (a MetricValue or a SeriesValue reduced to what the sheet shows). */
export interface ProvenanceValue {
  value: number | null;
  formatted?: string | null;
  period: string | null;
  year?: number | null;
  unit?: string | null;
  is_estimate?: boolean;
  is_forecast?: boolean;
  status?: ObservationStatus | string | null;
  provenance: Provenance | null;
}

export interface ProvenancePayload {
  indicator: ProvenanceIndicator;
  value: ProvenanceValue | null;
  country?: { id: string; slug: string | null; name: string; flag?: string | null } | null;
  /** Override download link; defaults to the country CSV, else the indicator CSV. */
  downloadHref?: string;
  /** Optional data-quality facts for the series (badges are derived when absent). */
  quality?: {
    badges?: Array<'fresh' | 'historical' | 'sparse' | 'limited-coverage' | 'stale' | 'flagged' | 'forecast'>;
    firstYear?: number | null;
    latestYear?: number | null;
    points?: number | null;
    missingYears?: number | null;
    continuityPct?: number | null;
    coveragePct?: number | null;
    referenceYear?: number | null;
  } | null;
}

interface Ctx {
  payload: ProvenancePayload | null;
  open: (p: ProvenancePayload) => void;
  close: () => void;
}

const ProvenanceCtx = createContext<Ctx | null>(null);

export function ProvenanceProvider({ children }: { children: ReactNode }) {
  const [payload, setPayload] = useState<ProvenancePayload | null>(null);
  const open = useCallback((p: ProvenancePayload) => setPayload(p), []);
  const close = useCallback(() => setPayload(null), []);
  const value = useMemo(() => ({ payload, open, close }), [payload, open, close]);
  return <ProvenanceCtx.Provider value={value}>{children}</ProvenanceCtx.Provider>;
}

export function useProvenance(): Ctx {
  const ctx = useContext(ProvenanceCtx);
  if (!ctx) return { payload: null, open: () => {}, close: () => {} };
  return ctx;
}