// Fetches the daily market aggregate series for a given listing-type +
// bedroom band. Re-fetches when the inputs change. Returns the raw array
// of points plus a derived "now vs N days ago" delta the strip renders.

import { useEffect, useState } from 'react';
import type { AuthUser } from '@/auth/types';
import type { MarketTrendPoint } from '@/types';
import { apiRequest } from '@/services/apiClient';

export interface MarketTrendDelta {
  metric: 'median_total_price' | 'median_qmprice' | 'listing_count';
  current: number | null;
  previous: number | null;
  changePct: number | null;
}

export interface UseMarketTrendResult {
  series: MarketTrendPoint[];
  isLoading: boolean;
  error: string | null;
  // Convenience: today's value vs the oldest in-window value.
  deltas: Record<MarketTrendDelta['metric'], MarketTrendDelta>;
}

function buildDelta(
  metric: MarketTrendDelta['metric'],
  series: MarketTrendPoint[],
): MarketTrendDelta {
  if (series.length < 2) {
    const only = series[0];
    return {
      metric,
      current: only ? (only[metric] as number | null) : null,
      previous: null,
      changePct: null,
    };
  }
  const current = series[series.length - 1][metric] as number | null;
  const previous = series[0][metric] as number | null;
  if (current === null || previous === null || previous === 0) {
    return { metric, current, previous, changePct: null };
  }
  const changePct = Math.round(((current - previous) / previous) * 1000) / 10;
  return { metric, current, previous, changePct };
}

export function useMarketTrend(
  user: AuthUser | null,
  listingType: 'RENT' | 'BUY',
  minBedrooms: number,
  maxBedrooms: number,
  days: number = 30,
): UseMarketTrendResult {
  const [series, setSeries] = useState<MarketTrendPoint[]>([]);
  const [isLoading, setIsLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    if (!user) return;
    let cancelled = false;
    setIsLoading(true);
    setError(null);
    const params = new URLSearchParams({
      listing_type: listingType,
      min_bedrooms: String(minBedrooms),
      max_bedrooms: String(maxBedrooms),
      days: String(days),
    });
    apiRequest<MarketTrendPoint[]>(user, `/api/market_trend?${params}`)
      .then((data) => {
        if (cancelled) return;
        setSeries(data);
      })
      .catch((err: Error) => {
        if (cancelled) return;
        setError(err.message);
      })
      .finally(() => {
        if (!cancelled) setIsLoading(false);
      });
    return () => {
      cancelled = true;
    };
  }, [user, listingType, minBedrooms, maxBedrooms, days]);

  const deltas: UseMarketTrendResult['deltas'] = {
    median_total_price: buildDelta('median_total_price', series),
    median_qmprice: buildDelta('median_qmprice', series),
    listing_count: buildDelta('listing_count', series),
  };

  return { series, isLoading, error, deltas };
}