import { t } from '@/i18n';
import { formatValue } from '@/lib/format';
import type { FormatSpec as Spec } from '@/lib/types';
import { firstLast, type SeriesPoint } from './scales';

/** "Canada's GDP per capita rose from US$21.4k in 1990 to US$53.4k in 2024." */
export function summarizeSeries(subject: string, points: SeriesPoint[], spec: Spec): string {
  const fl = firstLast(points);
  if (!fl) return t('chart.noData');
  const from = formatValue(fl.first.value, spec);
  const to = formatValue(fl.last.value, spec);
  const key =
    fl.last.value! > fl.first.value! ? 'chart.summary.rose' : fl.last.value! < fl.first.value! ? 'chart.summary.fell' : 'chart.summary.flat';
  return t(key, { subject, from, y0: fl.first.year, to, y1: fl.last.year });
}

export function summarizeMulti(names: string[], allPoints: SeriesPoint[][]): string {
  const years = allPoints.flat().map((p) => p.year);
  const y0 = Math.min(...years);
  const y1 = Math.max(...years);
  return t('chart.summary.multi', { n: names.length, y0, y1, names: names.join(', ') });
}