---

import { type LineData, PriceScaleMode, type WhitespaceData } from 'lightweight-charts';

import type {
  DailyClose,
  SeasonalityChange,
  SeasonalityRange,
  SeasonalityScale,
  SeasonalityTableRow,
  SeasonalityYear,
} from '@src/types';

type SeriesDatum = LineData | WhitespaceData;

const CALENDAR = Array.from({ length: 366 }, (_, day) =>
  new Date(Date.UTC(2000, 0, day + 1)).toISOString().slice(0, 10),
);

export function normalizeRange(range: SeasonalityRange, minYear: number, maxYear: number): SeasonalityRange {
  if (!Number.isFinite(range.fromYear) || !Number.isFinite(range.toYear)) {
    throw new Error('Invalid year range');
  }

  const fromYear = Math.max(minYear, Math.min(maxYear, Math.round(range.fromYear)));
  const toYear = Math.max(fromYear, Math.min(maxYear, Math.round(range.toYear)));

  return { fromYear, toYear };
}

export function buildSeasonality(rows: readonly DailyClose[]): SeasonalityYear[] {
  const years: SeasonalityYear[] = [];
  const sorted = [...rows].sort((a, b) => a.date.localeCompare(b.date));

  for (const row of sorted) {
    const year = Number(row.date.slice(0, 4));

    let current = years[years.length - 1];

    if (!current || current.year !== year) {
      current = {
        year,
        baselineDate: row.date,
        baselinePrice: row.close,
        points: [],
      };

      years.push(current);
    }

    if (current.points[current.points.length - 1]?.date === row.date) {
      throw new Error(`Multiple daily candles on ${row.date}`);
    }

    const percentage = current.baselinePrice > 0 ? (row.close / current.baselinePrice - 1) * 100 : null;

    if (percentage !== null && !Number.isFinite(percentage)) {
      throw new Error('Invalid percentage');
    }

    current.points.push({
      date: row.date,
      chartDate: `2000-${row.date.slice(5)}`,
      price: row.close,
      percentage,
    });
  }

  return years;
}

export function toSeriesData(year: SeasonalityYear, scale: SeasonalityScale): SeriesDatum[] {
  const isPercentage = scale === PriceScaleMode.Percentage;

  let index = 0;

  return CALENDAR.map((time) => {
    const point = year.points[index];

    if (point?.chartDate !== time) {
      return { time };
    }

    index += 1;

    const value = isPercentage ? point.percentage : point.price;

    return value === null ? { time } : { time, value };
  });
}

export function buildSeasonalityTable(years: readonly SeasonalityYear[]): SeasonalityTableRow[] {
  const closes = new Map<number, number>();

  for (const year of years) {
    for (const point of year.points) {
      const month = Number(point.date.slice(5, 7)) - 1;

      closes.set(year.year * 12 + month, point.price);
    }
  }

  return years.map((year) => {
    const firstMonth = year.year * 12;
    const lastPoint = year.points[year.points.length - 1];
    const baselinePrice = closes.get(firstMonth - 1) ?? year.baselinePrice;

    return {
      year: year.year,
      months: Array.from({ length: 12 }, (_, month) => {
        const key = firstMonth + month;

        return calculateChange(closes.get(key - 1), closes.get(key));
      }),
      total: calculateChange(baselinePrice, lastPoint.price),
    };
  }).reverse();
}

function calculateChange(from: number | undefined, to: number | undefined): SeasonalityChange | null {
  if (from === undefined || to === undefined) {
    return null;
  }

  return {
    absolute: to - from,
    percentage: from > 0 ? (to / from - 1) * 100 : null,
  };
}