/**
 * Presentation rules shared by the authority's dashboards (the vessel
 * register report and the seafarer services report).
 *
 * Kept here rather than in either feature folder because the two screens are
 * meant to read as one product: the same em dash for "no answer", the same
 * palette assigned in the same order, the same muted treatment for the
 * bookkeeping slices. Two copies would drift the first time one of them gained
 * a colour.
 *
 * Nothing in this file knows what a vessel or a seafarer is — the
 * domain-specific labels stay in each feature's own `report-format.ts`, which
 * re-exports this module so a component has one import.
 */

import { ethMonthName, toEthDateTime } from '@ema-platform/shared';

/** One slice of a breakdown chart, as every report's API returns it. */
export interface ReportBreakdownItem {
  key: string;
  label: string;
  count: number;
  percentage: number;
}

/** Nothing measurable is not zero — an em dash says so without lying. */
export const DASH = '—';

/**
 * A figure the API may legitimately have no answer for.
 *
 * An average is null on an empty register and a rate is null until something
 * has been decided; rendering either as 0 would report a fleet that weighs
 * nothing and a service that approves nobody.
 */
export function formatNumber(
  value: number | null | undefined,
  options: { decimals?: number; suffix?: string } = {},
): string {
  if (value === null || value === undefined || Number.isNaN(value)) return DASH;
  const text = value.toLocaleString(undefined, {
    minimumFractionDigits: options.decimals ?? 0,
    maximumFractionDigits: options.decimals ?? 0,
  });
  return options.suffix ? `${text}${options.suffix}` : text;
}

export function formatPercent(value: number | null | undefined): string {
  return value === null || value === undefined
    ? DASH
    : `${formatNumber(value, { decimals: 1 })}%`;
}

export function formatMoney(value: number, currency: string): string {
  return `${formatNumber(value, { decimals: 2 })} ${currency}`;
}

/** A signed delta for the change-vs-previous chip. */
export function formatDelta(value: number | null): string {
  if (value === null) return DASH;
  const sign = value > 0 ? '+' : '';
  return `${sign}${formatNumber(value, { decimals: 1 })}%`;
}

export function deltaColor(value: number | null): string {
  if (value === null || value === 0) return 'gray';
  return value > 0 ? 'teal' : 'red';
}

/**
 * Days as a readable duration.
 *
 * Sea time and processing times are both days on the wire, but "487 d" is not
 * a figure anyone reads as "a year and four months", which is the unit
 * certificate eligibility is argued in.
 */
export function formatDays(value: number | null | undefined): string {
  if (value === null || value === undefined || Number.isNaN(value)) return DASH;
  if (value < 31) return `${formatNumber(value)} d`;
  if (value < 365) return `${formatNumber(value / 30.44, { decimals: 1 })} mo`;
  return `${formatNumber(value / 365.25, { decimals: 1 })} yr`;
}

/** Cumulative expiry counts, as the disjoint bands a chart can stack. */
export interface CumulativeExpiry {
  expiringIn30: number;
  expiringIn60: number;
  expiringIn90: number;
}

/**
 * An API's expiry counts are cumulative — a certificate due in eleven days is
 * inside the 30-, 60- and 90-day figures, which is how a renewals desk reads
 * them. Stacked side by side in a chart that reads as three separate groups,
 * so they are differenced into disjoint bands first.
 */
export function expiryBands(
  counts: CumulativeExpiry,
): Array<{ label: string; count: number }> {
  const { expiringIn30, expiringIn60, expiringIn90 } = counts;
  return [
    { label: 'Within 30 days', count: expiringIn30 },
    // Math.max guards against a server that ever answers non-monotonically —
    // a negative bar is worse than a zero one.
    { label: '31–60 days', count: Math.max(0, expiringIn60 - expiringIn30) },
    { label: '61–90 days', count: Math.max(0, expiringIn90 - expiringIn60) },
  ];
}

/** Red inside a week, orange inside a month, otherwise unremarkable. */
export function expiryUrgency(daysToExpiry: number): string {
  if (daysToExpiry <= 7) return 'red';
  if (daysToExpiry <= 30) return 'orange';
  return 'gray';
}

/**
 * Officer ids are IAM uuids, which make useless axis labels. Until the
 * dashboards have a name lookup, shorten them and keep "UNASSIGNED" readable.
 */
export function officerLabel(key: string): string {
  if (key === 'UNASSIGNED') return 'Unassigned';
  return key.length > 8 ? `${key.slice(0, 8)}…` : key;
}

/**
 * Chart colours, assigned by position so a slice keeps its colour between
 * renders. Mantine's palette rather than invented hex codes, so the charts
 * follow the theme the rest of the app is built on.
 */
const PALETTE = [
  'var(--mantine-color-blue-6)',
  'var(--mantine-color-teal-6)',
  'var(--mantine-color-orange-6)',
  'var(--mantine-color-grape-6)',
  'var(--mantine-color-cyan-6)',
  'var(--mantine-color-lime-7)',
  'var(--mantine-color-pink-6)',
  'var(--mantine-color-indigo-6)',
];

const MUTED = 'var(--mantine-color-gray-5)';

/**
 * "Unknown" and "Other" are bookkeeping slices rather than findings, so they
 * always take the muted colour instead of competing with the real categories
 * for one of the bright ones.
 */
export function sliceColor(item: ReportBreakdownItem, index: number): string {
  if (item.key === 'OTHER' || item.key === 'Unknown') return MUTED;
  return PALETTE[index % PALETTE.length];
}

/**
 * Bucket keys are ISO dates; the axis wants something a human reads.
 *
 * Under Amharic the tick is the Ethiopian month (and day), the way every other
 * date in the app already renders through `dateDisplayer` — a chart whose axis
 * says "Sep 2026" beside a table that says "መስከረም 2019" is two calendars on one
 * screen. Bucket keys are UTC midnights, so the day is embedded at UTC noon
 * first: `toEthDateTime` reads local Y/M/D, and in a positive-offset timezone
 * a UTC midnight is still the previous local day.
 */
export function formatBucket(
  bucket: string,
  granularity: 'DAY' | 'WEEK' | 'MONTH',
  language = 'en',
): string {
  const date = new Date(bucket);
  if (Number.isNaN(date.getTime())) return bucket;
  if (language.startsWith('am')) {
    const local = new Date(
      date.getUTCFullYear(),
      date.getUTCMonth(),
      date.getUTCDate(),
      12,
    );
    const eth = toEthDateTime(local);
    const month = ethMonthName(local);
    return granularity === 'MONTH'
      ? `${month} ${eth.year}`
      : `${month} ${eth.date}`;
  }
  if (granularity === 'MONTH') {
    return date.toLocaleDateString(undefined, {
      month: 'short',
      year: 'numeric',
      timeZone: 'UTC',
    });
  }
  return date.toLocaleDateString(undefined, {
    day: 'numeric',
    month: 'short',
    timeZone: 'UTC',
  });
}

/** The default window the APIs apply when none is given: the last 12 months. */
export function defaultRange(now: Date): [Date, Date] {
  const from = new Date(
    Date.UTC(now.getUTCFullYear() - 1, now.getUTCMonth(), now.getUTCDate()),
  );
  return [from, now];
}

export const ISO_DAY_LENGTH = 10;

export const toIsoDay = (date: Date): string =>
  date.toISOString().slice(0, ISO_DAY_LENGTH);

/**
 * The filter state as URL search params, so a filtered dashboard is a
 * shareable link rather than something the next person has to rebuild.
 *
 * Empty arrays and blank strings are dropped rather than serialised, which
 * keeps an untouched dashboard's URL clean and lets the API apply its own
 * defaults instead of being handed an empty filter to honour.
 */
export function queryToSearchParams(query: object): URLSearchParams {
  const params = new URLSearchParams();
  for (const [key, value] of Object.entries(query)) {
    if (value === undefined || value === null || value === '') continue;
    if (Array.isArray(value)) {
      if (value.length === 0) continue;
      params.set(key, value.join(','));
    } else {
      params.set(key, String(value));
    }
  }
  return params;
}

/**
 * The inverse, for restoring state from a shared link.
 *
 * The key lists are the caller's, because they are the report's filter
 * contract: a key this report does not understand is dropped rather than
 * forwarded to fail the API's validation pipe.
 */
export function searchParamsToQuery<T>(
  params: URLSearchParams,
  keys: {
    arrays: readonly string[];
    numbers: readonly string[];
    strings: readonly string[];
  },
): T {
  const query: Record<string, unknown> = {};
  for (const key of keys.arrays) {
    const raw = params.get(key);
    if (raw) query[key] = raw.split(',').filter(Boolean);
  }
  for (const key of keys.numbers) {
    const raw = params.get(key);
    // An unparseable number in a hand-edited URL is ignored rather than sent
    // on to fail the API's validation pipe.
    if (raw !== null && raw !== '' && Number.isFinite(Number(raw))) {
      query[key] = Number(raw);
    }
  }
  for (const key of keys.strings) {
    const raw = params.get(key);
    if (raw) query[key] = raw;
  }
  const granularity = params.get('granularity');
  if (granularity === 'DAY' || granularity === 'WEEK' || granularity === 'MONTH') {
    query.granularity = granularity;
  }
  return query as T;
}

/**
 * The multi-select options a filter offers, taken from the breakdown the last
 * response carried — there is no lookup endpoint for flag states, ports or
 * nationalities, and the register is the only place that knows which ones are
 * in use.
 *
 * "Unknown" is dropped: it stands for a missing value, and there is nothing to
 * filter the register down to.
 */
export function optionsFrom(items: ReportBreakdownItem[] | undefined): string[] {
  return (items ?? [])
    .filter((item) => item.key !== 'Unknown' && item.key !== 'OTHER')
    .map((item) => item.key);
}