import type {
  AssignmentRead,
  AvailabilityRead,
  MatrixResponse,
  PositionCategory,
  ShiftRead,
  Violation,
} from '@/api/schema';
import { t } from '@/i18n';

import { datePart, hoursBetween, naiveMinutes, timePart } from './time';

export function categoryLabel(category: PositionCategory): string {
  return t(`position.category.${category.toLowerCase()}`);
}

// --------------------------------------------------------------------------- //
// Disponibilités : couverture d'un créneau par les fenêtres déclarées         //
// (portage de `backend/app/validation/engine.py`).                            //
// --------------------------------------------------------------------------- //
const _dayNum = (iso: string): number => {
  const [y, m, d] = iso.split('-').map(Number);
  return Math.floor(Date.UTC(y, m - 1, d) / 86_400_000);
};

/** Minutes absolues (depuis une origine arbitraire) d'un datetime naïf ISO. */
function absMinutes(iso: string): number {
  const [date, time] = iso.split('T');
  const [h, min] = time.split(':').map(Number);
  return _dayNum(date) * 1440 + h * 60 + min;
}

function windowInterval(w: AvailabilityRead): [number, number] {
  const [sh, sm] = w.start_time.split(':').map(Number);
  const [eh, em] = w.end_time.split(':').map(Number);
  const start = _dayNum(w.date) * 1440 + sh * 60 + sm;
  let end = _dayNum(w.date) * 1440 + eh * 60 + em;
  if (end <= start) end += 1440; // fenêtre à cheval sur minuit
  return [start, end];
}

/** Minutes du créneau `[startIso, endIso)` hors de l'union des fenêtres. */
export function uncoveredMinutes(
  windows: AvailabilityRead[],
  startIso: string,
  endIso: string,
): number {
  const shiftStart = absMinutes(startIso);
  const shiftEnd = absMinutes(endIso);
  const intervals = windows
    .map(windowInterval)
    .filter(([a, b]) => b > a)
    .sort((a, b) => a[0] - b[0]);
  let cursor = shiftStart;
  let gap = 0;
  for (const [s, e] of intervals) {
    if (e <= cursor) continue;
    if (s > shiftEnd) break;
    if (s > cursor) gap += Math.min(s, shiftEnd) - cursor;
    cursor = Math.max(cursor, e);
    if (cursor >= shiftEnd) return gap;
  }
  if (cursor < shiftEnd) gap += shiftEnd - cursor;
  return gap;
}

export type Coverage = 'full' | 'partial' | 'none';

/** État de couverture d'un créneau par les fenêtres d'un bénévole. */
export function availabilityCoverage(
  windows: AvailabilityRead[],
  startIso: string,
  endIso: string,
): Coverage {
  if (windows.length === 0) return 'none';
  const gap = uncoveredMinutes(windows, startIso, endIso);
  if (gap === 0) return 'full';
  const total = absMinutes(endIso) - absMinutes(startIso);
  return gap >= total ? 'none' : 'partial';
}

/** Colonne de la grille : une (date, heure de début) distincte. */
export interface LatticeColumn {
  key: string; // `YYYY-MM-DD|HH:MM`
  date: string;
  time: string;
}

export interface LatticeDay {
  date: string;
  columns: LatticeColumn[];
}

/** Construit le treillis de colonnes à partir de créneaux (grille alignée). */
export function buildLattice(starts: Array<{ starts_at: string }>): {
  days: LatticeDay[];
  columns: LatticeColumn[];
} {
  const seen = new Map<string, LatticeColumn>();
  for (const s of starts) {
    const date = datePart(s.starts_at);
    const time = timePart(s.starts_at);
    const key = `${date}|${time}`;
    if (!seen.has(key)) seen.set(key, { key, date, time });
  }
  const columns = [...seen.values()].sort((a, b) => a.key.localeCompare(b.key));
  const days: LatticeDay[] = [];
  for (const column of columns) {
    let day = days.find((d) => d.date === column.date);
    if (!day) {
      day = { date: column.date, columns: [] };
      days.push(day);
    }
    day.columns.push(column);
  }
  return { days, columns };
}

export function latticeFromMatrix(matrix: MatrixResponse) {
  return buildLattice(matrix.positions.flatMap((p) => p.shifts.map((s) => ({ starts_at: s.starts_at }))));
}

/** Heures cumulées par bénévole. */
export function hoursByVolunteer(
  assignments: AssignmentRead[],
  shiftsById: Map<string, Pick<ShiftRead, 'starts_at' | 'ends_at'>>,
): Map<string, number> {
  const totals = new Map<string, number>();
  for (const a of assignments) {
    const shift = shiftsById.get(a.shift_id);
    if (!shift) continue;
    totals.set(
      a.volunteer_id,
      (totals.get(a.volunteer_id) ?? 0) + hoursBetween(shift.starts_at, shift.ends_at),
    );
  }
  return totals;
}

/** Surcharge : > 8 h sur une journée civile ou < 8 h de repos entre créneaux. */
export function isOverloaded(
  volunteerId: string,
  assignments: AssignmentRead[],
  shiftsById: Map<string, Pick<ShiftRead, 'starts_at' | 'ends_at'>>,
): boolean {
  const shifts = assignments
    .filter((a) => a.volunteer_id === volunteerId)
    .map((a) => shiftsById.get(a.shift_id))
    .filter((s): s is ShiftRead => Boolean(s))
    .sort((a, b) => a.starts_at.localeCompare(b.starts_at));

  const perDay = new Map<string, number>();
  for (const s of shifts) {
    const day = datePart(s.starts_at);
    perDay.set(day, (perDay.get(day) ?? 0) + hoursBetween(s.starts_at, s.ends_at));
  }
  for (const hours of perDay.values()) if (hours > 8) return true;

  for (let i = 1; i < shifts.length; i += 1) {
    const gap = naiveMinutes(shifts[i].starts_at) - naiveMinutes(shifts[i - 1].ends_at);
    if (gap > 0 && gap < 8 * 60) return true;
  }
  return false;
}

/**
 * Rend une violation en texte lisible. Les `params` suivent exactement le
 * contrat du moteur back-end (`backend/app/validation/engine.py`).
 */
export function violationText(
  violation: Violation,
  resolvePosition?: (shiftId: string) => string | undefined,
): string {
  const p = violation.params;
  switch (violation.code) {
    case 'SHIFT_OVERLAP': {
      const where = resolvePosition?.(String(p.other_shift_id));
      return where
        ? t('validation.SHIFT_OVERLAP.at', { position: where })
        : t('validation.SHIFT_OVERLAP');
    }
    case 'OUTSIDE_AVAILABILITY':
      return t('validation.OUTSIDE_AVAILABILITY', {
        gap: formatMinutes(Number(p.uncovered_minutes)),
      });
    case 'DAILY_HOURS_EXCEEDED':
      return t('validation.DAILY_HOURS_EXCEEDED', {
        hours: formatMinutes(Number(p.total_minutes)),
      });
    case 'INSUFFICIENT_REST':
      return t('validation.INSUFFICIENT_REST', {
        rest: formatMinutes(Number(p.gap_minutes)),
      });
    default:
      return violation.code;
  }
}

function formatMinutes(total: number): string {
  const h = Math.floor(total / 60);
  const m = total % 60;
  return m === 0 ? `${h} h` : `${h} h ${String(m).padStart(2, '0')}`;
}