// server/lib/scheduling.ts
// Disponibilidad + scoring de especialistas. Las funciones puras de aquí
// se unit-testean en scheduling.test.ts; las que tocan la DB se añaden más abajo.

export interface WorkingDay { start: string; end: string; } // "HH:mm"
export type WorkingHoursMap = Record<number, WorkingDay | null>; // 1=Lun … 7=Dom

export interface BusyWindow { startMs: number; endMs: number; }
export interface ScoreInput {
  specialtyMatch: number; // 0..1
  efficiency: number;     // 0..1
  loadBalance: number;    // 0..1 (fracción de jornada ocupada)
}

export function clamp01(n: number): number {
  return Math.max(0, Math.min(1, n));
}

export function parseWorkingHours(json: string | null | undefined): WorkingHoursMap | null {
  if (!json) return null;
  try {
    const obj = JSON.parse(json);
    if (typeof obj !== "object" || obj === null) return null;
    const out: WorkingHoursMap = {};
    for (let d = 1; d <= 7; d++) {
      const v = obj[String(d)];
      if (v && typeof v.start === "string" && typeof v.end === "string") out[d] = { start: v.start, end: v.end };
      else out[d] = null;
    }
    return out;
  } catch {
    return null;
  }
}

/** JS getDay(): 0=Dom..6=Sáb → ISO 1=Lun..7=Dom. */
export function isoDayOfWeek(date: Date): number {
  const j = date.getDay();
  return j === 0 ? 7 : j;
}

export function isoDateStr(d: Date): string {
  const pad = (n: number) => String(n).padStart(2, "0");
  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
}

/** Resuelve el horario (empleado tiene prioridad; si no, negocio) para esa fecha. Devuelve ms o null si es día cerrado. */
export function getWorkingHoursForDate(
  empWh: WorkingHoursMap | null,
  bizWh: WorkingHoursMap | null,
  date: Date
): { startMs: number; endMs: number } | null {
  const dow = isoDayOfWeek(date);
  const day = empWh?.[dow] ?? bizWh?.[dow] ?? null;
  if (!day) return null;
  const [sh, sm] = day.start.split(":").map(Number);
  const [eh, em] = day.end.split(":").map(Number);
  const startMs = new Date(date.getFullYear(), date.getMonth(), date.getDate(), sh, sm).getTime();
  const endMs = new Date(date.getFullYear(), date.getMonth(), date.getDate(), eh, em).getTime();
  if (!isFinite(startMs) || !isFinite(endMs) || endMs <= startMs) return null;
  return { startMs, endMs };
}

export function normalizeText(s: string): string {
  return (s || "").toLowerCase().normalize("NFD").replace(/[\u0300-\u036f]/g, "").trim();
}

export function tokens(s: string): string[] {
  return normalizeText(s).split(/[^a-z0-9]+/).filter(Boolean);
}

/**
 * 1.0 si una especialidad coincide con la categoría o un token del nombre del servicio.
 * 0.5 si no hay etiquetas o no coincide (el caller ya garantiza que ofrece el servicio).
 */
export function specialtyMatch(specialties: string[], service: { name: string; category: string }): number {
  if (!specialties || specialties.length === 0) return 0.5;
  const catN = normalizeText(service.category);
  const nameTokens = tokens(service.name);
  const hay = new Set<string>([catN, ...nameTokens]);
  for (const sp of specialties) {
    const spn = normalizeText(sp);
    if (!spn) continue;
    if (hay.has(spn)) return 1;
    if (catN && (catN.includes(spn) || spn.includes(catN))) return 1;
    for (const t of nameTokens) {
      if (t.length >= 4 && (t.includes(spn) || spn.includes(t))) return 1;
    }
  }
  return 0.5;
}

export function overlaps(aStart: number, aEnd: number, bStart: number, bEnd: number): boolean {
  return aStart < bEnd && aEnd > bStart;
}

export function hasConflict(existing: BusyWindow[], startMs: number, endMs: number): boolean {
  return existing.some((b) => overlaps(startMs, endMs, b.startMs, b.endMs));
}

/** score = 50·specialtyMatch + 30·efficiency + 20·(1−loadBalance), todo en [0,1]. Rango 0..100. */
export function scoreCandidate(s: ScoreInput): number {
  const sm = clamp01(s.specialtyMatch);
  const eff = clamp01(s.efficiency);
  const inv = clamp01(1 - clamp01(s.loadBalance));
  return 50 * sm + 30 * eff + 20 * inv;
}

import type { DatabaseSync } from "node:sqlite";

export interface CandidateInfo {
  id: number;
  name: string;
  color: string;
  role: string;
  specialties: string[];
  efficiency_score: number;
  empWh: WorkingHoursMap | null;
}

function safeArr(json: unknown): string[] {
  if (typeof json !== "string" || !json) return [];
  try {
    const a = JSON.parse(json);
    return Array.isArray(a) ? a.map(String) : [];
  } catch {
    return [];
  }
}

export function getCandidates(db: DatabaseSync, businessId: number, serviceId: number): CandidateInfo[] {
  const rows = db
    .prepare(
      `SELECT e.id, e.name, e.color, e.role, e.specialties, e.working_hours wh, e.efficiency_score
       FROM employees e
       JOIN employee_services es ON es.employee_id = e.id
       WHERE e.business_id = ? AND es.service_id = ? AND e.active = 1`
    )
    .all(businessId, serviceId) as any[];
  return rows.map((r) => ({
    id: r.id,
    name: r.name,
    color: r.color,
    role: r.role,
    specialties: safeArr(r.specialties),
    efficiency_score: typeof r.efficiency_score === "number" ? r.efficiency_score : 50,
    empWh: parseWorkingHours(r.wh),
  }));
}

export function getExistingBusy(db: DatabaseSync, employeeIds: number[], dateIso: string): Map<number, BusyWindow[]> {
  const map = new Map<number, BusyWindow[]>();
  if (employeeIds.length === 0) return map;
  const startOfDay = `${dateIso}T00:00:00`;
  const endOfDay = `${dateIso}T23:59:59`;
  const rows = db
    .prepare(
      `SELECT employee_id, start_at, end_at FROM appointments
       WHERE employee_id IN (${employeeIds.map(() => "?").join(",")})
         AND status IN ('scheduled','completed') AND start_at >= ? AND start_at <= ?`
    )
    .all(...employeeIds, startOfDay, endOfDay) as any[];
  for (const r of rows) {
    const arr = map.get(r.employee_id) ?? [];
    arr.push({ startMs: new Date(r.start_at).getTime(), endMs: new Date(r.end_at).getTime() });
    map.set(r.employee_id, arr);
  }
  return map;
}

export function isAvailable(db: DatabaseSync, employeeId: number, startMs: number, endMs: number): boolean {
  const dateIso = isoDateStr(new Date(startMs));
  const busy = getExistingBusy(db, [employeeId], dateIso).get(employeeId) ?? [];
  return !hasConflict(busy, startMs, endMs);
}

interface RankedCandidate { info: CandidateInfo; score: number; reasons: string[] }

function rankOne(
  c: CandidateInfo,
  busy: BusyWindow[],
  wh: { startMs: number; endMs: number },
  service: { name: string; category: string }
): RankedCandidate | null {
  const workingMs = Math.max(1, wh.endMs - wh.startMs);
  let occupiedMs = 0;
  for (const b of busy) {
    occupiedMs += Math.min(b.endMs, wh.endMs) - Math.max(b.startMs, wh.startMs);
    if (occupiedMs < 0) occupiedMs = 0;
  }
  const loadBalance = clamp01(occupiedMs / workingMs);
  const sm = specialtyMatch(c.specialties, service);
  const score = scoreCandidate({ specialtyMatch: sm, efficiency: c.efficiency_score / 100, loadBalance });
  const reasons: string[] = [];
  if (sm >= 1) reasons.push("Especialidad coincidente");
  if (c.efficiency_score >= 75) reasons.push("Alta eficiencia");
  if (loadBalance <= 0.25) reasons.push("Buena disponibilidad");
  return { info: c, score, reasons };
}

/** Usado por el endpoint de slots: devuelve el mejor candidato libre para un slot concreto. */
export function pickBestSlotEmployee(
  candidates: CandidateInfo[],
  busyMap: Map<number, BusyWindow[]>,
  bizWh: WorkingHoursMap | null,
  service: { name: string; category: string },
  startMs: number,
  endMs: number
): { id: number; name: string } | null {
  const date = new Date(startMs);
  let best: { id: number; name: string; score: number } | null = null;
  for (const c of candidates) {
    const wh = getWorkingHoursForDate(c.empWh, bizWh, date);
    if (!wh) continue;
    if (startMs < wh.startMs || endMs > wh.endMs) continue;
    if (hasConflict(busyMap.get(c.id) ?? [], startMs, endMs)) continue;
    const ranked = rankOne(c, busyMap.get(c.id) ?? [], wh, service);
    if (!ranked) continue;
    if (!best || ranked.score > best.score || (ranked.score === best.score && c.id < best.id)) {
      best = { id: c.id, name: c.name, score: ranked.score };
    }
  }
  return best ? { id: best.id, name: best.name } : null;
}

export interface AutoAssignResult {
  employeeId: number;
  score: number;
  reasons: string[];
}

export interface AutoAssignCtx {
  businessId: number;
  serviceId: number;
  serviceName: string;
  serviceCategory: string;
  startMs: number;
  endMs: number;
  bizWh: WorkingHoursMap | null;
}

/** Asigna el mejor especialista disponible (hard constraints + score). Llamar dentro de transacción. */
export function autoAssign(db: DatabaseSync, ctx: AutoAssignCtx): AutoAssignResult | null {
  const candidates = getCandidates(db, ctx.businessId, ctx.serviceId);
  if (candidates.length === 0) return null;
  const dateIso = isoDateStr(new Date(ctx.startMs));
  const busyMap = getExistingBusy(db, candidates.map((c) => c.id), dateIso);
  let best: RankedCandidate | null = null;
  for (const c of candidates) {
    const wh = getWorkingHoursForDate(c.empWh, ctx.bizWh, new Date(ctx.startMs));
    if (!wh) continue;
    if (ctx.startMs < wh.startMs || ctx.endMs > wh.endMs) continue;
    if (hasConflict(busyMap.get(c.id) ?? [], ctx.startMs, ctx.endMs)) continue;
    const ranked = rankOne(c, busyMap.get(c.id) ?? [], wh, { name: ctx.serviceName, category: ctx.serviceCategory });
    if (!ranked) continue;
    if (!best || ranked.score > best.score || (ranked.score === best.score && c.id < best.info.id)) {
      best = ranked;
    }
  }
  if (!best) return null;
  return {
    employeeId: best.info.id,
    score: best.score,
    reasons: best.reasons.length ? best.reasons : ["Disponible"],
  };
}

/** Ejecuta fn dentro de una transacción BEGIN IMMEDIATE…COMMIT; ROLLBACK en error. */
export function runInTransaction<T>(db: DatabaseSync, fn: () => T): T {
  db.exec("BEGIN IMMEDIATE");
  try {
    const r = fn();
    db.exec("COMMIT");
    return r;
  } catch (err) {
    try { db.exec("ROLLBACK"); } catch { /* ignore */ }
    throw err;
  }
}