import type { QuoteItem } from "@eden/database";

/**
 * Quote pricing/fidelity/approval engine — ported verbatim from eden.md §8
 * (formulas) and §3–§4 (fidelity/discount business rules). These formulas
 * are exact, not approximate — do not "simplify" without an ADR. The
 * backend is always the source of truth (Master Prompt §6.4: "nunca
 * confiar no frontend para cálculo financeiro"); the frontend may mirror
 * this logic for UX, but every quote write recomputes from scratch here.
 */

export interface PricingInput {
  items: QuoteItem[];
  contractPeriod: number;
  fidelityPeriod: number | null;
  implGeral: number;
  proposedMonthlyTotal: number | null;
}

export interface PricingResult {
  monthlyTotal: number;
  implFromProducts: number;
  totalImpl: number;
  hasSpecialPrice: boolean;
  isDiscount: boolean;
  isMarkup: boolean;
  diffMonthly: number;
  effectiveMonthly: number;
  hasReducedFidelity: boolean;
  needsApproval: boolean;
  contractTotal: number;
  /** What to persist to quotes.fidelity_period — null unless it's genuinely a reduced-fidelity exception (eden.md §8 "só persiste se for de fato menor que a faixa"). */
  persistedFidelityPeriod: number | null;
  /** What to persist to quotes.proposed_monthly_total — null unless a special price is actually active. */
  persistedProposedMonthlyTotal: number | null;
}

export function computeQuotePricing(input: PricingInput): PricingResult {
  const monthlyTotal = round2(input.items.reduce((sum, item) => sum + item.total, 0));
  const implFromProducts = round2(input.items.reduce((sum, item) => sum + item.implTotal, 0));
  const totalImpl = round2(implFromProducts + (input.implGeral || 0));

  const proposedMonthly = input.proposedMonthlyTotal;
  const hasSpecialPrice =
    proposedMonthly != null && proposedMonthly > 0 && proposedMonthly !== monthlyTotal;
  const isDiscount = hasSpecialPrice && proposedMonthly! < monthlyTotal;
  const isMarkup = hasSpecialPrice && proposedMonthly! > monthlyTotal;
  const diffMonthly = hasSpecialPrice ? round2(monthlyTotal - proposedMonthly!) : 0;
  const effectiveMonthly = hasSpecialPrice ? proposedMonthly! : monthlyTotal;

  const hasReducedFidelity =
    input.fidelityPeriod != null && input.fidelityPeriod < input.contractPeriod;

  const needsApproval = isDiscount || hasReducedFidelity;

  const contractTotal = round2(effectiveMonthly * (input.contractPeriod || 1) + totalImpl);

  return {
    monthlyTotal,
    implFromProducts,
    totalImpl,
    hasSpecialPrice,
    isDiscount,
    isMarkup,
    diffMonthly,
    effectiveMonthly,
    hasReducedFidelity,
    needsApproval,
    contractTotal,
    persistedFidelityPeriod: hasReducedFidelity ? input.fidelityPeriod : null,
    persistedProposedMonthlyTotal: hasSpecialPrice ? proposedMonthly : null,
  };
}

/**
 * Resolves what `approval_status` should be persisted, given the previous
 * status and whether the actor is submitting an approval decision.
 * Mirrors eden.md §8: `needsApproval ? (approvalStatus === 'none' ?
 * 'pending' : approvalStatus) : 'none'` — but generalized to accept an
 * explicit decision (approve/reject) from a privileged actor, which the
 * legacy handled as a separate code path (§3.3) that this folds in here
 * for a single source of truth.
 */
export function resolveApprovalStatus(
  needsApproval: boolean,
  previousStatus: "none" | "pending" | "approved" | "rejected",
  decision?: "approved" | "rejected",
): "none" | "pending" | "approved" | "rejected" {
  if (!needsApproval) return "none";
  if (decision) return decision;
  return previousStatus === "none" ? "pending" : previousStatus;
}

/** eden.md §3.3: super_admin always; admin only with the explicit per-user flag — never inferred from role alone. */
export function canApproveDiscount(user: { roleKey: string; canApproveDiscount?: boolean }): boolean {
  if (user.roleKey === "super_admin") return true;
  return user.roleKey === "admin" && user.canApproveDiscount === true;
}

/**
 * The fidelity that actually has legal effect (vigência/vencimento/multa)
 * — eden.md §3.4/§10.4, repeated everywhere in the legacy as the single
 * most important rule to preserve: a pending/rejected exception NEVER
 * affects anything legal, only an approved one does.
 */
export function resolveEffectiveFidelity(
  contractPeriod: number,
  fidelityPeriod: number | null,
  approvalStatus: "none" | "pending" | "approved" | "rejected",
): number {
  return fidelityPeriod != null && approvalStatus === "approved" ? fidelityPeriod : contractPeriod || 0;
}

/** eden.md §7 (paymentConditions.js) — progressive by implementation value. */
export const PAYMENT_CONDITIONS = ["À vista", "1+1", "1+2"] as const;

export function getAvailablePaymentConditions(implTotal: number): readonly string[] {
  const value = implTotal || 0;
  if (value <= 1500) return ["À vista"];
  if (value <= 3000) return ["À vista", "1+1"];
  return PAYMENT_CONDITIONS;
}

export interface SavingsResult {
  totalDescontoMensal: number;
  totalEconomiaMensal: number;
  economiaTotalContrato: number;
  beneficioTotalFidelidade: number;
}

/**
 * eden.md §3.5/§4.4 — two DIFFERENT numbers that must never be confused:
 * `beneficioTotalFidelidade` (fidelity discount only, used as the legal
 * cap for the RGC art. 37 early-termination penalty) vs.
 * `totalEconomiaMensal`/`economiaTotalContrato` (fidelity + special
 * discount combined, shown as commercial "savings" info to the client).
 */
export function computeSavings(
  items: QuoteItem[],
  contractPeriod: number,
  effectiveFidelityPeriod: number,
  monthlyTotal: number,
  proposedMonthlyTotal: number | null,
): SavingsResult {
  const totalDescontoMensal = round2(
    items.reduce((sum, item) => sum + ((item.price0 ?? 0) - item.unitPrice) * item.quantity, 0),
  );
  const hasSpecialPrice =
    proposedMonthlyTotal != null && proposedMonthlyTotal > 0 && proposedMonthlyTotal !== monthlyTotal;
  const specialDiscount = hasSpecialPrice ? round2(monthlyTotal - proposedMonthlyTotal!) : 0;
  const totalEconomiaMensal = round2(totalDescontoMensal + specialDiscount);
  const economiaTotalContrato =
    totalEconomiaMensal > 0 && contractPeriod > 0 ? round2(totalEconomiaMensal * contractPeriod) : 0;
  const beneficioTotalFidelidade = round2(totalDescontoMensal * effectiveFidelityPeriod);

  return { totalDescontoMensal, totalEconomiaMensal, economiaTotalContrato, beneficioTotalFidelidade };
}

function round2(value: number): number {
  return Math.round((value + Number.EPSILON) * 100) / 100;
}