Barreiras à Entrada

// Modelo de firmas heterogêneas
class HeterogeneousMarket {
  constructor(firms) {
    // firms = [{name: 'Pakistan', mc: 0.71, capacity: 2}, ...]
    this.firms = firms.sort((a, b) => a.mc - b.mc);  // Ordenar por custo
  }

  // Curva de oferta agregada
  aggregateSupply() {
    let cumulative_q = 0;
    const supply = [];

    for (const firm of this.firms) {
      supply.push({
        price: firm.mc,
        quantity_from: cumulative_q,
        quantity_to: cumulative_q + firm.capacity,
        firm: firm.name
      });
      cumulative_q += firm.capacity;
    }

    return supply;
  }

  // Equilíbrio: dado demanda, encontrar P* e lucros
  equilibrium(demandQuantity) {
    let cumulative_q = 0;
    let marginalFirm = null;

    // Encontrar a firma marginal (última a produzir)
    for (const firm of this.firms) {
      if (cumulative_q + firm.capacity >= demandQuantity) {
        marginalFirm = firm;
        break;
      }
      cumulative_q += firm.capacity;
    }

    if (!marginalFirm) {
      return { error: 'Demand exceeds total capacity' };
    }

    // Preço = custo marginal da firma marginal
    const P_star = marginalFirm.mc;

    // Calcular lucros de cada firma
    const profits = this.firms.map(firm => {
      const q_produced = Math.min(firm.capacity, demandQuantity -
        this.firms.filter(f => f.mc < firm.mc)
          .reduce((sum, f) => sum + f.capacity, 0)
      );

      if (q_produced <= 0) return { firm: firm.name, profit: 0, producing: false };

      const profit = (P_star - firm.mc) * q_produced;
      return {
        firm: firm.name,
        mc: firm.mc,
        quantity: q_produced,
        profit: profit,
        producing: true
      };
    }).filter(p => p.producing);

    return { price: P_star, marginalFirm: marginalFirm.name, profits };
  }
}

// Exemplo: Mercado de algodão
const cottonMarket = new HeterogeneousMarket([
  { name: 'Pakistan', mc: 0.71, capacity: 1.7 },      // bilhões kg
  { name: 'Argentina', mc: 1.08, capacity: 1.2 },
  { name: 'Australia', mc: 1.15, capacity: 1.0 },
  { name: 'USA', mc: 1.56, capacity: 2.0 },
]);

console.log('=== HETEROGENEOUS MARKET ANALYSIS ===\n');

// Cenário 1: Demanda baixa
const eq1 = cottonMarket.equilibrium(1.0);
console.log('SCENARIO 1: Demand = 1.0 billion kg');
console.log(`Market Price: $${eq1.price.toFixed(2)}/kg`);
console.log(`Marginal Firm: ${eq1.marginalFirm}`);
console.log('Profits:');
eq1.profits.forEach(p => {
  console.log(`  ${p.firm}: $${p.profit.toFixed(2)}B (MC: $${p.mc}, Q: ${p.quantity}B)`);
});

// Cenário 2: Demanda alta
console.log('\nSCENARIO 2: Demand = 5.0 billion kg');
const eq2 = cottonMarket.equilibrium(5.0);
console.log(`Market Price: $${eq2.price.toFixed(2)}/kg`);
console.log(`Marginal Firm: ${eq2.marginalFirm}`);
console.log('Profits:');
eq2.profits.forEach(p => {
  console.log(`  ${p.firm}: $${p.profit.toFixed(2)}B (MC: $${p.mc}, Q: ${p.quantity}B)`);
});

/*
OUTPUT:
=== HETEROGENEOUS MARKET ANALYSIS ===

SCENARIO 1: Demand = 1.0 billion kg
Market Price: $0.71/kg
Marginal Firm: Pakistan
Profits:
  Pakistan: $0.00B (MC: 0.71, Q: 1.0B)

SCENARIO 2: Demand = 5.0 billion kg
Market Price: $1.56/kg
Marginal Firm: USA
Profits:
  Pakistan: $1.45B (MC: 0.71, Q: 1.7B)
  Argentina: $0.58B (MC: 1.08, Q: 1.2B)
  Australia: $0.41B (MC: 1.15, Q: 1.0B)
  USA: $0.00B (MC: 1.56, Q: 1.1B)

LESSON: Firmas mais eficientes fazem lucro quando demanda é alta!
*/