/**
 * Inventory System Tests — Phase 4.2
 *
 * Weight-based inventory with element stacking,
 * mass limits, and slot limits.
 */

import { describe, it, expect } from 'vitest';
import { Inventory, getItemMass } from '../src/player/inventory';

// === Item Mass Lookup ===

describe('getItemMass', () => {
  it('returns atomic mass for elements', () => {
    expect(getItemMass('H')).toBeCloseTo(1.008);
    expect(getItemMass('Na')).toBeCloseTo(22.99);
    expect(getItemMass('Fe')).toBeCloseTo(55.845);
    expect(getItemMass('O')).toBeCloseTo(15.999);
  });

  it('returns molecular mass for compounds', () => {
    expect(getItemMass('NaCl')).toBeCloseTo(58.44);
    expect(getItemMass('H2O')).toBeCloseTo(18.015);
    expect(getItemMass('CO2')).toBeCloseTo(44.01);
  });

  it('returns 0 for unknown items', () => {
    expect(getItemMass('UNKNOWN')).toBe(0);
    expect(getItemMass('')).toBe(0);
  });
});

// === Inventory Core ===

describe('Inventory — creation', () => {
  it('starts empty', () => {
    const inv = new Inventory();
    expect(inv.isEmpty()).toBe(true);
    expect(inv.getItems()).toEqual([]);
    expect(inv.getTotalWeight()).toBe(0);
    expect(inv.slotCount).toBe(0);
  });

  it('respects custom limits', () => {
    const inv = new Inventory(100, 5);
    expect(inv.maxWeight).toBe(100);
    expect(inv.maxSlots).toBe(5);
  });
});

describe('Inventory — adding items', () => {
  it('adds elements', () => {
    const inv = new Inventory();
    const added = inv.addItem('H', 3);
    expect(added).toBe(3);
    expect(inv.getCount('H')).toBe(3);
    expect(inv.isEmpty()).toBe(false);
    expect(inv.slotCount).toBe(1);
  });

  it('adds compounds', () => {
    const inv = new Inventory();
    const added = inv.addItem('NaCl', 1);
    expect(added).toBe(1);
    expect(inv.getCount('NaCl')).toBe(1);
  });

  it('stacks same elements', () => {
    const inv = new Inventory();
    inv.addItem('Na', 2);
    inv.addItem('Na', 3);
    expect(inv.getCount('Na')).toBe(5);
    expect(inv.slotCount).toBe(1);
  });

  it('stacking does not consume new slot', () => {
    const inv = new Inventory(10000, 3);
    inv.addItem('H', 1);
    inv.addItem('O', 1);
    inv.addItem('Na', 1);
    const added = inv.addItem('H', 5);
    expect(added).toBe(5);
    expect(inv.getCount('H')).toBe(6);
    expect(inv.slotCount).toBe(3);
  });

  it('returns 0 for unknown items', () => {
    const inv = new Inventory();
    expect(inv.addItem('UNKNOWN', 1)).toBe(0);
    expect(inv.isEmpty()).toBe(true);
  });

  it('returns 0 for zero/negative count', () => {
    const inv = new Inventory();
    expect(inv.addItem('H', 0)).toBe(0);
    expect(inv.addItem('H', -1)).toBe(0);
  });
});

describe('Inventory — removing items', () => {
  it('removes items', () => {
    const inv = new Inventory();
    inv.addItem('H', 5);
    const removed = inv.removeItem('H', 3);
    expect(removed).toBe(3);
    expect(inv.getCount('H')).toBe(2);
  });

  it('cleans up slot when count reaches zero', () => {
    const inv = new Inventory();
    inv.addItem('H', 3);
    inv.removeItem('H', 3);
    expect(inv.getCount('H')).toBe(0);
    expect(inv.slotCount).toBe(0);
    expect(inv.isEmpty()).toBe(true);
  });

  it('removes only what is available', () => {
    const inv = new Inventory();
    inv.addItem('H', 2);
    const removed = inv.removeItem('H', 5);
    expect(removed).toBe(2);
    expect(inv.getCount('H')).toBe(0);
  });

  it('returns 0 for non-existent item', () => {
    const inv = new Inventory();
    expect(inv.removeItem('H', 1)).toBe(0);
  });

  it('returns 0 for zero/negative count', () => {
    const inv = new Inventory();
    inv.addItem('H', 5);
    expect(inv.removeItem('H', 0)).toBe(0);
    expect(inv.removeItem('H', -1)).toBe(0);
  });
});

describe('Inventory — weight system', () => {
  it('calculates total weight from atomic masses', () => {
    const inv = new Inventory();
    inv.addItem('Na', 2); // 22.99 * 2 = 45.98
    expect(inv.getTotalWeight()).toBeCloseTo(22.99 * 2);
  });

  it('calculates mixed element + compound weight', () => {
    const inv = new Inventory();
    inv.addItem('Na', 1); // 22.99
    inv.addItem('NaCl', 1); // 58.44
    expect(inv.getTotalWeight()).toBeCloseTo(22.99 + 58.44);
  });

  it('limits additions by weight', () => {
    const inv = new Inventory(100); // 100 AMU limit
    // Na mass = 22.99 → max 4 fit (4 * 22.99 = 91.96)
    const added = inv.addItem('Na', 10);
    expect(added).toBe(4);
    expect(inv.getCount('Na')).toBe(4);
    expect(inv.getTotalWeight()).toBeCloseTo(22.99 * 4);
  });

  it('weight frees up after removal', () => {
    const inv = new Inventory(100);
    inv.addItem('Na', 4); // 91.96
    inv.removeItem('Na', 2); // now 45.98 used, ~54 free
    const added = inv.addItem('Na', 3); // 2 more fit (45.98 + 2*22.99 = 91.96)
    expect(added).toBe(2);
    expect(inv.getCount('Na')).toBe(4);
  });

  it('getItemWeight returns stack weight', () => {
    const inv = new Inventory();
    inv.addItem('Na', 3);
    expect(inv.getItemWeight('Na')).toBeCloseTo(22.99 * 3);
  });

  it('getItemWeight returns 0 for absent item', () => {
    const inv = new Inventory();
    expect(inv.getItemWeight('H')).toBe(0);
  });
});

describe('Inventory — slot limits', () => {
  it('respects max slots', () => {
    const inv = new Inventory(10000, 3);
    inv.addItem('H', 1);
    inv.addItem('O', 1);
    inv.addItem('Na', 1);
    const added = inv.addItem('Fe', 1); // 4th slot
    expect(added).toBe(0);
    expect(inv.slotCount).toBe(3);
    expect(inv.hasItem('Fe')).toBe(false);
  });

  it('frees slot after full removal', () => {
    const inv = new Inventory(10000, 2);
    inv.addItem('H', 1);
    inv.addItem('O', 1);
    expect(inv.addItem('Na', 1)).toBe(0); // full
    inv.removeItem('O', 1); // free a slot
    expect(inv.addItem('Na', 1)).toBe(1); // now fits
    expect(inv.slotCount).toBe(2);
  });
});

describe('Inventory — queries', () => {
  it('hasItem checks against count', () => {
    const inv = new Inventory();
    inv.addItem('H', 3);
    expect(inv.hasItem('H', 1)).toBe(true);
    expect(inv.hasItem('H', 3)).toBe(true);
    expect(inv.hasItem('H', 4)).toBe(false);
    expect(inv.hasItem('O')).toBe(false);
  });

  it('getItems returns all items', () => {
    const inv = new Inventory();
    inv.addItem('H', 3);
    inv.addItem('Na', 2);
    const items = inv.getItems();
    expect(items).toHaveLength(2);
    expect(items).toContainEqual({ id: 'H', count: 3 });
    expect(items).toContainEqual({ id: 'Na', count: 2 });
  });

  it('getCount returns 0 for absent item', () => {
    const inv = new Inventory();
    expect(inv.getCount('H')).toBe(0);
  });
});

describe('Inventory — clear', () => {
  it('removes everything', () => {
    const inv = new Inventory();
    inv.addItem('H', 3);
    inv.addItem('Na', 2);
    inv.addItem('NaCl', 1);
    inv.clear();
    expect(inv.isEmpty()).toBe(true);
    expect(inv.getTotalWeight()).toBe(0);
    expect(inv.slotCount).toBe(0);
    expect(inv.getItems()).toEqual([]);
  });
});