/**
 * Tests for reactor specificClass (domain logic).
 *
 * Two reactor classes are exported: Reactor_CSTR and Reactor_PFR.
 * Both extend a base Reactor class.
 *
 * Key methods tested:
 *  - _calcOTR: oxygen transfer rate calculation
 *  - _arrayClip2Zero: clip negative values to zero
 *  - setInfluent / getEffluent: influent/effluent data flow
 *  - setOTR: external OTR override
 *  - tick (CSTR): forward Euler state update
 *  - tick (PFR): finite difference state update
 *  - registerChild: dispatches to measurement / reactor handlers
 */

const { Reactor_CSTR, Reactor_PFR } = require('../src/specificClass');

// --------------- helpers ---------------

const NUM_SPECIES = 13;

function makeCSTRConfig(overrides = {}) {
  return {
    general: {
      name: 'TestCSTR',
      id: 'cstr-test-1',
      logging: { enabled: false, logLevel: 'error' },
    },
    functionality: {
      softwareType: 'reactor',
      positionVsParent: 'atEquipment',
    },
    volume: 1000,
    n_inlets: 1,
    kla: 240,
    timeStep: 1,      // 1 second
    initialState: new Array(NUM_SPECIES).fill(1.0),
    ...overrides,
  };
}

function makePFRConfig(overrides = {}) {
  return {
    general: {
      name: 'TestPFR',
      id: 'pfr-test-1',
      logging: { enabled: false, logLevel: 'error' },
    },
    functionality: {
      softwareType: 'reactor',
      positionVsParent: 'atEquipment',
    },
    volume: 200,
    length: 10,
    resolution_L: 10,
    n_inlets: 1,
    kla: 240,
    alpha: 0.5,
    timeStep: 1,
    initialState: new Array(NUM_SPECIES).fill(0.1),
    ...overrides,
  };
}

// --------------- CSTR tests ---------------

describe('Reactor_CSTR', () => {

  describe('constructor / initialization', () => {
    it('should create an instance and set state from initialState', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      expect(r).toBeDefined();
      expect(r.state).toEqual(new Array(NUM_SPECIES).fill(1.0));
    });

    it('should initialize Fs and Cs_in arrays based on n_inlets', () => {
      const r = new Reactor_CSTR(makeCSTRConfig({ n_inlets: 3 }));
      expect(r.Fs).toHaveLength(3);
      expect(r.Cs_in).toHaveLength(3);
      expect(r.Fs.every(v => v === 0)).toBe(true);
    });

    it('should store volume from config', () => {
      const r = new Reactor_CSTR(makeCSTRConfig({ volume: 500 }));
      expect(r.volume).toBe(500);
    });

    it('should initialize temperature to 20', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      expect(r.temperature).toBe(20);
    });
  });

  describe('_calcOTR()', () => {
    let r;
    beforeAll(() => { r = new Reactor_CSTR(makeCSTRConfig({ kla: 240 })); });

    it('should return a positive value when S_O < saturation', () => {
      const otr = r._calcOTR(0, 20);
      expect(otr).toBeGreaterThan(0);
    });

    it('should return approximately zero when S_O equals saturation', () => {
      // S_O_sat at T=20: 14.652 - 4.1022e-1*20 + 7.9910e-3*400 + 7.7774e-5*8000
      const T = 20;
      const S_O_sat = 14.652 - 4.1022e-1 * T + 7.9910e-3 * T * T + 7.7774e-5 * T * T * T;
      const otr = r._calcOTR(S_O_sat, T);
      expect(otr).toBeCloseTo(0, 5);
    });

    it('should return a negative value when S_O > saturation (supersaturated)', () => {
      const otr = r._calcOTR(100, 20);
      expect(otr).toBeLessThan(0);
    });

    it('should use T=20 as default temperature', () => {
      const otr1 = r._calcOTR(0);
      const otr2 = r._calcOTR(0, 20);
      expect(otr1).toBe(otr2);
    });
  });

  describe('_arrayClip2Zero()', () => {
    let r;
    beforeAll(() => { r = new Reactor_CSTR(makeCSTRConfig()); });

    it('should clip negative values to zero', () => {
      expect(r._arrayClip2Zero([-5, 3, -1, 0, 7])).toEqual([0, 3, 0, 0, 7]);
    });

    it('should leave all-positive arrays unchanged', () => {
      expect(r._arrayClip2Zero([1, 2, 3])).toEqual([1, 2, 3]);
    });

    it('should handle nested arrays (2D)', () => {
      const result = r._arrayClip2Zero([[-1, 2], [3, -4]]);
      expect(result).toEqual([[0, 2], [3, 0]]);
    });

    it('should handle a single scalar', () => {
      expect(r._arrayClip2Zero(-5)).toBe(0);
      expect(r._arrayClip2Zero(5)).toBe(5);
    });
  });

  describe('setInfluent / getEffluent', () => {
    it('should store influent data via setter', () => {
      const r = new Reactor_CSTR(makeCSTRConfig({ n_inlets: 2 }));
      const input = {
        payload: {
          inlet: 0,
          F: 100,
          C: new Array(NUM_SPECIES).fill(5),
        },
      };
      r.setInfluent = input;
      expect(r.Fs[0]).toBe(100);
      expect(r.Cs_in[0]).toEqual(new Array(NUM_SPECIES).fill(5));
    });

    it('should return effluent with the sum of Fs and the current state', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      r.Fs[0] = 50;
      const eff = r.getEffluent;
      expect(eff.topic).toBe('Fluent');
      expect(eff.payload.F).toBe(50);
      expect(eff.payload.C).toEqual(r.state);
    });
  });

  describe('setOTR', () => {
    it('should set the OTR value', () => {
      const r = new Reactor_CSTR(makeCSTRConfig({ kla: NaN }));
      r.setOTR = { payload: 42 };
      expect(r.OTR).toBe(42);
    });
  });

  describe('tick()', () => {
    it('should return a new state array of correct length', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      const result = r.tick(0.001);
      expect(result).toHaveLength(NUM_SPECIES);
    });

    it('should not produce NaN values', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      r.Fs[0] = 10;
      r.Cs_in[0] = new Array(NUM_SPECIES).fill(5);
      const result = r.tick(0.001);
      result.forEach(v => expect(Number.isNaN(v)).toBe(false));
    });

    it('should not produce negative concentrations', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      // Run multiple ticks
      for (let i = 0; i < 100; i++) {
        r.tick(0.001);
      }
      r.state.forEach(v => expect(v).toBeGreaterThanOrEqual(0));
    });

    it('should reach steady state with zero flow (concentrations change only via reaction)', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      // No inflow
      const initial = [...r.state];
      r.tick(0.0001);
      // State should have changed due to reaction/OTR
      const changed = r.state.some((v, i) => v !== initial[i]);
      expect(changed).toBe(true);
    });
  });

  describe('registerChild()', () => {
    it('should not throw for "measurement" software type', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      // Passing null child will trigger warn but not crash
      expect(() => r.registerChild(null, 'measurement')).not.toThrow();
    });

    it('should not throw for "reactor" software type', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      expect(() => r.registerChild(null, 'reactor')).not.toThrow();
    });

    it('should not throw for unknown software type', () => {
      const r = new Reactor_CSTR(makeCSTRConfig());
      expect(() => r.registerChild(null, 'unknown')).not.toThrow();
    });
  });
});

// --------------- PFR tests ---------------

describe('Reactor_PFR', () => {

  describe('constructor / initialization', () => {
    it('should create an instance with 2D state grid', () => {
      const r = new Reactor_PFR(makePFRConfig());
      expect(r).toBeDefined();
      expect(r.state).toHaveLength(10); // resolution_L = 10
      expect(r.state[0]).toHaveLength(NUM_SPECIES);
    });

    it('should compute d_x = length / n_x', () => {
      const r = new Reactor_PFR(makePFRConfig({ length: 10, resolution_L: 5 }));
      expect(r.d_x).toBe(2);
    });

    it('should compute cross-sectional area A = volume / length', () => {
      const r = new Reactor_PFR(makePFRConfig({ volume: 200, length: 10 }));
      expect(r.A).toBe(20);
    });

    it('should initialize D (dispersion) to 0', () => {
      const r = new Reactor_PFR(makePFRConfig());
      expect(r.D).toBe(0);
    });

    it('should create derivative operators of correct size', () => {
      const r = new Reactor_PFR(makePFRConfig({ resolution_L: 8 }));
      expect(r.D_op).toHaveLength(8);
      expect(r.D_op[0]).toHaveLength(8);
      expect(r.D2_op).toHaveLength(8);
      expect(r.D2_op[0]).toHaveLength(8);
    });
  });

  describe('setDispersion', () => {
    it('should set the axial dispersion value', () => {
      const r = new Reactor_PFR(makePFRConfig());
      r.setDispersion = { payload: 0.5 };
      expect(r.D).toBe(0.5);
    });
  });

  describe('tick()', () => {
    it('should return a 2D state grid of correct dimensions', () => {
      const r = new Reactor_PFR(makePFRConfig());
      r.D = 0.01;
      const result = r.tick(0.0001);
      expect(result).toHaveLength(10);
      expect(result[0]).toHaveLength(NUM_SPECIES);
    });

    it('should not produce NaN values with small time step and dispersion', () => {
      const r = new Reactor_PFR(makePFRConfig());
      r.D = 0.01;
      r.Fs[0] = 10;
      r.Cs_in[0] = new Array(NUM_SPECIES).fill(5);
      const result = r.tick(0.0001);
      result.forEach(row => {
        row.forEach(v => expect(Number.isNaN(v)).toBe(false));
      });
    });

    it('should not produce negative concentrations', () => {
      const r = new Reactor_PFR(makePFRConfig());
      r.D = 0.01;
      for (let i = 0; i < 10; i++) {
        r.tick(0.0001);
      }
      r.state.forEach(row => {
        row.forEach(v => expect(v).toBeGreaterThanOrEqual(0));
      });
    });
  });

  describe('_applyBoundaryConditions()', () => {
    it('should apply Neumann BC at outlet (last = second to last)', () => {
      const r = new Reactor_PFR(makePFRConfig({ resolution_L: 5 }));
      const state = Array.from({ length: 5 }, () => new Array(NUM_SPECIES).fill(1));
      state[3] = new Array(NUM_SPECIES).fill(7);
      r._applyBoundaryConditions(state);
      // outlet BC: state[4] = state[3]
      expect(state[4]).toEqual(new Array(NUM_SPECIES).fill(7));
    });

    it('should apply Neumann BC at inlet when no flow', () => {
      const r = new Reactor_PFR(makePFRConfig({ resolution_L: 5 }));
      r.Fs[0] = 0;
      const state = Array.from({ length: 5 }, () => new Array(NUM_SPECIES).fill(1));
      state[1] = new Array(NUM_SPECIES).fill(3);
      r._applyBoundaryConditions(state);
      // No flow: state[0] = state[1]
      expect(state[0]).toEqual(new Array(NUM_SPECIES).fill(3));
    });
  });

  describe('_arrayClip2Zero() (inherited)', () => {
    it('should clip 2D arrays correctly', () => {
      const r = new Reactor_PFR(makePFRConfig());
      const result = r._arrayClip2Zero([[-1, 2], [3, -4]]);
      expect(result).toEqual([[0, 2], [3, 0]]);
    });
  });

  describe('_calcOTR() (inherited)', () => {
    it('should work the same as in CSTR', () => {
      const r = new Reactor_PFR(makePFRConfig({ kla: 240 }));
      const otr = r._calcOTR(0, 20);
      expect(otr).toBeGreaterThan(0);
    });
  });
});