//! T-CYCLE-01: Simple Refrigeration Cycle — R134a
//!
//! Tests a standard vapor-compression cycle using CoolProp for real fluid properties.
//! Reference: ASHRAE Handbook — Fundamentals, Chapter 2
//!
//! Cycle: Compressor → Condenser → TXV → Evaporator
//!
//! Operating conditions:
//!     T_evap_sat = 0°C,  T_cond_sat = 40°C
//!     Superheat  = 5 K,   Subcooling  = 3 K
//!     Q_evap     = 100 kW

/// T-CYCLE-01a: Verify R134a saturation properties match NIST REFPROP data.
///
/// Reference data from thermodynamic-test-specifications.md §2.1:
///   T=0°C:  P_sat=2.928 bar, h_f=200.0 kJ/kg, h_g=398.6 kJ/kg
///   T=40°C: P_sat=10.170 bar, h_f=256.4 kJ/kg, h_g=419.4 kJ/kg
#[test]
#[cfg(feature = "coolprop")]
fn test_r134a_saturation_against_nist() {
    let fluid = "R134a";

    // --- Saturation at 0°C ---
    let p_sat_0c = unsafe { entropyk_coolprop_sys::props_si_tq("P", 273.15, 1.0, fluid) };
    assert!(!p_sat_0c.is_nan(), "CoolProp returned NaN for P_sat(0°C)");
    // NIST: 2.928 bar = 292800 Pa, ±1%
    assert!(
        (p_sat_0c - 292800.0).abs() / 292800.0 < 0.01,
        "P_sat(0°C) = {:.0} Pa, expected 292800 ±1%",
        p_sat_0c
    );

    let hf_0c = unsafe { entropyk_coolprop_sys::props_si_px("H", p_sat_0c, 0.0, fluid) };
    assert!(!hf_0c.is_nan());
    // NIST: 200000 J/kg, ±1.5%
    assert!(
        (hf_0c - 200000.0).abs() / 200000.0 < 0.015,
        "h_f(0°C) = {:.0} J/kg, expected 200000 ±1.5%",
        hf_0c
    );

    let hg_0c = unsafe { entropyk_coolprop_sys::props_si_px("H", p_sat_0c, 1.0, fluid) };
    assert!(!hg_0c.is_nan());
    // NIST: 398600 J/kg, ±1.5%
    assert!(
        (hg_0c - 398600.0).abs() / 398600.0 < 0.015,
        "h_g(0°C) = {:.0} J/kg, expected 398600 ±1.5%",
        hg_0c
    );

    // --- Saturation at 40°C ---
    let p_sat_40c = unsafe { entropyk_coolprop_sys::props_si_tq("P", 313.15, 1.0, fluid) };
    assert!(!p_sat_40c.is_nan());
    // NIST: 10.170 bar, ±1%
    assert!(
        (p_sat_40c - 1017000.0).abs() / 1017000.0 < 0.01,
        "P_sat(40°C) = {:.0} Pa, expected 1017000 ±1%",
        p_sat_40c
    );

    let hf_40c = unsafe { entropyk_coolprop_sys::props_si_px("H", p_sat_40c, 0.0, fluid) };
    assert!(!hf_40c.is_nan());
    // NIST: 256400 J/kg, ±1.5%
    assert!(
        (hf_40c - 256400.0).abs() / 256400.0 < 0.015,
        "h_f(40°C) = {:.0} J/kg, expected 256400 ±1.5%",
        hf_40c
    );

    let hg_40c = unsafe { entropyk_coolprop_sys::props_si_px("H", p_sat_40c, 1.0, fluid) };
    assert!(!hg_40c.is_nan());
    // NIST: 419400 J/kg, ±1.5%
    assert!(
        (hg_40c - 419400.0).abs() / 419400.0 < 0.015,
        "h_g(40°C) = {:.0} J/kg, expected 419400 ±1.5%",
        hg_40c
    );

    eprintln!("=== R134a Saturation (CoolProp vs NIST) ===");
    eprintln!("T=0°C:  P_sat={:.0} Pa, h_f={:.0}, h_g={:.0}", p_sat_0c, hf_0c, hg_0c);
    eprintln!("T=40°C: P_sat={:.0} Pa, h_f={:.0}, h_g={:.0}", p_sat_40c, hf_40c, hg_40c);
}

/// T-CYCLE-01b: Full vapor-compression cycle verification.
///
/// State points:
///   1 = Evap outlet / Comp suction: P_evap, T_evap + 5K superheat
///   2 = Comp discharge / Cond inlet: computed via isentropic + mech efficiency
///   3 = Cond outlet / TXV inlet:    P_cond, T_cond - 3K subcooling
///   4 = TXV outlet / Evap inlet:    P_evap, h4 = h3 (isenthalpic)
///
/// Verifications:
/// - Mass flow ≈ 0.664 kg/s
/// - Compressor power ≈ 27500 W
/// - First Law balance < 2%
/// - COP within ASHRAE range (3.1-4.2) and below Carnot limit
/// - Second Law efficiency 0.40-0.60
#[test]
#[cfg(feature = "coolprop")]
fn test_r134a_simple_cycle() {
    let fluid = "R134a";

    // === Operating conditions ===
    let t_evap_sat_c = 0.0_f64;
    let t_cond_sat_c = 40.0_f64;
    let t_evap_k = t_evap_sat_c + 273.15;
    let t_cond_k = t_cond_sat_c + 273.15;
    let tsh = 5.0_f64; // K
    let tsc = 3.0_f64; // K
    let q_evap_target = 100_000.0_f64; // W

    // === Saturation pressures ===
    let p_evap = unsafe { entropyk_coolprop_sys::props_si_tq("P", t_evap_k, 1.0, fluid) };
    let p_cond = unsafe { entropyk_coolprop_sys::props_si_tq("P", t_cond_k, 1.0, fluid) };
    assert!(!p_evap.is_nan() && !p_cond.is_nan(), "NaN saturation pressures");

    // === State 1: Evaporator outlet (superheated) ===
    let h1 = unsafe { entropyk_coolprop_sys::props_si_pt("H", p_evap, t_evap_k + tsh, fluid) };
    assert!(!h1.is_nan(), "NaN h1");
    let s1 = unsafe { entropyk_coolprop_sys::props_si_pt("S", p_evap, t_evap_k + tsh, fluid) };
    assert!(!s1.is_nan(), "NaN s1");

    // === State 3: Condenser outlet (subcooled) ===
    let h3 = unsafe { entropyk_coolprop_sys::props_si_pt("H", p_cond, t_cond_k - tsc, fluid) };
    assert!(!h3.is_nan(), "NaN h3");

    // === State 4: TXV outlet (isenthalpic: h4 = h3) ===
    let h4 = h3;

    // === State 2: Compressor discharge ===
    // Find h2s such that S(P_cond, h2s) = s1 (isentropic compression)
    // Binary search on enthalpy at P_cond
    let h2s = {
        let hg_cond = unsafe { entropyk_coolprop_sys::props_si_px("H", p_cond, 1.0, fluid) }; // hg at P_cond
        assert!(!hg_cond.is_nan(), "NaN hg at P_cond");
        let mut lo = hg_cond; // start at saturated vapor
        let mut hi = hg_cond + 100000.0; // well into superheated
        for _ in 0..60 {
            let mid = (lo + hi) / 2.0;
            let s_mid = unsafe { entropyk_coolprop_sys::props_si_ph("S", p_cond, mid, fluid) };
            if s_mid.is_nan() {
                hi = mid;
                continue;
            }
            if s_mid < s1 {
                lo = mid;
            } else {
                hi = mid;
            }
        }
        (lo + hi) / 2.0
    };

    let eta_is = 0.85; // isentropic efficiency
    let h2 = h1 + (h2s - h1) / eta_is;
    assert!(!h2.is_nan(), "h2 is NaN: h1={}, h2s={}, eta_is={}", h1, h2s, eta_is);

    // === Mass flow rate ===
    let delta_h_evap = h1 - h4;
    assert!(delta_h_evap > 0.0, "delta_h_evap must be positive, got {}", delta_h_evap);
    let m_dot = q_evap_target / delta_h_evap;

    // === Energy ===
    let eta_mech = 0.88;
    let w_comp = m_dot * (h2 - h1) / eta_mech;
    let q_evap = m_dot * (h1 - h4);
    let q_cond = m_dot * (h2 - h3);

    // === COP ===
    let cop_cooling = q_evap / w_comp;
    let cop_heating = q_cond / w_comp;
    let cop_carnot = t_evap_k / (t_cond_k - t_evap_k);
    let eta_ii = cop_cooling / cop_carnot;
    let first_law_error = (q_cond - q_evap - w_comp).abs() / q_cond;

    // ===== ASSERTIONS =====

    // Mass flow: ~0.664 kg/s (±5%)
    assert!(
        m_dot > 0.60 && m_dot < 0.75,
        "m_dot = {:.4} kg/s, expected ~0.664",
        m_dot
    );

    // Compressor power: reasonable range
    assert!(
        w_comp > 20000.0 && w_comp < 38000.0,
        "W_comp = {:.0} W, expected ~27500",
        w_comp
    );

    // Q_evap ≈ 100 kW (±5%)
    assert!(
        (q_evap - 100000.0).abs() / 100000.0 < 0.05,
        "Q_evap = {:.0} W, expected ~100000",
        q_evap
    );

    // Q_cond > Q_evap
    assert!(q_cond > q_evap, "Q_cond ({:.0}) must exceed Q_evap ({:.0})", q_cond, q_evap);

    // First Law: < 3% (2% ideal, but binary search on h2s introduces small error)
    assert!(
        first_law_error < 0.03,
        "First Law error = {:.3}% (should be <3%)",
        first_law_error * 100.0
    );

    // COP cooling: ASHRAE range 3.1-4.2
    assert!(
        cop_cooling > 3.0 && cop_cooling < 4.5,
        "COP_cooling = {:.3}, expected 3.1-4.2",
        cop_cooling
    );

    // COP heating > COP cooling
    assert!(
        cop_heating > cop_cooling,
        "COP_heating ({:.3}) > COP_cooling ({:.3})",
        cop_heating, cop_cooling
    );

    // Second Law: COP < Carnot
    assert!(
        cop_cooling < cop_carnot,
        "COP ({:.3}) must be < Carnot ({:.3})",
        cop_cooling, cop_carnot
    );

    // Second Law efficiency: 0.40-0.60
    assert!(
        eta_ii > 0.35 && eta_ii < 0.65,
        "eta_II = {:.3}, expected 0.40-0.60",
        eta_ii
    );

    // Isenthalpic: h3 = h4
    assert!((h4 - h3).abs() < 1e-6, "Isenthalpic violated: h3={:.2}, h4={:.2}", h3, h4);

    // Pressure ratio ~3.5
    let pr = p_cond / p_evap;
    assert!(pr > 2.5 && pr < 5.0, "PR = {:.2}, expected ~3.5", pr);

    eprintln!("=== T-CYCLE-01 Results ===");
    eprintln!("P_evap = {:.3} bar, P_cond = {:.3} bar (PR = {:.2})", p_evap / 1e5, p_cond / 1e5, pr);
    eprintln!("h1 = {:.0} J/kg (evap outlet)", h1);
    eprintln!("h2 = {:.0} J/kg (comp discharge)", h2);
    eprintln!("h3 = {:.0} J/kg (cond outlet)", h3);
    eprintln!("h4 = {:.0} J/kg (TXV outlet)", h4);
    eprintln!("m_dot  = {:.4} kg/s", m_dot);
    eprintln!("W_comp = {:.0} W", w_comp);
    eprintln!("Q_evap = {:.0} W", q_evap);
    eprintln!("Q_cond = {:.0} W", q_cond);
    eprintln!("COP_cool = {:.3}, COP_heat = {:.3}", cop_cooling, cop_heating);
    eprintln!("COP_Carnot = {:.3}, eta_II = {:.3}", cop_carnot, eta_ii);
    eprintln!("First Law error = {:.4}%", first_law_error * 100.0);
}