"""
Preprocessing utilities for ECFlow web app.

Handles:
- CSV/NPZ parsing for both CV and TPD data
- Physical-to-dimensionless unit conversion for CV (Compton convention)
- Formal potential estimation
- Diffusion coefficient estimation via Randles-Sevcik
"""

import io
import numpy as np

# Physical constants
F_CONST = 96485.3329  # Faraday constant (C/mol)
R_CONST = 8.314462    # Gas constant (J/(mol·K))


# =========================================================================
# CV nondimensionalization
# =========================================================================

def nondimensionalize_cv(E_volts, i_amps, v_Vs, E0_V, T_K=298.15,
                         A_cm2=0.0707, C_A_molcm3=1e-6, D_A_cm2s=1e-5, n=1,
                         v_ref_Vs=0.1):
    """
    Convert physical CV data to dimensionless units for the ECFlow model.

    Potential and current are nondimensionalized using the Compton convention
    with the scan-rate-dependent diffusion length d = sqrt(D·RT/(nFv)):
        θ = (E - E₀) / (RT/nF)
        ψ = i / (nFAC·D/d)

    The dimensionless scan rate σ = v / v_ref is computed separately.
    In the Compton convention σ ≡ 1 by construction (d absorbs v), but the
    ECFlow model uses σ as an explicit conditioning variable to distinguish
    experiments at different scan rates. Setting v_ref so that σ spans the
    training range (~0.1–100) gives the model the scan-rate information.

    Args:
        E_volts: potential array (V)
        i_amps: current array (A)
        v_Vs: scan rate (V/s)
        E0_V: formal potential (V)
        T_K: temperature (K)
        A_cm2: electrode area (cm²)
        C_A_molcm3: bulk concentration (mol/cm³)
        D_A_cm2s: diffusion coefficient (cm²/s)
        n: number of electrons
        v_ref_Vs: reference scan rate (V/s) at which σ = 1

    Returns:
        theta: dimensionless potential array
        flux: dimensionless current array
        sigma: dimensionless scan rate (= v_Vs / v_ref_Vs)
    """
    thermal_voltage = R_CONST * T_K / (n * F_CONST)

    theta = (E_volts - E0_V) / thermal_voltage

    d = np.sqrt(D_A_cm2s * R_CONST * T_K / (n * F_CONST * v_Vs))
    flux_scale = n * F_CONST * A_cm2 * C_A_molcm3 * D_A_cm2s / d
    flux = i_amps / flux_scale

    sigma = v_Vs / v_ref_Vs

    return theta.astype(np.float32), flux.astype(np.float32), float(sigma)


def estimate_E0(E, i):
    """
    Estimate formal potential from CV midpoint of anodic/cathodic peaks.

    Args:
        E: potential array (V)
        i: current array (A)

    Returns:
        E0 estimate (V)
    """
    E = np.asarray(E)
    i = np.asarray(i)

    mid = len(E) // 2
    i_anodic = i[:mid] if i[:mid].max() > abs(i[:mid].min()) else i[mid:]
    i_cathodic = i[mid:] if i[mid:].min() < -abs(i[mid:].max()) else i[:mid]

    E_pa = E[np.argmax(i)]
    E_pc = E[np.argmin(i)]

    return float((E_pa + E_pc) / 2.0)


def estimate_D_randles_sevcik(i_peak_A, v_Vs, A_cm2, C_molcm3, n=1, T_K=298.15):
    """
    Estimate diffusion coefficient from Randles-Sevcik equation.

    i_p = 0.4463 * n^(3/2) * F^(3/2) * A * C * sqrt(D * v / (R * T))

    Args:
        i_peak_A: peak current (A)
        v_Vs: scan rate (V/s)
        A_cm2: electrode area (cm^2)
        C_molcm3: concentration (mol/cm^3)
        n: number of electrons
        T_K: temperature (K)

    Returns:
        D estimate (cm^2/s)
    """
    coeff = 0.4463 * n**1.5 * F_CONST**1.5 * A_cm2 * C_molcm3
    if abs(coeff) < 1e-30 or v_Vs <= 0:
        return 1e-5
    ratio = abs(i_peak_A) / coeff
    D = ratio**2 * R_CONST * T_K / v_Vs
    return max(float(D), 1e-10)


# =========================================================================
# CSV parsing
# =========================================================================

def parse_cv_csv(file_content, delimiter=None):
    """
    Parse a CV CSV file with flexible column detection.

    Expected columns: potential (V or mV) and current (A, mA, uA, nA).
    Optionally includes a time column (s) to infer the scan rate.
    Auto-detects column names and units from header.

    Args:
        file_content: string or bytes of CSV content
        delimiter: CSV delimiter (auto-detected if None)

    Returns:
        dict with 'E_V' (potential in V), 'i_A' (current in A),
        and optionally 'scan_rate_Vs' (V/s) if time is available.
    """
    if isinstance(file_content, bytes):
        file_content = file_content.decode("utf-8", errors="replace")

    lines = file_content.strip().split("\n")
    if len(lines) < 2:
        raise ValueError("CSV must have at least a header and one data row")

    if delimiter is None:
        for d in [",", "\t", ";"]:
            if d in lines[0]:
                delimiter = d
                break
        if delimiter is None:
            delimiter = ","

    header = [h.strip().lower() for h in lines[0].split(delimiter)]

    e_col, i_col, t_col = None, None, None
    e_scale, i_scale = 1.0, 1.0

    time_patterns = ["time/s", "time (s)", "time/ms", "time (ms)",
                     "elapsed time", "t/s", "t (s)", "time"]

    potential_patterns = [
        ("e/v", 1.0), ("e (v)", 1.0), ("potential/v", 1.0), ("potential (v)", 1.0),
        ("ewe/v", 1.0), ("working electrode", 1.0),
        ("e/mv", 1e-3), ("e (mv)", 1e-3), ("potential/mv", 1e-3), ("potential (mv)", 1e-3),
        ("voltage", 1.0), ("e", 1.0), ("potential", 1.0),
    ]
    current_patterns = [
        ("i/a", 1.0), ("i (a)", 1.0), ("current/a", 1.0), ("current (a)", 1.0),
        ("<i>/ma", 1e-3),
        ("i/ma", 1e-3), ("i (ma)", 1e-3), ("current/ma", 1e-3), ("current (ma)", 1e-3),
        ("i/ua", 1e-6), ("i (ua)", 1e-6), ("i/µa", 1e-6), ("i (µa)", 1e-6),
        ("current/ua", 1e-6), ("current/µa", 1e-6),
        ("i/na", 1e-9), ("i (na)", 1e-9),
        ("current", 1.0), ("i", 1.0),
    ]

    for idx, col in enumerate(header):
        if t_col is None:
            for pat in time_patterns:
                if pat in col:
                    t_col = idx
                    break
            if t_col == idx:
                continue
        if e_col is None:
            for pat, scale in potential_patterns:
                if pat in col:
                    e_col, e_scale = idx, scale
                    break
        if i_col is None:
            for pat, scale in current_patterns:
                if pat in col:
                    i_col, i_scale = idx, scale
                    break

    if e_col is None or i_col is None:
        non_time = [idx for idx in range(len(header)) if idx != t_col]
        if len(non_time) >= 2:
            e_col, i_col = non_time[0], non_time[1]
        else:
            raise ValueError(
                f"Cannot identify potential/current columns from header: {header}"
            )

    all_cols = {e_col, i_col}
    if t_col is not None:
        all_cols.add(t_col)
    max_col = max(all_cols)

    E_vals, i_vals, t_vals = [], [], []
    for line in lines[1:]:
        parts = line.strip().split(delimiter)
        if len(parts) <= max_col:
            continue
        try:
            E_vals.append(float(parts[e_col]) * e_scale)
            i_vals.append(float(parts[i_col]) * i_scale)
            if t_col is not None:
                t_vals.append(float(parts[t_col]))
        except ValueError:
            continue

    if len(E_vals) < 5:
        raise ValueError(f"Only {len(E_vals)} valid data points found")

    result = {
        "E_V": np.array(E_vals, dtype=np.float32),
        "i_A": np.array(i_vals, dtype=np.float32),
    }

    if t_vals:
        t_arr = np.array(t_vals, dtype=np.float64)
        E_arr = np.array(E_vals, dtype=np.float64)
        mid = len(E_arr) // 2
        dE = np.abs(np.diff(E_arr[:mid]))
        dt = np.abs(np.diff(t_arr[:mid]))
        valid = dt > 1e-12
        if valid.sum() > 10:
            v = float(np.median(dE[valid] / dt[valid]))
            if v > 1e-6:
                result["scan_rate_Vs"] = v

    return result


def parse_tpd_csv(file_content, delimiter=None):
    """
    Parse a TPD CSV file.

    Expected columns: temperature (K or °C) and signal (arb. units).
    Optionally includes a time column (s) to infer the heating rate.
    Auto-detects Celsius vs Kelvin.

    Returns:
        dict with 'T_K' (temperature in K), 'signal' (arb. units),
        and optionally 'beta_Ks' (heating rate in K/s) if time is available.
    """
    if isinstance(file_content, bytes):
        file_content = file_content.decode("utf-8", errors="replace")

    lines = file_content.strip().split("\n")
    if len(lines) < 2:
        raise ValueError("CSV must have at least a header and one data row")

    if delimiter is None:
        for d in [",", "\t", ";"]:
            if d in lines[0]:
                delimiter = d
                break
        if delimiter is None:
            delimiter = ","

    header = [h.strip().lower() for h in lines[0].split(delimiter)]

    t_col, s_col, time_col = None, None, None
    is_celsius = False

    temp_patterns = [
        ("temperature", False), ("temp", False), ("t/k", False), ("t (k)", False),
        ("t/c", True), ("t (c)", True), ("t/°c", True), ("t (°c)", True),
    ]
    signal_patterns = ["signal", "rate", "intensity", "des", "tpd"]
    time_patterns = ["time/s", "time (s)", "time"]

    for idx, col in enumerate(header):
        if t_col is None:
            for pat, celsius in temp_patterns:
                if pat in col:
                    t_col = idx
                    is_celsius = celsius
                    break
        if s_col is None:
            for pat in signal_patterns:
                if pat in col:
                    s_col = idx
                    break
        if time_col is None:
            for pat in time_patterns:
                if pat in col:
                    time_col = idx
                    break

    if t_col is None or s_col is None:
        if len(header) >= 2:
            t_col, s_col = 0, 1
        else:
            raise ValueError(
                f"Cannot identify temperature/signal columns from header: {header}"
            )

    all_cols = {t_col, s_col}
    if time_col is not None:
        all_cols.add(time_col)
    max_col = max(all_cols)

    T_vals, s_vals, time_vals = [], [], []
    for line in lines[1:]:
        parts = line.strip().split(delimiter)
        if len(parts) <= max_col:
            continue
        try:
            T_vals.append(float(parts[t_col]))
            s_vals.append(float(parts[s_col]))
            if time_col is not None:
                time_vals.append(float(parts[time_col]))
        except ValueError:
            continue

    if len(T_vals) < 5:
        raise ValueError(f"Only {len(T_vals)} valid data points found")

    T_arr = np.array(T_vals, dtype=np.float32)
    if is_celsius or T_arr.max() < 200:
        T_arr += 273.15

    result = {
        "T_K": T_arr,
        "signal": np.array(s_vals, dtype=np.float32),
    }

    if time_vals:
        time_arr = np.array(time_vals, dtype=np.float32)
        dt = time_arr[-1] - time_arr[0]
        dT = T_arr[-1] - T_arr[0]
        if dt > 0:
            result["beta_Ks"] = float(dT / dt)

    return result


def parse_dimensionless_cv_csv(file_content, delimiter=None):
    """
    Parse a CSV that already contains dimensionless CV data.

    Expected columns: theta (dimensionless potential), flux (dimensionless current).

    Returns:
        dict with 'theta', 'flux' arrays
    """
    if isinstance(file_content, bytes):
        file_content = file_content.decode("utf-8", errors="replace")

    lines = file_content.strip().split("\n")
    if len(lines) < 2:
        raise ValueError("CSV must have at least a header and one data row")

    if delimiter is None:
        for d in [",", "\t", ";"]:
            if d in lines[0]:
                delimiter = d
                break
        if delimiter is None:
            delimiter = ","

    header = [h.strip().lower() for h in lines[0].split(delimiter)]

    t_col, f_col = None, None
    for idx, col in enumerate(header):
        if t_col is None and any(p in col for p in ["theta", "potential", "e"]):
            t_col = idx
        if f_col is None and any(p in col for p in ["flux", "current", "j", "i"]):
            f_col = idx

    if t_col is None or f_col is None:
        if len(header) >= 2:
            t_col, f_col = 0, 1
        else:
            raise ValueError(f"Cannot identify columns from header: {header}")

    theta_vals, flux_vals = [], []
    for line in lines[1:]:
        parts = line.strip().split(delimiter)
        if len(parts) <= max(t_col, f_col):
            continue
        try:
            theta_vals.append(float(parts[t_col]))
            flux_vals.append(float(parts[f_col]))
        except ValueError:
            continue

    return {
        "theta": np.array(theta_vals, dtype=np.float32),
        "flux": np.array(flux_vals, dtype=np.float32),
    }


# ── TPD summary feature extraction ──────────────────────────────────

MAX_HEATING_RATES = 3
TPD_FEATURES_PER_RATE = 6
TPD_SUMMARY_DIM = MAX_HEATING_RATES * TPD_FEATURES_PER_RATE + MAX_HEATING_RATES  # 21


def extract_tpd_summary_stats(temperature, rate, lengths, heating_rates, n_rates):
    """Extract 21-dim hand-crafted summary statistics from raw TPD data.

    Per heating rate (6 features): normalized peak rate, peak temperature,
    half-peak width, normalized total desorption integral, asymmetry ratio
    (left vs right half-width), log10(peak rate).
    Plus log10(heating_rate) per curve.

    Args:
        temperature: [N, T] array of temperatures (K)
        rate: [N, T] array of desorption rates
        lengths: [N] array of valid lengths per curve
        heating_rates: [N] array of heating rates (K/s)
        n_rates: number of heating rates

    Returns:
        1-D array of shape (21,)
    """
    features = np.zeros(TPD_SUMMARY_DIM, dtype=np.float32)
    for i in range(min(n_rates, MAX_HEATING_RATES)):
        L = int(lengths[i])
        temp = temperature[i, :L]
        r = rate[i, :L]
        peak_abs = np.max(np.abs(r)) + 1e-30

        peak_rate = np.max(r)
        idx_peak = np.argmax(r)
        peak_temp = temp[idx_peak]

        half_max = peak_rate / 2.0
        above_half = r >= half_max
        if np.any(above_half):
            indices = np.where(above_half)[0]
            half_width = temp[indices[-1]] - temp[indices[0]]
            left_width = peak_temp - temp[indices[0]]
            right_width = temp[indices[-1]] - peak_temp
            asymmetry = (right_width - left_width) / (half_width + 1e-30)
        else:
            half_width = 0.0
            asymmetry = 0.0

        if L > 1:
            integral = (np.trapezoid(r, temp)
                        if hasattr(np, 'trapezoid') else np.trapz(r, temp))
        else:
            integral = 0.0

        log_peak = np.log10(peak_abs)

        offset = i * TPD_FEATURES_PER_RATE
        features[offset + 0] = peak_rate / peak_abs
        features[offset + 1] = peak_temp
        features[offset + 2] = half_width
        features[offset + 3] = integral / (peak_abs * (temp.max() - temp.min()) + 1e-30)
        features[offset + 4] = asymmetry
        features[offset + 5] = log_peak

        features[MAX_HEATING_RATES * TPD_FEATURES_PER_RATE + i] = np.log10(heating_rates[i])
    return features