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"""Pass A parser: one ORCA 6.0 calculation (orca.out + orca.engrad) -> a plain-python record.

Design notes
------------
* Single forward scan over orca.out. The file can be 600 MB, so nothing is loaded whole: the FOCK
  block is consumed straight from the line iterator into its final numpy array.
* The scanner is a pushback iterator, so a sub-parser that reads one line too far can hand it back;
  otherwise a section's terminating line (often the *next* section's header) would be swallowed.
* Every section is optional. Datasets differ (NBO on/off, RHF/UHF, ECPs, linear dependencies), so a
  missing section leaves its fields as None rather than raising.
* The Fock matrix is returned as an int32 upper triangle in micro-Hartree, which is the storage
  encoding and is lossless with respect to ORCA's 6-decimal print.
* Reduced orbital populations are aggregated to shell totals (s, p, d, f, g) per atom; the
  individual components (pz, dxy, ...) are voluminous and low value, so they are skipped.

Returns a dict with keys grouped as: meta / system / atoms / pairs / orbitals / fock.
"""
from __future__ import annotations
import io, os, re, subprocess, tarfile
import numpy as np

SHELLS = ("s", "p", "d", "f", "g")
EH_TO_UEH = 1e6
_COLHDR = re.compile(r"^\s+0(\s+\d+)+\s*$")
_BOND = re.compile(r"B\(\s*(\d+)-\s*(\w+)\s*,\s*(\d+)-\s*(\w+)\s*\)\s*:\s*(-?\d+\.\d+)")


class _PB:
    """Line iterator with one-line pushback."""

    def __init__(self, it):
        self._it = iter(it)
        self._buf = []

    def __iter__(self):
        return self

    def __next__(self):
        if self._buf:
            return self._buf.pop()
        return next(self._it)

    def next(self, default=""):
        try:
            return self.__next__()
        except StopIteration:
            return default

    def push(self, line):
        self._buf.append(line)


def _f(tok):
    try:
        return float(tok)
    except (TypeError, ValueError):
        return None


def _after(line, sep):
    _, _, rest = line.partition(sep)
    return rest.strip()


def _num_after_colon(line):
    return _f(line.split(":")[-1].split()[0]) if ":" in line else None


def _is_rule(t):
    return bool(t) and set(t) <= set("-=*")


# ----------------------------------------------------------------------------- Fock block
def _read_matrix(pb, nbas, hdr):
    """Read one nbas x nbas matrix printed in column blocks, given its first header line."""
    F = np.zeros((nbas, nbas), dtype=np.float64)
    done = 0
    while done < nbas:
        while hdr.strip() == "":
            hdr = next(pb)
        ncol = len(hdr.split())
        rows = [next(pb) for _ in range(nbas)]
        blk = np.fromstring(" ".join(rows), sep=" ", dtype=np.float64)
        blk = blk.reshape(nbas, ncol + 1)[:, 1:]
        F[:, done:done + ncol] = blk
        done += ncol
        if done < nbas:
            hdr = next(pb)
    return F


def _tri_u_eh(F):
    iu = np.triu_indices(F.shape[0])
    return np.rint(F[iu] * EH_TO_UEH).astype(np.int32)


def _next_matrix_header(pb, max_skip=6):
    """Look for a column header, skipping blank and rule lines ('----', '****').
    Anything else is pushed back and None is returned."""
    for _ in range(max_skip + 1):
        line = pb.next(None)
        if line is None:
            return None
        t = line.strip()
        if t == "" or _is_rule(t):
            continue
        if _COLHDR.match(line):
            return line
        pb.push(line)
        return None
    return None


# ----------------------------------------------------------------------------- sub-parsers
def _atom_charges(pb):
    """'   0 Xe:    1.277884 [spin]' rows. Returns (charge, spin|None)."""
    q, sp = [], []
    for l2 in pb:
        t = l2.strip()
        if _is_rule(t):
            continue
        if not t:
            if q:
                break
            continue
        if ":" not in t:
            pb.push(l2)
            break
        head, _, rest = l2.partition(":")
        hp = head.split()
        if not hp or not hp[0].isdigit():
            pb.push(l2)
            break
        vals = rest.split()
        if not vals:
            break
        q.append(float(vals[0]))
        if len(vals) > 1:
            sp.append(float(vals[1]))
    return (np.array(q) if q else None, np.array(sp) if sp else None)


def _reduced_shells(pb, natm):
    """Per-atom shell totals from a REDUCED ORBITAL CHARGES block. Returns (charge, spin|None),
    each (natm, len(SHELLS)) or None."""
    if not natm:
        return None, None
    charge = np.zeros((natm, len(SHELLS)))
    spin = None
    target = charge
    atom = -1
    for l2 in pb:
        t = l2.strip()
        if not t or _is_rule(t):
            continue
        if t == "CHARGE":
            target = charge
            continue
        if t == "SPIN":
            spin = np.zeros((natm, len(SHELLS)))
            target = spin
            continue
        if ":" not in t:                       # next section banner
            pb.push(l2)
            break
        parts = l2.split(":")
        head = parts[0].split()
        if head and head[0].isdigit():
            atom = int(head[0])
        if len(parts) >= 3 and 0 <= atom < natm:
            tail = parts[1].split()
            if tail and tail[-1] in SHELLS:
                v = _f(parts[2].split()[0])
                if v is not None:
                    target[atom, SHELLS.index(tail[-1])] = v
    return charge, spin


def _bond_list(pb):
    """'B(  0-Xe,  1-Cl) :   0.1834' three per line, ending at a blank line."""
    out = []
    for l2 in pb:
        t = l2.strip()
        if _is_rule(t):
            continue
        if not t:
            if out:
                break
            continue
        found = _BOND.findall(l2)
        if not found:
            pb.push(l2)
            break
        for i, _, j, _, v in found:
            out.append((int(i), int(j), float(v)))
    return out


def _mayer_table(pb):
    cols = {k: [] for k in ("NA", "ZA", "QA", "VA", "BVA", "FA")}
    for l2 in pb:
        p = l2.split()
        if len(p) != 8 or not p[0].isdigit():
            pb.push(l2)
            break
        for k, v in zip(("NA", "ZA", "QA", "VA", "BVA", "FA"), p[2:]):
            cols[k].append(float(v))
    return {k: (np.array(v) if v else None) for k, v in cols.items()}


def _npa_summary(pb, r, natm):
    """RHF rows have 7 fields (El, No, Charge, Core, Valence, Rydberg, Total); UHF rows have an
    eighth, the natural spin density."""
    if not natm:
        return
    q = np.full(natm, np.nan)
    core = np.full(natm, np.nan)
    val = np.full(natm, np.nan)
    ryd = np.full(natm, np.nan)
    spin = np.full(natm, np.nan)
    for l2 in pb:
        t = l2.strip()
        if not t or _is_rule(t):
            continue
        p = t.split()
        if t.startswith("* Total *"):
            if len(p) >= 7:
                r["npa_core"], r["npa_valence"], r["npa_rydberg"] = (
                    float(p[4]), float(p[5]), float(p[6]))
            break
        if len(p) in (7, 8) and p[1].isdigit() and _f(p[2]) is not None:
            i = int(p[1]) - 1
            if 0 <= i < natm:
                q[i], core[i], val[i], ryd[i] = (float(p[2]), float(p[3]),
                                                 float(p[4]), float(p[5]))
                if len(p) == 8:
                    spin[i] = float(p[7])
            continue
        if not np.isnan(q).all():
            pb.push(l2)
            break
    if not np.isnan(q).all():
        r["npa_q"], r["npa_atom_core"] = q, core
        r["npa_atom_val"], r["npa_atom_ryd"] = val, ryd
        if not np.isnan(spin).all():
            r["npa_spin"] = spin


_CONFIG_SHELL = re.compile(r"(\d)([spdfg])\(\s*([\d.]+)\)")


def _natural_config(pb, natm):
    """'Xe  1      [core]5s( 2.00)5p( 4.39)4f( 0.02)5d( 0.15)' -> per-atom occupancy by l."""
    if not natm:
        return None
    out = np.zeros((natm, len(SHELLS)))
    seen = False
    for l2 in pb:
        t = l2.strip()
        if not t or _is_rule(t):
            continue
        p = t.split()
        if len(p) >= 3 and p[1].isdigit() and ("[core]" in t or _CONFIG_SHELL.search(t)):
            i = int(p[1]) - 1
            if 0 <= i < natm:
                for _, l, v in _CONFIG_SHELL.findall(t):
                    out[i, SHELLS.index(l)] += float(v)
                seen = True
            continue
        if seen:
            pb.push(l2)
            break
    return out if seen else None


def _orbital_energies(pb):
    """Returns (eps_a, occ_a, eps_b, occ_b); the beta pair is None for RHF."""
    eps_a = occ_a = eps_b = occ_b = None
    eps, occ = [], []
    spin = 0
    for l2 in pb:
        t = l2.strip()
        if not t or _is_rule(t):
            continue
        if "SPIN UP" in t:
            spin = 0
            continue
        if "SPIN DOWN" in t:
            eps_a, occ_a = np.array(eps), np.array(occ)
            eps, occ = [], []
            spin = 1
            continue
        if t.startswith("NO") and "OCC" in t:
            continue
        p = t.split()
        if len(p) == 4:
            o, e = _f(p[1]), _f(p[2])
            if o is not None and e is not None:
                occ.append(o)
                eps.append(e)
                continue
        pb.push(l2)
        break
    if spin == 0:
        eps_a, occ_a = np.array(eps), np.array(occ)
    else:
        eps_b, occ_b = np.array(eps), np.array(occ)
    return eps_a, occ_a, eps_b, occ_b


def _dipole(pb, r):
    for l2 in pb:
        t = l2.strip()
        if t.startswith("Electronic contribution"):
            r["dipole_elec"] = [float(x) for x in t.split(":")[1].split()]
        elif t.startswith("Nuclear contribution"):
            r["dipole_nuc"] = [float(x) for x in t.split(":")[1].split()]
        elif t.startswith("Total Dipole Moment"):
            r["dipole_total"] = [float(x) for x in t.split(":")[1].split()]
        elif t.startswith("Magnitude (a.u.)"):
            r["dipole_au"] = _num_after_colon(t)
        elif t.startswith("Magnitude (Debye)"):
            r["dipole_debye"] = _num_after_colon(t)
            return


def _quadrupole(pb, r):
    for l2 in pb:
        t = l2.strip()
        p = t.split()
        if t.startswith("NUC") and len(p) >= 7:
            r["quad_nuc"] = [float(x) for x in p[1:7]]
        elif t.startswith("EL") and len(p) >= 7:
            r["quad_elec"] = [float(x) for x in p[1:7]]
        elif t.startswith("TOT") and len(p) >= 7:
            r["quad_total"] = [float(x) for x in p[1:7]]
        elif t.startswith("diagonalized tensor"):
            nxt = next(pb).split()
            if len(nxt) >= 3:
                r["quad_diag"] = [float(x) for x in nxt[:3]]
        elif t.startswith("Isotropic quadrupole"):
            r["quad_iso"] = _num_after_colon(t)
            return


# ----------------------------------------------------------------------------- main parser
def _blank_record():
    return {
        "version": None, "hftyp": None, "charge": None, "mult": None, "nelec": None,
        "nbas": None, "naux": None, "smallest_ovlp_eig": None, "n_lindep": None,
        "e_total": None, "e_nuc_rep": None, "e_one_elec": None, "e_two_elec": None,
        "e_kinetic": None, "virial_ratio": None, "e_xc": None, "e_nl": None, "e_exchange": None,
        "n_alpha_int": None, "n_beta_int": None,
        "s2": None, "s2_ideal": None, "s2_dev": None,
        "scf_converged": False, "scf_cycles": None,
        "conv_denergy": None, "conv_maxdp": None, "conv_rmsdp": None, "conv_diiserr": None,
        "dipole_elec": None, "dipole_nuc": None, "dipole_total": None,
        "dipole_au": None, "dipole_debye": None,
        "quad_nuc": None, "quad_elec": None, "quad_total": None, "quad_diag": None,
        "quad_iso": None, "rot_const_cm": None, "rot_const_mhz": None,
        "grad_norm": None, "grad_rms": None, "grad_max": None,
        "run_time_s": None, "terminated_normally": False,
        "nbo_available": False, "npa_available": False,
        "npa_core": None, "npa_valence": None, "npa_rydberg": None,
        "nbo_lewis": None, "nbo_nonlewis": None,
        "elements": [], "coords": None, "ecp_ncore": {},
        "mulliken_q": None, "mulliken_s": None, "loewdin_q": None, "loewdin_s": None,
        "mayer_NA": None, "mayer_ZA": None, "mayer_QA": None,
        "mayer_VA": None, "mayer_BVA": None, "mayer_FA": None,
        "npa_q": None, "npa_atom_core": None, "npa_atom_val": None, "npa_atom_ryd": None,
        "npa_spin": None, "natural_config": None,
        "mulliken_shell_q": None, "loewdin_shell_q": None,
        "mulliken_shell_s": None, "loewdin_shell_s": None,
        "mayer_bo": [], "loewdin_bo": [], "mulliken_ovlp": [],
        "eps_a": None, "occ_a": None, "eps_b": None, "occ_b": None,
        "fock_a": None, "fock_b": None,
    }


def parse_orca_out(fh):
    r = _blank_record()
    pb = _PB(fh)
    coords = []
    for line in pb:
        s = line.strip()

        # ---------------- header / settings
        if r["version"] is None and "Program Version" in line:
            r["version"] = line.split("Program Version")[1].split()[0]
        elif "Hartree-Fock type" in line:
            r["hftyp"] = _after(line, "....")
        elif "Total Charge" in line and "...." in line:
            r["charge"] = int(float(_after(line, "....")))
        elif s.startswith("Multiplicity") and "Mult " in line:
            r["mult"] = int(float(_after(line, "....")))
        elif "Number of Electrons" in line and "...." in line:
            r["nelec"] = int(float(_after(line, "....")))
        elif line.startswith("Number of basis functions") and r["nbas"] is None:
            r["nbas"] = int(_after(line, "..."))
        elif "# of basis functions in Aux-J" in line:
            r["naux"] = int(_after(line, "..."))
        elif "Smallest eigenvalue" in line and r["smallest_ovlp_eig"] is None:
            r["smallest_ovlp_eig"] = _f(_after(line, "..."))
        elif "Number of eigenvalues below threshold" in line:
            r["n_lindep"] = int(_after(line, "..."))
        elif "ECP" in line and "replacing" in line and "core electrons" in line:
            m = re.search(r"Type\s+(\S+)\s+ECP.*replacing\s+(\d+)\s+core electrons", line)
            if m:
                r["ecp_ncore"][m.group(1)] = int(m.group(2))

        # ---------------- geometry
        elif s == "CARTESIAN COORDINATES (ANGSTROEM)" and not r["elements"]:
            next(pb)
            for l2 in pb:
                p = l2.split()
                if len(p) != 4:
                    pb.push(l2)
                    break
                r["elements"].append(p[0])
                coords.append([float(p[1]), float(p[2]), float(p[3])])

        # ---------------- energies
        elif s.startswith("Total Energy") and ":" in line and r["e_total"] is None:
            r["e_total"] = _num_after_colon(line)
        elif s.startswith("Nuclear Repulsion") and ":" in line:
            r["e_nuc_rep"] = _num_after_colon(line)
        elif s.startswith("One Electron Energy"):
            r["e_one_elec"] = _num_after_colon(line)
        elif s.startswith("Two Electron Energy"):
            r["e_two_elec"] = _num_after_colon(line)
        elif s.startswith("Kinetic Energy"):
            r["e_kinetic"] = _num_after_colon(line)
        elif s.startswith("Virial Ratio"):
            r["virial_ratio"] = _num_after_colon(line)
        elif s.startswith("E(XC)"):
            r["e_xc"] = _num_after_colon(line)
        elif s.startswith("NL Energy, E(C,NL)"):
            r["e_nl"] = _num_after_colon(line)
        elif s.startswith("New exchange energy"):
            r["e_exchange"] = _num_after_colon(line)
        elif s.startswith("N(Alpha)"):
            r["n_alpha_int"] = _num_after_colon(line)
        elif s.startswith("N(Beta)"):
            r["n_beta_int"] = _num_after_colon(line)
        elif s.startswith("FINAL SINGLE POINT ENERGY") and r["e_total"] is None:
            r["e_total"] = _f(s.split()[-1])

        # ---------------- SCF convergence
        elif "SCF CONVERGED AFTER" in line:
            r["scf_converged"] = True
            m = re.search(r"AFTER\s+(\d+)\s+CYCLES", line)
            if m:
                r["scf_cycles"] = int(m.group(1))
        elif s.startswith("Last Energy change"):
            r["conv_denergy"] = _f(_after(line, "...").split()[0])
        elif s.startswith("Last MAX-Density change"):
            r["conv_maxdp"] = _f(_after(line, "...").split()[0])
        elif s.startswith("Last RMS-Density change"):
            r["conv_rmsdp"] = _f(_after(line, "...").split()[0])
        elif s.startswith("Last DIIS Error"):
            r["conv_diiserr"] = _f(_after(line, "...").split()[0])
        elif s.startswith("Expectation value of <S**2>"):
            r["s2"] = _num_after_colon(line)
        elif s.startswith("Ideal value S*(S+1)"):
            r["s2_ideal"] = _num_after_colon(line)
        elif s.startswith("Deviation") and r["s2"] is not None and r["s2_dev"] is None:
            r["s2_dev"] = _num_after_colon(line)

        # ---------------- orbitals and Fock
        elif s == "ORBITAL ENERGIES":
            ea, oa, eb, ob = _orbital_energies(pb)
            r["eps_a"], r["occ_a"] = ea, oa
            if eb is not None:
                r["eps_b"], r["occ_b"] = eb, ob
        elif s == "FOCK" and r["nbas"]:
            hdr = _next_matrix_header(pb, max_skip=6)
            if hdr is not None:
                F = _read_matrix(pb, r["nbas"], hdr)
                r["fock_a"] = _tri_u_eh(F)
                del F
                hdr_b = _next_matrix_header(pb, max_skip=6)
                if hdr_b is not None:
                    Fb = _read_matrix(pb, r["nbas"], hdr_b)
                    r["fock_b"] = _tri_u_eh(Fb)
                    del Fb

        # ---------------- population analyses
        elif s.startswith("MULLIKEN ATOMIC CHARGES"):
            r["mulliken_q"], r["mulliken_s"] = _atom_charges(pb)
        elif s.startswith("LOEWDIN ATOMIC CHARGES"):
            r["loewdin_q"], r["loewdin_s"] = _atom_charges(pb)
        elif s.startswith("MULLIKEN REDUCED ORBITAL CHARGES"):
            r["mulliken_shell_q"], r["mulliken_shell_s"] = _reduced_shells(pb, len(r["elements"]))
        elif s.startswith("LOEWDIN REDUCED ORBITAL CHARGES"):
            r["loewdin_shell_q"], r["loewdin_shell_s"] = _reduced_shells(pb, len(r["elements"]))
        elif s.startswith("MULLIKEN OVERLAP CHARGES"):
            r["mulliken_ovlp"] = _bond_list(pb)
        elif s.startswith("LOEWDIN BOND ORDERS"):
            r["loewdin_bo"] = _bond_list(pb)
        elif s.startswith("ATOM") and "BVA" in s and "ZA" in s:
            for k, v in _mayer_table(pb).items():
                r[f"mayer_{k}"] = v
        elif s.startswith("Mayer bond orders larger than"):
            r["mayer_bo"] = _bond_list(pb)

        # ---------------- NBO / NPA
        elif "Now starting NBO" in line:
            r["nbo_available"] = True
        elif s.startswith("Summary of Natural Population Analysis") and r["npa_q"] is None:
            r["npa_available"] = True
            _npa_summary(pb, r, len(r["elements"]))
        elif s.startswith("Atom No") and "Natural Electron Configuration" in s and r["natural_config"] is None:
            r["natural_config"] = _natural_config(pb, len(r["elements"]))
        elif s.startswith("Total Lewis") and r["nbo_lewis"] is None:
            p = s.split()
            if len(p) > 2:
                r["nbo_lewis"] = _f(p[2])
        elif s.startswith("Total non-Lewis") and r["nbo_nonlewis"] is None:
            p = s.split()
            if len(p) > 2:
                r["nbo_nonlewis"] = _f(p[2])

        # ---------------- properties
        elif s == "DIPOLE MOMENT" and r["dipole_total"] is None:
            _dipole(pb, r)
        elif s == "QUADRUPOLE MOMENT" and r["quad_total"] is None:
            _quadrupole(pb, r)
        elif s.startswith("Rotational constants in cm-1"):
            r["rot_const_cm"] = [float(x) for x in s.split(":")[1].split()]
        elif s.startswith("Rotational constants in MHz"):
            r["rot_const_mhz"] = [float(x) for x in s.split(":")[1].split()]
        elif s.startswith("Norm of the Cartesian gradient"):
            r["grad_norm"] = _f(_after(line, "..."))
        elif s.startswith("RMS gradient"):
            r["grad_rms"] = _f(_after(line, "..."))
        elif s.startswith("MAX gradient"):
            r["grad_max"] = _f(_after(line, "..."))
        elif "ORCA TERMINATED NORMALLY" in line:
            r["terminated_normally"] = True
        elif s.startswith("TOTAL RUN TIME"):
            m = re.search(r"(\d+) days (\d+) hours (\d+) minutes (\d+) seconds (\d+) msec", s)
            if m:
                d, h, mi, sec, ms = (int(x) for x in m.groups())
                r["run_time_s"] = d * 86400 + h * 3600 + mi * 60 + sec + ms / 1000

    r["coords"] = np.array(coords, dtype=np.float64) if coords else None
    return r


# ----------------------------------------------------------------------------- engrad
def parse_engrad(fh):
    """Returns (n_atoms, energy, gradient (n,3) Eh/bohr, Z (n,), coords_bohr (n,3))."""
    lines = [l for l in fh if not l.lstrip().startswith("#") and l.strip()]
    it = iter(lines)
    n = int(next(it).split()[0])
    energy = float(next(it).split()[0])
    vals = [float(next(it).split()[0]) for _ in range(3 * n)]
    zs, xyz = [], []
    for _ in range(n):
        p = next(it).split()
        zs.append(int(p[0]))
        xyz.append([float(x) for x in p[1:4]])
    return n, energy, np.array(vals).reshape(n, 3), np.array(zs), np.array(xyz)


def iter_lines(fb, encoding="utf-8", chunk=1 << 20):
    """Yield decoded lines from a binary stream. tarfile's stream mode ('r|') hands back objects
    that TextIOWrapper rejects (no seekable()), so decoding is done here."""
    buf = b""
    while True:
        data = fb.read(chunk)
        if not data:
            break
        buf += data
        parts = buf.split(b"\n")
        buf = parts.pop()
        for part in parts:
            yield part.decode(encoding, "replace")
    if buf:
        yield buf.decode(encoding, "replace")


# ----------------------------------------------------------------------------- archive entry
def parse_archive(tar_path):
    """Stream an orca.tar.zst and parse the members we need. Never writes to disk."""
    proc = subprocess.Popen(["zstd", "-dc", tar_path], stdout=subprocess.PIPE,
                            stderr=subprocess.DEVNULL)
    rec, grad = None, None
    try:
        with tarfile.open(fileobj=proc.stdout, mode="r|") as tf:
            for member in tf:
                name = os.path.basename(member.name)
                if name == "orca.out":
                    rec = parse_orca_out(iter_lines(tf.extractfile(member)))
                elif name == "orca.engrad":
                    grad = parse_engrad(iter_lines(tf.extractfile(member)))
    finally:
        if proc.stdout:
            proc.stdout.close()
        proc.wait()
    if rec is None:
        raise ValueError(f"no orca.out in {tar_path}")
    if grad is not None:
        n, e_grad, g, z, xyz_bohr = grad
        rec["forces"] = -g
        rec["atomic_numbers"] = z
        rec["coords_bohr"] = xyz_bohr
        rec["e_total_engrad"] = e_grad
    else:
        rec["forces"] = rec["atomic_numbers"] = None
        rec["coords_bohr"] = rec["e_total_engrad"] = None
    return rec