from __future__ import annotations

import json
import re
import subprocess
import urllib.parse
from pathlib import Path
from typing import Any, Dict, Iterable, List

import numpy as np
import pandas as pd
import requests
from rdkit import Chem, DataStructs
from rdkit.Chem import AllChem
from rdkit.Chem.Scaffolds import MurckoScaffold


def _curl_get_text(url: str, timeout: int = 30) -> str:
    cp = subprocess.run(
        [
            "curl",
            "-L",
            "--silent",
            "--show-error",
            "--fail",
            "--retry",
            "2",
            "--retry-delay",
            "1",
            "--max-time",
            str(int(timeout)),
            url,
        ],
        capture_output=True,
        text=True,
        check=False,
    )
    if cp.returncode != 0:
        raise RuntimeError(f"curl failed for {url}: {cp.stderr.strip()}")
    return cp.stdout


def _http_json(url: str, timeout: int = 30) -> Dict[str, Any]:
    # Prefer curl on this workstation because requests+TLS has been unstable.
    try:
        return json.loads(_curl_get_text(url, timeout=timeout))
    except Exception:
        pass
    r = requests.get(url, timeout=timeout)
    r.raise_for_status()
    return r.json()


def _http_text(url: str, timeout: int = 60) -> str:
    try:
        return _curl_get_text(url, timeout=timeout)
    except Exception:
        pass
    r = requests.get(url, timeout=timeout)
    r.raise_for_status()
    return r.text


def _canonicalize_smiles(smiles: str) -> str | None:
    mol = Chem.MolFromSmiles(str(smiles))
    if mol is None:
        return None
    return Chem.MolToSmiles(mol, canonical=True)


def _morgan_bv(smiles: str, nbits: int = 2048):
    mol = Chem.MolFromSmiles(smiles)
    if mol is None:
        return None
    return AllChem.GetMorganFingerprintAsBitVect(mol, radius=2, nBits=nbits)


def _tanimoto(smiles_a: str, smiles_b: str) -> float:
    fp_a = _morgan_bv(smiles_a)
    fp_b = _morgan_bv(smiles_b)
    if fp_a is None or fp_b is None:
        return 0.0
    return float(DataStructs.TanimotoSimilarity(fp_a, fp_b))


def _scaffold_smiles(smiles: str) -> str | None:
    mol = Chem.MolFromSmiles(smiles)
    if mol is None:
        return None
    try:
        return MurckoScaffold.MurckoScaffoldSmiles(mol=mol)
    except Exception:
        return None


def _chemcomp_info(comp_id: str) -> Dict[str, Any]:
    d = _http_json(f"https://data.rcsb.org/rest/v1/core/chemcomp/{comp_id}", timeout=30)
    desc = d.get("rcsb_chem_comp_descriptor", {})
    smiles = desc.get("SMILES_stereo") or desc.get("SMILES")
    return {
        "comp_id": comp_id,
        "name": d.get("chem_comp", {}).get("name"),
        "formula_weight": d.get("chem_comp", {}).get("formula_weight"),
        "smiles": smiles,
        "inchi_key": desc.get("InChIKey"),
    }


def _download_pdb(pdb_id: str, out_path: Path) -> Path:
    out_path.parent.mkdir(parents=True, exist_ok=True)
    url = f"https://files.rcsb.org/download/{pdb_id}.pdb"
    out_path.write_text(_http_text(url, timeout=60), encoding="utf-8")
    return out_path


def _pubchem_similarity_cids(smiles: str, threshold: int, max_records: int) -> list[int]:
    enc = urllib.parse.quote(smiles, safe="")
    url = (
        "https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/fastsimilarity_2d/smiles/"
        f"{enc}/cids/JSON?Threshold={int(threshold)}&MaxRecords={int(max_records)}"
    )
    try:
        d = _http_json(url, timeout=30)
        cids = [int(x) for x in d.get("IdentifierList", {}).get("CID", [])]
        if cids:
            return cids
    except Exception:
        pass

    # CID-based fallback for molecules where SMILES endpoint is sparse.
    cid_url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/smiles/{enc}/cids/JSON"
    try:
        cands = [int(x) for x in _http_json(cid_url, timeout=20).get("IdentifierList", {}).get("CID", [])]
    except Exception:
        return []
    if not cands:
        return []
    cid = cands[0]
    sim_url = (
        "https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/fastsimilarity_2d/cid/"
        f"{cid}/cids/JSON?Threshold={int(threshold)}&MaxRecords={int(max_records)}"
    )
    try:
        return [int(x) for x in _http_json(sim_url, timeout=30).get("IdentifierList", {}).get("CID", [])]
    except Exception:
        return []


def _pubchem_properties_for_cids(cids: Iterable[int]) -> pd.DataFrame:
    cids = list(cids)
    if not cids:
        return pd.DataFrame(
            columns=[
                "cid",
                "smiles",
                "molecular_formula",
                "molecular_weight",
                "xlogp",
                "tpsa",
                "hbd",
                "hba",
                "rotatable_bonds",
                "heavy_atom_count",
            ]
        )

    rows: list[dict[str, Any]] = []
    # 200 CIDs/request is a stable balance on PubChem for URL size and throughput.
    chunk_size = 200
    for i in range(0, len(cids), chunk_size):
        chunk = cids[i : i + chunk_size]
        joined = ",".join(str(x) for x in chunk)
        url = (
            "https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/"
            f"{joined}/property/SMILES,ConnectivitySMILES,MolecularFormula,MolecularWeight,"
            "XLogP,TPSA,HBondDonorCount,HBondAcceptorCount,RotatableBondCount,HeavyAtomCount/JSON"
        )
        props = []
        for _attempt in range(3):
            try:
                props = _http_json(url, timeout=30).get("PropertyTable", {}).get("Properties", [])
            except Exception:
                props = []
            if props:
                break
        if not props:
            continue
        for p in props:
            rows.append(
                {
                    "cid": int(p.get("CID")),
                    "smiles": str(p.get("SMILES") or p.get("ConnectivitySMILES") or ""),
                    "molecular_formula": p.get("MolecularFormula"),
                    "molecular_weight": p.get("MolecularWeight"),
                    "xlogp": p.get("XLogP"),
                    "tpsa": p.get("TPSA"),
                    "hbd": p.get("HBondDonorCount"),
                    "hba": p.get("HBondAcceptorCount"),
                    "rotatable_bonds": p.get("RotatableBondCount"),
                    "heavy_atom_count": p.get("HeavyAtomCount"),
                }
            )
    return pd.DataFrame(rows)


def _fetch_chembl_smiles(target_chembl_id: str, max_rows: int) -> pd.DataFrame:
    if int(max_rows) <= 0:
        return pd.DataFrame(
            columns=[
                "smiles",
                "molecule_chembl_id",
                "assay_chembl_id",
                "standard_type",
                "standard_units",
                "standard_value",
                "source_database",
            ]
        )
    rows: list[dict[str, Any]] = []
    limit = 1000
    offset = 0
    while len(rows) < max_rows:
        url = (
            "https://www.ebi.ac.uk/chembl/api/data/activity.json"
            f"?target_chembl_id={target_chembl_id}&limit={limit}&offset={offset}"
        )
        try:
            d = _http_json(url, timeout=30)
        except Exception:
            break
        acts = d.get("activities", [])
        if not acts:
            break
        for a in acts:
            smi = _canonicalize_smiles(str(a.get("canonical_smiles") or ""))
            if smi is None:
                continue
            rows.append(
                {
                    "smiles": smi,
                    "molecule_chembl_id": a.get("molecule_chembl_id"),
                    "assay_chembl_id": a.get("assay_chembl_id"),
                    "standard_type": a.get("standard_type"),
                    "standard_units": a.get("standard_units"),
                    "standard_value": a.get("standard_value"),
                    "source_database": "ChEMBL",
                }
            )
            if len(rows) >= max_rows:
                break
        offset += limit
        if d.get("page_meta", {}).get("next") is None:
            break
    return pd.DataFrame(rows)


def _generate_fallback_smiles(seed_smiles: str, needed: int) -> List[str]:
    """Conservative, deterministic fallback if database retrieval is insufficient."""
    variants: List[str] = []
    candidates = [seed_smiles]
    replacements = [
        ("Cl", "F"),
        ("F", "Cl"),
        ("OC", "OCC"),
        ("CC", "CCC"),
    ]
    while candidates and len(variants) < needed:
        smi = candidates.pop(0)
        for a, b in replacements:
            if a not in smi:
                continue
            cand = smi.replace(a, b, 1)
            c = _canonicalize_smiles(cand)
            if c is None:
                continue
            if c not in variants:
                variants.append(c)
            if len(variants) >= needed:
                break
    return variants


def build_large_benchmark_library(config: Dict[str, Any], root: Path, logger) -> Dict[str, Any]:
    dataset_cfg = config["benchmark_dataset"]
    target_cfg = config["target"]
    ref_cfg = config["reference"]

    out_dir = root / dataset_cfg["output_dir"]
    out_dir.mkdir(parents=True, exist_ok=True)

    reference_path = out_dir / "reference_ligands.csv"
    raw_path = out_dir / "shared_library_raw.csv"
    dedup_path = out_dir / "shared_library_dedup.csv"
    shuffled_path = out_dir / "shared_library_shuffled.csv"
    provenance_path = out_dir / "ligand_provenance.csv"
    metadata_path = out_dir / "ligand_metadata.csv"
    similarity_path = out_dir / "similarity_distribution.csv"
    reuse_existing = bool(dataset_cfg.get("reuse_existing", True))

    required = [reference_path, raw_path, dedup_path, shuffled_path, provenance_path, metadata_path]
    docking_target_path = root / target_cfg["docking_target_path"]
    if reuse_existing and all(p.exists() for p in required):
        if not similarity_path.exists():
            dedup_existing = pd.read_csv(dedup_path)
            _write_similarity_distribution(dedup_existing, similarity_path)
        if not docking_target_path.exists():
            _download_pdb(str(ref_cfg["pdb_id"]), docking_target_path)
        return {
            "reference_df": pd.read_csv(reference_path),
            "raw_df": pd.read_csv(raw_path),
            "dedup_df": pd.read_csv(dedup_path),
            "shuffled_df": pd.read_csv(shuffled_path),
            "provenance_df": pd.read_csv(provenance_path),
            "metadata_df": pd.read_csv(metadata_path),
            "similarity_df": pd.read_csv(similarity_path),
            "target_path": docking_target_path,
            "out_dir": out_dir,
        }

    ref_smiles_cfg = str(ref_cfg.get("reference_smiles") or dataset_cfg.get("reference_smiles") or "").strip()
    ref_name_cfg = str(ref_cfg.get("reference_name") or dataset_cfg.get("reference_name") or "").strip()
    ref_formula_weight_cfg = dataset_cfg.get("reference_formula_weight", np.nan)
    ref_comp: Dict[str, Any]
    if ref_smiles_cfg:
        ref_smiles = _canonicalize_smiles(ref_smiles_cfg)
        if ref_smiles is None:
            raise RuntimeError("Invalid configured reference_smiles")
        ref_comp = {
            "comp_id": str(ref_cfg["ligand_comp_id"]),
            "name": ref_name_cfg or str(ref_cfg["ligand_comp_id"]),
            "formula_weight": ref_formula_weight_cfg,
            "smiles": ref_smiles,
            "inchi_key": "",
        }
    else:
        ref_comp = _chemcomp_info(str(ref_cfg["ligand_comp_id"]))
        ref_smiles = _canonicalize_smiles(str(ref_comp["smiles"] or ""))
        if ref_smiles is None:
            raise RuntimeError("Invalid reference SMILES from RCSB chemcomp endpoint")

    ref_df = pd.DataFrame(
        [
            {
                "reference_id": str(ref_cfg["reference_id"]),
                "pdb_id": str(ref_cfg["pdb_id"]),
                "ligand_comp_id": str(ref_cfg["ligand_comp_id"]),
                "ligand_name": ref_comp["name"],
                "reference_smiles": ref_smiles,
                "source_structure": str(ref_cfg["pdb_id"]),
            }
        ]
    )
    ref_df.to_csv(reference_path, index=False)

    _download_pdb(str(ref_cfg["pdb_id"]), docking_target_path)

    target_size = int(dataset_cfg.get("target_size", 7500))
    min_keep = float(dataset_cfg.get("min_similarity_keep", 0.25))
    max_records = int(dataset_cfg.get("pubchem_max_records", 50000))
    thresholds = [int(x) for x in dataset_cfg.get("pubchem_thresholds", [95, 90, 85, 80, 75, 70, 65, 60, 55, 50])]

    records: Dict[str, Dict[str, Any]] = {}
    for thr in thresholds:
        cids = _pubchem_similarity_cids(ref_smiles, threshold=thr, max_records=max_records)
        # Keep API workload bounded to what is still needed for target size.
        remaining = max(0, int(target_size) - len(records))
        if remaining <= 0:
            break
        # Query a modest over-sampling margin to compensate duplicates/canonicalization.
        limit = min(len(cids), max(remaining + 600, 1200))
        cids = cids[:limit]
        props = _pubchem_properties_for_cids(cids)
        if props.empty:
            continue
        for row in props.itertuples(index=False):
            c = _canonicalize_smiles(str(row.smiles))
            if c is None:
                continue
            sim = _tanimoto(ref_smiles, c)
            if sim < min_keep:
                continue
            prev = records.get(c)
            base = {
                "ligand_id": "",
                "smiles": c,
                "source": "database",
                "source_database": "PubChem",
                "source_type": "retrieved",
                "original_database_id": f"CID:{int(row.cid)}",
                "reference_similarity": float(sim),
                "scaffold_core": _scaffold_smiles(c),
                "scaffold_match": int(_scaffold_smiles(c) == _scaffold_smiles(ref_smiles)),
                "retrieval_threshold": int(thr),
                "is_reference": False,
                "parent_reference_ligand": str(ref_cfg["reference_id"]),
                "molecular_formula": row.molecular_formula,
                "molecular_weight": row.molecular_weight,
                "xlogp": row.xlogp,
                "tpsa": row.tpsa,
                "hbd": row.hbd,
                "hba": row.hba,
                "rotatable_bonds": row.rotatable_bonds,
                "heavy_atom_count": row.heavy_atom_count,
            }
            if prev is None or (float(base["reference_similarity"]) > float(prev["reference_similarity"])):
                records[c] = base
        logger.info("PubChem threshold=%s cumulative=%s", thr, len(records))
        if len(records) >= int(target_size * 1.2):
            break

    # ChEMBL supplement if needed (still database-first).
    if len(records) < target_size:
        chembl_target = str(dataset_cfg.get("chembl_target_id", "CHEMBL5023"))
        chembl_max = int(dataset_cfg.get("chembl_max_rows", 25000))
        cdf = _fetch_chembl_smiles(target_chembl_id=chembl_target, max_rows=chembl_max)
        for row in cdf.itertuples(index=False):
            c = _canonicalize_smiles(str(row.smiles))
            if c is None or c in records:
                continue
            sim = _tanimoto(ref_smiles, c)
            if sim < min_keep:
                continue
            records[c] = {
                "ligand_id": "",
                "smiles": c,
                "source": "database",
                "source_database": "ChEMBL",
                "source_type": "retrieved",
                "original_database_id": str(row.molecule_chembl_id or ""),
                "reference_similarity": float(sim),
                "scaffold_core": _scaffold_smiles(c),
                "scaffold_match": int(_scaffold_smiles(c) == _scaffold_smiles(ref_smiles)),
                "retrieval_threshold": np.nan,
                "is_reference": False,
                "parent_reference_ligand": str(ref_cfg["reference_id"]),
                "molecular_formula": np.nan,
                "molecular_weight": np.nan,
                "xlogp": np.nan,
                "tpsa": np.nan,
                "hbd": np.nan,
                "hba": np.nan,
                "rotatable_bonds": np.nan,
                "heavy_atom_count": np.nan,
            }
            if len(records) >= int(target_size * 1.2):
                break
        logger.info("ChEMBL supplement cumulative=%s", len(records))

    # Ensure reference is present.
    records[ref_smiles] = {
        "ligand_id": str(ref_cfg["reference_id"]),
        "smiles": ref_smiles,
        "source": "reference",
        "source_database": "RCSB",
        "source_type": "reference",
        "original_database_id": str(ref_cfg["ligand_comp_id"]),
        "reference_similarity": 1.0,
        "scaffold_core": _scaffold_smiles(ref_smiles),
        "scaffold_match": 1,
        "retrieval_threshold": np.nan,
        "is_reference": True,
        "parent_reference_ligand": str(ref_cfg["reference_id"]),
        "molecular_formula": np.nan,
        "molecular_weight": ref_comp.get("formula_weight"),
        "xlogp": np.nan,
        "tpsa": np.nan,
        "hbd": np.nan,
        "hba": np.nan,
        "rotatable_bonds": np.nan,
        "heavy_atom_count": np.nan,
    }

    raw_df = pd.DataFrame(records.values())
    raw_df = raw_df.sort_values(["is_reference", "reference_similarity"], ascending=[False, False]).reset_index(drop=True)
    raw_df.to_csv(raw_path, index=False)

    dedup_df = raw_df.drop_duplicates(subset=["smiles"], keep="first").reset_index(drop=True)

    allow_generated = bool(dataset_cfg.get("allow_generated_fallback", True))
    if dedup_df.shape[0] < target_size and allow_generated:
        need = int(target_size - dedup_df.shape[0])
        generated = _generate_fallback_smiles(seed_smiles=ref_smiles, needed=need * 2)
        gen_rows = []
        for s in generated:
            if s in set(dedup_df["smiles"].astype(str).tolist()):
                continue
            sim = _tanimoto(ref_smiles, s)
            gen_rows.append(
                {
                    "ligand_id": "",
                    "smiles": s,
                    "source": "generated",
                    "source_database": "generated",
                    "source_type": "generated",
                    "original_database_id": "",
                    "reference_similarity": float(sim),
                    "scaffold_core": _scaffold_smiles(s),
                    "scaffold_match": int(_scaffold_smiles(s) == _scaffold_smiles(ref_smiles)),
                    "retrieval_threshold": np.nan,
                    "is_reference": False,
                    "parent_reference_ligand": str(ref_cfg["reference_id"]),
                    "molecular_formula": np.nan,
                    "molecular_weight": np.nan,
                    "xlogp": np.nan,
                    "tpsa": np.nan,
                    "hbd": np.nan,
                    "hba": np.nan,
                    "rotatable_bonds": np.nan,
                    "heavy_atom_count": np.nan,
                }
            )
            if len(gen_rows) >= need:
                break
        if gen_rows:
            dedup_df = pd.concat([dedup_df, pd.DataFrame(gen_rows)], axis=0, ignore_index=True)

    dedup_df = dedup_df.sort_values(["is_reference", "source_type", "reference_similarity"], ascending=[False, True, False]).reset_index(
        drop=True
    )
    if dedup_df.shape[0] > target_size:
        refs = dedup_df[dedup_df["is_reference"].astype(bool)].copy()
        non_refs = dedup_df[~dedup_df["is_reference"].astype(bool)].copy()
        keep = max(0, target_size - refs.shape[0])
        dedup_df = pd.concat([refs, non_refs.head(keep)], axis=0, ignore_index=True)

    dedup_df = dedup_df.reset_index(drop=True)
    for i in range(dedup_df.shape[0]):
        if bool(dedup_df.loc[i, "is_reference"]):
            dedup_df.loc[i, "ligand_id"] = str(ref_cfg["reference_id"])
        else:
            dedup_df.loc[i, "ligand_id"] = f"lb_{i:05d}"
    dedup_df.to_csv(dedup_path, index=False)

    shuffle_seed = int(dataset_cfg.get("shuffle_seed", 1337))
    shuffled_df = dedup_df.sample(frac=1.0, random_state=shuffle_seed).reset_index(drop=True)
    shuffled_df["shuffle_seed"] = shuffle_seed
    shuffled_df.to_csv(shuffled_path, index=False)

    provenance_df = dedup_df[
        [
            "ligand_id",
            "smiles",
            "source",
            "source_database",
            "source_type",
            "original_database_id",
            "is_reference",
            "parent_reference_ligand",
            "reference_similarity",
            "scaffold_core",
            "scaffold_match",
            "retrieval_threshold",
        ]
    ].copy()
    provenance_df.to_csv(provenance_path, index=False)

    metadata_df = dedup_df[
        [
            "ligand_id",
            "smiles",
            "molecular_formula",
            "molecular_weight",
            "xlogp",
            "tpsa",
            "hbd",
            "hba",
            "rotatable_bonds",
            "heavy_atom_count",
        ]
    ].copy()
    metadata_df.to_csv(metadata_path, index=False)
    similarity_df = _write_similarity_distribution(dedup_df, similarity_path)

    return {
        "reference_df": ref_df,
        "raw_df": raw_df,
        "dedup_df": dedup_df,
        "shuffled_df": shuffled_df,
        "provenance_df": provenance_df,
        "metadata_df": metadata_df,
        "similarity_df": similarity_df,
        "target_path": docking_target_path,
        "out_dir": out_dir,
        "shuffle_seed": shuffle_seed,
    }


def _write_similarity_distribution(df: pd.DataFrame, path: Path) -> pd.DataFrame:
    vals = pd.to_numeric(df.get("reference_similarity", pd.Series(dtype=float)), errors="coerce").dropna()
    bins = np.linspace(0.0, 1.0, 21)
    hist, edges = np.histogram(vals.to_numpy(dtype=float), bins=bins)
    out = pd.DataFrame(
        {
            "bin_left": edges[:-1],
            "bin_right": edges[1:],
            "count": hist,
            "fraction": hist / max(1, int(hist.sum())),
        }
    )
    out.to_csv(path, index=False)
    return out