"""Input validation and position constraint building."""

import pandas as pd


def _validate_design_inputs(pdb_files: list | None, ensemble_mode: str) -> str | None:
    if not pdb_files:
        return "Upload at least one PDB or CIF file."

    if ensemble_mode == "user" and len(pdb_files) < 2:
        return "User ensemble mode requires at least two files."

    single_file_mode_messages = {
        "none": "Single structure mode requires exactly one file.",
        "synthetic": "Protpardelle mode requires exactly one file.",
    }
    message = single_file_mode_messages.get(ensemble_mode)
    if message and len(pdb_files) != 1:
        return message

    return None


def _build_pos_constraint_df(
    pdb_key: str,
    fixed_pos_seq: str,
    fixed_pos_scn: str,
    fixed_pos_override_seq: str,
    pos_restrict_aatype: str,
    symmetry_pos: str,
) -> pd.DataFrame | None:
    row = {}
    if fixed_pos_seq and fixed_pos_seq.strip():
        row["fixed_pos_seq"] = fixed_pos_seq.strip()
    if fixed_pos_scn and fixed_pos_scn.strip():
        row["fixed_pos_scn"] = fixed_pos_scn.strip()
    if fixed_pos_override_seq and fixed_pos_override_seq.strip():
        row["fixed_pos_override_seq"] = fixed_pos_override_seq.strip()
    if pos_restrict_aatype and pos_restrict_aatype.strip():
        row["pos_restrict_aatype"] = pos_restrict_aatype.strip()
    if symmetry_pos and symmetry_pos.strip():
        row["symmetry_pos"] = symmetry_pos.strip()
    if not row:
        return None
    row["pdb_key"] = pdb_key
    return pd.DataFrame([row])