# Copyright (C) 2002, Thomas Hamelryck (thamelry@binf.ku.dk)
# This code is part of the Biopython distribution and governed by its
# license.  Please see the LICENSE file that should have been included
# as part of this package.

"""Output of PDB files."""

from Bio._py3k import basestring

from Bio.PDB.StructureBuilder import StructureBuilder  # To allow saving of chains, residues, etc..
from Bio.Data.IUPACData import atom_weights  # Allowed Elements


_ATOM_FORMAT_STRING = "%s%5i %-4s%c%3s %c%4i%c   %8.3f%8.3f%8.3f%s%6.2f      %4s%2s%2s\n"


class Select(object):
    """Select everything for PDB output (for use as a base class).

    Default selection (everything) during writing - can be used as base class
    to implement selective output. This selects which entities will be written out.
    """

    def __repr__(self):
        """Represent the output as a string for debugging."""
        return "<Select all>"

    def accept_model(self, model):
        """Overload this to reject models for output."""
        return 1

    def accept_chain(self, chain):
        """Overload this to reject chains for output."""
        return 1

    def accept_residue(self, residue):
        """Overload this to reject residues for output."""
        return 1

    def accept_atom(self, atom):
        """Overload this to reject atoms for output."""
        return 1


class PDBIO(object):
    """Write a Structure object (or a subset of a Structure object) as a PDB file.

    Examples
    --------
    >>> p=PDBParser()
    >>> s=p.get_structure("1fat", "1fat.pdb")
    >>> io=PDBIO()
    >>> io.set_structure(s)
    >>> io.save("out.pdb")

    """

    def __init__(self, use_model_flag=0):
        """Create the PDBIO object.

        :param use_model_flag: if 1, force use of the MODEL record in output.
        :type use_model_flag: int
        """
        self.use_model_flag = use_model_flag

    # private mathods

    def _get_atom_line(self, atom, hetfield, segid, atom_number, resname,
                       resseq, icode, chain_id, charge="  "):
        """Return an ATOM PDB string (PRIVATE)."""
        if hetfield != " ":
            record_type = "HETATM"
        else:
            record_type = "ATOM  "

        if atom.element:
            element = atom.element.strip().upper()
            if element.capitalize() not in atom_weights:
                raise ValueError("Unrecognised element %r" % atom.element)
            element = element.rjust(2)
        else:
            element = "  "

        name = atom.get_fullname().strip()
        # Pad atom name if:
        #     - smaller than 4 characters
        # AND - is not C, N, O, S, H, F, P, ..., one letter elements
        # AND - first character is NOT numeric (funky hydrogen naming rules)
        if len(name) < 4 and name[:1].isalpha() and len(element.strip()) < 2:
            name = " " + name

        altloc = atom.get_altloc()
        x, y, z = atom.get_coord()
        bfactor = atom.get_bfactor()
        occupancy = atom.get_occupancy()
        try:
            occupancy_str = "%6.2f" % occupancy
        except TypeError:
            if occupancy is None:
                occupancy_str = " " * 6
                import warnings
                from Bio import BiopythonWarning
                warnings.warn("Missing occupancy in atom %s written as blank" %
                              repr(atom.get_full_id()), BiopythonWarning)
            else:
                raise TypeError("Invalid occupancy %r in atom %r"
                                % (occupancy, atom.get_full_id()))

        args = (record_type, atom_number, name, altloc, resname, chain_id,
                resseq, icode, x, y, z, occupancy_str, bfactor, segid,
                element, charge)
        return _ATOM_FORMAT_STRING % args

    # Public methods

    def set_structure(self, pdb_object):
        """Check what the user is providing and build a structure."""
        if pdb_object.level == "S":
            structure = pdb_object
        else:
            sb = StructureBuilder()
            sb.init_structure('pdb')
            sb.init_seg(' ')
            # Build parts as necessary
            if pdb_object.level == "M":
                sb.structure.add(pdb_object)
                self.structure = sb.structure
            else:
                sb.init_model(0)
                if pdb_object.level == "C":
                    sb.structure[0].add(pdb_object)
                else:
                    sb.init_chain('A')
                    if pdb_object.level == "R":
                        try:
                            parent_id = pdb_object.parent.id
                            sb.structure[0]['A'].id = parent_id
                        except Exception:
                            pass
                        sb.structure[0]['A'].add(pdb_object)
                    else:
                        # Atom
                        sb.init_residue('DUM', ' ', 1, ' ')
                        try:
                            parent_id = pdb_object.parent.parent.id
                            sb.structure[0]['A'].id = parent_id
                        except Exception:
                            pass
                        sb.structure[0]['A'].child_list[0].add(pdb_object)

            # Return structure
            structure = sb.structure
        self.structure = structure

    def save(self, file, select=Select(), write_end=True, preserve_atom_numbering=False):
        """Save structure to a file.

        :param file: output file
        :type file: string or filehandle

        :param select: selects which entities will be written.
        :type select: object

        Typically select is a subclass of L{Select}, it should
        have the following methods:

         - accept_model(model)
         - accept_chain(chain)
         - accept_residue(residue)
         - accept_atom(atom)

        These methods should return 1 if the entity is to be
        written out, 0 otherwise.

        Typically select is a subclass of L{Select}.
        """
        get_atom_line = self._get_atom_line
        if isinstance(file, basestring):
            fp = open(file, "w")
            close_file = 1
        else:
            # filehandle, I hope :-)
            fp = file
            close_file = 0
        # multiple models?
        if len(self.structure) > 1 or self.use_model_flag:
            model_flag = 1
        else:
            model_flag = 0
        for model in self.structure.get_list():
            if not select.accept_model(model):
                continue
            # necessary for ENDMDL
            # do not write ENDMDL if no residues were written
            # for this model
            model_residues_written = 0
            if not preserve_atom_numbering:
                atom_number = 1
            if model_flag:
                fp.write("MODEL      %s\n" % model.serial_num)
            for chain in model.get_list():
                if not select.accept_chain(chain):
                    continue
                chain_id = chain.get_id()
                # necessary for TER
                # do not write TER if no residues were written
                # for this chain
                chain_residues_written = 0
                for residue in chain.get_unpacked_list():
                    if not select.accept_residue(residue):
                        continue
                    hetfield, resseq, icode = residue.get_id()
                    resname = residue.get_resname()
                    segid = residue.get_segid()
                    for atom in residue.get_unpacked_list():
                        if select.accept_atom(atom):
                            chain_residues_written = 1
                            model_residues_written = 1
                            if preserve_atom_numbering:
                                atom_number = atom.get_serial_number()
                            s = get_atom_line(atom, hetfield, segid, atom_number, resname,
                                              resseq, icode, chain_id)
                            fp.write(s)
                            if not preserve_atom_numbering:
                                atom_number += 1
                if chain_residues_written:
                    fp.write("TER   %5i      %3s %c%4i%c                                                      \n"
                             % (atom_number, resname, chain_id, resseq, icode))

            if model_flag and model_residues_written:
                fp.write("ENDMDL\n")
        if write_end:
            fp.write('END\n')
        if close_file:
            fp.close()