# Source code for propertyestimator.substances

    """
    An API for defining and creating substances.
    """

    import abc
    import math
    from enum import Enum

    import numpy as np

    from propertyestimator import unit
    from propertyestimator.utils.serialization import TypedBaseModel

    class Substance(TypedBaseModel):
        """Defines the components, their amounts, and their roles in a system.

        Examples
        --------
        A neat liquid containing only a single component:

        >>> liquid = Substance()
        >>> liquid.add_component(Substance.Component(smiles='O'), Substance.MoleFraction(1.0))

        A binary mixture containing two components, where the mole fractions are explicitly stated:

        >>> binary_mixture = Substance()
        >>> binary_mixture.add_component(Substance.Component(smiles='O'), Substance.MoleFraction(0.2))
        >>> binary_mixture.add_component(Substance.Component(smiles='CO'), Substance.MoleFraction(0.8))

        The infinite dilution of one molecule within a bulk solvent or mixture may also be specified
        by defining the exact number of copies of that molecule, rather than a mole fraction:

        >>> benzene = Substance.Component(smiles='C1=CC=CC=C1', role=Substance.ComponentRole.Solute)
        >>> water = Substance.Component(smiles='O', role=Substance.ComponentRole.Solvent)
        >>>
        >>> infinite_dilution = Substance()
        >>> infinite_dilution.add_component(component=benzene, amount=Substance.ExactAmount(1)) # Infinite dilution.
        >>> infinite_dilution.add_component(component=water, amount=Substance.MoleFraction(1.0))

        In this example we explicitly flag benzene as being the solute and the water component the solvent.
        This enables workflow's to easily identify key molecules of interest, such as the molecule which should
        be 'grown' into solution during solvation free energy calculations.
        """

        class ComponentRole(Enum):
            """An enum which describes the role of a component in the system,
            such as whether the component is a solvent, a solute, a receptor etc.

            These roles are mainly only used by specific protocols to identify
            the correct species in a system, such as when doing docking or performing
            solvation free energy calculations.
            """
            Solvent = 'Solvent'
            Solute = 'Solute'

            Ligand = 'Ligand'
            Receptor = 'Receptor'

            Undefined = 'Undefined'

        class Component(TypedBaseModel):
            """Defines a single component in a system, as well as properties
            such as it's relative proportion in the system.
            """

            @property
            def identifier(self):
                """str: A unique identifier for this component, which is either a
                smiles descriptor or the supplied label."""
                return self._smiles or self._label

            @property
            def label(self):
                """str: A string label which describes this compound, for example, CB8."""
                return self._label

            @property
            def smiles(self):
                """str: The smiles pattern which describes this component, which may be None
                for complex (e.g protein) molecules."""
                return self._smiles

            @property
            def role(self):
                """ComponentRole: The role of this component in the system, such as a
                ligand or a receptor."""
                return self._role

            def __init__(self, smiles=None, label=None, role=None):
                """Constructs a new Component object with either a label or
                a smiles string, but not both.

                Notes
                -----
                The `label` and `smiles` arguments are mutually exclusive, and only
                one can be passed while the other should be `None`.

                Parameters
                ----------
                smiles: str
                    A SMILES descriptor of the component
                label: str
                    A string label which describes this compound, for example, CB8.
                role: ComponentRole, optional
                    The role of this component in the system. If no role is specified,
                    a default role of solvent is applied.
                """

                if label == smiles:
                    label = None

                assert ((label is None and smiles is not None) or
                        (label is not None and smiles is None) or
                        (label is None and smiles is None))

                label = label if label is not None else smiles

                self._label = label
                self._smiles = smiles

                self._role = role or Substance.ComponentRole.Solvent

            def __getstate__(self):
                return {
                    'label': self.label,
                    'smiles': self.smiles,

                    'role': self.role
                }

            def __setstate__(self, state):
                self._label = state['label']
                self._smiles = state['smiles']

                self._role = state['role']

            def __str__(self):
                return self.identifier

            def __hash__(self):
                return hash((self.identifier, self._role))

            def __eq__(self, other):
                return hash(self) == hash(other)

            def __ne__(self, other):
                return not (self == other)

        class Amount(abc.ABC):
            """An abstract representation of the amount of a given component
            in a substance.
            """

            @property
            def value(self):
                """The value of this amount."""
                return self._value

            @property
            def identifier(self):
                """A string identifier for this amount."""
                raise NotImplementedError()

            def __init__(self, value=None):
                """Constructs a new Amount object."""
                self._value = value

            @abc.abstractmethod
            def to_number_of_molecules(self, total_substance_molecules, tolerance=None):
                """Converts this amount to an exact number of molecules

                Parameters
                ----------
                total_substance_molecules: int
                    The total number of molecules in the whole substance. This amount
                    will contribute to a portion of this total number.
                tolerance: float, optional
                    The tolerance with which this amount should be in. As an example,
                    when converting a mole fraction into a number of molecules, the
                    total number of molecules may not be sufficiently large enough to
                    reproduce this amount.

                Returns
                -------
                int
                    The number of molecules which this amount represents,
                    given the `total_substance_molecules`.
                """
                raise NotImplementedError()

            def __getstate__(self):
                return {'value': self._value}

            def __setstate__(self, state):
                self._value = state['value']

            def __str__(self):
                return self.identifier

            def __eq__(self, other):
                return np.isclose(self._value, other.value)

            def __ne__(self, other):
                return not (self == other)

            def __hash__(self):
                return hash(self.identifier)

        class MoleFraction(Amount):
            """Represents the amount of a component in a substance as a
            mole fraction."""

            @property
            def value(self):
                """float: The value of this amount."""
                return super(Substance.MoleFraction, self).value

            @property
            def identifier(self):
                return f'{{{self._value:.6f}}}'

            def __init__(self, value=1.0):
                """Constructs a new MoleFraction object.

                Parameters
                ----------
                value: float
                    A mole fraction in the range (0.0, 1.0]
                """

                if value <= 0.0 or value > 1.0:

                    raise ValueError('A mole fraction must be greater than zero, and less than or '
                                     'equal to one.')

                if math.floor(value * 1e6) < 1:

                    raise ValueError('Mole fractions are only precise to the sixth '
                                     'decimal place within this class representation.')

                super().__init__(value)

            def to_number_of_molecules(self, total_substance_molecules, tolerance=None):

                # Determine how many molecules of each type will be present in the system.
                number_of_molecules = self._value * total_substance_molecules
                fractional_number_of_molecules = number_of_molecules % 1

                if np.isclose(fractional_number_of_molecules, 0.5):
                    number_of_molecules = int(number_of_molecules)
                else:
                    number_of_molecules = int(round(number_of_molecules))

                if number_of_molecules == 0:
                    raise ValueError('The total number of substance molecules was not large enough, '
                                     'such that this non-zero amount translates into zero molecules '
                                     'of this component in the substance.')

                if tolerance is not None:

                    mole_fraction = number_of_molecules / total_substance_molecules

                    if abs(mole_fraction - self._value) > tolerance:
                        raise ValueError(f'The mole fraction ({mole_fraction}) given a total number of molecules '
                                         f'({total_substance_molecules}) is outside of the tolerance {tolerance} '
                                         f'of the target mole fraction {self._value}')

                return number_of_molecules

        class ExactAmount(Amount):
            """Represents the amount of a component in a substance as an
            exact number of molecules.

            The expectation is that this amount should be used for components which
            are infinitely dilute (such as ligands in binding calculations), and hence
            do not contribute to the total mole fraction of a substance"""

            @property
            def value(self):
                """int: The value of this amount."""
                return super(Substance.ExactAmount, self).value

            @property
            def identifier(self):
                return f'({int(round(self._value)):d})'

            def __init__(self, value=1):
                """Constructs a new ExactAmount object.

                Parameters
                ----------
                value: int
                    An exact number of molecules.
                """

                if not np.isclose(int(round(value)), value):
                    raise ValueError('The value must be an integer.')

                super().__init__(value)

            def to_number_of_molecules(self, total_substance_molecules, tolerance=None):
                return self._value

        @property
        def identifier(self):
            """str: A unique str representation of this substance, which encodes all components
            and their amounts in the substance."""

            component_identifiers = [component.identifier for component in self._components]
            component_identifiers.sort()

            sorted_component_identifiers = [component.identifier for component in self._components]
            sorted_component_identifiers.sort()

            identifier_split = []

            for component_identifier in sorted_component_identifiers:

                component_amounts = sorted(self._amounts[component_identifier], key=lambda x: type(x).__name__)
                amount_identifier = ''.join([component_amount.identifier for component_amount in component_amounts])

                identifier = f'{component_identifier}{amount_identifier}'
                identifier_split.append(identifier)

            return '|'.join(identifier_split)

        @property
        def components(self):
            """list of Substance.Component: A list of all of the components in this substance."""
            return self._components

        @property
        def number_of_components(self):
            """int: The number of different components in this substance."""
            return len(self._components)

        def __init__(self):
            """Constructs a new Substance object."""

            self._amounts = {}
            self._components = []

        @classmethod
        def from_components(cls, *components):
            """Creates a new `Substance` object from a list of components.
            This method assumes that all components should be present with
            equal mole fractions.

            Parameters
            ----------
            components: Substance.Component or str
                The components to add to the substance. These may either be full
                `Substance.Component` objects or just the smiles representation
                of the component.

            Returns
            -------
            Substance
                The substance containing the requested components in equal amounts.
            """

            if len(components) == 0:
                raise ValueError('At least one component must be specified')

            mole_fraction = 1.0 / len(components)

            return_substance = cls()

            for component in components:

                if isinstance(component, str):
                    component = Substance.Component(smiles=component)

                return_substance.add_component(component, Substance.MoleFraction(mole_fraction))

            return return_substance

        def add_component(self, component, amount):
            """Add a component to the Substance. If the component is already present in
            the substance, then the mole fraction will be added to the current mole
            fraction of that component.

            Parameters
            ----------
            component : Substance.Component
                The component to add to the system.
            amount : Substance.Amount
                The amount of this component in the substance.
            """

            assert isinstance(component, Substance.Component)
            assert isinstance(amount, Substance.Amount)

            if isinstance(amount, Substance.MoleFraction):

                total_mole_fraction = amount.value

                for component_identifier in self._amounts:

                    total_mole_fraction += sum([amount.value for amount in self._amounts[component_identifier] if
                                                isinstance(amount, Substance.MoleFraction)])

                if np.isclose(total_mole_fraction, 1.0):
                    total_mole_fraction = 1.0

                if total_mole_fraction > 1.0:
                    raise ValueError(f'The total mole fraction of this substance {total_mole_fraction} exceeds 1.0')

            if component.identifier not in self._amounts:
                self._components.append(component)

            existing_amount_of_type = None

            all_amounts = [] if component.identifier not in self._amounts else self._amounts[component.identifier]
            remaining_amounts = []

            # Check to see if an amount of the same type already exists in
            # the substance, such that this amount should be appended to it.
            for existing_amount in all_amounts:

                if not type(existing_amount) is type(amount):

                    remaining_amounts.append(existing_amount)
                    continue

                existing_amount_of_type = existing_amount
                break

            if existing_amount_of_type is not None:

                # Append any existing amounts to the new amount.
                amount = type(amount)(existing_amount_of_type.value + amount.value)

            remaining_amounts.append(amount)
            self._amounts[component.identifier] = frozenset(remaining_amounts)

        def get_amounts(self, component):
            """Returns the amounts of the component in this substance.

            Parameters
            ----------
            component: str or Substance.Component
                The component (or it's identifier) to retrieve the amount of.

            Returns
            -------
            list of Substance.Amount
                The amounts of the component in this substance.
            """
            assert isinstance(component, str) or isinstance(component, Substance.Component)
            identifier = component if isinstance(component, str) else component.identifier

            return self._amounts[identifier]

        def get_molecules_per_component(self, maximum_molecules, tolerance=None):
            """Returns the number of molecules for each component in this substance,
            given a maximum total number of molecules.

            Parameters
            ----------
            maximum_molecules: int
                The maximum number of molecules.
            tolerance: float, optional
                The tolerance within which this amount should be represented. As
                an example, when converting a mole fraction into a number of molecules,
                the total number of molecules may not be sufficiently large enough to
                reproduce this amount.

            Returns
            -------
            dict of str and int
                A dictionary of molecule counts per component, where each key is
                a component identifier.
            """

            number_of_molecules = {}
            remaining_molecule_slots = maximum_molecules

            for index, component in enumerate(self._components):

                amounts = self._amounts[component.identifier]

                for amount in amounts:

                    if not isinstance(amount, Substance.ExactAmount):
                        continue

                    remaining_molecule_slots -= amount.value

            if remaining_molecule_slots < 0:

                raise ValueError(f'The required number of molecules {maximum_molecules - remaining_molecule_slots} '
                                 f'exceeds the provided maximum number ({maximum_molecules}).')

            for component in self._components:

                number_of_molecules[component.identifier] = 0

                for amount in self._amounts[component.identifier]:

                    number_of_molecules[component.identifier] += amount.to_number_of_molecules(remaining_molecule_slots,
                                                                                               tolerance)

            return number_of_molecules

        @staticmethod
        def calculate_aqueous_ionic_mole_fraction(ionic_strength):
            """Determines what mole fraction of ions is needed to yield
             an aqueous system of a given ionic strength.

            Parameters
            ----------
            ionic_strength: unit.Quantity
                The ionic string in units of molar.

            Returns
            -------
            float
                The mole fraction of ions.
            """

            # Taken from YANK:
            # https://github.com/choderalab/yank/blob/4dfcc8e127c51c20180fe6caeb49fcb1f21730c6/Yank/pipeline.py#L1869
            water_molarity = (998.23 * unit.gram / unit.litre) / (18.01528 * unit.gram / unit.mole)

            ionic_mole_fraction = ionic_strength / (ionic_strength + water_molarity)
            return ionic_mole_fraction

        def __getstate__(self):
            return {
                'components': self._components,
                'amounts': self._amounts
            }

        def __setstate__(self, state):
            self._components = state['components']
            self._amounts = state['amounts']

        def __str__(self):
            return self.identifier

        def __hash__(self):

            sorted_component_identifiers = [component.identifier for component in self._components]
            sorted_component_identifiers.sort()

            component_by_id = {component.identifier: component for component in self._components}

            string_hash_split = []

            for identifier in sorted_component_identifiers:

                component_role = component_by_id[identifier].role

                component_amounts = sorted(self._amounts[identifier], key=lambda x: type(x).__name__)
                amount_identifier = ''.join([component_amount.identifier for component_amount in component_amounts])

                string_hash_split.append(f'{identifier}_{component_role}_{amount_identifier}')

            string_hash = '|'.join(string_hash_split)

            return hash(string_hash)

        def __eq__(self, other):
            return isinstance(other, Substance) and hash(self) == hash(other)

        def __ne__(self, other):
            return not (self == other)