"""Classes and functions for batching multiple heterographs together."""
from collections.abc import Iterable

from . import backend as F
from . import heterograph_index
from .base import ALL, is_all
from .frame import FrameRef, Frame
from .heterograph import DGLHeteroGraph

__all__ = ['BatchedDGLHeteroGraph', 'unbatch_hetero', 'batch_hetero']

class BatchedDGLHeteroGraph(DGLHeteroGraph):
    """Class for batched DGLHeteroGraphs.

    A :class:`BatchedDGLHeteroGraph` basically merges a list of small graphs into a giant
    graph so that one can perform message passing and readout over a batch of graphs
    simultaneously.

    For a given node/edge type, the nodes/edges are re-indexed with a new id in the
    batched graph with the rule below:

    ======  ==========  ========================  ===  ==========================
    item    Graph 1     Graph 2                   ...  Graph k
    ======  ==========  ========================  ===  ==========================
    raw id  0, ..., N1       0, ..., N2           ...  ..., Nk
    new id  0, ..., N1  N1 + 1, ..., N1 + N2 + 1  ...  ..., N1 + ... + Nk + k - 1
    ======  ==========  ========================  ===  ==========================

    To modify the features in :class:`BatchedDGLHeteroGraph` has no effect on the original
    graphs. See the examples below about how to work around.

    Parameters
    ----------
    gidx : HeteroGraphIndex
        Graph index object.
    ntypes : list of str, pair of list of str
        Node type list. ``ntypes[i]`` stores the name of node type i.
        If a pair is given, the graph created is a uni-directional bipartite graph,
        and its SRC node types and DST node types are given as in the pair.
    etypes : list of str
        Edge type list. ``etypes[i]`` stores the name of edge type i.
    node_frames : list of FrameRef, optional
        Node feature storage. If None, empty frame is created.
        Otherwise, ``node_frames[i]`` stores the node features
        of node type i. (default: None)
    edge_frames : list of FrameRef, optional
        Edge feature storage. If None, empty frame is created.
        Otherwise, ``edge_frames[i]`` stores the edge features
        of edge type i. (default: None)
    batch_size : int
        Number of heterogeneous graphs in the batch.
    batch_num_nodes : list of list
        batch_num_nodes[i][j] gives the number of nodes of the i-th type
        in the j-th graph.
    batch_num_edges : list of list
        batch_num_edges[i][j] gives the number of edges of the i-th type
        in the j-th graph.

    Examples
    --------

    >>> import dgl
    >>> import torch as th

    **Example 1**

    We start with a simple example.

    >>> # Create the first graph and set features for nodes of type 'user'
    >>> g1 = dgl.heterograph({('user', 'plays', 'game'): [(0, 0), (1, 0)]})
    >>> g1.nodes['user'].data['h1'] = th.tensor([[0.], [1.]])
    >>> # Create the second graph and set features for nodes of type 'user'
    >>> g2 = dgl.heterograph({('user', 'plays', 'game'): [(0, 0)]})
    >>> g2.nodes['user'].data['h1'] = th.tensor([[0.]])
    >>> # Batch the graphs
    >>> bg = dgl.batch_hetero([g1, g2])

    With the batching operation, the nodes and edges are re-indexed.

    >>> bg.nodes('user')
    tensor([0, 1, 2])

    By default, we also copy and concatenate all the node and edge features.

    >>> bg.nodes['user'].data['h1']
    tensor([[0.],
            [1.],
            [0.]])

    **Example 2**

    We will now see a more complex example and the
    various operations one can play with a batched graph.

    >>> g1 = dgl.heterograph({
    ...    ('user', 'follows', 'user'): [(0, 1), (1, 2)],
    ...    ('user', 'plays', 'game'): [(0, 0), (1, 0)]
    ... })
    >>> g1.nodes['user'].data['h1'] = th.tensor([[0.], [1.], [2.]])
    >>> g1.nodes['user'].data['h2'] = th.tensor([[3.], [4.], [5.]])
    >>> g1.nodes['game'].data['h1'] = th.tensor([[0.]])
    >>> g1.edges['plays'].data['h1'] = th.tensor([[0.], [1.]])

    >>> g2 = dgl.heterograph({
    ...    ('user', 'follows', 'user'): [(0, 1), (1, 2)],
    ...    ('user', 'plays', 'game'): [(0, 0), (1, 0)]
    ... })
    >>> g2.nodes['user'].data['h1'] = th.tensor([[0.], [1.], [2.]])
    >>> g2.nodes['user'].data['h2'] = th.tensor([[3.], [4.], [5.]])
    >>> g2.nodes['game'].data['h1'] = th.tensor([[0.]])
    >>> g2.edges['plays'].data['h1'] = th.tensor([[0.], [1.]])

    Merge two :class:`~dgl.DGLHeteroGraph` objects into one :class:`BatchedDGLHeteroGraph` object.
    When merging a list of graphs, we can choose to include only a subset of the attributes.

    >>> # For edge types, only canonical edge types are allowed to avoid ambiguity.
    >>> bg = dgl.batch_hetero([g1, g2], node_attrs={'user': ['h1', 'h2'], 'game': None},
    ...                       edge_attrs={('user', 'plays', 'game'): 'h1'})
    >>> list(bg.nodes['user'].data.keys())
    ['h1', 'h2']
    >>> list(bg.nodes['game'].data.keys())
    []
    >>> list(bg.edges['follows'].data.keys())
    []
    >>> list(bg.edges['plays'].data.keys())
    ['h1']

    We can get a brief summary of the graphs that constitute the batched graph.

    >>> bg.batch_size
    2
    >>> bg.batch_num_nodes('user')
    [3, 3]
    >>> bg.batch_num_edges(('user', 'plays', 'game'))
    [2, 2]

    Updating the attributes of the batched graph has no effect on the original graphs.

    >>> bg.nodes['game'].data['h1'] = th.tensor([[1.], [1.]])
    >>> g2.nodes['game'].data['h1']
    tensor([[0.]])

    Instead, we can decompose the batched graph back into a list of graphs and use them
    to replace the original graphs.

    >>> g3, g4 = dgl.unbatch_hetero(bg) # returns a list of DGLHeteroGraph objects
    >>> g4.nodes['game'].data['h1']
    tensor([[1.]])
    """
    def __init__(self,
                 gidx,
                 ntypes,
                 etypes,
                 node_frames,
                 edge_frames,
                 batch_size,
                 batch_num_nodes,
                 batch_num_edges):
        super(BatchedDGLHeteroGraph, self).__init__(gidx=gidx,
                                                    ntypes=ntypes,
                                                    etypes=etypes,
                                                    node_frames=node_frames,
                                                    edge_frames=edge_frames)

        # extra members
        self._batch_size = batch_size
        self._batch_num_nodes = batch_num_nodes
        self._batch_num_edges = batch_num_edges

    @property
    def batch_size(self):
        """Number of graphs in this batch.

        Returns
        -------
        int
            Number of graphs in this batch."""
        return self._batch_size

    def batch_num_nodes(self, ntype=None):
        """Return the numbers of nodes of the given type for all heterographs in the batch.

        Parameters
        ----------
        ntype : str, optional
            The node type. Can be omitted if there is only one node type
            in the graph. (Default: None)

        Returns
        -------
        list of int
            The ith element gives the number of nodes of the specified type in the ith graph.

        Examples
        --------

        >>> g1 = dgl.heterograph({
        ...      ('user', 'follows', 'user'): [(0, 1), (1, 2)],
        ...      ('user', 'plays', 'game'): [(0, 0), (1, 0), (2, 1), (3, 1)]
        ...      })
        >>> g2 = dgl.heterograph({
        ...      ('user', 'follows', 'user'): [(0, 1), (1, 2)],
        ...      ('user', 'plays', 'game'): [(0, 0), (1, 0), (2, 1)]
        ...      })
        >>> bg = dgl.batch_hetero([g1, g2])
        >>> bg.batch_num_nodes('user')
        [4, 3]
        >>> bg.batch_num_nodes('game')
        [2, 2]
        """
        return self._batch_num_nodes[self.get_ntype_id(ntype)]

    def batch_num_edges(self, etype=None):
        """Return the numbers of edges of the given type for all heterographs in the batch.

        Parameters
        ----------
        etype : str or tuple of str, optional
            The edge type. Can be omitted if there is only one edge type
            in the graph.

        Returns
        -------
        list of int
            The ith element gives the number of edges of the specified type in the ith graph.

        Examples
        --------

        >>> g1 = dgl.heterograph({
        ...      ('user', 'follows', 'user'): [(0, 1), (1, 2)],
        ...      ('user', 'follows', 'developer'): [(0, 1), (1, 2)],
        ...      ('user', 'plays', 'game'): [(0, 0), (1, 0), (2, 1), (3, 1)]
        ...      })
        >>> g2 = dgl.heterograph({
        ...      ('user', 'follows', 'user'): [(0, 1), (1, 2)],
        ...      ('user', 'follows', 'developer'): [(0, 1), (1, 2)],
        ...      ('user', 'plays', 'game'): [(0, 0), (1, 0), (2, 1)]
        ...      })
        >>> bg = dgl.batch_hetero([g1, g2])
        >>> bg.batch_num_edges('plays')
        [4, 3]
        >>> # 'follows' is ambiguous and we use ('user', 'follows', 'user') instead.
        >>> bg.batch_num_edges(('user', 'follows', 'user'))
        [2, 2]
        """
        return self._batch_num_edges[self.get_etype_id(etype)]

    def to(self, ctx, **kwargs):  # pylint: disable=invalid-name
        """Move ndata, edata and graph structure to the targeted device context (cpu/gpu).

        Parameters
        ----------
        ctx : Framework-specific device context object
            The context to move data to.
        kwargs : Key-word arguments.
            Key-word arguments fed to the framework copy function.

        Returns
        -------
        g : BatchedDGLHeteroGraph
          Moved BatchedDGLHeteroGraph of the targeted mode.

        Examples
        --------
        The following example uses PyTorch backend.

        >>> # Create the first graph and set features for nodes of type 'user'
        >>> g1 = dgl.heterograph({('user', 'plays', 'game'): [(0, 0), (1, 0)]})
        >>> g1.nodes['user'].data['h1'] = th.tensor([[0.], [1.]])
        >>> # Create the second graph and set features for nodes of type 'user'
        >>> g2 = dgl.heterograph({('user', 'plays', 'game'): [(0, 0)]})
        >>> g2.nodes['user'].data['h1'] = th.tensor([[0.]])
        >>> # Batch the graphs
        >>> bg = dgl.batch_hetero([g1, g2])

        >>> # Move the graph topology and features to GPU
        >>> bg1 = bg.to(torch.device('cuda:0'))
        >>> print(bg1.device)
        device(type='cuda', index=0)
        >>> print(bg.device)
        device(type='cpu')
        """
        new_nframes = []
        for nframe in self._node_frames:
            new_feats = {k : F.copy_to(feat, ctx) for k, feat in nframe.items()}
            new_nframes.append(FrameRef(Frame(new_feats, num_rows=nframe.num_rows)))
        new_eframes = []
        for eframe in self._edge_frames:
            new_feats = {k : F.copy_to(feat, ctx) for k, feat in eframe.items()}
            new_eframes.append(FrameRef(Frame(new_feats, num_rows=eframe.num_rows)))
        # TODO(minjie): replace the following line with the commented one to enable GPU graph.
        new_gidx = self._graph
        #new_gidx = self._graph.copy_to(utils.to_dgl_context(ctx))

        return BatchedDGLHeteroGraph(gidx=new_gidx,
                                     ntypes=self.ntypes,
                                     etypes=self.etypes,
                                     node_frames=new_nframes,
                                     edge_frames=new_eframes,
                                     batch_size=self.batch_size,
                                     batch_num_nodes=self._batch_num_nodes,
                                     batch_num_edges=self._batch_num_edges)

def unbatch_hetero(graph):
    """Return the list of heterographs in this batch.

    Parameters
    ----------
    graph : BatchedDGLHeteroGraph
        The batched heterograph.

    Returns
    -------
    list
        A list of :class:`~dgl.BatchedDGLHeteroGraph` objects whose attributes are
        obtained by partitioning the attributes of the :attr:`graph`. The length of
        the list is the same as the batch size of :attr:`graph`.

    Notes
    -----
    Unbatching will break each field tensor of the batched graph into smaller
    partitions.

    For simpler tasks such as node/edge state aggregation, try to slice graphs along
    edge types and use readout functions.

    See Also
    --------
    batch_hetero
    """
    assert isinstance(graph, BatchedDGLHeteroGraph), \
        'Expect the input to be of type BatchedDGLHeteroGraph, got type {}'.format(type(graph))
    bsize = graph.batch_size
    bnn_all_types = graph._batch_num_nodes
    bne_all_types = graph._batch_num_edges
    ntypes = graph._ntypes
    etypes = graph._etypes
    node_frames = [[FrameRef(Frame(num_rows=bnn_all_types[tid][i])) for tid in range(len(ntypes))]
                   for i in range(bsize)]
    edge_frames = [[FrameRef(Frame(num_rows=bne_all_types[tid][i])) for tid in range(len(etypes))]
                   for i in range(bsize)]
    for tid in range(len(ntypes)):
        for attr, col in graph._node_frames[tid].items():
            col_splits = F.split(col, bnn_all_types[tid], dim=0)
            for i in range(bsize):
                node_frames[i][tid][attr] = col_splits[i]
    for tid in range(len(etypes)):
        for attr, col in graph._edge_frames[tid].items():
            col_splits = F.split(col, bne_all_types[tid], dim=0)
            for i in range(bsize):
                edge_frames[i][tid][attr] = col_splits[i]
    unbatched_graph_indices = heterograph_index.disjoint_partition(
        graph._graph, bnn_all_types, bne_all_types)
    return [DGLHeteroGraph(gidx=unbatched_graph_indices[i],
                           ntypes=ntypes,
                           etypes=etypes,
                           node_frames=node_frames[i],
                           edge_frames=edge_frames[i]) for i in range(bsize)]

def batch_hetero(graph_list, node_attrs=ALL, edge_attrs=ALL):
    """Batch a collection of :class:`~dgl.DGLHeteroGraph` and return a
    :class:`BatchedDGLHeteroGraph` object that is independent of the :attr:`graph_list`.

    Parameters
    ----------
    graph_list : iterable
        A collection of :class:`~dgl.DGLHeteroGraph` to be batched.
    node_attrs : None or dict
        The node attributes to be batched. If ``None``, the resulted graph will not have
        features. If ``dict``, it maps str to str or iterable. The keys represent names of
        node types and the values represent the node features to be batched for the
        corresponding type. By default, we use all features for all types of nodes.
    edge_attrs : None or dict
        Same as for the case of :attr:`node_attrs`.

    Returns
    -------
    BatchedDGLHeteroGraph
        One single batched heterograph

    See Also
    --------
    BatchedDGLHeteroGraph
    unbatch_hetero
    """
    # Sanity check. Make sure all graphs have the same node/edge types, in the same order.
    ref_canonical_etypes = graph_list[0].canonical_etypes
    ref_ntypes = graph_list[0].ntypes
    ref_etypes = graph_list[0].etypes
    for i in range(1, len(graph_list)):
        g_i = graph_list[i]
        assert g_i.ntypes == ref_ntypes, \
            'The node types of graph {:d} and {:d} should be the same.'.format(0, i)
        assert g_i.canonical_etypes == ref_canonical_etypes, \
            'The canonical edge types of graph {:d} and {:d} should be the same.'.format(0, i)

    # Sanity check. Make sure all graphs have same node/edge features in terns of name, size
    # and dtype if the number of nodes is nonzero.
    ref_node_feats = dict()
    for nty in ref_ntypes:
        for i, graph in enumerate(graph_list):
            # No nodes, skip it
            if graph.number_of_nodes(nty) == 0:
                continue
            # Use this for reference of feature names, shape and dtype
            if nty not in ref_node_feats:
                ref_node_feats[nty] = (i, graph.node_attr_schemes(nty))
                continue
            # Name check
            assert set(ref_node_feats[nty][1].keys()) == \
                   set(graph.node_attr_schemes(nty).keys()), \
                'The node features of graph {:d} and {:d} for node type {} should be the ' \
                'same.'.format(ref_node_feats[nty][0], i, nty)
            # Size and dtype check
            for nfeats in ref_node_feats[nty][1].keys():
                assert ref_node_feats[nty][1][nfeats] == \
                       graph.node_attr_schemes(nty)[nfeats], \
                    'For graph {:d} and {:d}, the size and dtype for feature {} of ' \
                    '{}-typed nodes should be the same.'.format(
                        ref_node_feats[nty][0], i, nfeats, nty)

    ref_edge_feats = dict()
    for ety in ref_canonical_etypes:
        for i, graph in enumerate(graph_list):
            # No edges, skip it
            if graph.number_of_edges(ety) == 0:
                continue
            # Use this for reference of feature names, shape and dtype
            if ety not in ref_edge_feats:
                ref_edge_feats[ety] = (i, graph.edge_attr_schemes(ety))
                continue
            # Name check
            assert set(ref_edge_feats[ety][1].keys()) == \
                   set(graph.edge_attr_schemes(ety).keys()), \
                'The edge features of graph {:d} and {:d} for edge type {} should be the ' \
                'same.'.format(ref_edge_feats[ety][0], i, ety)
            # Size and dtype check
            for efeats in ref_edge_feats[ety][1].keys():
                assert ref_edge_feats[ety][1][efeats] == \
                       graph.edge_attr_schemes(ety)[efeats], \
                    'For graph {:d} and {:d}, the size and dtype for feature {} of ' \
                    '{}-typed edges should be the same.'.format(
                        ref_edge_feats[ety][0], i, efeats, ety)

    def _init_attrs(types, attrs, mode):
        formatted_attrs = {t: [] for t in types}
        if is_all(attrs):
            for typ in types:
                if mode == 'node':
                    # Handle the case where the nodes of a type have no features
                    formatted_attrs[typ] = list(ref_node_feats.get(
                        typ, (None, dict()))[1].keys())
                elif mode == 'edge':
                    # Handle the case where the edges of a type have no features
                    formatted_attrs[typ] = list(ref_edge_feats.get(
                        typ, (None, dict()))[1].keys())
        elif isinstance(attrs, dict):
            for typ, v in attrs.items():
                if isinstance(v, str):
                    formatted_attrs[typ] = [v]
                elif isinstance(v, Iterable):
                    formatted_attrs[typ] = list(v)
                elif v is not None:
                    raise ValueError('Expected {} attrs for type {} to be str '
                                     'or iterable, got {}'.format(mode, typ, type(v)))
        elif attrs is not None:
            raise ValueError('Expected {} attrs to be of type None or dict,'
                             'got type {}'.format(mode, type(attrs)))
        return formatted_attrs

    node_attrs = _init_attrs(ref_ntypes, node_attrs, 'node')
    edge_attrs = _init_attrs(ref_canonical_etypes, edge_attrs, 'edge')

    node_frames = []
    for tid, typ in enumerate(ref_ntypes):
        if len(node_attrs[typ]) == 0:
            # Emtpy frames will be created when we instantiate a DGLHeteroGraph.
            node_frames.append(None)
        else:
            # NOTE: following code will materialize the columns of the input graphs.
            cols = {key: F.cat([gr._node_frames[tid][key] for gr in graph_list
                                if gr.number_of_nodes(typ) > 0], dim=0)
                    for key in node_attrs[typ]}
            node_frames.append(FrameRef(Frame(cols)))

    edge_frames = []
    for tid, typ in enumerate(ref_canonical_etypes):
        if len(edge_attrs[typ]) == 0:
            # Emtpy frames will be created when we instantiate a DGLHeteroGraph.
            edge_frames.append(None)
        else:
            # NOTE: following code will materialize the columns of the input graphs.
            cols = {key: F.cat([gr._edge_frames[tid][key] for gr in graph_list
                                if gr.number_of_edges(typ) > 0], dim=0)
                    for key in edge_attrs[typ]}
            edge_frames.append(FrameRef(Frame(cols)))

    # Create graph index for the batched graph
    metagraph = graph_list[0]._graph.metagraph
    batched_index = heterograph_index.disjoint_union(
        metagraph, [g._graph for g in graph_list])

    batch_size = 0
    # Store number of nodes/edge based on the id of node/edge types as we need
    # to handle both edge type and canonical edge type.
    batch_num_nodes = [[] for _ in range(len(ref_ntypes))]
    batch_num_edges = [[] for _ in range(len(ref_etypes))]

    for grh in graph_list:
        if isinstance(grh, BatchedDGLHeteroGraph):
            # Handle input graphs that are already batched
            batch_size += grh._batch_size
            for ntype_id in range(len(ref_ntypes)):
                batch_num_nodes[ntype_id].extend(grh._batch_num_nodes[ntype_id])
            for etype_id in range(len(ref_etypes)):
                batch_num_edges[etype_id].extend(grh._batch_num_edges[etype_id])
        else:
            batch_size += 1
            for ntype_id in range(len(ref_ntypes)):
                batch_num_nodes[ntype_id].append(grh._graph.number_of_nodes(ntype_id))
            for etype_id in range(len(ref_etypes)):
                batch_num_edges[etype_id].append(grh._graph.number_of_edges(etype_id))

    return BatchedDGLHeteroGraph(gidx=batched_index,
                                 ntypes=ref_ntypes,
                                 etypes=ref_etypes,
                                 node_frames=node_frames,
                                 edge_frames=edge_frames,
                                 batch_size=batch_size,
                                 batch_num_nodes=batch_num_nodes,
                                 batch_num_edges=batch_num_edges)
