"""Class pmesh2domain - Converting .tsh files to domains


   Copyright 2004
   Ole Nielsen, Stephen Roberts, Duncan Gray, Christopher Zoppou
   Geoscience Australia
"""

import sys
import numpy as num


##
# @brief Convert a pmesh instance to a domain instance.
# @param mesh The pmesh instance to convert.
# @param DomainClass The class to instantiate and return.
# @return The converted pmesh instance (as a 'DomainClass' instance).
def pmesh_instance_to_domain_instance(mesh, DomainClass):
    """Convert a pmesh instance/object into a domain instance.

    Uses pmesh_to_domain_instance to convert a mesh file to a domain instance.
    """

    (vertex_coordinates, vertices, tag_dict, vertex_quantity_dict,
     tagged_elements_dict, geo_reference) = pmesh_to_domain(mesh_instance=mesh)

    # NOTE(Ole): This import cannot be at the module level
    #            due to mutual dependency with domain.py
    from anuga.abstract_2d_finite_volumes.domain import Domain

    # ensure that the required 'DomainClass' actually is an instance of Domain
    msg = ('The class %s is not a subclass of the generic domain class %s'
           % (DomainClass, Domain))
    assert issubclass(DomainClass, Domain), msg

    # instantiate the result class
    result = DomainClass(coordinates=vertex_coordinates,
                         vertices=vertices,
                         boundary=tag_dict,
                         tagged_elements=tagged_elements_dict,
                         geo_reference=geo_reference)

    # set the water stage to be the elevation
    if (vertex_quantity_dict.has_key('elevation') and
        not vertex_quantity_dict.has_key('stage')):
        vertex_quantity_dict['stage'] = vertex_quantity_dict['elevation']
    result.set_quantity_vertices_dict(vertex_quantity_dict)

    return result


##
# @brief Convert a mesh file to a Domain instance.
# @param file_name Name of the file to convert (TSH or MSH).
# @param DomainClass Class of return instance.
# @param use_cache True if caching is to be used.
# @param verbose True if this function is to be verbose.
# @return An instance of 'DomainClass' containing the file data.
def pmesh_to_domain_instance(file_name, DomainClass, use_cache=False,
                             verbose=False):
    """Converts a mesh file(.tsh or .msh), to a Domain instance.

    file_name is the name of the mesh file to convert, including the extension

    DomainClass is the Class that will be returned.
    It must be a subclass of Domain, with the same interface as domain.

    use_cache: True means that caching is attempted for the computed domain.    
    """

    if use_cache is True:
        from caching import cache
        result = cache(_pmesh_to_domain_instance, (file_name, DomainClass),
                       dependencies=[file_name], verbose=verbose)
    else:
        result = apply(_pmesh_to_domain_instance, (file_name, DomainClass))        
        
    return result


##
# @brief Convert a mesh file to a Domain instance.
# @param file_name Name of the file to convert (TSH or MSH).
# @param DomainClass Class of return instance.
# @return The DomainClass instance containing the file data.
def _pmesh_to_domain_instance(file_name, DomainClass):
    """Converts a mesh file(.tsh or .msh), to a Domain instance.

    Internal function. See public interface pmesh_to_domain_instance for details
    """
    
    (vertex_coordinates, vertices, tag_dict, vertex_quantity_dict,
     tagged_elements_dict, geo_reference) = pmesh_to_domain(file_name=file_name)

    # NOTE(Ole): This import cannot be at the module level due to mutual
    # dependency with domain.py
    from anuga.abstract_2d_finite_volumes.domain import Domain

    # ensure the required class is a subclass of Domain
    msg = ('The class %s is not a subclass of the generic domain class %s'
           % (DomainClass, Domain))
    assert issubclass(DomainClass, Domain), msg

    domain = DomainClass(coordinates = vertex_coordinates,
                         vertices = vertices,
                         boundary = tag_dict,
                         tagged_elements = tagged_elements_dict,
                         geo_reference = geo_reference )

    # FIXME (Ole): Is this really the right place to apply a default
    # value specific to the shallow water wave equation?
    # The 'assert' above indicates that any subclass of Domain is acceptable.
    # Suggestion - module shallow_water.py will eventually take care of this
    # (when I get around to it) so it should be removed from here.

    # This doesn't work on the domain instance.
    # This is still needed so -ve elevations don't cuase 'lakes'
    # The fixme we discussed was to only create a quantity when its values
    # are set.
    # I think that's the way to go still

    # set the water stage to be the elevation
    if (vertex_quantity_dict.has_key('elevation') and
        not vertex_quantity_dict.has_key('stage')):
        vertex_quantity_dict['stage'] = vertex_quantity_dict['elevation']
    domain.set_quantity_vertices_dict(vertex_quantity_dict)

    return domain


##
# @brief Convert pmesh file/instance to list(s) that can instantiate a Domain.
# @param file_name Path to file to convert.
# @param mesh_instance Instance to convert.
# @param use_cache True if we are to cache.
# @param verbose True if this function is to be verbose.
# @return ??
def pmesh_to_domain(file_name=None, mesh_instance=None, use_cache=False,
                    verbose=False):
    """Convert a pmesh file or a pmesh mesh instance to a bunch of lists
    that can be used to instanciate a domain object.

    use_cache: True means that caching is attempted for the computed domain.    
    """
 
    if use_cache is True:
        from caching import cache
        result = cache(_pmesh_to_domain, (file_name, mesh_instance),
                       dependencies=[file_name], verbose=verbose)

    else:
        result = apply(_pmesh_to_domain, (file_name, mesh_instance))        
        
    return result


##
# @brief Convert pmesh file/instance to list(s) that can instantiate a Domain.
# @param file_name Path to file to convert.
# @param mesh_instance Instance to convert.
# @param use_cache True if we are to cache.
# @param verbose True if this function is to be verbose.
# @return ??
def _pmesh_to_domain(file_name=None, mesh_instance=None, use_cache=False,
                     verbose=False):
    """Convert a pmesh file or a pmesh mesh instance to a bunch of lists
    that can be used to instantiate a domain object.
    """

    from load_mesh.loadASCII import import_mesh_file

    # get data from mesh instance or file
    if file_name is None:
        mesh_dict = mesh_instance.Mesh2IODict()
    else:
        mesh_dict = import_mesh_file(file_name)

    # extract required data from the mesh dictionary
    vertex_coordinates = mesh_dict['vertices']
    volumes = mesh_dict['triangles']
    vertex_quantity_dict = {}

    # num.transpose(None) gives scalar array of value None
    point_atts = mesh_dict['vertex_attributes']

    point_titles = mesh_dict['vertex_attribute_titles']
    geo_reference = mesh_dict['geo_reference']
    if point_atts is not None:
        point_atts = num.transpose(point_atts)
        for quantity, value_vector in map(None, point_titles, point_atts):
            vertex_quantity_dict[quantity] = value_vector
    tag_dict = pmesh_dict_to_tag_dict(mesh_dict)
    tagged_elements_dict = build_tagged_elements_dictionary(mesh_dict)

    return (vertex_coordinates, volumes, tag_dict, vertex_quantity_dict,
            tagged_elements_dict, geo_reference)


def build_tagged_elements_dictionary(mesh_dict):
    """Build the dictionary of element tags.

    tagged_elements is a dictionary of element arrays,
    keyed by tag: { (tag): [e1, e2, e3..] }
    """

    tri_atts = mesh_dict['triangle_tags']
    tagged_elements = {}
    if tri_atts is None:
       tagged_elements[''] = range(len(mesh_dict['triangles']))
    else:
        for tri_att_index in range(len(tri_atts)):
            tagged_elements.setdefault(tri_atts[tri_att_index],
                                       []).append(tri_att_index)

    return tagged_elements


def pmesh_dict_to_tag_dict(mesh_dict):
    """ Convert the pmesh dictionary (mesh_dict) description of boundary tags
    to a dictionary of tags, indexed with volume id and face number.
    """

    triangles = mesh_dict['triangles']
    sides = calc_sides(triangles)
    tag_dict = {}
    for seg, tag in map(None, mesh_dict['segments'], mesh_dict['segment_tags']):
        v1 = int(seg[0])
        v2 = int(seg[1])
        for key in [(v1,v2),(v2,v1)]:
            if sides.has_key(key) and tag <> "":
                #"" represents null.  Don't put these into the dictionary
                #this creates a dict of lists of faces, indexed by tag
                #tagged_edges.setdefault(tag,[]).append(sides[key])
                tag_dict[sides[key]] = tag

    return tag_dict


def calc_sides(triangles):
    '''Build dictionary mapping from sides (2-tuple of points)
    to left hand side neighbouring triangle
    '''

    sides = {}

    for id, triangle in enumerate(triangles):
        a = int(triangle[0])
        b = int(triangle[1])
        c = int(triangle[2])

        sides[a,b] = (id, 2) #(id, face)
        sides[b,c] = (id, 0) #(id, face)
        sides[c,a] = (id, 1) #(id, face)

    return sides