import torch.jit
import inspect
import textwrap
# this file is for generating documentation using sphinx autodoc
# > help(torch.jit.supported_ops) will also give a nice listed of the
# supported ops programmatically

def _hidden(name):
    return name.startswith('_') and not name.startswith('__')

def _emit_type(type):
    return str(type)

def _emit_arg(indent, i, arg):
    v = "{} : {}".format(arg.name, _emit_type(arg.type))
    default = arg.default_value
    if default is not None:
        v = "{}={}".format(v, str(default))
    if i > 0:
        v = "\n{}{}".format(" " * indent, v)
    return v

def _emit_args(indent, arguments):
    return ",".join(_emit_arg(indent, i, arg) for i, arg in enumerate(arguments))

def _emit_ret(ret):
    return _emit_type(ret.type)

def _emit_rets(returns):
    if len(returns) == 1:
        return _emit_ret(returns[0])
    return "Tuple[{}]".format(", ".join(_emit_ret(r) for r in returns))

def _emit_schema(mod, name, schema, arg_start=0, padding=4):
    if mod is None:
        qualified_name = name
    else:
        qualified_name = "{}.{}".format(mod, name)
    schema = "{}({}) -> {}".format(qualified_name,
                                   _emit_args(len(qualified_name) + 1 + padding, schema.arguments[arg_start:]),
                                   _emit_rets(schema.returns))
    return schema

def _get_tensor_ops():
    def is_tensor_method(schema):
        if len(schema.arguments) == 0:
            return False
        self = schema.arguments[0]
        if self.name != 'self':
            return False
        if not self.type.isSubtypeOf(torch._C.TensorType.get()):
            return False
        return True

    methods = []
    # discover methods
    for elem in dir(torch.Tensor):
        if not _hidden(elem):
            schemas = torch._C._jit_get_schemas_for_operator("aten::" + elem)
            for schema in schemas:
                if is_tensor_method(schema):
                    methods.append(_emit_schema('Tensor', elem, schema, arg_start=1))

    return "Supported Tensor Methods", methods

def _get_nn_functional_ops():
    functions = []

    # Iterate over torch.nn.functional
    mod = torch.nn.functional
    name = mod.__name__
    for elem in dir(torch.nn.functional):
        attr = getattr(mod, elem)
        if not inspect.isfunction(attr) or _hidden(elem[0]):
            # Ignore non-functions and internal methods
            continue

        if 'torch.nn.functional' not in inspect.getmodule(attr).__name__:
            # Ignore functions from outside torch.nn.functional
            continue

        try:
            # compile fn, get schema
            scripted = torch.jit.script(attr)
            schema = scripted.schema
            functions.append(_emit_schema(name, elem, schema))
        except:  # noqa
            # Skip interpolate / boolean dispatched things
            pass

    # Iterate over modules that we know contain a lot of builtins
    for mod in torch.jit._modules_containing_builtins:
        name = mod.__name__
        for elem in dir(mod):
            builtin = torch.jit._find_builtin(getattr(mod, elem))
            if builtin is not None:
                schemas = torch._C._jit_get_schemas_for_operator(builtin)
                for schema in schemas:
                    # remove _tan but not __and__
                    if not _hidden(elem):
                        functions.append(_emit_schema(name, elem, schema))
    return "Supported PyTorch Functions", functions

def _get_builtins_helper():
    builtins = []
    for fn, _builtin_name in torch.jit._builtin_ops:
        mod = inspect.getmodule(fn)
        if _hidden(fn.__name__) or _hidden(fn.__qualname__) or _hidden(mod.__name__):
            # skip internal-only methods
            continue

        if 'torch._C' in mod.__name__:
            continue

        builtins.append((fn, _builtin_name))

    return builtins

def _is_math_fn(fn):
    mod = inspect.getmodule(fn)
    return mod.__name__ == 'math'


def _get_torchscript_builtins():
    functions = []
    builtins = filter(lambda fn: not _is_math_fn(fn[0]), _get_builtins_helper())
    builtins = list(builtins)
    # Iterate over the specially added builtins
    for fn, _builtin_name in builtins:
        mod = inspect.getmodule(fn)
        builtin = torch.jit._find_builtin(fn)
        if builtin is not None:
            schemas = torch._C._jit_get_schemas_for_operator(builtin)
            for schema in schemas:
                functions.append(_emit_schema(mod.__name__, fn.__name__, schema))
                pass

    return "TorchScript Builtin Functions", functions


def _get_math_builtins():
    functions = []
    builtins = filter(lambda fn: _is_math_fn(fn[0]), _get_builtins_helper())
    builtins = list(builtins)
    # Iterate over the specially added builtins
    for fn, _builtin_name in builtins:
        mod = inspect.getmodule(fn)
        builtin = torch.jit._find_builtin(fn)
        if builtin is not None:
            schemas = torch._C._jit_get_schemas_for_operator(builtin)
            for schema in schemas:
                schema = _emit_schema(mod.__name__, fn.__name__, schema)
                if 'Tensor' in schema:
                    # Skip Tensor ops that have the same name as math functions
                    # (they will show up in the tensor methods section)
                    continue
                functions.append(schema)
                pass

    return "``math`` Module", functions


def _get_global_builtins():
    # Taken from the 'globals' map in torch/csrc/jit/script/compiler.cpp
    supported_builtins = [
        'print',
        'tuple',
        'float',
        'int',
        'bool',
        'str',
        'getattr',
        'hasattr',
        'isinstance',
        'len',
        'hex',
        'oct',
        'round',
        'hash',
        'min',
        'max',
        'abs',
        'all',
        'divmod',
        'list',
        'ord',
        'chr',
        'bin',
        'range',
        'zip',
        'enumerate',
        'sorted',
    ]

    op_renames = {
        'bool': 'aten::Bool',
        'int': 'aten::Int',
        'float': 'aten::Float',
        'abs': 'prim::abs',
        'max': 'prim::max',
        'min': 'prim::min',
        'range': 'fake::does_not_exist',
    }

    schemaless_op_explanations = {
        'print': 'Print any value',
        'tuple': 'Lists cannot be converted to tuples with this method since their size is not statically known',
        'getattr': 'Attribute name must be a literal string',
        'hasattr': 'Attribute name must be a literal string',
        'isinstance': 'Result is static',
        'zip': 'Arguments must be iterable. See :ref:`Iterables <jit_iterables>` for details.',
        'enumerate': 'Arguments must be iterable. See :ref:`Iterables <jit_iterables>` for details.',
        'range': 'Can only be used as an iterator in a for loop',
    }

    magic_methods = [
        ('float', '__float__'),
        ('int', '__int__'),
        ('bool', '__bool__'),
        ('str', '__str__'),
        ('len', '__len__'),
        ('hex', '__hex__'),
        ('oct', '__oct__'),
    ]

    magic_methods_rows = []
    for fn, magic_method in magic_methods:
        magic_methods_rows.append('":any:`{}`", "``{}``"'.format(fn, magic_method))

    schematized_ops = []
    schemaless_ops = []

    for fn in supported_builtins:
        op_name = 'aten::{}'.format(fn)
        if fn in op_renames:
            op_name = op_renames[fn]
        schemas = torch._C._jit_get_schemas_for_operator(op_name)
        for s in schemas:
            schematized_ops.append(_emit_schema(None, fn, s, padding=0))
        if len(schemas) > 0:
            schematized_ops.append('')
        else:
            table_row = '":any:`{}`", "{}"'.format(fn, schemaless_op_explanations[fn])
            schemaless_ops.append(table_row)

    schematized_ops = '\n'.join(schematized_ops)
    schemaless_ops = '\n'.join(schemaless_ops)
    magic_methods_rows = '\n'.join(magic_methods_rows)
    schematized_ops = textwrap.indent(schematized_ops, '\t')
    schemaless_ops = textwrap.indent(schemaless_ops, '\t')
    magic_methods_rows = textwrap.indent(magic_methods_rows, '\t')
    section = """
The functions in the following table are supported but do not have a static schema

.. csv-table::
    :header: "Function", "Note"

{}

The following functions will use the corresponding magic method on :any:`TorchScript classes`

.. csv-table::
    :header: "Function", "Magic Method"

{}

These built-in functions do have a schema

.. rst-class:: codeblock-height-limiter

::

{}
    """.format(schemaless_ops, magic_methods_rows, schematized_ops)

    return "Python Built-in Functions", section


def _list_supported_ops():
    def emit_block(decls):
        return '\n.. rst-class:: codeblock-height-limiter\n\n::\n\n{}\n'.format(''.join('    {}\n\n'.format(d) for d in decls))

    body = ''
    op_gathering_fns = (
        _get_tensor_ops,
        _get_nn_functional_ops,
        _get_torchscript_builtins,
        _get_global_builtins,
        _get_math_builtins,
    )
    for fn in op_gathering_fns:
        header, items = fn()
        link_target = header.replace('`', '').replace('-', '').lower().replace(' ', '-')
        if isinstance(items, str):
            section = "{}\n{}\n{}\n".format(header, '~' * len(header), items)
        else:
            section = "{}\n{}\n{}".format(header, '~' * len(header), emit_block(items))
        section = '.. _{}:'.format(link_target) + '\n\n' + section
        body += section

    return body

__doc__ = _list_supported_ops()
