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#pylint: disable=no-else-return
"""The Python interface to the Relay reference interpreter."""
from __future__ import absolute_import

import numpy as np

import tvm._ffi
from tvm.runtime import container, Object
from tvm.ir import IRModule

from . import _backend
from .. import _make, analysis, transform
from ... import nd
from ..expr import Tuple, RefCreate, Call, Constant, GlobalVar, const
from ..function import Function
from ..scope_builder import ScopeBuilder


@tvm._ffi.register_object("relay.ConstructorValue")
class ConstructorValue(Object):
    def __init__(self, tag, fields, constructor):
        self.__init_handle_by_constructor__(
            _make.ConstructorValue, tag, fields, constructor)


@tvm._ffi.register_object("relay.RefValue")
class RefValue(Object):
    def __init__(self, value):
        self.__init_handle_by_constructor__(
            _make.RefValue, value)


def _arg_to_ast(mod, arg):
    if isinstance(arg, nd.NDArray):
        return Constant(arg.copyto(nd.cpu(0)))
    elif isinstance(arg, container.ADT):
        return Tuple([_arg_to_ast(mod, field) for field in arg])
    elif isinstance(arg, tuple):
        return Tuple([_arg_to_ast(mod, field) for field in arg])
    elif isinstance(arg, RefValue):
        return RefCreate(_arg_to_ast(mod, arg.value))
    elif isinstance(arg, ConstructorValue):
        return Call(mod.get_constructor(arg.tag),
                    [_arg_to_ast(mod, field) for field in arg.fields])
    elif isinstance(arg, np.ndarray):
        return Constant(nd.array(arg))
    elif isinstance(arg, Constant):
        return arg
    else:
        return const(arg)


class Executor(object):
    """An abstract interface for executing Relay programs."""

    def _convert_args(self, expr, args, kwargs):
        """
        Convert the combination of arguments and keyword arguments
        into a sequence of arguments that may be passed to
        a Relay evaluator.

        We first provide all positional arguments, and then attempt
        to fill in the remaining arguments using the keyword arguments. We
        map the keyword arguments to the corresponding parameters, if there
        is an ambiguity between positional and keyword arguments this
        procedure will raise an error.

        Parameters
        ----------
        expr: relay.Expr
            The expression to evaluate

        args: List[tvm.nd.NDArray]
            The arguments to pass to the evaluator.

        kwargs: Dict[str, tvm.NDArrray]
            The keyword arguments to pass to the evaluator.

        Returns:
            args: List[tvm.nd.NDArray]
                The new arguments with all keyword arguments placed in the correct slot.
        """
        assert expr is not None

        if not kwargs:
            return args

        if kwargs and not isinstance(expr, Function):
            raise Exception("can only supply keyword parameters for a "
                            "relay.Function, found {0}".format(expr))

        params = expr.params
        param_names = [p.name_hint for p in params]
        num_of_args = len(args)

        cargs = list(args)[:]
        for i, name in enumerate(param_names):
            if i < num_of_args:
                if kwargs.get(name):
                    raise Exception(
                        "duplicate argument supplied in "
                        "both positional args (at position: {0}), "
                        "and keyword argument (with name: {1})".format(i, name))
            else:
                cargs.append(kwargs[name])

        if len(cargs) != len(params):
            raise Exception(
                "insufficient arguments, expected "
                "{0}, provided {1}".format(len(cargs), len(params)))

        return tuple(cargs)

    def _make_executor(self, expr=None):
        """
        Construct a Python function that implements the evaluation
        of expression.

        Parameters
        ----------
        expr: Optional[relay.Expr]
            The Relay expression to execute.

        Returns
        -------
        executor: function,
            A Python function which implements the behavior of `expr`.
        """
        raise NotImplementedError()

    def evaluate(self, expr=None, binds=None):
        """
        Evaluate a Relay expression on the executor.

        Parameters
        ----------
        expr: Optional[tvm.relay.Expr]
            The expression to evaluate.

        binds: Optional[Map[tvm.relay.Var, tvm.relay.Expr]]
            Additional binding of free variable.

        Returns
        -------
        val : Union[function, Object]
            The evaluation result.
        """
        if binds:
            scope_builder = ScopeBuilder()
            for key, value in binds.items():
                scope_builder.let(key, _arg_to_ast(self.mod, value))
            scope_builder.ret(expr)
            expr = scope_builder.get()

        if not expr:
            return self._make_executor()

        if isinstance(expr, Function):
            assert not analysis.free_vars(expr)

        if isinstance(expr, (Function, GlobalVar)):
            return self._make_executor(expr)

        # normal expression evaluated by running a function.
        func = Function([], expr)
        return self._make_executor(func)()


class Interpreter(Executor):
    """
    Simple interpreter interface.

    Parameters
    ----------
    mod : tvm.IRModule
        The module to support the execution.

    ctx : tvmContext
        The runtime context to run the code on.

    target : tvm.Target
        The target option to build the function.
    """
    def __init__(self, mod, ctx, target):
        self.mod = mod
        self.ctx = ctx
        self.target = target

    def optimize(self):
        """Optimize functions in a module.

        Returns
        -------
        opt_mod : tvm.IRModule
            The optimized module.
        """
        seq = transform.Sequential([transform.SimplifyInference(),
                                    transform.FuseOps(0),
                                    transform.ToANormalForm(),
                                    transform.InferType()])
        return seq(self.mod)

    def _make_executor(self, expr=None):
        if expr is None or isinstance(expr, GlobalVar):
            assert self.mod is not None
        def _interp_wrapper(*args, **kwargs):
            if expr is None:
                args = self._convert_args(self.mod["main"], args, kwargs)
            else:
                args = self._convert_args(expr, args, kwargs)

            relay_args = []
            for arg in args:
                relay_args.append(_arg_to_ast(self.mod, arg))

            # Set the entry function for the module.
            if expr is None:
                pass
            elif isinstance(expr, GlobalVar):
                self.mod["main"] = self.mod[expr]
            else:
                assert isinstance(expr, Function)
                func = Function([], Call(expr, relay_args))
                relay_args = []
                if self.mod:
                    self.mod["main"] = func
                else:
                    self.mod = IRModule.from_expr(func)

            mod = self.optimize()
            opt_expr = Call(mod["main"], relay_args)
            _intrp = _backend.CreateInterpreter(mod, self.ctx, self.target)
            return _intrp(opt_expr)
        return _interp_wrapper
