#     Copyright 2019, Kay Hayen, mailto:kay.hayen@gmail.com
#
#     Part of "Nuitka", an optimizing Python compiler that is compatible and
#     integrates with CPython, but also works on its own.
#
#     Licensed under the Apache License, Version 2.0 (the "License");
#     you may not use this file except in compliance with the License.
#     You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#     Unless required by applicable law or agreed to in writing, software
#     distributed under the License is distributed on an "AS IS" BASIS,
#     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#     See the License for the specific language governing permissions and
#     limitations under the License.
#
""" Reformulation of for loop statements.

Consult the developer manual for information. TODO: Add ability to sync
source code comments with developer manual sections.

"""

from nuitka.nodes.AssignNodes import (
    StatementAssignmentVariable,
    StatementReleaseVariable,
)
from nuitka.nodes.BuiltinIteratorNodes import (
    ExpressionAsyncIter,
    ExpressionAsyncNext,
    ExpressionBuiltinIter1,
)
from nuitka.nodes.BuiltinNextNodes import ExpressionBuiltinNext1
from nuitka.nodes.ComparisonNodes import ExpressionComparisonIs
from nuitka.nodes.ConditionalNodes import makeStatementConditional
from nuitka.nodes.ConstantRefNodes import makeConstantRefNode
from nuitka.nodes.LoopNodes import StatementLoop, StatementLoopBreak
from nuitka.nodes.StatementNodes import StatementsSequence
from nuitka.nodes.VariableRefNodes import ExpressionTempVariableRef
from nuitka.nodes.YieldNodes import ExpressionYieldFromWaitable

from .ReformulationAssignmentStatements import buildAssignmentStatements
from .ReformulationTryExceptStatements import makeTryExceptSingleHandlerNode
from .ReformulationTryFinallyStatements import makeTryFinallyStatement
from .TreeHelpers import (
    buildNode,
    buildStatementsNode,
    makeStatementsSequence,
    makeStatementsSequenceFromStatements,
    popBuildContext,
    pushBuildContext,
)


def _buildForLoopNode(provider, node, sync, source_ref):
    # The for loop is re-formulated according to developer manual. An iterator
    # is created, and looped until it gives StopIteration. The else block is
    # taken if a for loop exits normally, i.e. because of iterator
    # exhaustion. We do this by introducing an indicator variable.

    # We handle async and sync both here, leading to cases, pylint: disable=too-many-locals

    source = buildNode(provider, node.iter, source_ref)

    # Temporary variables, we need one for the iterator, and one for the current
    # value.
    temp_scope = provider.allocateTempScope("for_loop")

    tmp_iter_variable = provider.allocateTempVariable(
        temp_scope=temp_scope, name="for_iterator"
    )
    tmp_value_variable = provider.allocateTempVariable(
        temp_scope=temp_scope, name="iter_value"
    )

    else_block = buildStatementsNode(
        provider=provider,
        nodes=node.orelse if node.orelse else None,
        source_ref=source_ref,
    )

    if else_block is not None:
        tmp_break_indicator = provider.allocateTempVariable(
            temp_scope=temp_scope, name="break_indicator"
        )

        statements = [
            StatementAssignmentVariable(
                variable=tmp_break_indicator,
                source=makeConstantRefNode(constant=True, source_ref=source_ref),
                source_ref=source_ref,
            )
        ]
    else:
        statements = []

    statements.append(StatementLoopBreak(source_ref=source_ref))

    handler_body = makeStatementsSequence(
        statements=statements, allow_none=False, source_ref=source_ref
    )

    if sync:
        next_node = ExpressionBuiltinNext1(
            value=ExpressionTempVariableRef(
                variable=tmp_iter_variable, source_ref=source_ref
            ),
            source_ref=source_ref,
        )
    else:
        next_node = ExpressionYieldFromWaitable(
            expression=ExpressionAsyncNext(
                value=ExpressionTempVariableRef(
                    variable=tmp_iter_variable, source_ref=source_ref
                ),
                source_ref=source_ref,
            ),
            source_ref=source_ref,
        )

    statements = (
        makeTryExceptSingleHandlerNode(
            tried=StatementAssignmentVariable(
                variable=tmp_value_variable, source=next_node, source_ref=source_ref
            ),
            exception_name="StopIteration" if sync else "StopAsyncIteration",
            handler_body=handler_body,
            source_ref=source_ref,
        ),
        buildAssignmentStatements(
            provider=provider,
            node=node.target,
            source=ExpressionTempVariableRef(
                variable=tmp_value_variable, source_ref=source_ref
            ),
            source_ref=source_ref,
        ),
    )

    pushBuildContext("loop_body")
    statements += (
        buildStatementsNode(provider=provider, nodes=node.body, source_ref=source_ref),
    )
    popBuildContext()

    loop_body = makeStatementsSequence(
        statements=statements, allow_none=True, source_ref=source_ref
    )

    cleanup_statements = [
        StatementReleaseVariable(variable=tmp_value_variable, source_ref=source_ref),
        StatementReleaseVariable(variable=tmp_iter_variable, source_ref=source_ref),
    ]

    if else_block is not None:
        statements = [
            StatementAssignmentVariable(
                variable=tmp_break_indicator,
                source=makeConstantRefNode(constant=False, source_ref=source_ref),
                source_ref=source_ref,
            )
        ]
    else:
        statements = []

    if sync:
        iter_source = ExpressionBuiltinIter1(
            value=source, source_ref=source.getSourceReference()
        )
    else:
        iter_source = ExpressionYieldFromWaitable(
            expression=ExpressionAsyncIter(
                value=source, source_ref=source.getSourceReference()
            ),
            source_ref=source.getSourceReference(),
        )

    statements += [
        # First create the iterator and store it.
        StatementAssignmentVariable(
            variable=tmp_iter_variable, source=iter_source, source_ref=source_ref
        ),
        makeTryFinallyStatement(
            provider=provider,
            tried=StatementLoop(body=loop_body, source_ref=source_ref),
            final=StatementsSequence(
                statements=cleanup_statements, source_ref=source_ref
            ),
            source_ref=source_ref,
        ),
    ]

    if else_block is not None:
        statements += [
            makeStatementConditional(
                condition=ExpressionComparisonIs(
                    left=ExpressionTempVariableRef(
                        variable=tmp_break_indicator, source_ref=source_ref
                    ),
                    right=makeConstantRefNode(constant=True, source_ref=source_ref),
                    source_ref=source_ref,
                ),
                yes_branch=else_block,
                no_branch=None,
                source_ref=source_ref,
            )
        ]

        statements = (
            makeTryFinallyStatement(
                provider=provider,
                tried=statements,
                final=StatementReleaseVariable(
                    variable=tmp_break_indicator, source_ref=source_ref
                ),
                source_ref=source_ref,
            ),
        )

    return makeStatementsSequenceFromStatements(*statements)


def buildForLoopNode(provider, node, source_ref):
    return _buildForLoopNode(provider, node, True, source_ref)


def buildAsyncForLoopNode(provider, node, source_ref):
    return _buildForLoopNode(provider, node, False, source_ref)
