"""Fixer for except statements with named exceptions.

The following cases will be converted:

- "except E, T:" where T is a name:

    except E as T:

- "except E, T:" where T is not a name, tuple or list:

        except E as t:

            T = t

    This is done because the target of an "except" clause must be a

    name.

- "except E, T:" where T is a tuple or list literal:

        except E as t:

            T = t.args

"""

# Author: Collin Winter

# Local imports

from .. import pytree

from ..pgen2 import token

from .. import fixer_base

from ..fixer_util import Assign, Attr, Name, is_tuple, is_list

def find_excepts(nodes):

    for i, n in enumerate(nodes):

        if isinstance(n, pytree.Node):

            if n.children[0].value == 'except':

                yield (n, nodes[i+2])

class FixExcept(fixer_base.BaseFix):

    PATTERN = """

    try_stmt< 'try' ':' suite

                  cleanup=(except_clause ':' suite)+

                  tail=(['except' ':' suite]

                        ['else' ':' suite]

                        ['finally' ':' suite]) >

    """

    def transform(self, node, results):

        syms = self.syms

        tail = [n.clone() for n in results["tail"]]

        try_cleanup = [ch.clone() for ch in results["cleanup"]]

        for except_clause, e_suite in find_excepts(try_cleanup):

            if len(except_clause.children) == 4:

                (E, comma, N) = except_clause.children[1:4]

                comma.replace(Name("as", prefix=" "))

                if N.type != token.NAME:

                    # Generate a new N for the except clause

                    new_N = Name(self.new_name(), prefix=" ")

                    target = N.clone()

                    target.set_prefix("")

                    N.replace(new_N)

                    new_N = new_N.clone()

                    # Insert "old_N = new_N" as the first statement in

                    #  the except body. This loop skips leading whitespace

                    #  and indents

                    #TODO(cwinter) suite-cleanup

                    suite_stmts = e_suite.children

                    for i, stmt in enumerate(suite_stmts):

                        if isinstance(stmt, pytree.Node):

                            break

                    # The assignment is different if old_N is a tuple or list

                    # In that case, the assignment is old_N = new_N.args

                    if is_tuple(N) or is_list(N):

                        assign = Assign(target, Attr(new_N, Name('args')))

                    else:

                        assign = Assign(target, new_N)

                    #TODO(cwinter) stopgap until children becomes a smart list

                    for child in reversed(suite_stmts[:i]):

                        e_suite.insert_child(0, child)

                    e_suite.insert_child(i, assign)

                elif N.get_prefix() == "":

                    # No space after a comma is legal; no space after "as",

                    # not so much.

                    N.set_prefix(" ")

        #TODO(cwinter) fix this when children becomes a smart list

        children = [c.clone() for c in node.children[:3]] + try_cleanup + tail

        return pytree.Node(node.type, children)