"""Fixer for function definitions with tuple parameters.

def func(((a, b), c), d):

    ...

    ->

def func(x, d):

    ((a, b), c) = x

    ...

It will also support lambdas:

    lambda (x, y): x + y -> lambda t: t[0] + t[1]

    # The parens are a syntax error in Python 3

    lambda (x): x + y -> lambda x: x + y

"""

# Author: Collin Winter

# Local imports

from .. import pytree

from ..pgen2 import token

from .. import fixer_base

from ..fixer_util import Assign, Name, Newline, Number, Subscript, syms

def is_docstring(stmt):

    return isinstance(stmt, pytree.Node) and \

           stmt.children[0].type == token.STRING

class FixTupleParams(fixer_base.BaseFix):

    PATTERN = """

              funcdef< 'def' any parameters< '(' args=any ')' >

                       ['->' any] ':' suite=any+ >

              |

              lambda=

              lambdef< 'lambda' args=vfpdef< '(' inner=any ')' >

                       ':' body=any

              >

              """

    def transform(self, node, results):

        if "lambda" in results:

            return self.transform_lambda(node, results)

        new_lines = []

        suite = results["suite"]

        args = results["args"]

        # This crap is so "def foo(...): x = 5; y = 7" is handled correctly.

        # TODO(cwinter): suite-cleanup

        if suite[0].children[1].type == token.INDENT:

            start = 2

            indent = suite[0].children[1].value

            end = Newline()

        else:

            start = 0

            indent = "; "

            end = pytree.Leaf(token.INDENT, "")

        # We need access to self for new_name(), and making this a method

        #  doesn't feel right. Closing over self and new_lines makes the

        #  code below cleaner.

        def handle_tuple(tuple_arg, add_prefix=False):

            n = Name(self.new_name())

            arg = tuple_arg.clone()

            arg.set_prefix("")

            stmt = Assign(arg, n.clone())

            if add_prefix:

                n.set_prefix(" ")

            tuple_arg.replace(n)

            new_lines.append(pytree.Node(syms.simple_stmt,

                                         [stmt, end.clone()]))

        if args.type == syms.tfpdef:

            handle_tuple(args)

        elif args.type == syms.typedargslist:

            for i, arg in enumerate(args.children):

                if arg.type == syms.tfpdef:

                    # Without add_prefix, the emitted code is correct,

                    #  just ugly.

                    handle_tuple(arg, add_prefix=(i > 0))

        if not new_lines:

            return node

        # This isn't strictly necessary, but it plays nicely with other fixers.

        # TODO(cwinter) get rid of this when children becomes a smart list

        for line in new_lines:

            line.parent = suite[0]

        # TODO(cwinter) suite-cleanup

        after = start

        if start == 0:

            new_lines[0].set_prefix(" ")

        elif is_docstring(suite[0].children[start]):

            new_lines[0].set_prefix(indent)

            after = start + 1

        suite[0].children[after:after] = new_lines

        for i in range(after+1, after+len(new_lines)+1):

            suite[0].children[i].set_prefix(indent)

        suite[0].changed()

    def transform_lambda(self, node, results):

        args = results["args"]

        body = results["body"]

        inner = simplify_args(results["inner"])

        # Replace lambda ((((x)))): x  with lambda x: x

        if inner.type == token.NAME:

            inner = inner.clone()

            inner.set_prefix(" ")

            args.replace(inner)

            return

        params = find_params(args)

        to_index = map_to_index(params)

        tup_name = self.new_name(tuple_name(params))

        new_param = Name(tup_name, prefix=" ")

        args.replace(new_param.clone())

        for n in body.post_order():

            if n.type == token.NAME and n.value in to_index:

                subscripts = [c.clone() for c in to_index[n.value]]

                new = pytree.Node(syms.power,

                                  [new_param.clone()] + subscripts)

                new.set_prefix(n.get_prefix())

                n.replace(new)

### Helper functions for transform_lambda()

def simplify_args(node):

    if node.type in (syms.vfplist, token.NAME):

        return node

    elif node.type == syms.vfpdef:

        # These look like vfpdef< '(' x ')' > where x is NAME

        # or another vfpdef instance (leading to recursion).

        while node.type == syms.vfpdef:

            node = node.children[1]

        return node

    raise RuntimeError("Received unexpected node %s" % node)

def find_params(node):

    if node.type == syms.vfpdef:

        return find_params(node.children[1])

    elif node.type == token.NAME:

        return node.value

    return [find_params(c) for c in node.children if c.type != token.COMMA]

def map_to_index(param_list, prefix=[], d=None):

    if d is None:

        d = {}

    for i, obj in enumerate(param_list):

        trailer = [Subscript(Number(i))]

        if isinstance(obj, list):

            map_to_index(obj, trailer, d=d)

        else:

            d[obj] = prefix + trailer

    return d

def tuple_name(param_list):

    l = []

    for obj in param_list:

        if isinstance(obj, list):

            l.append(tuple_name(obj))

        else:

            l.append(obj)

    return "_".join(l)