# Import previous version maya ascii file animCurve as buffer curve.
# Assumption is that the anim curve is named the same and is present in file.

import maya.cmds as cmds
import tempfile
import os.path
import shutil
import shlex
import re

CURVE = re.compile(r"\s*createNode animCurve[TU][LUTA].+\-n\s+\"([^\"]+)\".*?;")
COMMANDS = ("file", "requires", "createNode", "parent", "connectAttr", "disconnectAttr", "select", "currentUnit", "fileInfo")

def statement(parser):
    for token in parser:
        if token == ";":
            break
        yield token

def get_anim(path, curves):
    curves = set(curves)
    with open(path, "rb") as f:
        if f.read(6) != "//Maya":
            raise RuntimeError("Not a Maya Ascii file: %s" % path)
        f.seek(0)

        parser = shlex.shlex(f, posix=True)
        parser.commenters = "//"
        parser.wordchars += ".-:"
        for line in iter(f.readline, ""):
            if not curves: break
            header = CURVE.match(line) # Could parse whole file. But regex to location is faster
            if header and header.group(1) in curves:
                curves.remove(header.group(1))
                code = [header.group(0)]
                while True:
                    loc = f.tell()
                    st = tuple(statement(parser))
                    if not st or st[0] in COMMANDS:
                        f.seek(loc)
                        break
                    code.append(" ".join(st) + ";")
                yield "\n".join(code)

def load_anim(curves):
    tmp = tempfile.mkdtemp(dir=os.path.expanduser("~/"))
    try:
        tmpfile = os.path.join(tmp, "curves.ma")
        data = "//Maya ASCII\nrequires maya \"%s\";\n%s" % (cmds.about(v=True), "\n".join(curves))
        with open(tmpfile, "w") as f: f.write(data)
        nodes = cmds.file(tmpfile, i=True, rnn=True, ns="TMP")
        try:
            for node in cmds.ls(nodes, type="animCurve"):
                yield node
        finally:
            cmds.delete(nodes)
    finally:
        shutil.rmtree(tmp)

def main(path=None, editor="graphEditor1GraphEd"):
    selection = {a: cmds.keyframe(a, q=True, sl=True, iv=True) or [] for a in cmds.animCurveEditor(editor, q=True, cs=True) or []} if cmds.animCurveEditor(editor, ex=True) else []
    if not selection:
        raise RuntimeError("Please select some curves in the graph editor.")
    if path is None:
        path = cmds.fileDialog2(ff="Maya ASCII (*.ma)", fm=1)
        path = path[0] if path else ""
    if not path:
        raise RuntimeError("Please specify an .ma file to load from.")
    cmds.animCurveEditor(editor, e=True, sb="on")
    sel_obj = cmds.ls(sl=True)
    try:
        anim = get_anim(path, selection)
        missing = selection.keys()
        for node in load_anim(anim):
            name = node.rsplit(":", -1)[-1]
            cmds.bufferCurve(name, ov=True)
            cmds.copyKey(node, cb="api")
            cmds.pasteKey(name, o="replaceCompletely", cb="api")
            cmds.bufferCurve(name, sw=True)
            missing.remove(name)
        if missing: cmds.warning("Some curves were not present in file. %s" % missing)
    finally:
        cmds.select(sel_obj)
        for curve, index in selection.items():
            for i in index: cmds.selectKey(curve, index=(i,), add=True)
main("replace with path to file")