import fontTools.feaLib.ast as feaast
from fontFeatures.ttLib.Positioning import lookup_type


def glyphref(g):
    if len(g) == 1:
        return feaast.GlyphName(g[0])
    return feaast.GlyphClass([feaast.GlyphName(x) for x in sorted(g)])


def asFeaAST(self):
    lut = lookup_type(self)
    glyphs = [glyphref(x) for x in self.glyphs]
    positionings = list(zip(glyphs, self.valuerecords))
    if len(self.glyphs) == 1 or lut == 8:
        return feaast.SinglePosStatement(
            positionings,
            [glyphref(x) for x in self.precontext],
            [glyphref(x) for x in self.postcontext],
            (lut == 8),
        )
    if lut == 2:
        return feaast.PairPosStatement(
            glyphs[0], self.valuerecords[0], glyphs[1], self.valuerecords[1]
        )
    raise ValueError()