from io import StringIO

import numpy as np
import pytest

import pandas as pd
import pandas._testing as tm


class TestInvalidConcat:
    @pytest.mark.parametrize("obj", [1, {}, [1, 2], (1, 2)])
    def test_concat_invalid(self, obj):
        # trying to concat an ndframe with a non-ndframe
        df1 = pd.DataFrame(range(2))
        msg = (
            f"cannot concatenate object of type '{type(obj)}'; "
            "only Series and DataFrame objs are valid"
        )
        with pytest.raises(TypeError, match=msg):
            pd.concat([df1, obj])

    def test_concat_invalid_first_argument(self):
        df1 = pd.DataFrame(range(2))
        msg = (
            "first argument must be an iterable of pandas "
            'objects, you passed an object of type "DataFrame"'
        )
        with pytest.raises(TypeError, match=msg):
            pd.concat(df1)

    def test_concat_generator_obj(self):
        # generator ok though
        pd.concat(
            pd.DataFrame(np.random.default_rng(2).random((5, 5))) for _ in range(3)
        )

    def test_concat_textreader_obj(self):
        # text reader ok
        # GH6583
        data = """index,A,B,C,D
                  foo,2,3,4,5
                  bar,7,8,9,10
                  baz,12,13,14,15
                  qux,12,13,14,15
                  foo2,12,13,14,15
                  bar2,12,13,14,15
               """

        with pd.read_csv(StringIO(data), chunksize=1) as reader:
            result = pd.concat(reader, ignore_index=True)
        expected = pd.read_csv(StringIO(data))
        tm.assert_frame_equal(result, expected)