from __future__ import annotations

from collections.abc import Callable
from dataclasses import FrozenInstanceError
from pathlib import Path
from typing import Any, cast

import pytest

from mdpolish.text_ranges import PhysicalLine, iter_physical_lines, line_ending_styles, physical_lines


def _offsets(lines: tuple[PhysicalLine, ...]) -> tuple[tuple[int, int, int], ...]:
    return tuple((line.content_start, line.content_end, line.full_end) for line in lines)


@pytest.mark.parametrize(
    ("source", "expected"),
    [
        ("", ()),
        ("a", ((0, 1, 1),)),
        ("a\n", ((0, 1, 2),)),
        ("\n", ((0, 0, 1),)),
        ("\r\n", ((0, 0, 2),)),
        ("a\n\n", ((0, 1, 2), (2, 2, 3))),
        ("\ntext", ((0, 0, 1), (1, 5, 5))),
        ("a\r\nb\rc\n", ((0, 1, 3), (3, 4, 5), (5, 6, 7))),
        ("a\u2028b", ((0, 3, 3),)),
    ],
)
def test_scans_exact_physical_line_offsets(
    source: str,
    expected: tuple[tuple[int, int, int], ...],
) -> None:
    assert _offsets(physical_lines(source)) == expected


@pytest.mark.parametrize(
    "source",
    [
        "",
        "one line",
        "\nleading empty",
        "a\n\n",
        "a\r\nb\rc\n",
        "\ufeff中文😀e\u0301\u2028\x00\t\f",
    ],
)
def test_ranges_reconstruct_source_without_normalization(source: str) -> None:
    lines = physical_lines(source)

    assert "".join(source[line.content_start : line.full_end] for line in lines) == source
    assert lines == tuple(iter_physical_lines(source))
    assert lines == physical_lines(source)
    for line in lines:
        assert line.content(source) == source[line.content_start : line.content_end]
        assert line.line_ending(source) == source[line.content_end : line.full_end]


def test_unicode_separators_and_control_characters_remain_content() -> None:
    source = "\ufeff中文😀e\u0301\u2028\u2029\x00\t\f"
    line = physical_lines(source)[0]

    assert (line.content_start, line.content_end, line.full_end) == (0, len(source), len(source))
    assert line.content(source) == source
    assert line.line_ending(source) == ""


@pytest.mark.parametrize(
    ("source", "expected"),
    [
        ("", frozenset()),
        ("no ending", frozenset()),
        ("a\nb\n", frozenset(("\n",))),
        ("a\r\nb\r\n", frozenset(("\r\n",))),
        ("a\rb\r", frozenset(("\r",))),
        ("a\nb\r\nc\r", frozenset(("\n", "\r\n", "\r"))),
    ],
)
def test_reports_only_line_endings_present_in_source(source: str, expected: frozenset[str]) -> None:
    assert line_ending_styles(source) == expected


def test_empty_means_zero_length_content_not_whitespace() -> None:
    empty, space, tab = physical_lines("\n \n\t\n")

    assert empty.is_empty
    assert not space.is_empty
    assert not tab.is_empty


def test_physical_line_is_frozen_and_slotted() -> None:
    line = PhysicalLine(0, 1, 1)
    mutable_view = cast(Any, line)

    with pytest.raises(FrozenInstanceError):
        mutable_view.content_start = 1
    assert not hasattr(line, "__dict__")


@pytest.mark.parametrize("field_index", [0, 1, 2])
@pytest.mark.parametrize("invalid", [True, 1.0, "1", None])
def test_rejects_non_integer_offsets(field_index: int, invalid: object) -> None:
    values = [0, 0, 0]
    values[field_index] = cast(int, invalid)

    with pytest.raises(TypeError):
        PhysicalLine(*values)


@pytest.mark.parametrize(
    "offsets",
    [
        (-1, 0, 0),
        (0, -1, 0),
        (0, 0, -1),
        (1, 0, 1),
        (0, 2, 1),
        (0, 0, 3),
    ],
)
def test_rejects_invalid_offset_ranges(offsets: tuple[int, int, int]) -> None:
    with pytest.raises(ValueError):
        PhysicalLine(*offsets)


@pytest.mark.parametrize(
    "scanner",
    [iter_physical_lines, physical_lines, line_ending_styles],
)
@pytest.mark.parametrize("invalid", [b"text", Path("text.md"), None, 1])
def test_scanners_reject_non_string_sources_immediately(
    scanner: Callable[[str], object],
    invalid: object,
) -> None:
    with pytest.raises(TypeError, match="source must be a string"):
        scanner(cast(str, invalid))


def test_iter_scanner_validates_before_iteration_begins() -> None:
    with pytest.raises(TypeError, match="source must be a string"):
        iter_physical_lines(cast(str, b"deferred validation would be wrong"))


def test_accessors_reject_non_string_or_short_sources() -> None:
    line = PhysicalLine(0, 1, 2)

    with pytest.raises(TypeError, match="source must be a string"):
        line.content(cast(str, b"a\n"))
    with pytest.raises(TypeError, match="source must be a string"):
        line.line_ending(cast(str, None))
    with pytest.raises(ValueError, match="exceeds source length"):
        line.content("a")
    with pytest.raises(ValueError, match="exceeds source length"):
        line.line_ending("a")


@pytest.mark.parametrize(
    ("line", "source"),
    [
        (PhysicalLine(0, 1, 2), "ab"),
        (PhysicalLine(0, 0, 2), "\n\r"),
    ],
)
def test_line_ending_rejects_non_physical_slices(line: PhysicalLine, source: str) -> None:
    with pytest.raises(ValueError, match="empty, LF, CR, or CRLF"):
        line.line_ending(source)


@pytest.mark.parametrize("source", ["a", "a\n", "a\r", "a\r\n"])
def test_line_ending_accepts_every_supported_slice(source: str) -> None:
    line = physical_lines(source)[0]

    assert line.line_ending(source) in {"", "\n", "\r", "\r\n"}