from __future__ import annotations

from dataclasses import FrozenInstanceError
from hashlib import sha256

import pytest

from mdpolish import (
    DocumentSnapshot,
    ErrorStage,
    ProposedChange,
    ResidualProposal,
    RunError,
    RunStatus,
    TextEdit,
    TextSpan,
    TransformResult,
)
from mdpolish.models import ProposalReference


def test_snapshot_preserves_exact_markdown_and_computes_hash() -> None:
    markdown = "标题\r\nCafe\u0301\n🙂\n"

    snapshot = DocumentSnapshot(markdown)

    assert snapshot.markdown == markdown
    assert snapshot.sha256 == sha256(markdown.encode("utf-8")).hexdigest()


def test_empty_snapshot_is_valid_and_hash_cannot_be_supplied() -> None:
    snapshot = DocumentSnapshot("")

    assert snapshot.sha256 == sha256(b"").hexdigest()
    with pytest.raises(TypeError):
        DocumentSnapshot("", sha256="0" * 64)  # type: ignore[call-arg]


def test_snapshot_is_frozen() -> None:
    snapshot = DocumentSnapshot("original")

    with pytest.raises(FrozenInstanceError):
        snapshot.markdown = "changed"  # type: ignore[misc]


@pytest.mark.parametrize(
    ("start", "end", "error_type"),
    [
        (-1, 0, ValueError),
        (2, 1, ValueError),
        (True, 1, TypeError),
    ],
)
def test_span_rejects_invalid_indexes(start: int, end: int, error_type: type[Exception]) -> None:
    with pytest.raises(error_type):
        TextSpan(start, end)


def test_text_edit_supports_insert_delete_and_replace() -> None:
    snapshot = DocumentSnapshot("中文abc")

    insertion = TextEdit(snapshot.sha256, TextSpan(2, 2), "", "!")
    deletion = TextEdit(snapshot.sha256, TextSpan(2, 3), "a", "")
    replacement = TextEdit(snapshot.sha256, TextSpan(3, 5), "bc", "BC")

    assert insertion.span.is_empty
    assert deletion.replacement == ""
    assert replacement.expected_text == "bc"


def test_text_edit_rejects_bad_digest_length_mismatch_and_no_op() -> None:
    digest = DocumentSnapshot("abc").sha256

    with pytest.raises(ValueError, match="SHA-256"):
        TextEdit("bad", TextSpan(0, 1), "a", "b")
    with pytest.raises(ValueError, match="length"):
        TextEdit(digest, TextSpan(0, 2), "a", "b")
    with pytest.raises(ValueError, match="must change"):
        TextEdit(digest, TextSpan(0, 1), "a", "a")


def test_proposal_requires_reason_edits_and_one_matching_digest() -> None:
    snapshot = DocumentSnapshot("abc")
    other = DocumentSnapshot("xyz")
    edit = TextEdit(snapshot.sha256, TextSpan(0, 1), "a", "A")
    other_edit = TextEdit(other.sha256, TextSpan(0, 1), "x", "X")

    with pytest.raises(ValueError, match="reason"):
        ProposedChange(snapshot.sha256, " ", (edit,))
    with pytest.raises(ValueError, match="non-empty tuple"):
        ProposedChange(snapshot.sha256, "reason", ())
    with pytest.raises(ValueError, match="proposal digest"):
        ProposedChange(snapshot.sha256, "reason", (other_edit,))


def test_transform_result_enforces_status_specific_output_fields() -> None:
    snapshot = DocumentSnapshot("abc")
    error = RunError("component", "1.0.0", 0, ErrorStage.TRANSFORM, "ExampleError", "safe")
    edit = TextEdit(snapshot.sha256, TextSpan(0, 1), "a", "A")
    proposal = ProposedChange(snapshot.sha256, "reason", (edit,))
    residual = ResidualProposal(
        component_id="component",
        component_version="1.0.0",
        component_position=0,
        proposal_ref=ProposalReference(0, snapshot.sha256, 0),
        proposal=proposal,
    )

    success = TransformResult(
        status=RunStatus.SUCCESS,
        input_sha256=snapshot.sha256,
        current_sha256=snapshot.sha256,
        output_markdown=snapshot.markdown,
    )
    failed = TransformResult(
        status=RunStatus.FAILED,
        input_sha256=snapshot.sha256,
        current_sha256=snapshot.sha256,
        errors=(error,),
        partial_markdown=snapshot.markdown,
    )
    unstable = TransformResult(
        status=RunStatus.UNSTABLE,
        input_sha256=snapshot.sha256,
        current_sha256=snapshot.sha256,
        residual_proposals=(residual,),
        partial_markdown=snapshot.markdown,
    )

    assert success.output_markdown == "abc"
    assert failed.partial_markdown == "abc"
    assert unstable.residual_proposals == (residual,)

    with pytest.raises(ValueError, match="successful result"):
        TransformResult(
            status=RunStatus.SUCCESS,
            input_sha256=snapshot.sha256,
            current_sha256=snapshot.sha256,
            errors=(error,),
            output_markdown=snapshot.markdown,
        )
    with pytest.raises(ValueError, match="failed result"):
        TransformResult(
            status=RunStatus.FAILED,
            input_sha256=snapshot.sha256,
            current_sha256=snapshot.sha256,
            partial_markdown=snapshot.markdown,
        )