"""Write-back tests: surgical edits, atomicity, conflicts (SPEC 12, tests 3/8)."""

from __future__ import annotations

import difflib
import os
from pathlib import Path

import pytest

from mdcaldav.config import Config
from mdcaldav.ical import apply_to_task
from mdcaldav.index import Index
from mdcaldav.model import Status
from mdcaldav.writer import ConflictError, NotAllowedError, Writer


@pytest.fixture
def env(vault: Path, tmp_path: Path):
    cfg = Config()
    cfg.vault.path = vault
    cfg.index.db = tmp_path / "index.db"
    index = Index(cfg)
    index.rescan()
    yield cfg, index, Writer(cfg, index), vault
    index.close()


def uid_of(index: Index, title: str, rel: str | None = None) -> str:
    matches = [
        t
        for t in index.tasks.values()
        if t.title == title and (rel is None or t.source.rel_path == rel)
    ]
    assert len(matches) == 1, f"{title!r} matched {len(matches)}"
    return matches[0].uid


def diff_lines(before: str, after: str) -> list[str]:
    return [
        line
        for line in difflib.unified_diff(
            before.splitlines(), after.splitlines(), lineterm="", n=0
        )
        if line[:1] in "+-" and not line.startswith(("---", "+++"))
    ]


def test_completion_changes_exactly_one_line(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    before = (vault / rel).read_text()

    writer.apply(uid_of(index, "Water the seedlings", rel), {"status": Status.COMPLETED})

    after = (vault / rel).read_text()
    assert diff_lines(before, after) == [
        "-- [ ] Water the seedlings",
        "+- [x] Water the seedlings",
    ]


def test_completion_toggles_back(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    before = (vault / rel).read_bytes()
    uid = uid_of(index, "Water the seedlings", rel)

    writer.apply(uid, {"status": Status.COMPLETED})
    writer.apply(uid, {"status": Status.NEEDS_ACTION})

    assert (vault / rel).read_bytes() == before  # round trip is byte-identical


def test_nested_task_completion_leaves_siblings_alone(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-05.md"
    before = (vault / rel).read_text()

    writer.apply(
        uid_of(index, "Decide on trellis height", rel), {"status": Status.COMPLETED}
    )

    after = (vault / rel).read_text()
    assert diff_lines(before, after) == [
        "-    - [ ] Decide on trellis height",
        "+    - [x] Decide on trellis height",
    ]


def test_retitle_preserves_indent_bullet_and_priority(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    writer.apply(uid_of(index, "Book the soil test", rel), {"title": "Book the soil test today"})
    assert "- [ ] [#A] Book the soil test today" in (vault / rel).read_text()


def test_priority_set_clear_and_change(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"

    uid = uid_of(index, "Water the seedlings", rel)
    writer.apply(uid, {"priority": 1})
    assert "- [ ] [#A] Water the seedlings" in (vault / rel).read_text()

    writer.apply(uid, {"priority": 9})
    assert "- [ ] [#C] Water the seedlings" in (vault / rel).read_text()

    writer.apply(uid, {"priority": None})
    assert "- [ ] Water the seedlings" in (vault / rel).read_text()
    assert "[#" not in (vault / rel).read_text().split("Water the seedlings")[0].splitlines()[-1]


def test_description_replaced_in_place(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-05.md"
    writer.apply(
        uid_of(index, "Order the cover crop", rel), {"description": "Invoice filed"}
    )
    text = (vault / rel).read_text()
    assert "    - Invoice filed" in text
    assert "Arrived on the 12th" not in text


def test_description_added_where_none_existed(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    writer.apply(
        uid_of(index, "Call the arborist", rel), {"description": "Ask about the oak"}
    )
    text = (vault / rel).read_text()
    assert "- [ ] [#B] Call the arborist\n  - Ask about the oak\n" in text


def test_description_removed(env):
    _, index, writer, vault = env
    rel = "daily/2026-01-05.md"
    writer.apply(uid_of(index, "Order the cover crop", rel), {"description": None})
    text = (vault / rel).read_text()
    assert "Arrived on the 12th" not in text
    assert "- [x] Order the cover crop\n  - [x] Sharpen the pruners" in text


def test_untouched_files_are_not_rewritten(env):
    _, index, writer, vault = env
    others = {
        rel: (vault / rel).read_bytes()
        for rel in ("daily/2026-01-06.md", "projects/irrigation.md", "reference/glossary.md")
    }
    writer.apply(
        uid_of(index, "Water the seedlings", "daily/2026-01-07.md"),
        {"status": Status.COMPLETED},
    )
    for rel, content in others.items():
        assert (vault / rel).read_bytes() == content


def test_crlf_and_missing_final_newline_preserved(env, tmp_path: Path):
    cfg, index, writer, vault = env
    rel = "daily/crlf.md"
    (vault / rel).write_bytes(b"# T\r\n\r\n- [ ] alpha\r\n- [ ] omega")  # no final newline
    index.rescan()

    writer.apply(uid_of(index, "alpha", rel), {"status": Status.COMPLETED})

    data = (vault / rel).read_bytes()
    assert data == b"# T\r\n\r\n- [x] alpha\r\n- [ ] omega"


def test_unicode_title_edit_keeps_bytes_aligned(env):
    _, index, writer, vault = env
    rel = "daily/uni.md"
    (vault / rel).write_text("- [ ] café → naïve\n- [ ] after\n", encoding="utf-8")
    index.rescan()

    writer.apply(uid_of(index, "café → naïve", rel), {"status": Status.COMPLETED})
    assert (vault / rel).read_text() == "- [x] café → naïve\n- [ ] after\n"


def test_conflict_when_task_deleted_underneath(env):
    """The task the client addressed no longer exists → refuse, don't guess."""
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    uid = uid_of(index, "Water the seedlings", rel)

    text = (vault / rel).read_text()
    (vault / rel).write_text(text.replace("- [ ] Water the seedlings\n", ""))
    before = (vault / rel).read_bytes()

    with pytest.raises(ConflictError):
        writer.apply(uid, {"status": Status.COMPLETED})
    assert (vault / rel).read_bytes() == before  # not corrupted


def test_external_retitle_is_the_same_task(env):
    """Identity rule 2 treats an in-place retitle as the same task, so the
    write lands on the renamed line rather than failing. The client's own
    staleness is caught a layer up by Radicale's If-Match/ETag check."""
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    uid = uid_of(index, "Water the seedlings", rel)

    text = (vault / rel).read_text()
    (vault / rel).write_text(text.replace("Water the seedlings", "Water the beds"))

    writer.apply(uid, {"status": Status.COMPLETED})
    assert "- [x] Water the beds" in (vault / rel).read_text()


def test_stale_spans_are_never_used(env):
    """An edit that shifts line offsets must not corrupt a later write."""
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    uid = uid_of(index, "Water the seedlings", rel)

    # Insert lines above the target, invalidating every cached byte offset.
    text = (vault / rel).read_text()
    (vault / rel).write_text(text.replace("## TODO\n", "## TODO\n\nSome new prose here.\n\n"))

    writer.apply(uid, {"status": Status.COMPLETED})
    result = (vault / rel).read_text()
    assert "- [x] Water the seedlings" in result
    assert "Some new prose here." in result
    assert "- [ ] [#A] Book the soil test" in result  # neighbours intact


def test_unrelated_external_edit_is_absorbed(env):
    """A change elsewhere in the file must not block an unrelated write."""
    _, index, writer, vault = env
    rel = "daily/2026-01-07.md"
    uid = uid_of(index, "Water the seedlings", rel)

    text = (vault / rel).read_text()
    (vault / rel).write_text(text.replace("# Wednesday", "# Weds"))

    writer.apply(uid, {"status": Status.COMPLETED})
    assert "- [x] Water the seedlings" in (vault / rel).read_text()


def test_delete_cascades_to_subtree(env):
    _, index, writer, vault = env
    rel = "projects/irrigation.md"
    writer.delete(uid_of(index, "Trench the main line", rel))
    text = (vault / rel).read_text()
    assert "Trench the main line" not in text
    assert "Rent the trencher" not in text  # cascaded
    assert "frost line" not in text  # its description went too
    assert "Price the manifold" in text  # sibling untouched


def test_delete_reject_policy(env):
    cfg, index, writer, vault = env
    cfg.write.delete_children = "reject"
    with pytest.raises(NotAllowedError):
        writer.delete(uid_of(index, "Trench the main line", "projects/irrigation.md"))


def test_delete_disabled(env):
    cfg, index, writer, _ = env
    cfg.write.allow_delete = False
    with pytest.raises(NotAllowedError):
        writer.delete(uid_of(index, "Reseal the base", "daily/2026-01-06.md"))


def test_create_lands_in_inbox(env):
    _, index, writer, vault = env
    uid = writer.create({"title": "Buy netting", "priority": 1})
    text = (vault / "inbox.md").read_text()
    assert "## Inbox" in text
    assert "- [ ] [#A] Buy netting" in text
    assert index.tasks[uid].title == "Buy netting"


def test_create_disabled(env):
    cfg, _, writer, _ = env
    cfg.write.allow_create = False
    with pytest.raises(NotAllowedError):
        writer.create({"title": "nope"})


def test_atomic_write_leaves_no_temp_files(env):
    _, index, writer, vault = env
    writer.apply(
        uid_of(index, "Water the seedlings", "daily/2026-01-07.md"),
        {"status": Status.COMPLETED},
    )
    assert not list((vault / "daily").glob(".*tmp*"))


def test_upload_writes_even_when_the_index_is_stale(vault, tmp_path):
    """Regression: a stale index made completions silently no-op.

    `upload` diffed the client's VTODO against the cached in-memory task. If
    that cache disagreed with disk, the diff came out empty, `apply` returned
    early, and Radicale answered 2xx without touching the markdown — the client
    showed the task done while the file still said `- [ ]`.

    Reproduced the way NFS produces it: the file changes, but the stat() the
    index recorded still matches, so `refresh_if_stale` sees nothing. A status
    toggle does not change the file's size, so only mtime could betray it —
    and NFS attribute caching hides that for the length of the attr timeout.
    """
    from mdcaldav.config import Config
    from mdcaldav.index import Index
    from mdcaldav.model import Status

    cfg = Config()
    cfg.vault.path = vault
    cfg.index.db = tmp_path / "index.db"
    index = Index(cfg)
    index.rescan()
    writer = Writer(cfg, index)

    rel = "daily/2026-01-07.md"
    path = vault / rel
    uid = next(
        t.uid
        for t in index.tasks.values()
        if t.title == "Call the arborist" and t.source.rel_path == rel
    )

    # Complete it, so index and disk agree that it is done.
    writer.apply(uid, {"status": Status.COMPLETED})
    assert "- [x] [#B] Call the arborist" in path.read_text()

    # Now it is un-ticked in vim, and the change is invisible to stat():
    # same size, and we pin mtime/size back to what the index recorded.
    recorded = index.db.execute(
        "SELECT mtime, size FROM files WHERE rel_path = ?", (rel,)
    ).fetchone()
    path.write_text(path.read_text().replace("- [x] [#B] Call", "- [ ] [#B] Call"))
    os.utime(path, (recorded["mtime"], recorded["mtime"]))
    assert path.stat().st_size == recorded["size"]
    assert not index.refresh_if_stale()  # the staleness is genuinely hidden
    assert index.tasks[uid].status is Status.COMPLETED  # index disagrees with disk

    # The client PUTs "completed" again. Diffing against the stale cache yields
    # no changes at all; only re-reading the file reveals the real difference.
    assert apply_to_task(index.tasks[uid], {"status": Status.COMPLETED}, cfg) == {}

    index.refresh_file(rel)
    changes = apply_to_task(index.tasks[uid], {"status": Status.COMPLETED}, cfg)
    assert changes == {"status": Status.COMPLETED}
    writer.apply(uid, changes)

    assert "- [x] [#B] Call the arborist" in path.read_text()