"""
A root that goes away freezes; it never empties.

This is the property the whole per-root availability design exists for. Unplug a
drive while the node is running and the filesystem watcher either reports every
file under it as deleted, or the next scan sees an empty directory. Acting on
either propagates deletions for a whole library, to every member, as though the
owner had erased it — and the index is what the node serves, so the loss is not
local.

Every test here is written as "the entries are still there". They fail against
an indexer that treats a vanished root as a set of deletions, which is what the
straightforward implementation does.
"""

import asyncio
import os
from pathlib import Path

import pytest
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey

from meshbay_node.indexer.indexer import DirectoryIndexer
from meshbay_node.roots import RootSet

pytestmark = pytest.mark.asyncio


def _roots(*paths: Path, removable: bool = False) -> RootSet:
    specs = [{"path": str(p)} for p in paths]
    specs[0]["writable"] = True
    if removable:
        for spec in specs:
            spec["removable"] = True
    return RootSet.build(specs)


async def _indexer(roots: RootSet) -> DirectoryIndexer:
    idx = DirectoryIndexer(roots=roots, group_id="g" * 32,
                           sk_node=Ed25519PrivateKey.generate(), gek=None)
    await idx.initial_scan()
    return idx


def _names(idx: DirectoryIndexer) -> set[str]:
    return {e.name for e in idx.index.entries}


# ── The freeze ───────────────────────────────────────────────────────────────

async def test_a_vanished_root_does_not_empty_the_index(tmp_path):
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    (films / "b.mkv").write_bytes(b"b")

    idx = await _indexer(_roots(films))
    assert _names(idx) == {"a.mkv", "b.mkv"}

    # The volume goes away. Watchdog would now report both files as deleted.
    for f in films.iterdir():
        f.unlink()
    films.rmdir()

    for f in ("a.mkv", "b.mkv"):
        await idx._update_entry(films / f, deleted=True)

    assert _names(idx) == {"a.mkv", "b.mkv"}, (
        "an unplugged drive emptied the index — every member would see the "
        "library as deleted")
    assert idx.roots.roots[0].available is False


async def test_reconcile_does_not_delete_from_an_unavailable_root(tmp_path):
    """The sweep must skip roots it cannot read: there is nothing to compare
    against, and comparing anyway deletes everything."""
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")

    idx = await _indexer(_roots(films))
    (films / "a.mkv").unlink()
    films.rmdir()

    await idx.reconcile()

    assert _names(idx) == {"a.mkv"}
    assert idx.roots.roots[0].available is False


async def test_one_root_going_away_leaves_the_others_alone(tmp_path):
    films = tmp_path / "Films"
    music = tmp_path / "Music"
    films.mkdir()
    music.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    # Above the tiny-audio-file cutoff (indexer.py's MIN_AUDIO_SIZE_BYTES) —
    # this test is about root availability, not that gate, so the content
    # just needs to actually get indexed as an entry.
    (music / "b.mp3").write_bytes(os.urandom(60 * 1024))

    idx = await _indexer(_roots(films, music))
    assert _names(idx) == {"a.mkv", "b.mp3"}

    (music / "b.mp3").unlink()
    music.rmdir()
    await idx.reconcile()

    assert _names(idx) == {"a.mkv", "b.mp3"}
    by_name = {r.name: r.available for r in idx.roots}
    assert by_name == {"Films": True, "Music": False}


async def test_members_are_told_which_roots_are_unavailable(tmp_path):
    """Frozen entries stay listed, so without this a member cannot tell
    "temporarily unavailable" from "still there"."""
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")

    idx = await _indexer(_roots(films))
    assert idx.index.roots == [
        {"name": "Films", "kind": "generic", "available": True,
         "writable": True, "removable": False, "ejected": False}]

    (films / "a.mkv").unlink()
    films.rmdir()
    await idx.reconcile()

    assert idx.index.roots[0]["available"] is False


# ── The counter-property ─────────────────────────────────────────────────────

async def test_a_file_deleted_from_a_live_root_is_removed(tmp_path):
    """
    The freeze must not become "deletions never happen". A root that is readable
    and a file that is genuinely gone is an ordinary deletion.
    """
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    (films / "b.mkv").write_bytes(b"b")

    idx = await _indexer(_roots(films))
    (films / "a.mkv").unlink()
    await idx._update_entry(films / "a.mkv", deleted=True)

    assert _names(idx) == {"b.mkv"}


async def test_reconcile_removes_what_is_genuinely_gone(tmp_path):
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    (films / "b.mkv").write_bytes(b"b")

    idx = await _indexer(_roots(films))
    (films / "a.mkv").unlink()
    await idx.reconcile()

    assert _names(idx) == {"b.mkv"}


async def test_reconcile_picks_up_a_file_the_watcher_missed(tmp_path):
    """
    `ReadDirectoryChangesW` drops events under load and inotify on a FUSE mount
    misses changes made outside it. Both are the common case here, so the sweep
    is the only thing that recovers.
    """
    films = tmp_path / "Films"
    films.mkdir()
    idx = await _indexer(_roots(films))

    (films / "late.mkv").write_bytes(b"x")     # no event delivered
    await idx.reconcile()

    assert _names(idx) == {"late.mkv"}


async def test_a_returning_root_is_rescanned(tmp_path):
    films = tmp_path / "Films"
    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")

    idx = await _indexer(_roots(films))
    (films / "a.mkv").unlink()
    films.rmdir()
    await idx.reconcile()
    assert _names(idx) == {"a.mkv"}          # frozen

    films.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    (films / "c.mkv").write_bytes(b"c")
    await idx.reconcile()

    assert _names(idx) == {"a.mkv", "c.mkv"}
    assert idx.roots.roots[0].available is True


async def test_a_root_absent_at_startup_is_not_an_error(tmp_path):
    """
    Someone starts the node with the drive unplugged. The group still exists and
    the other roots still serve; this one fills in when it returns.
    """
    films = tmp_path / "Films"
    music = tmp_path / "Music"
    films.mkdir()
    music.mkdir()
    (films / "a.mkv").write_bytes(b"a")
    roots = _roots(films, music)
    music.rmdir()

    idx = await _indexer(roots)

    assert _names(idx) == {"a.mkv"}
    assert {r.name: r.available for r in idx.roots} == {"Films": True, "Music": False}


# ── Paths carry their root ───────────────────────────────────────────────────

async def test_every_path_starts_with_its_root_name(tmp_path):
    films = tmp_path / "Films"
    (films / "2024").mkdir(parents=True)
    (films / "top.mkv").write_bytes(b"t")
    (films / "2024" / "deep.mkv").write_bytes(b"d")

    idx = await _indexer(_roots(films))
    by_name = {e.name: e.path for e in idx.index.entries}

    assert by_name == {"top.mkv": "Films", "deep.mkv": "Films/2024"}


async def test_a_single_root_group_is_not_a_special_case(tmp_path):
    """One path shape has to be got right once; two have to be kept right
    forever. A lone root prefixes exactly like any other."""
    only = tmp_path / "Shared"
    only.mkdir()
    (only / "x.txt").write_bytes(b"x")

    idx = await _indexer(_roots(only))
    assert [e.path for e in idx.index.entries] == ["Shared"]


async def test_same_relative_path_in_two_roots_stays_distinct(tmp_path):
    films = tmp_path / "Films"
    music = tmp_path / "Music"
    (films / "2024").mkdir(parents=True)
    (music / "2024").mkdir(parents=True)
    (films / "2024" / "same.dat").write_bytes(b"film")
    (music / "2024" / "same.dat").write_bytes(b"music")

    idx = await _indexer(_roots(films, music))
    paths = sorted(e.path for e in idx.index.entries)

    assert paths == ["Films/2024", "Music/2024"]
    assert len(idx.index.entries) == 2


# ── Duplicate content ────────────────────────────────────────────────────────

async def test_identical_files_do_not_churn_the_index(tmp_path):
    """
    The index is keyed by content hash, so the same bytes at two paths are one
    entry. Reconciliation compares paths, so without care it decides the second
    path is a missed event **every cycle** — rewriting that entry, bumping the
    version, and pushing an index update to every connected peer once a minute.

    Found on a live node: `clip.mp4` sat at the root of a shared directory and
    in `uploads/` with identical bytes.
    """
    films = tmp_path / "Films"
    (films / "uploads").mkdir(parents=True)
    (films / "clip.mp4").write_bytes(b"same bytes")
    (films / "uploads" / "clip.mp4").write_bytes(b"same bytes")

    idx = await _indexer(_roots(films))
    assert len(idx.index.entries) == 1, "content-addressed index, so one entry"

    await idx.reconcile()
    first = (idx.index.version, idx.index.entries[0].path)
    await idx.reconcile()
    second = (idx.index.version, idx.index.entries[0].path)

    assert first == second, (
        "reconciliation rewrote the entry for a duplicate it cannot represent — "
        "every peer would receive an index update every cycle")


async def test_deleting_one_copy_keeps_the_other_listed(tmp_path):
    """
    The mirror case: the recorded path goes, identical content stays. Dropping
    the entry would delist a file that is still on disk and still servable.
    """
    films = tmp_path / "Films"
    (films / "uploads").mkdir(parents=True)
    (films / "clip.mp4").write_bytes(b"same bytes")
    (films / "uploads" / "clip.mp4").write_bytes(b"same bytes")

    idx = await _indexer(_roots(films))
    recorded = idx.index.entries[0].path
    survivor = "Films/uploads" if recorded == "Films" else "Films"

    (films / "clip.mp4").unlink() if recorded == "Films" else \
        (films / "uploads" / "clip.mp4").unlink()
    await idx.reconcile()

    assert len(idx.index.entries) == 1, "the surviving copy was delisted"
    assert idx.index.entries[0].path == survivor