"""Incremental maintenance == rebuild, with retraction + propagation (SHARD-WP-0011 T2)."""

from shard_wiki.incremental import EquivalenceIndex
from shard_wiki.model import Identity, Page
from shard_wiki.provenance import ProvenanceEnvelope


def _page(shard, key, body):
    return Page(
        identity=Identity(shard, key),
        body=body,
        envelope=ProvenanceEnvelope(source_shard=shard),
    )


def _rebuilt(pages, curator=()):
    idx = EquivalenceIndex()
    idx.build(pages, curator)
    return idx


def _equal(a, b):
    return a.edges() == b.edges() and set(a.groups()) == set(b.groups())


def test_add_keeps_index_equal_to_rebuild():
    pages = [_page("A", "Foo", "same content here"), _page("B", "Bar", "same content here")]
    idx = EquivalenceIndex()
    for p in pages:
        idx.add(p)
    assert _equal(idx, _rebuilt(pages))
    assert idx.groups()  # the two collapse


def test_remove_keeps_index_equal_to_rebuild():
    pages = [
        _page("A", "Foo", "same content here"),
        _page("B", "Bar", "same content here"),
        _page("C", "Baz", "unrelated isolated material entirely"),
    ]
    idx = _rebuilt(pages)
    idx.remove(Identity("B", "Bar"))
    assert _equal(idx, _rebuilt([pages[0], pages[2]]))


def test_edit_into_new_bucket_retracts_stale_edge():
    a = _page("A", "Foo", "shared identical body text")
    b = _page("B", "Bar", "shared identical body text")
    idx = _rebuilt([a, b])
    assert idx.groups()  # A ≡ B initially
    # Edit B to something completely different: it exits A's buckets, the edge is retracted.
    b2 = _page("B", "Bar", "now totally divergent unrelated prose about nothing")
    idx.update(b2)
    assert idx.groups() == ()  # stale edge gone
    assert _equal(idx, _rebuilt([a, b2]))


def test_edit_into_equivalence_adds_edge():
    a = _page("A", "Foo", "target body to converge on later")
    b = _page("B", "Bar", "initially completely separate writing here")
    idx = _rebuilt([a, b])
    assert idx.groups() == ()
    b2 = _page("B", "Bar", "target body to converge on later")  # now identical to A
    idx.update(b2)
    assert idx.equivalent_to(Identity("A", "Foo")) == frozenset(
        {Identity("A", "Foo"), Identity("B", "Bar")}
    )
    assert _equal(idx, _rebuilt([a, b2]))


def test_removing_connector_splits_a_chorus():
    # Curator chain A—B—C (no direct A—C): one group of three.
    a, b, c = (_page("A", "X", "aaa"), _page("B", "Y", "bbb"), _page("C", "Z", "ccc"))
    idx = EquivalenceIndex()
    for p in (a, b, c):
        idx.add(p)
    idx.bind(a.identity, b.identity)
    idx.bind(b.identity, c.identity)
    assert idx.equivalent_to(a.identity) == {a.identity, b.identity, c.identity}
    # Removing the connector B retracts/propagates: the chorus splits.
    idx.remove(b.identity)
    assert idx.groups() == ()
    chain = [(a.identity, b.identity), (b.identity, c.identity)]
    assert _equal(idx, _rebuilt([a, c], curator=chain))