"""Tests for the event-sourced DecisionLog (SHARD-WP-0007 T5)."""

from shard_wiki.coordination import DecisionLog, EventType


def test_append_is_totally_ordered_per_space():
    log = DecisionLog()
    log.append("spaceA", EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"})
    log.append("spaceA", EventType.ALIAS_SET, {"alias": "Start", "target": "shardA:Index"})
    log.append("spaceB", EventType.ALIAS_SET, {"alias": "X", "target": "shardB:Y"})
    seqs = [e.seq for e in log.events("spaceA")]
    assert seqs == [0, 1]  # per-space monotonic
    assert [e.seq for e in log.events("spaceB")] == [0]  # independent ordering


def test_read_your_writes():
    log = DecisionLog()
    ev = log.append("s", EventType.ALIAS_SET, {"alias": "a", "target": "shardA:b"})
    assert log.events("s")[-1] is ev


def test_fold_reproduces_current_state():
    log = DecisionLog()
    log.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"})
    log.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "shardB:Main"})  # LWW
    state = log.fold("s")
    assert state.resolve_alias("Home") == "shardB:Main"
    assert state.resolve_alias("missing") is None


def test_fold_is_pure_function_of_log():
    log = DecisionLog()
    log.append("s", EventType.BINDING_MADE, {"members": ["shardA:Home", "shardB:Home"]})
    first = log.fold("s")
    second = log.fold("s")
    assert first.equivalence_groups == second.equivalence_groups  # derived = f(log)


def test_equivalence_groups_merge_transitively():
    log = DecisionLog()
    log.append("s", EventType.BINDING_MADE, {"members": ["a", "b"]})
    log.append("s", EventType.BINDING_MADE, {"members": ["b", "c"]})
    state = log.fold("s")
    assert state.equivalent_to("a") == frozenset({"a", "b", "c"})
    assert state.equivalent_to("lonely") == frozenset({"lonely"})


def test_page_fork_creates_equivalence():
    log = DecisionLog()
    log.append("s", EventType.PAGE_FORKED, {"source": "shardA:Doc", "fork": "shardB:Doc"})
    assert log.fold("s").equivalent_to("shardA:Doc") == frozenset({"shardA:Doc", "shardB:Doc"})