"""Tests for union resolution (SHARD-WP-0007 T6)."""

from shard_wiki.adapters import FolderAdapter
from shard_wiki.coordination import DecisionLog, EventType
from shard_wiki.policy import CanonicalSource, Policy
from shard_wiki.union import ResolutionKind, UnionGraph


def _shard(tmp_path, name, files):
    root = tmp_path / name
    for rel, text in files.items():
        p = root / rel
        p.parent.mkdir(parents=True, exist_ok=True)
        p.write_text(text, encoding="utf-8")
    return FolderAdapter(name, root)


def test_single_resolution(tmp_path):
    u = UnionGraph("space")
    u.attach(_shard(tmp_path, "shardA", {"Home.md": "A home"}))
    res = u.resolve("Home")
    assert res.kind is ResolutionKind.SINGLE
    assert res.single().body == "A home"


def test_red_link_when_absent(tmp_path):
    u = UnionGraph("space")
    u.attach(_shard(tmp_path, "shardA", {"Home.md": "x"}))
    assert u.resolve("Nope").is_red_link


def test_chorus_on_ambiguity_records_divergence(tmp_path):
    u = UnionGraph("space")
    u.attach(_shard(tmp_path, "shardA", {"Home.md": "A home"}))
    u.attach(_shard(tmp_path, "shardB", {"Home.md": "B home"}))
    res = u.resolve("Home")
    assert res.kind is ResolutionKind.CHORUS
    assert {p.body for p in res.pages} == {"A home", "B home"}
    # Each page names its divergent peer — union without erasure.
    a = next(p for p in res.pages if p.identity.shard == "shardA")
    assert a.envelope.divergence == ("shardB:Home",)


def test_designated_canonical_orders_first(tmp_path):
    policy = Policy(canonical_source=CanonicalSource.DESIGNATED_CANONICAL, designated_shard="shardB")
    u = UnionGraph("space", policy=policy)
    u.attach(_shard(tmp_path, "shardA", {"Home.md": "A"}))
    u.attach(_shard(tmp_path, "shardB", {"Home.md": "B"}))
    res = u.resolve("Home")
    assert res.kind is ResolutionKind.CHORUS
    assert res.single().identity.shard == "shardB"  # designated wins the canonical pick


def test_alias_from_log_redirects(tmp_path):
    log = DecisionLog()
    log.append("space", EventType.ALIAS_SET, {"alias": "Start", "target": "shardA:Index"})
    u = UnionGraph("space", log=log)
    u.attach(_shard(tmp_path, "shardA", {"Index.md": "the index"}))
    res = u.resolve("Start")
    assert res.kind is ResolutionKind.SINGLE
    assert res.single().body == "the index"


def test_dangling_alias_falls_through_to_red_link(tmp_path):
    log = DecisionLog()
    log.append("space", EventType.ALIAS_SET, {"alias": "Start", "target": "shardA:Missing"})
    u = UnionGraph("space", log=log)
    u.attach(_shard(tmp_path, "shardA", {"Index.md": "x"}))
    assert u.resolve("Start").is_red_link