"""Tests for services.embeddings — fastembed backend.

We don't actually load the fastembed model in tests (heavy download).
Instead, mock _get_model to return a fake that produces deterministic vectors.
"""
from unittest.mock import AsyncMock, MagicMock, patch

import pytest

from scribe.services.embeddings import (
    _cosine_similarity, get_embedding,
)


# ─── cosine_similarity (pure logic) ──────────────────────────────────────────


def test_cosine_similarity_orthogonal_is_zero():
    assert _cosine_similarity([1.0, 0.0], [0.0, 1.0]) == 0.0


def test_cosine_similarity_identical_is_one():
    assert _cosine_similarity([1.0, 0.0], [1.0, 0.0]) == pytest.approx(1.0)


def test_cosine_similarity_opposite_is_negative_one():
    assert _cosine_similarity([1.0, 0.0], [-1.0, 0.0]) == pytest.approx(-1.0)


def test_cosine_similarity_zero_length_safe():
    """Zero-magnitude vector must not divide-by-zero."""
    assert _cosine_similarity([0.0, 0.0], [1.0, 0.0]) == 0.0
    assert _cosine_similarity([1.0, 0.0], [0.0, 0.0]) == 0.0


def test_cosine_similarity_mismatched_dim_returns_zero():
    """Cross-migration safety: a 768-dim vs 384-dim comparison must not crash."""
    assert _cosine_similarity([1.0] * 5, [1.0] * 3) == 0.0


def test_cosine_similarity_empty_inputs():
    assert _cosine_similarity([], []) == 0.0
    assert _cosine_similarity([], [1.0]) == 0.0


# ─── get_embedding (fastembed path) ──────────────────────────────────────────


@pytest.mark.asyncio
async def test_get_embedding_returns_list_of_floats():
    """get_embedding wraps the embedder; the result is a Python list of floats."""
    fake_vec = MagicMock()
    fake_vec.tolist.return_value = [0.1, 0.2, 0.3, 0.4]
    fake_embedder = MagicMock()
    fake_embedder.embed = MagicMock(return_value=iter([fake_vec]))
    with patch(
        "scribe.services.embeddings._get_model",
        AsyncMock(return_value=fake_embedder),
    ):
        out = await get_embedding("hello world")
    assert out == [0.1, 0.2, 0.3, 0.4]
    fake_embedder.embed.assert_called_once_with(["hello world"])


@pytest.mark.asyncio
async def test_get_embedding_propagates_model_load_failures():
    """If fastembed can't initialize, the error propagates — callers catch
    and degrade to keyword search."""
    with patch(
        "scribe.services.embeddings._get_model",
        AsyncMock(side_effect=RuntimeError("model load failed")),
    ):
        with pytest.raises(RuntimeError, match="model load failed"):
            await get_embedding("x")


# ─── query_embedding_memo (milestone 456 step 1) ─────────────────────────────


def _counting_embeddings():
    """A stand-in for get_embeddings that counts model calls and returns a
    vector derived from the text, so a wrong memo key returns a wrong vector."""
    calls: list[list[str]] = []

    async def fake(texts):
        calls.append(list(texts))
        return [[float(len(t)), 1.0] for t in texts]

    return fake, calls


@pytest.mark.asyncio
async def test_memo_embeds_a_repeated_query_once_per_scope():
    from scribe.services import embeddings as emb

    fake, calls = _counting_embeddings()
    with patch.object(emb, "get_embeddings", fake):
        with emb.query_embedding_memo():
            first = await emb.get_embedding("push to dev")
            again = await emb.get_embedding("push to dev")
            other = await emb.get_embedding("merge to main")
    assert first == again == [11.0, 1.0]
    assert other == [13.0, 1.0]
    assert calls == [["push to dev"], ["merge to main"]]


@pytest.mark.asyncio
async def test_without_a_scope_every_call_reaches_the_model():
    """The default is None: outside a request scope nothing is remembered, so
    every caller other than the plugin routes behaves exactly as before."""
    from scribe.services import embeddings as emb

    fake, calls = _counting_embeddings()
    with patch.object(emb, "get_embeddings", fake):
        await emb.get_embedding("q")
        await emb.get_embedding("q")
    assert calls == [["q"], ["q"]]


@pytest.mark.asyncio
async def test_a_scope_does_not_leak_into_the_next_one():
    from scribe.services import embeddings as emb

    fake, calls = _counting_embeddings()
    with patch.object(emb, "get_embeddings", fake):
        with emb.query_embedding_memo():
            await emb.get_embedding("q")
        with emb.query_embedding_memo():
            await emb.get_embedding("q")
        await emb.get_embedding("q")
    assert calls == [["q"], ["q"], ["q"]]
    assert emb._query_memo.get() is None


@pytest.mark.asyncio
async def test_a_failed_embedding_is_not_remembered():
    """The next arm in the request must try again and degrade on its own,
    not inherit a failure as if it were a vector."""
    from scribe.services import embeddings as emb

    attempts = {"n": 0}

    async def flaky(texts):
        attempts["n"] += 1
        if attempts["n"] == 1:
            raise RuntimeError("model busy")
        return [[0.5, 0.5] for _ in texts]

    with patch.object(emb, "get_embeddings", flaky):
        with emb.query_embedding_memo():
            with pytest.raises(RuntimeError):
                await emb.get_embedding("q")
            assert await emb.get_embedding("q") == [0.5, 0.5]
    assert attempts["n"] == 2


@pytest.mark.asyncio
async def test_the_route_decorator_opens_one_scope_per_call():
    from scribe.services import embeddings as emb

    fake, calls = _counting_embeddings()

    @emb.memoized_query_embeddings
    async def handler(q):
        await emb.get_embedding(q)
        await emb.get_embedding(q)
        return emb._query_memo.get() is not None

    with patch.object(emb, "get_embeddings", fake):
        assert await handler("a") is True
        assert await handler("a") is True
    assert calls == [["a"], ["a"]]
    assert handler.__name__ == "handler"