"""Tests for fairchem.core.models.uma.compat — UMA generation classifier
and in-place ``model_id`` back-fill.
"""

from __future__ import annotations

import pytest

from fairchem.core.models.uma.compat import (
    UMA_1P1_MODEL_ID,
    apply_uma_compat_fixups,
    get_uma_version,
)
from fairchem.core.units.mlip_unit.api.inference import MLIPInferenceCheckpoint

UMA_BACKBONE_FQN = "fairchem.core.models.uma.escn_moe.eSCNMDMoeBackbone"
UMA_BACKBONE_SHORT = "escnmd_moe_backbone"


def make_fake_checkpoint(model_config) -> MLIPInferenceCheckpoint:
    """Build a real ``MLIPInferenceCheckpoint`` with empty state for tests."""
    return MLIPInferenceCheckpoint(
        model_config=model_config,
        model_state_dict={},
        ema_state_dict={},
        tasks_config={},
    )


def uma_cfg(
    *, model_version=None, model_id=None, backbone_model=UMA_BACKBONE_FQN, num_experts=8
):
    # num_experts>0 by default: real UMA checkpoints are MoE. The shim treats a
    # shared-backbone checkpoint with num_experts==0 (e.g. eSEN) as not_uma.
    cfg = {"backbone": {"model": backbone_model, "num_experts": num_experts}}
    if model_version is not None:
        cfg["backbone"]["model_version"] = model_version
    if model_id is not None:
        cfg["model_id"] = model_id
    return cfg


# ---------------------------------------------------------------------------
# UMA 1.0 / untagged (neither model_id nor model_version) — hard fail
# ---------------------------------------------------------------------------


def test_unidentified_raises():
    """No model_id and no model_version -> cannot classify -> raise.

    This is the on-disk signature of a deprecated UMA 1.0 checkpoint (which ships
    with neither field) and of an untagged freshly-trained model.
    """
    cfg = uma_cfg()  # no model_id, no model_version
    ckpt = make_fake_checkpoint(cfg)
    with pytest.raises(RuntimeError) as exc_info:
        apply_uma_compat_fixups(ckpt, checkpoint_location="/path/to/uma-s-1.pt")
    msg = str(exc_info.value)
    assert "no model_id" in msg
    assert "fairchem-core<=2.21.0" in msg  # names the deprecated-1.0 possibility
    assert "/path/to/uma-s-1.pt" in msg


# ---------------------------------------------------------------------------
# UMA 1.1 — classification + back-fill
# ---------------------------------------------------------------------------


def test_uma_1p1_string_model_version_backfills():
    cfg = uma_cfg(model_version="1.1")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt, checkpoint_location="/p.pt")
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


def test_uma_1p1_float_model_version_backfills():
    cfg = uma_cfg(model_version=1.1)
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


def test_uma_1p1_idempotent_bare():
    cfg = uma_cfg(model_version="1.1", model_id=UMA_1P1_MODEL_ID)
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


@pytest.mark.parametrize("subsize_id", ["UMA-S-1.1", "UMA-M-1.1", "UMA-L-1.1"])
def test_uma_1p1_model_id_not_reclassified(subsize_id):
    """A checkpoint that already has a model_id is 'tagged' (no-op); it is never
    re-back-filled, regardless of what the model_id says."""
    cfg = uma_cfg(model_version="1.1", model_id=subsize_id)
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "tagged"
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == subsize_id  # untouched


# ---------------------------------------------------------------------------
# UMA 1.2 — no-op
# ---------------------------------------------------------------------------


def test_uma_1p2_no_op():
    cfg = uma_cfg(model_id="UMA-S-1.2")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == "UMA-S-1.2"


def test_uma_1p2_bare_no_op():
    cfg = uma_cfg(model_id="UMA-1.2")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == "UMA-1.2"


# ---------------------------------------------------------------------------
# Unknown / user-customized / non-UMA
# ---------------------------------------------------------------------------


def test_future_model_id_tagged_no_op():
    """A future/unknown model_id (e.g. UMA-1.3) is 'tagged' → no-op, untouched.
    (Its include_self is decided by the backbone from model_id.)"""
    cfg = uma_cfg(model_id="UMA-1.3")
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "tagged"
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == "UMA-1.3"  # untouched


def test_user_customized_model_id_preserved():
    cfg = uma_cfg(model_version="1.1", model_id="my-cool-finetune")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == "my-cool-finetune"


def test_non_uma_no_op():
    cfg = {"backbone": {"model": "fairchem.core.models.esen.esen_backbone.ESEN"}}
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "not_uma"
    apply_uma_compat_fixups(ckpt)
    assert "model_id" not in ckpt.model_config


@pytest.mark.parametrize("num_experts", [0, None])
def test_shared_backbone_without_experts_is_not_uma(num_experts):
    """A checkpoint that reuses eSCNMDMoeBackbone but has no MoE experts (e.g.
    eSEN OC25: num_experts=0, model_version=1.0, no model_id) must NOT be treated
    as an untagged UMA 1.0 checkpoint — it has no model_id-gated MoE path, so it
    loads unchanged rather than raising."""
    cfg = uma_cfg(model_version=1.0, num_experts=num_experts)
    if num_experts is None:
        del cfg["backbone"]["num_experts"]
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "not_uma"
    apply_uma_compat_fixups(ckpt)  # must not raise
    assert "model_id" not in ckpt.model_config


def test_short_registry_name_backbone():
    cfg = uma_cfg(model_version="1.1", backbone_model=UMA_BACKBONE_SHORT)
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "1.1"
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


def test_none_model_config():
    ckpt = make_fake_checkpoint(None)
    assert get_uma_version(None) == "not_uma"
    apply_uma_compat_fixups(ckpt)  # must not raise


def test_empty_backbone_dict_treated_as_not_uma():
    cfg = {"backbone": {}}
    ckpt = make_fake_checkpoint(cfg)
    assert get_uma_version(cfg) == "not_uma"
    apply_uma_compat_fixups(ckpt)
    assert "model_id" not in ckpt.model_config


def test_empty_string_model_id_treated_as_absent():
    cfg = uma_cfg(model_version="1.1", model_id="")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


def test_whitespace_model_id_treated_as_absent():
    cfg = uma_cfg(model_version="1.1", model_id="   ")
    ckpt = make_fake_checkpoint(cfg)
    apply_uma_compat_fixups(ckpt)
    assert ckpt.model_config["model_id"] == UMA_1P1_MODEL_ID


# ---------------------------------------------------------------------------
# 1.2 size variant is tagged (no-op); the backbone decides its include_self
# ---------------------------------------------------------------------------


def test_uma_1p2_m_variant_tagged():
    assert get_uma_version(uma_cfg(model_id="UMA-M-1.2")) == "tagged"