"""
Unit tests for the loading module in the Speculators library.
"""

import pytest
import torch
from transformers import AutoModelForCausalLM

from speculators.utils.loading import (
    _resolve_file,
    _resolve_key,
    is_config_only_dir,
    load_model_layers,
)

# Test model from HuggingFace
TEST_MODEL_REPO = "nm-testing/tiny-testing-random-weights"
SMALL_MODEL_REPO = "nm-testing/tinysmokellama-3.2"

# is_config_only_dir Tests


@pytest.mark.smoke
def test_is_config_only_dir(tmp_path):
    # Missing directory and a directory without config.json are not config-only.
    assert is_config_only_dir(tmp_path / "does-not-exist") is False
    assert is_config_only_dir(tmp_path) is False

    # config.json present, no weights -> config-only.
    (tmp_path / "config.json").write_text("{}")
    assert is_config_only_dir(tmp_path) is True

    # A weight file makes it a full checkpoint.
    (tmp_path / "model.safetensors").write_text("")
    assert is_config_only_dir(tmp_path) is False


@pytest.mark.smoke
def test_is_config_only_dir_detects_bin_weights(tmp_path):
    (tmp_path / "config.json").write_text("{}")
    (tmp_path / "pytorch_model.bin").write_text("")

    assert is_config_only_dir(tmp_path) is False


@pytest.mark.smoke
@pytest.mark.parametrize(
    "index_file",
    ["model.safetensors.index.json", "pytorch_model.bin.index.json"],
)
def test_is_config_only_dir_detects_sharded_index(tmp_path, index_file):
    # A sharded-checkpoint manifest ends in .json (so it dodges the *.safetensors /
    # *.bin globs); it must still count as weights, not config-only.
    (tmp_path / "config.json").write_text("{}")
    (tmp_path / index_file).write_text("{}")

    assert is_config_only_dir(tmp_path) is False


# _resolve_key Tests


FAKE_WEIGHT_MAP = {
    "model.embed_tokens.weight": "shard-0.safetensors",
    "model.layers.0.self_attn.q_proj.weight": "shard-0.safetensors",
    "tok_embeddings.weight": "shard-1.safetensors",
    "output.weight": "shard-1.safetensors",
    "norm.weight": "shard-1.safetensors",
}


@pytest.mark.smoke
def test_resolve_key_exact_match():
    assert _resolve_key("model.embed_tokens.weight", FAKE_WEIGHT_MAP) == (
        "model.embed_tokens.weight"
    )


@pytest.mark.smoke
def test_resolve_key_suffix_match():
    assert _resolve_key("self_attn.q_proj.weight", FAKE_WEIGHT_MAP) == (
        "model.layers.0.self_attn.q_proj.weight"
    )


@pytest.mark.smoke
def test_resolve_key_alias_exact():
    wm = {"tok_embeddings.weight": "shard.safetensors"}
    assert _resolve_key("embed_tokens.weight", wm) == "tok_embeddings.weight"


@pytest.mark.smoke
def test_resolve_key_alias_suffix():
    wm = {"model.tok_embeddings.weight": "shard.safetensors"}
    assert _resolve_key("embed_tokens.weight", wm) == "model.tok_embeddings.weight"


@pytest.mark.smoke
def test_resolve_key_all_aliases():
    wm_lm = {"output.weight": "s.safetensors"}
    assert _resolve_key("lm_head.weight", wm_lm) == "output.weight"

    wm_norm = {"norm.weight": "s.safetensors"}
    assert _resolve_key("model.norm.weight", wm_norm) == "norm.weight"


@pytest.mark.smoke
def test_resolve_key_miss():
    assert _resolve_key("nonexistent.weight", FAKE_WEIGHT_MAP) is None


@pytest.mark.smoke
def test_resolve_key_prefers_exact_over_alias():
    wm = {
        "embed_tokens.weight": "shard-0.safetensors",
        "tok_embeddings.weight": "shard-1.safetensors",
    }
    assert _resolve_key("embed_tokens.weight", wm) == "embed_tokens.weight"


@pytest.mark.smoke
def test_resolve_key_prefers_shortest_suffix():
    """When several keys share the searched suffix, the shortest (most specific)
    one wins via ``min(matches, key=len)``.

    None of the keys match an alias here, so resolution falls through to the
    generic ``norm.weight`` suffix scan and the tie-break is exercised directly
    rather than short-circuited by an alias hit (see ``test_resolve_key_llm_aliases``
    for the alias path).
    """
    wm = {
        "model.audio.final_norm.weight": "shard-a.safetensors",
        "model.text.norm.weight": "shard-b.safetensors",
    }
    # Both keys end in "norm.weight" (reached via the model.norm.weight ->
    # norm.weight alias); the shorter, more-specific key must win over the audio
    # tower's norm.
    assert _resolve_key("model.norm.weight", wm) == "model.text.norm.weight"


@pytest.mark.smoke
def test_resolve_key_llm_aliases():
    """Inkling-style keys with llm. prefix resolve correctly."""
    wm = {
        "model.llm.embed.weight": "shard-0.safetensors",
        "model.llm.unembed.weight": "shard-1.safetensors",
        "model.llm.norm.weight": "shard-2.safetensors",
    }
    assert _resolve_key("embed_tokens.weight", wm) == "model.llm.embed.weight"
    assert _resolve_key("lm_head.weight", wm) == "model.llm.unembed.weight"
    assert _resolve_key("model.norm.weight", wm) == "model.llm.norm.weight"


# _resolve_file Tests


@pytest.mark.sanity
def test_resolve_file_hub_download():
    """Test resolving a file from HuggingFace Hub using real model."""
    result = _resolve_file(TEST_MODEL_REPO, "config.json")

    assert result.exists()
    assert result.name == "config.json"


# load_model_layers Tests


@pytest.mark.sanity
@pytest.mark.parametrize(
    "test_model_repo",
    [
        TEST_MODEL_REPO,  # Multi-shard model
        SMALL_MODEL_REPO,  # Single-shard model
    ],
)
def test_load_model(test_model_repo: str):
    """Test loading layers from a model repository."""
    result = load_model_layers(
        ["model.embed_tokens.weight", "lm_head.weight"],
        test_model_repo,
    )

    assert len(result) == 2
    assert "model.embed_tokens.weight" in result
    assert "lm_head.weight" in result
    assert isinstance(result["model.embed_tokens.weight"], torch.Tensor)
    assert isinstance(result["lm_head.weight"], torch.Tensor)
    # Both should have same vocab dimension
    assert (
        result["model.embed_tokens.weight"].shape[0]
        == result["lm_head.weight"].shape[0]
    )
    # Verify CPU device
    assert result["model.embed_tokens.weight"].device.type == "cpu"


@pytest.mark.sanity
def test_load_model_layers_matches_full_model():
    """Test that tensors loaded via utility match those from full model loading."""
    # Load full model
    full_model = AutoModelForCausalLM.from_pretrained(
        TEST_MODEL_REPO,
        torch_dtype="auto",
    )

    # Get state dict from full model
    state_dict = full_model.state_dict()

    # Load specific layers using our utility
    layer_names = [
        "model.embed_tokens.weight",
        "lm_head.weight",
        "model.norm.weight",
        "model.layers.0.input_layernorm.weight",
        "model.layers.0.mlp.gate_proj.weight",
        "model.layers.1.mlp.down_proj.weight",
    ]

    loaded_tensors = load_model_layers(layer_names, TEST_MODEL_REPO)

    # Compare each tensor
    for layer_name in layer_names:
        assert layer_name in loaded_tensors, f"Layer {layer_name} not loaded"
        assert layer_name in state_dict, f"Layer {layer_name} not in state_dict"

        util_tensor = loaded_tensors[layer_name]
        model_tensor = state_dict[layer_name]

        # Check dtype matches
        assert util_tensor.dtype == model_tensor.dtype, (
            f"Dtype mismatch for {layer_name}: "
            f"{util_tensor.dtype} vs {model_tensor.dtype}"
        )

        # Check shape matches
        assert util_tensor.shape == model_tensor.shape, (
            f"Shape mismatch for {layer_name}: "
            f"{util_tensor.shape} vs {model_tensor.shape}"
        )

        # Check values are identical
        assert torch.equal(util_tensor, model_tensor), (
            f"Tensor values don't match for {layer_name}"
        )