from __future__ import annotations

from collections.abc import Mapping, Sequence
from pathlib import Path
from typing import Any

import torch

from .config import TrainConfig
from .model import TextToLatentRFDiT

LORA_TRAIN_CONFIG_FIELDS = (
    "lora_enabled",
    "lora_r",
    "lora_alpha",
    "lora_dropout",
    "lora_bias",
    "lora_target_modules",
    "lora_modules_to_save",
)

LORA_ADAPTER_CONFIG_NAME = "adapter_config.json"
LORA_ADAPTER_STATE_NAMES = ("adapter_model.safetensors", "adapter_model.bin")
LORA_TRAINER_STATE_NAME = "trainer_state.pt"
LORA_METADATA_NAME = "irodori_lora_metadata.json"

LORA_TARGET_PRESETS: dict[str, str] = {
    "text_attn_mlp": (
        r"^text_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))$"
    ),
    "caption_attn_mlp": (
        r"^caption_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))$"
    ),
    "speaker_attn_mlp": (
        r"^(speaker_encoder\.in_proj"
        r"|speaker_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3)))$"
    ),
    "diffusion_attn": (
        r"^blocks\.\d+\.attention\."
        r"(wq|wk|wv|wo|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate)$"
    ),
    "diffusion_attn_mlp": (
        r"^blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate)"
        r"|mlp\.(w1|w2|w3))$"
    ),
    "all_attn": (
        r"^(text_encoder\.blocks\.\d+\.attention\.(wq|wk|wv|wo|gate)"
        r"|caption_encoder\.blocks\.\d+\.attention\.(wq|wk|wv|wo|gate)"
        r"|speaker_encoder\.blocks\.\d+\.attention\.(wq|wk|wv|wo|gate)"
        r"|blocks\.\d+\.attention\.(wq|wk|wv|wo|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate))$"
    ),
    "diffusion_full": (
        r"^(cond_module\.(0|2|4)"
        r"|in_proj"
        r"|out_proj"
        r"|blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate)"
        r"|mlp\.(w1|w2|w3)"
        r"|attention_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up)"
        r"|mlp_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up)))$"
    ),
    "adaln": (
        r"^blocks\.\d+\."
        r"(attention_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up)"
        r"|mlp_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up))$"
    ),
    "conditioning": (
        r"^(cond_module\.(0|2|4)"
        r"|speaker_encoder\.in_proj"
        r"|blocks\.\d+\.attention\.(wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption))$"
    ),
    "all_attn_mlp": (
        r"^(text_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|caption_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|speaker_encoder\.in_proj"
        r"|speaker_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate)"
        r"|mlp\.(w1|w2|w3)))$"
    ),
    "all_linear": (
        r"^(speaker_encoder\.in_proj"
        r"|cond_module\.(0|2|4)"
        r"|in_proj"
        r"|out_proj"
        r"|text_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|caption_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|speaker_encoder\.blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wo|gate)|mlp\.(w1|w2|w3))"
        r"|blocks\.\d+\."
        r"(attention\.(wq|wk|wv|wk_text|wv_text|wk_speaker|wv_speaker|wk_caption|wv_caption|gate|wo)"
        r"|mlp\.(w1|w2|w3)"
        r"|attention_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up)"
        r"|mlp_adaln\.(shift_down|scale_down|gate_down|shift_up|scale_up|gate_up)))$"
    ),
}


def _require_peft():
    try:
        from peft import LoraConfig, PeftModel, get_peft_model
    except ImportError as exc:
        raise RuntimeError(
            "LoRA fine-tuning requires `peft`. Install with `pip install peft` or `uv sync`."
        ) from exc
    return LoraConfig, PeftModel, get_peft_model


def _lookup_config_value(raw: TrainConfig | Mapping[str, Any] | None, field: str) -> Any:
    if raw is None:
        return getattr(TrainConfig(), field)
    if isinstance(raw, TrainConfig):
        return getattr(raw, field)
    if isinstance(raw, Mapping):
        if field in raw:
            return raw[field]
        return getattr(TrainConfig(), field)
    raise TypeError(f"Unsupported LoRA config source: {type(raw)!r}")


def train_config_uses_lora(raw: TrainConfig | Mapping[str, Any] | None) -> bool:
    return bool(_lookup_config_value(raw, "lora_enabled"))


def checkpoint_state_uses_lora(model_state: Mapping[str, torch.Tensor]) -> bool:
    return any(key.startswith("base_model.model.") or ".lora_" in key for key in model_state)


def resolve_lora_target_modules(spec: str | Sequence[str] | None) -> str | list[str]:
    if spec is None:
        spec = TrainConfig().lora_target_modules

    if isinstance(spec, str):
        value = spec.strip()
        if not value:
            raise ValueError("lora_target_modules must not be empty.")
        preset = LORA_TARGET_PRESETS.get(value)
        if preset is not None:
            return preset
        if "," in value:
            modules = [chunk.strip() for chunk in value.split(",") if chunk.strip()]
            if not modules:
                raise ValueError(f"Invalid LoRA target_modules list: {spec!r}")
            return modules
        return value

    modules = [str(item).strip() for item in spec if str(item).strip()]
    if not modules:
        raise ValueError("LoRA target_modules sequence must not be empty.")
    return modules


def resolve_lora_modules_to_save(
    spec: str | Sequence[str] | None,
    *,
    use_duration_predictor: bool,
) -> list[str] | None:
    if spec is None:
        return None

    if isinstance(spec, str):
        value = spec.strip()
        if not value or value.lower() == "none":
            return None
        if value.lower() == "auto":
            if use_duration_predictor:
                return ["duration_predictor"]
            return None
        modules = [chunk.strip() for chunk in value.split(",") if chunk.strip()]
    else:
        modules = [str(item).strip() for item in spec if str(item).strip()]

    if not modules:
        return None
    return modules


def build_lora_config_kwargs(
    raw: TrainConfig | Mapping[str, Any],
    *,
    use_duration_predictor: bool = False,
) -> dict[str, Any]:
    bias = str(_lookup_config_value(raw, "lora_bias")).strip().lower()
    if bias not in {"none", "all", "lora_only"}:
        raise ValueError(f"Unsupported lora_bias={bias!r}. Expected one of: none, all, lora_only.")

    kwargs = {
        "r": int(_lookup_config_value(raw, "lora_r")),
        "lora_alpha": int(_lookup_config_value(raw, "lora_alpha")),
        "lora_dropout": float(_lookup_config_value(raw, "lora_dropout")),
        "bias": bias,
        "target_modules": resolve_lora_target_modules(
            _lookup_config_value(raw, "lora_target_modules")
        ),
    }
    modules_to_save = resolve_lora_modules_to_save(
        _lookup_config_value(raw, "lora_modules_to_save"),
        use_duration_predictor=use_duration_predictor,
    )
    if modules_to_save is not None:
        kwargs["modules_to_save"] = modules_to_save
    return kwargs


def apply_lora(
    model: TextToLatentRFDiT,
    raw: TrainConfig | Mapping[str, Any],
) -> torch.nn.Module:
    if not train_config_uses_lora(raw):
        return model

    lora_config_cls, _, get_peft_model = _require_peft()
    peft_model = get_peft_model(
        model,
        lora_config_cls(
            task_type=None,
            inference_mode=False,
            **build_lora_config_kwargs(
                raw,
                use_duration_predictor=bool(model.cfg.use_duration_predictor),
            ),
        ),
    )
    return peft_model


def is_lora_adapter_dir(path: str | Path) -> bool:
    candidate = Path(path)
    if not candidate.is_dir():
        return False
    if not (candidate / LORA_ADAPTER_CONFIG_NAME).is_file():
        return False
    return any((candidate / name).is_file() for name in LORA_ADAPTER_STATE_NAMES)


def load_lora_adapter(
    model: TextToLatentRFDiT,
    adapter_path: str | Path,
    *,
    is_trainable: bool,
) -> torch.nn.Module:
    _, peft_model_cls, _ = _require_peft()
    return peft_model_cls.from_pretrained(model, str(adapter_path), is_trainable=is_trainable)


def count_parameters(model: torch.nn.Module) -> tuple[int, int]:
    trainable = sum(int(param.numel()) for param in model.parameters() if param.requires_grad)
    total = sum(int(param.numel()) for param in model.parameters())
    return trainable, total