"""Factory for creating and registering processors with unified interface."""

from dataclasses import dataclass
from typing import Dict, List, Optional, Type, Union

from pipeline.processors.base import BaseProcessor
from pipeline.tokenize import AutoTokenizer
from pipeline.strategies import PromptStrategy, StrategyFactory


@dataclass
class ProcessorConfig:
    """Configuration for creating a processor.

    Attributes:
        processor_type: Type name for the processor ("pt", "sft", "dpo").
        tokenizer: Tokenizer instance (required).
        strategy_name: Name of the strategy to use (optional).
        strategy: Pre-created strategy instance (optional).
        strategy_kwargs: Additional arguments for strategy creation.
    """

    processor_type: str
    tokenizer: AutoTokenizer
    strategy_name: Optional[str] = None
    strategy: Optional[PromptStrategy] = None
    strategy_kwargs: Optional[Dict] = None


class ProcessorFactory:
    """Registry and factory for BaseProcessor implementations.

    Supports decorator-based registration for extensible processor types.

    Example usage::

        @ProcessorFactory.register("custom")
        class CustomProcessor(BaseProcessor):
            ...

        # Using config object (recommended)
        config = ProcessorConfig(
            processor_type="sft",
            tokenizer=tokenizer,
            strategy_name="alpaca"
        )
        processor = ProcessorFactory.create_from_config(config)

        # Using direct arguments
        processor = ProcessorFactory.create("pt", tokenizer)
    """

    PROCESSOR_MAP: Dict[str, Type[BaseProcessor]] = {}

    @classmethod
    def register(cls, name: str):
        """Decorator to register a new processor class.

        Args:
            name: Registration name for the processor.

        Returns:
            Decorator function that registers the processor class.
        """

        def decorator(processor_cls: Type[BaseProcessor]) -> Type[BaseProcessor]:
            if not issubclass(processor_cls, BaseProcessor):
                raise TypeError(
                    f"{processor_cls.__name__} must inherit from BaseProcessor"
                )
            cls.PROCESSOR_MAP[name] = processor_cls
            return processor_cls

        return decorator

    @classmethod
    def create(cls, processor_type: str, tokenizer: AutoTokenizer) -> BaseProcessor:
        """Create a processor by type name.

        Args:
            processor_type: Registered processor name (e.g. "pt", "sft", "dpo").
            tokenizer: Tokenizer instance.

        Returns:
            Processor instance.

        Raises:
            ValueError: If processor_type is not registered.
        """
        if processor_type not in cls.PROCESSOR_MAP:
            raise ValueError(
                f"Unknown processor type: '{processor_type}'. "
                f"Supported types: {sorted(cls.PROCESSOR_MAP.keys())}"
            )
        return cls.PROCESSOR_MAP[processor_type](tokenizer)

    @classmethod
    def create_with_strategy(
        cls,
        processor_type: str,
        tokenizer: AutoTokenizer,
        strategy: PromptStrategy,
    ) -> BaseProcessor:
        """Create a processor with a pre-configured strategy.

        Args:
            processor_type: Registered processor name.
            tokenizer: Tokenizer instance.
            strategy: Pre-created strategy instance.

        Returns:
            Processor instance configured with strategy.
        """
        if processor_type not in cls.PROCESSOR_MAP:
            raise ValueError(
                f"Unknown processor type: '{processor_type}'. "
                f"Supported types: {sorted(cls.PROCESSOR_MAP.keys())}"
            )

        processor_cls = cls.PROCESSOR_MAP[processor_type]
        if processor_type == "pt":
            return processor_cls(tokenizer)
        return processor_cls(tokenizer, strategy=strategy)

    @classmethod
    def create_with_strategy_name(
        cls,
        processor_type: str,
        tokenizer: AutoTokenizer,
        strategy_name: str,
        **strategy_kwargs,
    ) -> BaseProcessor:
        """Create a processor with a strategy selected by name.

        Args:
            processor_type: Registered processor name.
            tokenizer: Tokenizer instance.
            strategy_name: Registered strategy name ("chatml", "alpaca", etc.).
            **strategy_kwargs: Additional arguments forwarded to strategy constructor.

        Returns:
            Processor instance.
        """
        strategy = StrategyFactory.create(strategy_name, tokenizer, **strategy_kwargs)
        return cls.create_with_strategy(processor_type, tokenizer, strategy)

    @classmethod
    def create_from_config(cls, config: ProcessorConfig) -> BaseProcessor:
        """Create a processor from a configuration object (unified interface).

        Args:
            config: ProcessorConfig with all creation parameters.

        Returns:
            Processor instance.

        Raises:
            ValueError: If processor_type is not registered or strategy is invalid.
        """
        if config.processor_type not in cls.PROCESSOR_MAP:
            raise ValueError(
                f"Unknown processor type: '{config.processor_type}'. "
                f"Supported types: {sorted(cls.PROCESSOR_MAP.keys())}"
            )

        tokenizer = config.tokenizer
        strategy_kwargs = config.strategy_kwargs or {}

        # Determine strategy to use
        strategy: Optional[PromptStrategy] = None
        if config.strategy is not None:
            strategy = config.strategy
        elif config.strategy_name is not None:
            strategy = StrategyFactory.create(
                config.strategy_name, tokenizer, **strategy_kwargs
            )

        # Create processor
        if strategy is not None:
            return cls.create_with_strategy(
                config.processor_type, tokenizer, strategy
            )
        return cls.create(config.processor_type, tokenizer)

    @classmethod
    def available_types(cls) -> List[str]:
        """Return list of registered processor type names."""
        return list(cls.PROCESSOR_MAP.keys())