"""8 breakage primitives representing real HuggingFace/PyTorch ecosystem drift.

Each primitive transforms a working script to simulate a library upgrade
breakage. They double as the Drift Generator's structured action space.
"""
from __future__ import annotations

import re
from abc import ABC, abstractmethod
from dataclasses import dataclass, field


@dataclass
class BreakagePrimitive(ABC):
    """Abstract base class for all breakage types."""

    category: str = field(default="generic", init=False)
    name: str = field(default="BreakagePrimitive", init=False)
    description: str = field(default="", init=False)

    @abstractmethod
    def apply(self, script: str) -> str:
        """Transform `script` to introduce the breakage."""

    def to_spec(self) -> dict:
        """Serialize to JSON-compatible spec for the LLM action space."""
        return {
            "primitive_type": self.__class__.__name__,
            "category": self.category,
            "params": self._get_params(),
        }

    @abstractmethod
    def _get_params(self) -> dict:
        """Return a JSON-serializable dict of constructor parameters."""


@dataclass
class RenameApiCall(BreakagePrimitive):
    """Rename a function/method call to simulate API deprecation."""

    old_name: str = ""
    new_name: str = ""

    def __post_init__(self) -> None:
        self.category = "api_drift"
        self.name = "RenameApiCall"
        self.description = f"Rename {self.old_name} -> {self.new_name}"

    def apply(self, script: str) -> str:
        if not self.old_name:
            return script
        # Use word-boundary replacement so we don't substring-match identifiers.
        pattern = re.compile(rf"(?<!\w){re.escape(self.old_name)}(?!\w)")
        return pattern.sub(self.new_name, script)

    def _get_params(self) -> dict:
        return {"old_name": self.old_name, "new_name": self.new_name}


@dataclass
class DeprecateImport(BreakagePrimitive):
    """Change an import path to simulate module restructuring."""

    old_module: str = ""
    new_module: str = ""

    def __post_init__(self) -> None:
        self.category = "import_drift"
        self.name = "DeprecateImport"
        self.description = f"Move {self.old_module} -> {self.new_module}"

    def apply(self, script: str) -> str:
        if not self.old_module:
            return script
        return script.replace(self.old_module, self.new_module)

    def _get_params(self) -> dict:
        return {"old_module": self.old_module, "new_module": self.new_module}


@dataclass
class ChangeArgumentSignature(BreakagePrimitive):
    """Remove an expected kwarg (and document a new required one)."""

    function_name: str = ""
    removed_arg: str = ""
    added_arg: str = ""
    added_value: str = ""

    def __post_init__(self) -> None:
        self.category = "api_drift"
        self.name = "ChangeArgumentSignature"
        self.description = (
            f"Change args of {self.function_name}: -{self.removed_arg} +{self.added_arg}"
        )

    def apply(self, script: str) -> str:
        if not self.removed_arg:
            return script
        pattern = rf"(\b{re.escape(self.removed_arg)}\s*=\s*[^,)]+,?\s*)"
        return re.sub(pattern, "", script)

    def _get_params(self) -> dict:
        return {
            "function_name": self.function_name,
            "removed_arg": self.removed_arg,
            "added_arg": self.added_arg,
            "added_value": self.added_value,
        }


@dataclass
class ModifyConfigField(BreakagePrimitive):
    """Change a config-class default value to simulate behaviour drift."""

    config_class: str = ""
    field_name: str = ""
    new_value: str = ""

    def __post_init__(self) -> None:
        self.category = "config_drift"
        self.name = "ModifyConfigField"
        self.description = f"Change {self.config_class}.{self.field_name}"

    def apply(self, script: str) -> str:
        if not self.field_name:
            return script
        pattern = rf"({re.escape(self.field_name)}\s*=\s*)([^,)\n]+)"
        return re.sub(pattern, rf"\g<1>{self.new_value}", script)

    def _get_params(self) -> dict:
        return {
            "config_class": self.config_class,
            "field_name": self.field_name,
            "new_value": self.new_value,
        }


@dataclass
class RestructureDatasetSchema(BreakagePrimitive):
    """Rename a dataset column reference to simulate schema drift."""

    old_column: str = ""
    new_column: str = ""

    def __post_init__(self) -> None:
        self.category = "dataset_drift"
        self.name = "RestructureDatasetSchema"
        self.description = f"Rename column {self.old_column} -> {self.new_column}"

    def apply(self, script: str) -> str:
        if not self.old_column:
            return script
        return script.replace(
            f'"{self.old_column}"', f'"{self.new_column}"'
        ).replace(
            f"'{self.old_column}'", f"'{self.new_column}'"
        )

    def _get_params(self) -> dict:
        return {"old_column": self.old_column, "new_column": self.new_column}


@dataclass
class ChangeTokenizerBehavior(BreakagePrimitive):
    """Change tokenizer call arguments."""

    old_kwarg: str = ""
    old_value: str = ""
    new_kwarg: str = ""
    new_value: str = ""

    def __post_init__(self) -> None:
        self.category = "tokenizer_drift"
        self.name = "ChangeTokenizerBehavior"
        self.description = f"Change tokenizer kwarg {self.old_kwarg}={self.old_value} -> {self.new_kwarg}={self.new_value}"

    def apply(self, script: str) -> str:
        if not self.old_kwarg:
            return script
        pattern = rf"{re.escape(self.old_kwarg)}\s*=\s*{re.escape(self.old_value)}"
        replacement = f"{self.new_kwarg}={self.new_value}"
        return re.sub(pattern, replacement, script)

    def _get_params(self) -> dict:
        return {
            "old_kwarg": self.old_kwarg,
            "old_value": self.old_value,
            "new_kwarg": self.new_kwarg,
            "new_value": self.new_value,
        }


@dataclass
class RemoveDeprecatedMethod(BreakagePrimitive):
    """Remove a method that has been deprecated, leaving a sentinel that
    raises AttributeError-style errors when the script runs."""

    class_name: str = ""
    method_name: str = ""
    replacement: str = ""

    def __post_init__(self) -> None:
        self.category = "api_drift"
        self.name = "RemoveDeprecatedMethod"
        self.description = f"Remove {self.class_name}.{self.method_name}"

    def apply(self, script: str) -> str:
        if not self.method_name:
            return script
        return script.replace(
            f".{self.method_name}(", f".{self.method_name}_DEPRECATED("
        )

    def _get_params(self) -> dict:
        return {
            "class_name": self.class_name,
            "method_name": self.method_name,
            "replacement": self.replacement,
        }


@dataclass
class ChangeReturnType(BreakagePrimitive):
    """A function now returns a different structure (e.g. tuple -> object)."""

    function_name: str = ""
    old_access: str = ""
    new_access: str = ""

    def __post_init__(self) -> None:
        self.category = "api_drift"
        self.name = "ChangeReturnType"
        self.description = f"Change return type of {self.function_name}"

    def apply(self, script: str) -> str:
        if self.old_access and self.new_access:
            return script.replace(self.old_access, self.new_access)
        return script

    def _get_params(self) -> dict:
        return {
            "function_name": self.function_name,
            "old_access": self.old_access,
            "new_access": self.new_access,
        }


PRIMITIVE_REGISTRY: dict[str, type[BreakagePrimitive]] = {
    "RenameApiCall": RenameApiCall,
    "DeprecateImport": DeprecateImport,
    "ChangeArgumentSignature": ChangeArgumentSignature,
    "ModifyConfigField": ModifyConfigField,
    "RestructureDatasetSchema": RestructureDatasetSchema,
    "ChangeTokenizerBehavior": ChangeTokenizerBehavior,
    "RemoveDeprecatedMethod": RemoveDeprecatedMethod,
    "ChangeReturnType": ChangeReturnType,
}


def parse_breakage_spec(spec: dict) -> BreakagePrimitive:
    """Parse a JSON breakage spec into a BreakagePrimitive object.

    Tolerates extra keys; ignores unknown params (LLMs hallucinate these).
    """
    ptype = spec.get("primitive_type", "")
    params = spec.get("params", {}) or {}

    if ptype not in PRIMITIVE_REGISTRY:
        raise ValueError(
            f"Unknown primitive type: {ptype!r}. "
            f"Valid types: {list(PRIMITIVE_REGISTRY)}"
        )

    cls = PRIMITIVE_REGISTRY[ptype]
    # Filter to known fields only so a hallucinated kwarg can't crash us.
    valid_fields = {
        f.name for f in cls.__dataclass_fields__.values() if f.init  # type: ignore[attr-defined]
    }
    filtered = {k: v for k, v in params.items() if k in valid_fields}
    return cls(**filtered)