"""BabyAI level registry and curriculum definitions for MiniGridEnv."""

from __future__ import annotations

from dataclasses import dataclass, field


@dataclass(frozen=True)
class LevelConfig:
    """Configuration for a single BabyAI level."""

    gym_id: str
    name: str
    description: str
    difficulty: int
    max_steps: int
    expected_optimal_steps: int
    requires_interaction: bool
    num_objects: int
    involves_language_composition: bool
    fallback_gym_ids: tuple[str, ...] = ()

    @property
    def candidate_gym_ids(self) -> list[str]:
        return [self.gym_id, *self.fallback_gym_ids]


LEVEL_REGISTRY: list[LevelConfig] = [
    # Stage 0: simple navigation
    LevelConfig(
        gym_id="BabyAI-GoToRedBallGrey-v0",
        fallback_gym_ids=("BabyAI-GoToRedBall-v0",),
        name="GoToRedBall",
        description="Navigate to the red ball in a single room.",
        difficulty=0,
        max_steps=64,
        expected_optimal_steps=10,
        requires_interaction=False,
        num_objects=1,
        involves_language_composition=False,
    ),
    LevelConfig(
        gym_id="BabyAI-GoToObj-v0",
        name="GoToObj",
        description="Navigate to a specific colored object.",
        difficulty=1,
        max_steps=64,
        expected_optimal_steps=12,
        requires_interaction=False,
        num_objects=2,
        involves_language_composition=False,
    ),
    LevelConfig(
        gym_id="BabyAI-GoToLocal-v0",
        name="GoToLocal",
        description="Navigate to a specific object with distractors.",
        difficulty=2,
        max_steps=64,
        expected_optimal_steps=15,
        requires_interaction=False,
        num_objects=4,
        involves_language_composition=False,
    ),
    # Stage 1: object interaction
    LevelConfig(
        gym_id="BabyAI-PickupLoc-v0",
        name="PickupLoc",
        description="Pick up a specific object in a single room.",
        difficulty=3,
        max_steps=64,
        expected_optimal_steps=14,
        requires_interaction=True,
        num_objects=4,
        involves_language_composition=False,
    ),
    LevelConfig(
        gym_id="BabyAI-OpenDoor-v0",
        name="OpenDoor",
        description="Open a door of a specified color.",
        difficulty=3,
        max_steps=64,
        expected_optimal_steps=12,
        requires_interaction=True,
        num_objects=1,
        involves_language_composition=False,
    ),
    LevelConfig(
        gym_id="BabyAI-UnlockLocal-v0",
        name="UnlockLocal",
        description="Unlock a local door with the matching key.",
        difficulty=4,
        max_steps=128,
        expected_optimal_steps=25,
        requires_interaction=True,
        num_objects=3,
        involves_language_composition=False,
    ),
    # Stage 2: multi-room and compositional
    LevelConfig(
        gym_id="BabyAI-GoTo-v0",
        name="GoTo",
        description="Navigate to a specified object across rooms.",
        difficulty=5,
        max_steps=128,
        expected_optimal_steps=30,
        requires_interaction=True,
        num_objects=6,
        involves_language_composition=False,
    ),
    LevelConfig(
        gym_id="BabyAI-PutNextLocal-v0",
        name="PutNextLocal",
        description="Place one object next to another local object.",
        difficulty=6,
        max_steps=128,
        expected_optimal_steps=20,
        requires_interaction=True,
        num_objects=4,
        involves_language_composition=True,
    ),
    # Stage 3: hardest compositional tasks
    LevelConfig(
        gym_id="BabyAI-Synth-v0",
        name="Synth",
        description="Random compositional instructions.",
        difficulty=7,
        max_steps=256,
        expected_optimal_steps=40,
        requires_interaction=True,
        num_objects=8,
        involves_language_composition=True,
    ),
    LevelConfig(
        gym_id="BabyAI-BossLevel-v0",
        name="BossLevel",
        description="Hardest compositional BabyAI level.",
        difficulty=8,
        max_steps=512,
        expected_optimal_steps=80,
        requires_interaction=True,
        num_objects=10,
        involves_language_composition=True,
    ),
]


def get_level(name: str) -> LevelConfig:
    """Return a level by short name (case-insensitive)."""
    for level in LEVEL_REGISTRY:
        if level.name.lower() == name.lower():
            return level
    available = ", ".join(level.name for level in LEVEL_REGISTRY)
    raise ValueError(f"Unknown level '{name}'. Available levels: {available}")


def get_levels_by_difficulty(max_difficulty: int) -> list[LevelConfig]:
    """Return levels with difficulty <= max_difficulty."""
    return [level for level in LEVEL_REGISTRY if level.difficulty <= max_difficulty]


@dataclass
class CurriculumConfig:
    """Curriculum stages and advancement settings."""

    stages: list[list[str]] = field(
        default_factory=lambda: [
            ["GoToRedBall"],
            ["GoToObj", "GoToLocal"],
            ["PickupLoc", "OpenDoor", "UnlockLocal"],
            ["GoTo", "PutNextLocal"],
            ["Synth", "BossLevel"],
        ]
    )
    advance_threshold: float = 0.8
    episodes_per_eval: int = 100