from __future__ import annotations

from pathlib import Path
from typing import Any, Literal

import yaml
from pydantic import BaseModel, Field, field_validator, model_validator


class RewardConfig(BaseModel):
    quality_weight: float = 1.0
    cost_weight: float = 0.0
    latency_weight: float = 0.0
    cost_scale_usd: float = 0.01
    latency_scale_seconds: float = 30.0
    judge_model: str | None = None
    judge_system_prompt: str = (
        "Score the candidate answer from 0 to 1. Return only one decimal number."
    )

    @field_validator("cost_scale_usd", "latency_scale_seconds")
    @classmethod
    def positive_scales(cls, value: float) -> float:
        if value <= 0:
            raise ValueError("reward scales must be positive")
        return value


class WorkerConfig(BaseModel):
    id: str
    provider: Literal["openrouter", "openai_compatible", "mock"] = "openrouter"
    model: str
    description: str = ""
    base_url: str | None = None
    api_key_env: str | None = None
    api_key: str | None = Field(default=None, repr=False)
    system_prompt: str = "You are a helpful expert. Follow the user's requested output format."
    temperature: float = 0.1
    max_tokens: int = 1024
    extra_body: dict[str, Any] = Field(default_factory=dict)
    mock_domains: list[str] = Field(default_factory=list)
    mock_specialist_accuracy: float = 1.0
    mock_general_accuracy: float = 0.0


class WorkerPoolConfig(BaseModel):
    project_name: str = "benchgen-fugu-lite"
    base_url: str = "https://openrouter.ai/api/v1"
    api_key_env: str = "OPENROUTER_API_KEY"
    concurrency: int = 4
    timeout_seconds: float = 120.0
    max_retries: int = 3
    workers: list[WorkerConfig]
    reward: RewardConfig = Field(default_factory=RewardConfig)

    @model_validator(mode="after")
    def unique_workers(self) -> WorkerPoolConfig:
        ids = [worker.id for worker in self.workers]
        if not ids:
            raise ValueError("at least one worker is required")
        if len(ids) != len(set(ids)):
            raise ValueError("worker IDs must be unique")
        return self

    @property
    def worker_ids(self) -> list[str]:
        return [worker.id for worker in self.workers]

    @property
    def worker_descriptions(self) -> dict[str, str]:
        return {worker.id: worker.description for worker in self.workers}


class ModelConfig(BaseModel):
    base_model: str = "Qwen/Qwen3-0.6B"
    max_length: int = 512
    pooling: Literal["last_token", "mean"] = "last_token"
    dropout: float = 0.05
    freeze_backbone: bool = True
    dtype: Literal["auto", "float32", "float16", "bfloat16"] = "auto"


class SFTTrainingConfig(BaseModel):
    seed: int = 42
    epochs: int = 5
    batch_size: int = 8
    gradient_accumulation_steps: int = 1
    learning_rate: float = 1e-3
    weight_decay: float = 0.01
    max_grad_norm: float = 1.0
    soft_target_temperature: float = 0.15
    log_every: int = 10


class RLTrainingConfig(BaseModel):
    seed: int = 43
    epochs: int = 3
    batch_size: int = 8
    gradient_accumulation_steps: int = 1
    learning_rate: float = 2e-4
    weight_decay: float = 0.0
    max_grad_norm: float = 1.0
    estimator: Literal["reinforce", "expected_reward"] = "reinforce"
    rollouts_per_prompt: int = 8
    entropy_coefficient: float = 0.01
    normalize_advantage: bool = False
    log_every: int = 10


class ESTrainingConfig(BaseModel):
    seed: int = 44
    generations: int = 30
    sigma: float = 0.03
    population_size: int | None = 16
    objective: Literal["greedy_utility", "expected_utility"] = "greedy_utility"


class SFTConfig(BaseModel):
    model: ModelConfig = Field(default_factory=ModelConfig)
    training: SFTTrainingConfig = Field(default_factory=SFTTrainingConfig)


class RLConfig(BaseModel):
    model: ModelConfig = Field(default_factory=ModelConfig)
    training: RLTrainingConfig = Field(default_factory=RLTrainingConfig)


class ESConfig(BaseModel):
    model: ModelConfig = Field(default_factory=ModelConfig)
    training: ESTrainingConfig = Field(default_factory=ESTrainingConfig)


def load_yaml(path: str | Path) -> dict[str, Any]:
    with Path(path).open("r", encoding="utf-8") as handle:
        data = yaml.safe_load(handle)
    if not isinstance(data, dict):
        raise TypeError(f"Expected a YAML object in {path}")
    return data


def load_worker_pool(path: str | Path) -> WorkerPoolConfig:
    return WorkerPoolConfig.model_validate(load_yaml(path))


def load_sft_config(path: str | Path) -> SFTConfig:
    return SFTConfig.model_validate(load_yaml(path))


def load_rl_config(path: str | Path) -> RLConfig:
    return RLConfig.model_validate(load_yaml(path))


def load_es_config(path: str | Path) -> ESConfig:
    return ESConfig.model_validate(load_yaml(path))