"""Offline-safe, ID-correlated provider batch execution."""

from dataclasses import dataclass, field

from .provider import ProviderTransportError


@dataclass
class BatchRunResult:
    results_by_work_item_id: dict[str, dict] = field(default_factory=dict)
    errors: dict[str, str] = field(default_factory=dict)
    provider_calls: int = 0
    retries: int = 0
    usage: dict = field(default_factory=dict)


def run_batches(items, provider, batch_size: int, max_retries: int = 2, *, scenario: str | None = None) -> BatchRunResult:
    if batch_size <= 0:
        raise ValueError("batch_size must be positive")
    if max_retries < 0:
        raise ValueError("max_retries must not be negative")

    result = BatchRunResult()
    for start in range(0, len(items), batch_size):
        batch = list(items[start:start + batch_size])
        expected_ids = [str(item.work_item_id) for item in batch]
        answers = None
        for attempt in range(max_retries + 1):
            result.provider_calls += 1
            try:
                kwargs = {} if scenario is None else {"scenario": scenario}
                answers = provider.select_batch(batch, **kwargs)
                break
            except ProviderTransportError as error:
                if attempt == max_retries:
                    for work_item_id in expected_ids:
                        result.errors[work_item_id] = str(error)
                else:
                    result.retries += 1
            except Exception as error:
                for work_item_id in expected_ids:
                    result.errors[work_item_id] = str(error)
                break
        if answers is None:
            continue
        answer_ids = [str(answer.get("work_item_id")) for answer in answers]
        if len(answer_ids) != len(expected_ids) or set(answer_ids) != set(expected_ids) or len(set(answer_ids)) != len(answer_ids):
            error = "provider response did not contain exactly one answer per work_item_id"
            for work_item_id in expected_ids:
                result.errors[work_item_id] = error
            continue
        result.results_by_work_item_id.update({str(answer["work_item_id"]): answer for answer in answers})

    result.usage = dict(getattr(provider, "usage", {}) or {})
    return result