from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
from typing import Any
import json

try:
    import yaml
except Exception:  # pragma: no cover
    yaml = None


@dataclass(frozen=True)
class ModelEntry:
    model_id: str
    license: str
    usage_notes: str
    runtime: str = 'heuristic'
    backend: str | None = None
    local_fallback: str | None = None


def _load_raw(path: Path) -> Any:
    text = path.read_text(encoding='utf-8')
    if path.suffix.lower() == '.json':
        return json.loads(text)
    if yaml is not None:
        return yaml.safe_load(text)
    return json.loads(text)


def load_model_registry(path: str | Path) -> dict[str, Any]:
    path = Path(path)
    raw = _load_raw(path)
    if not isinstance(raw, dict):
        raise ValueError(f'model registry must be a mapping, got {type(raw)!r}')
    return raw


def get_entry(registry: dict[str, Any], project_key: str, component: str) -> ModelEntry:
    section = registry.get(project_key, {})
    if project_key == 'shared':
        section = registry.get('shared', {})
    else:
        section = registry.get('projects', {}).get(project_key, {})
    if component not in section:
        raise KeyError(f'missing registry entry for {project_key}.{component}')
    item = section[component]
    return ModelEntry(
        model_id=item['model_id'],
        license=item['license'],
        usage_notes=item['usage_notes'],
        runtime=item.get('runtime', 'heuristic'),
        backend=item.get('backend'),
        local_fallback=item.get('local_fallback'),
    )