import re
from typing import Any, Callable, Dict


class FastAPI:
    def __init__(self, title: str | None = None):
        self.title = title
        self._routes = []  # List of route dicts: {method, pattern, func, param_names}

    def _add_route(self, method: str, path: str, func: Callable):
        # Convert path with {name} params into a regex pattern and capture group names
        param_names = []
        pattern = ''
        i = 0
        while i < len(path):
            if path[i] == '{':
                j = path.find('}', i)
                name = path[i+1:j]
                param_names.append(name)
                pattern += rf'(?P<{name}>[^/]+)'
                i = j + 1
            else:
                pattern += re.escape(path[i])
                i += 1
        pattern = '^' + pattern + '$'
        self._routes.append({
            'method': method,
            'path': path,
            'pattern': re.compile(pattern),
            'param_names': param_names,
            'func': func,
        })

    def post(self, path: str):
        def decorator(func: Callable):
            self._add_route('POST', path, func)
            return func
        return decorator

    def get(self, path: str):
        def decorator(func: Callable):
            self._add_route('GET', path, func)
            return func
        return decorator

    # Minimal internal dispatch used by the TestClient shim
    def _dispatch(self, method: str, path: str, body: Dict[str, Any] | None = None):
        for r in self._routes:
            if r['method'] != method:
                continue
            m = r['pattern'].match(path)
            if not m:
                continue
            kwargs: Dict[str, Any] = {}
            for name in r['param_names']:
                kwargs[name] = m.group(name)
            if body is not None:
                kwargs['payload'] = body
            result = r['func'](**kwargs)
            return SimpleResponse(result, 200)
        return SimpleResponse({'error': 'not found'}, 404)


class SimpleResponse:
    def __init__(self, json_body: Any, status_code: int = 200):
        self._json = json_body
        self.status_code = status_code
    def json(self):
        return self._json