afterhours-shift-manager/src/roster-api/app.py

"""HTTP API v2 handler — Bearer-authenticated roster PUT/DELETE.

PUT  /roster                 upsert name, extension, slack_user_id
DELETE /roster/{extension}   delete the row (204 even if it was already gone)

Auth is an app-level Bearer token stored in Secrets Manager. Do not log the
Authorization header, the token, or the request body.
"""

from __future__ import annotations

import base64
import hmac
import json
import logging
import os
import unicodedata
from typing import Any

import shared.sentry_init  # noqa: F401
from shared.schedule import ShiftSchedule
from shared.secrets import get_secret

logger = logging.getLogger()
logger.setLevel(logging.INFO)

PUT_FIELDS = ("name", "extension", "slack_user_id")
MAX_BODY_BYTES = 4096
MAX_NAME_LEN = 128
MAX_EXTENSION_LEN = 16
MAX_SLACK_ID_LEN = 64

_cached_token: str | None = None


class AuthError(Exception):
    """Missing or wrong Bearer token."""


class SecretUnavailable(Exception):
    """Token secret could not be read."""


def _json_response(status: int, body: dict[str, Any] | None = None) -> dict:
    if status == 204:
        return {"statusCode": 204, "headers": {}, "body": ""}
    payload = {} if body is None else body
    return {
        "statusCode": status,
        "headers": {"Content-Type": "application/json"},
        "body": json.dumps(payload, separators=(",", ":")),
    }


def _header(event: dict, name: str) -> str:
    headers = event.get("headers") or {}
    if not isinstance(headers, dict):
        return ""
    target = name.lower()
    for key, value in headers.items():
        if str(key).lower() == target:
            return "" if value is None else str(value)
    return ""


def _route(event: dict) -> tuple[str, str]:
    request_context = event.get("requestContext") or {}
    http = request_context.get("http") or {}
    method = str(http.get("method") or event.get("httpMethod") or "").upper()
    path = str(event.get("rawPath") or http.get("path") or event.get("path") or "")
    route_key = event.get("routeKey")
    if isinstance(route_key, str) and " " in route_key:
        rk_method, rk_path = route_key.split(" ", 1)
        method = method or rk_method.upper()
        path = path or rk_path
    return method, path


def _raw_body(event: dict) -> bytes | None:
    body = event.get("body")
    if body is None:
        return b""
    try:
        if event.get("isBase64Encoded"):
            if isinstance(body, bytes):
                body = body.decode("ascii")
            return base64.b64decode(body, validate=True)
        if isinstance(body, bytes):
            return body
        return str(body).encode("utf-8")
    except (ValueError, UnicodeError):
        return None


def _has_disallowed_chars(value: str, *, allow_space: bool) -> bool:
    for char in value:
        if char == " " and allow_space:
            continue
        if char.isspace() or unicodedata.category(char).startswith("C"):
            return True
    return False


def _expected_token() -> str:
    global _cached_token
    if _cached_token:
        return _cached_token
    secret_id = os.environ["ROSTER_API_TOKEN_SECRET"]
    try:
        token = get_secret(secret_id)
    except Exception:
        logger.exception("roster api token secret read failed")
        raise SecretUnavailable from None
    if not isinstance(token, str):
        raise SecretUnavailable
    token = token.strip()
    if not token:
        raise SecretUnavailable
    _cached_token = token
    return token


def _authorize(event: dict) -> None:
    presented = _header(event, "authorization")
    if not presented:
        raise AuthError
    parts = presented.split(None, 1)
    if len(parts) != 2 or parts[0].lower() != "bearer" or not parts[1].strip():
        raise AuthError
    token = parts[1].strip()
    expected = _expected_token()
    try:
        matched = hmac.compare_digest(token, expected)
    except (TypeError, ValueError):
        raise AuthError from None
    if not matched:
        raise AuthError


def _validate_put(raw: bytes) -> tuple[str, str, str]:
    if len(raw) > MAX_BODY_BYTES:
        raise ValueError("oversized")
    try:
        parsed = json.loads(raw.decode("utf-8"))
    except (UnicodeDecodeError, json.JSONDecodeError):
        raise ValueError("invalid json") from None
    if not isinstance(parsed, dict):
        raise TypeError("invalid json")
    if set(parsed) != set(PUT_FIELDS):
        raise ValueError("fields")
    values: dict[str, str] = {}
    for field in PUT_FIELDS:
        value = parsed[field]
        if not isinstance(value, str):
            raise TypeError("fields")
        trimmed = value.strip()
        if not trimmed:
            raise ValueError("fields")
        values[field] = trimmed

    name = values["name"]
    extension = values["extension"]
    slack_user_id = values["slack_user_id"]

    if len(name) > MAX_NAME_LEN or _has_disallowed_chars(name, allow_space=True):
        raise ValueError("fields")
    if (
        len(extension) > MAX_EXTENSION_LEN
        or not extension.isdigit()
        or _has_disallowed_chars(extension, allow_space=False)
    ):
        raise ValueError("fields")
    if (
        len(slack_user_id) > MAX_SLACK_ID_LEN
        or not slack_user_id.isalnum()
        or _has_disallowed_chars(slack_user_id, allow_space=False)
    ):
        raise ValueError("fields")
    return name, extension, slack_user_id


def _delete_extension(event: dict) -> str:
    params = event.get("pathParameters") or {}
    if not isinstance(params, dict):
        raise TypeError("extension")
    raw = params.get("extension")
    if not isinstance(raw, str):
        raise TypeError("extension")
    extension = raw.strip()
    if (
        not extension
        or len(extension) > MAX_EXTENSION_LEN
        or not extension.isdigit()
        or _has_disallowed_chars(extension, allow_space=False)
    ):
        raise ValueError("extension")
    return extension


def handler(event, context):
    try:
        method, path = _route(event)
        logger.info("roster api %s %s", method, path)
        try:
            _authorize(event)
        except AuthError:
            return _json_response(401, {"error": "unauthorized"})
        except SecretUnavailable:
            return _json_response(503, {"error": "service unavailable"})

        if method == "PUT" and (path == "/roster" or path.rstrip("/") == "/roster"):
            raw = _raw_body(event)
            if raw is None:
                return _json_response(400, {"error": "invalid request"})
            try:
                name, extension, slack_user_id = _validate_put(raw)
            except (TypeError, ValueError):
                return _json_response(400, {"error": "invalid request"})
            ShiftSchedule().upsert_roster_entry(extension, name, slack_user_id)
            logger.info("roster upserted extension=%s", extension)
            return _json_response(200, {"ok": True})

        if method == "DELETE" and path.startswith("/roster/"):
            try:
                extension = _delete_extension(event)
            except (TypeError, ValueError):
                return _json_response(400, {"error": "invalid request"})
            ShiftSchedule().remove_roster_entry(extension)
            logger.info("roster deleted extension=%s", extension)
            return _json_response(204)

        return _json_response(405, {"error": "method not allowed"})
    except Exception:
        logger.exception("roster api unexpected failure")
        return _json_response(500, {"error": "internal error"})