first commit

backend/.env.example

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+MONGODB_URI=mongodb://localhost:27017
+MONGODB_DB_NAME=zero_knowledge_platform
+JWT_SECRET=replace-with-a-long-random-secret
+JWT_ALGORITHM=HS256
+ACCESS_TOKEN_EXPIRE_MINUTES=60
+CORS_ORIGINS=http://localhost:5173,http://127.0.0.1:5173

backend/app/api/auth.py

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+from fastapi import APIRouter, Depends
+from motor.motor_asyncio import AsyncIOMotorDatabase
+
+from app.core.security import create_access_token
+from app.db.mongo import get_database
+from app.schemas.auth import (
+    AuthBootstrapResponse,
+    AuthLoginBootstrapRequest,
+    AuthLoginRequest,
+    AuthSignupRequest,
+    AuthTokenResponse,
+)
+from app.services.auth import create_account, get_account_by_identifier, verify_account_login
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+@router.post("/signup", response_model=AuthTokenResponse)
+async def signup(payload: AuthSignupRequest, database: AsyncIOMotorDatabase = Depends(get_database)) -> AuthTokenResponse:
+    owner_id = await create_account(database, payload)
+    access_token = create_access_token(owner_id)
+    return AuthTokenResponse(accessToken=access_token, ownerId=owner_id)
+
+
+@router.post("/bootstrap", response_model=AuthBootstrapResponse)
+async def bootstrap(
+    payload: AuthLoginBootstrapRequest,
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> AuthBootstrapResponse:
+    account = await get_account_by_identifier(database, payload.identifierType.value, payload.identifier)
+    return AuthBootstrapResponse(
+        identifierType=payload.identifierType,
+        identifier=account["identifier"],
+        saltAuth=account["saltAuth"],
+        saltEnc=account["saltEnc"],
+    )
+
+
+@router.post("/login", response_model=AuthTokenResponse)
+async def login(payload: AuthLoginRequest, database: AsyncIOMotorDatabase = Depends(get_database)) -> AuthTokenResponse:
+    owner_id = await verify_account_login(database, payload)
+    access_token = create_access_token(owner_id)
+    return AuthTokenResponse(accessToken=access_token, ownerId=owner_id)

backend/app/api/children.py

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+from fastapi import APIRouter, Depends
+from motor.motor_asyncio import AsyncIOMotorDatabase
+
+from app.dependencies.auth import get_current_owner_id
+from app.db.mongo import get_database
+from app.schemas.records import ChildCreateRequest, ChildRecordResponse, ChildUpdateRequest
+from app.services.records import create_child, delete_child, get_child, list_children, update_child
+
+router = APIRouter(prefix="/parents/{parent_id}/children", tags=["children"])
+
+
+@router.post("", response_model=ChildRecordResponse)
+async def create_child_record(
+    parent_id: str,
+    payload: ChildCreateRequest,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ChildRecordResponse:
+    if payload.parentId != parent_id:
+        payload = ChildCreateRequest(parentId=parent_id, iv=payload.iv, ciphertext=payload.ciphertext)
+    return await create_child(database, owner_id, payload)
+
+
+@router.get("", response_model=list[ChildRecordResponse])
+async def list_child_records(
+    parent_id: str,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> list[ChildRecordResponse]:
+    return await list_children(database, owner_id, parent_id)
+
+
+@router.get("/{child_id}", response_model=ChildRecordResponse)
+async def get_child_record(
+    parent_id: str,
+    child_id: str,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ChildRecordResponse:
+    return await get_child(database, owner_id, parent_id, child_id)
+
+
+@router.put("/{child_id}", response_model=ChildRecordResponse)
+async def update_child_record(
+    parent_id: str,
+    child_id: str,
+    payload: ChildUpdateRequest,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ChildRecordResponse:
+    return await update_child(database, owner_id, parent_id, child_id, payload)
+
+
+@router.delete("/{child_id}", status_code=204)
+async def delete_child_record(
+    parent_id: str,
+    child_id: str,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> None:
+    await delete_child(database, owner_id, parent_id, child_id)

backend/app/api/health.py

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+from fastapi import APIRouter
+
+router = APIRouter(prefix="/health", tags=["health"])
+
+
+@router.get("")
+async def health_check() -> dict[str, str]:
+    return {"status": "ok"}

backend/app/api/parents.py

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+from fastapi import APIRouter, Depends
+from motor.motor_asyncio import AsyncIOMotorDatabase
+
+from app.dependencies.auth import get_current_owner_id
+from app.db.mongo import get_database
+from app.schemas.records import ParentCreateRequest, ParentRecordResponse, ParentUpdateRequest
+from app.services.records import create_parent, delete_parent, get_parent, list_parents, update_parent
+
+router = APIRouter(prefix="/parents", tags=["parents"])
+
+
+@router.post("", response_model=ParentRecordResponse)
+async def create_parent_record(
+    payload: ParentCreateRequest,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ParentRecordResponse:
+    return await create_parent(database, owner_id, payload)
+
+
+@router.get("", response_model=list[ParentRecordResponse])
+async def list_parent_records(
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> list[ParentRecordResponse]:
+    return await list_parents(database, owner_id)
+
+
+@router.get("/{parent_id}", response_model=ParentRecordResponse)
+async def get_parent_record(
+    parent_id: str,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ParentRecordResponse:
+    return await get_parent(database, owner_id, parent_id)
+
+
+@router.put("/{parent_id}", response_model=ParentRecordResponse)
+async def update_parent_record(
+    parent_id: str,
+    payload: ParentUpdateRequest,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> ParentRecordResponse:
+    return await update_parent(database, owner_id, parent_id, payload)
+
+
+@router.delete("/{parent_id}", status_code=204)
+async def delete_parent_record(
+    parent_id: str,
+    owner_id: str = Depends(get_current_owner_id),
+    database: AsyncIOMotorDatabase = Depends(get_database),
+) -> None:
+    await delete_parent(database, owner_id, parent_id)

backend/app/core/config.py

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+from dataclasses import dataclass, field
+import os
+from pathlib import Path
+
+from dotenv import load_dotenv
+
+backend_env_path = Path(__file__).resolve().parents[2] / ".env"
+load_dotenv(dotenv_path=backend_env_path)
+
+
+@dataclass(frozen=True)
+class Settings:
+    app_name: str = os.getenv("APP_NAME", "Zero Knowledge Platform API")
+    mongo_uri: str = os.getenv("MONGODB_URI", "mongodb://localhost:27017")
+    mongo_db_name: str = os.getenv("MONGODB_DB_NAME", "zero_knowledge_platform")
+    jwt_secret: str = os.getenv("JWT_SECRET", "replace-with-a-long-random-secret")
+    jwt_algorithm: str = os.getenv("JWT_ALGORITHM", "HS256")
+    access_token_expire_minutes: int = int(os.getenv("ACCESS_TOKEN_EXPIRE_MINUTES", "60"))
+    cors_origins: list[str] = field(
+        default_factory=lambda: [
+            origin.strip()
+            for origin in os.getenv(
+                "CORS_ORIGINS",
+                "http://localhost:5173,http://127.0.0.1:5173",
+            ).split(",")
+            if origin.strip()
+        ]
+    )
+
+
+settings = Settings()

backend/app/core/security.py

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+import re
+from datetime import datetime, timedelta, timezone
+from typing import Any
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def normalize_identifier(identifier_type: str, identifier: str) -> str:
+    value = identifier.strip()
+    if identifier_type == "email":
+        return value.lower()
+    if identifier_type == "username":
+        return value
+    if identifier_type == "mobile":
+        return re.sub(r"[\s\-().]", "", value)
+    return value
+
+
+def hash_auth_key(auth_key_material: str) -> str:
+    return pwd_context.hash(auth_key_material)
+
+
+def verify_auth_key(auth_key_material: str, hashed_auth_key: str) -> bool:
+    return pwd_context.verify(auth_key_material, hashed_auth_key)
+
+
+def create_access_token(subject: str, extra_claims: dict[str, Any] | None = None) -> str:
+    expires_at = datetime.now(timezone.utc) + timedelta(minutes=settings.access_token_expire_minutes)
+    payload: dict[str, Any] = {"sub": subject, "exp": expires_at, "iat": datetime.now(timezone.utc)}
+    if extra_claims:
+        payload.update(extra_claims)
+    return jwt.encode(payload, settings.jwt_secret, algorithm=settings.jwt_algorithm)

backend/app/db/mongo.py

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+from motor.motor_asyncio import AsyncIOMotorClient, AsyncIOMotorDatabase
+
+from app.core.config import settings
+
+client: AsyncIOMotorClient | None = None
+
+
+def get_database() -> AsyncIOMotorDatabase:
+    if client is None:
+        raise RuntimeError("MongoDB client has not been initialized")
+    return client[settings.mongo_db_name]
+
+
+def get_client() -> AsyncIOMotorClient:
+    if client is None:
+        raise RuntimeError("MongoDB client has not been initialized")
+    return client
+
+
+async def connect_to_mongo() -> None:
+    global client
+    client = AsyncIOMotorClient(settings.mongo_uri)
+
+
+async def close_mongo_connection() -> None:
+    global client
+    if client is not None:
+        client.close()
+        client = None

backend/app/dependencies/auth.py

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+from fastapi import Depends, HTTPException, status
+from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
+from jose import JWTError, jwt
+
+from app.core.config import settings
+
+bearer_scheme = HTTPBearer(auto_error=False)
+
+
+async def get_current_owner_id(
+    credentials: HTTPAuthorizationCredentials | None = Depends(bearer_scheme),
+) -> str:
+    if credentials is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Not authenticated.",
+        )
+
+    try:
+        payload = jwt.decode(credentials.credentials, settings.jwt_secret, algorithms=[settings.jwt_algorithm])
+    except JWTError as exc:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid or expired token.",
+        ) from exc
+
+    owner_id = payload.get("sub")
+    if not isinstance(owner_id, str) or not owner_id:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid token payload.",
+        )
+    return owner_id

backend/app/main.py

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+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from fastapi import Request
+from fastapi.responses import JSONResponse
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.auth import router as auth_router
+from app.api.children import router as children_router
+from app.api.parents import router as parents_router
+from app.api.health import router as health_router
+from app.core.config import settings
+from app.db.mongo import close_mongo_connection, connect_to_mongo, get_database
+from app.services.records import ensure_record_indexes
+from app.services.auth import ensure_auth_indexes
+
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    await connect_to_mongo()
+    await ensure_auth_indexes(get_database())
+    await ensure_record_indexes(get_database())
+    yield
+    await close_mongo_connection()
+
+
+app = FastAPI(title="Zero Knowledge Platform API", lifespan=lifespan)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=settings.cors_origins,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+app.include_router(health_router)
+app.include_router(auth_router)
+app.include_router(parents_router)
+app.include_router(children_router)
+
+
+@app.exception_handler(Exception)
+async def unhandled_exception_handler(request: Request, exc: Exception) -> JSONResponse:
+    return JSONResponse(status_code=500, content={"detail": "Internal server error."})
+
+
+@app.get("/")
+async def root() -> dict[str, str]:
+    return {"message": "Zero Knowledge Platform API"}

backend/app/schemas/auth.py

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+from enum import Enum
+
+from pydantic import BaseModel, Field, field_validator
+
+
+class IdentifierType(str, Enum):
+    email = "email"
+    username = "username"
+    mobile = "mobile"
+
+
+class AuthIdentifierBase(BaseModel):
+    identifierType: IdentifierType
+    identifier: str = Field(min_length=1, max_length=255)
+
+    @field_validator("identifier")
+    @classmethod
+    def strip_identifier(cls, value: str) -> str:
+        normalized = value.strip()
+        if not normalized:
+            raise ValueError("identifier cannot be empty")
+        return normalized
+
+
+class AuthSignupRequest(AuthIdentifierBase):
+    saltAuth: str = Field(min_length=8)
+    saltEnc: str = Field(min_length=8)
+    authKeyMaterial: str = Field(min_length=8)
+
+
+class AuthLoginBootstrapRequest(AuthIdentifierBase):
+    pass
+
+
+class AuthLoginRequest(AuthIdentifierBase):
+    authKeyMaterial: str = Field(min_length=8)
+
+
+class AuthBootstrapResponse(BaseModel):
+    identifierType: IdentifierType
+    identifier: str
+    saltAuth: str
+    saltEnc: str
+
+
+class AuthTokenResponse(BaseModel):
+    accessToken: str
+    tokenType: str = "bearer"
+    ownerId: str

backend/app/schemas/records.py

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+from datetime import datetime
+
+from pydantic import BaseModel, Field, field_validator
+
+
+class ParentBlobBase(BaseModel):
+    iv: str = Field(min_length=1)
+    ciphertext: str = Field(min_length=1)
+
+
+class ParentCreateRequest(ParentBlobBase):
+    pass
+
+
+class ParentUpdateRequest(ParentBlobBase):
+    pass
+
+
+class ChildCreateRequest(ParentBlobBase):
+    parentId: str = Field(min_length=1)
+
+    @field_validator("parentId")
+    @classmethod
+    def strip_parent_id(cls, value: str) -> str:
+        normalized = value.strip()
+        if not normalized:
+            raise ValueError("parentId cannot be empty")
+        return normalized
+
+
+class ChildUpdateRequest(ParentBlobBase):
+    pass
+
+
+class ParentRecordResponse(ParentBlobBase):
+    id: str
+    ownerId: str
+    createdAt: datetime
+    updatedAt: datetime
+
+
+class ChildRecordResponse(ParentBlobBase):
+    id: str
+    parentId: str
+    ownerId: str
+    createdAt: datetime
+    updatedAt: datetime

backend/app/services/auth.py

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+from datetime import datetime, timezone
+
+from fastapi import HTTPException, status
+from motor.motor_asyncio import AsyncIOMotorDatabase
+from pymongo.errors import DuplicateKeyError
+
+from app.core.security import hash_auth_key, normalize_identifier, verify_auth_key
+from app.schemas.auth import AuthLoginRequest, AuthSignupRequest
+
+ACCOUNTS_COLLECTION = "accounts"
+
+
+async def ensure_auth_indexes(database: AsyncIOMotorDatabase) -> None:
+    await database[ACCOUNTS_COLLECTION].create_index(
+        [("identifierType", 1), ("identifier", 1)],
+        unique=True,
+        name="uq_accounts_identifier",
+    )
+
+
+def _account_filter(identifier_type: str, identifier: str) -> dict[str, str]:
+    return {
+        "identifierType": identifier_type,
+        "identifier": normalize_identifier(identifier_type, identifier),
+    }
+
+
+async def create_account(database: AsyncIOMotorDatabase, payload: AuthSignupRequest) -> str:
+    now = datetime.now(timezone.utc)
+    account_document = {
+        "identifierType": payload.identifierType.value,
+        "identifier": normalize_identifier(payload.identifierType.value, payload.identifier),
+        "hashedAuthKey": hash_auth_key(payload.authKeyMaterial),
+        "saltAuth": payload.saltAuth,
+        "saltEnc": payload.saltEnc,
+        "createdAt": now,
+        "updatedAt": now,
+    }
+
+    try:
+        result = await database[ACCOUNTS_COLLECTION].insert_one(account_document)
+    except DuplicateKeyError as exc:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="An account with that identifier already exists.",
+        ) from exc
+
+    return str(result.inserted_id)
+
+
+async def get_account_by_identifier(database: AsyncIOMotorDatabase, identifier_type: str, identifier: str) -> dict[str, str]:
+    account = await database[ACCOUNTS_COLLECTION].find_one(_account_filter(identifier_type, identifier))
+    if account is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Account not found.",
+        )
+    return account
+
+
+async def verify_account_login(database: AsyncIOMotorDatabase, payload: AuthLoginRequest) -> str:
+    account = await get_account_by_identifier(database, payload.identifierType.value, payload.identifier)
+    if not verify_auth_key(payload.authKeyMaterial, account["hashedAuthKey"]):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid credentials.",
+        )
+    return str(account["_id"])

backend/app/services/records.py

@@ -0,0 +1,235 @@
+from datetime import datetime, timezone
+
+from bson import ObjectId
+from fastapi import HTTPException, status
+from motor.motor_asyncio import AsyncIOMotorDatabase
+from pymongo import ReturnDocument
+from pymongo.errors import DuplicateKeyError
+
+from app.schemas.records import (
+    ChildCreateRequest,
+    ChildRecordResponse,
+    ChildUpdateRequest,
+    ParentCreateRequest,
+    ParentRecordResponse,
+    ParentUpdateRequest,
+)
+
+PARENTS_COLLECTION = "parents"
+CHILDREN_COLLECTION = "children"
+
+
+class RecordNotFoundError(HTTPException):
+    def __init__(self, detail: str = "Record not found.") -> None:
+        super().__init__(status_code=status.HTTP_404_NOT_FOUND, detail=detail)
+
+
+class BadRequestError(HTTPException):
+    def __init__(self, detail: str = "Invalid request.") -> None:
+        super().__init__(status_code=status.HTTP_400_BAD_REQUEST, detail=detail)
+
+
+def _now() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+def _to_object_id(value: str, field_name: str) -> ObjectId:
+    if not ObjectId.is_valid(value):
+        raise BadRequestError(f"Invalid {field_name}.")
+    return ObjectId(value)
+
+
+def _serialize_parent(document: dict) -> ParentRecordResponse:
+    return ParentRecordResponse(
+        id=str(document["_id"]),
+        ownerId=document["ownerId"],
+        iv=document["iv"],
+        ciphertext=document["ciphertext"],
+        createdAt=document["createdAt"],
+        updatedAt=document["updatedAt"],
+    )
+
+
+def _serialize_child(document: dict) -> ChildRecordResponse:
+    return ChildRecordResponse(
+        id=str(document["_id"]),
+        parentId=str(document["parentId"]),
+        ownerId=document["ownerId"],
+        iv=document["iv"],
+        ciphertext=document["ciphertext"],
+        createdAt=document["createdAt"],
+        updatedAt=document["updatedAt"],
+    )
+
+
+async def ensure_record_indexes(database: AsyncIOMotorDatabase) -> None:
+    await database[PARENTS_COLLECTION].create_index([("ownerId", 1)], name="ix_parents_ownerId")
+    await database[CHILDREN_COLLECTION].create_index([("ownerId", 1)], name="ix_children_ownerId")
+    await database[CHILDREN_COLLECTION].create_index([("parentId", 1)], name="ix_children_parentId")
+    await database[CHILDREN_COLLECTION].create_index(
+        [("ownerId", 1), ("parentId", 1)],
+        name="ix_children_ownerId_parentId",
+    )
+
+
+async def create_parent(database: AsyncIOMotorDatabase, owner_id: str, payload: ParentCreateRequest) -> ParentRecordResponse:
+    now = _now()
+    document = {
+        "ownerId": owner_id,
+        "iv": payload.iv,
+        "ciphertext": payload.ciphertext,
+        "createdAt": now,
+        "updatedAt": now,
+    }
+    result = await database[PARENTS_COLLECTION].insert_one(document)
+    document["_id"] = result.inserted_id
+    return _serialize_parent(document)
+
+
+async def list_parents(database: AsyncIOMotorDatabase, owner_id: str) -> list[ParentRecordResponse]:
+    parents: list[ParentRecordResponse] = []
+    cursor = database[PARENTS_COLLECTION].find({"ownerId": owner_id}).sort("createdAt", -1)
+    async for document in cursor:
+        parents.append(_serialize_parent(document))
+    return parents
+
+
+async def get_parent(database: AsyncIOMotorDatabase, owner_id: str, parent_id: str) -> ParentRecordResponse:
+    document = await database[PARENTS_COLLECTION].find_one(
+        {"_id": _to_object_id(parent_id, "parentId"), "ownerId": owner_id}
+    )
+    if document is None:
+        raise RecordNotFoundError("Parent record not found.")
+    return _serialize_parent(document)
+
+
+async def update_parent(
+    database: AsyncIOMotorDatabase,
+    owner_id: str,
+    parent_id: str,
+    payload: ParentUpdateRequest,
+) -> ParentRecordResponse:
+    document = await database[PARENTS_COLLECTION].find_one_and_update(
+        {"_id": _to_object_id(parent_id, "parentId"), "ownerId": owner_id},
+        {
+            "$set": {
+                "iv": payload.iv,
+                "ciphertext": payload.ciphertext,
+                "updatedAt": _now(),
+            }
+        },
+        return_document=ReturnDocument.AFTER,
+    )
+    if document is None:
+        raise RecordNotFoundError("Parent record not found.")
+    return _serialize_parent(document)
+
+
+async def delete_parent(database: AsyncIOMotorDatabase, owner_id: str, parent_id: str) -> None:
+    client = database.client
+    if client is None:
+        raise RuntimeError("MongoDB client has not been initialized")
+
+    parent_object_id = _to_object_id(parent_id, "parentId")
+    async with await client.start_session() as session:
+        async with session.start_transaction():
+            parent = await database[PARENTS_COLLECTION].find_one(
+                {"_id": parent_object_id, "ownerId": owner_id},
+                session=session,
+            )
+            if parent is None:
+                raise RecordNotFoundError("Parent record not found.")
+
+            await database[CHILDREN_COLLECTION].delete_many(
+                {"parentId": parent_object_id, "ownerId": owner_id},
+                session=session,
+            )
+            await database[PARENTS_COLLECTION].delete_one(
+                {"_id": parent_object_id, "ownerId": owner_id},
+                session=session,
+            )
+
+
+async def create_child(
+    database: AsyncIOMotorDatabase,
+    owner_id: str,
+    payload: ChildCreateRequest,
+) -> ChildRecordResponse:
+    parent_object_id = _to_object_id(payload.parentId, "parentId")
+    parent = await database[PARENTS_COLLECTION].find_one({"_id": parent_object_id, "ownerId": owner_id})
+    if parent is None:
+        raise RecordNotFoundError("Parent record not found.")
+
+    now = _now()
+    document = {
+        "ownerId": owner_id,
+        "parentId": parent_object_id,
+        "iv": payload.iv,
+        "ciphertext": payload.ciphertext,
+        "createdAt": now,
+        "updatedAt": now,
+    }
+    result = await database[CHILDREN_COLLECTION].insert_one(document)
+    document["_id"] = result.inserted_id
+    return _serialize_child(document)
+
+
+async def list_children(database: AsyncIOMotorDatabase, owner_id: str, parent_id: str) -> list[ChildRecordResponse]:
+    parent_object_id = _to_object_id(parent_id, "parentId")
+    children: list[ChildRecordResponse] = []
+    cursor = database[CHILDREN_COLLECTION].find({"ownerId": owner_id, "parentId": parent_object_id}).sort("createdAt", -1)
+    async for document in cursor:
+        children.append(_serialize_child(document))
+    return children
+
+
+async def get_child(database: AsyncIOMotorDatabase, owner_id: str, parent_id: str, child_id: str) -> ChildRecordResponse:
+    document = await database[CHILDREN_COLLECTION].find_one(
+        {
+            "_id": _to_object_id(child_id, "childId"),
+            "parentId": _to_object_id(parent_id, "parentId"),
+            "ownerId": owner_id,
+        }
+    )
+    if document is None:
+        raise RecordNotFoundError("Child record not found.")
+    return _serialize_child(document)
+
+
+async def update_child(
+    database: AsyncIOMotorDatabase,
+    owner_id: str,
+    parent_id: str,
+    child_id: str,
+    payload: ChildUpdateRequest,
+) -> ChildRecordResponse:
+    document = await database[CHILDREN_COLLECTION].find_one_and_update(
+        {
+            "_id": _to_object_id(child_id, "childId"),
+            "parentId": _to_object_id(parent_id, "parentId"),
+            "ownerId": owner_id,
+        },
+        {
+            "$set": {
+                "iv": payload.iv,
+                "ciphertext": payload.ciphertext,
+                "updatedAt": _now(),
+            }
+        },
+        return_document=ReturnDocument.AFTER,
+    )
+    if document is None:
+        raise RecordNotFoundError("Child record not found.")
+    return _serialize_child(document)
+
+
+async def delete_child(database: AsyncIOMotorDatabase, owner_id: str, parent_id: str, child_id: str) -> None:
+    result = await database[CHILDREN_COLLECTION].delete_one(
+        {
+            "_id": _to_object_id(child_id, "childId"),
+            "parentId": _to_object_id(parent_id, "parentId"),
+            "ownerId": owner_id,
+        }
+    )
+    if result.deleted_count == 0:
+        raise RecordNotFoundError("Child record not found.")

backend/requirements.txt

@@ -0,0 +1,7 @@
+fastapi>=0.115,<1
+uvicorn[standard]>=0.30,<1
+motor>=3.6,<4
+pydantic>=2.8,<3
+python-jose[cryptography]>=3.3,<4
+passlib[bcrypt]>=1.7,<2
+python-dotenv>=1.0,<2