110 lines
2.5 KiB
Markdown
110 lines
2.5 KiB
Markdown
# Reference Data Layer
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## Table of Contents
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- [Purpose](#purpose)
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- [Responsibilities](#responsibilities)
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- [Recommended Structure](#recommended-structure)
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- [Rules](#rules)
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- [Examples](#examples)
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## Purpose
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The `refdata/` layer contains app-wide reference datasets that are reused across modules.
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Reference data is data that usually comes from the backend, but is not owned by one feature module.
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Examples:
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- countries
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- languages
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- currencies
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- time zones
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- common option dictionaries
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- shared lookup datasets
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## Responsibilities
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The `refdata/` layer is responsible for:
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- fetching common reference datasets
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- exposing reusable query hooks for those datasets
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- defining cache keys for reference data
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- keeping app-wide lookup data out of feature modules
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## Recommended Structure
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For small datasets, a single file per dataset is enough:
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```plaintext
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refdata/
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├── countries.ts
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├── languages.ts
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└── currencies.ts
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```
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For larger datasets, use a folder:
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```plaintext
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refdata/
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└── countries/
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├── api.ts
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├── dto.ts
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├── mapper.ts
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├── queries.ts
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└── keys.ts
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```
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## Rules
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1. Use `refdata/` only for app-wide datasets.
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If a dataset belongs to one feature module, keep it in that module's `data/` layer.
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2. `refdata/` may use infrastructure.
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Reference data hooks can use `#infrastructure/axios` and `#infrastructure/reactQuery`.
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3. `refdata/` should not import from `view/`, `pages/`, or feature modules.
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It should remain reusable across the app.
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4. Expose hooks or small service functions.
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Consumers should not need to know backend endpoints or cache key details.
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5. Add mappers when backend DTOs differ from app-facing reference data.
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If a reference dataset performs DTO transformation, test the mapper the same way module data mappers are tested.
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## Examples
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```ts
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import { keepPreviousData, useQuery } from "@tanstack/react-query";
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import { axiosClient } from "#infrastructure/axios";
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import { createKeyBuilder } from "#infrastructure/reactQuery";
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export const countriesCacheKey = createKeyBuilder(
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"REF_DATA",
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"COUNTRIES",
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"LIST",
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);
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interface CountryData {
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code: string;
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name: string;
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}
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export const useCountries = () => {
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return useQuery({
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queryKey: countriesCacheKey.store(),
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placeholderData: keepPreviousData,
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queryFn: async () => {
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return axiosClient
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.get<Array<CountryData>>("/datasets/countries")
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.then((data) => data.data);
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},
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});
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};
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```
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