152 lines
5.0 KiB
Markdown
152 lines
5.0 KiB
Markdown
# HTTP Adapter
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This document describes the internal HTTP adapter under
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`internal/adapters/inbound/httpapi`. The public endpoint contract belongs in
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[`docs/api.md`](../api.md).
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## Purpose
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The HTTP adapter turns feedapi route definitions into calls on the application
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service boundary. It owns route registration, query binding, request validation,
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forecast day-slice filtering, response envelopes, and template names.
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## Inputs and Outputs
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Inputs:
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- feedapi HTTP requests;
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- query parameters;
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- an implementation of the adapter-local `Service` interface.
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Outputs:
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- `endpoint.Definition` values registered by runtime composition;
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- `response.Envelope{Data: ...}` values for successful requests;
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- typed feedapi errors for invalid query parameters;
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- endpoint-specific template names for text rendering.
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## Boundaries
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The adapter may:
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- define routes and supported response formats;
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- bind and validate query parameters;
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- call the `Service` interface;
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- choose the presenter function for an endpoint;
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- filter forecast copies for `/today` and `/tomorrow`.
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The adapter must not:
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- execute SQL;
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- open databases;
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- mutate repository-returned models in place;
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- duplicate public API reference text;
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- move unit conversion or timezone presentation out of presenters.
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## Config Fields Used
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The HTTP adapter does not read config directly. Feedapi applies server and
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renderer configuration before requests reach these handlers. Template names are
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declared in endpoint definitions, but `templates.base_dir` is loaded by feedapi.
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## External Adapters Used
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- `feedapi/endpoint` for route definitions.
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- `feedapi/render` for declared output formats.
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- `feedapi/response` for success envelopes.
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- `feedapi/bind` and `feedapi/errors` for query validation failures.
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- `presenter` package for payload shaping.
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## State
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The adapter has no durable state. `forecastNow` is package-level state only to
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make forecast day filtering testable. Do not add request caches or cross-request
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mutable state here.
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## Route Registry
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`Definitions(svc)` returns all implemented route definitions. It includes:
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- observations;
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- active alerts;
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- current conditions;
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- weather stories;
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- forecast discussions;
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- hourly and narrative forecasts.
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Each route uses `endpoint.GET`, declares JSON/XML/text production, and names a
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text template. Feedapi owns routing, format negotiation, response rendering,
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middleware, and error normalization after definitions are registered.
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## Query Binding
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There are three binder shapes:
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- `bindQuery`: `format` and `units`;
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- `bindPrecisionQuery`: `format`, `units`, and `precision`;
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- `bindForecastPrecisionQuery`: `format`, `units`, `precision`, and timezone;
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- `bindTimezoneQuery`: `format`, `units`, and timezone.
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All binders use feedapi binding helpers with `RejectUnknown: true`. Supported
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common query values are lowercased and trimmed before binding where applicable.
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`precision` defaults to `0` and must be between `0` and `2`. Timezone parsing is
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available only through binders used by forecast, discussion, and weather story
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routes.
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## Timezone Parsing
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Timezone parsing accepts:
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- IANA names through `time.LoadLocation`;
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- configured aliases such as `Chicago` and `Stl`;
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- common US abbreviations handled as fixed zones;
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- signed UTC offsets.
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If both `tz` and `TZ` are provided, they must match case-insensitively.
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Invalid timezone input is converted to a feedapi invalid-parameter error.
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## Forecast Day Slices
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Forecast base routes return the latest run unchanged except for presentation.
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`/today` and `/tomorrow` routes call `filterForecastRunByDaySlice`.
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Filtering behavior:
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- nil runs remain nil;
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- missing timezone means UTC;
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- day selection is based on `forecastNow()` in the resolved timezone;
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- periods are included when `period.StartTime` falls on the target local date;
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- the run is shallow-copied and `Periods` is replaced with the filtered slice.
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The package variable `forecastNow` exists so endpoint tests can make day-slice
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behavior deterministic.
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## Failure Behavior
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Binder failures become feedapi invalid-parameter responses. Handler service
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errors are returned unchanged to feedapi for runtime normalization. Nil service
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payloads are presented as nil data, so response rendering can produce
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`data: null`.
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## Templates
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Endpoint definitions bind template names only. Template loading and rendering
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belong to feedapi. Template files live under `templates/` and are operator
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configuration through `templates.base_dir`.
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## Tests to Inspect Before Changing
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- `internal/adapters/inbound/httpapi/endpoints_test.go`
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- `internal/adapters/inbound/httpapi/presenter/payload_test.go` when changing
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presenter interaction
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- `docs/api.md` when query behavior, route behavior, or payload behavior changes
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## Invariants
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- Preserve strict unknown-query rejection.
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- Keep route-specific query policy in binder functions.
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- Keep endpoint handlers thin: bind, call service, present, envelope.
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- Keep day-slice filtering in the HTTP adapter, not in the repository.
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- Preserve top-level `data` envelopes and nil-data behavior.
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