Eric Rakestraw
cfe6748330
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111 lines
5.3 KiB
Markdown
111 lines
5.3 KiB
Markdown
# Implement Source-Balanced Current Conditions Condition Codes
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## Summary
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Implement the target behavior in `docs/roadmap/current.md`: keep `/conditions/current` response shape unchanged, continue aggregating numeric observations over the current window, and replace SQL `MAX(condition_code)` with Go-based source-balanced WMO family consensus.
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This is a behavior change only. Do not add public fields, change query parameters, alter weatherfeeder tables, or add provider-specific blacklists.
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## Stage 1: Add Condition-Code Consensus Helpers
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Add package-local helpers in `internal/adapters/outbound/postgres` for current-conditions condition-code selection.
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Required data shape:
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- define a small candidate row/type containing `event_source` and `condition_code`;
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- the selector accepts latest-per-source candidates and returns `model.WMOCode`.
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Required selector behavior:
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- use the family mapping and tie ranking from `docs/roadmap/current.md` exactly;
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- ignore unrecognized WMO codes for family voting;
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- return `model.WMOUnknown` when no recognized candidates exist;
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- count each source at most once;
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- return `model.WMOUnknown` on tied family votes;
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- inside the winning family, choose the most frequent exact code;
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- when exact codes tie inside the winning family, choose by family ranking.
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Add focused unit tests for the selector before wiring SQL changes.
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## Stage 2: Split Current-Conditions Condition-Code Querying
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Update the Postgres current-conditions read path so condition-code selection is no longer computed with `MAX(condition_code)`.
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Required SQL behavior:
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- keep the existing aggregate query for sample count, numeric averages, circular wind direction, and latest `is_day`;
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- remove `MAX(condition_code)` from the aggregate query result;
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- add a separate query that returns one latest condition-code candidate per `event_source` inside the same observation window;
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- latest per source is ordered by `observed_at DESC, event_emitted_at DESC`;
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- candidate columns should include `event_source` and `condition_code`; timestamp columns may remain SQL-only if used only for ordering.
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Required repository flow:
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1. query aggregate current conditions;
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2. return `nil, nil` when the aggregate sample count maps to no data, preserving current behavior;
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3. query condition-code candidates using the same observation window;
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4. run the Go selector;
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5. map numeric aggregate fields plus selected condition code into `app.CurrentConditions`.
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Keep row DTOs and mappers local to the Postgres adapter. Do not move SQL or row types into `internal/app`.
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## Stage 3: Preserve API And Presentation Behavior
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Keep all existing `/conditions/current` API behavior except condition-code selection.
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Required invariants:
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- `conditionCode` remains present in JSON/XML/text responses through the existing presenter path;
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- `conditionText` continues to derive from selected `conditionCode` and `isDay`;
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- `format`, `units`, and `precision` behavior is unchanged;
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- no `tz` support is added;
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- no public response fields are added or removed.
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Update existing endpoint or presenter tests only if expected condition codes need to change because of the new selector.
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## Stage 4: Update Current-Behavior Documentation
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After implementation is complete, update current-behavior docs outside roadmap:
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- `docs/api.md`: current conditions aggregate numeric fields and choose `conditionCode` by source-balanced WMO family consensus;
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- `docs/internal/postgres-repository.md`: current conditions use an aggregate row plus a latest-per-source condition-code candidate query;
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- `docs/integrations/weatherfeeder-postgres.md`: current conditions use `observations.event_source` for source-balanced condition-code selection.
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Do not document any unimplemented options such as provider blacklists, trust weights, or source priorities.
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## Test Plan
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Selector tests:
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- `0`, `1`, `2` returns `0` by clear/cloud ranking;
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- `1`, `2`, `95` returns `1` because clear/cloud family wins;
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- `0`, `95` returns `model.WMOUnknown` because families tie;
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- `61`, `63`, `80` returns `61` by rain ranking;
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- `61`, `95`, `0` returns `model.WMOUnknown` because three families tie;
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- only `95` returns `95`;
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- unrecognized-only candidates return `model.WMOUnknown`;
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- duplicate candidates from the same source do not produce multiple votes if the selector receives them.
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Repository tests:
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- current conditions no longer chooses the highest numeric condition code;
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- latest condition-code candidate per source uses `observed_at DESC, event_emitted_at DESC`;
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- aggregate no-sample behavior still returns nil;
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- numeric aggregate fields, wind direction, and `isDay` mapping remain unchanged;
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- SQL/query errors from the candidate query include operation context.
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Verification commands:
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```sh
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go test ./internal/adapters/outbound/postgres ./internal/app
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go test ./internal/adapters/inbound/httpapi ./internal/adapters/inbound/httpapi/presenter
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go test ./...
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```
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## Assumptions
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- `observations.event_source` is non-null in the weatherfeeder-owned schema and is safe to use as the source identity.
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- The latest-per-source query can be implemented with existing Postgres features and does not require a migration.
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- Current conditions remain repository-owned because they are a Postgres aggregate read model; no new app service method or public interface is needed.
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- The implementation should remain standard-library and SQL based; do not add dependencies.
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