sources: standardize Event.ID on Source:EffectiveAt; simplify raw event helper

- Adopt an opinionated Event.ID policy across sources:
  - use upstream-provided ID when available
  - otherwise derive a stable ID from Source:EffectiveAt (RFC3339Nano, UTC)
  - fall back to Source:EmittedAt when EffectiveAt is unavailable
- Add common/id helper to centralize ID selection logic and keep sources consistent
- Simplify common event construction by collapsing SingleRawEventAt/SingleRawEvent
  into a single explicit SingleRawEvent helper (emittedAt passed in)
- Update NWS/Open-Meteo/OpenWeather observation sources to:
  - compute EffectiveAt first
  - generate IDs via the shared helper
  - build envelopes via the unified SingleRawEvent helper
- Improve determinism and dedupe-friendliness without changing schemas or payloads

internal/sources/common/event.go

@@ -9,17 +9,34 @@ import (
 
 // SingleRawEvent constructs, validates, and returns a slice containing exactly one event.
 //
-// This removes the repetitive "event envelope ceremony" from individual sources.
+// This removes repetitive "event envelope ceremony" from individual sources.
 // Sources remain responsible for:
 //   - fetching bytes (raw payload)
 //   - choosing Schema (raw schema identifier)
-//   - computing a stable Event.ID and (optional) EffectiveAt
-func SingleRawEvent(kind event.Kind, sourceName string, schema string, id string, effectiveAt *time.Time, payload any) ([]event.Event, error) {
+//   - computing Event.ID and (optional) EffectiveAt
+//
+// emittedAt is explicit so callers can compute IDs using the same timestamp (or
+// so tests can provide a stable value).
+func SingleRawEvent(
+	kind event.Kind,
+	sourceName string,
+	schema string,
+	id string,
+	emittedAt time.Time,
+	effectiveAt *time.Time,
+	payload any,
+) ([]event.Event, error) {
+	if emittedAt.IsZero() {
+		emittedAt = time.Now().UTC()
+	} else {
+		emittedAt = emittedAt.UTC()
+	}
+
 	e := event.Event{
 		ID:          id,
 		Kind:        kind,
 		Source:      sourceName,
-		EmittedAt:   time.Now().UTC(),
+		EmittedAt:   emittedAt,
 		EffectiveAt: effectiveAt,
 
 		// RAW schema (normalizer matches on this).

internal/sources/common/id.go

@@ -0,0 +1,39 @@
+// FILE: ./internal/sources/common/id.go
+package common
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+// ChooseEventID applies weatherfeeder's opinionated Event.ID policy:
+//
+//   - If upstream provides an ID, use it (trimmed).
+//   - Otherwise, ID is "<Source>:<EffectiveAt>" when available.
+//   - If EffectiveAt is unavailable, fall back to "<Source>:<EmittedAt>".
+//
+// Timestamps are encoded as RFC3339Nano in UTC.
+func ChooseEventID(upstreamID, sourceName string, effectiveAt *time.Time, emittedAt time.Time) string {
+	if id := strings.TrimSpace(upstreamID); id != "" {
+		return id
+	}
+
+	src := strings.TrimSpace(sourceName)
+	if src == "" {
+		src = "UNKNOWN_SOURCE"
+	}
+
+	// Prefer EffectiveAt for dedupe friendliness.
+	if effectiveAt != nil && !effectiveAt.IsZero() {
+		return fmt.Sprintf("%s:%s", src, effectiveAt.UTC().Format(time.RFC3339Nano))
+	}
+
+	// Fall back to EmittedAt (still stable within a poll invocation).
+	t := emittedAt.UTC()
+	if t.IsZero() {
+		t = time.Now().UTC()
+	}
+
+	return fmt.Sprintf("%s:%s", src, t.Format(time.RFC3339Nano))
+}

internal/sources/nws/observation.go

@@ -4,7 +4,6 @@ package nws
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 	"strings"
 	"time"
 
@@ -15,10 +14,6 @@ import (
 )
 
 // ObservationSource polls an NWS station observation endpoint and emits a RAW observation Event.
-//
-// This corresponds to URLs like:
-//
-//	https://api.weather.gov/stations/KSTL/observations/latest
 type ObservationSource struct {
 	http *common.HTTPSource
 }
@@ -36,35 +31,14 @@ func NewObservationSource(cfg config.SourceConfig) (*ObservationSource, error) {
 
 func (s *ObservationSource) Name() string { return s.http.Name }
 
-// Kind is used for routing/policy.
-// We keep Kind canonical (observation) even for raw events; Schema differentiates raw vs canonical.
 func (s *ObservationSource) Kind() event.Kind { return event.Kind("observation") }
 
-// Poll fetches NWS "latest observation" and emits exactly one RAW Event.
-// The RAW payload is json.RawMessage and Schema is standards.SchemaRawNWSObservationV1.
 func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 	raw, meta, err := s.fetchRaw(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	// Event.ID must be set BEFORE normalization (feedkit requires it).
-	// Prefer NWS-provided "id" (stable URL). Fallback to a stable computed key.
-	eventID := strings.TrimSpace(meta.ID)
-	if eventID == "" {
-		ts := meta.ParsedTimestamp
-		if ts.IsZero() {
-			ts = time.Now().UTC()
-		}
-
-		station := strings.TrimSpace(meta.StationID)
-		if station == "" {
-			station = "UNKNOWN"
-		}
-
-		eventID = fmt.Sprintf("nws:observation:%s:%s:%s", s.http.Name, station, ts.UTC().Format(time.RFC3339Nano))
-	}
-
 	// EffectiveAt is optional; for observations it’s naturally the observation timestamp.
 	var effectiveAt *time.Time
 	if !meta.ParsedTimestamp.IsZero() {
@@ -72,11 +46,15 @@ func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 		effectiveAt = &t
 	}
 
+	emittedAt := time.Now().UTC()
+	eventID := common.ChooseEventID(meta.ID, s.http.Name, effectiveAt, emittedAt)
+
 	return common.SingleRawEvent(
 		s.Kind(),
 		s.http.Name,
 		standards.SchemaRawNWSObservationV1,
 		eventID,
+		emittedAt,
 		effectiveAt,
 		raw,
 	)
@@ -84,18 +62,13 @@ func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 
 // ---- RAW fetch + minimal metadata decode ----
 
-// observationMeta is a *minimal* decode of the NWS payload used only to build
-// a stable Event.ID and a useful EffectiveAt for the envelope.
 type observationMeta struct {
 	ID         string `json:"id"`
 	Properties struct {
-		StationID string `json:"stationId"`
 		Timestamp string `json:"timestamp"`
 	} `json:"properties"`
 
-	// Convenience fields populated after decode.
 	ParsedTimestamp time.Time `json:"-"`
-	StationID       string    `json:"-"`
 }
 
 func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, observationMeta, error) {
@@ -106,12 +79,10 @@ func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, obse
 
 	var meta observationMeta
 	if err := json.Unmarshal(raw, &meta); err != nil {
-		// If metadata decode fails, still return raw; envelope will fall back to computed ID.
+		// If metadata decode fails, still return raw; envelope will fall back to Source:EffectiveAt.
 		return raw, observationMeta{}, nil
 	}
 
-	meta.StationID = strings.TrimSpace(meta.Properties.StationID)
-
 	tsStr := strings.TrimSpace(meta.Properties.Timestamp)
 	if tsStr != "" {
 		if t, err := time.Parse(time.RFC3339, tsStr); err == nil {

internal/sources/openmeteo/observation.go

@@ -4,8 +4,6 @@ package openmeteo
 import (
 	"context"
 	"encoding/json"
-	"fmt"
-	"strings"
 	"time"
 
 	"gitea.maximumdirect.net/ejr/feedkit/config"
@@ -23,8 +21,6 @@ type ObservationSource struct {
 func NewObservationSource(cfg config.SourceConfig) (*ObservationSource, error) {
 	const driver = "openmeteo_observation"
 
-	// We require params.user_agent for uniformity across sources (even though Open-Meteo
-	// itself does not strictly require a special User-Agent).
 	hs, err := common.NewHTTPSource(driver, cfg, "application/json")
 	if err != nil {
 		return nil, err
@@ -37,30 +33,27 @@ func (s *ObservationSource) Name() string { return s.http.Name }
 
 func (s *ObservationSource) Kind() event.Kind { return event.Kind("observation") }
 
-// Poll fetches Open-Meteo "current" and emits exactly one RAW Event.
 func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 	raw, meta, err := s.fetchRaw(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	eventID := buildEventID(s.http.Name, meta)
-	if strings.TrimSpace(eventID) == "" {
-		// Extremely defensive fallback: keep the envelope valid no matter what.
-		eventID = fmt.Sprintf("openmeteo:current:%s:%s", s.http.Name, time.Now().UTC().Format(time.RFC3339Nano))
-	}
-
 	var effectiveAt *time.Time
 	if !meta.ParsedTimestamp.IsZero() {
 		t := meta.ParsedTimestamp.UTC()
 		effectiveAt = &t
 	}
 
+	emittedAt := time.Now().UTC()
+	eventID := common.ChooseEventID("", s.http.Name, effectiveAt, emittedAt)
+
 	return common.SingleRawEvent(
 		s.Kind(),
 		s.http.Name,
 		standards.SchemaRawOpenMeteoCurrentV1,
 		eventID,
+		emittedAt,
 		effectiveAt,
 		raw,
 	)
@@ -69,10 +62,8 @@ func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 // ---- RAW fetch + minimal metadata decode ----
 
 type openMeteoMeta struct {
-	Latitude         float64 `json:"latitude"`
-	Longitude        float64 `json:"longitude"`
-	Timezone         string  `json:"timezone"`
-	UTCOffsetSeconds int     `json:"utc_offset_seconds"`
+	Timezone         string `json:"timezone"`
+	UTCOffsetSeconds int    `json:"utc_offset_seconds"`
 
 	Current struct {
 		Time string `json:"time"`
@@ -89,31 +80,13 @@ func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, open
 
 	var meta openMeteoMeta
 	if err := json.Unmarshal(raw, &meta); err != nil {
-		// If metadata decode fails, still return raw; envelope will fall back to computed ID without EffectiveAt.
+		// If metadata decode fails, still return raw; envelope will omit EffectiveAt.
 		return raw, openMeteoMeta{}, nil
 	}
 
-	// Best effort: compute a stable EffectiveAt + event ID component.
-	// If parsing fails, we simply omit EffectiveAt and fall back to time.Now() in buildEventID.
 	if t, err := openmeteo.ParseTime(meta.Current.Time, meta.Timezone, meta.UTCOffsetSeconds); err == nil {
 		meta.ParsedTimestamp = t.UTC()
 	}
 
 	return raw, meta, nil
 }
-
-func buildEventID(sourceName string, meta openMeteoMeta) string {
-	locKey := ""
-	if meta.Latitude != 0 || meta.Longitude != 0 {
-		locKey = fmt.Sprintf("coord:%.5f,%.5f", meta.Latitude, meta.Longitude)
-	} else {
-		locKey = "loc:unknown"
-	}
-
-	ts := meta.ParsedTimestamp
-	if ts.IsZero() {
-		ts = time.Now().UTC()
-	}
-
-	return fmt.Sprintf("openmeteo:current:%s:%s:%s", sourceName, locKey, ts.Format(time.RFC3339Nano))
-}

internal/sources/openweather/observation.go

@@ -15,12 +15,6 @@ import (
 	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/standards"
 )
 
-// ObservationSource polls the OpenWeatherMap "Current weather" endpoint and emits a RAW observation Event.
-//
-// IMPORTANT UNIT POLICY (weatherfeeder convention):
-// OpenWeather changes units based on the `units` query parameter but does NOT include the unit
-// system in the response body. To keep normalization deterministic, this driver *requires*
-// `units=metric`. If absent (or non-metric), the driver returns an error.
 type ObservationSource struct {
 	http *common.HTTPSource
 }
@@ -45,7 +39,6 @@ func (s *ObservationSource) Name() string { return s.http.Name }
 func (s *ObservationSource) Kind() event.Kind { return event.Kind("observation") }
 
 func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
-	// Re-check policy defensively (in case the URL is mutated after construction).
 	if err := requireMetricUnits(s.http.URL); err != nil {
 		return nil, fmt.Errorf("%s %q: %w", s.http.Driver, s.http.Name, err)
 	}
@@ -55,22 +48,21 @@ func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 		return nil, err
 	}
 
-	eventID := buildEventID(s.http.Name, meta)
-	if strings.TrimSpace(eventID) == "" {
-		eventID = fmt.Sprintf("openweather:current:%s:%s", s.http.Name, time.Now().UTC().Format(time.RFC3339Nano))
-	}
-
 	var effectiveAt *time.Time
 	if !meta.ParsedTimestamp.IsZero() {
 		t := meta.ParsedTimestamp.UTC()
 		effectiveAt = &t
 	}
 
+	emittedAt := time.Now().UTC()
+	eventID := common.ChooseEventID("", s.http.Name, effectiveAt, emittedAt)
+
 	return common.SingleRawEvent(
 		s.Kind(),
 		s.http.Name,
 		standards.SchemaRawOpenWeatherCurrentV1,
 		eventID,
+		emittedAt,
 		effectiveAt,
 		raw,
 	)
@@ -81,14 +73,6 @@ func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
 type openWeatherMeta struct {
 	Dt int64 `json:"dt"` // unix seconds, UTC
 
-	ID   int64  `json:"id"`
-	Name string `json:"name"`
-
-	Coord struct {
-		Lon float64 `json:"lon"`
-		Lat float64 `json:"lat"`
-	} `json:"coord"`
-
 	ParsedTimestamp time.Time `json:"-"`
 }
 
@@ -110,24 +94,6 @@ func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, open
 	return raw, meta, nil
 }
 
-func buildEventID(sourceName string, meta openWeatherMeta) string {
-	locKey := ""
-	if meta.ID != 0 {
-		locKey = fmt.Sprintf("city:%d", meta.ID)
-	} else if meta.Coord.Lat != 0 || meta.Coord.Lon != 0 {
-		locKey = fmt.Sprintf("coord:%.5f,%.5f", meta.Coord.Lat, meta.Coord.Lon)
-	} else {
-		locKey = "loc:unknown"
-	}
-
-	ts := meta.ParsedTimestamp
-	if ts.IsZero() {
-		ts = time.Now().UTC()
-	}
-
-	return fmt.Sprintf("openweather:current:%s:%s:%s", sourceName, locKey, ts.Format(time.RFC3339Nano))
-}
-
 func requireMetricUnits(rawURL string) error {
 	u, err := url.Parse(strings.TrimSpace(rawURL))
 	if err != nil {