Add collected and derived fact contracts

2026-06-09 20:23:53 +00:00
parent 454f47b2b5
commit e9508089ab
10 changed files with 519 additions and 65 deletions
--- a/docs/internal/app-orchestration.md
+++ b/docs/internal/app-orchestration.md
@@ -6,10 +6,10 @@ This document describes the implemented workflow coordinator in `internal/app`.

 `internal/app` coordinates the top-level use cases after CLI parsing and config
 loading are complete. It resolves report definitions, fetches weather data,
-builds briefing and prompt-input artifacts, invokes Scriptorium through the
-adapter boundary, optionally notifies distributor through an app-owned notifier
-boundary, persists managed state, runs batches, and reads existing artifacts for
-inspection.
+builds collected and derived facts, builds briefing and prompt-input artifacts,
+invokes Scriptorium through the adapter boundary, optionally notifies
+distributor through an app-owned notifier boundary, persists managed state, runs
+batches, and reads existing artifacts for inspection.

 ## Inputs And Outputs

@@ -21,7 +21,7 @@ Inputs:
 - `BriefingRequest` and `ReportRequest` for package-level orchestration tests
  and internal composition
 - resolved report definitions from `internal/report`
- forecast bundles from `internal/adapters/weatherapi`
+- weather data bundles from `internal/adapters/weatherapi`
 - prior snapshots loaded from `internal/state`
 - optional renderer, notifier, and state-store fakes for tests

@@ -39,11 +39,12 @@ Outputs:
 ## Boundaries

 `internal/app` owns workflow order and request composition. It does not parse
-CLI flags, load YAML files directly, implement HTTP transport, derive forecast
-facts, define report periods, compare rendered Markdown, or construct
-Scriptorium argv.
+CLI flags, load YAML files directly, implement HTTP transport, own fact
+derivation algorithms, define report periods, compare rendered Markdown, or
+construct Scriptorium argv.

 Report selection and report identity policy come from `internal/report`.
+Collected and derived fact contracts come from `internal/facts`.
 Weather API transport stays in `internal/adapters/weatherapi`. Scriptorium
 subprocess behavior stays in `internal/adapters/scriptorium`. Distributor
 upload behavior stays in `internal/adapters/distributor`. Filesystem layout and
--- a/docs/internal/briefing.md
+++ b/docs/internal/briefing.md
@@ -5,9 +5,8 @@ This document describes the implemented briefing package boundary.
 ## Purpose

 `internal/briefing` builds structured report-specific briefing packages from
-resolved report metadata, forecast bundles, and derived forecast summaries.
-Briefings are curated inputs for prompt data packages, not rendered report
-prose.
+resolved report metadata, collected weather data, and derived forecast facts.
+Briefings are curated inputs for prompt data packages, not rendered report prose.

 ## Inputs And Outputs

@@ -15,7 +14,7 @@ Inputs:

 - resolved report definition, generation time, timezone, and valid period
 - `weatherdata.Bundle` with source provenance and warnings
- derived daily or period summaries where required
+- derived daily, period, or storm-window facts where required
 - configured units, timezone, and descriptive location context

 Outputs:
@@ -37,7 +36,7 @@ Outputs:
 ## Config Fields Used

 The package receives configured units and timezone from the app layer. Daypart
-configuration is consumed by `internal/forecast` before briefing builders run.
+configuration is consumed by `internal/facts` before briefing builders run.
 Configured `location` values are prompt context only; Weather API
 `sourceLocationId` and `sourceLocation` remain source provenance.
 Current conditions are copied from the normalized `/conditions/current` bundle
--- a/docs/internal/facts.md
+++ b/docs/internal/facts.md
@@ -0,0 +1,72 @@
+# Fact Contracts Internals
+
+This document describes the implemented fact contract boundary.
+
+## Purpose
+
+`internal/facts` separates normalized upstream facts collected for a report run
+from conservative report-scoped facts derived from them. The package gives app
+orchestration one place to build reusable facts before briefing construction.
+
+## Inputs And Outputs
+
+Inputs:
+
+- `weatherdata.Bundle` from the Weather API adapter
+- resolved report definition and valid period
+- report timezone
+- configured daypart definitions
+
+Outputs:
+
+- `facts.CollectedFacts` with normalized source facts plus separate source
+  provenance and warnings
+- `facts.DerivedFacts` with valid-period forecast slices, alert overlaps,
+  daily summaries, daypart summaries, and Storm Report window summary
+
+## Boundaries
+
+- This package owns fact assembly and reusable deterministic derivation for a
+  report run.
+- It does not fetch upstream data, build prompt wording, compare prior
+  snapshots, write workflow state, invoke Scriptorium, or define modules.
+
+## Config Fields Used
+
+- `dayparts[].name`
+- `dayparts[].start`
+- `dayparts[].end`
+- `weather_api.timezone`
+
+## External Adapters Used
+
+None directly. Collected facts are built from `weatherdata.Bundle`.
+
+## State Or Manifest Behavior
+
+None. Source provenance and warnings remain data fields for downstream metadata
+and inspection.
+
+## Failure Behavior
+
+- Invalid or missing report valid periods return an error.
+- Invalid timezone names return an error.
+- Missing required hourly forecast data returns the underlying forecast
+  derivation error for reports that require daily summaries.
+- Missing optional narrative, alert, discussion, daily, or weather story data
+  produces empty or nil derived fields.
+
+## Tests
+
+Inspect:
+
+- `internal/facts/facts_test.go`
+- `internal/app/app_test.go`
+
+## Invariants
+
+- Collected facts are built once from a fetched bundle.
+- Derived facts are scoped to one resolved report.
+- Source provenance and warnings stay separate from ordinary fact fields.
+- Prompt-specific wording and one-off presentation decisions stay outside this
+  package.
--- a/docs/internal/forecast-derivation.md
+++ b/docs/internal/forecast-derivation.md
@@ -5,8 +5,8 @@ This document describes deterministic forecast summarization in

 ## Purpose

-`internal/forecast` converts normalized `weatherdata` bundle data into daily
-and period summaries used by briefing builders.
+`internal/forecast` converts normalized weather data into daily and period
+summaries used by fact builders and briefing builders.

 ## Inputs And Outputs

--- a/docs/policy/development.md
+++ b/docs/policy/development.md
@@ -19,6 +19,7 @@ Developers and LLM coding agents should use it with
 - `internal/weatherdata`: normalized weather source facts, source metadata, and
  source warnings.
 - `internal/forecast`: deterministic forecast derivation.
+- `internal/facts`: collected and derived report fact contracts.
 - `internal/report`: report definitions, valid periods, batches, output names,
  and comparison declarations.
 - `internal/briefing`: report-specific briefing package builders.
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -14,6 +14,7 @@ import (
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/briefing"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/changes"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/config"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/facts"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/fileutil"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/promptinput"
@@ -789,10 +790,7 @@ func distributorUploadFiles(sourcePath string, bundlePaths []string) []distribut
 }

 func BuildBriefing(req BriefingRequest, bundle *weatherdata.Bundle) (briefing.Package, error) {
-	location, err := timeutil.LoadLocation(req.Config.WeatherAPI.Timezone)
-	if err != nil {
-		return briefing.Package{}, err
-	}
+	collected := facts.BuildCollected(bundle)
 	dayparts := make([]forecast.DaypartDefinition, 0, len(req.Config.Dayparts))
 	for _, daypart := range req.Config.Dayparts {
 		dayparts = append(dayparts, forecast.DaypartDefinition{
@@ -801,48 +799,32 @@ func BuildBriefing(req BriefingRequest, bundle *weatherdata.Bundle) (briefing.Pa
 			End:   daypart.End,
 		})
 	}
+	derived, err := facts.BuildDerived(facts.BuildDerivedRequest{
+		Resolved:  req.Resolved,
+		Timezone:  req.Config.WeatherAPI.Timezone,
+		Dayparts:  dayparts,
+		Collected: collected,
+	})
+	if err != nil {
+		return briefing.Package{}, err
+	}
+	buildContext := briefing.BuildContext{
+		Resolved: req.Resolved,
+		Bundle:   collected.Bundle(),
+		Units:    req.Config.WeatherAPI.Units,
+		Timezone: req.Config.WeatherAPI.Timezone,
+		Location: briefingLocation(req.Config),
+	}
 	switch req.Resolved.Definition.ID {
 	case report.DailyToday, report.DailyTomorrow:
-		summary, err := forecast.BuildDailySummary(bundle, req.Resolved.ValidPeriod.Start, location, dayparts)
-		if err != nil {
-			return briefing.Package{}, err
-		}
-		return briefing.BuildDaily(briefing.BuildContext{
-			Resolved: req.Resolved,
-			Bundle:   bundle,
-			Units:    req.Config.WeatherAPI.Units,
-			Timezone: req.Config.WeatherAPI.Timezone,
-			Location: briefingLocation(req.Config),
-		}, summary)
+		return briefing.BuildDaily(buildContext, derived.FirstDailySummary())
 	case report.ThreeDay, report.Weekend:
-		summaries, err := forecast.BuildPeriodDailySummaries(bundle, req.Resolved.ValidPeriod, location, dayparts)
-		if err != nil {
-			return briefing.Package{}, err
-		}
 		if req.Resolved.Definition.ID == report.Weekend {
-			return briefing.BuildWeekend(briefing.BuildContext{
-				Resolved: req.Resolved,
-				Bundle:   bundle,
-				Units:    req.Config.WeatherAPI.Units,
-				Timezone: req.Config.WeatherAPI.Timezone,
-				Location: briefingLocation(req.Config),
-			}, summaries)
+			return briefing.BuildWeekend(buildContext, derived.DailySummaries)
 		}
-		return briefing.BuildThreeDay(briefing.BuildContext{
-			Resolved: req.Resolved,
-			Bundle:   bundle,
-			Units:    req.Config.WeatherAPI.Units,
-			Timezone: req.Config.WeatherAPI.Timezone,
-			Location: briefingLocation(req.Config),
-		}, summaries)
+		return briefing.BuildThreeDay(buildContext, derived.DailySummaries)
 	case report.Storm:
-		return briefing.BuildStorm(briefing.BuildContext{
-			Resolved: req.Resolved,
-			Bundle:   bundle,
-			Units:    req.Config.WeatherAPI.Units,
-			Timezone: req.Config.WeatherAPI.Timezone,
-			Location: briefingLocation(req.Config),
-		})
+		return briefing.BuildStorm(buildContext, derived)
 	default:
 		return briefing.Package{}, fmt.Errorf("briefing is not implemented for report %q", req.Resolved.Definition.ID)
 	}
--- a/internal/briefing/storm.go
+++ b/internal/briefing/storm.go
@@ -3,6 +3,7 @@ package briefing
 import (
 	"fmt"

+	"gitea.maximumdirect.net/eric/weatherreporter/internal/facts"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
@@ -26,7 +27,7 @@ type Storm struct {
 	WeatherStory        *WeatherStoryContext         `json:"weatherStory,omitempty"`
 }

-func BuildStorm(ctx BuildContext) (Package, error) {
+func BuildStorm(ctx BuildContext, derived facts.DerivedFacts) (Package, error) {
 	if ctx.Resolved.Definition.ID != report.Storm {
 		return Package{}, fmt.Errorf("storm briefing requires a storm report definition")
 	}
@@ -34,12 +35,14 @@ func BuildStorm(ctx BuildContext) (Package, error) {
 		return Package{}, fmt.Errorf("forecast bundle is required")
 	}
 	period := ctx.Resolved.ValidPeriod
-	hourly := forecast.SelectHourlyPeriods(ctx.Bundle.Hourly, period)
-	narrative := forecast.SelectNarrativePeriods(ctx.Bundle, period)
-	daily := forecast.SelectHourlyPeriods(ctx.Bundle.Daily, period)
-	alerts := forecast.AlertOverlaps(ctx.Bundle.Alerts, period)
-	summary := forecast.SummarizeDaypart("storm window", period, hourly)
-	summary.AlertOverlaps = alerts
+	hourly := derived.ValidPeriodHourlyPeriods
+	narrative := derived.ValidPeriodNarrativePeriods
+	daily := derived.ValidPeriodDailyPeriods
+	alerts := derived.AlertOverlaps
+	if derived.StormWindowSummary == nil {
+		return Package{}, fmt.Errorf("storm window summary is required")
+	}
+	summary := *derived.StormWindowSummary

 	storm := &Storm{
 		TimingWindow:        period,
--- a/internal/briefing/storm_test.go
+++ b/internal/briefing/storm_test.go
@@ -6,6 +6,8 @@ import (
 	"testing"
 	"time"

+	"gitea.maximumdirect.net/eric/weatherreporter/internal/facts"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
 )
@@ -62,7 +64,7 @@ func TestStormBriefingWithActiveAlert(t *testing.T) {
 		Sources: []weatherdata.Source{{Name: "hourly", FetchedAt: time.Now()}},
 	}

-	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"})
+	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"}, stormDerivedFacts(t, resolved, bundle))
 	if err != nil {
 		t.Fatalf("BuildStorm() error = %v", err)
 	}
@@ -120,7 +122,7 @@ func TestStormBriefingWithDiscussionButNoAlert(t *testing.T) {
 		Sources:    []weatherdata.Source{{Name: "hourly", FetchedAt: time.Now()}},
 	}

-	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"})
+	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"}, stormDerivedFacts(t, resolved, bundle))
 	if err != nil {
 		t.Fatalf("BuildStorm() error = %v", err)
 	}
@@ -155,7 +157,7 @@ func TestStormBriefingQuietWindow(t *testing.T) {
 		Sources: []weatherdata.Source{{Name: "hourly", FetchedAt: time.Now()}},
 	}

-	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"})
+	pkg, err := BuildStorm(BuildContext{Resolved: resolved, Bundle: bundle, Units: "us", Timezone: "America/Chicago"}, stormDerivedFacts(t, resolved, bundle))
 	if err != nil {
 		t.Fatalf("BuildStorm() error = %v", err)
 	}
@@ -167,3 +169,17 @@ func TestStormBriefingQuietWindow(t *testing.T) {
 		t.Fatalf("WhatToWatchNext = %#v, want watch fallback", pkg.Storm.WhatToWatchNext)
 	}
 }
+
+func stormDerivedFacts(t *testing.T, resolved report.Resolved, bundle *weatherdata.Bundle) facts.DerivedFacts {
+	t.Helper()
+	derived, err := facts.BuildDerived(facts.BuildDerivedRequest{
+		Resolved:  resolved,
+		Timezone:  "America/Chicago",
+		Dayparts:  []forecast.DaypartDefinition{{Name: "morning", Start: "06:00", End: "12:00"}},
+		Collected: facts.BuildCollected(bundle),
+	})
+	if err != nil {
+		t.Fatalf("build derived facts: %v", err)
+	}
+	return derived
+}
--- a/internal/facts/facts.go
+++ b/internal/facts/facts.go
@@ -0,0 +1,139 @@
+// Package facts defines collected and derived report facts.
+package facts
+
+import (
+	"fmt"
+	"time"
+
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
+)
+
+type CollectedFacts struct {
+	FetchedAt    time.Time
+	Observation  *weatherdata.Observation
+	Current      *weatherdata.Current
+	Hourly       *weatherdata.ForecastRun
+	Narrative    *weatherdata.ForecastRun
+	Alerts       *weatherdata.AlertRun
+	Discussion   *weatherdata.Discussion
+	Daily        *weatherdata.ForecastRun
+	WeatherStory *weatherdata.WeatherStory
+
+	SourceProvenance []weatherdata.Source
+	SourceWarnings   []weatherdata.SourceWarning
+}
+
+func BuildCollected(bundle *weatherdata.Bundle) CollectedFacts {
+	if bundle == nil {
+		return CollectedFacts{}
+	}
+	return CollectedFacts{
+		FetchedAt:        bundle.FetchedAt,
+		Observation:      bundle.Observation,
+		Current:          bundle.Current,
+		Hourly:           bundle.Hourly,
+		Narrative:        bundle.Narrative,
+		Alerts:           bundle.Alerts,
+		Discussion:       bundle.Discussion,
+		Daily:            bundle.Daily,
+		WeatherStory:     bundle.WeatherStory,
+		SourceProvenance: append([]weatherdata.Source(nil), bundle.Sources...),
+		SourceWarnings:   append([]weatherdata.SourceWarning(nil), bundle.Warnings...),
+	}
+}
+
+func (f CollectedFacts) Bundle() *weatherdata.Bundle {
+	return &weatherdata.Bundle{
+		FetchedAt:    f.FetchedAt,
+		Observation:  f.Observation,
+		Current:      f.Current,
+		Hourly:       f.Hourly,
+		Narrative:    f.Narrative,
+		Alerts:       f.Alerts,
+		Discussion:   f.Discussion,
+		Daily:        f.Daily,
+		WeatherStory: f.WeatherStory,
+		Sources:      append([]weatherdata.Source(nil), f.SourceProvenance...),
+		Warnings:     append([]weatherdata.SourceWarning(nil), f.SourceWarnings...),
+	}
+}
+
+type BuildDerivedRequest struct {
+	Resolved  report.Resolved
+	Timezone  string
+	Dayparts  []forecast.DaypartDefinition
+	Collected CollectedFacts
+}
+
+type DerivedFacts struct {
+	ValidPeriodHourlyPeriods    []weatherdata.ForecastPeriod
+	ValidPeriodNarrativePeriods []weatherdata.ForecastPeriod
+	ValidPeriodDailyPeriods     []weatherdata.ForecastPeriod
+	AlertOverlaps               []forecast.AlertOverlap
+	DailySummaries              []forecast.DailySummary
+	DaypartSummaries            []forecast.DaypartSummary
+	StormWindowSummary          *forecast.DaypartSummary
+}
+
+func (f DerivedFacts) FirstDailySummary() *forecast.DailySummary {
+	if len(f.DailySummaries) == 0 {
+		return nil
+	}
+	return &f.DailySummaries[0]
+}
+
+func BuildDerived(req BuildDerivedRequest) (DerivedFacts, error) {
+	if !req.Resolved.ValidPeriod.IsValid() {
+		return DerivedFacts{}, fmt.Errorf("resolved valid period is required")
+	}
+	location, err := timeutil.LoadLocation(req.Timezone)
+	if err != nil {
+		return DerivedFacts{}, fmt.Errorf("load report timezone %q: %w", req.Timezone, err)
+	}
+	bundle := req.Collected.Bundle()
+	period := req.Resolved.ValidPeriod
+	derived := DerivedFacts{
+		ValidPeriodHourlyPeriods:    forecast.SelectHourlyPeriods(req.Collected.Hourly, period),
+		ValidPeriodNarrativePeriods: forecast.SelectHourlyPeriods(req.Collected.Narrative, period),
+		ValidPeriodDailyPeriods:     forecast.SelectHourlyPeriods(req.Collected.Daily, period),
+		AlertOverlaps:               forecast.AlertOverlaps(req.Collected.Alerts, period),
+	}
+
+	switch req.Resolved.Definition.ID {
+	case report.DailyToday, report.DailyTomorrow:
+		summary, err := forecast.BuildDailySummary(bundle, period.Start, location, req.Dayparts)
+		if err != nil {
+			return DerivedFacts{}, err
+		}
+		derived.DailySummaries = []forecast.DailySummary{*summary}
+	case report.ThreeDay, report.Weekend:
+		summaries, err := forecast.BuildPeriodDailySummaries(bundle, period, location, req.Dayparts)
+		if err != nil {
+			return DerivedFacts{}, err
+		}
+		derived.DailySummaries = summaries
+	case report.Storm:
+		summary := forecast.SummarizeDaypart("storm window", period, derived.ValidPeriodHourlyPeriods)
+		summary.AlertOverlaps = derived.AlertOverlaps
+		derived.StormWindowSummary = &summary
+	default:
+		return DerivedFacts{}, fmt.Errorf("derived facts are not implemented for report %q", req.Resolved.Definition.ID)
+	}
+
+	derived.DaypartSummaries = collectDaypartSummaries(derived)
+	return derived, nil
+}
+
+func collectDaypartSummaries(derived DerivedFacts) []forecast.DaypartSummary {
+	var out []forecast.DaypartSummary
+	for _, summary := range derived.DailySummaries {
+		out = append(out, summary.Dayparts...)
+	}
+	if derived.StormWindowSummary != nil {
+		out = append(out, *derived.StormWindowSummary)
+	}
+	return out
+}
--- a/internal/facts/facts_test.go
+++ b/internal/facts/facts_test.go
@@ -0,0 +1,241 @@
+package facts
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
+)
+
+func TestBuildCollectedCopiesBundleFactsAndKeepsSourcesSeparate(t *testing.T) {
+	fetchedAt := mustParse("2026-05-29T10:00:00Z")
+	bundle := &weatherdata.Bundle{
+		FetchedAt: fetchedAt,
+		Current:   &weatherdata.Current{ConditionText: "Clear"},
+		Hourly:    &weatherdata.ForecastRun{Product: "hourly"},
+		Sources:   []weatherdata.Source{{Name: "hourly"}},
+		Warnings:  []weatherdata.SourceWarning{{Source: "daily", Code: "missing_source"}},
+	}
+
+	collected := BuildCollected(bundle)
+	if collected.FetchedAt != fetchedAt || collected.Current.ConditionText != "Clear" || collected.Hourly.Product != "hourly" {
+		t.Fatalf("CollectedFacts = %#v, want source facts copied from bundle", collected)
+	}
+	if len(collected.SourceProvenance) != 1 || collected.SourceProvenance[0].Name != "hourly" {
+		t.Fatalf("SourceProvenance = %#v, want hourly source", collected.SourceProvenance)
+	}
+	if len(collected.SourceWarnings) != 1 || collected.SourceWarnings[0].Source != "daily" {
+		t.Fatalf("SourceWarnings = %#v, want daily warning", collected.SourceWarnings)
+	}
+
+	bundle.Sources[0].Name = "changed"
+	bundle.Warnings[0].Source = "changed"
+	if collected.SourceProvenance[0].Name != "hourly" || collected.SourceWarnings[0].Source != "daily" {
+		t.Fatalf("collected source slices changed after bundle mutation: %#v %#v", collected.SourceProvenance, collected.SourceWarnings)
+	}
+}
+
+func TestBuildDerivedDailySlicesDaypartsAndAlerts(t *testing.T) {
+	location := testLocation()
+	resolved := resolveForTest(t, report.DailyToday, mustParse("2026-05-29T08:00:00-05:00"), location)
+	derived, err := BuildDerived(BuildDerivedRequest{
+		Resolved:  resolved,
+		Timezone:  location.String(),
+		Dayparts:  testDayparts(),
+		Collected: BuildCollected(testBundle(location)),
+	})
+	if err != nil {
+		t.Fatalf("BuildDerived() error = %v", err)
+	}
+
+	if len(derived.ValidPeriodHourlyPeriods) != 4 {
+		t.Fatalf("ValidPeriodHourlyPeriods length = %d, want 4", len(derived.ValidPeriodHourlyPeriods))
+	}
+	if len(derived.ValidPeriodNarrativePeriods) != 1 {
+		t.Fatalf("ValidPeriodNarrativePeriods length = %d, want 1", len(derived.ValidPeriodNarrativePeriods))
+	}
+	if len(derived.AlertOverlaps) != 1 || derived.AlertOverlaps[0].Event != "Flood Watch" {
+		t.Fatalf("AlertOverlaps = %#v, want Flood Watch overlap", derived.AlertOverlaps)
+	}
+	if len(derived.DailySummaries) != 1 || len(derived.DailySummaries[0].Dayparts) != 3 {
+		t.Fatalf("DailySummaries = %#v, want one summary with dayparts", derived.DailySummaries)
+	}
+	if len(derived.DaypartSummaries) != 3 {
+		t.Fatalf("DaypartSummaries length = %d, want 3", len(derived.DaypartSummaries))
+	}
+	morning := derived.DailySummaries[0].Dayparts[0]
+	if len(morning.HourlyPeriods) != 1 || morning.MaxPrecipitationProbability == nil || morning.MaxPrecipitationProbability.Value != 60 {
+		t.Fatalf("morning summary = %#v, want sliced hour with precip max", morning)
+	}
+}
+
+func TestBuildDerivedOutlookBuildsPartialDaySummariesWithMissingOptionalSources(t *testing.T) {
+	location := testLocation()
+	resolved := resolveForTest(t, report.ThreeDay, mustParse("2026-05-29T08:00:00-05:00"), location)
+	bundle := testBundle(location)
+	bundle.Narrative = nil
+	bundle.Alerts = nil
+	bundle.Discussion = nil
+	bundle.WeatherStory = nil
+
+	derived, err := BuildDerived(BuildDerivedRequest{
+		Resolved:  resolved,
+		Timezone:  location.String(),
+		Dayparts:  testDayparts(),
+		Collected: BuildCollected(bundle),
+	})
+	if err != nil {
+		t.Fatalf("BuildDerived() error = %v", err)
+	}
+
+	if len(derived.DailySummaries) != 3 {
+		t.Fatalf("DailySummaries length = %d, want 3 partial-day summaries", len(derived.DailySummaries))
+	}
+	if len(derived.ValidPeriodNarrativePeriods) != 0 {
+		t.Fatalf("ValidPeriodNarrativePeriods length = %d, want 0 for missing optional source", len(derived.ValidPeriodNarrativePeriods))
+	}
+	if len(derived.AlertOverlaps) != 0 {
+		t.Fatalf("AlertOverlaps = %#v, want none for missing optional alerts", derived.AlertOverlaps)
+	}
+	if derived.DailySummaries[0].Period.Start.Format(time.RFC3339) != "2026-05-29T08:00:00-05:00" {
+		t.Fatalf("first summary start = %s, want valid-period start", derived.DailySummaries[0].Period.Start.Format(time.RFC3339))
+	}
+}
+
+func TestBuildDerivedWeekendAndTomorrow(t *testing.T) {
+	location := testLocation()
+	for _, id := range []report.ID{report.DailyTomorrow, report.Weekend} {
+		resolved := resolveForTest(t, id, mustParse("2026-05-29T08:00:00-05:00"), location)
+		derived, err := BuildDerived(BuildDerivedRequest{
+			Resolved:  resolved,
+			Timezone:  location.String(),
+			Dayparts:  testDayparts(),
+			Collected: BuildCollected(testBundle(location)),
+		})
+		if err != nil {
+			t.Fatalf("BuildDerived(%s) error = %v", id, err)
+		}
+		if len(derived.DailySummaries) == 0 {
+			t.Fatalf("BuildDerived(%s) DailySummaries length = 0, want summaries", id)
+		}
+	}
+}
+
+func TestBuildDerivedStormBuildsWindowSummary(t *testing.T) {
+	location := testLocation()
+	resolved := resolveStormForTest(t, location)
+	derived, err := BuildDerived(BuildDerivedRequest{
+		Resolved:  resolved,
+		Timezone:  location.String(),
+		Dayparts:  testDayparts(),
+		Collected: BuildCollected(testBundle(location)),
+	})
+	if err != nil {
+		t.Fatalf("BuildDerived() error = %v", err)
+	}
+
+	if len(derived.ValidPeriodHourlyPeriods) != 2 {
+		t.Fatalf("ValidPeriodHourlyPeriods length = %d, want 2 storm-window hours", len(derived.ValidPeriodHourlyPeriods))
+	}
+	if len(derived.ValidPeriodDailyPeriods) != 1 {
+		t.Fatalf("ValidPeriodDailyPeriods length = %d, want 1 daily period", len(derived.ValidPeriodDailyPeriods))
+	}
+	if derived.StormWindowSummary == nil {
+		t.Fatal("StormWindowSummary = nil, want summary")
+	}
+	if derived.StormWindowSummary.MaxPrecipitationProbability == nil || derived.StormWindowSummary.MaxPrecipitationProbability.Value != 80 {
+		t.Fatalf("StormWindowSummary = %#v, want peak precipitation", derived.StormWindowSummary)
+	}
+	if len(derived.StormWindowSummary.AlertOverlaps) != 1 {
+		t.Fatalf("StormWindowSummary.AlertOverlaps length = %d, want 1", len(derived.StormWindowSummary.AlertOverlaps))
+	}
+}
+
+func testBundle(location *time.Location) *weatherdata.Bundle {
+	return &weatherdata.Bundle{
+		FetchedAt: mustParse("2026-05-29T10:00:00Z"),
+		Current:   &weatherdata.Current{ConditionText: "Cloudy"},
+		Hourly: &weatherdata.ForecastRun{Periods: []weatherdata.ForecastPeriod{
+			hour(location, "2026-05-29T08:00:00-05:00", "2026-05-29T09:00:00-05:00", "Showers", 60, 10),
+			hour(location, "2026-05-29T12:00:00-05:00", "2026-05-29T13:00:00-05:00", "Thunderstorms", 80, 35),
+			hour(location, "2026-05-29T13:00:00-05:00", "2026-05-29T14:00:00-05:00", "Heavy rain", 70, 25),
+			hour(location, "2026-05-29T14:00:00-05:00", "2026-05-29T15:00:00-05:00", "Hot", 10, 15),
+			hour(location, "2026-05-30T09:00:00-05:00", "2026-05-30T10:00:00-05:00", "Clear", 0, 5),
+		}},
+		Narrative: &weatherdata.ForecastRun{Periods: []weatherdata.ForecastPeriod{
+			hour(location, "2026-05-29T06:00:00-05:00", "2026-05-29T18:00:00-05:00", "Storm chances peak midday.", 70, 20),
+		}},
+		Daily: &weatherdata.ForecastRun{Periods: []weatherdata.ForecastPeriod{
+			hour(location, "2026-05-29T00:00:00-05:00", "2026-05-30T00:00:00-05:00", "Storms", 70, 20),
+		}},
+		Alerts: &weatherdata.AlertRun{Alerts: []json.RawMessage{
+			json.RawMessage(`{"event":"Flood Watch","headline":"Flooding possible","severity":"Moderate","effective":"2026-05-29T11:00:00-05:00","expires":"2026-05-29T15:00:00-05:00"}`),
+		}},
+		Discussion:   &weatherdata.Discussion{Product: "discussion", KeyMessages: []string{"Storm confidence is moderate."}},
+		WeatherStory: &weatherdata.WeatherStory{Title: "Storm Risk"},
+		Sources:      []weatherdata.Source{{Name: "hourly"}},
+		Warnings:     []weatherdata.SourceWarning{{Source: "daily", Code: "missing_source"}},
+	}
+}
+
+func hour(location *time.Location, start string, end string, text string, precip float64, gust float64) weatherdata.ForecastPeriod {
+	temperature := 70.0
+	return weatherdata.ForecastPeriod{
+		StartTime:                         mustParse(start).In(location),
+		EndTime:                           mustParse(end).In(location),
+		TextDescription:                   text,
+		TemperatureF:                      &temperature,
+		ProbabilityOfPrecipitationPercent: &precip,
+		WindGustMph:                       &gust,
+	}
+}
+
+func testDayparts() []forecast.DaypartDefinition {
+	return []forecast.DaypartDefinition{
+		{Name: "morning", Start: "06:00", End: "12:00"},
+		{Name: "afternoon", Start: "12:00", End: "18:00"},
+		{Name: "evening", Start: "18:00", End: "24:00"},
+	}
+}
+
+func resolveForTest(t *testing.T, id report.ID, now time.Time, location *time.Location) report.Resolved {
+	t.Helper()
+	resolved, err := report.Resolve(id, report.ResolveRequest{Now: now, Location: location})
+	if err != nil {
+		t.Fatalf("resolve %s: %v", id, err)
+	}
+	return resolved
+}
+
+func resolveStormForTest(t *testing.T, location *time.Location) report.Resolved {
+	t.Helper()
+	resolved, err := report.Resolve(report.Storm, report.ResolveRequest{
+		Now:        mustParse("2026-05-29T08:00:00-05:00"),
+		Location:   location,
+		StormStart: mustParse("2026-05-29T11:30:00-05:00"),
+		StormEnd:   mustParse("2026-05-29T13:30:00-05:00"),
+	})
+	if err != nil {
+		t.Fatalf("resolve storm: %v", err)
+	}
+	return resolved
+}
+
+func testLocation() *time.Location {
+	location, err := time.LoadLocation("America/Chicago")
+	if err != nil {
+		panic(err)
+	}
+	return location
+}
+
+func mustParse(value string) time.Time {
+	parsed, err := time.Parse(time.RFC3339, value)
+	if err != nil {
+		panic(err)
+	}
+	return parsed
+}