feat(discovery): persist and display per-source contributions for merged queue rows

Migration 000018 adds sources text[] + source_contributions jsonb columns to discovered_markets. Crawler's merger now preserves the raw per-source RawEvents through Merge() so they can be stored alongside the merged row. Admin UI gains two surfaces: (a) compact "merged from source1 + source2" chip + amber Datumskonflikt badge when hinweis flags it, (b) expandable Quellen-Vergleich panel showing a per-field comparison table with diverging fields highlighted. Forensic visibility into what each source said vs what the merger picked.
2026-04-19 00:27:34 +02:00
parent f22a141615
commit cc6c4f2efb
11 changed files with 393 additions and 52 deletions
--- a/backend/internal/domain/discovery/crawler/merger.go
+++ b/backend/internal/domain/discovery/crawler/merger.go
@@ -172,6 +172,7 @@ func mergeGroup(raws []RawEvent) MergedEvent {

 	m.Quellen = sortedKeys(quellenSet)
 	m.Sources = sortedKeys(sourceSet)
+	m.Contributions = raws // raws is sorted by source rank (best first)
 	return m
 }

--- a/backend/internal/domain/discovery/crawler/types.go
+++ b/backend/internal/domain/discovery/crawler/types.go
@@ -47,6 +47,11 @@ type MergedEvent struct {
 	Quellen    []string
 	Hinweis    string
 	Sources    []string
+
+	// Contributions holds the raw per-source inputs that fed this merge.
+	// Preserved so downstream code can surface per-field conflicts in the
+	// admin UI without re-running merger logic.
+	Contributions []RawEvent
 }

 // SourceError records a per-source failure without stopping the whole crawl.
--- a/backend/internal/domain/discovery/model.go
+++ b/backend/internal/domain/discovery/model.go
@@ -7,6 +7,25 @@ import (
 	"github.com/google/uuid"
 )

+// SourceContribution captures what one source reported about a market.
+// Persisted as a JSONB array in discovered_markets.source_contributions
+// so the admin UI can render per-field conflicts between sources.
+type SourceContribution struct {
+	SourceName string     `json:"source_name"`
+	SourceURL  string     `json:"source_url,omitempty"`
+	DetailURL  string     `json:"detail_url,omitempty"`
+	Name       string     `json:"name,omitempty"`
+	City       string     `json:"city,omitempty"`
+	PLZ        string     `json:"plz,omitempty"`
+	Land       string     `json:"land,omitempty"`
+	Bundesland string     `json:"bundesland,omitempty"`
+	StartDate  *time.Time `json:"start_date,omitempty"`
+	EndDate    *time.Time `json:"end_date,omitempty"`
+	Website    string     `json:"website,omitempty"`
+	Venue      string     `json:"venue,omitempty"`
+	Organizer  string     `json:"organizer,omitempty"`
+}
+
 // Bucket is a scheduler row: one (land, region, year_month, halbmonat) tuple.
 // Halbmonat splits the month into H1 (days 1-15) and H2 (days 16-EOM) so each
 // Pass 0 call covers a smaller window and fits within the 4096-token response.
@@ -26,26 +45,28 @@ type Bucket struct {
 // the separate confirmation signal from Pass 0 (bestaetigt|unklar|
 // vorjahr_unbestaetigt|abgesagt).
 type DiscoveredMarket struct {
-	ID               uuid.UUID  `json:"id"`
-	BucketID         *uuid.UUID `json:"bucket_id"`
-	MarktName        string     `json:"markt_name"`
-	Stadt            string     `json:"stadt"`
-	Bundesland       string     `json:"bundesland"`
-	Land             string     `json:"land"`
-	StartDatum       *time.Time `json:"start_datum"`
-	EndDatum         *time.Time `json:"end_datum"`
-	Website          string     `json:"website"`
-	Quellen          []string   `json:"quellen"`
-	Konfidenz        string     `json:"konfidenz"`    // 'hoch' | 'mittel' | 'niedrig'
-	AgentStatus      string     `json:"agent_status"` // 'bestaetigt' | 'unklar' | 'vorjahr_unbestaetigt' | 'abgesagt'
-	Hinweis          string     `json:"hinweis"`
-	NameNormalized   string     `json:"name_normalized"`
-	MatchedSeriesID  *uuid.UUID `json:"matched_series_id"`
-	Status           string     `json:"status"` // queue lifecycle
-	DiscoveredAt     time.Time  `json:"discovered_at"`
-	ReviewedAt       *time.Time `json:"reviewed_at"`
-	ReviewedBy       *uuid.UUID `json:"reviewed_by"`
-	CreatedEditionID *uuid.UUID `json:"created_edition_id"`
+	ID                  uuid.UUID            `json:"id"`
+	BucketID            *uuid.UUID           `json:"bucket_id"`
+	MarktName           string               `json:"markt_name"`
+	Stadt               string               `json:"stadt"`
+	Bundesland          string               `json:"bundesland"`
+	Land                string               `json:"land"`
+	StartDatum          *time.Time           `json:"start_datum"`
+	EndDatum            *time.Time           `json:"end_datum"`
+	Website             string               `json:"website"`
+	Quellen             []string             `json:"quellen"`
+	Sources             []string             `json:"sources"`
+	SourceContributions []SourceContribution `json:"source_contributions"`
+	Konfidenz           string               `json:"konfidenz"`    // 'hoch' | 'mittel' | 'niedrig'
+	AgentStatus         string               `json:"agent_status"` // 'bestaetigt' | 'unklar' | 'vorjahr_unbestaetigt' | 'abgesagt'
+	Hinweis             string               `json:"hinweis"`
+	NameNormalized      string               `json:"name_normalized"`
+	MatchedSeriesID     *uuid.UUID           `json:"matched_series_id"`
+	Status              string               `json:"status"` // queue lifecycle
+	DiscoveredAt        time.Time            `json:"discovered_at"`
+	ReviewedAt          *time.Time           `json:"reviewed_at"`
+	ReviewedBy          *uuid.UUID           `json:"reviewed_by"`
+	CreatedEditionID    *uuid.UUID           `json:"created_edition_id"`
 }

 // RejectedDiscovery stores a sticky rejection scoped to (normalized_name, city, year).
--- a/backend/internal/domain/discovery/repository.go
+++ b/backend/internal/domain/discovery/repository.go
@@ -3,6 +3,7 @@ package discovery

 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"time"

@@ -71,15 +72,21 @@ func (r *pgRepository) EditionExists(ctx context.Context, seriesID uuid.UUID, ye
 }

 func (r *pgRepository) InsertDiscovered(ctx context.Context, d DiscoveredMarket) (uuid.UUID, error) {
+	contribJSON, err := json.Marshal(d.SourceContributions)
+	if err != nil {
+		return uuid.Nil, fmt.Errorf("marshal source_contributions: %w", err)
+	}
 	var id uuid.UUID
-	err := r.pool.QueryRow(ctx, `
+	err = r.pool.QueryRow(ctx, `
 INSERT INTO discovered_markets
  (bucket_id, markt_name, stadt, bundesland, land, start_datum, end_datum, website,
-   quellen, konfidenz, agent_status, hinweis, name_normalized, matched_series_id)
-VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14)
+   quellen, konfidenz, agent_status, hinweis, name_normalized, matched_series_id,
+   sources, source_contributions)
+VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16)
 RETURNING id`,
 		d.BucketID, d.MarktName, d.Stadt, d.Bundesland, d.Land, d.StartDatum, d.EndDatum, d.Website,
-		d.Quellen, nilIfEmpty(d.Konfidenz), nilIfEmpty(d.AgentStatus), d.Hinweis, d.NameNormalized, d.MatchedSeriesID).Scan(&id)
+		d.Quellen, nilIfEmpty(d.Konfidenz), nilIfEmpty(d.AgentStatus), d.Hinweis, d.NameNormalized, d.MatchedSeriesID,
+		d.Sources, contribJSON).Scan(&id)
 	return id, err
 }

@@ -116,7 +123,8 @@ func (r *pgRepository) ListQueue(ctx context.Context, status string, limit, offs
 SELECT id, bucket_id, markt_name, stadt, coalesce(bundesland,''), land,
       start_datum, end_datum, coalesce(website,''), quellen, coalesce(konfidenz,''),
       coalesce(agent_status,''), coalesce(hinweis,''), name_normalized, matched_series_id, status,
-       discovered_at, reviewed_at, reviewed_by, created_edition_id
+       discovered_at, reviewed_at, reviewed_by, created_edition_id,
+       sources, source_contributions
 FROM discovered_markets
 WHERE status = $1
 ORDER BY discovered_at DESC
@@ -127,13 +135,8 @@ LIMIT $2 OFFSET $3`, status, limit, offset)
 	defer rows.Close()
 	out := make([]DiscoveredMarket, 0)
 	for rows.Next() {
-		var d DiscoveredMarket
-		if err := rows.Scan(
-			&d.ID, &d.BucketID, &d.MarktName, &d.Stadt, &d.Bundesland, &d.Land,
-			&d.StartDatum, &d.EndDatum, &d.Website, &d.Quellen, &d.Konfidenz,
-			&d.AgentStatus, &d.Hinweis, &d.NameNormalized, &d.MatchedSeriesID, &d.Status,
-			&d.DiscoveredAt, &d.ReviewedAt, &d.ReviewedBy, &d.CreatedEditionID,
-		); err != nil {
+		d, err := scanDiscoveredMarket(rows)
+		if err != nil {
 			return nil, err
 		}
 		out = append(out, d)
@@ -149,19 +152,48 @@ func (r *pgRepository) CountQueue(ctx context.Context, status string) (int, erro
 }

 func (r *pgRepository) GetDiscovered(ctx context.Context, id uuid.UUID) (DiscoveredMarket, error) {
-	var d DiscoveredMarket
-	err := r.pool.QueryRow(ctx, `
+	row := r.pool.QueryRow(ctx, `
 SELECT id, bucket_id, markt_name, stadt, coalesce(bundesland,''), land,
       start_datum, end_datum, coalesce(website,''), quellen, coalesce(konfidenz,''),
       coalesce(agent_status,''), coalesce(hinweis,''), name_normalized, matched_series_id, status,
-       discovered_at, reviewed_at, reviewed_by, created_edition_id
-FROM discovered_markets WHERE id = $1`, id).Scan(
+       discovered_at, reviewed_at, reviewed_by, created_edition_id,
+       sources, source_contributions
+FROM discovered_markets WHERE id = $1`, id)
+	return scanDiscoveredMarket(row)
+}
+
+// scanner is the common interface between pgx.Row and pgx.Rows, both of which
+// expose a Scan method with identical signature.
+type scanner interface {
+	Scan(dest ...any) error
+}
+
+// scanDiscoveredMarket reads one DiscoveredMarket from a pgx row/rows scanner.
+// Used by both ListQueue and GetDiscovered to stay in sync with the column list.
+func scanDiscoveredMarket(s scanner) (DiscoveredMarket, error) {
+	var d DiscoveredMarket
+	var contribJSON []byte
+	if err := s.Scan(
 		&d.ID, &d.BucketID, &d.MarktName, &d.Stadt, &d.Bundesland, &d.Land,
 		&d.StartDatum, &d.EndDatum, &d.Website, &d.Quellen, &d.Konfidenz,
 		&d.AgentStatus, &d.Hinweis, &d.NameNormalized, &d.MatchedSeriesID, &d.Status,
 		&d.DiscoveredAt, &d.ReviewedAt, &d.ReviewedBy, &d.CreatedEditionID,
-	)
-	return d, err
+		&d.Sources, &contribJSON,
+	); err != nil {
+		return DiscoveredMarket{}, err
+	}
+	if len(contribJSON) > 0 {
+		if err := json.Unmarshal(contribJSON, &d.SourceContributions); err != nil {
+			return DiscoveredMarket{}, fmt.Errorf("unmarshal source_contributions: %w", err)
+		}
+	}
+	if d.Sources == nil {
+		d.Sources = []string{}
+	}
+	if d.SourceContributions == nil {
+		d.SourceContributions = []SourceContribution{}
+	}
+	return d, nil
 }

 func (r *pgRepository) MarkAccepted(ctx context.Context, tx pgx.Tx, id, editionID, reviewer uuid.UUID) error {
--- a/backend/internal/domain/discovery/service.go
+++ b/backend/internal/domain/discovery/service.go
@@ -200,20 +200,22 @@ func (s *Service) Crawl(ctx context.Context) (CrawlSummary, error) {
 		}

 		dm := DiscoveredMarket{
-			BucketID:        nil,
-			MarktName:       m.Name,
-			Stadt:           m.City,
-			Bundesland:      m.Bundesland,
-			Land:            m.Land,
-			StartDatum:      m.StartDate,
-			EndDatum:        endDatum,
-			Website:         website,
-			Quellen:         quellen,
-			Konfidenz:       crawlerKonfidenz(m),
-			AgentStatus:     AgentStatusCrawler,
-			Hinweis:         m.Hinweis,
-			NameNormalized:  nameNorm,
-			MatchedSeriesID: matchedSeriesID,
+			BucketID:            nil,
+			MarktName:           m.Name,
+			Stadt:               m.City,
+			Bundesland:          m.Bundesland,
+			Land:                m.Land,
+			StartDatum:          m.StartDate,
+			EndDatum:            endDatum,
+			Website:             website,
+			Quellen:             quellen,
+			Sources:             m.Sources,
+			SourceContributions: toContributions(m.Contributions),
+			Konfidenz:           crawlerKonfidenz(m),
+			AgentStatus:         AgentStatusCrawler,
+			Hinweis:             m.Hinweis,
+			NameNormalized:      nameNorm,
+			MatchedSeriesID:     matchedSeriesID,
 		}

 		issues := ValidateForInsert(dm, nil)
@@ -444,6 +446,30 @@ func (s *Service) FindSimilarToQueueEntry(ctx context.Context, id uuid.UUID) ([]
 	return FindSimilar(target, candidates, 0.5), nil
 }

+// toContributions translates the crawler's per-source RawEvents into the
+// discovery-domain SourceContribution shape for JSONB persistence.
+func toContributions(raws []crawler.RawEvent) []SourceContribution {
+	out := make([]SourceContribution, 0, len(raws))
+	for _, r := range raws {
+		out = append(out, SourceContribution{
+			SourceName: r.SourceName,
+			SourceURL:  r.SourceURL,
+			DetailURL:  r.DetailURL,
+			Name:       r.Name,
+			City:       r.City,
+			PLZ:        r.PLZ,
+			Land:       r.Land,
+			Bundesland: r.Bundesland,
+			StartDate:  r.StartDate,
+			EndDate:    r.EndDate,
+			Website:    r.Website,
+			Venue:      r.Venue,
+			Organizer:  r.Organizer,
+		})
+	}
+	return out
+}
+
 // findSeriesMatch returns the ID of the first candidate whose normalized name matches
 // incomingName after normalization. Candidates are expected to be pre-filtered by city.
 func findSeriesMatch(incomingName string, candidates []SeriesCandidate) *uuid.UUID {
--- a/backend/internal/domain/discovery/service_test.go
+++ b/backend/internal/domain/discovery/service_test.go
@@ -340,6 +340,62 @@ func TestListPendingQueuePaged_ReturnsBothRowsAndTotal(t *testing.T) {
 	}
 }

+func TestServiceCrawlPersistsSourcesAndContributions(t *testing.T) {
+	repo := newMockRepo()
+	start := mustParseDate(t, "2026-05-01")
+
+	sc := &stubCrawlerRunner{
+		result: crawler.CrawlResult{
+			PerSource: map[string][]crawler.RawEvent{
+				"marktkalendarium": {
+					{SourceName: "marktkalendarium", SourceURL: "https://mk/", Name: "Markt X",
+						City: "Dresden", PLZ: "01067", StartDate: start, Website: "https://organizer.de"},
+				},
+				"mittelaltermarkt_online": {
+					{SourceName: "mittelaltermarkt_online", SourceURL: "https://mo/",
+						DetailURL: "https://mo/e/1", Name: "Markt X", City: "Dresden",
+						PLZ: "01067", StartDate: start, Venue: "Stallhof"},
+				},
+			},
+		},
+	}
+	svc := NewService(repo, sc, noopLinkVerifier{}, noopMarketCreator{})
+
+	if _, err := svc.Crawl(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+	if len(repo.inserted) != 1 {
+		t.Fatalf("inserted = %d; want 1 (merged from two sources)", len(repo.inserted))
+	}
+	got := repo.inserted[0]
+
+	// Sources list populated.
+	if len(got.Sources) != 2 {
+		t.Errorf("Sources = %v; want 2 entries", got.Sources)
+	}
+
+	// Contributions populated with both raws.
+	if len(got.SourceContributions) != 2 {
+		t.Fatalf("SourceContributions = %d; want 2", len(got.SourceContributions))
+	}
+	// First contribution should be the highest-rank source
+	// (mittelaltermarkt_online = rank 1, marktkalendarium = rank 2).
+	if got.SourceContributions[0].SourceName != "mittelaltermarkt_online" {
+		t.Errorf("first contribution source = %q; want mittelaltermarkt_online (rank 1)",
+			got.SourceContributions[0].SourceName)
+	}
+	// Each contribution preserves its source's original field values.
+	var seenVenue bool
+	for _, c := range got.SourceContributions {
+		if c.Venue == "Stallhof" {
+			seenVenue = true
+		}
+	}
+	if !seenVenue {
+		t.Error("expected Venue=Stallhof preserved in the mittelaltermarkt_online contribution")
+	}
+}
+
 func TestServiceCrawlMultiSourceHighKonfidenz(t *testing.T) {
 	repo := newMockRepo()
 	start := mustParseDate(t, "2026-05-01")
--- a/backend/migrations/000018_discovered_markets_sources_contributions.down.sql
+++ b/backend/migrations/000018_discovered_markets_sources_contributions.down.sql
@@ -0,0 +1,4 @@
+DROP INDEX IF EXISTS idx_discovered_markets_sources_gin;
+ALTER TABLE discovered_markets
+  DROP COLUMN IF EXISTS source_contributions,
+  DROP COLUMN IF EXISTS sources;
--- a/backend/migrations/000018_discovered_markets_sources_contributions.up.sql
+++ b/backend/migrations/000018_discovered_markets_sources_contributions.up.sql
@@ -0,0 +1,7 @@
+ALTER TABLE discovered_markets
+  ADD COLUMN sources text[] NOT NULL DEFAULT '{}',
+  ADD COLUMN source_contributions jsonb NOT NULL DEFAULT '[]'::jsonb;
+
+-- Helpful indexes for potential future filtering.
+CREATE INDEX IF NOT EXISTS idx_discovered_markets_sources_gin
+  ON discovered_markets USING GIN (sources);
--- a/web/src/routes/admin/discovery/+page.server.ts
+++ b/web/src/routes/admin/discovery/+page.server.ts
@@ -3,6 +3,22 @@ import { redirect, fail } from '@sveltejs/kit';
 import { serverFetch } from '$lib/api/client.server.js';
 import { ApiClientError } from '$lib/api/client.js';

+type SourceContribution = {
+	source_name: string;
+	source_url?: string;
+	detail_url?: string;
+	name?: string;
+	city?: string;
+	plz?: string;
+	land?: string;
+	bundesland?: string;
+	start_date?: string | null;
+	end_date?: string | null;
+	website?: string;
+	venue?: string;
+	organizer?: string;
+};
+
 type DiscoveredMarket = {
 	id: string;
 	markt_name: string;
@@ -13,6 +29,8 @@ type DiscoveredMarket = {
 	end_datum: string | null;
 	website: string;
 	quellen: string[];
+	sources: string[];
+	source_contributions: SourceContribution[];
 	konfidenz: string; // 'hoch' | 'mittel' | 'niedrig'
 	agent_status: string; // 'bestaetigt' | 'unklar' | 'vorjahr_unbestaetigt' | 'abgesagt'
 	hinweis: string;
--- a/web/src/routes/admin/discovery/+page.svelte
+++ b/web/src/routes/admin/discovery/+page.svelte
@@ -2,6 +2,7 @@
 	import { onMount } from 'svelte';
 	import { enhance } from '$app/forms';
 	import { goto } from '$app/navigation';
+	import ContributionsPanel from './ContributionsPanel.svelte';

 	let { data, form } = $props();

@@ -58,6 +59,12 @@
 	let similarLoading = $state(false);
 	let similarEntries = $state<SimilarEntry[]>([]);

+	// Quellen-Vergleich panel — one open at a time.
+	let quellenVergleichOpenId: string | null = $state(null);
+	function toggleQuellenVergleich(id: string) {
+		quellenVergleichOpenId = quellenVergleichOpenId === id ? null : id;
+	}
+
 	async function toggleSimilar(id: string) {
 		if (similarOpenId === id) {
 			similarOpenId = null;
@@ -454,6 +461,19 @@
 										{row.agent_status}
 									</span>
 								{/if}
+								{#if row.hinweis?.includes('date_conflict')}
+									<span
+										class="ml-1 inline-block rounded bg-amber-100 px-1.5 py-0.5 align-middle text-[10px] text-amber-700 dark:bg-amber-900/50 dark:text-amber-300"
+										title="Datumskonflikt zwischen Quellen"
+									>
+										⚠ Datumskonflikt
+									</span>
+								{/if}
+								{#if (row.sources?.length ?? 0) >= 2}
+									<div class="mt-0.5 text-[10px] font-normal text-stone-400 dark:text-stone-500">
+										merged: {row.sources.join(' + ')}
+									</div>
+								{/if}
 							</td>
 							<td class="py-3 pr-4">{row.stadt}</td>
 							<td class="py-3 pr-4 whitespace-nowrap">
@@ -515,6 +535,17 @@
 								>
 									Similar
 								</button>
+								{#if (row.sources?.length ?? 0) >= 2}
+									<button
+										type="button"
+										onclick={() => toggleQuellenVergleich(row.id)}
+										class="ml-1 rounded px-2 py-1 text-xs {quellenVergleichOpenId === row.id
+											? 'bg-amber-100 text-amber-700 dark:bg-amber-900/50 dark:text-amber-300'
+											: 'bg-stone-100 text-stone-600 hover:bg-stone-200 dark:bg-stone-800 dark:text-stone-300 dark:hover:bg-stone-700'}"
+									>
+										Quellen-Vergleich
+									</button>
+								{/if}
 							</td>
 						</tr>
 						{#if similarOpenId === row.id}
@@ -573,6 +604,21 @@
 								</td>
 							</tr>
 						{/if}
+						{#if quellenVergleichOpenId === row.id}
+							<tr
+								class="border-b border-stone-100 bg-amber-50/50 dark:border-stone-800 dark:bg-amber-950/20"
+							>
+								<td></td>
+								<td colspan="8" class="py-3 pr-4">
+									<div
+										class="text-xs font-medium tracking-wider text-amber-700 uppercase dark:text-amber-400"
+									>
+										Quellen-Vergleich
+									</div>
+									<ContributionsPanel contributions={row.source_contributions ?? []} />
+								</td>
+							</tr>
+						{/if}
 						{#if expandedId === row.id}
 							<tr
 								class="border-b border-stone-100 bg-stone-50 dark:border-stone-800 dark:bg-stone-900/50"
--- a/web/src/routes/admin/discovery/ContributionsPanel.svelte
+++ b/web/src/routes/admin/discovery/ContributionsPanel.svelte
@@ -0,0 +1,125 @@
+<script lang="ts">
+	type SourceContribution = {
+		source_name: string;
+		source_url?: string;
+		detail_url?: string;
+		name?: string;
+		city?: string;
+		plz?: string;
+		land?: string;
+		bundesland?: string;
+		start_date?: string | null;
+		end_date?: string | null;
+		website?: string;
+		venue?: string;
+		organizer?: string;
+	};
+
+	let { contributions }: { contributions: SourceContribution[] } = $props();
+
+	type FieldDef = {
+		label: string;
+		key: keyof SourceContribution;
+		format?: (v: string | null | undefined) => string;
+	};
+
+	const fields: FieldDef[] = [
+		{ label: 'Name', key: 'name' },
+		{ label: 'Stadt', key: 'city' },
+		{ label: 'PLZ', key: 'plz' },
+		{ label: 'Land', key: 'land' },
+		{ label: 'Bundesland', key: 'bundesland' },
+		{
+			label: 'Start-Datum',
+			key: 'start_date',
+			format: (v) => (v ? v.slice(0, 10) : '')
+		},
+		{
+			label: 'End-Datum',
+			key: 'end_date',
+			format: (v) => (v ? v.slice(0, 10) : '')
+		},
+		{ label: 'Website', key: 'website' },
+		{ label: 'Venue', key: 'venue' },
+		{ label: 'Veranstalter', key: 'organizer' }
+	];
+
+	// Returns the display value for a contribution field.
+	function cellValue(c: SourceContribution, field: FieldDef): string {
+		const raw = c[field.key] as string | null | undefined;
+		if (field.format) return field.format(raw);
+		return raw ?? '';
+	}
+
+	// A field has a conflict if at least two sources have non-empty, different values.
+	function hasConflict(field: FieldDef): boolean {
+		const values = contributions.map((c) => cellValue(c, field)).filter((v) => v !== '');
+		if (values.length < 2) return false;
+		return values.some((v) => v !== values[0]);
+	}
+</script>
+
+{#if contributions.length === 0}
+	<p class="mt-2 text-xs text-stone-400">Keine Quelldaten vorhanden.</p>
+{:else}
+	<div class="mt-2 overflow-x-auto">
+		<p class="mb-2 text-xs text-stone-500">
+			Rang 1 = höchste Priorität · Gewinnende Quelle:
+			<span class="font-mono font-medium text-stone-700 dark:text-stone-300"
+				>{contributions[0].source_name}</span
+			>
+			· Amber = abweichende Werte zwischen Quellen
+		</p>
+		<table class="w-full text-left text-xs">
+			<thead>
+				<tr
+					class="border-b border-amber-200 text-amber-700 dark:border-amber-800 dark:text-amber-400"
+				>
+					<th class="pr-4 pb-1 font-medium">Feld</th>
+					{#each contributions as c, i}
+						<th class="pr-4 pb-1 font-medium">
+							<span class="font-mono">{c.source_name}</span>
+							{#if i === 0}
+								<span
+									class="ml-1 rounded bg-amber-100 px-1 text-[10px] text-amber-700 dark:bg-amber-900/50 dark:text-amber-300"
+									>Rang 1</span
+								>
+							{/if}
+						</th>
+					{/each}
+				</tr>
+			</thead>
+			<tbody>
+				{#each fields as field}
+					{@const conflict = hasConflict(field)}
+					<tr
+						class="border-b border-amber-100 dark:border-amber-900 {conflict
+							? 'bg-amber-50 dark:bg-amber-950/30'
+							: ''}"
+					>
+						<td
+							class="py-1 pr-4 font-medium text-stone-500 dark:text-stone-400 {conflict
+								? 'text-amber-700 dark:text-amber-400'
+								: ''}"
+						>
+							{field.label}
+							{#if conflict}
+								<span title="Konflikt zwischen Quellen">⚠</span>
+							{/if}
+						</td>
+						{#each contributions as c}
+							{@const val = cellValue(c, field)}
+							<td class="py-1 pr-4 {conflict && val ? 'font-medium' : ''}">
+								{#if val}
+									{val}
+								{:else}
+									<span class="text-stone-300 dark:text-stone-600">—</span>
+								{/if}
+							</td>
+						{/each}
+					</tr>
+				{/each}
+			</tbody>
+		</table>
+	</div>
+{/if}