pageta-native/Sources/Core/EventSync/Reducers.swift

import Foundation
import ManaEventSync

// Reducer-Funktionen: replay über Events liefert den projezierten State.
// Swift-Spiegel der `emit`-Logik in `apps/web/src/lib/event-sync-api.ts`
// — was dort als Event-Type emittiert wird, muss hier reduziert werden.
//
// Reducer sind idempotent gegen Replay: gleicher Event-Stream → gleicher
// State. Bei unbekanntem eventType wird übersprungen statt Crash
// (Forward-Kompatibilität).

enum Reducers {
	// MARK: - Article

	static func replayArticle(_ events: [EventEnvelope]) -> ArticleState? {
		guard !events.isEmpty else { return nil }
		var state = ArticleState.initial()
		for event in events {
			state = applyArticle(state, event)
		}
		// Vor ArticleSaved existiert das Aggregat semantisch nicht.
		return state.id.isEmpty ? nil : state
	}

	private static func applyArticle(
		_ state: ArticleState,
		_ event: EventEnvelope
	) -> ArticleState {
		var s = state
		switch event.eventType {
		case EventType.articleSaved:
			guard let p = try? event.payload.decode(ArticleSavedPayload.self) else { return s }
			s.id = p.articleId
			s.userId = event.attributedToUserId
			s.originalUrl = p.originalUrl
			s.urlHash = p.urlHash
			s.title = p.title
			s.excerpt = p.excerpt
			s.content = p.content
			s.author = p.author
			s.siteName = p.siteName
			s.imageUrl = p.imageUrl
			s.wordCount = p.wordCount
			s.readingTimeMinutes = p.readingTimeMinutes
			s.publishedAt = p.publishedAt
			s.status = .unread
			s.readingProgress = 0
			s.isFavorite = false
			s.userNote = p.userNote
			s.tags = []
			s.savedAt = event.occurredAt
			s.readAt = nil
			s.deletedAt = nil
			s.warning = nil

		case EventType.articleEnriched:
			// Deferred extraction: füllt Inhalt/Metadaten nach. Bewusst
			// non-destruktiv — Status/Progress/Favorit/Note/Tags/savedAt
			// bleiben, wie der User sie zwischenzeitlich gesetzt hat.
			guard let p = try? event.payload.decode(ArticleEnrichedPayload.self) else { return s }
			s.title = p.title
			s.excerpt = p.excerpt
			s.content = p.content
			s.author = p.author
			s.siteName = p.siteName
			s.imageUrl = p.imageUrl
			s.wordCount = p.wordCount
			s.readingTimeMinutes = p.readingTimeMinutes
			s.publishedAt = p.publishedAt
			if let warning = p.warning { s.warning = warning }

		case EventType.articleStatusChanged:
			guard let p = try? event.payload.decode(ArticleStatusChangedPayload.self)
			else { return s }
			s.status = p.newStatus
			if p.newStatus == .finished, s.readAt == nil {
				s.readAt = event.occurredAt
			}

		case EventType.articleProgressUpdated:
			guard let p = try? event.payload.decode(ArticleProgressUpdatedPayload.self)
			else { return s }
			s.readingProgress = p.newProgress

		case EventType.articleFavoriteToggled:
			guard let p = try? event.payload.decode(ArticleFavoriteToggledPayload.self)
			else { return s }
			s.isFavorite = p.isFavorite

		case EventType.articleNoteUpdated:
			guard let p = try? event.payload.decode(ArticleNoteUpdatedPayload.self)
			else { return s }
			s.userNote = p.newNote

		case EventType.articleTagsSet:
			guard let p = try? event.payload.decode(ArticleTagsSetPayload.self) else { return s }
			s.tags = p.tags

		case EventType.articleWarningFlagged:
			guard let p = try? event.payload.decode(ArticleWarningFlaggedPayload.self)
			else { return s }
			s.warning = p.warning

		case EventType.articleWarningCleared:
			s.warning = nil

		case EventType.articleDeleted:
			s.deletedAt = event.occurredAt

		default:
			// Unbekannter Event-Type: skippen.
			break
		}
		return s
	}

	// MARK: - Highlight

	static func replayHighlight(_ events: [EventEnvelope]) -> HighlightEventState? {
		guard !events.isEmpty else { return nil }
		var state = HighlightEventState.initial()
		for event in events {
			state = applyHighlight(state, event)
		}
		return state.id.isEmpty ? nil : state
	}

	private static func applyHighlight(
		_ state: HighlightEventState,
		_ event: EventEnvelope
	) -> HighlightEventState {
		var s = state
		switch event.eventType {
		case EventType.highlightCreated:
			guard let p = try? event.payload.decode(HighlightCreatedPayload.self) else { return s }
			s.id = p.highlightId
			s.userId = event.attributedToUserId
			s.articleId = p.articleId
			s.text = p.text
			s.note = p.note
			s.color = p.color
			s.startOffset = p.startOffset
			s.endOffset = p.endOffset
			s.contextBefore = p.contextBefore
			s.contextAfter = p.contextAfter
			s.createdAt = event.occurredAt
			s.deletedAt = nil

		case EventType.highlightNoteUpdated:
			guard let p = try? event.payload.decode(HighlightNoteUpdatedPayload.self)
			else { return s }
			s.note = p.newNote

		case EventType.highlightColorChanged:
			guard let p = try? event.payload.decode(HighlightColorChangedPayload.self)
			else { return s }
			s.color = p.newColor

		case EventType.highlightDeleted:
			s.deletedAt = event.occurredAt

		default:
			break
		}
		return s
	}
}