pageta-native/Sources/Features/RueckblickTabView.swift

import ManaAuthUI
import ManaCore
import ManaLLM
import SwiftUI

/// Lese-Rückblick: synthetisiert, was die Person WIRKLICH gelesen hat
/// (fertig oder substanziell gescrollt) — Tag/Woche/Gesamt. Pendant zur
/// Web-Route `/rueckblick`.
///
/// Architektur wie im Web: ein **deterministisches Gerüst** (Kennzahlen,
/// Themen, eigene Markierungen) steht IMMER — gratis, offline, ohne LLM.
/// Darüber eine **optionale Synthese** via `ManaLLM.generate` (lokal-first;
/// liefert sie nichts, bleibt das Gerüst nutzbar). Reine Auswahl-/Gruppier-/
/// Prompt-Logik in `Digest` (testbar, geteilt mit der Web-Konvention).
///
/// Motivations-Leitplanke (Wert 8): ruhiger Spiegel, keine Streaks/Belohnung.
struct RueckblickTabView: View {
	@Environment(AuthClient.self) private var auth
	@Environment(PendingShareSignal.self) private var shareSignal
	private var api: PagetaAPI { PagetaAPI(auth: auth) }

	@State private var articles: [Article] = []
	@State private var allHighlights: [HighlightWithArticle] = []
	@State private var loadState: LoadState = .idle
	@State private var scope: DigestScope = .week
	// Fenster-Bezugspunkt einmal pro Load festhalten.
	@State private var loadedAt = Date(timeIntervalSince1970: 0)

	@State private var synthesizing = false
	@State private var synthesis: String?
	@State private var synthesisError: String?
	@State private var synthesisInfo: String?

	enum LoadState: Equatable {
		case idle
		case loading
		case loaded
		case error(String)
	}

	// MARK: - Abgeleitetes Gerüst (rein, gratis)

	private var selected: [Article] {
		Digest.selectArticles(articles, scope: scope, now: loadedAt)
	}

	private func briefText(_ a: Article) -> String {
		if let ex = a.excerpt?.trimmingCharacters(in: .whitespacesAndNewlines), !ex.isEmpty {
			return ex
		}
		return String(a.content.prefix(280))
	}

	private var briefs: [DigestBrief] {
		selected.map { a in
			DigestBrief(
				id: a.id,
				title: a.displayTitle,
				source: a.siteName,
				url: a.id,
				brief: briefText(a),
				tags: a.tags
			)
		}
	}

	private var themeGroups: [ThemeGroup] { Digest.groupByTheme(briefs) }

	private var highlightLines: [DigestHighlightLine] {
		let ids = Set(selected.map(\.id))
		return allHighlights
			.filter { ids.contains($0.article.id) }
			.map {
				DigestHighlightLine(
					articleId: $0.article.id,
					source: $0.article.siteName,
					title: $0.article.displayTitle,
					text: $0.highlight.text,
					note: $0.highlight.note
				)
			}
	}

	private var highlightsByArticle: [(title: String, source: String?, lines: [DigestHighlightLine])] {
		var order: [String] = []
		var map: [String: (title: String, source: String?, lines: [DigestHighlightLine])] = [:]
		for h in highlightLines {
			if map[h.articleId] == nil {
				order.append(h.articleId)
				map[h.articleId] = (h.title, h.source, [])
			}
			map[h.articleId]?.lines.append(h)
		}
		return order.compactMap { map[$0] }
	}

	private var totalMinutes: Int {
		selected.reduce(0) { $0 + ($1.readingTimeMinutes ?? 0) }
	}

	private var sourceCount: Int {
		Set(selected.compactMap { $0.siteName?.lowercased() }.filter { !$0.isEmpty }).count
	}

	// MARK: - Body

	var body: some View {
		NavigationStack {
			Group {
				switch loadState {
				case .idle, .loading:
					ProgressView()
						.frame(maxWidth: .infinity, maxHeight: .infinity)
				case let .error(message):
					ContentUnavailableView(
						"Rückblick nicht verfügbar",
						systemImage: "exclamationmark.triangle",
						description: Text(message)
					)
				case .loaded:
					contentScroll
				}
			}
			.navigationTitle("Rückblick")
			.navigationDestination(for: String.self) { articleId in
				ArticleDetailView(articleId: articleId)
			}
			.paperBackground()
			.task {
				if loadState == .idle { await load() }
			}
			.onAppear {
				if loadState != .idle, loadState != .loading {
					Task { await load() }
				}
			}
			.refreshable { await load() }
			.onChange(of: shareSignal.flushedTick) { _, _ in
				Task { await load() }
			}
			.onChange(of: scope) { _, _ in resetSynthesis() }
		}
	}

	private var contentScroll: some View {
		ScrollView {
			VStack(alignment: .leading, spacing: 20) {
				Text("Was du gelesen hast — als ruhiger Spiegel, nicht als Punktestand.")
					.font(.subheadline)
					.foregroundStyle(.secondary)

				Picker("Zeitraum", selection: $scope) {
					ForEach(DigestScope.allCases) { s in
						Text(s.label).tag(s)
					}
				}
				.pickerStyle(.segmented)

				if selected.isEmpty {
					ContentUnavailableView(
						"Noch nichts gelesen",
						systemImage: "book.closed",
						description: Text(
							"In diesem Zeitraum hast du noch nichts (zu Ende) gelesen. Sobald du Artikel liest, erscheinen sie hier."
						)
					)
					.padding(.top, 24)
				} else {
					statsRow
					synthesisCard
					themesSection
					if !highlightsByArticle.isEmpty { highlightsSection }
				}
			}
			.padding(.horizontal, 20)
			.padding(.vertical, 16)
			.macReadingWidth()
		}
		.toolbar {
			if !selected.isEmpty {
				ShareLink(item: buildMarkdown()) {
					Image(systemName: "square.and.arrow.up")
				}
			}
		}
	}

	private var statsRow: some View {
		HStack(spacing: 18) {
			stat("\(selected.count)", "Artikel")
			stat("\(totalMinutes)", "Min")
			stat("\(sourceCount)", "Quellen")
			if !highlightLines.isEmpty {
				stat("\(highlightLines.count)", "Marker")
			}
		}
	}

	private func stat(_ value: String, _ label: String) -> some View {
		VStack(alignment: .leading, spacing: 2) {
			Text(value).font(.title3.weight(.semibold)).foregroundStyle(PagetaTheme.foreground)
			Text(label).font(.caption).foregroundStyle(.secondary)
		}
	}

	private var synthesisCard: some View {
		VStack(alignment: .leading, spacing: 10) {
			HStack {
				Text("Synthese")
					.font(.caption.weight(.semibold))
					.foregroundStyle(.secondary)
				Spacer()
				Button {
					Task { await synthesize() }
				} label: {
					Label(
						synthesizing ? "Erzeuge …" : (synthesis == nil ? "Synthese erzeugen" : "Neu erzeugen"),
						systemImage: "sparkles"
					)
					.font(.callout.weight(.medium))
				}
				.buttonStyle(.borderedProminent)
				.tint(PagetaTheme.primary)
				.disabled(synthesizing)
			}

			if synthesizing {
				Text("Läuft lokal auf deinem Gerät — das kann einen Moment dauern.")
					.font(.callout)
					.foregroundStyle(.secondary)
			} else if let synthesisError {
				Text(synthesisError)
					.font(.callout)
					.foregroundStyle(.orange)
					.fixedSize(horizontal: false, vertical: true)
			} else if let synthesis {
				Text(synthesis)
					.font(.callout)
					.foregroundStyle(PagetaTheme.foreground)
					.fixedSize(horizontal: false, vertical: true)
				if let synthesisInfo {
					Text(synthesisInfo).font(.caption2).foregroundStyle(.secondary)
				}
			} else {
				Text(
					"Überblick und rote Fäden über deine gelesenen Artikel — lokal erzeugt. Optional; das Gerüst unten steht auch ohne."
				)
				.font(.callout)
				.foregroundStyle(.secondary)
				.fixedSize(horizontal: false, vertical: true)
			}
		}
		.padding(14)
		.frame(maxWidth: .infinity, alignment: .leading)
		.background(PagetaTheme.surfaceHover, in: RoundedRectangle(cornerRadius: 12))
	}

	private var themesSection: some View {
		VStack(alignment: .leading, spacing: 14) {
			Text("Themen")
				.font(.caption.weight(.semibold))
				.foregroundStyle(.secondary)
			ForEach(themeGroups) { group in
				VStack(alignment: .leading, spacing: 4) {
					HStack(spacing: 6) {
						Text(group.theme).font(.headline)
						Text("· \(group.articles.count)").font(.subheadline).foregroundStyle(.secondary)
					}
					ForEach(group.articles) { brief in
						NavigationLink(value: brief.url) {
							HStack(alignment: .firstTextBaseline, spacing: 6) {
								Text(brief.title)
									.font(.callout)
									.foregroundStyle(PagetaTheme.foreground)
									.multilineTextAlignment(.leading)
								if let source = brief.source {
									Text("· \(source)").font(.caption).foregroundStyle(.secondary)
								}
								Spacer(minLength: 0)
							}
						}
						.buttonStyle(.plain)
					}
				}
			}
		}
	}

	private var highlightsSection: some View {
		VStack(alignment: .leading, spacing: 14) {
			Text("Deine Markierungen")
				.font(.caption.weight(.semibold))
				.foregroundStyle(.secondary)
			ForEach(Array(highlightsByArticle.enumerated()), id: \.offset) { _, group in
				VStack(alignment: .leading, spacing: 6) {
					HStack(spacing: 6) {
						Text(group.title).font(.subheadline.weight(.medium))
						if let source = group.source {
							Text("· \(source)").font(.caption).foregroundStyle(.secondary)
						}
					}
					ForEach(Array(group.lines.enumerated()), id: \.offset) { _, line in
						VStack(alignment: .leading, spacing: 2) {
							Text(line.text)
								.font(.callout)
								.italic()
								.foregroundStyle(PagetaTheme.foreground)
							if let note = line.note, !note.isEmpty {
								Text("— \(note)").font(.caption).foregroundStyle(.secondary)
							}
						}
						.padding(.leading, 10)
						.overlay(alignment: .leading) {
							Rectangle().fill(PagetaTheme.primary).frame(width: 2)
						}
					}
				}
			}
		}
	}

	// MARK: - Aktionen

	private func resetSynthesis() {
		synthesis = nil
		synthesisError = nil
		synthesisInfo = nil
	}

	private func load() async {
		loadState = .loading
		resetSynthesis()
		do {
			async let a = api.fetchArticles(limit: 500)
			async let h = api.fetchAllHighlights()
			articles = try await a
			allHighlights = try await h
			loadedAt = Date()
			loadState = .loaded
		} catch {
			loadState = .error(error.localizedDescription)
		}
	}

	private func synthesize() async {
		let currentBriefs = briefs
		let currentHighlights = highlightLines
		guard !currentBriefs.isEmpty, !synthesizing else { return }
		synthesizing = true
		resetSynthesis()
		let p = Digest.buildSynthesisPrompt(
			scope: scope,
			briefs: currentBriefs,
			highlights: currentHighlights
		)
		let result = await ManaLLM.generate(
			prompt: p.prompt,
			instructions: p.instructions,
			level: .creative,
			maxTokens: 700
		)
		let clean = result?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
		if clean.count >= 20 {
			synthesis = clean
			var parts: [String] = []
			if p.usedArticles < currentBriefs.count {
				parts.append("\(p.usedArticles) von \(currentBriefs.count) Artikeln")
			}
			if p.usedHighlights < currentHighlights.count {
				parts.append("\(p.usedHighlights) von \(currentHighlights.count) Markierungen")
			}
			synthesisInfo = parts.isEmpty ? nil : "Synthese aus \(parts.joined(separator: " und ")) — Rest gekürzt."
		} else {
			synthesisError =
				"Die lokale KI hat keine Synthese erzeugt — auf diesem Gerät ist eventuell kein Modell verfügbar. Das Gerüst unten steht unabhängig davon."
		}
		synthesizing = false
	}

	private func buildMarkdown() -> String {
		var lines: [String] = ["# Rückblick — \(scope.label)", ""]
		lines.append("\(selected.count) Artikel · \(totalMinutes) Min · \(sourceCount) Quellen")
		lines.append("")
		if let synthesis { lines.append(synthesis); lines.append("") }
		lines.append("## Gelesen (\(selected.count))")
		for a in selected {
			let src = a.siteName.map { " — \($0)" } ?? ""
			lines.append("- [\(a.displayTitle)](\(a.originalUrl))\(src)")
		}
		if !highlightsByArticle.isEmpty {
			lines.append("")
			lines.append("## Deine Markierungen")
			for group in highlightsByArticle {
				lines.append("")
				lines.append("**\(group.title)**")
				for line in group.lines {
					lines.append("> \(line.text)")
					if let note = line.note, !note.isEmpty { lines.append("> — \(note)") }
				}
			}
		}
		return lines.joined(separator: "\n")
	}
}