import SwiftUI

struct DMListView: View {
	@Environment(APIClient.self) private var api
	@Environment(MeshDataStore.self) private var store

	@State private var conversations: [DMConversation] = []
	@State private var loading = false
	@State private var error: String?

	var body: some View {
		Group {
			if loading && conversations.isEmpty {
				ProgressView("Loading conversations…")
			} else if let error, conversations.isEmpty {
				ContentUnavailableView {
					Label("Error", systemImage: "exclamationmark.triangle")
				} description: {
					Text(error)
				} actions: {
					Button("Retry") { Task { await load() } }
				}
			} else if conversations.isEmpty {
				ContentUnavailableView("No direct messages",
									   systemImage: "bubble.left.and.bubble.right")
			} else {
				List(conversations) { conv in
					NavigationLink {
						ChatView(target: .dm(nodeId: conv.nodeId, name: conv.displayName))
					} label: {
						DMRow(conversation: conv)
					}
				}
			}
		}
		.navigationTitle("Direct Messages")
		.toolbar {
			ToolbarItem(placement: .topBarTrailing) {
				Button {
					Task { await load() }
				} label: {
					Image(systemName: "arrow.clockwise")
				}
				.disabled(loading)
			}
		}
		.refreshable { await load() }
		.task { await load() }
	}

	@MainActor
	private func load() async {
		loading = true
		defer { loading = false }
		error = nil
		if store.nodes.isEmpty || store.localNodeId == nil {
			await store.refresh(api: api)
		}
		do {
			let msgs = try await api.fetchAllMessages(limit: 200)
			conversations = Self.extractConversations(
				from: msgs,
				localNodeId: store.localNodeId,
				nodeNames: store.nodeNames
			)
		} catch {
			self.error = error.localizedDescription
		}
	}

	static func extractConversations(from messages: [Message],
									  localNodeId: String?,
									  nodeNames: [String: String]) -> [DMConversation] {
		var byNode: [String: Message] = [:]
		for msg in messages where msg.channel == -1 && msg.isText && !msg.isReaction {
			let from = msg.fromNodeId
			let to = msg.toNodeId
			let partner: String?
			if let local = localNodeId {
				if from == local { partner = to }
				else if to == local { partner = from }
				else { partner = from }
			} else {
				partner = from
			}
			guard let p = partner, p != "broadcast", p != localNodeId else { continue }
			if let existing = byNode[p] {
				if msg.timestamp > existing.timestamp { byNode[p] = msg }
			} else {
				byNode[p] = msg
			}
		}
		return byNode.map { (id, msg) in
			DMConversation(
				nodeId: id,
				displayName: nodeNames[id] ?? id,
				lastMessage: msg.text ?? "",
				lastTimestamp: msg.timestamp
			)
		}.sorted { $0.lastTimestamp > $1.lastTimestamp }
	}
}

struct DMConversation: Identifiable, Hashable {
	let nodeId: String
	let displayName: String
	let lastMessage: String
	let lastTimestamp: Date
	var id: String { nodeId }
}

private struct DMRow: View {
	let conversation: DMConversation

	private static let timeFmt: DateFormatter = {
		let f = DateFormatter()
		f.dateStyle = .none
		f.timeStyle = .short
		return f
	}()

	var body: some View {
		HStack(spacing: 10) {
			Image(systemName: "person.circle.fill")
				.font(.title2)
				.foregroundStyle(.tint)
			VStack(alignment: .leading, spacing: 2) {
				HStack {
					Text(conversation.displayName).font(.body)
					Spacer()
					Text(Self.timeFmt.string(from: conversation.lastTimestamp))
						.font(.caption2).foregroundStyle(.secondary)
				}
				Text(conversation.lastMessage)
					.font(.caption)
					.foregroundStyle(.secondary)
					.lineLimit(1)
			}
		}
		.padding(.vertical, 2)
	}
}