Sapling/Sources/SaplingEditor/DocumentSessionStore.swift

import Foundation
import SaplingCore

@MainActor
public final class MarkdownDocumentSession: Identifiable, ObservableObject {
    public let id: UUID
    public let documentURL: URL
    public let viewModel: HybridMarkdownEditorViewModel

    public init(
        id: UUID = UUID(),
        documentURL: URL,
        viewModel: HybridMarkdownEditorViewModel
    ) {
        self.id = id
        self.documentURL = documentURL
        self.viewModel = viewModel
    }
}

@MainActor
public final class DocumentSessionStore: ObservableObject {
    @Published public private(set) var sessions: [MarkdownDocumentSession]
    @Published public private(set) var activeSession: MarkdownDocumentSession?

    public init(sessions: [MarkdownDocumentSession] = []) {
        self.sessions = sessions
        self.activeSession = sessions.first
    }

    @discardableResult
    public func openDocument(
        at url: URL,
        loadDocument: @MainActor (URL) throws -> MarkdownDocument = HybridMarkdownEditorViewModel.loadDocument(at:)
    ) throws -> MarkdownDocumentSession {
        let key = sessionKey(for: url)
        if let existingSession = sessions.first(where: { sessionKey(for: $0.documentURL) == key }) {
            activeSession = existingSession
            return existingSession
        }

        let document = try loadDocument(url)
        let session = MarkdownDocumentSession(
            documentURL: url,
            viewModel: HybridMarkdownEditorViewModel(document: document)
        )
        sessions.append(session)
        activeSession = session
        return session
    }

    @discardableResult
    public func activateDocument(at url: URL) -> Bool {
        let key = sessionKey(for: url)
        guard let session = sessions.first(where: { sessionKey(for: $0.documentURL) == key }) else {
            return false
        }

        activeSession = session
        return true
    }

    public func updateActiveSessionFromViewModel() {
        guard let activeSession else { return }
        objectWillChange.send()
        activeSession.objectWillChange.send()
    }

    private func sessionKey(for url: URL) -> String {
        url.standardizedFileURL.path
    }
}