import Foundation

/// The text of the Notitie editor, kept in one plain file. Saves are debounced and atomic.
@MainActor
public final class NoteStore: ObservableObject {
    @Published public var text: String = "" {
        didSet {
            guard text != oldValue, !loading else { return }
            changed()
        }
    }
    public private(set) var lastError: String?
    /// True when the file exists but could not be read: saving would overwrite the user's text, so it is switched off.
    public private(set) var isReadOnly = false

    private let fileURL: URL
    private var saveTask: Task<Void, Never>?
    private var loading = false

    public init(fileURL: URL) {
        self.fileURL = fileURL
    }

    public func load() {
        guard FileManager.default.fileExists(atPath: fileURL.path) else { return }
        loading = true
        defer { loading = false }
        do {
            text = try String(contentsOf: fileURL, encoding: .utf8)
        } catch {
            isReadOnly = true
            lastError = error.localizedDescription
        }
    }

    /// Writes immediately (also call this when the app quits).
    public func flush() {
        saveTask?.cancel()
        saveTask = nil
        guard !isReadOnly else { return }
        do {
            try FileManager.default.createDirectory(
                at: fileURL.deletingLastPathComponent(), withIntermediateDirectories: true)
            try text.write(to: fileURL, atomically: true, encoding: .utf8)
            lastError = nil
        } catch {
            lastError = error.localizedDescription
        }
    }

    private func changed() {
        saveTask?.cancel()
        saveTask = Task { [weak self] in
            try? await Task.sleep(for: .milliseconds(400))
            guard !Task.isCancelled else { return }
            self?.flush()
        }
    }
}

/// Puts a space between dictations: the text before the cursor decides whether one is needed.
public enum DictationSpacing {
    public static func prepared(_ text: String, characterBefore: Character?) -> String {
        guard let before = characterBefore, !before.isWhitespace, let first = text.first else { return text }
        if first.isWhitespace || ".,;:!?)]}\u{201D}\u{2019}".contains(first) { return text }
        return " " + text
    }
}