//
//  DataStateManager.swift

import Foundation

/// Manages the overall data state timestamp for sync purposes. This tracks when any data in the
/// local database was last modified, independent of individual entity timestamps.
class DataStateManager {

    private let userDefaults = UserDefaults.standard

    private enum Keys {
        static let lastModified = "openclimb_data_last_modified"
        static let initialized = "openclimb_data_state_initialized"
    }

    /// Shared instance for app-wide use
    static let shared = DataStateManager()

    private init() {
        // Initialize with current timestamp if this is the first time
        if !isInitialized() {
            print("DataStateManager: First time initialization")
            // Set initial timestamp to a very old date so server data will be considered newer
            let epochTime = "1970-01-01T00:00:00.000Z"
            userDefaults.set(epochTime, forKey: Keys.lastModified)
            markAsInitialized()
            print("DataStateManager initialized with epoch timestamp: \(epochTime)")
        } else {
            print("DataStateManager: Already initialized, current timestamp: \(getLastModified())")
        }
    }

    /// Updates the data state timestamp to the current time. Call this whenever any data is modified
    /// (create, update, delete).
    func updateDataState() {
        let now = ISO8601DateFormatter().string(from: Date())
        userDefaults.set(now, forKey: Keys.lastModified)
        print("📝 iOS Data state updated to: \(now)")
    }

    /// Gets the current data state timestamp. This represents when any data was last modified
    /// locally.
    func getLastModified() -> String {
        if let storedTimestamp = userDefaults.string(forKey: Keys.lastModified) {
            print("📅 iOS DataStateManager returning stored timestamp: \(storedTimestamp)")
            return storedTimestamp
        }

        // If no timestamp is stored, return epoch time to indicate very old data
        // This ensures server data will be considered newer than uninitialized local data
        let epochTime = "1970-01-01T00:00:00.000Z"
        print("⚠️ No data state timestamp found - returning epoch time: \(epochTime)")
        return epochTime
    }

    /// Sets the data state timestamp to a specific value. Used when importing data from server to
    /// sync the state.
    func setLastModified(_ timestamp: String) {
        userDefaults.set(timestamp, forKey: Keys.lastModified)
        print("Data state set to: \(timestamp)")
    }

    /// Resets the data state (for testing or complete data wipe).
    func reset() {
        userDefaults.removeObject(forKey: Keys.lastModified)
        userDefaults.removeObject(forKey: Keys.initialized)
        print("Data state reset")
    }

    /// Checks if the data state has been initialized.
    private func isInitialized() -> Bool {
        return userDefaults.bool(forKey: Keys.initialized)
    }

    /// Marks the data state as initialized.
    private func markAsInitialized() {
        userDefaults.set(true, forKey: Keys.initialized)
    }

    /// Gets debug information about the current state.
    func getDebugInfo() -> String {
        return "DataState(lastModified=\(getLastModified()), initialized=\(isInitialized()))"
    }
}