import Foundation

public struct UsageCache {
    public static let cacheURL: URL = {
        let dir = FileManager.default.homeDirectoryForCurrentUser.appendingPathComponent(".config/usage-tray", isDirectory: true)
        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
        return dir.appendingPathComponent("cache.json")
    }()

    private static var inMemoryCache: [String: ProviderUsage]? = nil

    public static func load() -> [String: ProviderUsage] {
        if let cached = inMemoryCache { return cached }
        guard let data = try? Data(contentsOf: cacheURL),
              let dict = try? JSONDecoder().decode([String: ProviderUsage].self, from: data) else {
            inMemoryCache = [:]
            return [:]
        }
        inMemoryCache = dict
        return dict
    }

    public static func save(providers: [ProviderUsage]) {
        var dict = load()
        var changed = false
        for p in providers where !p.windows.isEmpty || p.balance != nil {
            if dict[p.id] != p {
                dict[p.id] = p
                changed = true
            }
        }
        guard changed else { return }
        inMemoryCache = dict
        if let data = try? JSONEncoder().encode(dict) {
            try? data.write(to: cacheURL, options: .atomic)
        }
    }
}