import Foundation

public protocol RDEPUBReaderPersistence: AnyObject {

    func loadLocation(for bookIdentifier: String) -> RDEPUBLocation?

    func saveLocation(_ location: RDEPUBLocation, for bookIdentifier: String)

    func loadBookmarks(for bookIdentifier: String) -> [RDEPUBBookmark]

    func saveBookmarks(_ bookmarks: [RDEPUBBookmark], for bookIdentifier: String)

    func loadHighlights(for bookIdentifier: String) -> [RDEPUBHighlight]

    func saveHighlights(_ highlights: [RDEPUBHighlight], for bookIdentifier: String)

    func loadReaderSettings() -> RDEPUBReaderSettings?

    func saveReaderSettings(_ settings: RDEPUBReaderSettings)
}

public extension RDEPUBReaderPersistence {
    func loadBookmarks(for bookIdentifier: String) -> [RDEPUBBookmark] {
        #if DEBUG
        print("[RDEPUBReaderPersistence] ⚠️ loadBookmarks called on default no-op implementation for: \(bookIdentifier)")
        #endif
        return []
    }

    func saveBookmarks(_ bookmarks: [RDEPUBBookmark], for bookIdentifier: String) {
        #if DEBUG
        print("[RDEPUBReaderPersistence] ⚠️ saveBookmarks(\(bookmarks.count) items) called on default no-op implementation for: \(bookIdentifier)")
        #endif
    }

    func loadReaderSettings() -> RDEPUBReaderSettings? {
        #if DEBUG
        print("[RDEPUBReaderPersistence] ⚠️ loadReaderSettings called on default no-op implementation")
        #endif
        return nil
    }

    func saveReaderSettings(_ settings: RDEPUBReaderSettings) {
        #if DEBUG
        print("[RDEPUBReaderPersistence] ⚠️ saveReaderSettings called on default no-op implementation")
        #endif
    }
}

public final class RDEPUBUserDefaultsPersistence: RDEPUBReaderPersistence {

    private let defaults: UserDefaults

    private let locationPrefix: String

    private let bookmarksPrefix: String

    private let highlightsPrefix: String

    private let settingsKey: String

    public init(
        defaults: UserDefaults = .standard,
        locationPrefix: String = "ssreader.epub.location.",
        bookmarksPrefix: String = "ssreader.epub.bookmarks.",
        highlightsPrefix: String = "ssreader.epub.highlights.",
        settingsKey: String = "ssreader.epub.settings"
    ) {
        self.defaults = defaults
        self.locationPrefix = locationPrefix
        self.bookmarksPrefix = bookmarksPrefix
        self.highlightsPrefix = highlightsPrefix
        self.settingsKey = settingsKey
    }

    public func loadLocation(for bookIdentifier: String) -> RDEPUBLocation? {
        guard let data = defaults.data(forKey: locationPrefix + bookIdentifier) else {
            return nil
        }
        return try? JSONDecoder().decode(RDEPUBLocation.self, from: data)
    }

    public func saveLocation(_ location: RDEPUBLocation, for bookIdentifier: String) {
        guard let data = try? JSONEncoder().encode(location) else {
            return
        }
        defaults.set(data, forKey: locationPrefix + bookIdentifier)
    }

    public func loadBookmarks(for bookIdentifier: String) -> [RDEPUBBookmark] {
        guard let data = defaults.data(forKey: bookmarksPrefix + bookIdentifier) else {
            return []
        }
        return (try? JSONDecoder().decode([RDEPUBBookmark].self, from: data)) ?? []
    }

    public func saveBookmarks(_ bookmarks: [RDEPUBBookmark], for bookIdentifier: String) {
        guard let data = try? JSONEncoder().encode(bookmarks) else {
            return
        }
        defaults.set(data, forKey: bookmarksPrefix + bookIdentifier)
    }

    public func loadHighlights(for bookIdentifier: String) -> [RDEPUBHighlight] {
        guard let data = defaults.data(forKey: highlightsPrefix + bookIdentifier) else {
            return []
        }
        return (try? JSONDecoder().decode([RDEPUBHighlight].self, from: data)) ?? []
    }

    public func saveHighlights(_ highlights: [RDEPUBHighlight], for bookIdentifier: String) {
        guard let data = try? JSONEncoder().encode(highlights) else {
            return
        }
        if data.count > 1_048_576 {
            #if DEBUG
            print("[RDEPUBUserDefaultsPersistence] ⚠️ saveHighlights data size (\(data.count) bytes) exceeds 1MB for: \(bookIdentifier)")
            #endif
        }
        defaults.set(data, forKey: highlightsPrefix + bookIdentifier)
    }

    public func loadReaderSettings() -> RDEPUBReaderSettings? {
        guard let data = defaults.data(forKey: settingsKey) else {
            return nil
        }
        return try? JSONDecoder().decode(RDEPUBReaderSettings.self, from: data)
    }

    public func saveReaderSettings(_ settings: RDEPUBReaderSettings) {
        guard let data = try? JSONEncoder().encode(settings) else {
            return
        }
        defaults.set(data, forKey: settingsKey)
    }
}