import Foundation
import Combine

/// 媒体库条目
struct LibraryItem: Identifiable, Codable, Equatable {
    let id: String
    var url: String
    var name: String
    var type: String          // "file", "url", "stream", "local"
    var lastPosition: Double  // 秒，上次播放位置
    var liked: Bool
    var disliked: Bool
    var tags: [String]
    var addedAt: Date
    var group: String?        // M3U group-title
    var logoURL: String?      // M3U tvg-logo
    
    init(id: String = UUID().uuidString, url: String, name: String,
         type: String = "url", lastPosition: Double = 0,
         liked: Bool = false, disliked: Bool = false,
         tags: [String] = [], group: String? = nil, logoURL: String? = nil) {
        self.id = id
        self.url = url
        self.name = name
        self.type = type
        self.lastPosition = lastPosition
        self.liked = liked
        self.disliked = disliked
        self.tags = tags
        self.addedAt = Date()
        self.group = group
        self.logoURL = logoURL
    }
    
    static func == (lhs: LibraryItem, rhs: LibraryItem) -> Bool { lhs.id == rhs.id }
}

/// 播放列表
struct LibraryPlaylist: Identifiable, Codable, Equatable {
    let id: String
    var name: String
    var itemIDs: [String]
    var createdAt: Date
    
    init(id: String = UUID().uuidString, name: String, itemIDs: [String] = []) {
        self.id = id
        self.name = name
        self.itemIDs = itemIDs
        self.createdAt = Date()
    }
    
    static func == (lhs: LibraryPlaylist, rhs: LibraryPlaylist) -> Bool { lhs.id == rhs.id }
}

/// 持久化结构
private struct LibraryStore: Codable {
    var items: [LibraryItem]
    var playlists: [LibraryPlaylist]
}

/// 媒体库管理器 — JSON文件持久化
@MainActor
final class MediaLibrary: ObservableObject {
    @Published var items: [LibraryItem] = []
    @Published var playlists: [LibraryPlaylist] = []
    
    private let filePath: URL
    
    // MARK: - 索引（O(1)查找）
    private var urlIndex: [String: String] = [:]   // url → itemID
    private var idIndex: [String: Int] = [:]        // itemID → array index
    
    init() {
        let appSupport = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
        let dir = appSupport.appendingPathComponent("MiniPlayer", isDirectory: true)
        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
        self.filePath = dir.appendingPathComponent("library.json")
        load()
    }
    
    // MARK: - 持久化
    
    private func load() {
        guard let data = try? Data(contentsOf: filePath),
              let store = try? JSONDecoder().decode(LibraryStore.self, from: data) else { return }
        items = store.items
        playlists = store.playlists
        rebuildIndexes()
    }
    
    /// 异步保存 — 不阻塞主线程，M3U几千条数据不卡UI
    private var saveTask: DispatchWorkItem?
    
    private func save() {
        // debounce: 合并连续save调用，只在500ms后真正写入
        saveTask?.cancel()
        let store = LibraryStore(items: items, playlists: playlists)
        let path = filePath
        let task = DispatchWorkItem {
            guard let data = try? JSONEncoder().encode(store) else { return }
            try? data.write(to: path, options: .atomic)
        }
        saveTask = task
        DispatchQueue.global(qos: .utility).asyncAfter(deadline: .now() + 0.5, execute: task)
    }
    
    /// 强制同步保存（退出时调用）
    func saveSync() {
        saveTask?.cancel()
        let store = LibraryStore(items: items, playlists: playlists)
        guard let data = try? JSONEncoder().encode(store) else { return }
        try? data.write(to: filePath, options: .atomic)
    }
    
    private func rebuildIndexes() {
        urlIndex.removeAll(keepingCapacity: true)
        idIndex.removeAll(keepingCapacity: true)
        for (i, item) in items.enumerated() {
            urlIndex[item.url] = item.id
            idIndex[item.id] = i
        }
    }
    
    // MARK: - 条目操作
    
    /// 添加单条，URL去重
    @discardableResult
    func addItem(url: String, name: String, type: String = "url",
                 group: String? = nil, logoURL: String? = nil) -> LibraryItem {
        if let existingID = urlIndex[url], let idx = idIndex[existingID] {
            return items[idx]
        }
        let item = LibraryItem(url: url, name: name, type: type, group: group, logoURL: logoURL)
        let newIndex = items.count
        items.append(item)
        urlIndex[item.url] = item.id
        idIndex[item.id] = newIndex
        save()
        return item
    }
    
    /// 批量添加（M3U导入），跳过已存在的URL，仅触发一次save
    func addItems(_ newItems: [LibraryItem]) -> Int {
        var count = 0
        for item in newItems {
            if urlIndex[item.url] == nil {
                let newIndex = items.count
                items.append(item)
                urlIndex[item.url] = item.id
                idIndex[item.id] = newIndex
                count += 1
            }
        }
        if count > 0 { save() }
        return count
    }
    
    func removeItem(_ id: String) {
        items.removeAll { $0.id == id }
        for i in playlists.indices {
            playlists[i].itemIDs.removeAll { $0 == id }
        }
        rebuildIndexes()
        save()
    }
    
    // MARK: - 喜欢 / 不喜欢
    
    func toggleLike(_ id: String) {
        guard let idx = idIndex[id] else { return }
        items[idx].liked.toggle()
        if items[idx].liked { items[idx].disliked = false }
        save()
    }
    
    func toggleDislike(_ id: String) {
        guard let idx = idIndex[id] else { return }
        items[idx].disliked.toggle()
        if items[idx].disliked { items[idx].liked = false }
        save()
    }
    
    // MARK: - 标签
    
    func addTag(_ tag: String, to id: String) {
        guard let idx = idIndex[id] else { return }
        let t = tag.trimmingCharacters(in: .whitespaces)
        guard !t.isEmpty, !items[idx].tags.contains(t) else { return }
        items[idx].tags.append(t)
        items[idx].tags.sort()
        save()
    }
    
    func removeTag(_ tag: String, from id: String) {
        guard let idx = idIndex[id] else { return }
        items[idx].tags.removeAll { $0 == tag }
        save()
    }
    
    /// 所有已使用的标签（去重+排序）
    var allTags: [String] {
        Array(Set(items.flatMap { $0.tags })).sorted()
    }
    
    // MARK: - 播放位置（节流：30秒内只保存一次）
    
    private var lastPositionSaveTime: Date = .distantPast
    
    func savePosition(_ itemID: String, position: Double) {
        guard let idx = idIndex[itemID] else { return }
        // 节流：距上次保存 < 30秒且位置差 < 5秒则跳过
        let now = Date()
        if now.timeIntervalSince(lastPositionSaveTime) < 30,
           abs(items[idx].lastPosition - position) < 5 {
            return
        }
        items[idx].lastPosition = position
        lastPositionSaveTime = now
        save()
    }
    
    /// 强制保存位置（退出时）
    func savePositionImmediate(_ itemID: String, position: Double) {
        guard let idx = idIndex[itemID] else { return }
        items[idx].lastPosition = position
        saveSync()
    }
    
    func getPosition(for itemID: String) -> Double {
        guard let idx = idIndex[itemID] else { return 0 }
        return items[idx].lastPosition
    }
    
    /// 按URL查找库条目 — O(1)
    func findItem(byURL url: String) -> LibraryItem? {
        guard let id = urlIndex[url], let idx = idIndex[id] else { return nil }
        return items[idx]
    }
    
    // MARK: - 播放列表
    
    func createPlaylist(name: String) -> LibraryPlaylist {
        let pl = LibraryPlaylist(name: name)
        playlists.append(pl)
        save()
        return pl
    }
    
    func deletePlaylist(_ id: String) {
        playlists.removeAll { $0.id == id }
        save()
    }
    
    func renamePlaylist(_ id: String, name: String) {
        guard let idx = playlists.firstIndex(where: { $0.id == id }) else { return }
        playlists[idx].name = name
        save()
    }
    
    func addToPlaylist(_ playlistID: String, itemID: String) {
        guard let idx = playlists.firstIndex(where: { $0.id == playlistID }) else { return }
        guard !playlists[idx].itemIDs.contains(itemID) else { return }
        playlists[idx].itemIDs.append(itemID)
        save()
    }
    
    func removeFromPlaylist(_ playlistID: String, itemID: String) {
        guard let idx = playlists.firstIndex(where: { $0.id == playlistID }) else { return }
        playlists[idx].itemIDs.removeAll { $0 == itemID }
        save()
    }
    
    func items(in playlistID: String) -> [LibraryItem] {
        guard let pl = playlists.first(where: { $0.id == playlistID }) else { return [] }
        return pl.itemIDs.compactMap { id in
            guard let idx = idIndex[id] else { return nil }
            return items[idx]
        }
    }
    
    // MARK: - 搜索（模糊查询）
    
    func search(_ text: String, tag: String? = nil, likedOnly: Bool = false) -> [LibraryItem] {
        items.filter { item in
            if likedOnly && !item.liked { return false }
            if let tag = tag, !item.tags.contains(tag) { return false }
            guard !text.isEmpty else { return true }
            let q = text.lowercased()
            return item.name.lowercased().contains(q)
                || item.url.lowercased().contains(q)
                || item.tags.contains(where: { $0.lowercased().contains(q) })
                || (item.group?.lowercased().contains(q) ?? false)
        }
    }
    
    // MARK: - 辅助
    
    var count: Int { items.count }
}