import SwiftUI
import UIKit

// MARK: - Image Cache (Memory + Disk)

/// Two-tier image cache: NSCache for fast memory access, disk for persistence across launches.
class ImageCache {
    static let shared = ImageCache()
    
    private let memoryCache = NSCache<NSString, UIImage>()
    private let fileManager = FileManager.default
    private let diskCacheURL: URL
    private let ioQueue = DispatchQueue(label: "com.navidromeplayer.imagecache", qos: .utility)
    
    /// Max memory cache: ~80 images
    /// Max disk cache: 200 MB
    private let maxDiskBytes: UInt64 = 200 * 1024 * 1024
    
    private init() {
        let caches = fileManager.urls(for: .cachesDirectory, in: .userDomainMask).first!
        diskCacheURL = caches.appendingPathComponent("ImageCache", isDirectory: true)
        try? fileManager.createDirectory(at: diskCacheURL, withIntermediateDirectories: true)
        try? (diskCacheURL as NSURL).setResourceValue(
            URLFileProtection.completeUntilFirstUserAuthentication,
            forKey: .fileProtectionKey
        )
        
        memoryCache.countLimit = 80
        memoryCache.totalCostLimit = 50 * 1024 * 1024 // ~50 MB
    }
    
    // MARK: - Key Hashing
    
    private func cacheKey(for url: URL) -> String {
        // Use endpoint + query params only (not the server base URL)
        // so the same cover art ID caches the same regardless of local vs public server
        let components = URLComponents(url: url, resolvingAgainstBaseURL: false)
        let path = components?.path ?? ""
        // Extract just the endpoint name and relevant params (id, size)
        let endpoint = (path as NSString).lastPathComponent
        let params = (components?.queryItems ?? [])
            .filter { ["id", "size"].contains($0.name) }
            .sorted { $0.name < $1.name }
            .map { "\($0.name)=\($0.value ?? "")" }
            .joined(separator: "&")
        let keyStr = "\(endpoint)?\(params)"
        let hash = keyStr.utf8.reduce(0) { ($0 &* 31) &+ UInt64($1) }
        return String(hash, radix: 16)
    }
    
    // MARK: - Memory Cache
    
    func memoryImage(for url: URL) -> UIImage? {
        let key = cacheKey(for: url) as NSString
        return memoryCache.object(forKey: key)
    }
    
    func storeInMemory(_ image: UIImage, for url: URL) {
        let key = cacheKey(for: url) as NSString
        let cost = Int(image.size.width * image.size.height * image.scale * 4)
        memoryCache.setObject(image, forKey: key, cost: cost)
    }
    
    // MARK: - Disk Cache
    
    private func diskURL(for url: URL) -> URL {
        diskCacheURL.appendingPathComponent(cacheKey(for: url) + ".jpg")
    }
    
    func diskImage(for url: URL) -> UIImage? {
        let path = diskURL(for: url)
        guard let data = try? Data(contentsOf: path) else { return nil }
        return UIImage(data: data)
    }
    
    func storeToDisk(_ image: UIImage, for url: URL) {
        ioQueue.async { [weak self] in
            guard let self = self else { return }
            let path = self.diskURL(for: url)
            // JPEG at 85% quality for good size/quality balance
            if let data = image.jpegData(compressionQuality: 0.85) {
                try? data.write(to: path, options: .atomic)
            }
        }
    }
    
    // MARK: - Combined Lookup

    /// Synchronous memory-only check — safe to call from any thread.
    /// Returns nil if not in memory (does NOT hit disk).
    func memoryOnlyImage(for url: URL) -> UIImage? {
        memoryImage(for: url)
    }

    /// Returns cached image from memory first, then disk (async, off main thread).
    /// Promotes disk hits to memory. Use this from async contexts.
    func cachedImageAsync(for url: URL) async -> UIImage? {
        // 1. Memory — no I/O, safe on any thread
        if let img = memoryImage(for: url) { return img }
        // 2. Disk — on ioQueue to keep main thread free
        return await withCheckedContinuation { continuation in
            ioQueue.async {
                if let img = self.diskImage(for: url) {
                    self.storeInMemory(img, for: url)
                    continuation.resume(returning: img)
                } else {
                    continuation.resume(returning: nil)
                }
            }
        }
    }

    /// Synchronous combined lookup — only call from background threads.
    /// For main-thread callers, prefer memoryOnlyImage + cachedImageAsync.
    func cachedImage(for url: URL) -> UIImage? {
        // 1. Memory
        if let img = memoryImage(for: url) {
            return img
        }
        // 2. Disk -> promote to memory
        if let img = diskImage(for: url) {
            storeInMemory(img, for: url)
            return img
        }
        return nil
    }
    
    /// Stores image in both memory and disk.
    func store(_ image: UIImage, for url: URL) {
        storeInMemory(image, for: url)
        storeToDisk(image, for: url)
    }
    
    // MARK: - Cleanup
    
    /// Trims disk cache to maxDiskBytes. Call periodically or on app launch.
    func trimDiskCache() {
        ioQueue.async { [weak self] in
            guard let self = self else { return }
            guard let files = try? self.fileManager.contentsOfDirectory(
                at: self.diskCacheURL,
                includingPropertiesForKeys: [.contentModificationDateKey, .fileSizeKey]
            ) else { return }
            
            // Get file info
            var fileInfos: [(url: URL, date: Date, size: UInt64)] = []
            var totalSize: UInt64 = 0
            
            for file in files {
                guard let attrs = try? file.resourceValues(forKeys: [.contentModificationDateKey, .fileSizeKey]),
                      let date = attrs.contentModificationDate,
                      let size = attrs.fileSize else { continue }
                let s = UInt64(size)
                fileInfos.append((file, date, s))
                totalSize += s
            }
            
            guard totalSize > self.maxDiskBytes else { return }
            
            // Sort oldest first, delete until under limit
            fileInfos.sort { $0.date < $1.date }
            for info in fileInfos {
                guard totalSize > self.maxDiskBytes else { break }
                try? self.fileManager.removeItem(at: info.url)
                totalSize -= info.size
            }
        }
    }
    
    /// Clears all cached images
    func clearAll() {
        memoryCache.removeAllObjects()
        ioQueue.async { [weak self] in
            guard let self = self else { return }
            if let files = try? self.fileManager.contentsOfDirectory(at: self.diskCacheURL, includingPropertiesForKeys: nil) {
                for file in files {
                    try? self.fileManager.removeItem(at: file)
                }
            }
        }
    }
}

// MARK: - Album Cover Store (custom covers, disk-persisted)

/// Stores user-set album cover art on disk, keyed by coverArtId.
/// Custom covers override server art everywhere (AlbumDetail, NowPlaying, MiniPlayer, grids).
class AlbumCoverStore: ObservableObject {
    static let shared = AlbumCoverStore()
    
    /// Triggers SwiftUI refresh when a cover changes
    @Published var updateTrigger = UUID()
    
    private let fileManager = FileManager.default
    private let coverDir: URL
    
    private init() {
        let docs = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first!
        coverDir = docs.appendingPathComponent("AlbumCovers", isDirectory: true)
        try? fileManager.createDirectory(at: coverDir, withIntermediateDirectories: true)
    }
    
    private func coverURL(for coverArtId: String) -> URL {
        // Sanitize the ID for filesystem safety
        let safe = coverArtId.replacingOccurrences(of: "/", with: "_")
        return coverDir.appendingPathComponent("\(safe).jpg")
    }
    
    func hasCover(for coverArtId: String) -> Bool {
        fileManager.fileExists(atPath: coverURL(for: coverArtId).path)
    }
    
    func loadCover(for coverArtId: String) -> UIImage? {
        let url = coverURL(for: coverArtId)
        guard let data = try? Data(contentsOf: url) else { return nil }
        return UIImage(data: data)
    }
    
    func saveCover(_ image: UIImage, for coverArtId: String) {
        let url = coverURL(for: coverArtId)
        if let data = image.jpegData(compressionQuality: 0.85) {
            try? data.write(to: url, options: .atomic)
            DispatchQueue.main.async { self.updateTrigger = UUID() }
        }
    }
    
    func removeCover(for coverArtId: String) {
        let url = coverURL(for: coverArtId)
        try? fileManager.removeItem(at: url)
        DispatchQueue.main.async { self.updateTrigger = UUID() }
    }
}

// MARK: - Artist Cover Store (custom artist photos)

class ArtistCoverStore: ObservableObject {
    static let shared = ArtistCoverStore()
    
    @Published var updateTrigger = UUID()
    
    private let fileManager = FileManager.default
    private let coverDir: URL
    
    private init() {
        let docs = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first!
        coverDir = docs.appendingPathComponent("ArtistCovers", isDirectory: true)
        try? fileManager.createDirectory(at: coverDir, withIntermediateDirectories: true)
    }
    
    private func coverURL(for artistId: String) -> URL {
        let safe = artistId.replacingOccurrences(of: "/", with: "_")
        return coverDir.appendingPathComponent("\(safe).jpg")
    }
    
    func hasCover(for artistId: String) -> Bool {
        fileManager.fileExists(atPath: coverURL(for: artistId).path)
    }
    
    func loadCover(for artistId: String) -> UIImage? {
        let url = coverURL(for: artistId)
        guard let data = try? Data(contentsOf: url) else { return nil }
        return UIImage(data: data)
    }
    
    func saveCover(_ image: UIImage, for artistId: String) {
        let url = coverURL(for: artistId)
        if let data = image.jpegData(compressionQuality: 0.85) {
            try? data.write(to: url, options: .atomic)
            DispatchQueue.main.async { self.updateTrigger = UUID() }
        }
    }
    
    func removeCover(for artistId: String) {
        let url = coverURL(for: artistId)
        try? fileManager.removeItem(at: url)
        DispatchQueue.main.async { self.updateTrigger = UUID() }
    }
}

// MARK: - Cached Image Loader (ObservableObject per-view)

class CachedImageLoader: ObservableObject {
    @Published var image: UIImage?
    @Published var isLoading = false
    
    private var url: URL?
    private var task: URLSessionDataTask?
    
    func load(from url: URL) {
        // Skip if already loaded this URL
        guard self.url != url else { return }
        self.url = url

        // 1. Memory hit — instant, no I/O
        if let cached = ImageCache.shared.memoryOnlyImage(for: url) {
            self.image = cached
            return
        }

        // 2. Async check (disk → network) — never blocks main thread
        isLoading = true
        task?.cancel()
        Task { @MainActor in
            // Check disk off main thread
            if let cached = await ImageCache.shared.cachedImageAsync(for: url) {
                self.image = cached
                self.isLoading = false
                return
            }
            // Network fetch
            do {
                let (data, _) = try await URLSession.shared.data(from: url)
                guard let img = UIImage(data: data) else {
                    self.isLoading = false
                    return
                }
                ImageCache.shared.store(img, for: url)
                self.image = img
                self.isLoading = false
            } catch {
                self.isLoading = false
            }
        }
    }
    
    func cancel() {
        task?.cancel()
        task = nil
    }
}

// MARK: - CachedAsyncImage View

struct CachedAsyncImage: View {
    let url: URL?
    
    @StateObject private var loader = CachedImageLoader()
    
    var body: some View {
        Group {
            if let img = loader.image {
                Image(uiImage: img)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
            } else {
                Color.clear // placeholder handled by caller
            }
        }
        .onAppear {
            if let url = url {
                loader.load(from: url)
            }
        }
        .onChange(of: url) { _, newURL in
            if let newURL = newURL {
                loader.load(from: newURL)
            }
        }
        .onDisappear {
            loader.cancel()
        }
    }
}

// MARK: - AsyncCoverArt (drop-in replacement, now cached)

struct AsyncCoverArt: View {
    let coverArtId: String?
    let size: Int

    @ObservedObject private var albumCoverStore = AlbumCoverStore.shared

    var body: some View {
        if let id = coverArtId {
            // Custom user-set cover takes priority everywhere
            if let customImage = albumCoverStore.loadCover(for: id) {
                let _ = albumCoverStore.updateTrigger
                Image(uiImage: customImage)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .clipped()
            } else if id.hasPrefix("companion:") {
                // Route to Companion API cover art endpoint.
                // Use a shared service instance — creating CompanionAPIService() per render
                // allocates a new URLSession each time, causing connection pool exhaustion.
                let companionId = String(id.dropFirst("companion:".count))
                if let url = CompanionSettings.shared.baseURL?
                    .appendingPathComponent("library/cover-art/\(companionId)") {
                    ZStack {
                        placeholderView
                        CachedAsyncImage(url: url)
                    }
                    .clipped()
                } else {
                    placeholderView
                }
            } else if let url = ServerManager.shared.client.coverArtURL(id: id, size: size) {
                ZStack {
                    placeholderView
                    CachedAsyncImage(url: url)
                }
                .clipped()
            } else {
                placeholderView
            }
        } else {
            placeholderView
        }
    }

    private var placeholderView: some View {
        ZStack {
            Rectangle()
                .fill(
                    LinearGradient(
                        colors: [Color(white: 0.2), Color(white: 0.15)],
                        startPoint: .topLeading,
                        endPoint: .bottomTrailing
                    )
                )
            Image(systemName: "music.note")
                .font(.system(size: max(12, CGFloat(size) * 0.15)))
                .foregroundColor(.gray)
        }
    }
}

// MARK: - Keyboard Done Button
/// Adds a "Done" button above the keyboard on any TextField or SecureField.
/// Usage: TextField(...).keyboardDoneButton()
extension View {
    func keyboardDoneButton() -> some View {
        self.toolbar {
            ToolbarItemGroup(placement: .keyboard) {
                Spacer()
                Button("Done") {
                    UIApplication.shared.sendAction(
                        #selector(UIResponder.resignFirstResponder),
                        to: nil, from: nil, for: nil
                    )
                }
                .foregroundColor(Color(red: 1.0, green: 0.176, blue: 0.333))
                .fontWeight(.medium)
            }
        }
    }
}