import Foundation
import AVFoundation
import Combine

/// Captures a radio stream into a local file buffer for timeshift scrubbing and recording.
/// No microphone is used — the raw stream bytes are saved directly from URLSession.
class RadioStreamBuffer: NSObject, ObservableObject, URLSessionDataDelegate {
    static let shared = RadioStreamBuffer()
    
    // MARK: - Published State
    @Published var isBuffering = false
    @Published var isRecording = false
    @Published var recordingTimeFormatted: String = "0:00"
    @Published var bufferedDuration: TimeInterval = 0
    @Published var isLive = true
    @Published var isHLSStream = false  // HLS streams can't be raw-buffered
    
    // MARK: - Config
    let maxBufferDuration: TimeInterval = 20 * 60  // 20 minutes
    
    // MARK: - Internal
    private var dataTask: URLSessionDataTask?
    private var urlSession: URLSession?
    private var bufferFileHandle: FileHandle?
    private var bufferFileURL: URL?
    private var totalBytesWritten: Int64 = 0
    private var streamStartTime: Date?
    private var estimatedBitRate: Double = 128000  // bits per second, updated from headers
    private var recordingStartByte: Int64 = 0
    private var recordingTimer: Timer?
    private var recordingStartTime: Date?
    private var stationName: String = ""
    private var bufferGeneration: Int = 0  // Prevents old URLSession callbacks from overwriting state
    
    private override init() {
        super.init()
    }
    
    // MARK: - Start Buffering
    
    private func rlog(_ msg: String) {
        DebugLogger.shared.log(msg, category: "Radio")
    }
    
    /// Start capturing a radio stream. Call this when a radio station starts playing.
    /// The URL should already be resolved (not a .pls/.m3u playlist) — use resolveStreamURL() first.
    func startBuffering(url: URL, stationName: String) {
        // Increment generation BEFORE stopping — so old callbacks are ignored
        bufferGeneration += 1
        let gen = bufferGeneration
        
        stopBuffering()
        self.stationName = stationName
        isHLSStream = false
        rlog("Start buffering (gen \(gen)): \(stationName) → \(url.absoluteString)")
        
        // Detect HLS from URL extension
        let ext = url.pathExtension.lowercased()
        if ext == "m3u8" {
            rlog("HLS stream detected from URL extension — buffering/recording unavailable")
            isHLSStream = true
            isBuffering = false
            return
        }
        
        // Create temp file
        let tempDir = FileManager.default.temporaryDirectory
        let filename = "radio_buffer_\(UUID().uuidString).raw"
        let fileURL = tempDir.appendingPathComponent(filename)
        FileManager.default.createFile(atPath: fileURL.path, contents: nil)
        
        do {
            bufferFileHandle = try FileHandle(forWritingTo: fileURL)
        } catch {
            rlog("Failed to create buffer file: \(error)")
            return
        }
        
        bufferFileURL = fileURL
        totalBytesWritten = 0
        streamStartTime = Date()
        isBuffering = true
        isLive = true
        bufferedDuration = 0
        
        let config = URLSessionConfiguration.default
        config.timeoutIntervalForRequest = 30
        config.waitsForConnectivity = true
        urlSession = URLSession(configuration: config, delegate: self, delegateQueue: nil)
        dataTask = urlSession?.dataTask(with: url)
        dataTask?.resume()
    }
    
    /// Stop capturing — cleans up temp file
    func stopBuffering() {
        if isBuffering { rlog("Stop buffering: \(stationName)") }
        _ = stopRecording()
        dataTask?.cancel()
        dataTask = nil
        urlSession?.invalidateAndCancel()
        urlSession = nil
        bufferFileHandle?.closeFile()
        bufferFileHandle = nil
        
        // Clean up temp file
        if let url = bufferFileURL {
            try? FileManager.default.removeItem(at: url)
        }
        bufferFileURL = nil
        totalBytesWritten = 0
        streamStartTime = nil
        isBuffering = false
        isHLSStream = false
        bufferedDuration = 0
        isLive = true
    }
    
    // MARK: - URLSessionDataDelegate
    
    func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Void) {
        if let httpResponse = response as? HTTPURLResponse {
            rlog("Stream response: HTTP \(httpResponse.statusCode)")
            
            let ct = httpResponse.mimeType?.lowercased() ?? ""
            
            // Detect HLS from content-type
            let hlsTypes = ["application/vnd.apple.mpegurl", "application/x-mpegurl"]
            if hlsTypes.contains(ct) || (ct.contains("mpegurl") && ct.contains("apple")) {
                rlog("HLS stream detected from content-type (\(ct)) — cancelling raw buffer")
                DispatchQueue.main.async {
                    self.isHLSStream = true
                    self.isBuffering = false
                }
                completionHandler(.cancel)
                return
            }
            
            // Detect playlist content-types (PLS, M3U, ASX) — shouldn't happen
            // if resolution worked, but guard against it
            if Self.playlistContentTypes.contains(ct) {
                rlog("Playlist content-type detected (\(ct)) — URL was not resolved. Cancelling buffer.")
                DispatchQueue.main.async {
                    self.isBuffering = false
                }
                completionHandler(.cancel)
                return
            }
            
            if let icyBR = httpResponse.allHeaderFields["icy-br"] as? String,
               let br = Double(icyBR) {
                estimatedBitRate = br * 1000
                rlog("Stream bitrate (icy-br): \(icyBR) kbps")
            }
            if let mimeType = httpResponse.mimeType {
                rlog("Stream content-type: \(mimeType)")
            }
        }
        completionHandler(.allow)
    }
    
    func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
        bufferFileHandle?.write(data)
        totalBytesWritten += Int64(data.count)
        
        let bytesPerSecond = estimatedBitRate / 8.0
        let estDuration = Double(totalBytesWritten) / bytesPerSecond
        
        DispatchQueue.main.async {
            self.bufferedDuration = estDuration
        }
    }
    
    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        let gen = bufferGeneration  // Capture current generation
        if let error = error as? NSError, error.code != NSURLErrorCancelled {
            rlog("Stream ended with error (gen \(gen)): \(error.localizedDescription)")
        } else if error == nil {
            rlog("Stream ended normally (gen \(gen))")
        } else {
            rlog("Stream cancelled (gen \(gen))")
        }
        DispatchQueue.main.async { [weak self] in
            guard let self = self else { return }
            // Only mark as not buffering if this callback is from the CURRENT session
            // Old cancelled sessions must not reset the flag
            if gen == self.bufferGeneration {
                self.isBuffering = false
                self.rlog("isBuffering → false (gen \(gen) matches)")
            } else {
                self.rlog("Ignoring stale completion (gen \(gen), current \(self.bufferGeneration))")
            }
        }
    }
    
    // MARK: - Timeshift Playback
    
    /// Get a playable URL for the buffer. AVPlayer can seek within this file.
    var bufferPlaybackURL: URL? {
        return bufferFileURL
    }
    
    /// Estimated duration of buffered content
    var estimatedBufferSeconds: TimeInterval {
        let bytesPerSecond = estimatedBitRate / 8.0
        guard bytesPerSecond > 0 else { return 0 }
        return Double(totalBytesWritten) / bytesPerSecond
    }
    
    /// Convert a "seconds ago" offset to a byte position for seeking
    func seekPosition(secondsFromLive: TimeInterval) -> TimeInterval {
        let total = estimatedBufferSeconds
        return max(0, total - secondsFromLive)
    }
    
    // MARK: - Recording (no mic — direct stream capture)
    
    /// Start recording — marks the current buffer position
    func startRecording() {
        rlog("startRecording: isBuffering=\(isBuffering), isHLS=\(isHLSStream), totalBytes=\(totalBytesWritten), gen=\(bufferGeneration)")
        
        if isHLSStream {
            rlog("startRecording SKIPPED: HLS streams cannot be raw-captured. Recording unavailable for this station.")
            return
        }
        
        guard isBuffering else {
            rlog("startRecording FAILED: not buffering. URLSession state: \(urlSession != nil ? "exists" : "nil"), dataTask: \(dataTask?.state.rawValue ?? -1)")
            return
        }
        rlog("Recording started at byte offset \(totalBytesWritten)")
        recordingStartByte = totalBytesWritten
        recordingStartTime = Date()
        isRecording = true
        recordingTimeFormatted = "0:00"
        
        recordingTimer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
            guard let start = self?.recordingStartTime else { return }
            let elapsed = Int(Date().timeIntervalSince(start))
            let min = elapsed / 60
            let sec = elapsed % 60
            DispatchQueue.main.async {
                self?.recordingTimeFormatted = String(format: "%d:%02d", min, sec)
            }
        }
    }
    
    /// Stop recording — saves the captured segment to Documents/RadioRecordings/
    func stopRecording() -> URL? {
        guard isRecording else { return nil }
        isRecording = false
        recordingTimer?.invalidate()
        recordingTimer = nil
        
        guard let bufferURL = bufferFileURL else { return nil }
        
        // Read the recorded segment from the buffer file
        let endByte = totalBytesWritten
        let recordedBytes = endByte - recordingStartByte
        guard recordedBytes > 0 else { return nil }
        
        do {
            let fm = FileManager.default
            let docs = fm.urls(for: .documentDirectory, in: .userDomainMask).first!
            let dir = docs.appendingPathComponent("RadioRecordings", isDirectory: true)
            try fm.createDirectory(at: dir, withIntermediateDirectories: true)
            
            let dateStr = ISO8601DateFormatter().string(from: Date())
                .replacingOccurrences(of: ":", with: "-")
            let safeName = stationName.replacingOccurrences(of: "/", with: "-")
            
            // Determine extension from stream content
            let ext = guessExtension()
            let filename = "\(safeName)_\(dateStr).\(ext)"
            let destURL = dir.appendingPathComponent(filename)
            
            // Read segment from buffer file
            let readHandle = try FileHandle(forReadingFrom: bufferURL)
            readHandle.seek(toFileOffset: UInt64(recordingStartByte))
            let data = readHandle.readData(ofLength: Int(recordedBytes))
            readHandle.closeFile()
            
            try data.write(to: destURL)
            print("Saved recording: \(filename) (\(data.count) bytes)")
            
            recordingTimeFormatted = "0:00"
            return destURL
        } catch {
            print("Failed to save recording: \(error)")
            return nil
        }
    }
    
    private func guessExtension() -> String {
        // Default to mp3 for radio streams — most common
        return "mp3"
    }
    
    // MARK: - Playlist URL Resolver
    
    /// Playlist file extensions that wrap the actual audio stream URL
    private static let playlistExtensions: Set<String> = ["pls", "m3u", "asx", "xspf"]
    
    /// Content-types that indicate a playlist, not audio
    private static let playlistContentTypes: Set<String> = [
        "audio/x-scpls", "audio/scpls",                     // PLS
        "audio/x-mpegurl", "audio/mpegurl",                  // M3U
        "application/vnd.apple.mpegurl", "application/x-mpegurl", // HLS M3U8
        "video/x-ms-asf", "application/x-mms-framed",        // ASX
        "application/xspf+xml"                                // XSPF
    ]
    
    /// Check if a URL points to a playlist file rather than a direct audio stream
    static func isPlaylistURL(_ url: URL) -> Bool {
        playlistExtensions.contains(url.pathExtension.lowercased())
    }
    
    /// Resolve a playlist URL to the actual audio stream URL.
    /// If the URL is already a direct stream, returns it unchanged.
    static func resolveStreamURL(_ url: URL) async -> URL {
        let ext = url.pathExtension.lowercased()
        guard playlistExtensions.contains(ext) else { return url }
        
        DebugLogger.shared.log("Resolving playlist URL (\(ext)): \(url.lastPathComponent)", category: "Radio")
        
        do {
            let (data, response) = try await URLSession.shared.data(from: url)
            guard let text = String(data: data, encoding: .utf8) ?? String(data: data, encoding: .ascii) else {
                DebugLogger.shared.log("Playlist: couldn't decode text", category: "Radio")
                return url
            }
            
            // Check content-type to determine format
            let ct = (response as? HTTPURLResponse)?.mimeType?.lowercased() ?? ""
            
            // HLS — return original URL, AVPlayer handles it natively
            if ct.contains("mpegurl") && ext == "m3u8" {
                DebugLogger.shared.log("Playlist is HLS — returning original URL for AVPlayer", category: "Radio")
                return url
            }
            
            // Try parsing based on extension / content
            if let resolved = parsePLS(text) ?? parseM3U(text) ?? parseASX(text) {
                DebugLogger.shared.log("Resolved stream: \(resolved.absoluteString)", category: "Radio")
                return resolved
            }
            
            DebugLogger.shared.log("Playlist: no stream URL found in \(data.count) bytes", category: "Radio")
            return url
        } catch {
            DebugLogger.shared.log("Playlist resolve failed: \(error.localizedDescription)", category: "Radio")
            return url
        }
    }
    
    /// Parse PLS format: `File1=http://...`
    private static func parsePLS(_ text: String) -> URL? {
        for line in text.components(separatedBy: .newlines) {
            let trimmed = line.trimmingCharacters(in: .whitespaces)
            // Match File1=, File2=, etc.
            if trimmed.lowercased().hasPrefix("file"),
               let eqIndex = trimmed.firstIndex(of: "=") {
                let urlString = String(trimmed[trimmed.index(after: eqIndex)...]).trimmingCharacters(in: .whitespaces)
                if urlString.lowercased().hasPrefix("http"), let url = URL(string: urlString) {
                    return url
                }
            }
        }
        return nil
    }
    
    /// Parse M3U format: first non-comment line starting with http
    private static func parseM3U(_ text: String) -> URL? {
        for line in text.components(separatedBy: .newlines) {
            let trimmed = line.trimmingCharacters(in: .whitespaces)
            if trimmed.isEmpty || trimmed.hasPrefix("#") { continue }
            if trimmed.lowercased().hasPrefix("http"), let url = URL(string: trimmed) {
                return url
            }
        }
        return nil
    }
    
    /// Parse ASX format: `<ref href="http://..."/>`
    private static func parseASX(_ text: String) -> URL? {
        // Simple regex-free parse for <ref href="..."/>
        let lower = text.lowercased()
        guard let refRange = lower.range(of: "href") else { return nil }
        let after = text[refRange.upperBound...]
        // Find the quoted URL
        guard let quoteStart = after.firstIndex(of: "\"") else { return nil }
        let urlStart = after.index(after: quoteStart)
        guard let quoteEnd = after[urlStart...].firstIndex(of: "\"") else { return nil }
        let urlString = String(after[urlStart..<quoteEnd])
        if urlString.lowercased().hasPrefix("http") {
            return URL(string: urlString)
        }
        return nil
    }
}