import Foundation
import UIKit

class FileLogger {
    static let shared = FileLogger()

    private var fileHandle: FileHandle?
    private let logURL: URL
    private let df: DateFormatter = {
        let f = DateFormatter()
        f.dateFormat = "HH:mm:ss.SSS"
        return f
    }()

    private init() {
        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
        logURL = docs.appendingPathComponent("coreml_test.log")
        if !FileManager.default.fileExists(atPath: logURL.path) {
            FileManager.default.createFile(atPath: logURL.path, contents: nil)
        }
        fileHandle = try? FileHandle(forWritingTo: logURL)
        fileHandle?.seekToEndOfFile()
        log("========== NEW SESSION ==========")
        log("iOS \(UIDevice.current.systemVersion) | \(UIDevice.current.model)")
        log("Date: \(Date())")
    }

    func log(_ message: String) {
        let ts = df.string(from: Date())
        let thread = Thread.isMainThread ? "MAIN" : (Thread.current.name ?? "BG")
        let line = "[\(ts)][\(thread)] \(message)\n"
        if let data = line.data(using: .utf8) {
            fileHandle?.write(data)
        }
        print(line, terminator: "")
    }

    func getLogURL() -> URL { logURL }

    func clearLog() {
        try? "".write(to: logURL, atomically: true, encoding: .utf8)
        log("========== LOG CLEARED ==========")
    }

    deinit { fileHandle?.closeFile() }
}

func log(_ msg: String) { FileLogger.shared.log(msg) }