//
//  SyncLogger.swift
//  SportsTime
//
//  File-based logger for sync operations.
//  Writes to Documents/sync_log.txt for viewing in Settings.
//

import Foundation

final class SyncLogger: @unchecked Sendable {
    static let shared = SyncLogger()

    private let fileURL: URL
    private let maxLines = 500
    private let queue = DispatchQueue(label: "com.88oakapps.SportsTime.synclogger")

    private init() {
        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
            ?? FileManager.default.temporaryDirectory
        fileURL = docs.appendingPathComponent("sync_log.txt")
    }

    // MARK: - Public API

    func log(_ message: String) {
        let timestamp = ISO8601DateFormatter().string(from: Date())
        let line = "[\(timestamp)] \(message)\n"

        // Also print to console
        #if DEBUG
        print(message)
        #endif

        queue.async { [weak self] in
            self?.appendToFile(line)
        }
    }

    func readLog() -> String {
        queue.sync {
            guard FileManager.default.fileExists(atPath: fileURL.path) else {
                return "No sync logs yet."
            }
            return (try? String(contentsOf: fileURL, encoding: .utf8)) ?? "Failed to read log."
        }
    }

    func clearLog() {
        queue.async { [weak self] in
            guard let self = self else { return }
            try? FileManager.default.removeItem(at: self.fileURL)
        }
    }

    // MARK: - Private

    private func appendToFile(_ line: String) {
        if !FileManager.default.fileExists(atPath: fileURL.path) {
            FileManager.default.createFile(atPath: fileURL.path, contents: nil)
        }

        guard let handle = try? FileHandle(forWritingTo: fileURL) else { return }
        defer { try? handle.close() }

        handle.seekToEndOfFile()
        if let data = line.data(using: .utf8) {
            handle.write(data)
        }

        // Trim if too large
        trimIfNeeded()
    }

    private func trimIfNeeded() {
        guard let content = try? String(contentsOf: fileURL, encoding: .utf8) else { return }
        let lines = content.components(separatedBy: "\n")

        if lines.count > maxLines {
            let trimmed = lines.suffix(maxLines).joined(separator: "\n")
            try? trimmed.write(to: fileURL, atomically: true, encoding: .utf8)
        }
    }
}