import Foundation

final class Logger {
    static let shared = Logger()
    private let queue = DispatchQueue(label: "org.prole.tools.logger", qos: .utility)
    private var currentDateStr: String = Logger.dateString(Date())

    private init() {
        // Ensure directories exist
        ProleEnv.bootstrap()
        // Ensure current symlink points to today's file (best effort)
        queue.async { [weak self] in self?.ensureSymlink() }
    }

    private static func dateString(_ date: Date) -> String {
        let fmt = DateFormatter()
        fmt.locale = Locale(identifier: "en_US_POSIX")
        fmt.dateFormat = "yyyy-MM-dd"
        return fmt.string(from: date)
    }

    private func logDir() -> URL { ProleEnv.logsDir() }

    private func datedLogURL(for dateStr: String) -> URL {
        return logDir().appendingPathComponent("prole-tools-app-\(dateStr).log")
    }

    private func currentLogURL() -> URL {
        return logDir().appendingPathComponent("prole-tools-app.log")
    }

    private func ensureSymlink() {
        let fm = FileManager.default
        let target = datedLogURL(for: currentDateStr)
        let link = currentLogURL()
        // If link exists and points to target, nothing to do
        if let attrs = try? fm.attributesOfItem(atPath: link.path), attrs[.type] as? FileAttributeType == .typeSymbolicLink {
            if let dest = try? fm.destinationOfSymbolicLink(atPath: link.path), dest.hasSuffix(target.lastPathComponent) {
                return
            }
        }
        // Recreate symlink to today's file
        _ = try? fm.removeItem(at: link)
        try? fm.createSymbolicLink(at: link, withDestinationURL: target)
    }

    private func rotateIfNeeded(now: Date = Date()) {
        let today = Logger.dateString(now)
        if today != currentDateStr {
            currentDateStr = today
            ensureSymlink()
        }
    }

    func info(_ message: String) { write(level: "INFO", message) }
    func error(_ message: String) { write(level: "ERROR", message) }

    func write(level: String, _ message: String) {
        queue.async {
            self.rotateIfNeeded()
            let ts = ISO8601DateFormatter().string(from: Date())
            let line = "[\(level)] \(ts) \(message)\n"
            let fileURL = self.datedLogURL(for: self.currentDateStr)
            if let data = line.data(using: .utf8) {
                if FileManager.default.fileExists(atPath: fileURL.path) {
                    if let h = try? FileHandle(forWritingTo: fileURL) {
                        defer { try? h.close() }
                        try? h.seekToEnd()
                        try? h.write(contentsOf: data)
                    }
                } else {
                    try? data.write(to: fileURL, options: .atomic)
                }
            }
        }
    }
}