//
//  UpdateCheckService.swift
//  oAI
//
//  Checks for new releases on GitLab and surfaces an update badge in the footer
//
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2026 Rune Olsen
//
// This file is part of oAI.
//
// oAI is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// oAI is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General
// Public License for more details.
//
// You should have received a copy of the GNU Affero General Public
// License along with oAI. If not, see <https://www.gnu.org/licenses/>.


import Foundation
#if os(macOS)
import AppKit
#endif
import Observation

@Observable
final class UpdateCheckService {
    static let shared = UpdateCheckService()

    var updateAvailable: Bool = false
    var latestVersion: String? = nil

    private let apiURL = "https://gitlab.pm/api/v4/projects/rune%2Foai-swift/releases"
    private let releasesURL = URL(string: "https://gitlab.pm/rune/oai-swift/releases")!

    private init() {}

    /// Kick off a background update check. Silently does nothing on failure.
    func checkForUpdates() {
        Task {
            await performCheck()
        }
    }

    @MainActor
    private func performCheck() async {
        guard let url = URL(string: apiURL) else { return }

        var request = URLRequest(url: url)
        request.timeoutInterval = 10

        guard let (data, _) = try? await URLSession.shared.data(for: request) else { return }
        guard let releases = try? JSONSerialization.jsonObject(with: data) as? [[String: Any]],
              let latest = releases.first,
              let tagName = latest["tag_name"] as? String else { return }

        // Strip leading "v" from tag (e.g. "v2.3.1" → "2.3.1")
        let latestVer = tagName.hasPrefix("v") ? String(tagName.dropFirst()) : tagName
        let currentVer = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "0.0.0"

        if isNewer(latestVer, than: currentVer) {
            self.latestVersion = latestVer
            self.updateAvailable = true
        }
    }

    /// Semantic version comparison — returns true if `version` is newer than `current`.
    private func isNewer(_ version: String, than current: String) -> Bool {
        let lhs = version.split(separator: ".").compactMap { Int($0) }
        let rhs = current.split(separator: ".").compactMap { Int($0) }
        let count = max(lhs.count, rhs.count)
        for i in 0..<count {
            let l = i < lhs.count ? lhs[i] : 0
            let r = i < rhs.count ? rhs[i] : 0
            if l > r { return true }
            if l < r { return false }
        }
        return false
    }

    /// Open the GitLab releases page in the default browser.
    func openReleasesPage() {
        #if os(macOS)
        NSWorkspace.shared.open(releasesURL)
        #endif
    }
}