//===----------------------------------------------------------------------===//
// Copyright © 2025-2026 Apple Inc. and the container project authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//===----------------------------------------------------------------------===//

import ContainerVersion
import Foundation
import SystemPackage

/// Provides the application installation root path.
public struct InstallRoot {
    /// The environment variable that if set, determines the root directory for installed application.
    /// Otherwise, the system computes the install path as the parent of the directory containing the
    /// application binary (for example, "/usr/local/bin/container" -> "/usr/local").
    public static let environmentName = "CONTAINER_INSTALL_ROOT"

    /// The default root directory used when the environment variable is not set.
    ///
    /// Computed as the grandparent of ``CommandLine/executablePath``
    /// (for example, `/usr/local/bin/container` → `/usr/local`).
    /// Lexically normalized but not canonical, as symlinks in the executable path are not resolved.
    public static let defaultPath = CommandLine.executablePath
        .removingLastComponent()
        .removingLastComponent()

    /// The resolved root directory path, always lexically normalized.
    ///
    /// If the environment variable is set to an absolute path, that path is used directly.
    /// If it is set to a relative path, the path is resolved against the working directory.
    /// Otherwise, ``defaultPath`` is used.
    public static let path = FilePath(FileManager.default.currentDirectoryPath).resolve(
        ProcessInfo.processInfo.environment[environmentName],
        defaultPath: defaultPath
    )

    /// The pathname to the root directory
    public static let pathname = path.string
}