import Foundation

/// Where a produced file goes, and what it is called.
enum OutputNaming {
    /// ``name.pdf`` for ``photo.jpg`` — appends ``-2``, ``-3`` … when the
    /// target already exists (unless the user asked to overwrite).
    static func destination(for source: URL, format: Format, settings: Settings = .shared) -> URL {
        let base = source.deletingPathExtension().lastPathComponent
        let directory: URL
        switch settings.outputLocation {
        case .besideOriginal:
            directory = source.deletingLastPathComponent()
        case .chosenFolder:
            let folder = settings.resolvedOutputFolder
            directory = FileManager.default.fileExists(atPath: folder.path)
                ? folder
                : source.deletingLastPathComponent()
        }
        let candidate = directory.appendingPathComponent(base).appendingPathExtension(format.ext)
        return settings.conflictPolicy == .overwrite ? candidate : availableURL(for: candidate)
    }

    /// A sibling of any output a tool produces (e.g. ``photo-compressed.jpg``).
    static func sibling(for source: URL, suffix: String, extension ext: String? = nil) -> URL {
        let base = source.deletingPathExtension().lastPathComponent
        let directory = source.deletingLastPathComponent()
        let resolvedExtension = ext ?? source.pathExtension
        return availableURL(
            for: directory.appendingPathComponent(base + suffix).appendingPathExtension(resolvedExtension)
        )
    }

    /// A working directory for multi-file outputs (split pages, extracted
    /// images, unarchived trees).
    static func artifactDirectory(for source: URL, suffix: String) -> URL {
        let base = source.deletingPathExtension().lastPathComponent
        let directory = source.deletingLastPathComponent()
        let url = directory.appendingPathComponent(base + suffix, isDirectory: true)
        var candidate = url
        var index = 2
        while FileManager.default.fileExists(atPath: candidate.path) {
            candidate = directory.appendingPathComponent("\(base + suffix) \(index)", isDirectory: true)
            index += 1
        }
        return candidate
    }

    /// ``foo 2.txt``, ``foo 3.txt`` … until the name is free.
    static func availableURL(for url: URL) -> URL {
        guard FileManager.default.fileExists(atPath: url.path) else { return url }
        let directory = url.deletingLastPathComponent()
        let ext = url.pathExtension
        let base = url.deletingPathExtension().lastPathComponent
        var index = 2
        while true {
            let name = ext.isEmpty ? "\(base) \(index)" : "\(base) \(index).\(ext)"
            let candidate = directory.appendingPathComponent(name)
            if !FileManager.default.fileExists(atPath: candidate.path) { return candidate }
            index += 1
        }
    }

    static func uniqueChild(of directory: URL, suggestedName: String) -> URL {
        availableURL(for: directory.appendingPathComponent(suggestedName))
    }
}