CHGenerator/WebsiteGenerator/FileSystem.swift

import Foundation

enum FileSystem {

    fileprivate static var fm: FileManager { .default }

    static func folders(in folder: URL) throws -> [URL] {
        try fm.contentsOfDirectory(at: folder, includingPropertiesForKeys: [.isDirectoryKey])
            .filter { $0.isDirectory }
    }

    /**
     Copy a file to the destination, creating the containing folder if needed
     */
    static func copy(_ source: URL, to destination: URL) throws {
        try destination.ensureParentFolderExistence()
        try source.copy(to: destination)
    }

}

extension URL {

    func ensureParentFolderExistence() throws {
        try deletingLastPathComponent().ensureFolderExistence()
    }

    func ensureFolderExistence() throws {
        if !exists {
            print("Creating directory \(path)")
            try wrap(.failedToWriteFile(path)) {
                try FileManager.default.createDirectory(at: self, withIntermediateDirectories: true)
            }
        }
    }

    var isDirectory: Bool {
        (try? resourceValues(forKeys: [.isDirectoryKey]))?.isDirectory == true
    }

    var exists: Bool {
        FileSystem.fm.fileExists(atPath: path)
    }

    func delete() throws {
        try FileSystem.fm.removeItem(at: self)
    }

    func copy(to url: URL) throws {
        try wrap(.failedToWriteFile(url.path)) {
            if url.exists {
                try url.delete()
            }
            try url.ensureParentFolderExistence()
            try FileSystem.fm.copyItem(at: self, to: url)
        }
    }
}

extension Data {

    func createFolderAndWrite(to url: URL) throws {
        try url.ensureParentFolderExistence()
//        if url.exists {
//            print("Overwriting \(url.path)")
//        }
        try wrap(.failedToWriteFile(url.path)) {
            try write(to: url)
        }
    }
}

extension String {

    func createFolderAndWrite(to url: URL) throws {
        try data(using: .utf8)!.createFolderAndWrite(to: url)
    }
}

extension Encodable {

    func writeJSON(to url: URL) throws {
        let encoder = JSONEncoder()
        encoder.outputFormatting = .prettyPrinted
        let content = try wrap(.failedToEncodeJSON(url.path)) {
            try encoder.encode(self)
        }
        try content.createFolderAndWrite(to: url)
    }
}

extension Decodable {

    init(decodeFrom url: URL) throws {
        let data = try wrap(.failedToOpenFile(url.path)) {
            try Data(contentsOf: url)
        }
        self = try wrap({ .failedToDecodeJSON(file: url.path, error: $0.localizedDescription)}) {
            try JSONDecoder().decode(Self.self, from: data)
        }
    }
}