libos+cp: Add prompt functionality

apps/cp.cpp

@@ -1,11 +1,13 @@
 #include <luna/PathParser.h>
+#include <luna/String.h>
 #include <os/ArgumentParser.h>
 #include <os/File.h>
 #include <os/FileSystem.h>
+#include <os/Prompt.h>
 
 using os::File;
 
-Result<void> copy_file(StringView source, StringView destination, bool verbose)
+Result<void> copy_file(StringView source, StringView destination, bool verbose, bool interactive)
 {
     SharedPtr<File> source_file = TRY(os::File::open(source, File::ReadOnly));
     SharedPtr<File> destination_file;
@@ -19,10 +21,23 @@ Result<void> copy_file(StringView source, StringView destination, bool verbose)
         auto basename = TRY(PathParser::basename(source));
         auto path = TRY(PathParser::join_paths(destination, basename.view()));
 
+        if (interactive && os::FileSystem::exists(path.view(), false))
+        {
+            auto prompt = TRY(String::format("cp: Overwrite %s with %s?"_sv, path.chars(), source.chars()));
+            if (!os::conditional_prompt(prompt.view(), os::DefaultNo)) return {};
+        }
+
         destination_file = TRY(File::open_or_create(path.view(), File::ReadWrite, st.st_mode & ~S_IFMT));
     }
     else
+    {
+        if (interactive && os::FileSystem::exists(destination, false))
+        {
+            auto prompt = TRY(String::format("cp: Overwrite %s with %s?"_sv, destination.chars(), source.chars()));
+            if (!os::conditional_prompt(prompt.view(), os::DefaultNo)) return {};
+        }
         destination_file = TRY(File::open_or_create(destination, File::ReadWrite, st.st_mode & ~S_IFMT));
+    }
 
     if (verbose) os::eprintln("copying %s to %s", source.chars(), destination.chars());
 
@@ -42,6 +57,7 @@ Result<int> luna_main(int argc, char** argv)
     Vector<StringView> files;
     StringView destination;
     bool verbose { false };
+    bool interactive { false };
 
     os::ArgumentParser parser;
     parser.add_description("Copy files or directories."_sv);
@@ -49,9 +65,10 @@ Result<int> luna_main(int argc, char** argv)
     parser.set_vector_argument(files, "files"_sv, true);
     parser.add_positional_argument(destination, "destination"_sv, true);
     parser.add_switch_argument(verbose, 'v', "verbose"_sv, "show more information"_sv);
-    parser.parse(argc, argv);
+    parser.add_switch_argument(interactive, 'i', "interactive"_sv, "prompt before overwriting existing files"_sv);
+    TRY(parser.parse(argc, argv));
 
-    for (const auto& file : files) { TRY(copy_file(file, destination, verbose)); }
+    for (const auto& file : files) { TRY(copy_file(file, destination, verbose, interactive)); }
 
     return 0;
 }

libos/CMakeLists.txt

@@ -12,6 +12,7 @@ set(SOURCES
     src/Main.cpp
     src/Path.cpp
     src/Mode.cpp
+    src/Prompt.cpp
 )
 
 add_library(os ${SOURCES})

libos/include/os/Prompt.h

@@ -0,0 +1,35 @@
+/**
+ * @file Prompt.h
+ * @author apio (cloudapio.eu)
+ * @brief A few functions to get input from the user.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/StringView.h>
+
+namespace os
+{
+    /**
+     * @brief The default value for a conditional prompt.
+     *
+     */
+    enum DefaultValue
+    {
+        DefaultNo = 0,
+        DefaultYes = 1
+    };
+
+    /**
+     * @brief Show a prompt asking a yes or no question to the user.
+     *
+     * @param prompt The prompt that will be shown, without the "[y/N]" part. This will be added automatically by the
+     * function.
+     * @param fallback The value to return if the user's input was not a valid yes or no answer.
+     * @return true If the user entered 'y', 'Y', or the default value was yes and the input was invalid.
+     * @return false If the user entered 'n', 'N', or the default value was no and the input was invalid.
+     */
+    bool conditional_prompt(StringView prompt, DefaultValue fallback);
+}

libos/src/Prompt.cpp

@@ -0,0 +1,24 @@
+#include <luna/String.h>
+#include <os/File.h>
+#include <os/Prompt.h>
+
+namespace os
+{
+    bool conditional_prompt(StringView prompt, DefaultValue fallback)
+    {
+        bool default_yes = fallback == DefaultYes;
+
+        os::print("%s [%s] ", prompt.chars(), default_yes ? "Y/n" : "y/N");
+
+        auto line_or_error = os::File::standard_input()->read_line();
+        if (line_or_error.has_error()) return default_yes;
+
+        auto line = line_or_error.release_value();
+        line.trim("\n");
+
+        if (line.view() == "y" || line.view() == "Y") return true;
+        if (line.view() == "n" || line.view() == "N") return false;
+
+        return default_yes;
+    }
+}