feat(cli): add --json to 'formats'

src/Filee.Cli/Cli.cs

@@ -339,13 +339,43 @@ private static int ListFormats(CliOptions options, CliHost host, TextWriter outp
             var targets = FormatRegistry.Known.Where(t => t.Writable && t.Id != from.Id).ToList();
             var now = targets.Where(t => installed.CanConvert(from.Id, t.Id)).Select(t => t.Id).ToList();
             var later = targets.Where(t => !now.Contains(t.Id) && everything.CanConvert(from.Id, t.Id)).Select(t => t.Id).ToList();
+            if (options.Json)
+            {
+                WriteJsonDocument(output, json =>
+                {
+                    json.WriteStartObject();
+                    WriteFormatFields(json, from);
+                    WriteStrings(json, "targets", now);
+                    WriteStrings(json, "withEngines", later);
+                    json.WriteEndObject();
+                });
+                return Success;
+            }
             output.WriteLine($"{from.DisplayName} ({string.Join(", ", from.Extensions)}) converts to:");
             output.WriteLine(now.Count > 0 ? "  " + string.Join(", ", now) : "  (nothing with the engines installed now)");
             if (later.Count > 0)
                 output.WriteLine($"With optional engines (install them in Filee, Settings → Engines):{Environment.NewLine}  {string.Join(", ", later)}");
             return Success;
         }
 
+        if (options.Json)
+        {
+            WriteJsonDocument(output, json =>
+            {
+                json.WriteStartObject();
+                json.WriteStartArray("formats");
+                foreach (var format in FormatRegistry.Known.Where(f => f.Id != FormatRegistry.Folder))
+                {
+                    json.WriteStartObject();
+                    WriteFormatFields(json, format);
+                    json.WriteEndObject();
+                }
+                json.WriteEndArray();
+                json.WriteEndObject();
+            });
+            return Success;
+        }
+
         foreach (var group in FormatRegistry.Known.Where(f => f.Id != FormatRegistry.Folder).GroupBy(f => f.Category))
         {
             output.WriteLine($"{group.Key}:");
@@ -357,6 +387,32 @@ private static int ListFormats(CliOptions options, CliHost host, TextWriter outp
         return Success;
     }
 
+    /// <summary>The fields of one format in the JSON of 'formats': the same names for the list and for one format.</summary>
+    private static void WriteFormatFields(Utf8JsonWriter json, FileFormat format)
+    {
+        json.WriteString("id", format.Id);
+        json.WriteString("name", format.DisplayName);
+        json.WriteString("category", format.Category.ToString().ToLowerInvariant());
+        WriteStrings(json, "extensions", format.Extensions);
+        json.WriteBoolean("writable", format.Writable);
+    }
+
+    private static void WriteStrings(Utf8JsonWriter json, string name, IEnumerable<string> values)
+    {
+        json.WriteStartArray(name);
+        foreach (var value in values)
+            json.WriteStringValue(value);
+        json.WriteEndArray();
+    }
+
+    private static void WriteJsonDocument(TextWriter output, Action<Utf8JsonWriter> write)
+    {
+        using var stream = new MemoryStream();
+        using (var json = new Utf8JsonWriter(stream, new JsonWriterOptions { Indented = true }))
+            write(json);
+        output.WriteLine(System.Text.Encoding.UTF8.GetString(stream.ToArray()));
+    }
+
     private static int ListPresets(CliHost host, TextWriter output)
     {
         output.WriteLine($"{"ID",-24} {"NAME",-28} TARGET");

src/Filee.Cli/Help.cs

@@ -14,7 +14,8 @@ internal static class Help
     {
         "convert" => Convert,
         "watch" => Watch,
-        "formats" => "Usage: filee formats [<format>]\n\nLists every format, or what one format converts to.\n",
+        "formats" => "Usage: filee formats [<format>] [--json]\n\nLists every format, or what one format converts to.\n" +
+                     "With --json, prints the same as JSON (for scripts and other programs).\n",
         "presets" => "Usage: filee presets\n\nLists the presets saved in Filee (built-in and your own).\n",
         _ => General,
     };
@@ -26,7 +27,7 @@ internal static class Help
           filee convert <files or folders...> --to <format> [options]
           filee convert <files or folders...> --preset <preset> [options]
           filee watch <folder> --to <format> [options]
-          filee formats [<format>]
+          filee formats [<format>] [--json]
           filee presets
           filee help [<command>]
           filee version

tests/Filee.Cli.Tests/CliTests.cs

@@ -328,6 +328,41 @@ public async Task Archives_list_folder_as_a_target()
         Assert.DoesNotContain("folder", output);
     }
 
+    [Fact]
+    public async Task Formats_json_lists_every_format()
+    {
+        var (code, output, _) = await Run("formats", "--json");
+        Assert.Equal(Cli.Success, code);
+
+        using var json = JsonDocument.Parse(output);
+        var formats = json.RootElement.GetProperty("formats").EnumerateArray().ToList();
+        var png = Assert.Single(formats, f => f.GetProperty("id").GetString() == "png");
+        Assert.Equal("image", png.GetProperty("category").GetString());
+        Assert.Contains("png", png.GetProperty("extensions").EnumerateArray().Select(e => e.GetString()));
+        Assert.True(png.GetProperty("writable").GetBoolean());
+        Assert.DoesNotContain(formats, f => f.GetProperty("id").GetString() == "folder");
+    }
+
+    [Fact]
+    public async Task Formats_json_of_one_format_matches_the_text()
+    {
+        var (code, text, _) = await Run("formats", "zip");
+        Assert.Equal(Cli.Success, code);
+        (code, var output, _) = await Run("formats", "zip", "--json");
+        Assert.Equal(Cli.Success, code);
+
+        using var json = JsonDocument.Parse(output);
+        var root = json.RootElement;
+        Assert.Equal("zip", root.GetProperty("id").GetString());
+        Assert.Equal("archive", root.GetProperty("category").GetString());
+        var targets = root.GetProperty("targets").EnumerateArray().Select(e => e.GetString()!).ToList();
+        var withEngines = root.GetProperty("withEngines").EnumerateArray().Select(e => e.GetString()!).ToList();
+        Assert.Contains("folder", targets.Concat(withEngines));
+        Assert.Empty(targets.Intersect(withEngines));
+        foreach (var id in targets.Concat(withEngines))
+            Assert.Contains(id, text);
+    }
+
     [Fact]
     public async Task Jpeg_xr_converts_on_windows_and_is_no_download_away_elsewhere()
     {