fix: replace widget file FFI with simplifile

gleam.toml

@@ -19,6 +19,7 @@ redraw = ">= 19.2.2 and < 20.0.0"
 redraw_dom = ">= 19.2.2 and < 20.0.0"
 lustre = ">= 5.7.1 and < 6.0.0"
 mendraw = ">= 2.0.0 and < 3.0.0"
+simplifile = ">= 2.6.0 and < 3.0.0"
 
 [dev_dependencies]
 gleeunit = ">= 1.11.0 and < 2.0.0"

manifest.toml

@@ -9,6 +9,7 @@
 packages = [
   { name = "etch", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "etch", source = "hex", outer_checksum = "A4B4458EE1E7D22753538C03F0D64C930309863365D2D26570E2D2C6B7CFC5EA" },
   { name = "exception", version = "2.1.1", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "exception", source = "hex", outer_checksum = "6BDEA95248093599391C3B5DF1835C5C6A86C353C2F99CE539B450E3432FE117" },
+  { name = "filepath", version = "1.1.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "B06A9AF0BF10E51401D64B98E4B627F1D2E48C154967DA7AF4D0914780A6D40A" },
   { name = "gleam_erlang", version = "1.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "1124AD3AA21143E5AF0FC5CF3D9529F6DB8CA03E43A55711B60B6B7B3874375C" },
   { name = "gleam_fetch", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_http", "gleam_javascript", "gleam_stdlib"], otp_app = "gleam_fetch", source = "hex", outer_checksum = "284CE88E37436699545F9F65D413E1DFB6C1EA3FE3824B6EA2018D0ECF088FFC" },
   { name = "gleam_http", version = "4.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_http", source = "hex", outer_checksum = "82EA6A717C842456188C190AFB372665EA56CE13D8559BF3B1DD9E40F619EE0C" },
@@ -22,6 +23,7 @@ packages = [
   { name = "mendraw", version = "2.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "redraw", "redraw_dom"], otp_app = "mendraw", source = "hex", outer_checksum = "BB913054A5FEDC872AAB114FFADDFB791DACFE605B3DCEEAD3620F11BB59D090" },
   { name = "redraw", version = "19.2.2", build_tools = ["gleam"], requirements = ["gleam_javascript", "gleam_stdlib"], otp_app = "redraw", source = "hex", outer_checksum = "B8CEEB74E8846CE10B8360B924DAD22441B61D947F9449854164F0686C4B8661" },
   { name = "redraw_dom", version = "19.2.2", build_tools = ["gleam"], requirements = ["gleam_fetch", "gleam_stdlib", "redraw"], otp_app = "redraw_dom", source = "hex", outer_checksum = "80278296AD6E3D4457D6FF6A14FEA3E90696284BEA297BDE10E430FC4CE726B8" },
+  { name = "simplifile", version = "2.7.0", build_tools = ["gleam"], requirements = ["filepath", "gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "A2727627B063E87351934C7F7F008F2D1FDB16F6DE0B8C79F9E46459CFC9C164" },
 ]
 
 [requirements]
@@ -34,3 +36,4 @@ lustre = { version = ">= 5.7.1 and < 6.0.0" }
 mendraw = { version = ">= 2.0.0 and < 3.0.0" }
 redraw = { version = ">= 19.2.2 and < 20.0.0" }
 redraw_dom = { version = ">= 19.2.2 and < 20.0.0" }
+simplifile = { version = ">= 2.6.0 and < 3.0.0" }

src/glendix/define/file_boundary.gleam

@@ -1,83 +1,127 @@
 //// Provides typed filesystem operations for the widget definition editor.
 ////
 
+import gleam/dynamic
+import gleam/dynamic/decode
+import gleam/json
+import gleam/list
+import gleam/option
 import gleam/result
+import gleam/string
+import simplifile
 
 /// Describes a widget definition filesystem failure.
 pub type FileError {
   /// The current package does not declare a widget name.
   WidgetNameWasNotDeclared(path: String)
   /// The expected widget XML file does not exist.
   WidgetXmlWasNotFound(path: String)
-  /// A file could not be read.
+  /// A file could not be read or decoded.
+  ///
+  /// Filesystem reasons come from `simplifile.describe_error`. JSON reasons
+  /// use Glendix's stable description of `gleam_json.DecodeError`.
   FileCouldNotBeRead(path: String, reason: String)
   /// A file could not be written.
+  ///
+  /// The reason comes from `simplifile.describe_error`.
   FileCouldNotBeWritten(path: String, reason: String)
 }
 
 /// Finds the widget XML path declared by the current package.
 pub fn find_widget_xml() -> Result(String, FileError) {
-  find_widget_xml_raw()
-  |> result.map_error(map_raw_error)
+  let package_path = "package.json"
+  use package_contents <- result.try(read(package_path))
+  use widget_name <- result.try(widget_name(package_contents, package_path))
+  let widget_path = "src/" <> widget_name <> ".xml"
+
+  case simplifile.is_file(widget_path) {
+    Ok(True) -> Ok(widget_path)
+    Ok(False) -> Error(WidgetXmlWasNotFound(path: widget_path))
+    Error(error) ->
+      Error(FileCouldNotBeRead(
+        path: widget_path,
+        reason: simplifile.describe_error(error),
+      ))
+  }
 }
 
 /// Reads a UTF-8 text file.
 pub fn read(path path: String) -> Result(String, FileError) {
-  read_raw(path)
-  |> result.map_error(map_raw_error)
+  simplifile.read(from: path)
+  |> result.map_error(fn(error) {
+    FileCouldNotBeRead(path: path, reason: simplifile.describe_error(error))
+  })
 }
 
 /// Writes a UTF-8 text file.
 pub fn write(
   path path: String,
   content content: String,
 ) -> Result(Nil, FileError) {
-  write_raw(path, content)
-  |> result.map_error(map_raw_error)
+  simplifile.write(to: path, contents: content)
+  |> result.map_error(fn(error) {
+    FileCouldNotBeWritten(path: path, reason: simplifile.describe_error(error))
+  })
 }
 
-type RawFileError
-
-fn map_raw_error(error: RawFileError) -> FileError {
-  case raw_file_error_kind(error) {
-    1 -> WidgetNameWasNotDeclared(path: raw_file_error_path(error))
-    2 -> WidgetXmlWasNotFound(path: raw_file_error_path(error))
-    3 ->
-      FileCouldNotBeRead(
-        path: raw_file_error_path(error),
-        reason: raw_file_error_reason(error),
-      )
-    4 ->
-      FileCouldNotBeWritten(
-        path: raw_file_error_path(error),
-        reason: raw_file_error_reason(error),
-      )
-    _ ->
-      FileCouldNotBeRead(
-        path: raw_file_error_path(error),
-        reason: raw_file_error_reason(error),
-      )
+fn widget_name(
+  package_contents: String,
+  package_path: String,
+) -> Result(String, FileError) {
+  case json.parse(package_contents, package_widget_name_decoder()) {
+    Error(error) ->
+      Error(FileCouldNotBeRead(
+        path: package_path,
+        reason: json_decode_error_reason(error),
+      ))
+    Ok(option.None) -> Error(WidgetNameWasNotDeclared(path: package_path))
+    Ok(option.Some(value)) ->
+      case decode.run(value, decode.string) {
+        Ok(name) ->
+          case string.trim(name) {
+            "" -> Error(WidgetNameWasNotDeclared(path: package_path))
+            _ -> Ok(name)
+          }
+        Error(_) -> Error(WidgetNameWasNotDeclared(path: package_path))
+      }
   }
 }
 
-// -- FFI --
-@external(javascript, "./file_boundary_ffi.mjs", "find_widget_xml")
-fn find_widget_xml_raw() -> Result(String, RawFileError)
-
-@external(javascript, "./file_boundary_ffi.mjs", "read_file")
-fn read_raw(path path: String) -> Result(String, RawFileError)
-
-@external(javascript, "./file_boundary_ffi.mjs", "write_file")
-fn write_raw(
-  path path: String,
-  content content: String,
-) -> Result(Nil, RawFileError)
-
-@external(javascript, "./file_boundary_ffi.mjs", "file_error_kind")
-fn raw_file_error_kind(error: RawFileError) -> Int
+fn package_widget_name_decoder() -> decode.Decoder(
+  option.Option(dynamic.Dynamic),
+) {
+  let object_decoder = {
+    use name <- decode.optional_field(
+      "widgetName",
+      option.None,
+      decode.optional(decode.dynamic),
+    )
+    decode.success(name)
+  }
+  decode.one_of(object_decoder, or: [decode.success(option.None)])
+}
 
-@external(javascript, "./file_boundary_ffi.mjs", "file_error_path")
-fn raw_file_error_path(error: RawFileError) -> String
+fn json_decode_error_reason(error: json.DecodeError) -> String {
+  case error {
+    json.UnexpectedEndOfInput -> "JSON ended unexpectedly"
+    json.UnexpectedByte(byte) -> "JSON contained unexpected byte: " <> byte
+    json.UnexpectedSequence(sequence) ->
+      "JSON contained unexpected sequence: " <> sequence
+    json.UnableToDecode(errors) -> {
+      let reasons =
+        errors
+        |> list.map(dynamic_decode_error_reason)
+        |> string.join("; ")
+      "JSON value could not be decoded: " <> reasons
+    }
+  }
+}
 
-@external(javascript, "./file_boundary_ffi.mjs", "file_error_reason")
-fn raw_file_error_reason(error: RawFileError) -> String
+fn dynamic_decode_error_reason(error: decode.DecodeError) -> String {
+  let decode.DecodeError(expected, found, path) = error
+  let location = case path {
+    [] -> "root"
+    [_, ..] -> string.join(path, ".")
+  }
+  location <> " expected " <> expected <> " but found " <> found
+}