feat: main code

src/simple_repl.gleam

@@ -0,0 +1,74 @@
+import gleam/dict
+import gleam/io
+import gleam/string
+import simplifile
+
+const history_file = ".history"
+
+@external(erlang, "io", "get_line")
+fn get_line(prompt: String) -> String
+
+@external(erlang, "erlang", "halt")
+fn halt(code: Int) -> Nil
+
+fn clean() {
+  case simplifile.delete(history_file) {
+    Ok(Nil) -> Nil
+    Error(e) -> io.println(simplifile.describe_error(e))
+  }
+}
+
+fn history() {
+  case simplifile.read(history_file) {
+    Ok(content) -> io.print(content)
+    Error(e) -> io.println(simplifile.describe_error(e))
+  }
+}
+
+fn help() -> Nil {
+  io.println("help: print this message")
+  io.println("history: dump history")
+  io.println("clean: delete history")
+  io.println("exit: quit the program")
+}
+
+fn exit() -> Nil {
+  halt(0)
+}
+
+fn commands() -> dict.Dict(String, fn() -> Nil) {
+  dict.from_list([
+    #("clean", clean),
+    #("help", help),
+    #("history", history),
+    #("exit", exit),
+  ])
+}
+
+fn append_history(cmd: String) -> Nil {
+  case simplifile.append(history_file, cmd <> "\n") {
+    Ok(Nil) -> Nil
+    Error(e) -> io.println(simplifile.describe_error(e))
+  }
+}
+
+fn repl_loop() -> a {
+  let cmd = get_line("repl> ") |> string.trim
+  cmd |> append_history
+  case dict.get(commands(), cmd) {
+    Ok(func) -> func()
+    Error(_) -> io.println(cmd <> ": unknown command")
+  }
+  repl_loop()
+}
+
+pub fn main() -> Nil {
+  case simplifile.is_file(history_file) {
+    Ok(True) -> repl_loop()
+    _ ->
+      case simplifile.create_file(history_file) {
+        Ok(Nil) -> repl_loop()
+        Error(e) -> io.println(simplifile.describe_error(e))
+      }
+  }
+}