fn string_push_char(str: string, value: int) -> string #[builtin(StringPushChar)] {}
fn string_char_at(str: string, index: int) -> int #[builtin(StringCharAt)] {}
fn string_length(str: string) -> int #[builtin(StringLength)] {}

fn string_array_new() -> [string] #[builtin(ArrayNew)] {}
fn string_array_push(array: [string], value: string) #[builtin(ArrayPush)] {}
fn string_array_length(array: [string]) -> int #[builtin(ArrayLength)] {}
fn string_array_at(array: [string], index: int) -> string #[builtin(ArrayAt)] {}

fn int_array_new() -> [int] #[builtin(ArrayNew)] {}
fn int_array_push(array: [int], value: int) #[builtin(ArrayPush)] {}
fn int_array_length(array: [int]) -> int #[builtin(ArrayLength)] {}
fn int_array_at(array: [int], index: int) -> int #[builtin(ArrayAt)] {}

fn file_open(filename: string, mode: string) -> int #[builtin(FileOpen)] {}
fn file_close(file: int) #[builtin(FileClose)] {}
fn file_write_string(file: int, content: string) -> int #[builtin(FileWriteString)] {}
fn file_read_char(file: int) -> int #[builtin(FileReadChar)] {}
fn file_read_to_string(file: int) -> string #[builtin(FileReadToString)] {}
fn file_flush(file: int) #[builtin(FileFlush)] {}
fn file_eof(file: int) -> bool #[builtin(FileEof)] {}

fn stdin() -> int { 0 }
fn stdout() -> int { 1 }
fn stderr() -> int { 2 }

fn file_read_line(file: int) -> string {
    let line = "";
    loop {
        if file_eof(file) {
            break;
        }
        let ch = file_read_char(file);
        if ch == "\n"[0] {
            break;
        }
        line = string_push_char(line, ch);
    }
    line
}

fn print(msg: string) #[builtin(Print)] {}
fn println(msg: string) { print(msg + "\n") }

fn input(prompt: string) -> string {
    print("> ");
    file_flush(stdout());
    file_read_line(stdin())
}