// Parser: turn the line-based point-table text into a Device.
//
// Point table format (one register per line, `#` starts a comment):
//    
   [] []
// Example:
//   coil_temp  40001 float32 R  degC  jsonb->coil_temp
//   conveyor   40003 bool    RW        jsonb->conveyor_run
//
// The Modbus area (coil / discrete input / input register / holding register)
// is inferred from the address prefix, so no extra header is required.

///|
/// Parse a whole point-table document.
pub fn parse_device(text : String) -> Result[Device, String] {
  let lines = split_lines(text)
  let regs : Array[Register] = []
  for i = 0; i < lines.length(); i = i + 1 {
    let raw = lines[i].trim().to_owned()
    if raw.length() == 0 {
      continue
    }
    if raw[0] == '#' {
      continue
    }
    let r = match parse_line(raw, i + 1) {
      Ok(v) => v
      Err(e) => return Err(e)
    }
    regs.push(r)
  }
  Ok({ registers: regs, })
}

///|
/// Parse a single register line.
fn parse_line(line : String, line_no : Int) -> Result[Register, String] {
  let toks = split_ws(line)
  if toks.length() < 4 {
    return Err(
      "line " +
      line_no.to_string() +
      ": expected '    [unit] [jsonb]', got " +
      toks.length().to_string() +
      " field(s)",
    )
  }
  let name = toks[0]
  let addr = match parse_int(toks[1]) {
    Ok(v) => v
    Err(e) => return Err("line " + line_no.to_string() + ": bad address: " + e)
  }
  let rtype = match parse_type(toks[2]) {
    Ok(v) => v
    Err(e) => return Err("line " + line_no.to_string() + ": " + e)
  }
  let access = match parse_access(toks[3]) {
    Ok(v) => v
    Err(e) => return Err("line " + line_no.to_string() + ": " + e)
  }
  let unit = if toks.length() > 4 { toks[4] } else { "" }
  let jsonb = if toks.length() > 5 { toks[5] } else { "" }
  Ok({ name, address: addr, rtype, access, unit, jsonb, line: line_no, })
}

///|
test "parse_device reads comments and registers" {
  let text = "# example point table\n" +
    "coil_temp 40001 float32 R degC jsonb->coil_temp\n" +
    "\n" +
    "conveyor  40003 bool RW jsonb->conveyor_run\n"
  let dev = parse_device(text).unwrap()
  assert_eq(dev.registers.length(), 2)
  assert_eq(dev.registers[0].name, "coil_temp")
  assert_eq(dev.registers[1].address, 40003)
}

///|
test "parse_device rejects unknown type" {
  let res = parse_device("x 40001 unknown R")
  assert_eq(res is Ok(_), false)
}

///|
test "parse_device rejects too-few fields" {
  let res = parse_device("x 40001 float32")
  assert_eq(res is Ok(_), false)
}