import {
  S7WLBit, S7WLByte, S7WLWord, S7WLDWord, S7WLReal, S7WLCounter, S7WLTimer,
} from '../protocol/constants.js';

export function getByteCount(wordLen: number): number {
  switch (wordLen) {
    case S7WLBit:
    case S7WLByte: return 1;
    case S7WLWord:
    case S7WLCounter:
    case S7WLTimer: return 2;
    case S7WLDWord:
    case S7WLReal: return 4;
    default: return 0;
  }
}

export function getTransportSize(wordLen: number): number {
  switch (wordLen) {
    case S7WLBit: return 0x01;
    case S7WLByte: return 0x02;
    case S7WLWord: return 0x04;
    case S7WLDWord: return 0x06;
    case S7WLReal: return 0x08;
    case S7WLCounter: return 0x1C;
    case S7WLTimer: return 0x1D;
    default: return 0x00;
  }
}

export function readFixedString(buf: Buffer, offset: number, len: number): string {
  return buf.subarray(offset, offset + len).toString('ascii').replace(/\0+$/, '').trimEnd();
}

export function writeFixedString(buf: Buffer, offset: number, len: number, str: string): void {
  const strBuf = Buffer.alloc(len, 0x20); // pad with spaces
  Buffer.from(str, 'ascii').copy(strBuf, 0, 0, Math.min(str.length, len));
  strBuf.copy(buf, offset);
}

export function encodeS7Address(start: number, bitOffset: number, area: number, dbNumber: number, wordLen: number): Buffer {
  const transportSize = getTransportSize(wordLen);
  const buf = Buffer.alloc(12);
  buf[0] = 0x12; // Item spec
  buf[1] = 0x0A; // Item len
  buf[2] = 0x10; // Syntax ID S7Any
  buf[3] = transportSize;

  const isDB = area === 0x84;
  const numElements = wordLen === S7WLBit ? 1 : 1; // simplified, caller handles amount

  buf.writeUInt16BE(1, 4); // Number of elements (will be overwritten by caller)
  buf.writeUInt16BE(isDB ? dbNumber : 0, 6);
  buf[8] = area;

  // Address: Offset * 8 + BitOffset, 3 bytes big-endian
  const addr = start * 8 + bitOffset;
  buf[9] = (addr >> 16) & 0xFF;
  buf[10] = (addr >> 8) & 0xFF;
  buf[11] = addr & 0xFF;

  return buf;
}

export function s7DateToDate(year: number, month: number, day: number, hour: number, minute: number, second: number): Date {
  return new Date(year, month - 1, day, hour, minute, second);
}

export function dateToS7Date(d: Date): { year: number; month: number; day: number; hour: number; minute: number; second: number } {
  return {
    year: d.getFullYear(),
    month: d.getMonth() + 1,
    day: d.getDate(),
    hour: d.getHours(),
    minute: d.getMinutes(),
    second: d.getSeconds(),
  };
}