#include "settings.h"

#include <SD.h>

extern "C" {
#include <lauxlib.h>
#include <lua.h>
}

Settings settings;

static constexpr const char* PATH = "/settings.lua";
static constexpr const char* TEMP_PATH = "/settings.tmp";
static constexpr const char* BACKUP_PATH = "/settings.bak";

static int16_t fieldOr(lua_State* L, const char* key, int16_t fallback) {
  lua_getfield(L, -1, key);
  int16_t value = lua_isinteger(L, -1) ? lua_tointeger(L, -1) : fallback;
  lua_pop(L, 1);
  return value;
}

static String stringFieldOr(lua_State* L, const char* key,
                            const String& fallback) {
  lua_getfield(L, -1, key);
  String value = lua_isstring(L, -1) ? lua_tostring(L, -1) : fallback;
  lua_pop(L, 1);
  return value;
}

static String luaString(const String& value) {
  String out = "\"";
  for (size_t i = 0; i < value.length(); i++) {
    unsigned char c = value[i];
    if (c == '\\' || c == '\"') {
      out += '\\';
      out += (char)c;
    } else if (c >= 32 && c < 127) {
      out += (char)c;
    } else {
      char escaped[5];
      snprintf(escaped, sizeof(escaped), "\\%03u", c);
      out += escaped;
    }
  }
  out += '\"';
  return out;
}

bool Settings::setRotation(int16_t degrees) {
  if (degrees % 90 != 0 || degrees < 0 || degrees > 270)
    return false;
  rotation = degrees;
  return true;
}

bool Settings::load() {
  File f = SD.open(PATH);
  if (!f)
    return false;
  String source = f.readString();
  f.close();

  lua_State* L = luaL_newstate();
  if (!L)
    return false;
  bool ok =
      luaL_loadbuffer(L, source.c_str(), source.length(), PATH) == LUA_OK &&
      lua_pcall(L, 0, 1, 0) == LUA_OK && lua_istable(L, -1);
  if (ok) {
    rotation = fieldOr(L, "rotation", rotation);
    timezone = stringFieldOr(L, "timezone", timezone);
    theme = stringFieldOr(L, "theme", theme);
    lua_getfield(L, -1, "touch");
    if (lua_istable(L, -1)) {
      touchX0 = fieldOr(L, "x0", touchX0);
      touchY0 = fieldOr(L, "y0", touchY0);
      touchX1 = fieldOr(L, "x1", touchX1);
      touchY1 = fieldOr(L, "y1", touchY1);
    }
    lua_pop(L, 1);
    lua_getfield(L, -1, "wifi");
    if (lua_istable(L, -1)) {
      wifiSsid = stringFieldOr(L, "ssid", wifiSsid);
      wifiPassword = stringFieldOr(L, "password", wifiPassword);
    }
    lua_pop(L, 1);
  }
  lua_close(L);
  return ok;
}

bool Settings::save() const {
  String source = "return {\n  rotation = " + String(rotation) + ",\n";
  source += "  timezone = " + luaString(timezone) + ",\n";
  source += "  theme = " + luaString(theme) + ",\n";
  source += "  touch = { x0 = " + String(touchX0) +
            ", y0 = " + String(touchY0) + ", x1 = " + String(touchX1) +
            ", y1 = " + String(touchY1) + " },\n";
  source += "  wifi = { ssid = " + luaString(wifiSsid) +
            ", password = " + luaString(wifiPassword) + " },\n}\n";

  if (SD.exists(TEMP_PATH))
    SD.remove(TEMP_PATH);
  File f = SD.open(TEMP_PATH, FILE_WRITE);
  if (!f)
    return false;
  bool ok = f.write(reinterpret_cast<const uint8_t*>(source.c_str()),
                    source.length()) == source.length();
  f.close();
  if (!ok) {
    SD.remove(TEMP_PATH);
    return false;
  }
  if (SD.exists(BACKUP_PATH))
    SD.remove(BACKUP_PATH);
  bool hadSettings = SD.exists(PATH);
  if (hadSettings && !SD.rename(PATH, BACKUP_PATH))
    return false;
  if (SD.rename(TEMP_PATH, PATH)) {
    if (hadSettings)
      SD.remove(BACKUP_PATH);
    return true;
  }
  if (hadSettings)
    SD.rename(BACKUP_PATH, PATH);
  return false;
}