<?php
namespace metagen_go;
use Exception;

function get_twig(array $inc_path = [])
{
  array_unshift($inc_path, __DIR__ . "/../tpl/");
  $loader = new \Twig\Loader\FilesystemLoader($inc_path);

  $twig = new \Twig\Environment($loader, [
    'debug' => true, 
    'autoescape' => false, 
    'strict_variables' => true]
  );
  $twig->addExtension(new \Twig\Extension\DebugExtension());

  _add_twig_support($twig);

  return $twig;
}

function supported_tokens()
{
  return [
    'POD',
    'default',
    'optional',
    'bitfields',
    'cloneable',
    'virtual',

    'table',
    'id',
    'owner',
    'pkey',

    'statist',
    'statist_skip',
  ];
}

function _add_twig_support(\Twig\Environment $twig)
{
  $twig->addTest(new \Twig\TwigTest('instanceof', 
    function($obj, $class) 
    { 
      return (new \ReflectionClass($class))->isInstance($obj);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('Error', 
    function($e) 
    {
      throw new Exception($e);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('has_token', 
    function($o, $token) 
    { 
      return $o->hasToken($token);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('has_token_in_parent', 
    function($o, $token) 
    { 
      return $o->hasTokenInParent($token);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('token', 
    function($o, $name) 
    {
      return $o->getToken($name);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('token_or', 
    function($o, $name, $v) 
    {
      if($o->hasToken($name))
        return $o->getToken($name);
      else
        return $v;
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('get_all_fields', 
    function($meta, $o) 
    {
      return \mtg_get_all_fields($meta, $o);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('count_optional', 
    function($units) 
    {
      $opts = 0;
      foreach($units as $u)
        if($u->hasToken('optional'))
          ++$opts;
      return $opts;
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('buf2var', 
    function($name, $fname, $type, $buf, $tokens, $is_ptr)
    {
      return buf2var($name, $fname, $type, $buf, $tokens, $is_ptr);
    }
  ));
  $twig->addFunction(new \Twig\TwigFunction('var2buf', 
    function($name, $fname, $type, $buf, $tokens, $is_ptr)
    {
      return var2buf($name, $fname, $type, $buf, $tokens, $is_ptr);
    }
  ));
  $twig->addFilter(new \Twig\TwigFilter('go_type', 
    function($type, $tokens) 
    {
      return go_type($type, $tokens);
    }
  ));
  $twig->addFilter(new \Twig\TwigFilter('ucfirst', 
    function($str) 
    {
      return ucfirst($str);
    }
  ));
}

function go_type(\mtgType $type, array $tokens = array())
{
  if($type instanceof \mtgArrType)
  {
    $vtype = $type->getValue();

    $native = go_type($vtype);

    $str = "[]";
    if(array_key_exists("virtual", $tokens))
      $str .= "I";
    else
      $str .= $vtype instanceof \mtgMetaStruct ? "*" : "";

    $str .= $native;

    return $str;
  }
  else if($type instanceof \mtgBuiltinType)
  {
    if($type->isFloat())
      return "float32";
    else if($type->isDouble())
      return "float64";
    else if($type->isBlob())
      return "[]byte";
    else
      return $type->getName();
  }
  else if($type instanceof \mtgMetaEnum)
    return $type->getName();
  else if($type instanceof \mtgMetaStruct)
  {
    if(array_key_exists("virtual", $tokens))
      return "I{$type->getName()}";
    else
      return $type->getName();
  }
  else
    throw new Exception("Unknown type '$type'");
}

function builtin_type_prefix(\mtgBuiltinType $type)
{
  switch($type->getName())
  {
  case "string":
    return "String";
  case "bool":
    return "Bool";
  case "blob":
    return "Blob";
  case "float":
    return "Float";
  case "double":
    return "Double";
  case "uint64":
    return "U64";
  case "int64":
    return "I64";
  case "uint":
  case "uint32":
    return "U32";
  case "uint16":
    return "U16";
  case "uint8":
    return "U8";
  case "int":
  case "int32":
    return "I32";
  case "int16":
    return "I16";
  case "int8":
    return "I8";
  default:
    throw new Exception("Unknown type '{$type}'");
  }
}

function buf2var($name, $fname, \mtgType $type, $buf, array $tokens = array(), $is_ptr = false)
{
  $str = '';

  if($type instanceof \mtgBuiltinType)
  {
    $str .= _read_op($tokens, $buf.'.Read'.builtin_type_prefix($type).'(&'.$fname.', "'.$name.'")');
  }
  else if($type instanceof \mtgMetaEnum)
  {
    $str .= _read_op($tokens, "{$buf}.ReadI32((*int32)(&{$fname}), \"$name\")");
    $str .= "\n  if !{$fname}.IsValid() { return errors.Errorf(\"Bad enum value %d for $name\", $fname) }";
  }
  else if($type instanceof \mtgMetaStruct)
  {
    if(array_key_exists('virtual', $tokens))
      $str .= "if v, err := meta.ReadStructGeneric($buf, CreateById, \"{$name}\"); err != nil { return err } else { {$fname} = v.(I{$type}) }";
    else
      $str .= _read_op($tokens, "meta.ReadStruct($buf, ".($is_ptr?"":"&")."$fname, \"$name\")");
  }
  else if($type instanceof \mtgArrType)
  {
    $is_virtual = array_key_exists("virtual", $tokens);
    $native_type = go_type($type->getValue(), $tokens);
    $offset = "\n  ";
    $str .= "/*[]{$name}*/";
    $str .= $offset . _read_op($tokens, "{$buf}.BeginContainer(\"$name\")");
    //we don't want to propagate 'optionalness' below
    unset($tokens['optional']);
    $str .= $offset . "_{$name}_size, err := {$buf}.GetContainerSize()";
    $str .= $offset . "if err != nil { return err }";

    $need_new = !$is_virtual && $type->getValue() instanceof \mtgMetaStruct;

    $str .= $offset . "for ; _{$name}_size > 0; _{$name}_size-- {";
    $offset = "\n    ";
    $str .= $offset . "var tmp_{$name} {$native_type}";

    $str .= $offset . buf2var("", "tmp_{$name}", $type->getValue(), $buf, $tokens, $is_virtual);
    $str .= $offset . "{$fname} = append({$fname}, ".($need_new?"&":"")."tmp_{$name})";

    $offset = "\n  ";
    $str .= $offset . "}";
    $str .= $offset .  _read_op($tokens, "{$buf}.EndContainer()");
    $str .= "\n";
  }
  else
    throw new Exception("Unknown type '{$type}'");

  return $str;
}

function var2buf($name, $fname, \mtgType $type, $buf, array $tokens = array(), $is_ptr = false)
{
  $str = '';

  if($type instanceof \mtgBuiltinType)
  {
    $str .= _write_op("{$buf}.Write".builtin_type_prefix($type)."($fname, \"$name\")")."\n";
  }
  else if($type instanceof \mtgMetaEnum)
  {
    $str .= _write_op("{$buf}.WriteI32(int32($fname), \"$name\")");
  }
  else if($type instanceof \mtgMetaStruct)
  {
    if(array_key_exists('virtual', $tokens))
      $str .= _write_op("meta.WriteStructGeneric($buf, ".($is_ptr?"":"&")."$fname, \"$name\")");
    else
      $str .= _write_op("meta.WriteStruct($buf, ".($is_ptr?"":"&")."$fname, \"$name\")");
  }
  else if($type instanceof \mtgArrType)
  {
    $str .= "{$buf}.BeginContainer(\"{$name}\")\n";
    $str .= "  for _, v := range({$fname}) {\n";
    $str .= "    ".var2buf("", "v", $type->getValue(), $buf, $tokens, true)."\n";
    $str .= "  }\n";
    $str .= "  "._write_op("{$buf}.EndContainer()")."\n";
  }
  else
    throw new Exception("Unknown type '$type'");

  return $str;
}

function _write_op($op)
{
  return "if err := $op; err != nil { return err }";
}

function _read_op(array $tokens, $op)
{
  return "if err := $op; err != nil { return " . (array_key_exists("optional", $tokens) ? "/*optional*/nil" : "err"). " }";
}