// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <zircon/assert.h>

#include "tools/kazoo/output_util.h"
#include "tools/kazoo/outputs.h"
#include "tools/kazoo/string_util.h"

namespace {

class Formatter {
 public:
  Formatter() = default;

  struct Names {
    std::string base_name;  // signals
    std::string type_name;  // zx_signals_t
  };

  Names Format(const Enum& e) {
    return Names{
        .base_name = e.base_name(),
        .type_name = "zx_" + e.base_name() + "_t",
    };
  }

  Names Format(const Struct& s) {
    return Names{
        .base_name = s.base_name(),
        .type_name = "zx_" + s.base_name() + "_t",
    };
  }

  Names Format(const Alias& alias) {
    return Names{
        .base_name = alias.base_name(),
        .type_name = "zx_" + alias.base_name() + "_t",
    };
  }

  std::string RustName(const Type& type) {
    struct {
     public:
      void operator()(const std::monostate&) { ret = "<TODO!>"; }
      void operator()(const TypeBool&) { ret = "u32"; }
      void operator()(const TypeChar&) { ret = "u8"; }
      void operator()(const TypeInt32&) { ret = "i32"; }
      void operator()(const TypeInt64&) { ret = "i64"; }
      void operator()(const TypeSizeT&) { ret = "usize"; }
      void operator()(const TypeUint16&) { ret = "u16"; }
      void operator()(const TypeUint32&) { ret = "u32"; }
      void operator()(const TypeUint64&) { ret = "u64"; }
      void operator()(const TypeUint8&) { ret = "u8"; }
      void operator()(const TypeVoid&) { ret = "u8"; }
      // TODO(syscall-fidl-transition): This is what abigen does, not sure if there's something
      // better that could be done.
      void operator()(const TypeUintptrT&) { ret = "usize"; }
      void operator()(const TypeZxBasicAlias& zx_basic_alias) { ret = zx_basic_alias.name(); }

      void operator()(const TypeAlias& alias) {
        ret = formatter->Format(alias.alias_data()).type_name;
      }
      void operator()(const TypeEnum& enm) { ret = formatter->Format(enm.enum_data()).type_name; }
      void operator()(const TypeHandle& handle) {
        ret = "zx_handle_t";
        // TOOD(syscall-fidl-transition): Once we're not trying to match abigen, it might be nice to
        // add the underlying handle type here like "zx_handle_t /*vmo*/" or similar.
      }
      void operator()(const TypePointer& pointer) {
        ret = StringPrintf("*%s %s", constness == Constness::kConst ? "const" : "mut",
                           formatter->RustName(pointer.pointed_to_type()).c_str());
      }
      void operator()(const TypeString&) {
        ZX_ASSERT(false && "can't convert string directly");
        ret = "<!>";
      }
      void operator()(const TypeStruct& strukt) {
        ret = formatter->Format(strukt.struct_data()).type_name;
      }
      void operator()(const TypeVector&) {
        ZX_ASSERT(false && "can't convert vector directly");
        ret = "<!>";
      }

      Constness constness;
      Formatter* formatter;
      std::string ret;
    } name_visitor;
    name_visitor.formatter = this;
    name_visitor.constness = type.constness();
    std::visit(name_visitor, type.type_data());
    return name_visitor.ret;
  }
};

}  // namespace

std::string mangle_identifier(std::string type) {
  // type is a reserved name in rustc
  if (type == "type") {
    return "ty";
  } else {
    return type;
  }
}

bool RustOutput(const SyscallLibrary& library, Writer* writer) {
  CopyrightHeaderWithCppComments(writer);

  Formatter formatter;
  constexpr const char indent[] = "    ";
  writer->Puts("// re-export the types defined in the fuchsia-zircon-types crate\n");
  writer->Puts("pub use fuchsia_zircon_types::*;\n");
  writer->Puts("// only link against zircon when targeting Fuchsia\n");
  writer->Puts("#[cfg(target_os = \"fuchsia\")]\n");
  writer->Puts("#[link(name = \"zircon\")]\n");
  writer->Puts("extern {\n");
  for (const auto& syscall : library.syscalls()) {
    if (syscall->HasAttribute("internal")) {
      continue;
    }

    writer->Printf("%spub fn zx_%s(\n", indent, syscall->name().c_str());
    for (size_t i = 0; i < syscall->kernel_arguments().size(); ++i) {
      const StructMember& arg = syscall->kernel_arguments()[i];
      const bool last = i == syscall->kernel_arguments().size() - 1;
      writer->Printf("%s%s%s: %s%s\n", indent, indent, mangle_identifier(arg.name()).c_str(),
                     formatter.RustName(arg.type()).c_str(), last ? "" : ",");
    }
    writer->Printf("%s%s)", indent, indent);
    if (!syscall->kernel_return_type().IsVoid()) {
      writer->Printf(" -> %s", formatter.RustName(syscall->kernel_return_type()).c_str());
    }
    writer->Puts(";\n\n");
  }
  writer->Puts("}\n");

  return true;
}