#include <algorithm>
#include <limits.h>  // PATH_MAX
#include <sys/stat.h>  // S_IFDIR
#include "module_wrap.h"

#include "env.h"
#include "node_url.h"
#include "util.h"
#include "util-inl.h"

namespace node {
namespace loader {

using node::url::URL;
using node::url::URL_FLAGS_FAILED;
using v8::Context;
using v8::EscapableHandleScope;
using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Integer;
using v8::IntegrityLevel;
using v8::Isolate;
using v8::JSON;
using v8::Local;
using v8::Maybe;
using v8::MaybeLocal;
using v8::Module;
using v8::Object;
using v8::Promise;
using v8::ScriptCompiler;
using v8::ScriptOrigin;
using v8::String;
using v8::Value;

static const char* const EXTENSIONS[] = {".mjs", ".js", ".json", ".node"};

ModuleWrap::ModuleWrap(Environment* env,
                       Local<Object> object,
                       Local<Module> module,
                       Local<String> url) : BaseObject(env, object) {
  module_.Reset(env->isolate(), module);
  url_.Reset(env->isolate(), url);
}

ModuleWrap::~ModuleWrap() {
  HandleScope scope(env()->isolate());
  Local<Module> module = module_.Get(env()->isolate());
  auto range = env()->module_map.equal_range(module->GetIdentityHash());
  for (auto it = range.first; it != range.second; ++it) {
    if (it->second == this) {
      env()->module_map.erase(it);
      break;
    }
  }

  module_.Reset();
}

void ModuleWrap::New(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);

  Isolate* iso = args.GetIsolate();

  if (!args.IsConstructCall()) {
    env->ThrowError("constructor must be called using new");
    return;
  }

  if (args.Length() != 2) {
    env->ThrowError("constructor must have exactly 2 arguments "
                    "(string, string)");
    return;
  }

  if (!args[0]->IsString()) {
    env->ThrowError("first argument is not a string");
    return;
  }

  auto source_text = args[0].As<String>();

  if (!args[1]->IsString()) {
    env->ThrowError("second argument is not a string");
    return;
  }

  Local<String> url = args[1].As<String>();

  Local<Module> mod;

  // compile
  {
    ScriptOrigin origin(url,
                        Integer::New(iso, 0),
                        Integer::New(iso, 0),
                        False(iso),
                        Integer::New(iso, 0),
                        FIXED_ONE_BYTE_STRING(iso, ""),
                        False(iso),
                        False(iso),
                        True(iso));
    ScriptCompiler::Source source(source_text, origin);
    auto maybe_mod = ScriptCompiler::CompileModule(iso, &source);
    if (maybe_mod.IsEmpty()) {
        return;
    }
    mod = maybe_mod.ToLocalChecked();
  }

  auto that = args.This();
  auto ctx = that->CreationContext();
  auto url_str = FIXED_ONE_BYTE_STRING(iso, "url");

  if (!that->Set(ctx, url_str, url).FromMaybe(false)) {
    return;
  }

  ModuleWrap* obj =
      new ModuleWrap(Environment::GetCurrent(ctx), that, mod, url);

  env->module_map.emplace(mod->GetIdentityHash(), obj);
  Wrap(that, obj);

  that->SetIntegrityLevel(ctx, IntegrityLevel::kFrozen);
  args.GetReturnValue().Set(that);
}

void ModuleWrap::Link(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* iso = args.GetIsolate();
  EscapableHandleScope handle_scope(iso);
  if (!args[0]->IsFunction()) {
    env->ThrowError("first argument is not a function");
    return;
  }

  Local<Function> resolver_arg = args[0].As<Function>();

  auto that = args.This();
  ModuleWrap* obj = Unwrap<ModuleWrap>(that);
  auto mod_context = that->CreationContext();
  if (obj->linked_) return;
  obj->linked_ = true;
  Local<Module> mod(obj->module_.Get(iso));

  // call the dependency resolve callbacks
  for (int i = 0; i < mod->GetModuleRequestsLength(); i++) {
    Local<String> specifier = mod->GetModuleRequest(i);
    Utf8Value specifier_utf(env->isolate(), specifier);
    std::string specifier_std(*specifier_utf, specifier_utf.length());

    Local<Value> argv[] = {
      specifier
    };

    MaybeLocal<Value> maybe_resolve_return_value =
        resolver_arg->Call(mod_context, that, 1, argv);
    if (maybe_resolve_return_value.IsEmpty()) {
      return;
    }
    Local<Value> resolve_return_value =
        maybe_resolve_return_value.ToLocalChecked();
    if (!resolve_return_value->IsPromise()) {
      env->ThrowError("linking error, expected resolver to return a promise");
    }
    Local<Promise> resolve_promise = resolve_return_value.As<Promise>();
    obj->resolve_cache_[specifier_std].Reset(env->isolate(), resolve_promise);
  }

  args.GetReturnValue().Set(handle_scope.Escape(that));
}

void ModuleWrap::Instantiate(const FunctionCallbackInfo<Value>& args) {
  auto iso = args.GetIsolate();
  auto that = args.This();
  auto ctx = that->CreationContext();

  ModuleWrap* obj = Unwrap<ModuleWrap>(that);
  Local<Module> mod = obj->module_.Get(iso);
  Maybe<bool> ok = mod->InstantiateModule(ctx, ModuleWrap::ResolveCallback);

  // clear resolve cache on instantiate
  for (auto& entry : obj->resolve_cache_)
    entry.second.Reset();
  obj->resolve_cache_.clear();

  if (!ok.FromMaybe(false)) {
    return;
  }
}

void ModuleWrap::Evaluate(const FunctionCallbackInfo<Value>& args) {
  auto iso = args.GetIsolate();
  auto that = args.This();
  auto ctx = that->CreationContext();
  ModuleWrap* obj = Unwrap<ModuleWrap>(that);
  auto result = obj->module_.Get(iso)->Evaluate(ctx);

  if (result.IsEmpty()) {
    return;
  }

  auto ret = result.ToLocalChecked();
  args.GetReturnValue().Set(ret);
}

MaybeLocal<Module> ModuleWrap::ResolveCallback(Local<Context> context,
                                               Local<String> specifier,
                                               Local<Module> referrer) {
  Environment* env = Environment::GetCurrent(context);
  Isolate* iso = Isolate::GetCurrent();
  if (env->module_map.count(referrer->GetIdentityHash()) == 0) {
    env->ThrowError("linking error, unknown module");
    return MaybeLocal<Module>();
  }

  ModuleWrap* dependent = nullptr;
  auto range = env->module_map.equal_range(referrer->GetIdentityHash());
  for (auto it = range.first; it != range.second; ++it) {
    if (it->second->module_ == referrer) {
      dependent = it->second;
      break;
    }
  }

  if (dependent == nullptr) {
    env->ThrowError("linking error, null dep");
    return MaybeLocal<Module>();
  }

  Utf8Value specifier_utf(env->isolate(), specifier);
  std::string specifier_std(*specifier_utf, specifier_utf.length());

  if (dependent->resolve_cache_.count(specifier_std) != 1) {
    env->ThrowError("linking error, not in local cache");
    return MaybeLocal<Module>();
  }

  Local<Promise> resolve_promise =
      dependent->resolve_cache_[specifier_std].Get(iso);

  if (resolve_promise->State() != Promise::kFulfilled) {
    env->ThrowError("linking error, dependency promises must be resolved on "
                    "instantiate");
    return MaybeLocal<Module>();
  }

  auto module_object = resolve_promise->Result().As<Object>();
  if (module_object.IsEmpty() || !module_object->IsObject()) {
    env->ThrowError("linking error, expected a valid module object from "
                    "resolver");
    return MaybeLocal<Module>();
  }

  ModuleWrap* mod;
  ASSIGN_OR_RETURN_UNWRAP(&mod, module_object, MaybeLocal<Module>());
  return mod->module_.Get(env->isolate());
}

namespace {

URL __init_cwd() {
  std::string specifier = "file://";
#ifdef _WIN32
  // MAX_PATH is in characters, not bytes. Make sure we have enough headroom.
  char buf[MAX_PATH * 4];
#else
  char buf[PATH_MAX];
#endif

  size_t cwd_len = sizeof(buf);
  int err = uv_cwd(buf, &cwd_len);
  if (err) {
    return URL("");
  }
  specifier += buf;
  specifier += "/";
  return URL(specifier);
}
static URL INITIAL_CWD(__init_cwd());
inline bool is_relative_or_absolute_path(std::string specifier) {
  auto len = specifier.length();
  if (len <= 0) {
    return false;
  } else if (specifier[0] == '/') {
    return true;
  } else if (specifier[0] == '.') {
    if (len == 1 || specifier[1] == '/') {
      return true;
    } else if (specifier[1] == '.') {
      if (len == 2 || specifier[2] == '/') {
        return true;
      }
    }
  }
  return false;
}
struct read_result {
  bool had_error = false;
  std::string source;
} read_result;
inline const struct read_result read_file(uv_file file) {
  struct read_result ret;
  std::string src;
  uv_fs_t req;
  void* base = malloc(4096);
  if (base == nullptr) {
    ret.had_error = true;
    return ret;
  }
  uv_buf_t buf = uv_buf_init(static_cast<char*>(base), 4096);
  uv_fs_read(uv_default_loop(), &req, file, &buf, 1, 0, nullptr);
  while (req.result > 0) {
    src += std::string(static_cast<const char*>(buf.base), req.result);
    uv_fs_read(uv_default_loop(), &req, file, &buf, 1, src.length(), nullptr);
  }
  ret.source = src;
  return ret;
}
struct file_check {
  bool failed = true;
  uv_file file = -1;
};
inline const struct file_check check_file(URL search,
                                          bool close = false,
                                          bool allow_dir = false) {
  struct file_check ret;
  uv_fs_t fs_req;
  std::string path = search.ToFilePath();
  if (path.empty()) {
    return ret;
  }
  uv_fs_open(nullptr, &fs_req, path.c_str(), O_RDONLY, 0, nullptr);
  auto fd = fs_req.result;
  if (fd < 0) {
    return ret;
  }
  if (!allow_dir) {
    uv_fs_fstat(nullptr, &fs_req, fd, nullptr);
    if (fs_req.statbuf.st_mode & S_IFDIR) {
      uv_fs_close(nullptr, &fs_req, fd, nullptr);
      return ret;
    }
  }
  ret.failed = false;
  ret.file = fd;
  if (close) uv_fs_close(nullptr, &fs_req, fd, nullptr);
  return ret;
}
URL resolve_extensions(URL search, bool check_exact = true) {
  if (check_exact) {
    auto check = check_file(search, true);
    if (!check.failed) {
      return search;
    }
  }
  for (auto extension : EXTENSIONS) {
    URL guess(search.path() + extension, &search);
    auto check = check_file(guess, true);
    if (!check.failed) {
      return guess;
    }
  }
  return URL("");
}
inline URL resolve_index(URL search) {
  return resolve_extensions(URL("index", &search), false);
}
URL resolve_main(URL search) {
  URL pkg("package.json", &search);
  auto check = check_file(pkg);
  if (!check.failed) {
    auto iso = Isolate::GetCurrent();
    auto ctx = iso->GetCurrentContext();
    auto read = read_file(check.file);
    uv_fs_t fs_req;
    // if we fail to close :-/
    uv_fs_close(nullptr, &fs_req, check.file, nullptr);
    if (read.had_error) return URL("");
    std::string pkg_src = read.source;
    Local<String> src =
        String::NewFromUtf8(iso, pkg_src.c_str(),
                            String::kNormalString, pkg_src.length());
    if (src.IsEmpty()) return URL("");
    auto maybe_pkg_json = JSON::Parse(ctx, src);
    if (maybe_pkg_json.IsEmpty()) return URL("");
    auto pkg_json_obj = maybe_pkg_json.ToLocalChecked().As<Object>();
    if (!pkg_json_obj->IsObject()) return URL("");
    auto maybe_pkg_main = pkg_json_obj->Get(
        ctx, FIXED_ONE_BYTE_STRING(iso, "main"));
    if (maybe_pkg_main.IsEmpty()) return URL("");
    auto pkg_main_str = maybe_pkg_main.ToLocalChecked().As<String>();
    if (!pkg_main_str->IsString()) return URL("");
    Utf8Value main_utf8(iso, pkg_main_str);
    std::string main_std(*main_utf8, main_utf8.length());
    if (!is_relative_or_absolute_path(main_std)) {
      main_std.insert(0, "./");
    }
    return Resolve(main_std, &search);
  }
  return URL("");
}
URL resolve_module(std::string specifier, URL* base) {
  URL parent(".", base);
  URL dir("");
  do {
    dir = parent;
    auto check = Resolve("./node_modules/" + specifier, &dir, true);
    if (!(check.flags() & URL_FLAGS_FAILED)) {
      const auto limit = specifier.find('/');
      const auto spec_len = limit == std::string::npos ?
                                specifier.length() :
                                limit + 1;
      std::string chroot =
          dir.path() + "node_modules/" + specifier.substr(0, spec_len);
      if (check.path().substr(0, chroot.length()) != chroot) {
        return URL("");
      }
      return check;
    } else {
      // TODO(bmeck) PREVENT FALLTHROUGH
    }
    parent = URL("..", &dir);
  } while (parent.path() != dir.path());
  return URL("");
}

URL resolve_directory(URL search, bool read_pkg_json) {
  if (read_pkg_json) {
    auto main = resolve_main(search);
    if (!(main.flags() & URL_FLAGS_FAILED)) return main;
  }
  return resolve_index(search);
}

}  // anonymous namespace


URL Resolve(std::string specifier, URL* base, bool read_pkg_json) {
  URL pure_url(specifier);
  if (!(pure_url.flags() & URL_FLAGS_FAILED)) {
    return pure_url;
  }
  if (specifier.length() == 0) {
    return URL("");
  }
  if (is_relative_or_absolute_path(specifier)) {
    URL resolved(specifier, base);
    auto file = resolve_extensions(resolved);
    if (!(file.flags() & URL_FLAGS_FAILED)) return file;
    if (specifier.back() != '/') {
      resolved = URL(specifier + "/", base);
    }
    return resolve_directory(resolved, read_pkg_json);
  } else {
    return resolve_module(specifier, base);
  }
  UNREACHABLE();
}

void ModuleWrap::Resolve(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);

  if (args.IsConstructCall()) {
    env->ThrowError("resolve() must not be called as a constructor");
    return;
  }
  if (args.Length() != 2) {
    env->ThrowError("resolve must have exactly 2 arguments (string, string)");
    return;
  }

  if (!args[0]->IsString()) {
    env->ThrowError("first argument is not a string");
    return;
  }
  Utf8Value specifier_utf(env->isolate(), args[0]);

  if (!args[1]->IsString()) {
    env->ThrowError("second argument is not a string");
    return;
  }
  Utf8Value url_utf(env->isolate(), args[1]);
  URL url(*url_utf, url_utf.length());

  if (url.flags() & URL_FLAGS_FAILED) {
    env->ThrowError("second argument is not a URL string");
    return;
  }

  URL result = node::loader::Resolve(*specifier_utf, &url, true);
  if (result.flags() & URL_FLAGS_FAILED) {
    std::string msg = "module ";
    msg += *specifier_utf;
    msg += " not found";
    env->ThrowError(msg.c_str());
    return;
  }

  args.GetReturnValue().Set(result.ToObject(env));
}

void ModuleWrap::Initialize(Local<Object> target,
                           Local<Value> unused,
                           Local<Context> context) {
  Environment* env = Environment::GetCurrent(context);
  Isolate* isolate = env->isolate();

  Local<FunctionTemplate> tpl = env->NewFunctionTemplate(New);
  tpl->SetClassName(FIXED_ONE_BYTE_STRING(isolate, "ModuleWrap"));
  tpl->InstanceTemplate()->SetInternalFieldCount(1);

  env->SetProtoMethod(tpl, "link", Link);
  env->SetProtoMethod(tpl, "instantiate", Instantiate);
  env->SetProtoMethod(tpl, "evaluate", Evaluate);

  target->Set(FIXED_ONE_BYTE_STRING(isolate, "ModuleWrap"), tpl->GetFunction());
  env->SetMethod(target, "resolve", node::loader::ModuleWrap::Resolve);
}

}  // namespace loader
}  // namespace node

NODE_MODULE_CONTEXT_AWARE_BUILTIN(module_wrap,
                                  node::loader::ModuleWrap::Initialize)