#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#include <v8.h>
#include <vector>

#include "js_shell.h"

typedef int (*V8ExtensionRegistrar) (v8::Handle<v8::Context>);

class V8Shell: public JSShell {

public:
    V8Shell();
    
    virtual ~V8Shell();

protected:

  virtual bool RegisterModule(HANDLE library, const std::string& module_name);

  virtual bool InitializeEngine();
  
  virtual bool ExecuteScript(const std::string& source, const std::string& name);

  virtual bool DisposeEngine();
  
private:

  v8::Persistent<v8::Context> CreateShellContext();

  void ReportException(v8::TryCatch* handler);

  static v8::Handle<v8::Value> Print(const v8::Arguments& args);

  static v8::Handle<v8::Value> Quit(const v8::Arguments& args);

  static v8::Handle<v8::Value> Version(const v8::Arguments& args);

  static const char* ToCString(const v8::String::Utf8Value& value);
    
protected:

  std::vector<V8ExtensionRegistrar> module_initializers;
  
  v8::Persistent<v8::Context> context;

};

#ifdef __GNUC__
#include <dlfcn.h>
#define LOAD_SYMBOL(handle, name) dlsym(handle, name)
#else
#error "implement dll loading"
#endif

V8Shell::V8Shell()
{
}

V8Shell::~V8Shell() {
  context.Dispose();
  v8::V8::Dispose();
}

bool V8Shell::RegisterModule(HANDLE library, const std::string& module_name) {
    std::string symname = std::string(module_name).append("_initialize");
    
    V8ExtensionRegistrar init_function = reinterpret_cast<V8ExtensionRegistrar>((long) LOAD_SYMBOL(library, symname.c_str()));
    if(init_function == 0) return false;

    module_initializers.push_back(init_function);
    return true;
}

bool V8Shell::InitializeEngine() {
  if (!context.IsEmpty()) {
    context.Dispose();
  }

  context = CreateShellContext(); 
  if (context.IsEmpty()) {
      printf("Could not create context.\n");
      return 1;
  }
  
  context->Enter();
}

bool V8Shell::ExecuteScript(const std::string& source, const std::string& name) {
  // Enter the execution environment before evaluating any code.
  v8::Context::Scope context_scope(context);

  v8::HandleScope handle_scope;
  v8::TryCatch try_catch;
  v8::Handle<v8::Script> script = v8::Script::Compile(v8::String::New(source.c_str()), v8::String::New(name.c_str()));
  if (script.IsEmpty()) {
    // Print errors that happened during compilation.
    ReportException(&try_catch);
    return false;
  } else {
    v8::Handle<v8::Value> result = script->Run();
    if (result.IsEmpty()) {
      assert(try_catch.HasCaught());
      // Print errors that happened during execution.
      ReportException(&try_catch);
      return false;
    } else {
      assert(!try_catch.HasCaught());
      if (!result->IsUndefined()) {
        // If all went well and the result wasn't undefined then print
        // the returned value.
        v8::String::Utf8Value str(result);
        const char* cstr = V8Shell::ToCString(str);
        printf("%s\n", cstr);
      }
      return true;
    }
  }
}

bool V8Shell::DisposeEngine() {
  context->Exit();
  context.Dispose();
  v8::V8::Dispose();
}

v8::Persistent<v8::Context> V8Shell::CreateShellContext() {
  // Create a template for the global object.
  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New();

  // Bind global functions
  global->Set(v8::String::New("print"), v8::FunctionTemplate::New(V8Shell::Print));
  global->Set(v8::String::New("quit"), v8::FunctionTemplate::New(V8Shell::Quit));
  global->Set(v8::String::New("version"), v8::FunctionTemplate::New(V8Shell::Version));

  v8::Persistent<v8::Context> _context = v8::Context::New(NULL, global);
  
  // register extensions
  for(std::vector<V8ExtensionRegistrar>::iterator it=module_initializers.begin();
    it != module_initializers.end(); ++it) {
    (*it)(_context);
  }

  return _context;
}


v8::Handle<v8::Value> V8Shell::Print(const v8::Arguments& args) {
  bool first = true;
  for (int i = 0; i < args.Length(); i++) {
    v8::HandleScope handle_scope;
    if (first) {
      first = false;
    } else {
      printf(" ");
    }
    v8::String::Utf8Value str(args[i]);
    const char* cstr = V8Shell::ToCString(str);
    printf("%s", cstr);
  }
  printf("\n");
  fflush(stdout);
  return v8::Undefined();
}

v8::Handle<v8::Value> V8Shell::Quit(const v8::Arguments& args) {
  int exit_code = args[0]->Int32Value();
  fflush(stdout);
  fflush(stderr);
  exit(exit_code);
  return v8::Undefined();
}

v8::Handle<v8::Value> V8Shell::Version(const v8::Arguments& args) {
  return v8::String::New(v8::V8::GetVersion());
}

void V8Shell::ReportException(v8::TryCatch* try_catch) {
  v8::HandleScope handle_scope;
  v8::String::Utf8Value exception(try_catch->Exception());
  const char* exception_string = V8Shell::ToCString(exception);
  v8::Handle<v8::Message> message = try_catch->Message();
  if (message.IsEmpty()) {
    // V8 didn't provide any extra information about this error; just
    // print the exception.
    printf("%s\n", exception_string);
  } else {
    // Print (filename):(line number): (message).
    v8::String::Utf8Value filename(message->GetScriptResourceName());
    const char* filename_string = V8Shell::ToCString(filename);
    int linenum = message->GetLineNumber();
    printf("%s:%i: %s\n", filename_string, linenum, exception_string);
    // Print line of source code.
    v8::String::Utf8Value sourceline(message->GetSourceLine());
    const char* sourceline_string = V8Shell::ToCString(sourceline);
    printf("%s\n", sourceline_string);
    // Print wavy underline (GetUnderline is deprecated).
    int start = message->GetStartColumn();
    for (int i = 0; i < start; i++) {
      printf(" ");
    }
    int end = message->GetEndColumn();
    for (int i = start; i < end; i++) {
      printf("^");
    }
    printf("\n");
    v8::String::Utf8Value stack_trace(try_catch->StackTrace());
    if (stack_trace.length() > 0) {
      const char* stack_trace_string = V8Shell::ToCString(stack_trace);
      printf("%s\n", stack_trace_string);
    }
  }
}

// Extracts a C string from a V8 Utf8Value.
const char* V8Shell::ToCString(const v8::String::Utf8Value& value) {
  return *value ? *value : "<string conversion failed>";
}