// Copyright (c) 2006-2008 The Chromium 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 "chrome/browser/ime_input.h"

#include "base/scoped_ptr.h"
#include "base/string_util.h"

// "imm32.lib" is required by IMM32 APIs used in this file.
// NOTE(hbono): To comply with a comment from Darin, I have added
// this #pragma directive instead of adding "imm32.lib" to a project file.
#pragma comment(lib, "imm32.lib")

///////////////////////////////////////////////////////////////////////////////
// ImeInput

ImeInput::ImeInput()
    : ime_status_(false),
      input_language_id_(LANG_USER_DEFAULT),
      is_composing_(false),
      system_caret_(false),
      caret_rect_(-1, -1, 0, 0) {
}

ImeInput::~ImeInput() {
}

bool ImeInput::SetInputLanguage() {
  // Retrieve the current keyboard layout from Windows and determine whether
  // or not the current input context has IMEs.
  // Also save its input language for language-specific operations required
  // while composing a text.
  HKL keyboard_layout = ::GetKeyboardLayout(0);
  input_language_id_ = reinterpret_cast<LANGID>(keyboard_layout);
  ime_status_ = (::ImmIsIME(keyboard_layout) == TRUE) ? true : false;
  return ime_status_;
}


void ImeInput::CreateImeWindow(HWND window_handle) {
  // When a user disables TSF (Text Service Framework) and CUAS (Cicero
  // Unaware Application Support), Chinese IMEs somehow ignore function calls
  // to ::ImmSetCandidateWindow(), i.e. they do not move their candidate
  // window to the position given as its parameters, and use the position
  // of the current system caret instead, i.e. it uses ::GetCaretPos() to
  // retrieve the position of their IME candidate window.
  // Therefore, we create a temporary system caret for Chinese IMEs and use
  // it during this input context.
  // Since some third-party Japanese IME also uses ::GetCaretPos() to determine
  // their window position, we also create a caret for Japanese IMEs.
  if (PRIMARYLANGID(input_language_id_) == LANG_CHINESE ||
      PRIMARYLANGID(input_language_id_) == LANG_JAPANESE) {
    if (!system_caret_) {
      if (::CreateCaret(window_handle, NULL, 1, 1)) {
        system_caret_ = true;
      }
    }
  }
  // Restore the positions of the IME windows.
  UpdateImeWindow(window_handle);
}

void ImeInput::SetImeWindowStyle(HWND window_handle, UINT message,
                                 WPARAM wparam, LPARAM lparam,
                                 BOOL* handled) {
  // To prevent the IMM (Input Method Manager) from displaying the IME
  // composition window, Update the styles of the IME windows and EXPLICITLY
  // call ::DefWindowProc() here.
  // NOTE(hbono): We can NEVER let WTL call ::DefWindowProc() when we update
  // the styles of IME windows because the 'lparam' variable is a local one
  // and all its updates disappear in returning from this function, i.e. WTL
  // does not call ::DefWindowProc() with our updated 'lparam' value but call
  // the function with its original value and over-writes our window styles.
  *handled = TRUE;
  lparam &= ~ISC_SHOWUICOMPOSITIONWINDOW;
  ::DefWindowProc(window_handle, message, wparam, lparam);
}

void ImeInput::DestroyImeWindow(HWND window_handle) {
  // Destroy the system caret if we have created for this IME input context.
  if (system_caret_) {
    ::DestroyCaret();
    system_caret_ = false;
  }
}

void ImeInput::MoveImeWindow(HWND window_handle, HIMC imm_context) {
  int x = caret_rect_.x();
  int y = caret_rect_.y();
  const int kCaretMargin = 1;
  // As written in a comment in ImeInput::CreateImeWindow(),
  // Chinese IMEs ignore function calls to ::ImmSetCandidateWindow()
  // when a user disables TSF (Text Service Framework) and CUAS (Cicero
  // Unaware Application Support).
  // On the other hand, when a user enables TSF and CUAS, Chinese IMEs
  // ignore the position of the current system caret and uses the
  // parameters given to ::ImmSetCandidateWindow() with its 'dwStyle'
  // parameter CFS_CANDIDATEPOS.
  // Therefore, we do not only call ::ImmSetCandidateWindow() but also
  // set the positions of the temporary system caret if it exists.
  CANDIDATEFORM candidate_position = {0, CFS_CANDIDATEPOS, {x, y},
                                      {0, 0, 0, 0}};
  ::ImmSetCandidateWindow(imm_context, &candidate_position);
  if (system_caret_) {
    switch (PRIMARYLANGID(input_language_id_)) {
      case LANG_JAPANESE:
        ::SetCaretPos(x, y + caret_rect_.height());
        break;
      default:
        ::SetCaretPos(x, y);
        break;
    }
  }
  if (PRIMARYLANGID(input_language_id_) == LANG_KOREAN) {
    // Chinese IMEs and Japanese IMEs require the upper-left corner of
    // the caret to move the position of their candidate windows.
    // On the other hand, Korean IMEs require the lower-left corner of the
    // caret to move their candidate windows.
    y += kCaretMargin;
  }
  // Japanese IMEs and Korean IMEs also use the rectangle given to
  // ::ImmSetCandidateWindow() with its 'dwStyle' parameter CFS_EXCLUDE
  // to move their candidate windows when a user disables TSF and CUAS.
  // Therefore, we also set this parameter here.
  CANDIDATEFORM exclude_rectangle = {0, CFS_EXCLUDE, {x, y},
      {x, y, x + caret_rect_.width(), y + caret_rect_.height()}};
  ::ImmSetCandidateWindow(imm_context, &exclude_rectangle);
}

void ImeInput::UpdateImeWindow(HWND window_handle) {
  // Just move the IME window attached to the given window.
  if (caret_rect_.x() >= 0 && caret_rect_.y() >= 0) {
    HIMC imm_context = ::ImmGetContext(window_handle);
    if (imm_context) {
      MoveImeWindow(window_handle, imm_context);
      ::ImmReleaseContext(window_handle, imm_context);
    }
  }
}

void ImeInput::CleanupComposition(HWND window_handle) {
  // Notify the IMM attached to the given window to complete the ongoing
  // composition, (this case happens when the given window is de-activated
  // while composing a text and re-activated), and reset the omposition status.
  if (is_composing_) {
    HIMC imm_context = ::ImmGetContext(window_handle);
    if (imm_context) {
      ::ImmNotifyIME(imm_context, NI_COMPOSITIONSTR, CPS_COMPLETE, 0);
      ::ImmReleaseContext(window_handle, imm_context);
    }
    ResetComposition(window_handle);
  }
}

void ImeInput::ResetComposition(HWND window_handle) {
  // Currently, just reset the composition status.
  is_composing_ = false;
}

void ImeInput::CompleteComposition(HWND window_handle, HIMC imm_context) {
  // We have to confirm there is an ongoing composition before completing it.
  // This is for preventing some IMEs from getting confused while completing an
  // ongoing composition even if they do not have any ongoing compositions.)
  if (is_composing_) {
    ::ImmNotifyIME(imm_context, NI_COMPOSITIONSTR, CPS_COMPLETE, 0);
    ResetComposition(window_handle);
  }
}

void ImeInput::GetCaret(HIMC imm_context, LPARAM lparam,
                        ImeComposition* composition) {
  // This operation is optional and language-dependent because the caret
  // style is depended on the language, e.g.:
  //   * Korean IMEs: the caret is a blinking block,
  //     (It contains only one hangul character);
  //   * Chinese IMEs: the caret is a blinking line,
  //     (i.e. they do not need to retrieve the target selection);
  //   * Japanese IMEs: the caret is a selection (or undelined) block,
  //     (which can contain one or more Japanese characters).
  int target_start = -1;
  int target_end = -1;
  switch (PRIMARYLANGID(input_language_id_)) {
  case LANG_KOREAN:
    if (lparam & CS_NOMOVECARET) {
      target_start = 0;
      target_end = 1;
    }
    break;
  case LANG_CHINESE:
    break;
  case LANG_JAPANESE:
    // For Japanese IMEs, the robustest way to retrieve the caret
    // is scanning the attribute of the latest composition string and
    // retrieving the begining and the end of the target clause, i.e.
    // a clause being converted.
    if (lparam & GCS_COMPATTR) {
      int attribute_size = ::ImmGetCompositionString(imm_context,
                                                     GCS_COMPATTR,
                                                     NULL, 0);
      if (attribute_size > 0) {
        scoped_array<char> attribute_data(new char[attribute_size]);
        if (attribute_data.get()) {
          ::ImmGetCompositionString(imm_context, GCS_COMPATTR,
                                    attribute_data.get(), attribute_size);
          for (target_start = 0; target_start < attribute_size;
               ++target_start) {
            if (IsTargetAttribute(attribute_data[target_start]))
              break;
          }
          for (target_end = target_start; target_end < attribute_size;
               ++target_end) {
            if (!IsTargetAttribute(attribute_data[target_end]))
              break;
          }
          if (target_start == attribute_size) {
            // This composition clause does not contain any target clauses,
            // i.e. this clauses is an input clause.
            // We treat whole this clause as a target clause.
            target_end = target_start;
            target_start = 0;
          }
        }
      }
    }
    break;
  }
  composition->target_start = target_start;
  composition->target_end = target_end;
}

bool ImeInput::GetString(HIMC imm_context, WPARAM lparam, int type,
                         ImeComposition* composition) {
  bool result = false;
  if (lparam & type) {
    int string_size = ::ImmGetCompositionString(imm_context, type, NULL, 0);
    if (string_size > 0) {
      int string_length = string_size / sizeof(wchar_t);
      wchar_t *string_data = WriteInto(&composition->ime_string,
                                       string_length + 1);
      if (string_data) {
        // Fill the given ImeComposition object.
        ::ImmGetCompositionString(imm_context, type,
                                  string_data, string_size);
        composition->string_type = type;
        result = true;
      }
    }
  }
  return result;
}

bool ImeInput::GetResult(HWND window_handle, LPARAM lparam,
                         ImeComposition* composition) {
  bool result = false;
  HIMC imm_context = ::ImmGetContext(window_handle);
  if (imm_context) {
    // Copy the result string to the ImeComposition object.
    result = GetString(imm_context, lparam, GCS_RESULTSTR, composition);
    // Reset all the other parameters because a result string does not
    // have composition attributes.
    composition->cursor_position = -1;
    composition->target_start = -1;
    composition->target_end = -1;
    ::ImmReleaseContext(window_handle, imm_context);
  }
  return result;
}

bool ImeInput::GetComposition(HWND window_handle, LPARAM lparam,
                              ImeComposition* composition) {
  bool result = false;
  HIMC imm_context = ::ImmGetContext(window_handle);
  if (imm_context) {
    // Copy the composition string to the ImeComposition object.
    result = GetString(imm_context, lparam, GCS_COMPSTR, composition);

    // Retrieve the cursor position in the IME composition.
    int cursor_position = ::ImmGetCompositionString(imm_context,
                                                    GCS_CURSORPOS, NULL, 0);
    composition->cursor_position = cursor_position;
    composition->target_start = -1;
    composition->target_end = -1;

    // Retrieve the target selection and Update the ImeComposition
    // object.
    GetCaret(imm_context, lparam, composition);

    // Mark that there is an ongoing composition.
    is_composing_ = true;

    ::ImmReleaseContext(window_handle, imm_context);
  }
  return result;
}

void ImeInput::DisableIME(HWND window_handle) {
  // A renderer process have moved its input focus to a password input
  // when there is an ongoing composition, e.g. a user has clicked a
  // mouse button and selected a password input while composing a text.
  // For this case, we have to complete the ongoing composition and
  // clean up the resources attached to this object BEFORE DISABLING THE IME.
  CleanupComposition(window_handle);
  ::ImmAssociateContextEx(window_handle, NULL, 0);
}

void ImeInput::EnableIME(HWND window_handle,
                         const gfx::Rect& caret_rect,
                         bool complete) {
  // Load the default IME context.
  // NOTE(hbono)
  //   IMM ignores this call if the IME context is loaded. Therefore, we do
  //   not have to check whether or not the IME context is loaded.
  ::ImmAssociateContextEx(window_handle, NULL, IACE_DEFAULT);
  // Complete the ongoing composition and move the IME windows.
  HIMC imm_context = ::ImmGetContext(window_handle);
  if (imm_context) {
    if (complete) {
      // A renderer process have moved its input focus to another edit
      // control when there is an ongoing composition, e.g. a user has
      // clicked a mouse button and selected another edit control while
      // composing a text.
      // For this case, we have to complete the ongoing composition and
      // hide the IME windows BEFORE MOVING THEM.
      CompleteComposition(window_handle, imm_context);
    }
    // Save the caret position, and Update the position of the IME window.
    // This update is used for moving an IME window when a renderer process
    // resize/moves the input caret.
    if (caret_rect.x() >= 0 && caret_rect.y() >= 0) {
      caret_rect_.SetRect(caret_rect.x(), caret_rect.y(), caret_rect.width(),
                          caret_rect.height());
      MoveImeWindow(window_handle, imm_context);
    }
    ::ImmReleaseContext(window_handle, imm_context);
  }
}