diff --git a/src/actions/background.js b/src/actions/background.js
deleted file mode 100644
index 40b901b..0000000
--- a/src/actions/background.js
+++ /dev/null
@@ -1,11 +0,0 @@
-import actions from '../actions';
-
-export function requestCompletions(line) {
-  let command = line.split(' ', 1)[0];
-  let keywords = line.replace(command + ' ', '');
-  return {
-    type: actions.BACKGROUND_REQUEST_COMPLETIONS,
-    command,
-    keywords
-  };
-}
diff --git a/src/actions/command.js b/src/actions/command.js
index c983278..03f1e83 100644
--- a/src/actions/command.js
+++ b/src/actions/command.js
@@ -1,4 +1,5 @@
-import actions from '../actions';
+import * as tabs from '../background/tabs';
+import * as consoleActions from './console';
 
 const normalizeUrl = (string) => {
   try {
@@ -8,28 +9,76 @@ const normalizeUrl = (string) => {
   }
 }
 
-export function exec(line) {
-  let name = line.split(' ')[0];
-  let remaining = line.replace(name + ' ', '');
+const openCommand = (url) => {
+  return browser.tabs.query({ active: true, currentWindow: true }).then((tabs) => {
+    if (tabs.length > 0) {
+      return browser.tabs.update(tabs[0].id, { url: url });
+    }
+  });
+}
 
+const tabopenCommand = (url) => {
+  return browser.tabs.create({ url: url });
+}
+
+const bufferCommand = (keywords) => {
+  return browser.tabs.query({ active: true, currentWindow: true }).then((tabss) => {
+    if (tabss.length > 0) {
+      if (isNaN(keywords)) {
+        return tabs.selectByKeyword(tabss[0], keywords);
+      } else {
+        let index = parseInt(keywords, 10) - 1;
+        return tabs.selectAt(index);
+      }
+    }
+  });
+}
+
+const doCommand = (name, remaining) => {
   switch (name) {
   case 'open':
     // TODO use search engined and pass keywords to them
-    return {
-      type: actions.COMMAND_OPEN_URL,
-      url: normalizeUrl(remaining)
-    };
+    return openCommand(normalizeUrl(remaining));
   case 'tabopen':
-    return {
-      type: actions.COMMAND_TABOPEN_URL,
-      url: normalizeUrl(remaining)
-    };
+    return tabopenCommand(normalizeUrl(remaining));
   case 'b':
   case 'buffer':
-    return {
-      type: actions.COMMAND_BUFFER,
-      keywords: remaining
-    };
+    return bufferCommand(remaining);
   }
   throw new Error(name + ' command is not defined');
 }
+
+const getCompletions = (command, keywords) => {
+  switch (command) {
+  case 'buffer':
+    return tabs.getCompletions(keywords).then((tabs) => {
+      let items = tabs.map((tab) => {
+        return {
+          caption: tab.title,
+          content: tab.title,
+          url: tab.url,
+          icon: tab.favIconUrl
+        }
+      });
+      return [{
+        name: "Buffers",
+        items: items
+      }];
+    });
+  }
+  return Promise.resolve([]);
+};
+
+export function exec(line) {
+  let name = line.split(' ')[0];
+  let remaining = line.replace(name + ' ', '');
+  return doCommand(name, remaining).then(() => {
+    return consoleActions.hide();
+  });
+}
+
+export function complete(line) {
+  let command = line.split(' ', 1)[0];
+  let keywords = line.replace(command + ' ', '');
+  return getCompletions(command, keywords).then(consoleActions.setCompletions);
+}
diff --git a/src/actions/index.js b/src/actions/index.js
index 63d5f6f..977b3c2 100644
--- a/src/actions/index.js
+++ b/src/actions/index.js
@@ -5,36 +5,7 @@ export default {
   CONSOLE_SHOW_ERROR: 'vimvixen.console.show.error',
   CONSOLE_HIDE: 'vimvixen.console.hide',
 
-  // Background commands
-  BACKGROUND_REQUEST_COMPLETIONS: 'vimvixen.background.request.completions',
-  TABS_CLOSE: 'tabs.close',
-  TABS_REOPEN: 'tabs.reopen',
-  TABS_PREV: 'tabs.prev',
-  TABS_NEXT: 'tabs.next',
-  TABS_RELOAD: 'tabs.reload',
-  ZOOM_IN: 'zoom.in',
-  ZOOM_OUT: 'zoom.out',
-  ZOOM_NEUTRAL: 'zoom.neutral',
-
-  // content commands
-  CMD_OPEN: 'cmd.open',
-  CMD_TABS_OPEN: 'cmd.tabs.open',
-  CMD_BUFFER: 'cmd.buffer',
-  SCROLL_LINES: 'scroll.lines',
-  SCROLL_PAGES: 'scroll.pages',
-  SCROLL_TOP: 'scroll.top',
-  SCROLL_BOTTOM: 'scroll.bottom',
-  SCROLL_LEFT: 'scroll.left',
-  SCROLL_RIGHT: 'scroll.right',
-  FOLLOW_START: 'follow.start',
-  HISTORY_PREV: 'history.prev',
-  HISTORY_NEXT: 'history.next',
-
   // User input
   INPUT_KEY_PRESS: 'input.key,press',
   INPUT_CLEAR_KEYS: 'input.clear.keys',
-
-  COMMAND_OPEN_URL: 'command.open.url',
-  COMMAND_TABOPEN_URL: 'command.tabopen.url',
-  COMMAND_BUFFER: 'command.buffer',
 };
diff --git a/src/actions/operation.js b/src/actions/operation.js
new file mode 100644
index 0000000..e589b89
--- /dev/null
+++ b/src/actions/operation.js
@@ -0,0 +1,43 @@
+import operations from '../operations';
+import messages  from '../messages';
+import * as consoleActions from './console';
+import * as tabs from '../background/tabs';
+import * as zooms from '../background/zooms';
+
+export function exec(operation, tab) {
+  switch (operation.type) {
+  case operations.TABS_CLOSE:
+    return tabs.closeTab(tab.id);
+  case operations.TABS_REOPEN:
+    return tabs.reopenTab();
+  case operations.TABS_PREV:
+    return tabs.selectPrevTab(tab.index, operation.count);
+  case operations.TABS_NEXT:
+    return tabs.selectNextTab(tab.index, operation.count);
+  case operations.TABS_RELOAD:
+    return tabs.reload(tab, operation.cache);
+  case operations.ZOOM_IN:
+    return zooms.zoomIn();
+  case operations.ZOOM_OUT:
+    return zooms.zoomOut();
+  case operations.ZOOM_NEUTRAL:
+    return zooms.neutral();
+  case operations.COMMAND_OPEN:
+    return consoleActions.showCommand('');
+  case operations.COMMAND_TABS_OPEN:
+    if (operations.alter) {
+      // alter url
+      return consoleActions.showCommand('open ' + tab.url);
+    } else {
+      return consoleActions.showCommand('open ');
+    }
+  case operations.COMMAND_BUFFER:
+    return consoleActions.showCommand('buffer ');
+  default:
+    return browser.tabs.sendMessage(tab.id, {
+      type: messages.CONTENT_OPERATION,
+      operation
+    });
+  }
+}
+
diff --git a/src/background/index.js b/src/background/index.js
index e72cab0..ef1b881 100644
--- a/src/background/index.js
+++ b/src/background/index.js
@@ -1,45 +1,75 @@
 import * as keys from './keys';
 import * as inputActions from '../actions/input';
-import backgroundReducers from '../reducers/background';
-import commandReducer from '../reducers/command';
-import inputReducers from '../reducers/input';
+import * as operationActions from '../actions/operation';
+import * as commandActions from '../actions/command';
+import * as consoleActions from '../actions/console';
+import reducers from '../reducers';
+import messages from '../messages';
+import * as store from '../store'
 
-let inputState = inputReducers(undefined, {});
+let prevInput = [];
+const backgroundStore = store.createStore(reducers, (e, sender) => {
+  console.error('Vim-Vixen:', e);
+  if (sender) {
+    backgroundStore.dispatch(consoleActions.showError(e.message), sender);
+  }
+});
+backgroundStore.subscribe((sender) => {
+  let currentInput = backgroundStore.getState().input
+  if (JSON.stringify(prevInput) === JSON.stringify(currentInput)) {
+    return
+  }
+  prevInput = currentInput;
 
-const keyQueueChanged = (sender, prevState, state) => {
-  if (state.keys.length === 0) {
-    return Promise.resolve();
+  if (currentInput.keys.length === 0) {
+    return;
+  }
+  if (sender) {
+    return keyQueueChanged(backgroundStore.getState(), sender);
   }
+});
+backgroundStore.subscribe((sender) => {
+  if (sender) {
+    return browser.tabs.sendMessage(sender.tab.id, {
+      type: messages.STATE_UPDATE,
+      state: backgroundStore.getState()
+    });
+  }
+});
 
-  let prefix = keys.asKeymapChars(state.keys);
+const keyQueueChanged = (state, sender) => {
+  let prefix = keys.asKeymapChars(state.input.keys);
   let matched = Object.keys(keys.defaultKeymap).filter((keys) => {
     return keys.startsWith(prefix);
   });
   if (matched.length == 0) {
-    return handleMessage(inputActions.clearKeys(), sender);
+    backgroundStore.dispatch(inputActions.clearKeys(), sender);
+    return Promise.resolve();
   } else if (matched.length > 1 || matched.length === 1 && prefix !== matched[0]) {
     return Promise.resolve();
   }
   let action = keys.defaultKeymap[matched];
-  return handleMessage(inputActions.clearKeys(), sender).then(() => {
-    return backgroundReducers(undefined, action, sender).then(() => {
-      return browser.tabs.sendMessage(sender.tab.id, action);
-    });
-  });
+  backgroundStore.dispatch(operationActions.exec(action, sender.tab), sender);
+  backgroundStore.dispatch(inputActions.clearKeys(), sender);
 };
 
-const handleMessage = (action, sender) => {
-  let nextInputState = inputReducers(inputState, action);
-  if (JSON.stringify(nextInputState) !== JSON.stringify(inputState)) {
-    let prevState = inputState;
-    inputState = nextInputState;
-    return keyQueueChanged(sender, prevState, inputState);
-  }
-  return backgroundReducers(undefined, action, sender).then(() => {
-    return commandReducer(undefined, action, sender).then(() => {
-      return browser.tabs.sendMessage(sender.tab.id, action);
-    });
-  });
-};
+const handleMessage = (message, sender) => {
+  switch (message.type) {
+  case messages.KEYDOWN:
+    return backgroundStore.dispatch(inputActions.keyPress(message.code, message.ctrl), sender);
+  case messages.CONSOLE_BLURRED:
+    return backgroundStore.dispatch(consoleActions.hide(), sender);
+  case messages.CONSOLE_ENTERED:
+    return backgroundStore.dispatch(commandActions.exec(message.text), sender);
+  case messages.CONSOLE_CHANGEED:
+    return backgroundStore.dispatch(commandActions.complete(message.text), sender);
+  }
+}
 
-browser.runtime.onMessage.addListener(handleMessage);
+browser.runtime.onMessage.addListener((message, sender) => {
+  try {
+    handleMessage(message, sender);
+  } catch (e) {
+    backgroundStore.dispatch(consoleActions.showError(e.message), sender);
+  }
+});
diff --git a/src/background/keys.js b/src/background/keys.js
index 0ce53fa..8d75aba 100644
--- a/src/background/keys.js
+++ b/src/background/keys.js
@@ -1,35 +1,35 @@
-import actions from '../actions';
+import operations from '../operations';
 
 const defaultKeymap = {
-  ':': { type: actions.CMD_OPEN },
-  'o': { type: actions.CMD_TABS_OPEN, alter: false },
-  'O': { type: actions.CMD_TABS_OPEN, alter: true },
-  'b': { type: actions.CMD_BUFFER },
-  'k': { type: actions.SCROLL_LINES, count: -1 },
-  'j': { type: actions.SCROLL_LINES, count: 1 },
-  '<C-E>': { type: actions.SCROLL_LINES, count: -1 },
-  '<C-Y>': { type: actions.SCROLL_LINES, count: 1 },
-  '<C-U>': { type: actions.SCROLL_PAGES, count: -0.5 },
-  '<C-D>': { type: actions.SCROLL_PAGES, count: 0.5 },
-  '<C-B>': { type: actions.SCROLL_PAGES, count: -1 },
-  '<C-F>': { type: actions.SCROLL_PAGES, count: 1 },
-  'gg': { type: actions.SCROLL_TOP },
-  'G': { type: actions.SCROLL_BOTTOM },
-  '0': { type: actions.SCROLL_LEFT },
-  '$': { type: actions.SCROLL_RIGHT },
-  'd': { type: actions.TABS_CLOSE },
-  'u': { type: actions.TABS_REOPEN },
-  'h': { type: actions.TABS_PREV, count: 1 },
-  'l': { type: actions.TABS_NEXT, count: 1 },
-  'r': { type: actions.TABS_RELOAD, cache: false },
-  'R': { type: actions.TABS_RELOAD, cache: true },
-  'zi': { type: actions.ZOOM_IN },
-  'zo': { type: actions.ZOOM_OUT },
-  'zz': { type: actions.ZOOM_NEUTRAL },
-  'f': { type: actions.FOLLOW_START, newTab: false },
-  'F': { type: actions.FOLLOW_START, newTab: true },
-  'H': { type: actions.HISTORY_PREV },
-  'L': { type: actions.HISTORY_NEXT },
+  ':': { type: operations.COMMAND_OPEN },
+  'o': { type: operations.COMMAND_TABS_OPEN, alter: false },
+  'O': { type: operations.COMMAND_TABS_OPEN, alter: true },
+  'b': { type: operations.COMMAND_BUFFER },
+  'k': { type: operations.SCROLL_LINES, count: -1 },
+  'j': { type: operations.SCROLL_LINES, count: 1 },
+  '<C-E>': { type: operations.SCROLL_LINES, count: -1 },
+  '<C-Y>': { type: operations.SCROLL_LINES, count: 1 },
+  '<C-U>': { type: operations.SCROLL_PAGES, count: -0.5 },
+  '<C-D>': { type: operations.SCROLL_PAGES, count: 0.5 },
+  '<C-B>': { type: operations.SCROLL_PAGES, count: -1 },
+  '<C-F>': { type: operations.SCROLL_PAGES, count: 1 },
+  'gg': { type: operations.SCROLL_TOP },
+  'G': { type: operations.SCROLL_BOTTOM },
+  '0': { type: operations.SCROLL_LEFT },
+  '$': { type: operations.SCROLL_RIGHT },
+  'd': { type: operations.TABS_CLOSE },
+  'u': { type: operations.TABS_REOPEN },
+  'h': { type: operations.TABS_PREV, count: 1 },
+  'l': { type: operations.TABS_NEXT, count: 1 },
+  'r': { type: operations.TABS_RELOAD, cache: false },
+  'R': { type: operations.TABS_RELOAD, cache: true },
+  'zi': { type: operations.ZOOM_IN },
+  'zo': { type: operations.ZOOM_OUT },
+  'zz': { type: operations.ZOOM_NEUTRAL },
+  'f': { type: operations.FOLLOW_START, newTab: false },
+  'F': { type: operations.FOLLOW_START, newTab: true },
+  'H': { type: operations.HISTORY_PREV },
+  'L': { type: operations.HISTORY_NEXT },
 }
 
 const asKeymapChars = (keys) => {
diff --git a/src/console/console.js b/src/console/console.js
index 25ab36d..d1547b8 100644
--- a/src/console/console.js
+++ b/src/console/console.js
@@ -1,18 +1,17 @@
 import './console.scss';
-import * as backgroundActions from '../actions/background';
-import * as consoleActions from '../actions/console';
-import * as commandActions from '../actions/command';
 import Completion from './completion';
-import consoleReducer from '../reducers/console';
+import messages from '../messages';
 
 // TODO consider object-oriented
 var prevValue = "";
 var completion = null;
 var completionOrigin = "";
-let state = consoleReducer(undefined, {});
+var prevState = {};
 
 const handleBlur = () => {
-  return browser.runtime.sendMessage(consoleActions.hide());
+  return browser.runtime.sendMessage({
+    type: messages.CONSOLE_BLURRED,
+  });
 };
 
 const completeNext = () => {
@@ -52,7 +51,10 @@ const handleKeydown = (e) => {
   case KeyboardEvent.DOM_VK_ESCAPE:
     return input.blur();
   case KeyboardEvent.DOM_VK_RETURN:
-    return browser.runtime.sendMessage(commandActions.exec(e.target.value));
+    return browser.runtime.sendMessage({
+      type: messages.CONSOLE_ENTERED,
+      text: e.target.value
+    });
   case KeyboardEvent.DOM_VK_TAB:
     if (e.shiftKey) {
       completePrev();
@@ -73,9 +75,10 @@ const handleKeyup = (e) => {
     return;
   }
   prevValue = e.target.value;
-  return browser.runtime.sendMessage(
-    backgroundActions.requestCompletions(e.target.value)
-  );
+  return browser.runtime.sendMessage({
+    type: messages.CONSOLE_CHANGEED,
+    text: e.target.value
+  });
 };
 
 window.addEventListener('load', () => {
@@ -147,7 +150,7 @@ const updateCompletions = (completions) => {
   completionOrigin = input.value.split(' ')[0];
 }
 
-const update = (prevState, state) => {
+const update = (state) => {
   let error = window.document.querySelector('#vimvixen-console-error');
   let command = window.document.querySelector('#vimvixen-console-command');
   let input = window.document.querySelector('#vimvixen-console-command-input');
@@ -156,25 +159,26 @@ const update = (prevState, state) => {
   error.textContent = state.errorText;
 
   command.style.display = state.commandShown ? 'block' : 'none';
-  if (!prevState.commandShown && state.commandShown) {
-    // setup input on firstly shown
+  if (state.commandShown && !prevState.commandShown) {
     input.value = state.commandText;
     input.focus();
   }
-
   if (JSON.stringify(state.completions) !== JSON.stringify(prevState.completions)) {
     updateCompletions(state.completions);
   }
+
+  prevState = state;
 }
 
 browser.runtime.onMessage.addListener((action) => {
-  let nextState = consoleReducer(state, action);
-  if (JSON.stringify(nextState) !== JSON.stringify(state)) {
-    update(state, nextState);
-    state = nextState;
+  if (action.type === messages.STATE_UPDATE) {
+    return update(action.state.console);
   }
 });
 
 window.addEventListener('load', () => {
-  update({}, state);
+  let error = window.document.querySelector('#vimvixen-console-error');
+  let command = window.document.querySelector('#vimvixen-console-command');
+  error.style.display = 'none';
+  command.style.display = 'none';
 });
diff --git a/src/console/frames.js b/src/console/frames.js
index 0b6f3e2..ec1e38c 100644
--- a/src/console/frames.js
+++ b/src/console/frames.js
@@ -1,5 +1,4 @@
 import './console-frame.scss';
-import * as consoleActions from '../actions/console';
 
 const initialize = (doc) => {
   let iframe = doc.createElement('iframe');
@@ -11,17 +10,9 @@ const initialize = (doc) => {
   return iframe;
 }
 
-const showCommand = (text) => {
-  return browser.runtime.sendMessage(consoleActions.showCommand(text));
-};
-
-const showError = (text) => {
-  return browser.runtime.sendMessage(consoleActions.showError(text));
-}
-
 const blur = (doc) => {
   let iframe = doc.getElementById('vimvixen-console-frame');
   iframe.blur();
 }
 
-export { initialize, showCommand, showError, blur };
+export { initialize, blur };
diff --git a/src/content/index.js b/src/content/index.js
index 12d079f..5d3735c 100644
--- a/src/content/index.js
+++ b/src/content/index.js
@@ -1,40 +1,61 @@
 import '../console/console-frame.scss';
-import * as inputActions from '../actions/input';
 import * as consoleFrames from '../console/frames';
-import actions from '../actions';
-import contentReducer from '../reducers/content';
+import * as scrolls from '../content/scrolls';
+import * as histories from '../content/histories';
+import Follow from '../content/follow';
+import operations from '../operations';
+import messages  from '../messages';
 
 consoleFrames.initialize(window.document);
 
-browser.runtime.onMessage.addListener((action) => {
-  contentReducer(undefined, action);
-  return Promise.resolve();
-});
-
 window.addEventListener("keypress", (e) => {
   if (e.target instanceof HTMLInputElement) {
     return;
   }
-  browser.runtime.sendMessage(inputActions.keyPress(e.which, e.ctrlKey))
-    .catch((err) => {
-      console.error("Vim Vixen:", err);
-      return consoleFrames.showError(err.message);
-    });
+  browser.runtime.sendMessage({
+    type: messages.KEYDOWN,
+    code: e.which,
+    ctrl: e.ctrl
+  });
 });
 
+const execOperation = (operation) => {
+  switch (operation.type) {
+  case operations.SCROLL_LINES:
+    return scrolls.scrollLines(window, operation.count);
+  case operations.SCROLL_PAGES:
+    return scrolls.scrollPages(window, operation.count);
+  case operations.SCROLL_TOP:
+    return scrolls.scrollTop(window);
+  case operations.SCROLL_BOTTOM:
+    return scrolls.scrollBottom(window);
+  case operations.SCROLL_LEFT:
+    return scrolls.scrollLeft(window);
+  case operations.SCROLL_RIGHT:
+    return scrolls.scrollRight(window);
+  case operations.FOLLOW_START:
+    return new Follow(window.document, operation.newTab);
+  case operations.HISTORY_PREV:
+    return histories.prev(window);
+  case operations.HISTORY_NEXT:
+    return histories.next(window);
+  }
+}
+
+const update = (state) => {
+  if (!state.console.commandShown) {
+    window.focus();
+    consoleFrames.blur(window.document);
+  }
+}
+
 browser.runtime.onMessage.addListener((action) => {
   switch (action.type) {
-  case actions.CONSOLE_HIDE:
-    window.focus();
-    return consoleFrames.blur(window.document);
-  case 'vimvixen.command.enter':
-    return browser.runtime.sendMessage({
-      type: 'event.cmd.enter',
-      text: action.value
-    }).catch((err) => {
-      console.error("Vim Vixen:", err);
-      return consoleFrames.showError(err.message);
-    });
+  case messages.STATE_UPDATE:
+    return update(action.state);
+  case messages.CONTENT_OPERATION:
+    execOperation(action.operation);
+    return Promise.resolve();
   default:
     return Promise.resolve();
   }
diff --git a/src/messages/index.js b/src/messages/index.js
new file mode 100644
index 0000000..3bdecca
--- /dev/null
+++ b/src/messages/index.js
@@ -0,0 +1,10 @@
+export default {
+  STATE_UPDATE: 'state.update',
+  CONTENT_OPERATION: 'content.operation',
+
+  CONSOLE_BLURRED: 'console.blured',
+  CONSOLE_ENTERED: 'console.entered',
+  CONSOLE_CHANGEED: 'console.changed',
+
+  KEYDOWN: 'keydown'
+};
diff --git a/src/operations/index.js b/src/operations/index.js
new file mode 100644
index 0000000..05c7d78
--- /dev/null
+++ b/src/operations/index.js
@@ -0,0 +1,26 @@
+export default {
+  // command
+  COMMAND_OPEN: 'cmd.open',
+  COMMAND_TABS_OPEN: 'cmd.tabs.open',
+  COMMAND_BUFFER: 'cmd.buffer',
+
+  SCROLL_LINES: 'scroll.lines',
+  SCROLL_PAGES: 'scroll.pages',
+  SCROLL_TOP: 'scroll.top',
+  SCROLL_BOTTOM: 'scroll.bottom',
+  SCROLL_LEFT: 'scroll.left',
+  SCROLL_RIGHT: 'scroll.right',
+  FOLLOW_START: 'follow.start',
+  HISTORY_PREV: 'history.prev',
+  HISTORY_NEXT: 'history.next',
+
+  // background
+  TABS_CLOSE: 'tabs.close',
+  TABS_REOPEN: 'tabs.reopen',
+  TABS_PREV: 'tabs.prev',
+  TABS_NEXT: 'tabs.next',
+  TABS_RELOAD: 'tabs.reload',
+  ZOOM_IN: 'zoom.in',
+  ZOOM_OUT: 'zoom.out',
+  ZOOM_NEUTRAL: 'zoom.neutral',
+}
diff --git a/src/reducers/background.js b/src/reducers/background.js
deleted file mode 100644
index d7d7860..0000000
--- a/src/reducers/background.js
+++ /dev/null
@@ -1,53 +0,0 @@
-import * as tabs from '../background/tabs';
-import * as zooms from '../background/zooms';
-import * as consoleActions from '../actions/console';
-import actions from '../actions';
-
-const doCompletion = (command, keywords, sender) => {
-  if (command === 'buffer') {
-    return tabs.getCompletions(keywords).then((tabs) => {
-      let items = tabs.map((tab) => {
-        return {
-          caption: tab.title,
-          content: tab.title,
-          url: tab.url,
-          icon: tab.favIconUrl
-        }
-      });
-      let completions = {
-        name: "Buffers",
-        items: items
-      };
-      return browser.tabs.sendMessage(
-        sender,
-        consoleActions.setCompletions([completions]));
-    });
-  }
-  return Promise.resolve();
-};
-
-export default function reducer(state, action = {}, sender) {
-  // TODO hide sender object
-  switch (action.type) {
-  case actions.BACKGROUND_REQUEST_COMPLETIONS:
-    return doCompletion(action.command, action.keywords, sender.tab.id);
-  case actions.TABS_CLOSE:
-    return tabs.closeTab(sender.tab.id);
-  case actions.TABS_REOPEN:
-    return tabs.reopenTab();
-  case actions.TABS_PREV:
-    return tabs.selectPrevTab(sender.tab.index, action.count);
-  case actions.TABS_NEXT:
-    return tabs.selectNextTab(sender.tab.index, action.count);
-  case actions.TABS_RELOAD:
-    return tabs.reload(sender.tab, action.cache);
-  case actions.ZOOM_IN:
-    return zooms.zoomIn();
-  case actions.ZOOM_OUT:
-    return zooms.zoomOut();
-  case actions.ZOOM_NEUTRAL:
-    return zooms.neutral();
-  default:
-    return Promise.resolve();
-  }
-}
diff --git a/src/reducers/command.js b/src/reducers/command.js
deleted file mode 100644
index 7e03593..0000000
--- a/src/reducers/command.js
+++ /dev/null
@@ -1,24 +0,0 @@
-import * as tabs from '../background/tabs';
-import actions from '../actions';
-
-const cmdBuffer = (sender, arg) => {
-  if (isNaN(arg)) {
-    return tabs.selectByKeyword(sender.tab, arg);
-  } else {
-    let index = parseInt(arg, 10) - 1;
-    return tabs.selectAt(index);
-  }
-}
-
-export default function reducer(state, action, sender) {
-  switch (action.type) {
-  case actions.COMMAND_OPEN_URL:
-    return browser.tabs.update(sender.tab.id, { url: action.url });
-  case actions.COMMAND_TABOPEN_URL:
-    return browser.tabs.create({ url: action.url });
-  case actions.COMMAND_BUFFER:
-    return cmdBuffer(sender, action.keywords);
-  default:
-    return Promise.resolve();
-  }
-}
diff --git a/src/reducers/console.js b/src/reducers/console.js
index 3303802..27ccdc9 100644
--- a/src/reducers/console.js
+++ b/src/reducers/console.js
@@ -28,10 +28,13 @@ export default function reducer(state = defaultState, action = {}) {
       commandShown: false,
     });
   case actions.CONSOLE_HIDE:
+    if (state.errorShown) {
+      // keep error message if shown
+      return state;
+    }
     return Object.assign({}, state, {
       errorShown: false,
       commandShown: false
-      
     });
   default:
     return state;
diff --git a/src/reducers/content.js b/src/reducers/content.js
deleted file mode 100644
index bcf1160..0000000
--- a/src/reducers/content.js
+++ /dev/null
@@ -1,48 +0,0 @@
-import * as consoleFrames from '../console/frames';
-import * as histories from '../content/histories';
-import * as scrolls from '../content/scrolls';
-import Follow from '../content/follow';
-import actions from '../actions';
-
-export default function reducer(state, action = {}) {
-  switch (action.type) {
-  case actions.CMD_OPEN:
-    return consoleFrames.showCommand('');
-  case actions.CMD_TABS_OPEN:
-    if (action.alter) {
-      // alter url
-      return consoleFrames.showCommand('open ' + window.location.href);
-    } else {
-      return consoleFrames.showCommand('open ');
-    }
-  case actions.CMD_BUFFER:
-    return consoleFrames.showCommand('buffer ');
-  case actions.SCROLL_LINES:
-    scrolls.scrollLines(window, action.count);
-    break;
-  case actions.SCROLL_PAGES:
-    scrolls.scrollPages(window, action.count);
-    break;
-  case actions.SCROLL_TOP:
-    scrolls.scrollTop(window);
-    break;
-  case actions.SCROLL_BOTTOM:
-    scrolls.scrollBottom(window);
-    break;
-  case actions.SCROLL_LEFT:
-    scrolls.scrollLeft(window);
-    break;
-  case actions.SCROLL_RIGHT:
-    scrolls.scrollRight(window);
-    break;
-  case actions.FOLLOW_START:
-    new Follow(window.document, action.newTab);
-    break;
-  case actions.HISTORY_PREV:
-    histories.prev(window);
-    break;
-  case actions.HISTORY_NEXT:
-    histories.next(window);
-    break;
-  }
-}
diff --git a/src/reducers/index.js b/src/reducers/index.js
new file mode 100644
index 0000000..83a9a56
--- /dev/null
+++ b/src/reducers/index.js
@@ -0,0 +1,14 @@
+import inputReducer from '../reducers/input';
+import consoleReducer from '../reducers/console';
+
+const defaultState = {
+  input: inputReducer(undefined, {}),
+  console: consoleReducer(undefined, {})
+};
+
+export default function reducer(state = defaultState, action = {}) {
+  return Object.assign({}, state, {
+    input: inputReducer(state.input, action),
+    console: consoleReducer(state.console, action)
+  });
+}
diff --git a/src/store/index.js b/src/store/index.js
new file mode 100644
index 0000000..2d08296
--- /dev/null
+++ b/src/store/index.js
@@ -0,0 +1,51 @@
+class Store {
+  constructor(reducer, catcher) {
+    this.reducer = reducer;
+    this.catcher = catcher;
+    this.subscribers = [];
+    try {
+      this.state = this.reducer(undefined, {});
+    } catch (e) {
+      catcher(e);
+    }
+  }
+
+  dispatch(action, sender) {
+    if (action instanceof Promise) {
+      action.then((a) => {
+        this.transitNext(a, sender);
+      }).catch((e) => {
+        this.catcher(e, sender);
+      });
+    } else {
+      try {
+        this.transitNext(action, sender);
+      } catch (e) {
+        this.catcher(e, sender);
+      }
+    }
+    return action
+  }
+
+  getState() {
+    return this.state;
+  }
+
+  subscribe(callback) {
+    this.subscribers.push(callback);
+  }
+
+  transitNext(action, sender) {
+    let newState = this.reducer(this.state, action);
+    if (JSON.stringify(this.state) !== JSON.stringify(newState)) {
+      this.state = newState;
+      this.subscribers.forEach(f => f(sender));
+    }
+  }
+}
+
+const empty = () => {};
+
+export function createStore(reducer, catcher = empty) {
+  return new Store(reducer, catcher);
+}
diff --git a/test/actions/background.test.js b/test/actions/background.test.js
deleted file mode 100644
index a3203ee..0000000
--- a/test/actions/background.test.js
+++ /dev/null
@@ -1,14 +0,0 @@
-import { expect } from "chai";
-import actions from '../../src/actions';
-import * as backgroundActions from '../../src/actions/background';
-
-describe("background actions", () => {
-  describe("requestCompletions", () => {
-    it('create BACKGROUND_REQUEST_COMPLETIONS action', () => {
-      let action = backgroundActions.requestCompletions('buffer hoge fuga');
-      expect(action.type).to.equal(actions.BACKGROUND_REQUEST_COMPLETIONS);
-      expect(action.command).to.equal('buffer');
-      expect(action.keywords).to.equal('hoge fuga');
-    });
-  });
-});
diff --git a/test/actions/command.test.js b/test/actions/command.test.js
deleted file mode 100644
index 01a67f2..0000000
--- a/test/actions/command.test.js
+++ /dev/null
@@ -1,51 +0,0 @@
-import { expect } from "chai";
-import actions from '../../src/actions';
-import * as commandActions from '../../src/actions/command';
-
-describe("command actions", () => {
-  describe("exec", () => {
-    context("open command", () => {
-      it('create COMMAND_OPEN_URL acion with a full url', () => {
-        let action = commandActions.exec("open https://github.com/")
-        expect(action.type).to.equal(actions.COMMAND_OPEN_URL);
-        expect(action.url).to.equal('https://github.com/');
-      });
-
-      it('create COMMAND_OPEN_URL acion with a domain name', () => {
-        let action = commandActions.exec("open github.com")
-        expect(action.type).to.equal(actions.COMMAND_OPEN_URL);
-        expect(action.url).to.equal('http://github.com');
-      });
-    });
-
-    context("tabopen command", () => {
-      it('create COMMAND_TABOPEN_URL acion with a full url', () => {
-        let action = commandActions.exec("tabopen https://github.com/")
-        expect(action.type).to.equal(actions.COMMAND_TABOPEN_URL);
-        expect(action.url).to.equal('https://github.com/');
-      });
-
-      it('create COMMAND_TABOPEN_URL acion with a domain name', () => {
-        let action = commandActions.exec("tabopen github.com")
-        expect(action.type).to.equal(actions.COMMAND_TABOPEN_URL);
-        expect(action.url).to.equal('http://github.com');
-      });
-    });
-
-    context("buffer command", () => {
-      it('create COMMAND_BUFFER acion with a keywords', () => {
-        let action = commandActions.exec("buffer foo bar")
-        expect(action.type).to.equal(actions.COMMAND_BUFFER);
-        expect(action.keywords).to.equal('foo bar');
-      });
-    });
-
-    context("b command", () => {
-      it('create COMMAND_BUFFER acion with a keywords', () => {
-        let action = commandActions.exec("b foo bar")
-        expect(action.type).to.equal(actions.COMMAND_BUFFER);
-        expect(action.keywords).to.equal('foo bar');
-      });
-    });
-  });
-});
diff --git a/test/store/index.test.js b/test/store/index.test.js
new file mode 100644
index 0000000..e19d50e
--- /dev/null
+++ b/test/store/index.test.js
@@ -0,0 +1,111 @@
+import { expect } from "chai";
+import { createStore } from '../../src/store';
+
+describe("Store class", () => {
+  const reducer = (state, action) => {
+    if (state == undefined) {
+      return 0;
+    }
+    return state + action;
+  };
+
+  describe("#dispatch", () => {
+    it('transit status by immediate action', () => {
+      let store = createStore(reducer);
+      store.dispatch(10);
+      expect(store.getState()).to.equal(10);
+
+      store.dispatch(-20);
+      expect(store.getState()).to.equal(-10);
+    });
+
+    it('returns next state by immediate action', () => {
+      let store = createStore(reducer);
+      let dispatchedAction = store.dispatch(11);
+      expect(dispatchedAction).to.equal(11);
+    });
+
+    it('transit status by Promise action', () => {
+      let store = createStore(reducer);
+      let p1 = Promise.resolve(10);
+
+      return store.dispatch(p1).then(() => {
+        expect(store.getState()).to.equal(10);
+      }).then(() => {
+        store.dispatch(Promise.resolve(-20));
+      }).then(() => {
+        expect(store.getState()).to.equal(-10);
+      });
+    });
+
+    it('returns next state by promise action', () => {
+      let store = createStore(reducer);
+      let dispatchedAction = store.dispatch(Promise.resolve(11));
+      return dispatchedAction.then((value) => {
+        expect(value).to.equal(11);
+      });
+    });
+  });
+
+  describe("#subscribe", () => {
+    it('invoke callback', (done) => {
+      let store = createStore(reducer);
+      store.subscribe(() => {
+        expect(store.getState()).to.equal(15);
+        done();
+      });
+      store.dispatch(15);
+    });
+
+    it('propagate sender object', (done) => {
+      let store = createStore(reducer);
+      store.subscribe((sender) => {
+        expect(sender).to.equal('sender');
+        done();
+      });
+      store.dispatch(15, 'sender');
+    });
+  })
+
+  describe("catcher", () => {
+    it('catch an error in reducer on initializing by immediate action', (done) => {
+      let store = createStore(() => {
+        throw new Error();
+      }, (e) => {
+        expect(e).to.be.an('error');
+        done();
+      });
+    });
+
+    it('catch an error in reducer on initializing by immediate action', (done) => {
+      let store = createStore((state, action) => {
+        if (state === undefined) return 0;
+        throw new Error();
+      }, (e) => {
+        expect(e).to.be.an('error');
+        done();
+      });
+      store.dispatch(20);
+    });
+
+    it('catch an error in reducer on initializing by promise action', (done) => {
+      let store = createStore((state, action) => {
+        if (state === undefined) return 0;
+        throw new Error();
+      }, (e) => {
+        expect(e).to.be.an('error');
+        done();
+      });
+      store.dispatch(Promise.resolve(20));
+    });
+
+    it('catch an error in promise action', (done) => {
+      let store = createStore((state, action) => 0, (e) => {
+        expect(e).to.be.an('error');
+        done();
+      });
+      store.dispatch(new Promise(() => { throw new Error() }));
+    });
+  })
+});
+