diff --git a/.gitignore b/.gitignore
index 7bbc71c..9eb16cb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -99,3 +99,6 @@ ENV/
 
 # mypy
 .mypy_cache/
+/temp.py
+*.json
+id
\ No newline at end of file
diff --git a/app.py b/app.py
index f4203a7..da0b921 100644
--- a/app.py
+++ b/app.py
@@ -1,19 +1,117 @@
-from flask import Flask, request
+from flask import Flask, request, jsonify
 import zlib
 import base64
 import json
+import os.path
 
 app = Flask(__name__)
 
+## global server action id. should init in first run
+id = 0
+ID_FILE_PATH = "id"
+DATA_FILE_PATH = "data.json"
+
+## deal with cli data
 @app.route("/v1/sync", methods=["GET", "POST"])
 def sync():
     payload = json.loads(request.data)
     raw_data = base64.b64decode(payload["actions"])
     json_data = json.loads(zlib.decompress(raw_data, 16 + zlib.MAX_WBITS))
 
-    print "Request: ", json_data
+    if json_data is None: data = []
+    # extract data to response to client
+    actions = fetchResponseById(payload["bookmark"])
+    # save actions with generated id
+    saveActionsAndGenerateId(payload["bookmark"], json_data)
+
+    # constuct response
+    response = {}
+    # response["bookmark"] = lastId() # ? should I use u"bookmark" here? what is the difference?
+    response[u"bookmark"] = lastId()
+    response[u"actions"] = actions
+
+    saveId()
+
+    return jsonify(response), 200
+
+## functions about id
+def initId():
+    global id
+    with open(ID_FILE_PATH) as infile:
+        id = json.load(infile)[u'id']
+
+def saveId():
+    with open(ID_FILE_PATH, 'w') as outfile:
+        json.dump({u'id':id}, outfile)
+
+def generateId():
+    global id
+    id =  id + 1
+    return id
+
+def lastId():
+    return id
+
+def saveActionsAndGenerateId(bookmark, actions):
+    if bookmark == lastId():
+        saveData(actions)
+    elif bookmark < lastId():
+        saveData(actions)
+    else:
+    # maybe delete all client data and re-sync?
+    # but now do nothing.
+        print "bookmark is greater than last id in server"
+
+def fetchResponseById(bookmark):
+    def fresh(x):
+        return x["id"] > bookmark
+
+    alldata = readData()
+    actions = filter(fresh, alldata)
+    return actions
+
+def sillyDataAppend(old, data):
+    for item in data:
+        if (not isDuplicate(item, old)):
+            item["id"] = generateId()
+            old.append(item)
+
+    # maybe should compare *type* value
+    return sorted(old, key=lambda o:o['id'])
+
+def isDuplicate(item, collections):
+    for action in collections:
+        if (item["timestamp"] == action["timestamp"] and item["data"] == action["data"] and item["type"] == action["type"]): return True
+    return False
+
+
+## functions about read/write file
+def saveData(data):
+    old = readData()
+    newdata = sillyDataAppend(old, data)
+    writeData(newdata)
+
+
+def writeData(data):
+    with open(DATA_FILE_PATH, 'w') as outfile:
+        json.dump(data, outfile)
+
+def readData():
+    with open(DATA_FILE_PATH) as infile:
+        data = json.load(infile)
+        return data
+    return []
 
-    return resp, 200
+## functions to initialize data files
+def initDataFiles():
+    if not os.path.isfile(ID_FILE_PATH):
+        id = 0
+        saveId()
+    if not os.path.isfile(DATA_FILE_PATH):
+        writeData([])
 
+## main function
 if __name__ == "__main__":
-    app.run(debug=False)
\ No newline at end of file
+    initDataFiles()
+    initId()
+    app.run(debug=False)