what is the developed source code snippets that shows core solution and detailed code should be in appendix section in this following code 
import dash
from dash import dcc, html, dash_table
from dash.dependencies import Input, Output, State
import sqlite3
import pandas as pd
import base64
import io;

# إعداد التطبيق مع ورقة الأنماط الخارجية
app = dash.Dash(__name__, external_stylesheets=['assets/styles.css'])

# إعداد قاعدة البيانات
conn = sqlite3.connect('RetailDB_db.sqlite')
cursor = conn.cursor()
cursor.execute('''
    CREATE TABLE IF NOT EXISTS RetailDB
    (id INTEGER PRIMARY KEY, filename TEXT, filetype TEXT, filedata BLOB, upload_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP)
''')
conn.commit()
conn.close()

# دمج التصميمات
app.layout = html.Div([
    # الرأس وشريط التنقل والشريط الجانبي والمحتوى الرئيسي
    html.Div(className='header', children=[
    html.Div(className='dashboard-name', children='Retail Sector Analysis'),
    html.Div(className='page-title', children=[
        dcc.Link('Control Board', href='/Control_board'),
        dcc.Link('Dashboard', href='/dashboard'),
    ]),
]),

    html.Div(className='navbar', children=[
        html.Div(id='navbar-title', children='Dashboard'),
    ]),
    html.Div(className="sidebar"),
    dcc.Location(id='url', refresh=False),
    html.Div(id='page-content', className='main-content'),

    # أقسام إدارة الملفات
    html.Div(className='section', children=[
        html.H2('File Upload'),
        dcc.Upload(
            id='upload-data',
            children=html.Div(['Drag and Drop or ', html.A('Select Files')]),
            style={
                'width': '60%',
                'height': '60px',
                'lineHeight': '60px',
                'borderWidth': '1px',
                'borderStyle': 'dashed',
                'borderRadius': '5px',
                'textAlign': 'center',
                'margin': '10px'
            },
            multiple=False
        ),
        html.Button('Upload File', id='upload-button'),
        html.Button('Cancel', id='cancel-upload-button'),
        html.Div(id='file-info', style={'margin-top': '10px'}),
        html.Div(id='output-data-upload', style={'color': 'red'}),
    ]),
    html.Div(className='section', children=[
        html.H2('File Management'),
        html.Button('View Files', id='view-files-button'),
        html.Button('Delete ', id='delete-files-button'),
        html.Button('Cancel', id='cancel-button'),
        dash_table.DataTable(
            id='files-table',
            columns=[
                {'name': 'ID', 'id': 'id'},
                {'name': 'Filename', 'id': 'filename'},
                {'name': 'Filetype', 'id': 'filetype'},
                {'name': 'Upload Date', 'id': 'upload_date'}
            ],
            row_selectable='multi',
            filter_action="native"
        ),
        html.Div(id='delete-message', style={'color': 'green'})
    ]),
    html.Div(className='section', children=[
    html.H2('Data Cleaning'),
    html.Button('Clean Data', id='clean-data-button'),
    dash_table.DataTable(id='cleaning-results-table', columns=[
        {'name': 'Filename', 'id': 'filename'},
        {'name': 'Missing Values', 'id': 'missing_values'},
        {'name': 'Outliers', 'id': 'outliers'},
        {'name': 'Duplicates', 'id': 'duplicates'},
        {'name': 'Transformations', 'id': 'transformations'},
        {'name': 'Cleaned Rows', 'id': 'cleaned_rows'}
    ])
])

])

# Callback للتنقل بين الصفحات
@app.callback(
    Output('navbar-title', 'children'),
    Output('page-content', 'children'),
    Input('url', 'pathname')
)
def display_page(pathname):
    if pathname == '/about_retail_sector':
        return 'About Retail Sector', html.Div()
    elif pathname == '/Control_board':
        return 'Control Board', html.Div()
    else:
        return 'Dashboard', html.Div()

# Callback لرفع الملفات
@app.callback(
    Output('output-data-upload', 'children'),
    Input('upload-button', 'n_clicks'),
    State('upload-data', 'contents'),
    State('upload-data', 'filename'),
    State('upload-data', 'last_modified')
)
def upload_file(n_clicks, content, filename, last_modified):
    if n_clicks is None or content is None:
        return ''

    # تحقق من نوع الملف
    ALLOWED_TYPES = ['xls', 'csv', 'xlsx']
    if not filename.endswith(tuple(ALLOWED_TYPES)):
        return f'File type not allowed. Allowed types: {", ".join(ALLOWED_TYPES)}'

    try:
        content_type, content_string = content.split(',')
        decoded = base64.b64decode(content_string)

        conn = sqlite3.connect('RetailDB_db.sqlite')
        cursor = conn.cursor()
        cursor.execute("INSERT INTO RetailDB (filename, filetype, filedata) VALUES (?, ?, ?)", (filename, content_type, decoded))
        conn.commit()
        conn.close()

        return f"File {filename} uploaded successfully!"
    except Exception as e:
        return f"An error occurred: {str(e)}"

# Callback لتحديث معلومات الملف بعد الرفع
@app.callback(
    Output('file-info', 'children'),
    [Input('upload-data', 'contents')],
    [State('upload-data', 'filename'), State('upload-data', 'last_modified')]
)
def update_file_info(contents, filename, last_modified):
    if contents is None:
        return 'No file selected.'
    else:
        content_type, content_string = contents.split(',')
        decoded = base64.b64decode(content_string)
        size_in_mb = len(decoded) / (1024 )  # حجم الملف بالميغابايت

        return html.Div([
            html.P(f"File Name: {filename}"),
            html.P(f"File Size: {size_in_mb:.2f} KB")
        ])

# دمج Callbacks لعرض وحذف الملفات
# الدمج بين Callbacks لعرض وحذف الملفات
@app.callback(
    [Output('files-table', 'data'),
     Output('delete-message', 'children')],
    [Input('view-files-button', 'n_clicks'),
     Input('delete-files-button', 'n_clicks'),
     Input('cancel-button', 'n_clicks')],
    [State('files-table', 'selected_rows'),
     State('files-table', 'data')],
    prevent_initial_call=True
)
def update_and_delete_files(view_clicks, delete_clicks, cancel_clicks, selected_rows, rows):
    ctx = dash.callback_context

    if not ctx.triggered:
        raise dash.exceptions.PreventUpdate

    button_id = ctx.triggered[0]['prop_id'].split('.')[0]

    if button_id == 'view-files-button':
        conn = sqlite3.connect('RetailDB_db.sqlite')
        df = pd.read_sql_query("SELECT id, filename, filetype, upload_date FROM RetailDB", conn)
        conn.close()
        return df.to_dict('records'), ''

    elif button_id == 'delete-files-button':
        try:
            if not selected_rows:
                return dash.no_update, 'No file selected for deletion.'

            selected_ids = [rows[i]['id'] for i in selected_rows]
            conn = sqlite3.connect('RetailDB_db.sqlite')
            cursor = conn.cursor()
            cursor.executemany("DELETE FROM RetailDB WHERE id=?", [(id,) for id in selected_ids])
            conn.commit()
            conn.close()

            updated_rows = [row for row in rows if row['id'] not in selected_ids]
            return updated_rows, 'Selected RetailDB have been deleted.'
        except Exception as e:
            return dash.no_update, f'Error in deleting files: {str(e)}'

    elif button_id == 'cancel-button':
        return dash.no_update, ''

    else:
        raise dash.exceptions.PreventUpdate
    
    
@app.callback(
   
    Output('cleaning-results-table', 'data'),
    Input('clean-data-button', 'n_clicks'),
    prevent_initial_call=True
)
def clean_data(n_clicks):
    if n_clicks is None:
        raise dash.exceptions.PreventUpdate

    conn = sqlite3.connect('RetailDB_db.sqlite')
    cursor = conn.cursor()
    
    cursor.execute("SELECT name FROM sqlite_master WHERE type='table';")
    table_names = [name[0] for name in cursor.fetchall()]

    cleaning_results = []

    for table_name in table_names:
        cursor.execute(f"SELECT * FROM {table_name}")
        files = cursor.fetchall()

        for file_row in files:
            if len(file_row) < 3:
                continue

            file_id, filename, filedata = file_row[:3]

            # تحويل البيانات إلى كائن ثنائي إذا كانت في شكل نص
            if isinstance(filedata, str):
                filedata = filedata.encode('utf-8')

            try:
                df = pd.read_csv(io.BytesIO(filedata), encoding='utf-8')
            except UnicodeDecodeError:
                try:
                    df = pd.read_csv(io.BytesIO(filedata), encoding='ISO-8859-1')
                except Exception as e:
                    continue

            # تنظيف البيانات
            df = clean_dataframe(df)

            cleaned_rows = df.shape[0]

            cleaning_results.append({
                'filename': filename,
                'missing_values': count_missing_values(df),
                'outliers': detect_outliers(df),
                'duplicates': count_duplicates(df),
                'transformations': apply_transformations(df),
                'cleaned_rows': cleaned_rows
            })

    conn.close()
    return cleaning_results

# تعريف الوظائف المساعدة لتنظيف البيانات
def clean_dataframe(df):
    # معالجة القيم المفقودة
    df.fillna(method='ffill', inplace=True)
    
    # إزالة السجلات المكررة
    df.drop_duplicates(inplace=True)

    return df

def count_missing_values(df):
    return df.isnull().sum().sum()

def detect_outliers(df):
    # يمكنك تعريف كيفية اكتشاف القيم الشاذة هنا
    return "Not implemented"

def count_duplicates(df):
    return df.duplicated().sum()

def apply_transformations(df):
    # يمكنك تطبيق التحويلات هنا
    return "Not implemented"
if __name__ == '__main__':
    app.run_server(debug=True)