app.py

import base64
import io
import os
import zipfile
from threading import Thread

import dash
import dash_bootstrap_components as dbc
from dash import dcc, html, Input, Output, State, callback, MATCH, ALL
from dash.exceptions import PreventUpdate
from PyPDF2 import PdfReader, PdfWriter

app = dash.Dash(__name__, external_stylesheets=[dbc.themes.BOOTSTRAP])

# Global variables
generated_file = None
progress = 0

# Layout
app.layout = dbc.Container([
    html.H1("PDF Splitter", className="my-4"),
    dcc.Upload(
        id='upload-pdf',
        children=html.Div(['Drag and Drop or ', html.A('Select PDF')]),
        style={
            'width': '100%',
            'height': '60px',
            'lineHeight': '60px',
            'borderWidth': '1px',
            'borderStyle': 'dashed',
            'borderRadius': '5px',
            'textAlign': 'center',
            'margin': '10px'
        },
        multiple=False
    ),
    html.Div(id='pdf-name'),
    dbc.Card([
        dbc.CardBody([
            html.Div(id='ranges-container', children=[
                dbc.Row([
                    dbc.Col(dbc.Input(id={'type': 'range-input', 'index': 0}, type='text', placeholder='Enter page range (e.g., 1-3)'), width=10),
                    dbc.Col(dbc.Button("Remove", id={'type': 'remove-range', 'index': 0}, color="danger", size="sm"), width=2),
                ], className="mb-2"),
            ]),
            dbc.Button("Add Range", id='add-range', color="secondary", className="mt-2"),
        ])
    ], className="my-3"),
    dbc.Button("Split PDF", id='split-button', color="primary", className="mt-3", disabled=True),
    dbc.Progress(id='progress-bar', className="my-3"),
    dbc.Button("Download ZIP", id='download-button', color="success", className="mt-3", disabled=True),
    dcc.Download(id="download-zip"),
], fluid=True)

@callback(
    Output('pdf-name', 'children'),
    Output('split-button', 'disabled'),
    Input('upload-pdf', 'contents'),
    State('upload-pdf', 'filename')
)
def update_output(contents, filename):
    if contents is not None:
        return f"Selected file: {filename}", False
    return "No file selected", True

@callback(
    Output('ranges-container', 'children'),
    Input('add-range', 'n_clicks'),
    Input({'type': 'remove-range', 'index': ALL}, 'n_clicks'),
    State('ranges-container', 'children'),
    prevent_initial_call=True
)
def manage_ranges(add_clicks, remove_clicks, existing_ranges):
    ctx = dash.callback_context
    triggered_id = ctx.triggered[0]['prop_id'].split('.')[0]

    if triggered_id == 'add-range':
        new_index = len(existing_ranges)
        new_range = dbc.Row([
            dbc.Col(dbc.Input(id={'type': 'range-input', 'index': new_index}, type='text', placeholder='Enter page range (e.g., 1-3)'), width=10),
            dbc.Col(dbc.Button("Remove", id={'type': 'remove-range', 'index': new_index}, color="danger", size="sm"), width=2),
        ], className="mb-2")
        existing_ranges.append(new_range)
    elif 'remove-range' in triggered_id:
        remove_index = json.loads(triggered_id)['index']
        existing_ranges = [range for range in existing_ranges if json.loads(range['props']['children'][1]['props']['children']['props']['id'])['index'] != remove_index]

    return existing_ranges

def process_pdf(contents, filename, ranges):
    global generated_file, progress
    progress = 0
    
    try:
        content_type, content_string = contents.split(',')
        decoded = base64.b64decode(content_string)
        pdf = PdfReader(io.BytesIO(decoded))
        
        writers = []
        for range_str in ranges:
            start, end = map(int, range_str.split('-'))
            writer = PdfWriter()
            for i in range(start - 1, min(end, len(pdf.pages))):
                writer.add_page(pdf.pages[i])
            writers.append(writer)
        
        zip_buffer = io.BytesIO()
        with zipfile.ZipFile(zip_buffer, 'w', zipfile.ZIP_DEFLATED) as zf:
            for i, writer in enumerate(writers):
                progress = (i + 1) / len(writers) * 100
                pdf_buffer = io.BytesIO()
                writer.write(pdf_buffer)
                pdf_buffer.seek(0)
                zf.writestr(f"split_{i+1}.pdf", pdf_buffer.getvalue())
        
        zip_buffer.seek(0)
        generated_file = zip_buffer.getvalue()
        progress = 100
    except Exception as e:
        print(f"Error processing PDF: {str(e)}")
        progress = -1

@callback(
    Output('progress-bar', 'value'),
    Output('download-button', 'disabled'),
    Input('split-button', 'n_clicks'),
    State('upload-pdf', 'contents'),
    State('upload-pdf', 'filename'),
    State({'type': 'range-input', 'index': ALL}, 'value'),
    prevent_initial_call=True
)
def split_pdf(n_clicks, contents, filename, ranges):
    if not contents or not ranges:
        raise PreventUpdate
    
    ranges = [r for r in ranges if r]  # Filter out empty ranges
    thread = Thread(target=process_pdf, args=(contents, filename, ranges))
    thread.start()
    
    return 0, True

@callback(
    Output('progress-bar', 'value', allow_duplicate=True),
    Output('download-button', 'disabled', allow_duplicate=True),
    Input('progress-bar', 'value'),
    prevent_initial_call=True
)
def update_progress(value):
    global progress
    if progress == 100:
        return 100, False
    elif progress == -1:
        return 0, True
    else:
        return progress, True

@callback(
    Output("download-zip", "data"),
    Input("download-button", "n_clicks"),
    prevent_initial_call=True
)
def download_zip(n_clicks):
    global generated_file
    if generated_file is not None:
        return dcc.send_bytes(generated_file, "split_pdfs.zip")
    raise PreventUpdate

if __name__ == '__main__':
    print("Starting the Dash application...")
    app.run(debug=True, host='0.0.0.0', port=7860)
    print("Dash application has finished running.")