donations: Imported Rene's donation plugin

This comes from a stale PR on the c-lightning issue tracker and after talking
with Rene, I decided to give it an official place to live.

donations/LICENSE

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+Note: the modules in the ccan/ directory have their own licenses, but
+the rest of the code is covered by the following (BSD-MIT) license:
+
+	Copyright Rene Pickhardt 2018.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

donations/README.md

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+# Invoice Service (for Donations) plugin
+
+This plugin enables c-lightning nodes to start one or several small webserver
+via the command line on specified port. The webserver is based on flask and
+exposes the invoice API call.
+
+Therefor people can query for an invoice which they can use to pay.
+
+Run the plugin with:
+
+```
+lightningd --plugin=/path/to/lightning/contrib/plugins/donations/donations.py
+```
+
+Once the plugin is active you can run `lightning-cli help donationserver`
+to learn about the command line API:
+
+Controls a donationserver with `start`/`stop`/`restart`/`list` on `port`
+
+A Simple HTTP Server is created that can serve a donation webpage and allow to issue invoices.
+The plugin takes one of the following three commands {start/stop/restart} as the first agument
+By default the plugin starts the server on port 8088. This can however be changed with the
+port argument.
+
+This means after starting `lightningd` together with the plugin you can run:
+`lightning-cli donationserver start` and access the server at
+http://localhost:33506/donation (in case you run your lightning node at
+`localhost`)
+
+## About the plugin
+You can see a demo of the plugin on the [authors website][rene-donations]:
+
+
+This plugin was created and is maintained by Rene Pickhardt. Thus Rene Pickhardt
+is the copyright owner of this plugin. It shall serve as an educational resource
+on his [Youtube channel][rene-youtube].
+
+The plugin is licensed like the rest of c-lightning with BSD-MIT license
+and comes without any warrenty.
+
+If you like my work feel free to support me on [patreon][rene-patreon].
+
+[rene-donations]: https://ln.rene-pickhardt.de/donation
+[rene-patreon]: https://www.patreon.com/renepickhardt
+[rene-youtube]:  https://www.youtube.com/user/RenePickhardt

donations/donations.py

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+#!/usr/bin/env python3
+""" A small donation service so that users can request ln invoices
+
+This plugin spins up a small flask server that provides a form to 
+users who wish to donate some money to the owner of the lightning
+node. The server can run on an arbitrary port and returns an invoice. 
+Also a list of previously paid invoices (only those that used this
+service) will be displayed. Displaying paid invoices could be made
+optionally in a future version. 
+
+Author: Rene Pickhardt (https://ln.rene-pickhardt.de)
+
+you can see a demo of the plugin (and leave a tip) directly at:
+       https://ln.rene-pickhardt.de/donation
+
+LICENSE: MIT / APACHE
+"""
+import base64
+import json
+import multiprocessing
+import qrcode
+import sys
+
+
+from flask import Flask, render_template
+from flask_bootstrap import Bootstrap
+from flask_wtf import FlaskForm
+from io import BytesIO
+from lightning import LightningRpc, Plugin
+from os.path import join
+from random import random
+from time import time
+from wtforms import StringField,  SubmitField, IntegerField
+from wtforms.validators import Required, NumberRange
+
+
+plugin = Plugin()
+
+
+class DonationForm(FlaskForm):
+    """Form for donations """
+    amount = IntegerField("Enter how many Satoshis you want to donate!",
+                          validators=[Required(), NumberRange(min=1, max=16666666)])
+    description = StringField("Leave a comment (displayed publically)")
+    submit = SubmitField('Donate')
+
+
+def make_base64_qr_code(bolt11):
+    qr = qrcode.QRCode(
+        version=1,
+        error_correction=qrcode.constants.ERROR_CORRECT_H,
+        box_size=4,
+        border=4,
+    )
+
+    qr.add_data(bolt11)
+    qr.make(fit=True)
+    img = qr.make_image()
+
+    buffered = BytesIO()
+    img.save(buffered, format="PNG")
+    img_str = base64.b64encode(buffered.getvalue()).decode("utf-8")
+    return img_str
+
+
+def ajax(label):
+    global plugin
+    msg = plugin.rpc.listinvoices(label)["invoices"][0]
+    if msg["status"] == "paid":
+        return "Your donation has been received and is well appricated."
+    return "waiting"
+
+
+def donation_form():
+    global plugin
+    form = DonationForm()
+    b11 = None
+    qr = None
+    label = None
+    if form.validate_on_submit():
+        amount = form.amount.data
+        description = form.description.data
+        label = "ln-plugin-donation-{}".format(random())
+        invoice = plugin.rpc.invoice(
+            int(amount)*1000, label, description)
+        b11 = invoice["bolt11"]
+        qr = make_base64_qr_code(b11)
+
+    invoices = plugin.rpc.listinvoices()["invoices"]
+    donations = []
+    for invoice in invoices:
+        if invoice["label"].startswith("ln-plugin-donation-"):
+            # FIXME: change to paid after debugging
+            if invoice["status"] == "paid":
+                bolt11 = plugin.rpc.decodepay(invoice["bolt11"])
+                satoshis = int(bolt11["msatoshi"])//1000
+                description = bolt11["description"]
+                ts = bolt11["created_at"]
+                donations.append((ts, satoshis, description))
+
+    if b11 is not None:
+        return render_template("donation.html", donations=sorted(donations, reverse=True), form=form, bolt11=b11, qr=qr, label=label)
+    else:
+        return render_template("donation.html", donations=sorted(donations, reverse=True), form=form)
+
+
+def worker(port):
+    app = Flask(__name__)
+    # FIXME: use hexlified hsm secret or something else
+    app.config['SECRET_KEY'] = 'you-will-never-guess-this'
+    app.add_url_rule('/donation', 'donation',
+                     donation_form, methods=["GET", "POST"])
+    app.add_url_rule('/is_invoice_paid/<label>', 'ajax', ajax)
+    bootstrap = Bootstrap(app)
+    app.run("0.0.0.0", port=port)
+    return
+
+
+jobs = {}
+
+
+def start_server(port):
+    if port in jobs:
+        return False, "server already running"
+
+    p = multiprocessing.Process(
+        target=worker, args=[port], name="server on port {}".format(port))
+    p.daemon = True
+
+    jobs[port] = p
+    p.start()
+
+    return True
+
+
+def stop_server(port):
+    if port in jobs:
+        jobs[port].terminate()
+        del jobs[port]
+        return True
+    else:
+        return False
+
+
+@plugin.method('donationserver')
+def donationserver(request, command="start", port=8088):
+    """Starts a donationserver with {start/stop/restart} on {port}.
+
+    A Simple HTTP Server is created that can serve a donation webpage and
+    allow to issue invoices.  The plugin takes one of the following three
+    commands {start/stop/restart} as the first agument By default the plugin
+    starts the server on port 8088. This can however be changed with the port
+    argument.
+
+    """
+    commands = {"start", "stop", "restart", "list"}
+
+    # if command unknown make start our default command
+    if command not in commands:
+        command = "start"
+
+    # if port not an integer make 8088 as default
+    try:
+        port = int(port)
+    except:
+        port = int(plugin.options['donation-web-port']['value'])
+
+    if command == "list":
+        return "servers running on the following ports: {}".format(list(jobs.keys()))
+
+    if command == "start":
+        if port in jobs:
+            return "Server already running on port {}. Maybe restart the server?".format(port)
+        suc = start_server(port)
+        if suc:
+            return "started server successfully on port {}".format(port)
+        else:
+            return "Could not start server on port {}".format(port)
+
+    if command == "stop":
+        if stop_server(port):
+            return "stopped server on port{}".format(port)
+        else:
+            return "could not stop the server"
+
+    if command == "restart":
+        stop_server(port)
+        suc = start_server(port)
+        if suc:
+            return "started server successfully on port {}".format(port)
+        else:
+            return "Could not start server on port {}".format(port)
+
+plugin.add_option(
+    'donation-autostart',
+    'true',
+    'Should the donation server start automatically'
+)
+
+plugin.add_option(
+    'donation-web-port',
+    '33506',
+    'Which port should the donation server listen to?'
+)
+
+
+@plugin.init()
+def init(options, configuration, plugin):
+    port = int(options['donation-web-port'])
+
+    if options['donation-autostart'].lower() in ['true', '1']:
+        start_server(port)
+
+
+plugin.run()

donations/requirements.txt

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+qrcode==6.1
+flask-bootstrap==3.3.7.1
+flask-wtf==0.14.2
+pillow==5.4.1

donations/templates/donation.html

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+{% extends 'bootstrap/base.html' %}
+{% import 'bootstrap/wtf.html' as wtf %}
+
+{% block title %}
+    Lightning Donations
+{% endblock %}
+
+{% block navbar %}
+    <nav class="navbar navbar-default">
+        ... navigation bar here (see complete code on GitHub) ...
+    </nav>
+{% endblock %}
+
+{% block content %}
+    <div class="container">
+      <h1>Leave a donation to support my work!</h1>
+      {% if bolt11 %}
+      <div id="target_div">
+	<div>
+	  <input type="text" value="{{bolt11}}" id="bolt11">
+	  <button onclick="copyFunction()">Copy invoice</button>
+	</div>
+	<div>
+	  <img src="data:image/png;base64,{{qr}}" />
+	</div>
+      </div>
+  {% else %}
+	{{ wtf.quick_form(form) }}
+  {% endif %}
+  <h2>Most recent donations & comments</h2>
+  <ul>
+    {% for item in donations %}
+        <li>{{ item[1] }} Satoshi. Message: {{ item[2] }}</a></li>
+    {% endfor %}
+</ul>
+<p>The above texts come from a community of unknown users. If you think they violate against your copyrite please <a href="https://www.rene-pickhardt.de/imprint" rel="nofollow"> contact me</a> so that I can remove those comments. According to the German law I am not responsible for Copyright violations rising from user generated content unless you notify me and I don't react.</p>
+
+<hr>
+<p>
+  c-lightning invoice query service for donations and spontanious payments is brought to you by
+  <a href="https://ln.rene-pickhardt.de">Rene Pickhardt</a>.</p>
+
+<p>
+If you want to learn more about the Lightning network (for beginners and for developers) check out
+  <a href="https://www.youtube.com/user/RenePickhardt">his youtube channel</a>.
+</p>
+<p>
+  Find the source code for this plugin at: <a href="https://github.com/ElementsProject/lightning/tree/master/contrib/plugins/donations">https://github.com/ElementsProject/lightning/tree/master/contrib/plugins/donations</a>
+</p>
+</div>
+{% endblock %}
+{% block scripts %}
+{{super()}}
+<script>
+var interval = null;
+$(document).on('ready',function(){
+    interval = setInterval(updateDiv,3000);
+});
+
+function updateDiv(){
+    $.ajax({
+        url: '/is_invoice_paid/{{label}}',
+        success: function(data){
+               if (data != "waiting") {
+                            var tc = document.getElementById("target_div");
+                            tc.innerHTML = data;
+                            clearInterval(interval);
+                        }
+        }
+    });
+}
+
+function copyFunction() {
+    document.getElementById("bolt11").select();
+    document.execCommand("copy");
+    alert("Copied invoice to clipboard.");
+}
+</script>
+{% endblock %}