commit df3aa7fdcd2a0f9a180179e6f7e8626248a2d8b4
Author: Burathar <Burathar@gmail.com>
Date:   Wed Dec 16 13:10:34 2020 +0100

    Initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..29bb024
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,144 @@
+# Source: https://github.com/github/gitignore/blob/master/Python.gitignore
+
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+app.db
+.vscode/
+
diff --git a/app/__init__.py b/app/__init__.py
new file mode 100644
index 0000000..e686d47
--- /dev/null
+++ b/app/__init__.py
@@ -0,0 +1,47 @@
+from flask import Flask
+from config import Config
+from flask_sqlalchemy import SQLAlchemy
+from flask_migrate import Migrate
+from flask_bootstrap import Bootstrap
+import logging
+from logging.handlers import SMTPHandler, RotatingFileHandler
+import os
+
+app = Flask(__name__)
+app.config.from_object(Config)
+db = SQLAlchemy(app)
+migrate = Migrate(app, db)
+bootstrap = Bootstrap(app)
+
+
+from app import routes, models, errors, database_cleaner
+
+if not app.debug:
+    # Mail errors
+    if app.config['MAIL_SERVER']:
+        auth = None
+        if app.config['MAIL_USERNAME'] or app.config['MAIL_PASSWORD']:
+            auth = (app.config['MAIL_USERNAME'], app.config['MAIL_PASSWORD'])
+        secure = None
+        if app.config['MAIL_USE_TLS']:
+            secure = () # The secure argument is an empty tuple to use TLS without providing a specific certificate and key.
+        mail_handler = SMTPHandler(
+                mailhost=(app.config['MAIL_SERVER'], app.config['MAIL_PORT']),
+                fromaddr='no-reply@' + app.config['MAIL_SERVER'],
+                toaddrs=app.config['ADMINS'], subject='Microblog Failure',
+                credentials=auth, secure=secure)
+        mail_handler.setLevel(logging.ERROR)
+        app.logger.addHandler(mail_handler)
+    # Log to File
+    if not os.path.exists('logs'):
+        os.mkdir('logs')
+    file_handler = RotatingFileHandler('logs/linkshortener.log', maxBytes=10240, backupCount=10)
+    file_handler.setFormatter(logging.Formatter(
+        '%(asctime)s %(levelname)s: %(message)s'))
+    file_handler.setLevel(logging.INFO)
+    app.logger.addHandler(file_handler)
+
+    app.logger.setLevel(logging.INFO)
+    app.logger.info('Link Shortener startup')
+
+database_cleaner.start_scheduler()
diff --git a/app/database_cleaner.py b/app/database_cleaner.py
new file mode 100644
index 0000000..0faef0f
--- /dev/null
+++ b/app/database_cleaner.py
@@ -0,0 +1,46 @@
+import time
+from apscheduler.schedulers.background import BackgroundScheduler
+import atexit
+from datetime import datetime
+
+from app import app, db
+from app.models import Url
+
+def remove_dead_urls():
+    for url in Url.query.all():
+        check_url(url)
+
+def check_url(url):
+    if url.death is not None:
+        if datetime.now() > url.death :
+            app.logger.info(f"Removed hash '{url.hash}'' because its retention time has passed.")
+            db.session.delete(url)
+            db.session.commit()
+            return "Timeout"
+    if url.view_counter is not None:
+        if url.view_counter <= 0:
+            app.logger.info(f"Removed hash '{url.hash}'' because its viewcouner has run out.")
+            db.session.delete(url)
+            db.session.commit()
+            return "Counter"
+    return None
+
+scheduler = None
+
+def start_scheduler():
+    global scheduler
+    if scheduler is not None:
+        app.logger.info("Database_cleaner scheduler was already started, not launching a second instane.")
+        return
+    scheduler = BackgroundScheduler()
+    scheduler.add_job(func=remove_dead_urls, trigger="interval", hours=1)
+    scheduler.start()
+    app.logger.info("Database_cleaner scheduler was started.")
+
+    # Shut down the scheduler when exiting the app
+    atexit.register(shutdown_scheduler)
+
+def shutdown_scheduler():
+    scheduler.shutdown()
+    app.logger.info("Database_cleaner scheduler was shut down.")
+    
\ No newline at end of file
diff --git a/app/errors.py b/app/errors.py
new file mode 100644
index 0000000..989fc38
--- /dev/null
+++ b/app/errors.py
@@ -0,0 +1,12 @@
+from flask import render_template
+from app import app
+
+@app.errorhandler(404)
+def not_found_error(error):
+    return render_template('404.html'), 404
+
+@app.errorhandler(500)
+def internal_error(error):
+    return render_template('500.html'), 500
+    db.session.rollback()
+
diff --git a/app/forms.py b/app/forms.py
new file mode 100644
index 0000000..96a0f4b
--- /dev/null
+++ b/app/forms.py
@@ -0,0 +1,9 @@
+from flask_wtf import FlaskForm
+from wtforms import StringField, IntegerField, SelectField, SubmitField
+from wtforms.validators import DataRequired, NumberRange, Required
+
+class UrlForm(FlaskForm):
+    url = StringField('Url', validators=[DataRequired()])
+    retention = IntegerField('Retention', default=5, validators = [NumberRange(min=0, max=100)])
+    retention_type = SelectField('Retention', choices = [ 'Minute', 'Hour', 'Day', 'Time'], default=2, validators = [Required()]) 
+    submit = SubmitField('Shorten Url')
diff --git a/app/models.py b/app/models.py
new file mode 100644
index 0000000..35476d2
--- /dev/null
+++ b/app/models.py
@@ -0,0 +1,16 @@
+from datetime import datetime
+from app import app, db
+
+class Url(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    url = db.Column(db.String(2000), nullable=False)
+    hash = db.Column(db.String(20), index=True, unique=True, nullable=False)
+    birth = db.Column(db.DateTime, default=datetime.utcnow)
+    death = db.Column(db.DateTime)
+    view_counter = db.Column(db.Integer)
+
+    def __init__(self, **kwargs):
+        super(Url, self).__init__(**kwargs)
+
+        if not self.url.lower().startswith(('http://', 'https://')):
+            self.url = f'https://{self.url}'
diff --git a/app/routes.py b/app/routes.py
new file mode 100644
index 0000000..7b3f1b2
--- /dev/null
+++ b/app/routes.py
@@ -0,0 +1,76 @@
+from datetime import datetime, timedelta
+from secrets import token_urlsafe
+
+from flask import render_template, flash, redirect, url_for, abort, request, Markup
+from app import app, db
+from app.forms import UrlForm
+from app.models import Url
+from app.database_cleaner import check_url
+
+domain = 'http://127.0.0.1:5000'
+
+@app.before_request
+def before_request():
+    pass
+
+@app.route('/index', methods=['GET', 'POST'])
+def index():
+    form = UrlForm()
+    if form.validate_on_submit():
+        hash = getHash()
+        if hash is None:
+            return redirect(url_for('index'))
+
+        death = calcDeath(form.retention.data, form.retention_type.data)
+        view_counter = None if form.retention_type.data != "Time" else form.retention.data
+        if death is None and view_counter is None:
+            app.logger.warning("Neither death nor view_counter was recieved for url")
+            flash('Please specify a retention time')
+            return redirect(url_for('index'))
+
+        url = Url(url = form.url.data.strip(), hash=hash, death=death, view_counter=view_counter)
+        db.session.add(url)
+        db.session.commit()
+        death = None if url.death is None else url.death.strftime('%Y-%m-%d %H:%M:%S')
+        app.logger.info(f"{request.environ['REMOTE_ADDR']} created hash '{url.hash}' for '{url.url}'. Death: {death}, View Counter: {url.view_counter}")
+        link = url_for("resolve_hash", hash=hash, _external = True)
+        flash(Markup(f'Your url is shortend to <a href="{link}">{link}</a>'))
+        return redirect(url_for('index'))
+    return render_template("index.html", form=form)
+
+def getHash():
+    for i in range(200):
+        hash = token_urlsafe(3)
+        url = Url.query.filter_by(hash=hash).first()
+        if (url is None and url != 'index'):
+            return hash
+
+    flash('Failed generating a unique hash. Please try again.')
+    return None
+
+def calcDeath(retention, retention_type):
+    if retention_type == 'Minute':
+        return datetime.now() + timedelta(minutes=retention)
+    if retention_type == 'Hour':
+        return datetime.now() + timedelta(hours=retention)
+    if retention_type == 'Day':
+        return datetime.now() + timedelta(days=retention)
+    if retention_type == 'Time':
+        return None
+    app.logger.error(f"Retention_type out of range: '{retention_type}'")
+
+@app.route('/', defaults={'hash' : 'index'})
+@app.route('/<hash>')
+def resolve_hash(hash):
+    if hash == 'index':
+        return redirect(url_for('index'))
+
+    url = Url.query.filter_by(hash=hash).first_or_404()
+    if check_url(url) is None:
+        if url.view_counter is not None:
+            url.view_counter -= 1
+            db.session.commit()
+
+    countermessage = "" if url.view_counter is None else f". View counter was lowered to {url.view_counter}"
+    app.logger.info(f"{request.environ['REMOTE_ADDR']} requested hash '{url.hash}' which resolved to '{url.url}'{countermessage}")
+    return redirect(url.url, 301)
diff --git a/app/templates/404.html b/app/templates/404.html
new file mode 100644
index 0000000..4e77079
--- /dev/null
+++ b/app/templates/404.html
@@ -0,0 +1,7 @@
+{% extends "base.html" %}
+
+{% block app_content %}
+    <h1>File Not Found</h1>
+    <p><a href="{{ url_for('index') }}">Back</a></p>
+{% endblock %}
+
diff --git a/app/templates/500.html b/app/templates/500.html
new file mode 100644
index 0000000..9fb3d07
--- /dev/null
+++ b/app/templates/500.html
@@ -0,0 +1,8 @@
+{% extends "base.html" %}
+
+{% block app_content %}
+    <h1>An unexpected error has occurred</h1>
+    <p>The administrator has been notified. Sorry for the inconvenience!</p>
+    <p><a href="{{ url_for('index') }}">Back</a></p>
+{% endblock %}
+
diff --git a/app/templates/base.html b/app/templates/base.html
new file mode 100644
index 0000000..698a24b
--- /dev/null
+++ b/app/templates/base.html
@@ -0,0 +1,30 @@
+{% extends 'bootstrap/base.html' %}
+
+{% block title %}
+Link Shortener
+{% endblock %}
+
+{% block content %}
+<div class="container">
+  <br>
+  <div class="col-md-3"></div> 
+  <div class="col-md-5">
+    {% with messages = get_flashed_messages() %}
+    {% if messages %}
+    {% for message in messages %}
+    <div class="alert alert-info" role="alert">{{ message }}</div>
+    {% endfor %}
+    {% endif %}
+    {% endwith %}
+  
+    {# application content needs to be provided in the app_content block #}
+    {% block app_content %}{% endblock %}
+  </div>
+  
+</div>
+{% endblock %}
+
+{% block scripts %}
+{{ super() }}
+{% endblock %}
+
diff --git a/app/templates/index.html b/app/templates/index.html
new file mode 100644
index 0000000..db528e3
--- /dev/null
+++ b/app/templates/index.html
@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+{% import 'bootstrap/wtf.html' as wtf %}
+
+{% block app_content %}
+
+{% if form %}
+{{ wtf.quick_form(form, button_map={'submit': 'primary'}) }}
+<br>
+
+{% endif %}
+
+{% endblock %}
+
diff --git a/config.py b/config.py
new file mode 100644
index 0000000..733f13e
--- /dev/null
+++ b/config.py
@@ -0,0 +1,16 @@
+import os
+basedir = os.path.abspath(os.path.dirname(__file__))
+
+class Config(object):
+    SECRET_KEY = os.environ.get('SECRET_KEY') or 'you-will-never-guess'
+    SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or \
+            'sqlite:///' + os.path.join(basedir, 'app.db')
+    SQLALCHEMY_TRACK_MODIFICATIONS = False
+
+    MAIL_SERVER = os.environ.get('MAIL_SERVER')
+    MAIL_PORT = int(os.environ.get('MAIL_PORT') or 25)
+    MAIL_USE_TLS = os.environ.get('MAIL_USE_TLS') is not None
+    MAIL_USERNAME = os.environ.get('MAIL_USERNAME')
+    MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')
+    ADMINS = ['your-email@example.com']
+
diff --git a/linkshortener.py b/linkshortener.py
new file mode 100644
index 0000000..8d73323
--- /dev/null
+++ b/linkshortener.py
@@ -0,0 +1,6 @@
+from app import app, db
+from app.models import Url
+
+@app.shell_context_processor
+def make_shell_context():
+    return {'db': db, 'Url': Url}
diff --git a/migrations/README b/migrations/README
new file mode 100644
index 0000000..98e4f9c
--- /dev/null
+++ b/migrations/README
@@ -0,0 +1 @@
+Generic single-database configuration.
\ No newline at end of file
diff --git a/migrations/alembic.ini b/migrations/alembic.ini
new file mode 100644
index 0000000..f8ed480
--- /dev/null
+++ b/migrations/alembic.ini
@@ -0,0 +1,45 @@
+# A generic, single database configuration.
+
+[alembic]
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S
diff --git a/migrations/env.py b/migrations/env.py
new file mode 100644
index 0000000..9452179
--- /dev/null
+++ b/migrations/env.py
@@ -0,0 +1,96 @@
+from __future__ import with_statement
+
+import logging
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+logger = logging.getLogger('alembic.env')
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from flask import current_app
+config.set_main_option(
+    'sqlalchemy.url',
+    str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%'))
+target_metadata = current_app.extensions['migrate'].db.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url, target_metadata=target_metadata, literal_binds=True
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    # this callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema
+    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(context, revision, directives):
+        if getattr(config.cmd_opts, 'autogenerate', False):
+            script = directives[0]
+            if script.upgrade_ops.is_empty():
+                directives[:] = []
+                logger.info('No changes in schema detected.')
+
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix='sqlalchemy.',
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            process_revision_directives=process_revision_directives,
+            **current_app.extensions['migrate'].configure_args
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
diff --git a/migrations/script.py.mako b/migrations/script.py.mako
new file mode 100644
index 0000000..2c01563
--- /dev/null
+++ b/migrations/script.py.mako
@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}
diff --git a/migrations/versions/3c65fc2aac0a_initial_migration.py b/migrations/versions/3c65fc2aac0a_initial_migration.py
new file mode 100644
index 0000000..a200608
--- /dev/null
+++ b/migrations/versions/3c65fc2aac0a_initial_migration.py
@@ -0,0 +1,38 @@
+"""initial migration
+
+Revision ID: 3c65fc2aac0a
+Revises: 
+Create Date: 2020-12-15 23:06:09.507454
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '3c65fc2aac0a'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('url',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('url', sa.String(length=2000), nullable=False),
+    sa.Column('hash', sa.String(length=20), nullable=False),
+    sa.Column('birth', sa.DateTime(), nullable=True),
+    sa.Column('death', sa.DateTime(), nullable=True),
+    sa.Column('view_counter', sa.Integer(), nullable=True),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_url_hash'), 'url', ['hash'], unique=True)
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index(op.f('ix_url_hash'), table_name='url')
+    op.drop_table('url')
+    # ### end Alembic commands ###
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..2e6a167
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,32 @@
+alembic==1.4.3
+APScheduler==3.6.3
+astroid==2.4.2
+click==7.1.2
+dominate==2.6.0
+Flask==1.1.2
+Flask-Bootstrap==3.3.7.1
+Flask-Migrate==2.5.3
+Flask-SQLAlchemy==2.4.4
+Flask-WTF==0.14.3
+isort==5.6.4
+itsdangerous==1.1.0
+Jinja2==2.11.2
+lazy-object-proxy==1.4.3
+Mako==1.1.3
+MarkupSafe==1.1.1
+mccabe==0.6.1
+pylint==2.6.0
+pylint-flask-sqlalchemy==0.2.0
+python-dateutil==2.8.1
+python-dotenv==0.15.0
+python-editor==1.0.4
+pytz==2020.4
+six==1.15.0
+SQLAlchemy==1.3.20
+toml==0.10.2
+typed-ast==1.4.1
+tzlocal==2.1
+visitor==0.1.3
+Werkzeug==1.0.1
+wrapt==1.12.1
+WTForms==2.3.3