Chapter 23: Application Programming Interfaces (APIs) (v0.23)

app/__init__.py

@@ -50,6 +50,9 @@ def create_app(config_class=Config):
     from app.main import bp as main_bp
     app.register_blueprint(main_bp)
 
+    from app.api import bp as api_bp
+    app.register_blueprint(api_bp, url_prefix='/api')
+
     if not app.debug and not app.testing:
         if app.config['MAIL_SERVER']:
             auth = None

app/api/__init__.py

@@ -0,0 +1,5 @@
+from flask import Blueprint
+
+bp = Blueprint('api', __name__)
+
+from app.api import users, errors, tokens

app/api/auth.py

@@ -0,0 +1,33 @@
+from flask import g
+from flask_httpauth import HTTPBasicAuth, HTTPTokenAuth
+from flask_login import current_user
+from app.models import User
+from app.api.errors import error_response
+
+basic_auth = HTTPBasicAuth()
+token_auth = HTTPTokenAuth()
+
+
+@basic_auth.verify_password
+def verify_password(username, password):
+    user = User.query.filter_by(username=username).first()
+    if user is None:
+        return False
+    g.current_user = user
+    return user.check_password(password)
+
+
+@basic_auth.error_handler
+def basic_auth_error():
+    return error_response(401)
+
+
+@token_auth.verify_token
+def verify_token(token):
+    g.current_user = User.check_token(token) if token else None
+    return g.current_user is not None
+
+
+@token_auth.error_handler
+def token_auth_error():
+    return error_response(401)

app/api/errors.py

@@ -0,0 +1,15 @@
+from flask import jsonify
+from werkzeug.http import HTTP_STATUS_CODES
+
+
+def error_response(status_code, message=None):
+    payload = {'error': HTTP_STATUS_CODES.get(status_code, 'Unknown error')}
+    if message:
+        payload['message'] = message
+    response = jsonify(payload)
+    response.status_code = status_code
+    return response
+
+
+def bad_request(message):
+    return error_response(400, message)

app/api/tokens.py

@@ -0,0 +1,20 @@
+from flask import jsonify, g
+from app import db
+from app.api import bp
+from app.api.auth import basic_auth, token_auth
+
+
+@bp.route('/tokens', methods=['POST'])
+@basic_auth.login_required
+def get_token():
+    token = g.current_user.get_token()
+    db.session.commit()
+    return jsonify({'token': token})
+
+
+@bp.route('/tokens', methods=['DELETE'])
+@token_auth.login_required
+def revoke_token():
+    g.current_user.revoke_token()
+    db.session.commit()
+    return '', 204

app/api/users.py

@@ -0,0 +1,80 @@
+from flask import jsonify, request, url_for, g, abort
+from app import db
+from app.models import User
+from app.api import bp
+from app.api.auth import token_auth
+from app.api.errors import bad_request
+
+
+@bp.route('/users/<int:id>', methods=['GET'])
+@token_auth.login_required
+def get_user(id):
+    return jsonify(User.query.get_or_404(id).to_dict())
+
+
+@bp.route('/users', methods=['GET'])
+@token_auth.login_required
+def get_users():
+    page = request.args.get('page', 1, type=int)
+    per_page = min(request.args.get('per_page', 10, type=int), 100)
+    data = User.to_collection_dict(User.query, page, per_page, 'api.get_users')
+    return jsonify(data)
+
+
+@bp.route('/users/<int:id>/followers', methods=['GET'])
+@token_auth.login_required
+def get_followers(id):
+    user = User.query.get_or_404(id)
+    page = request.args.get('page', 1, type=int)
+    per_page = min(request.args.get('per_page', 10, type=int), 100)
+    data = User.to_collection_dict(user.followers, page, per_page,
+                                   'api.get_followers', id=id)
+    return jsonify(data)
+
+
+@bp.route('/users/<int:id>/followed', methods=['GET'])
+@token_auth.login_required
+def get_followed(id):
+    user = User.query.get_or_404(id)
+    page = request.args.get('page', 1, type=int)
+    per_page = min(request.args.get('per_page', 10, type=int), 100)
+    data = User.to_collection_dict(user.followed, page, per_page,
+                                   'api.get_followed', id=id)
+    return jsonify(data)
+
+
+@bp.route('/users', methods=['POST'])
+def create_user():
+    data = request.get_json() or {}
+    if 'username' not in data or 'email' not in data or 'password' not in data:
+        return bad_request('must include username, email and password fields')
+    if User.query.filter_by(username=data['username']).first():
+        return bad_request('please use a different username')
+    if User.query.filter_by(email=data['email']).first():
+        return bad_request('please use a different email address')
+    user = User()
+    user.from_dict(data, new_user=True)
+    db.session.add(user)
+    db.session.commit()
+    response = jsonify(user.to_dict())
+    response.status_code = 201
+    response.headers['Location'] = url_for('api.get_user', id=user.id)
+    return response
+
+
+@bp.route('/users/<int:id>', methods=['PUT'])
+@token_auth.login_required
+def update_user(id):
+    if g.current_user.id != id:
+        abort(403)
+    user = User.query.get_or_404(id)
+    data = request.get_json() or {}
+    if 'username' in data and data['username'] != user.username and \
+            User.query.filter_by(username=data['username']).first():
+        return bad_request('please use a different username')
+    if 'email' in data and data['email'] != user.email and \
+            User.query.filter_by(email=data['email']).first():
+        return bad_request('please use a different email address')
+    user.from_dict(data, new_user=False)
+    db.session.commit()
+    return jsonify(user.to_dict())

app/errors/handlers.py

@@ -1,14 +1,24 @@
-from flask import render_template
+from flask import render_template, request
 from app import db
 from app.errors import bp
+from app.api.errors import error_response as api_error_response
+
+
+def wants_json_response():
+    return request.accept_mimetypes['application/json'] >= \
+        request.accept_mimetypes['text/html']
 
 
 @bp.app_errorhandler(404)
 def not_found_error(error):
+    if wants_json_response():
+        return api_error_response(404)
     return render_template('errors/404.html'), 404
 
 
 @bp.app_errorhandler(500)
 def internal_error(error):
     db.session.rollback()
+    if wants_json_response():
+        return api_error_response(500)
     return render_template('errors/500.html'), 500

app/models.py

@@ -1,8 +1,10 @@
-from datetime import datetime
+import base64
+from datetime import datetime, timedelta
 from hashlib import md5
 import json
+import os
 from time import time
-from flask import current_app
+from flask import current_app, url_for
 from flask_login import UserMixin
 from werkzeug.security import generate_password_hash, check_password_hash
 import jwt
@@ -55,21 +57,47 @@ def reindex(cls):
 db.event.listen(db.session, 'after_commit', SearchableMixin.after_commit)
 
 
+class PaginatedAPIMixin(object):
+    @staticmethod
+    def to_collection_dict(query, page, per_page, endpoint, **kwargs):
+        resources = query.paginate(page, per_page, False)
+        data = {
+            'items': [item.to_dict() for item in resources.items],
+            '_meta': {
+                'page': page,
+                'per_page': per_page,
+                'total_pages': resources.pages,
+                'total_items': resources.total
+            },
+            '_links': {
+                'self': url_for(endpoint, page=page, per_page=per_page,
+                                **kwargs),
+                'next': url_for(endpoint, page=page + 1, per_page=per_page,
+                                **kwargs) if resources.has_next else None,
+                'prev': url_for(endpoint, page=page - 1, per_page=per_page,
+                                **kwargs) if resources.has_prev else None
+            }
+        }
+        return data
+
+
 followers = db.Table(
     'followers',
     db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
     db.Column('followed_id', db.Integer, db.ForeignKey('user.id'))
 )
 
 
-class User(UserMixin, db.Model):
+class User(UserMixin, PaginatedAPIMixin, db.Model):
     id = db.Column(db.Integer, primary_key=True)
     username = db.Column(db.String(64), index=True, unique=True)
     email = db.Column(db.String(120), index=True, unique=True)
     password_hash = db.Column(db.String(128))
     posts = db.relationship('Post', backref='author', lazy='dynamic')
     about_me = db.Column(db.String(140))
     last_seen = db.Column(db.DateTime, default=datetime.utcnow)
+    token = db.Column(db.String(32), index=True, unique=True)
+    token_expiration = db.Column(db.DateTime)
     followed = db.relationship(
         'User', secondary=followers,
         primaryjoin=(followers.c.follower_id == id),
@@ -160,6 +188,52 @@ def get_task_in_progress(self, name):
         return Task.query.filter_by(name=name, user=self,
                                     complete=False).first()
 
+    def to_dict(self, include_email=False):
+        data = {
+            'id': self.id,
+            'username': self.username,
+            'last_seen': self.last_seen.isoformat() + 'Z',
+            'about_me': self.about_me,
+            'post_count': self.posts.count(),
+            'follower_count': self.followers.count(),
+            'followed_count': self.followed.count(),
+            '_links': {
+                'self': url_for('api.get_user', id=self.id),
+                'followers': url_for('api.get_followers', id=self.id),
+                'followed': url_for('api.get_followed', id=self.id),
+                'avatar': self.avatar(128)
+            }
+        }
+        if include_email:
+            data['email'] = self.email
+        return data
+
+    def from_dict(self, data, new_user=False):
+        for field in ['username', 'email', 'about_me']:
+            if field in data:
+                setattr(self, field, data[field])
+        if new_user and 'password' in data:
+            self.set_password(data['password'])
+
+    def get_token(self, expires_in=3600):
+        now = datetime.utcnow()
+        if self.token and self.token_expiration > now + timedelta(seconds=60):
+            return self.token
+        self.token = base64.b64encode(os.urandom(24)).decode('utf-8')
+        self.token_expiration = now + timedelta(seconds=expires_in)
+        db.session.add(self)
+        return self.token
+
+    def revoke_token(self):
+        self.token_expiration = datetime.utcnow() - timedelta(seconds=1)
+
+    @staticmethod
+    def check_token(token):
+        user = User.query.filter_by(token=token).first()
+        if user is None or user.token_expiration < datetime.utcnow():
+            return None
+        return user
+
 
 @login.user_loader
 def load_user(id):

migrations/versions/834b1a697901_user_tokens.py

@@ -0,0 +1,32 @@
+"""user tokens
+
+Revision ID: 834b1a697901
+Revises: c81bac34faab
+Create Date: 2017-11-05 18:41:07.996137
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '834b1a697901'
+down_revision = 'c81bac34faab'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('user', sa.Column('token', sa.String(length=32), nullable=True))
+    op.add_column('user', sa.Column('token_expiration', sa.DateTime(), nullable=True))
+    op.create_index(op.f('ix_user_token'), 'user', ['token'], unique=True)
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index(op.f('ix_user_token'), table_name='user')
+    op.drop_column('user', 'token_expiration')
+    op.drop_column('user', 'token')
+    # ### end Alembic commands ###

requirements.txt

@@ -9,6 +9,7 @@ elasticsearch==7.5.1
 Flask==1.0.2
 Flask-Babel==0.11.2
 Flask-Bootstrap==3.3.7.1
+Flask-HTTPAuth==3.2.3
 Flask-Login==0.4.0
 Flask-Mail==0.9.1
 Flask-Migrate==2.1.1