Backend with restapi

5 years ago · 43ef16c103
commit 43ef16c103
2 changed files with 120 additions and 0 deletions
--- a/main.py
+++ b/main.py
@ -0,0 +1,107 @@
+from flask import Flask, jsonify, request, render_template
+import numpy as np
+
+app = Flask(__name__)
+
+
+class Graph(object):
+    nodes = set()   # set of strings
+    edges = dict()  # (string,string) -> float
+
+
+def bellmann_ford(graph, node_a, node_b):
+    """Calculate distance from node_a to node_b assuming no negative cycles."""
+    # weights
+    from_a_to = {**[(node, np.inf) for node in graph.nodes]}
+    from_a_to[node_a] = 0
+    # save path so we dont have to backtrace later
+    path_from_a_to = {**[(node, []) for node in graph.nodes]}
+    path_from_a_to[node_a] = [node_a]
+
+    for i in range(len(graph.nodes)-1):
+        for e in graph.edges:
+            # because edges are not directed
+            for (x,y) in [e,e[::-1]]:
+                if from_a_to[x] + graph.edges[(x,y)] < from_a_to[y]:
+                    path_from_a_to[y] = path_from_a_to + [y]
+                    from_a_to[y] = from_a_to[x] + graph.edges[(x,y)]
+
+    return path_from_a_to[node_b]
+
+
+graph = Graph()
+
+
+def error(message):
+    return jsonify({"error": message})
+
+
+@app.route('/api/nodes', methods=['GET'])
+def get_nodes():
+    return jsonify({'nodes': graph.nodes})
+
+
+@app.route('/api/edges', methods=['GET'])
+def get_edges():
+    return jsonify({'edges': graph.edges})
+
+
+@app.route('/api/nodes', methods=['POST'])
+def create_node():
+    if not request.json:
+        return error("Request needs to be JSON."), 400
+    if 'name' not in request.json:
+        return error("Name must be set."), 400
+
+    name = request.json['name']
+    if name == "":
+        return error("Name cannot be empty."), 400
+    if name in graph.nodes:
+        return error(f'Node with name "{name}" already exist.'), 400
+
+    graph.nodes.add(name)
+    return jsonify(name), 201
+
+
+@app.route('/api/edges', methods=['POST'])
+def create_edge():
+    if not request.json:
+        return error("Request needs to be JSON."), 400
+    if 'start' not in request.json:
+        return error("Start node must be set."), 400
+    if 'end' not in request.json:
+        return error("End node must be set."), 400
+    if 'weight' not in request.json:
+        return error("Edge weight must be set."), 400
+
+    start = request.json['start']
+    end = request.json['end']
+    weight = request.json['weight']
+    if weight < 0:
+        return error("Weight must be positive."), 400
+    if start == end:
+        return error("Start and end node must be different."), 400
+    if start not in graph.nodes:
+        return error("Start node does not exist."), 400
+    if end not in graph.nodes:
+        return error("End node does not exist."), 400
+    if (start,end) in graph.edges or (end,start) in graph.edges:
+        return error("Edge exists already."), 400
+    try:
+        weight = float(weight)
+    except ValueError:
+        return error("Weight must be a number."), 400
+
+    edge = {(start,end): weight}
+    graph.edges[(start,end)] = weight
+
+    return jsonify(edge), 201
+
+
+@app.route("/")
+def index():
+    return render_template("index.html", nodes=graph.nodes, edges=graph.edges)
+
+
+if __name__ == '__main__':
+    app.run(host="127.0.0.1", debug=True, port=5000)
--- a/templates/index.html
+++ b/templates/index.html
@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html lang="de" dir="ltr">
+  <head>
+    <meta charset="utf-8">
+    <title>Assignment</title>
+  </head>
+  <body>
+    <p><b>nodes:</b> {{ nodes }}</p>
+    <p><b>edges:</b> {{ edges }}</p>
+    <div ></div>
+    <script src="{{ url_for('static', filename='js/canvas.js')}}"></script>
+  </body>
+</html>