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TU_Assignment/main.py

116 lines
3.3 KiB

from flask import Flask, jsonify, request, render_template
import numpy as np
app = Flask(__name__)
app.template_folder = "frontend/"
app.static_folder = "frontend/assets/"
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})
def edges_to_json(edges):
return_list = []
for e in edges:
return_list.append({"start":e[0],"end":e[1],"weight":edges[e]})
return return_list
@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': edges_to_json(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']
try:
weight = float(weight)
except ValueError:
return error("Weight must be a number."), 400
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 already exists."), 400
edge = {"start":start,"end":end, "weight": weight}
graph.edges[(start,end)] = weight
return jsonify(edge), 201
@app.route("/")
def index():
return render_template("index.html", nodes=graph.nodes, edges=edges_to_json(graph.edges))
if __name__ == '__main__':
app.run(host="127.0.0.1", debug=True, port=5000)