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116 lines
3.3 KiB
116 lines
3.3 KiB
from flask import Flask, jsonify, request, render_template
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import numpy as np
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app = Flask(__name__)
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app.template_folder = "frontend/"
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app.static_folder = "frontend/assets/"
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class Graph(object):
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nodes = set() # set of strings
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edges = dict() # (string,string) -> float
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def bellmann_ford(graph, node_a, node_b):
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"""Calculate distance from node_a to node_b assuming no negative cycles."""
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# weights
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from_a_to = {**[(node, np.inf) for node in graph.nodes]}
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from_a_to[node_a] = 0
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# save path so we dont have to backtrace later
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path_from_a_to = {**[(node, []) for node in graph.nodes]}
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path_from_a_to[node_a] = [node_a]
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for i in range(len(graph.nodes)-1):
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for e in graph.edges:
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# because edges are not directed
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for (x,y) in [e,e[::-1]]:
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if from_a_to[x] + graph.edges[(x,y)] < from_a_to[y]:
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path_from_a_to[y] = path_from_a_to + [y]
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from_a_to[y] = from_a_to[x] + graph.edges[(x,y)]
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return path_from_a_to[node_b]
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graph = Graph()
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def error(message):
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return jsonify({"error": message})
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def edges_to_json(edges):
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return_list = []
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for e in edges:
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return_list.append({"start":e[0],"end":e[1],"weight":edges[e]})
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return return_list
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@app.route('/api/nodes', methods=['GET'])
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def get_nodes():
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return jsonify({'nodes': graph.nodes})
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@app.route('/api/edges', methods=['GET'])
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def get_edges():
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return jsonify({'edges': edges_to_json(graph.edges)})
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@app.route('/api/nodes', methods=['POST'])
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def create_node():
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if not request.json:
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return error("Request needs to be JSON."), 400
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if 'name' not in request.json:
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return error("Name must be set."), 400
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name = request.json['name']
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if name == "":
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return error("Name cannot be empty."), 400
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if name in graph.nodes:
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return error(f'Node with name "{name}" already exist.'), 400
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graph.nodes.add(name)
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return jsonify(name), 201
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@app.route('/api/edges', methods=['POST'])
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def create_edge():
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if not request.json:
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return error("Request needs to be JSON."), 400
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if 'start' not in request.json:
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return error("Start node must be set."), 400
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if 'end' not in request.json:
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return error("End node must be set."), 400
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if 'weight' not in request.json:
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return error("Edge weight must be set."), 400
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start = request.json['start']
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end = request.json['end']
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weight = request.json['weight']
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try:
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weight = float(weight)
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except ValueError:
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return error("Weight must be a number."), 400
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if weight < 0:
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return error("Weight must be positive."), 400
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if start == end:
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return error("Start and end node must be different."), 400
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if start not in graph.nodes:
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return error("Start node does not exist."), 400
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if end not in graph.nodes:
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return error("End node does not exist."), 400
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if (start,end) in graph.edges or (end,start) in graph.edges:
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return error("Edge already exists."), 400
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edge = {"start":start,"end":end, "weight": weight}
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graph.edges[(start,end)] = weight
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return jsonify(edge), 201
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@app.route("/")
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def index():
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return render_template("index.html", nodes=graph.nodes, edges=edges_to_json(graph.edges))
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if __name__ == '__main__':
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app.run(host="127.0.0.1", debug=True, port=5000)
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