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135 lines
3.9 KiB
135 lines
3.9 KiB
from flask import Flask, jsonify, request, render_template, escape
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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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graph = {
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# "A": {"B":10},
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# "B": {"E":10, "D":10, "C":10, "A":10},
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# "C": {"B":10, "D":10},
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# "D": {"B":10, "C":10},
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# "E": {"B":10}
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}
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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}
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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}
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path_from_a_to[node_a] = [node_a]
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for i in range(len(graph.keys())-1):
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for s,e in [(s,e) for s in graph for e in graph[s]]:
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if from_a_to[s] + graph[s][e] < from_a_to[e]:
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path_from_a_to[e] = path_from_a_to[s] + [e]
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from_a_to[e] = from_a_to[s] + graph[s][e]
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return path_from_a_to[node_b]
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def error(message):
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return jsonify({"error": message})
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def edges_to_json(graph):
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return_list = []
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done = []
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for s in graph:
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for e in graph[s]:
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if (e,s) not in done:
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return_list.append({"start":s,"end":e,"weight":graph[s][e]})
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done.append((s,e))
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return return_list
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@app.route('/api/paths/<start>/<end>', methods=['GET'])
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def get_path(start, end):
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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:
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return error("Start node does not exist."), 400
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if end not in graph:
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return error("End node does not exist."), 400
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path = bellmann_ford(graph, start, end)
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if len(path) == 0:
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return error("There exists no path."), 400
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return jsonify({'path': path})
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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.keys()})
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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)})
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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:
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return error(f'Node with name "{escape(name)}" already exist.'), 400
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graph[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:
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return error("Start node does not exist."), 400
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if end not in graph:
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return error("End node does not exist."), 400
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if start in graph and end in graph[start]:
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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[start][end] = weight
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graph[end][start] = 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=list(graph.keys()), edges=edges_to_json(graph))
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if __name__ == '__main__':
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app.run(host="0.0.0.0", debug=True, port=5000)
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