A stateful chatbot to capture data in 50 lines of Ruby

chatbot.rb

# https://medium.com/cleartax-engineering/a-simple-rule-based-stateful-chatbot-for-data-capture-ebfad9271388

require 'ostruct'

# Track the current state of the conversation
state = {pointer: ""}

# Metadata is used to fill the outgoing templates AND store the captured data from conversation
metadata = {name: "Calvin"}

# Build the conversation tree from bottom up
# Each node has the outgoing message and incoming message patterns
# next_node pointer is where the conversation will jump to if the pattern matches

last = OpenStruct.new({
  outgoing: "Congrats on your %{age}th year",
  incoming: []
})

second = OpenStruct.new({
  outgoing: "Ok %{name}, how old are you?",
  incoming: [
    OpenStruct.new({pattern: /(?<age>\d+)/, next_node: last})
  ]
})

# Root of the conversation tree
$chat_tree = OpenStruct.new({
  outgoing: "Hi %{name}, is that you?",
  incoming: [
    OpenStruct.new({pattern: /(y|Y|yes|YES)/, next_node: second}),
    OpenStruct.new({pattern: /(no|NO)/, next_node: last})
  ]
})

def tree_lookup(node_pointer)
  node = $chat_tree
  node_pointer.split("/").reject(&:empty?).each do |idx|
    resp = node.incoming[idx.to_i]
    node = resp.next_node || tree_lookup(resp.next_node_id)
  end
  return node
end

def process(message, state, metadata)
  node = tree_lookup(state[:pointer])
  resp = node.incoming.select { |r| message.match(r.pattern) }.first
  
  if resp
    resp_index = node.incoming.index(resp)
    state.merge! message.match(resp.pattern).named_captures.inject({}){|memo, (k,v)| memo[k.to_sym] = v; memo}
    state[:pointer] += "/#{resp_index}"
    puts "state = #{state.inspect}"
    puts resp.next_node.outgoing % state.merge(metadata)
  else
    puts "Sorry, I didn't understand. Try again?"
  end
end

puts $chat_tree.outgoing % state.merge(metadata)
while true do
  msg = gets.chomp
  process(msg, state, metadata)
end