Chat bot to add all occurrences of a string.

I am wanting to write a simple chatbot that polls a chat and adds up all occurrences of a string at the end of the day and displays how many it was.

Example. Chat bot monitors a chat thread, check every so often for new occurrences of X and adds its to the running total. at the end of the day lets say midnight is writes a message the number of times X was mentioned that day.

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I dont really know where to start with this however I am a computer engineer and very tech savy. any insight would be great.