Chord detection from notes plugin

Hi, I am interested in developing a plugin that can guess chord based on notes in measures, the chords will be calculated/guessed measure by measure (bar by bar), which may be useful for monophonic and pop songs. I want to ask is there already some works like this, since I cant find any plugin like this yet. Beside that, I am also new in developing plugin, is there any suggestions/guides/tutorials for me?