Free and Open Source Software

Hi everyone! Due to so many projects I'm involved into, I need an easy way to organize and visualize tasks, dependencies, and durations in order to properly plan my week.

I'm looking for an organizer app that fulfills the following requirements:

• must have a calendar management systems
• it must support multiple caldav calendars at the same time
• must have a to-do list
• each time the user creates a to-do element, they should have the option to reserve a specific time on the calendar
• when they decide to reserve a specific time on the calendar, the calendar might be chosen among the multiple support ones
• to-do tasks might be visualized as a mindmap
• for every leaf / "outer children" of the mindmap, must correspond a to-do element with the specific calendar

Does anybody knows something that does all of this?

Thank you