If you want the extremely brief version of the history, Canada was kind of a thing but not officially until 1867, with the British North America Act, making it officially a country but still a Dominion of the United Kingdom.

In 1949, the Supreme Court of Canada disconnected itself from the British one.

In 1982 the Constitution Act formally removed the power of British Parliament to override the Canadian Parliament, enacted a Constitution and more or less fully established Canada as independent from the UK, in every matter except specific ones relating to the Head of State and the Crown. The Crown’s powers are vested in the Governor General and Lieutenant Governors, and they play very important, but mostly ceremonial roles today.