I'd start by having a look at the front brakes to see if the left is working properly or the right is seized on. (You might not even feel it if one of the rears isnt working). The 'long pedal' may just be you need new pads. But a hot brake can cause the fluid to boil and you end up with air in the system. With the engine running, does the pedal 'come up' if you pump it?