PA-28 pilot reported an NMAC occurred on final approach when another aircraft took off from the opposite end runway against the traffic flow.

Narrative

I was the pilot of Aircraft X. I was conducting a return flight to ZZZ from ZZZ1. I did the ILS XX Practice Approach at ZZZ2 during my return to ZZZ. After my practice approach; I was approaching ZZZ from the south under visual flight rules. The wind at ZZZ was reported as calm. I intended to make a straight in approach to Runway XY. As I tuned CTAF; there was another plane in the pattern that was landing [Runway] XZ [opposite end]. I adjusted my path to go west of the field and prepared to do a 45 degree entry to the right downwind for Runway XZ (XZ is RP). As I approached the field; I made an initial call at 6 miles south; 5;900 ft; just below the Bravo airspace. I made an additional call as I was established on the 45 for right downwind XZ. After I made the 45 degree call; another plane on the field; a twin-engine Piper; announced they were taxiing bravo to hold short XZ; keeping with the flow of traffic. I made another call once established right downwind XZ. As I turned base; another plane; Aircraft Y; made a call that they were taking off XY. I assumed they announced the wrong runway; but a quick glance at the hold short line XY confirmed they were indeed intending to take XY.The pilot of the other aircraft took off against the flow of traffic. When I announced I was on the base leg of the opposite direction runway; he continued to take off; and did not communicate until he was 100 feet from my plane at the same altitude.