A320 First Officer reported that the landing gear and doors did not retract after takeoff and the aircraft lost all fluid in the green hydraulic system. The flight crew left the gear extended and returned to the departure airport where after landing they were towed to the gate.

Narrative

With the Captain flying and I performing PM duties; Aircraft Y departed Runway XXR out of ZZZ. Shortly after take-off; the Captain said 'Gear Up' and I went to retract the landing gear. Upon moving the gear handle; we received an ECAM of HYD G Eng 1 Pump Lo Pr and the landing gear and doors did not retract. The Captain put on the autopilot and we cleaned up the flaps and maintained an airspeed of 205 KIAS. We started to run the ECAM which had us turn off the green pump. Then I asked ATC to level off at 4000 ft. MSL and a heading while we ran a checklist. I turned the green pump back on to attempt to retract the landing gear; but after the system indicated no pressure; I turned the pump back off and left the gear down. We also checked the hydraulic page and noted that we had lost all fluid in the green system. At that time the Captain handed me the aircraft and radios while they worked in coordination with Dispatch and Maintenance Control. After conferring with Dispatch; I [requested priority handling] with ATC and notified them of our intention to return to ZZZ while the Captain continued to troubleshoot with Maintenance Control. I ran the HYD G Eng 1 Pump Lo Pr FM procedure; ran the landing distance tables; and built the box to an ILS to Runway YY; which was ZZZ's longest runway that supported the winds (250 @ 6 gusting 21). ATC began to give us vectors while I maintained an airspeed of 205 KIAS. Shortly thereafter the Captain got off the phone; informed me the flight controls would be slow to move; we had lost nose wheel steering; and thrust reversers on the left side; and would have to stop straight ahead on the runway.They talked to the passengers and Flight Attendants (FAs) to inform them of the situation; then asked me to run the overweight landing checklist; which I did. I also conferred with them on the L/G gravity extension checklist; which we did per the HYD G Eng 1 Lo Pr checklist. After that they reviewed the mission computer work I had done; looked at the approach; and briefed the procedures. I handed the aircraft back to them and I informed ATC we were ready for the approach and they set us up for a 25 mile straight in for the ILS to Runway YY. I ran the descent checklist; we configured the aircraft early due to slow flight control movement; and I ran the landing checklist. The Captain did a great; smooth landing on the runway and they brought us to a stop with the reversers in reverse idle. The Captain applied the brakes at 105 kts. and brought us to a stop abeam taxiway X. I asked Tower to have Crash Fire Rescue (CFR) check on the brakes to ensure they didn't overheat. I ran my normal after landing flow; we started the APU; the Captain talked to the passengers; and then we coordinated a tug with operations. We shut down the engines with the parking brake set and the Captain called the Chief Pilot to advise them of our situation and plan. The tug came and got us about 20 min later and pulled us back to the gate with no further issues. Upon arriving at the gate; the gate agent spoke to the passengers and deplaned the aircraft while we talked with maintenance.