The claim of a temple below the Shahi Jama Masjid in Badaun, what is the whole truth?

It is being claimed that there is Neelkanth Mahadev Temple below the Shamsi Shahi Jama Masjid of Badaun. The Hindu side, citing the survey and gazetteer of the Archaeological Department, said that the mosque was built on the site of an ancient temple. The Muslim side says that Altamash had built the mosque in 1223 AD. After the Sambhal violence, this issue has again come into limelight. There has also been a debate on the Places of Worship Act.