John is my friend. I'm in his house right now (we've been talking for about 20 minutes). My other friend calls me and asks me: "Where are you?" I say: "I'm in John's house at the moment." Then he says: "Why are you there?" I reply to him with one of the sentences below.
I hadn't seen him for a long time, so I decided to pay him a visit. That's why I'm here in his house.
I haven't seen him for a long time, so I have decided to pay him a visit. That's why I'm here in his house.
Which of the above sentences should be used in the context given? I'm wondering about the tenses in bold.