I don't think there is a difference. Both mean the same thing.

i did this means its completed in past i have done this means just now it completed means just few seconds

There is no difference in meaning and in nuance.

The meaning is VERY different! Let me put more context in the sentence to make the meaning clearer: I wish my wife did/would do the dishes. I have to do them every night. I wish I had done the dishes. Now I have to do them. Can you see the difference? If not, here is the rule: I wish + past simple (or would + be) = present regrets I wish + past perfect = past regrets Sentence #1 refers to my wife's habit of never cleaning. You can use past simple or would + infinitive for "action verbs", but remember the golden rule: never use "would" with a feeling/state verb (for example "I wish I was/were a bird", "I wish I had $1 million". But NEVER say: *"I wish I would be a bird", *"I wish I would have $1 million") In #2 I am talking about the past. My wife didn't do the dishes, and now I am sad. Here are some more examples: "I wish I had left home earlier this morning, now I'm late for work"; "I wish I had studied harder for the exams, now I have failed all my studies." می فهمید؟ ;-)