Git Rebase — ধারণা ও ইন্টারঅ্যাক্টিভ রিবেস

# git rebase সিমুলেশন -- L30/L34-এর ঠিক একই Repo মডেল ব্যবহার করে।
# বাস্তব git বাইনারি এই স্যান্ডবক্সে নেই, তাই এটি git-এর নিজস্ব রিবেস অ্যালগরিদমের
# (merge base খোঁজা -> commit replay করা -> branch pointer সরানো) একটি from-scratch, নির্ভুল সিমুলেশন।

def make_repo():
    return {
        "working_directory": {},
        "staging_area": {},
        "commits": {},
        "branches": {"main": None},
        "head": "main",
    }

def _new_hash(repo):
    return f"c{len(repo['commits']) + 1}"

def current_commit(repo):
    if repo["head"] in repo["branches"]:
        return repo["branches"][repo["head"]]
    return repo["head"]

def git_add(repo, filename):
    repo["staging_area"][filename] = repo["working_directory"][filename]

def git_commit(repo, message):
    parent = current_commit(repo)
    commit_hash = _new_hash(repo)
    repo["commits"][commit_hash] = {
        "message": message,
        "snapshot": dict(repo["staging_area"]),
        "parent": parent,
    }
    if repo["head"] in repo["branches"]:
        repo["branches"][repo["head"]] = commit_hash
    else:
        repo["head"] = commit_hash
    repo["staging_area"] = {}
    return commit_hash

def git_branch(repo, name):
    repo["branches"][name] = current_commit(repo)

def git_switch(repo, name):
    repo["head"] = name

def find_merge_base(repo, tip_a, tip_b):
    ancestors_a = set()
    current = tip_a
    while current is not None:
        ancestors_a.add(current)
        current = repo["commits"][current]["parent"]
    current = tip_b
    while current is not None:
        if current in ancestors_a:
            return current
        current = repo["commits"][current]["parent"]
    return None

def git_rebase(repo, branch, onto_branch):
    branch_tip = repo["branches"][branch]
    onto_tip = repo["branches"][onto_branch]
    base = find_merge_base(repo, branch_tip, onto_tip)

    # branch-এর নিজস্ব commit গুলো (base-এর পর থেকে), পুরনো -> নতুন ক্রমে
    unique = []
    current = branch_tip
    while current != base:
        unique.append(current)
        current = repo["commits"][current]["parent"]
    unique.reverse()

    hash_map = {}
    new_parent = onto_tip
    for old_hash in unique:
        old = repo["commits"][old_hash]
        new_hash = _new_hash(repo)
        repo["commits"][new_hash] = {
            "message": old["message"],
            "snapshot": dict(old["snapshot"]),
            "parent": new_parent,
        }
        hash_map[old_hash] = new_hash
        new_parent = new_hash

    repo["branches"][branch] = new_parent
    return hash_map


repo = make_repo()

repo["working_directory"]["app.py"] = "print('v1')"
git_add(repo, "app.py")
git_commit(repo, "প্রজেক্ট শুরু")

git_branch(repo, "feature-x")
git_switch(repo, "feature-x")

repo["working_directory"]["login.py"] = "def login(): pass"
git_add(repo, "login.py")
git_commit(repo, "লগইন ফাংশন যোগ")

repo["working_directory"]["login.py"] = "def login(): return True"
git_add(repo, "login.py")
git_commit(repo, "লগইন রিটার্ন ভ্যালু ঠিক করা")

git_switch(repo, "main")
repo["working_directory"]["readme.md"] = "# Project"
git_add(repo, "readme.md")
git_commit(repo, "README যোগ করা হলো")

print("Rebase-এর আগে:")
print("  main       ->", repo["branches"]["main"])
print("  feature-x  ->", repo["branches"]["feature-x"])

hash_map = git_rebase(repo, "feature-x", "main")

print("\nRebase-এর পরে:")
print("  main       ->", repo["branches"]["main"])
print("  feature-x  ->", repo["branches"]["feature-x"])

print("\nমূল commit হ্যাশ  ->  নতুন replay করা commit হ্যাশ  (মেসেজ অপরিবর্তিত থাকছে):")
for old_hash, new_hash in hash_map.items():
    msg = repo["commits"][new_hash]["message"]
    print(f"  {old_hash}  ->  {new_hash}   \"{msg}\"")

hashes_differ = all(old != new for old, new in hash_map.items())
print("\nসব রিপ্লে করা commit-এর হ্যাশ মূল হ্যাশ থেকে ভিন্ন?", hashes_differ)


def interactive_rebase_squash(commits_list, squash_indices):
    squash_set = set(squash_indices)
    if not squash_set:
        return list(commits_list)

    start = min(squash_set)
    end = max(squash_set)
    kept_before = commits_list[:start]
    kept_after = commits_list[end + 1:]
    to_squash = commits_list[start:end + 1]

    combined_message = "; ".join(c["message"] for c in to_squash)
    combined_snapshot = {}
    for c in to_squash:
        combined_snapshot.update(c["snapshot"])  # পরের commit-এর কনটেন্ট শেষ অবস্থাকে override করে

    squashed_commit = {"message": combined_message, "snapshot": combined_snapshot}
    return kept_before + [squashed_commit] + kept_after


messy_history = [
    {"message": "WIP: ফিচার শুরু করা হলো", "snapshot": {"cart.py": "v1"}},
    {"message": "WIP: টেস্ট ঠিক করা হলো", "snapshot": {"cart.py": "v2"}},
    {"message": "WIP: টাইপো ফিক্স", "snapshot": {"cart.py": "v3", "cart_test.py": "v1"}},
]

print("\n\nSquash-এর আগে: মোট", len(messy_history), "টি commit")
for c in messy_history:
    print("  -", c["message"])

cleaned_history = interactive_rebase_squash(messy_history, [0, 1, 2])

print("\nSquash-এর পরে: মোট", len(cleaned_history), "টি commit")
for c in cleaned_history:
    print("  -", c["message"])
    print("    ফাইল অবস্থা:", c["snapshot"])