from pathlib import Path, PurePath

import hashlib
import os

from collections import namedtuple

GIT_DIR = ".ugit"


def init():
    Path.mkdir(GIT_DIR)
    Path.mkdir(f"{GIT_DIR}/objects")


RefValue = namedtuple("RefValue", ["symbolic", "value"])


def update_ref(ref, value):
    assert not value.symbolic
    ref_path = f"{GIT_DIR}/{ref}"
    Path.mkdir(ref_path, exist_ok=True)
    with open(ref_path, "w") as f:
        f.write(value.value)


def get_ref(ref):
    ref_path = f"{GIT_DIR}/{ref}"
    value = None
    if Path.is_file(ref_path):
        with open(ref_path) as f:
            value = f.read().strip()

    if value and value.startswith("ref:"):
        return get_ref(value.split(":", 1)[1].strip())

    return RefValue(symbolic=False, value=value)


def iter_refs():
    refs = ["HEAD"]
    for root, _, filenames in Path.walk(f"{GIT_DIR}/refs"):
        root = PurePath.relative_to(root, GIT_DIR)
        refs.extend(f"{root}/{name}" for name in filenames)

    for refname in refs:
        yield refname, get_ref(refname)


def hash_object(data, type_="blob"):
    obj = type_.encode() + b"\x00" + data
    oid = hashlib.sha1(obj).hexdigest()
    with open(f"{GIT_DIR}/objects/{oid}", "wb") as out:
        out.write(obj)
    return oid


def get_object(oid, expected="blob"):
    with open(f"{GIT_DIR}/objects/{oid}", "rb") as f:
        obj = f.read()

    type_, _, content = obj.partition(b"\x00")
    type_ = type_.decode()

    if expected is not None:
        assert type_ == expected, f"Expected {expected}, got {type_}"
    return content