#!/usr/bin/env python3
"""Troca os arquivos de ponteiro do Git LFS de uma arvore (as imagens .png do Clean Line, que o tarball do GitHub
traz como ponteiros de ~130 bytes) pelos objetos reais, pedidos pela API em lote do LFS do proprio repositorio do
autor. Cada objeto e conferido pelo sha256 do ponteiro (o oid do LFS e o sha256 do conteudo) e pelo tamanho.
Uso: lfs-fetch.py <repositorio owner/nome> <pasta> [<pasta> ...]"""
import hashlib, json, os, sys, urllib.request

repo, dirs = sys.argv[1], sys.argv[2:]
MAGIC = b"version https://git-lfs.github.com/spec/v1\n"
todo = {}
for d in dirs:
    for base, _, files in os.walk(d):
        for f in files:
            p = os.path.join(base, f)
            with open(p, "rb") as fh:
                head = fh.read(200)
            if head.startswith(MAGIC):
                lines = dict(l.split(" ", 1) for l in head.decode().strip().split("\n")[1:])
                todo.setdefault((lines["oid"].split(":", 1)[1].strip(), int(lines["size"])), []).append(p)
if not todo:
    print("nenhum ponteiro LFS")
    sys.exit(0)
req = urllib.request.Request(
    "https://github.com/%s.git/info/lfs/objects/batch" % repo,
    data=json.dumps({"operation": "download", "transfers": ["basic"],
                     "objects": [{"oid": o, "size": s} for (o, s) in todo]}).encode(),
    headers={"Accept": "application/vnd.git-lfs+json", "Content-Type": "application/vnd.git-lfs+json"})
res = json.load(urllib.request.urlopen(req, timeout=60))
for obj in res["objects"]:
    key = (obj["oid"], obj["size"])
    if "error" in obj:
        sys.exit("LFS: %s: %s" % (obj["oid"], obj["error"]))
    data = urllib.request.urlopen(obj["actions"]["download"]["href"], timeout=60).read()
    if hashlib.sha256(data).hexdigest() != obj["oid"] or len(data) != obj["size"]:
        sys.exit("LFS: conteudo de %s nao confere" % obj["oid"])
    for p in todo[key]:
        with open(p, "wb") as fh:
            fh.write(data)
print("objetos LFS baixados e conferidos:", len(todo), "em", sum(len(v) for v in todo.values()), "arquivos")