#!/usr/bin/env python3

# Copyright 2021 Codethink Limited

# raw file archive using git-lfs frontend for git-fast-import

import hashlib
import os
import shutil
import subprocess
import sys
import time

branch_name = "master"
branch_ref = "refs/heads/%s" % branch_name
committer_name = "Lorry Raw File Importer"
committer_email = "lorry-raw-file-importer@lorry"


def commit_lfs_gitattributes(fast_import):
    commit_time = int(time.time())
    commit = (
        "commit {ref}\n"
        "committer {committer_name} <{committer_email}> {commit_time} +0000\n"
        "data <<EOM\n"
        "Ensure LFS is configured\n"
        "EOM\n"
        "M 100644 inline .gitattributes\n"
        "data <<EOM\n"
        "* filter=lfs diff=lfs merge=lfs -text\n"
        ".gitattributes filter diff merge text=auto\n"
        "EOM\n"
        "\n"
    ).format(
        ref=branch_ref,
        committer_name=committer_name,
        committer_email=committer_email,
        commit_time=commit_time,
    )
    fast_import.write(commit.encode("utf-8"))


def commit_lfs_file(raw_file, relative_path, last_commit, fast_import):
    # git-lfs-pointer of the file
    ret = subprocess.run(
        ["git", "lfs", "pointer", "--file", raw_file],
        stdout=subprocess.PIPE,
        check=True,
    )
    pointer_digest = ret.stdout
    datasize = len(pointer_digest)

    # sha256sum of the file
    # slightly wasteful because git-lfs-pointer also generates a sha256sum
    with open(raw_file, "rb") as f:
        shasum = hashlib.sha256(f.read()).hexdigest()

    # Add the file to the repo
    out_dir = os.path.join("lfs", "objects", shasum[0:2], shasum[2:4])
    os.makedirs(out_dir, exist_ok=True)
    shutil.copyfile(raw_file, os.path.join(out_dir, shasum))

    # Commit the data to master
    commit_time = int(time.time())
    basename = os.path.basename(raw_file)
    # Ensure we don't allow directory traversal
    path = os.path.relpath(os.path.join(relative_path, basename))
    if path[0:3] == "../":
        print("error: unsafe path: {}".format(path), file=sys.stderr)
        sys.exit(1)

    fromline = "from {}\n".format(last_commit) if last_commit else ""

    commit = (
        "commit {ref}\n"
        "committer {committer_name} <{committer_email}> {commit_time} +0000\n"
        "data <<EOM\n"
        "import {basename}\n"
        "EOM\n"
        "{fromline}"
        "M 100644 inline {path}\n"
        "data {datasize}\n"
        "{data}\n"
        "\n"
    ).format(
        ref=branch_ref,
        committer_name=committer_name,
        committer_email=committer_email,
        commit_time=commit_time,
        basename=basename,
        fromline=fromline,
        path=path,
        datasize=datasize,
        data=pointer_digest.decode("utf-8"),
    )
    fast_import.write(commit.encode("utf-8"))


def get_last_commit():
    # show the full hash of the latest commit
    out = subprocess.run(
        ["git", "rev-parse", branch_ref],
        stdout=subprocess.PIPE,
        universal_newlines=True,
    )
    if out.returncode != 0:
        return None

    # Will be same string as input when no commits exist yet
    out = out.stdout.strip()
    return None if out == branch_ref else out


def main():
    if len(sys.argv) != 3:
        print("usage:", sys.argv[0], "<file>", "<relative path>")
        sys.exit(1)

    raw_file = sys.argv[1]
    relpath = sys.argv[2]

    last_commit = get_last_commit()
    with subprocess.Popen(
        "git fast-import --quiet", shell=True, stdin=subprocess.PIPE
    ) as import_proc:
        if not last_commit:
            commit_lfs_gitattributes(import_proc.stdin)

        commit_lfs_file(raw_file, relpath, last_commit, import_proc.stdin)
        import_proc.stdin.close()
        if import_proc.wait() != 0:
            sys.exit(1)


main()