From 9faa39b400a155c9dddeea4fe712301462093d4f Mon Sep 17 00:00:00 2001
From: Helmut Grohne <helmut@subdivi.de>
Date: Tue, 11 May 2021 14:52:29 +0200
Subject: add ssh remote backend and streamapi wrapper

The ssh backend calls into another host and passes all information on
stdin/stdout/stderr. To do so, it uses a streamapi wrapper on the remote
side that itself calls into a regular backend.
---
 mdbp/streamapi.py | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 mdbp/streamapi.py

(limited to 'mdbp/streamapi.py')

diff --git a/mdbp/streamapi.py b/mdbp/streamapi.py
new file mode 100644
index 0000000..8f67366
--- /dev/null
+++ b/mdbp/streamapi.py
@@ -0,0 +1,73 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: MIT
+"""mdbp frontend without filesystem interaction. It basically wraps another
+backend and is used as frontend from the ssh backend on the remote side.
+Differences to the regular backend API:
+ * It expects an uncompressed tar file on stdin. The first member must be named
+   "build.json". Any other members must be regular files. The build.json file
+   should lack the .output.directory and if an .input.dscpath is given, it
+   should not contain any slashes.
+ * The build log is issued on stderr instead of stdout.
+ * All the requested artifacts are emitted as a tar stream on stdout.
+"""
+
+import argparse
+import json
+import pathlib
+import subprocess
+import sys
+import tarfile
+import tempfile
+
+from .common import json_load, buildjson_validate, buildjson_patch_relative, \
+        tar_add
+
+def main() -> None:
+    """Entry point for mdbp-streamapi wrapper"""
+    parser = argparse.ArgumentParser()
+    parser.add_argument("command", nargs=argparse.REMAINDER)
+    args = parser.parse_args()
+    if not args.command:
+        parser.error("missing command")
+
+    with tempfile.TemporaryDirectory() as tdirname:
+        indir = pathlib.Path(tdirname) / "input"
+        outdir = pathlib.Path(tdirname) / "output"
+        indir.mkdir()
+        outdir.mkdir()
+        with tarfile.open(fileobj=sys.stdin.buffer, mode="r|") as intar:
+            seenjson = False
+            for member in intar:
+                if "/" in member.name or not member.isfile():
+                    raise ValueError("expected flat tar as input")
+                if seenjson:
+                    intar.extract(member, indir, set_attrs=False)
+                    continue
+                if member.name != "build.json":
+                    raise ValueError("first input member must be build.json")
+                jsonfileobj = intar.extractfile(member)
+                # We already checked .isfile(), but mypy doesn't know.
+                assert jsonfileobj is not None
+                build = json_load(jsonfileobj)
+                build["output"]["directory"] = str(outdir)
+                buildjson_validate(build)
+                buildjson_patch_relative(build, indir)
+                (indir / "build.json").write_text(json.dumps(build))
+                seenjson = True
+            if not seenjson:
+                raise ValueError("input is an empty tar archive")
+        proc = subprocess.Popen([*args.command, str(indir / "build.json")],
+                                stdout=sys.stderr
+                                       if build["output"].get("log", True)
+                                       else subprocess.DEVNULL,
+                                stderr=None if build["output"].get("log", True)
+                                       else subprocess.DEVNULL)
+        code = proc.wait()
+        if code != 0:
+            sys.exit(code)
+        with tarfile.open(fileobj=sys.stdout.buffer, mode="w|") as outtar:
+            for elem in outdir.iterdir():
+                tar_add(outtar, elem)
+
+if __name__ == "__main__":
+    main()
-- 
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