start introducing modules

zfs_backup/commands.py

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+from __future__ import annotations
+
+from pathlib import Path
+from subprocess import Popen, call, check_output, PIPE
+
+from misc import assert_type
+
+
+class CommandInterface:
+    _BINARY: Path
+
+    @classmethod
+    def _run_command(cls, *args: str) -> None:
+        CommandRunner.run([str(cls._BINARY), *args])
+
+    @classmethod
+    def _get_output(cls, *args: str) -> str:
+        return CommandRunner.get_output([str(cls._BINARY), *args])
+
+    @classmethod
+    def _open_stream(cls, *args: str) -> Popen:
+        return CommandRunner.send_stream([str(cls._BINARY), *args])
+
+    @classmethod
+    def _receive_stream(cls, *args: str, stream: Popen) -> None:
+        CommandRunner.receive_from_stream([str(cls._BINARY), *args], stream=stream)
+
+
+class CommandRunner:
+    @staticmethod
+    def _sanity_check(cmdline: list[str]) -> None:
+        assert_type(cmdline, list, "Command line must be a list")
+        for item in cmdline:
+            assert_type(item, str, "Only strings allowed in command line")
+
+    @staticmethod
+    def _to_list(command: str | list[str]) -> list[str]:
+        """If the command is a str, return it as list. Otherwise, return the command."""
+        if isinstance(command, str):
+            return [command]
+        return command
+
+    @classmethod
+    def run(cls, cmdline: str | list[str]) -> None:
+        """Run the command, wait for it to return."""
+        cmdline = cls._to_list(cmdline)
+        cls._sanity_check(cmdline)
+        call(cmdline)
+
+    @classmethod
+    def get_output(cls, cmdline: str | list[str]) -> str:
+        """Run the command, return the output of the command."""
+        cmdline = cls._to_list(cmdline)
+        cls._sanity_check(cmdline)
+        return check_output(cmdline).strip().decode()
+
+    @classmethod
+    def receive_from_stream(cls, cmdline: str | list[str], stream: Popen) -> None:
+        """Run the command, receive data from a pipe to stdin."""
+        cmdline = cls._to_list(cmdline)
+        cls._sanity_check(cmdline)
+        check_output(cmdline, stdin=stream.stdout)
+
+    @classmethod
+    def send_stream(cls, cmdline: str | list[str]) -> Popen:
+        """Run the command, redirect stdout to a pipe."""
+        cmdline = cls._to_list(cmdline)
+        cls._sanity_check(cmdline)
+        return Popen(cmdline, stdout=PIPE)