from contextlib import contextmanager
import os

from .common import WorkspaceError, read_json, safe_path, write_json


class State:
    def __init__(self, root):
        self.root = root
        self.area = safe_path(root, ".workspace")
        self.path = safe_path(root, ".workspace/state.json")
        self.data = read_json(self.path) if self.path.exists() else {"schema": 1, "components": {}}
        if not isinstance(self.data, dict) or self.data.get("schema") != 1 or not isinstance(self.data.get("components"), dict):
            raise WorkspaceError("unsupported workspace state")
        for name, entry in self.data["components"].items():
            if not isinstance(entry, dict) or entry.get("owner_root") != str(root):
                raise WorkspaceError(f"workspace owner mismatch: {name}")
            safe_path(root, entry.get("path", ""))

    def save(self):
        write_json(self.path, self.data)

    @contextmanager
    def operation(self):
        self.area.mkdir(exist_ok=True)
        path = safe_path(self.root, ".workspace/.operation.lock")
        try:
            descriptor = os.open(path, os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0o600)
        except FileExistsError as error:
            raise WorkspaceError("workspace has another writer (.operation.lock); preserve the owner lock") from error
        try:
            with os.fdopen(descriptor, "w") as stream:
                stream.write(str(os.getpid()) + "\n")
            yield
        finally:
            path.unlink()