brn: Introduce BRN as a class

app/brm/__init__.py

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+"""
+Bypass Censorship Resource Management API.
+"""

app/brm/brn.py

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+"""
+Bypass Censorship Resource Names.
+"""
+
+from __future__ import annotations
+from dataclasses import dataclass, field
+from typing import Any
+
+from flask import current_app
+
+from app.brm.utils import is_integer
+
+
+def global_namespace() -> str:
+    return str(current_app.config["GLOBAL_NAMESPACE"])
+
+
+@dataclass
+class BRN:
+    group_id: int
+    product: str
+    provider: str
+    resource_type: str
+    resource_id: str
+    global_namespace: str = field(default_factory=global_namespace)
+
+    @classmethod
+    def from_str(cls, s: str) -> BRN:
+        parts = s.split(":")
+        if len(parts) != 6 or parts[0].lower() != "brn" or not is_integer(parts[2]):
+            raise TypeError(f"Expected a valid BRN but got {repr(s)}.")
+        resource_parts = parts[4].split("/")
+        if len(resource_parts) != 5:
+            raise TypeError(f"Expected a valid BRN but got {repr(s)}.")
+        return cls(
+            global_namespace=parts[1],
+            group_id=int(parts[2]),
+            product=parts[3],
+            provider=parts[4],
+            resource_type=resource_parts[0],
+            resource_id=resource_parts[1]
+        )
+
+    def __eq__(self, other: Any) -> bool:
+        return str(self) == str(other)
+
+    def __str__(self) -> str:
+        return ":".join([
+            "brn",
+            self.global_namespace,
+            str(self.group_id),
+            self.product,
+            self.provider,
+            f"{self.resource_type}/{self.resource_id}"
+        ])
+
+    def __repr__(self) -> str:
+        return f"<BRN {str(self)}>"

app/brm/utils.py

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+from __future__ import annotations
+
+from typing import Any
+
+
+def is_integer(n: Any) -> bool:
+    """
+    Determine if a string (or other object type that can be converted automatically) represents an integer.
+
+    Thanks to https://note.nkmk.me/en/python-check-int-float/.
+
+    :param n: object to test
+    :return: true if it's an integer
+    """
+    try:
+        float(n)
+    except ValueError:
+        return False
+    else:
+        return float(n).is_integer()