Added transaction.py

Allow for transactions to be created, controlling and managing operation
goals.

enum@PkgGoal:
	- An enumaration of all possible package goals which a transaction
	  can perform.

class@Transaction:
	- Create a new transaction for the given context of a comment
	  (specified by the `goal=`).
	- method@compute:
		- Compute all the system dependencies and return them as a
		  tuple. Note, dependencies that soypak can install will not be
		  listed here and included in the final state.
	- method@apply:
		- Will apply the goal to the transaction and handle the
		  appropriate operations call.
	- method@problems:
		- Report a tuple of packages which were identified as
		  problematic during the transaction goal.
	- method@commit:
		- Commit the transaction to record to inform what exactly
		  happened during that transaction, i.e., the goal.
	-method@finalised:
		- Return a list of the final state, i.e., those packages related
		  to the transaction goal.

soypak/deps/transaction.py

@@ -0,0 +1,53 @@
+import enum
+import sys
+import clog
+import soypak.deps.bottler as bottler
+import soypak.deps.operations as ops
+
+
+_log = clog.Logger.get("runtime_logger")
+
+
+class PkgGoal(enum.Enum):
+    PKG_INSTALL = 1
+
+
+class Transaction:
+    def __init__(self, goal: PkgGoal) -> None:
+        """Setup a new transaction."""
+        if not isinstance(goal, PkgGoal):
+            _log.error(f"TypeError: {goal=}, expected PkgGoal.")
+            _log.printLog("There was an issue when operating on the transaction.", level=4)
+            sys.exit(1)
+        self.pkg_goal: PkgGoal = goal
+
+
+    def compute(self, pkgs: list[bottler._Soybottle]) -> tuple:
+        """Compute dependencies and conflicts of packages. Returns a list of total packages to install."""
+        self._final_state = []
+        sys_depends = []
+        for pkg in pkgs:
+            ...
+            # :@TODO: compute the dependencies
+
+        return tuple(sys_depends)
+
+
+    def apply(self):
+        if self.pkg_goal == PkgGoal.PKG_INSTALL:
+            ops.install_packages(self._final_state)
+
+
+    def problems(self) -> tuple:
+        """Provide a report of conflicts and packages which cannot be resolved (dependencies not installable)."""
+        return ()
+
+
+    def commit(self):
+        """Commit the transaction to record for what happened."""
+        pass
+
+
+    @property
+    def finalised(self):
+        return self._final_state