Adds get_paths_to_sync and organise it in a class

This refactors the paths functions in a class called PathsManager
allowing to share some data like the Paths to the various directories
unisync works with.
This commit also creates the get_paths_to_sync method which simply reads
the paths file and returns its content as a list

src/unisync/paths.py

@@ -3,42 +3,72 @@
 
 import subprocess
 
-def user_select_files(local_dir:str, choice_timeout:int=120) -> list[str]:
-    """
-    Make the user select files in the top directory.
-    Currently uses nnn for the selection.
-    The goal is to replace it in order to avoid using external programs.
-    Args:
-        local_dir: The absolute path to the top synchronisation directory
-        choice_timeout: Time given to make choices in nnn
-    Returns:
-        list[str]: The list of paths that was selected
-    """
-    command = [
-            "/usr/bin/nnn",
-            "-H",
-            "-p", "-",
-            local_dir
-            ]
-    nnn_process = subprocess.Popen(command, stdout=subprocess.PIPE)
-    try:
-        ret_code = nnn_process.wait(timeout=choice_timeout)
-    except subprocess.TimeoutExpired as e:
-        print("Choice timeout expired", file=sys.stderr)
-        raise e
+from pathlib import Path, PosixPath
 
-    if ret_code != 0:
-        print("File selection failed", file=sys.stderr)
-        raise subprocess.CalledProcessError("File selection failed")
+class PathsManager:
 
-    paths_list:list[str] = []
-    while (next_path := nnn_process.stdout.readline()) != b'':
-        next_path = next_path.decode().strip()
-        # Make the path relative to the top directory
-        next_path = next_path[len(local_dir):].lstrip("/")
-        paths_list.append(next_path)
+    def __init__(self, local_dir:PosixPath, cache_dir:PosixPath):
+        """
+        Creates a PathsManager with the necessary data
+        Args:
+            local_dir: Path to the top directory of the synchronisation
+            cache_dir: Path to the cache directory that contains the paths file
+        """
+        if not local_dir.is_dir():
+            raise ValueError("Invalid local directory")
+        self.local_dir = local_dir
 
-    return paths_list
+        if not cache_dir.is_dir():
+            raise ValueError("Invalid cache directory")
+        self.cache_dir = cache_dir
+
+        self.paths_file:PosixPath = self.cache_dir / "paths"
+        if not self.paths_file.is_file():
+            raise ValueError("The paths file does not exist")
 
 
+    def user_select_files(self, choice_timeout:int=120) -> list[str]:
+        """
+        Make the user select files in the top directory.
+        Currently uses nnn for the selection.
+        The goal is to replace it in order to avoid using external programs.
+        Args:
+            choice_timeout: Time given to make choices in nnn
+        Returns:
+            list[str]: The list of paths that was selected
+        """
+        command = [
+                "/usr/bin/nnn",
+                "-H",
+                "-p", "-",
+                self.local_dir
+                ]
+        nnn_process = subprocess.Popen(command, stdout=subprocess.PIPE)
+        try:
+            ret_code = nnn_process.wait(timeout=choice_timeout)
+        except subprocess.TimeoutExpired as e:
+            print("Choice timeout expired", file=sys.stderr)
+            raise e
+
+        if ret_code != 0:
+            print("File selection failed", file=sys.stderr)
+            raise subprocess.CalledProcessError("File selection failed")
+
+        paths_list:list[str] = []
+        while (next_path := nnn_process.stdout.readline()) != b'':
+            next_path = next_path.decode().strip()
+            # Make the path relative to the top directory
+            next_path = next_path[len(self.local_dir):].lstrip("/")
+            paths_list.append(next_path)
+        return paths_list
+
+    def get_paths_to_sync(self) -> list[str]:
+        """
+        Return the paths to synchronise as list.
+        """
+        paths:list[str] = self.paths_file.read_text().split("\n")
+        if paths[-1] == "":
+            paths.pop()
+        return paths
+