From 25ab623328e63edabe6af54d7416e6d317988c1a Mon Sep 17 00:00:00 2001
From: "D. Berge" <dberge@aaltronav.eu>
Date: Wed, 30 Aug 2023 14:17:47 +0200
Subject: [PATCH] Add functions for translating paths.

The Dougal database will no longer store physical file paths
but rather logical ones, relative to (config.yaml).imports.paths.

These functions translate between physical and logical paths.
---
 bin/configuration.py | 71 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/bin/configuration.py b/bin/configuration.py
index 17cf0f7..d59d0ee 100644
--- a/bin/configuration.py
+++ b/bin/configuration.py
@@ -1,4 +1,5 @@
 import os
+import pathlib
 from glob import glob
 from yaml import full_load as _load
 
@@ -87,3 +88,73 @@ def rxflags (flagstr):
 	for flag in flagstr:
 		flags |= cases.get(flag, 0)
 	return flags
+
+def translate_path (file):
+	"""
+	Translate a path from a Dougal import directory to an actual
+	physical path on disk.
+
+	Any user files accessible by Dougal must be under a path prefixed
+	by `(config.yaml).imports.paths`. The value of `imports.paths` may
+	be either a string, in which case this represents the prefix under
+	which all Dougal data resides, or a dictionary where the keys are
+	logical paths and their values the corresponding physical path.
+	"""
+	cfg = read()
+	root = pathlib.Path(DOUGAL_ROOT)
+	filepath = pathlib.Path(file).resolve()
+	import_paths = cfg["imports"]["paths"]
+
+	if filepath.is_absolute():
+		if type(import_paths) == str:
+			# Substitute the root for the real physical path
+			# NOTE: `root` deals with import_paths not being absolute
+			prefix = root.joinpath(pathlib.Path(import_paths)).resolve()
+			return str(pathlib.Path(prefix).joinpath(*filepath.parts[2:]))
+		else:
+			# Look for a match on the second path element
+			if filepath.parts[1] in import_paths:
+				# NOTE: `root` deals with import_paths[…] not being absolute
+				prefix = root.joinpath(import_paths[filepath.parts[1]])
+				return str(pathlib.Path(prefix).joinpath(*filepath.parts[2:]))
+			else:
+				# This path is invalid
+				raise TypeError("invalid path or file: {0!r}".format(filepath))
+	else:
+		# A relative filepath is always resolved relative to the logical root
+		root = pathlib.Path("/")
+		return translate_path(root.joinpath(filepath))
+
+def untranslate_path (file):
+	"""
+	Attempt to convert a physical path into a logical one.
+	See `translate_path()` above for details.
+	"""
+	cfg = read()
+	dougal_root = pathlib.Path(DOUGAL_ROOT)
+	filepath = pathlib.Path(file).resolve()
+	import_paths = cfg["imports"]["paths"]
+	physical_root = pathlib.Path("/")
+
+	if filepath.is_absolute():
+		if type(import_paths) == str:
+			if filepath.is_relative_to(import_paths):
+				physical_root = pathlib.Path("/")
+				physical_prefix = pathlib.Path(import_paths)
+				return str(root.joinpath(filepath.relative_to(physical_prefix)))
+			else:
+				raise TypeError("invalid path or file: {0!r}".format(filepath))
+		else:
+			for key, value in import_paths.items():
+				value = dougal_root.joinpath(value)
+				physical_prefix = pathlib.Path(value)
+				if filepath.is_relative_to(physical_prefix):
+					logical_prefix = physical_root.joinpath(pathlib.Path(key)).resolve()
+					return str(logical_prefix.joinpath(filepath.relative_to(physical_prefix)))
+
+			# If we got here with no matches, this is not a valid
+			# Dougal data path
+			raise TypeError("invalid path or file: {0!r}".format(filepath))
+	else:
+		# A relative filepath is always resolved relative to DOUGAL_ROOT
+		return untranslate_path(root.joinpath(filepath))