From c7a28e464f3eddd21013b2f3c362ec3025e70822 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 23 Feb 2024 11:01:06 -0800
Subject: New cd alias feature.

* cdlog.sh (cdlog_alias): New global array.

* README.md: Documented.
(cdlog.chdir): Check for and expand alias.
(cdlog.alias): New function.
(cdalias): New alias.
---
 README.md | 15 +++++++++++++++
 cdlog.sh  | 35 +++++++++++++++++++++++++++++++++--
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 7c7bd3f..64214e2 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,8 @@ presents you with a numbered list of these sessions. You can recover to one of
 the sessions, use a `c` prefix on the number to clone the session into
 the current session, or press Enter to do nothing.
 
+* The `cdalias` command is used for defining "cd aliases"; see below.
+
 In addition, the `cdlog.sh` script sets the bash `direxpand` option.
 With the `direxpand` option, Tab completion on a directory coming
 from a variable name will expand that variable into the command line.
@@ -57,6 +59,19 @@ from a variable name will expand that variable into the command line.
 The directory changing commands do nothing if you attempt to change into the
 same directory you are already in. There is no effect on the FIFO.
 
+## Aliases
+
+`cdlog` provides its own "cd alias" feature. If the argument to
+`cd` contains no slashes, then it is used as a key to look up an
+alias, which replaces it. The replacement is not considered to
+be an alias even if it looks like one. Aliases are defined using
+the `cdalias` command which is an alias. It takes two arguments.
+
+Implementation notes: aliases are stored in the `cdlog_alias`
+array.  The `cdlog.chdir` function recognizes an alias only if
+it is invoked as `cdlog.chdir -p <alias>`, which is the way
+`cd` invokes it.
+
 ## Persistence
 
 Whenever the nine-element FIFO changes, the current directory and the
diff --git a/cdlog.sh b/cdlog.sh
index 017a9f0..e1a6181 100644
--- a/cdlog.sh
+++ b/cdlog.sh
@@ -1,7 +1,9 @@
 # License at bottom.
 
-# Configuration variables
+# Globals
+declare -A cdlog_alias            # cd aliases
 
+# Configuration variables
 cdlog_autocs=${cdlog_autocs-y}    # cd behaves like cs if match
 
 # Update after FIFO change.
@@ -146,7 +148,21 @@ cdlog.recover()
 cdlog.chdir()
 {
   local cur=$PWD
-  local i=10
+  local i
+  local def
+
+  if [ $# -eq 2 -a "$1" = -P ] ; then
+    case $2 in
+    ( */* )
+      ;;
+    ( * )
+      def=${cdlog_alias[$2]}
+      if [ -n "$def" ] ; then
+          set -- -P "$def"
+      fi
+      ;;
+    esac
+  fi
 
   if command cd "$@" && [ "$PWD" != "$cur" ]; then
     # only if we successfully change to a different
@@ -303,6 +319,20 @@ cdlog.mcd()
   return $res
 }
 
+cdlog.alias()
+{
+  local ali=
+  local def=
+
+  if [ $# -ne 2 ] ; then
+    printf "cdlog.alias: two arguments required\n"
+    return 1
+  fi
+
+  cdlog_alias[$1]=$2
+  return 0
+}
+
 # Aliases.
 alias cd='cdlog.chdir -P'
 alias pd='cdlog.pop'
@@ -312,6 +342,7 @@ alias cll='cdlog -l'
 alias mcd='cdlog.mcd'
 alias mcs='cdlog.mcd -s'
 alias cdr='cdlog.recover'
+alias cdalias='cdlog.alias'
 
 # Better completion for $x[Tab]
 shopt -s direxpand
-- 
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