Add coerce.sh for character set coercion

For situations when there are constraints on what characters are
allowed, this module provides several non-reversible conversion
functions.

packaging/debian/control

@@ -172,6 +172,23 @@ Description: Shellfu/sh module for building interactive terminal menus
  This sub-package contains 'charmenu', a Shellfu/sh module for building
  interactive terminal menus
 
+Package: shellfu-sh-coerce
+Architecture: all
+Depends: shellfu-sh
+Description: Shellfu/sh module with data coercion helpers
+ Shellfu is an attempt to add modularity to your shell scripts.
+ .
+ With Shellfu you can develop your shell modules separately from your
+ scripts, and test, use, explore or study them without need to be aware
+ of details such as where the actual files are placed.
+ .
+ Shellfu is mostly intended for cases when there's need for non-trivial
+ amount of reliable body of shell scripts, and access to advanced modular
+ languages such as Python or Perl is limited.
+ .
+ This sub-package contains 'coerce', Shellfu module containing few
+ data coercion helpers.
+
 Package: shellfu-sh-exit
 Architecture: all
 Depends: shellfu-sh

packaging/template.spec

@@ -97,6 +97,13 @@ Obsoletes: shellfu-bash-extras < 0.10
 This sub-package contains 'charmenu', a Shellfu/sh module for building
 interactive terminal menus
 
+%package sh-coerce
+Summary: Shellfu/sh module with data coercion helpers
+Requires: shellfu-sh
+%description sh-isa
+This sub-package contains 'coerce', Shellfu module containing few
+data coercion helpers.
+
 %package sh-exit
 Summary: Shellfu/sh module for standard exit statuses
 Requires: shellfu-sh

src/include-sh/coerce.sh

@@ -0,0 +1,79 @@
+#!/bin/sh
+
+#
+# Data coercion helpers
+#
+# This module provides several simple functions to help transform
+# data to fit certain constraints.
+#
+
+#
+# Replacement character
+#
+COERCE__REPCHAR=${COERCE__REPCHAR:-�}
+
+coerce__nocolor() {
+    #
+    # Remove ANSI color codes
+    #
+    perl -CS -Mutf8 -MTerm::ANSIColor=colorstrip -ne 'print colorstrip $_;'
+}
+
+coerce__noctl() {
+    #
+    # Remove non-printable characters
+    #
+    perl -CS -Mutf8 -pe 'tr|[:graph:]\n\t ||c;'
+}
+
+coerce__nofdraw() {
+    #
+    # Replace frame-drawing characters with ASCII
+    #
+    # Replace frame-drawing characters according
+    # to following mapping:
+    #
+    #     ┌ ┬ ┐ └ ┴ ┘ ├ ┤ │ ┼ ─
+    #
+    #     ' ' ' . . . | | | | -
+    #
+    # This converts frame-drawing to ASCII, making it
+    # safer when fonts on terminals are not rendering
+    # properly.
+    #
+    perl -CS -Mutf8 -pe "
+        tr{┌┬┐}{.};
+        tr{└┴┘}{'};
+        tr{├┼┤│}{|};
+        tr{─}{-};
+    "
+}
+
+coerce__for_yaml() {
+    #
+    # Replace yaml-invalid characters
+    #
+    # Yaml won't allow all characters:
+    #
+    # > [...] The allowed character range explicitly excludes the C0 control
+    # > block #x0-#x1F (except for TAB #x9, LF #xA, and CR #xD which are
+    # > allowed), DEL #x7F, the C1 control block #x80-#x9F (except for NEL
+    # > #x85 which is allowed), the surrogate block #xD800-#xDFFF, #xFFFE,
+    # > and #xFFFF.
+    #
+    # so take stdin and replace all unacceptable characters with '�'.
+    #
+    perl -CS -Mutf8 -pe "tr/$(__coerce__for_yaml_bad)/$COERCE__REPCHAR/"
+}
+
+__coerce__for_yaml_bad() {
+    #
+    # Print all YAML-bad chars
+    #
+    printf '\N{U+0}-\N{U+8}\N{U+B}\N{U+C}\N{U+E}-\N{U+1F}'    # C0 with some gaps
+    printf '\N{U+7F}'                                         # DEL alone
+    printf '\N{U+80}-\N{U+84}\N{U+86}-\N{U+9F}'               # C1 with NEL gap
+    # printf -n '\N{U+D800}-\N{U+DFFF}'                        # surrogates
+    # printf -n '\N{U+FFFE}-\N{U+FFFF}'                        # 0xFFFE and 0xFFFF
+    #FIXME: for some reasons perl complains about these ^^
+}