From 1c1542d64f37c67bf29c3de1e06735fd79cc50ea Mon Sep 17 00:00:00 2001
From: Pierre Le Marre <dev@wismill.eu>
Date: Fri, 29 Sep 2023 20:44:06 +0200
Subject: [PATCH] Tools: Add bash completions for xkbcli

- Add bash completion script. It parses the commands help messages to
  provide the completions, thus any new subcommand or option will be
  supported, as long as it has its entry in the help messages. This
  should result in low maintenancei effort.
- Add installation entry in Meson. The path can be configured using
  the following options:
  - `enable-bash-completion` to enable the installation;
  - `bash-completion-path` to control the installation path. It will
    default to: `share/bash-completion/completions`.

TODO: completion for other shells, such as zsh?
---
 meson.build                     | 30 +++++++++++
 meson_options.txt               | 11 ++++
 tools/compile-keymap.c          |  2 +
 tools/xkbcli-bash-completion.sh | 96 +++++++++++++++++++++++++++++++++
 tools/xkbcli.c                  |  3 ++
 5 files changed, 142 insertions(+)
 create mode 100755 tools/xkbcli-bash-completion.sh

diff --git a/meson.build b/meson.build
index 91d0b36..7d5802b 100644
--- a/meson.build
+++ b/meson.build
@@ -417,6 +417,7 @@ man_pages = []
 # Tools
 build_tools = get_option('enable-tools') and cc.has_header_symbol('getopt.h', 'getopt_long', prefix: '#define _GNU_SOURCE')
 if build_tools
+    # Common resources
     libxkbcommon_tools_internal_sources = [
         'tools/tools-common.h',
         'tools/tools-common.c',
@@ -432,10 +433,27 @@ if build_tools
         dependencies: dep_libxkbcommon,
     )
 
+    # Tool: xkbcli
     executable('xkbcli', 'tools/xkbcli.c',
                dependencies: tools_dep, install: true)
     install_man('tools/xkbcli.1')
 
+    if get_option('enable-bash-completion')
+        bash_completion_path = get_option('bash-completion-path')
+        if bash_completion_path == ''
+            bash_completion = dependency('bash-completion', required: false)
+            if bash_completion.found()
+                bash_completion_path = bash_completion.get_variable(pkgconfig: 'completionsdir')
+            else
+                bash_completion_path = get_option('datadir') / 'bash-completion/completions'
+            endif
+        endif
+        install_data('tools/xkbcli-bash-completion.sh',
+                     rename: 'xkbcli',
+                     install_dir: bash_completion_path)
+    endif
+
+    # Tool: compile-keymap
     xkbcli_compile_keymap = executable('xkbcli-compile-keymap',
                                        'tools/compile-keymap.c',
                                        dependencies: tools_dep,
@@ -450,12 +468,16 @@ if build_tools
                c_args: ['-DENABLE_PRIVATE_APIS'],
                include_directories: [include_directories('src', 'include')],
                install: false)
+
+    # Tool: compose
     executable('compose',
                'tools/compose.c',
                dependencies: tools_dep,
                include_directories: [include_directories('src', 'include')],
                install: false)
     configh_data.set10('HAVE_XKBCLI_COMPILE_KEYMAP', true)
+
+    # Tool: how-to-type
     executable('xkbcli-how-to-type',
                'tools/how-to-type.c',
                dependencies: tools_dep,
@@ -463,6 +485,8 @@ if build_tools
                install_dir: dir_libexec)
     install_man('tools/xkbcli-how-to-type.1')
     configh_data.set10('HAVE_XKBCLI_HOW_TO_TYPE', true)
+
+    # Tool: interactive-evdev
     if cc.has_header('linux/input.h')
         executable('xkbcli-interactive-evdev',
                    'tools/interactive-evdev.c',
@@ -481,6 +505,8 @@ if build_tools
                 include_directories: [include_directories('src', 'include')],
                 install: false)
     endif
+
+    # Tool: interactive-x11
     if get_option('enable-x11')
         x11_tools_dep = declare_dependency(
             link_with: libxkbcommon_x11,
@@ -498,6 +524,8 @@ if build_tools
         install_man('tools/xkbcli-interactive-x11.1')
         configh_data.set10('HAVE_XKBCLI_INTERACTIVE_X11', true)
     endif
+
+    # Tool: interactive-wayland
     if get_option('enable-wayland')
         wayland_client_dep = dependency('wayland-client', version: '>=1.2.0', required: false)
         wayland_protocols_dep = dependency('wayland-protocols', version: '>=1.12', required: false)
@@ -534,6 +562,7 @@ You can disable the Wayland xkbcli programs with -Denable-wayland=false.''')
         configh_data.set10('HAVE_XKBCLI_INTERACTIVE_WAYLAND', true)
     endif
 
+    # Tool: list
     if get_option('enable-xkbregistry')
         configh_data.set10('HAVE_XKBCLI_LIST', true)
         executable('xkbcli-list',
@@ -544,6 +573,7 @@ You can disable the Wayland xkbcli programs with -Denable-wayland=false.''')
         install_man('tools/xkbcli-list.1')
     endif
 
+    # Tool: check-messages
     executable('xkb-check-messages',
                'tools/check-messages.c',
                'tools/messages.c',
diff --git a/meson_options.txt b/meson_options.txt
index 924d1f7..d52cc37 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -13,6 +13,11 @@ option(
     type: 'string',
     description: 'The X locale root [default=$datadir/X11/locale]',
 )
+option(
+    'bash-completion-path',
+    type: 'string',
+    description: 'Directory for bash completion scripts'
+)
 option(
     'default-rules',
     type: 'string',
@@ -79,3 +84,9 @@ option(
     value: true,
     description: 'Enable building libxkbregistry',
 )
+option(
+    'enable-bash-completion',
+    type: 'boolean',
+    value: true,
+    description: 'Enable installing bash completion scripts',
+)
diff --git a/tools/compile-keymap.c b/tools/compile-keymap.c
index d762624..f49aa3c 100644
--- a/tools/compile-keymap.c
+++ b/tools/compile-keymap.c
@@ -58,6 +58,8 @@ usage(char **argv)
            "Compile the given RMLVO to a keymap and print it\n"
            "\n"
            "Options:\n"
+           " --help\n"
+           "    Print this help and exit\n"
            " --verbose\n"
            "    Enable verbose debugging output\n"
 #if ENABLE_PRIVATE_APIS
diff --git a/tools/xkbcli-bash-completion.sh b/tools/xkbcli-bash-completion.sh
new file mode 100755
index 0000000..fdab116
--- /dev/null
+++ b/tools/xkbcli-bash-completion.sh
@@ -0,0 +1,96 @@
+# bash completion support for xkbcli.
+
+# See completion API documentation: https://github.com/scop/bash-completion
+# NOTE: The script parses the commands help messages to provide the completions,
+#       thus any new subcommand or option will be supported, as long as it has its
+#       entry in the help messages. This should result in low maintenancei effort.
+
+___xkbcli_main()
+{
+    # Initialization: https://github.com/scop/bash-completion/blob/fdf4456186eb4548ef628e65fb1be73d8e4695e9/bash_completion.d/000_bash_completion_compat.bash#L205
+    local cur prev words cword cmd
+    _init_completion -s || return
+
+    # Find subcommand
+    local i=1
+    while [[ "$i" -lt "$COMP_CWORD" ]]; do
+        local s="${COMP_WORDS[i]}"
+        case "$s" in
+            -*) ;;
+            *)
+            cmd="$s"
+            break
+            ;;
+        esac
+        (( i++ ))
+    done
+
+    # Parse available subcommands
+    local line
+    local is_command_list=false
+    local subcommands=()
+    while IFS='' read -r line; do
+        # Traverse subcommand list
+        if [[ "$is_command_list" == true ]]; then
+            # Check for subcommand based on the indentation
+            if [[ "$line" =~ ^[[:blank:]]{2}([[:alpha:]]([[:alnum:]]|-)+)$ ]]; then
+                subcommands+=("${BASH_REMATCH[1]}")
+            # Detect end of subcommand list based on indentation
+            elif [[ "$line" =~ ^[[:graph:]] ]]; then
+                is_command_list=false
+            fi
+        # Detect start of subcommand list
+        elif [[ "$line" == "Commands:" ]]; then
+            is_command_list=true
+        fi
+    # NOTE: <( COMMAND ) Bash construct is “process substitution”.
+    done < <(xkbcli --help)
+
+    # No previous subcommand or incomplete: completion for root xkbcli command
+    if [[ "$i" -eq "$COMP_CWORD" ]]; then
+        local opts
+        # Doc for _parse_help: https://github.com/scop/bash-completion/blob/fdf4456186eb4548ef628e65fb1be73d8e4695e9/bash_completion.d/000_bash_completion_compat.bash#L311
+        opts=$(_parse_help xkbcli)
+        local cur="${COMP_WORDS[COMP_CWORD]}"
+        COMPREPLY=($(compgen -W "${subcommands[*]} $opts" -- "$cur"))
+        return
+    fi
+
+    # Found a supported subcommand: proceed to completion
+    if [[ "${subcommands[*]}" =~ (^| )$cmd( |$) ]]; then
+        ___xkbcli_subcommand "$cmd"
+    fi
+}
+
+___xkbcli_subcommand()
+{
+    # Some special cases
+    case $1 in
+        compile-keymap | interactive-evdev)
+            case ${COMP_WORDS[COMP_CWORD-1]} in
+                --include | --keymap)
+                    _filedir
+                    return;;
+            esac
+            ;;
+        list)
+            if [[ ${COMP_WORDS[COMP_CWORD]} != -* ]]; then
+                _filedir
+                return
+            fi
+            ;;
+    esac
+
+    # Parse help to get command options
+    local opts
+    # Doc for _parse_usage and _parse_help:
+    # • https://github.com/scop/bash-completion/blob/fdf4456186eb4548ef628e65fb1be73d8e4695e9/bash_completion.d/000_bash_completion_compat.bash#L335
+    # • https://github.com/scop/bash-completion/blob/fdf4456186eb4548ef628e65fb1be73d8e4695e9/bash_completion.d/000_bash_completion_compat.bash#L311
+    # We need both as the current help messages adopt both GNU and BSD styles.
+    opts=$(_parse_usage xkbcli "$1 --help")
+    opts+=$(_parse_help xkbcli "$1 --help")
+    local cur="${COMP_WORDS[COMP_CWORD]}"
+    COMPREPLY=($(compgen -W "$opts" -- "$cur"))
+}
+
+complete -F ___xkbcli_main xkbcli
diff --git a/tools/xkbcli.c b/tools/xkbcli.c
index 75f72fe..3602fb9 100644
--- a/tools/xkbcli.c
+++ b/tools/xkbcli.c
@@ -37,6 +37,9 @@ usage(void)
            "Global options:\n"
            "  -h, --help ...... show this help and exit\n"
            "  -V, --version ... show version information and exit\n"
+           /* WARNING: The following is parsed by the bash completion script.
+            *          Any change to the format (in particular to the indentation)
+            *          should kept in the script in sync. */
            "Commands:\n"
 #if HAVE_XKBCLI_LIST
            "  list\n"