add a completion function for zsh (#30)

README.md

@@ -97,7 +97,7 @@ you can do it with the `change-password` command.
 
 ### Changing the location of the credentials file
 
-Simply put this into your `.zshrc` (or `.{YourSell}rc` or `.profile`):
+Simply put this into your `.zshrc` (or `.{YourShell}rc` or `.profile`):
 
 ```
 export TOTP_CLI_CREDENTIAL_FILE="/mnt/mydrive/totp-credentials"
@@ -113,3 +113,19 @@ Note: It's a filename not just a directory.
 
 Note: It does not traverse through the given path,
       parent directory has to be there already.
+
+### Zsh Completion
+
+A function to provide tab-completion for zsh is in the file `_totp-cli`.
+When installing or packaging totp-cli this should preferably be
+installed in `$prefix/share/zsh/site-functions`. Otherwise, it can be
+installed by copying to a directory where zsh searches for completion
+functions (the `$fpath` array). If you, for example, put all completion
+functions into the folder `~/.zsh/completions` you must add the
+following to your zsh main config file (`.zshrc`):
+
+```
+fpath=( ~/.zsh/completions $fpath )
+autoload -U compinit
+compinit
+```

_totp-cli

@@ -0,0 +1,33 @@
+#compdef totp-cli
+
+# Completion function for zsh
+# Install this file in $prefix/share/zsh/site-functions or
+# update the fpath array in zsh to include its location
+
+local -a commands=(
+  'change-password:change password'
+  'delete:delete an account or a whole namespace'
+  'generate:generate a specific OTP'
+  'instant:generate an OTP from TOTP_TOKEN without the Storage backend'
+  'list:list all available namespaces or accounts under a namespace'
+  'update:check and update totp-cli itself'
+  'version:display version information'
+  'add-token:add new token'
+  'help:display general or command-specific usage information'
+)
+
+case $CURRENT:${words[2]} in
+  2:*|3:help)
+    _describe -t commands command commands
+  ;;
+  3:(add-token|delete|generate|list))
+    _message -e namespaces namespace
+  ;;
+  4:(add-token|delete|generate|list))
+    _message -e accounts account
+  ;;
+  *)
+    _message 'no more arguments'
+  ;;
+esac
+