From cffa56ed750ee1e7ca634e316464b0f07f23dce8 Mon Sep 17 00:00:00 2001
From: Shrikant Sharat <shrikantsharat.k@gmail.com>
Date: Sat, 11 Aug 2012 14:10:33 +0530
Subject: [PATCH] Added function to handle argument parsing.

---
 antigen.zsh        | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/arg-parser.t |  48 +++++++++++++++++++++++
 2 files changed, 160 insertions(+)
 create mode 100644 tests/arg-parser.t

diff --git a/antigen.zsh b/antigen.zsh
index 30ff392..bef9542 100644
--- a/antigen.zsh
+++ b/antigen.zsh
@@ -364,6 +364,118 @@ antigen () {
     "antigen-$cmd" "$@"
 }
 
+-antigen-parse-args () {
+    # An argument parsing functionality to parse arguments the *antigen* way :).
+    # Takes one first argument (called spec), which dictates how to parse and
+    # the rest of the arguments are parsed. Outputs a piece of valid shell code
+    # that can be passed to `eval` inside a function which creates the arguments
+    # and their values as local variables. Suggested use is to set the defaults
+    # to all arguments first and then eval the output of this function.
+
+    # Spec: Only long argument supported. No support for parsing short options.
+    # The spec must have two sections, separated by a `;`.
+    #       '<positional-arguments>;<keyword-only-arguments>'
+    # Positional arguments are passed as just values, like `command a b`.
+    # Keyword arguments are passed as a `--name=value` pair, like `command
+    # --arg1=a --arg2=b`.
+
+    # Each argument in the spec is separated by a `,`. Each keyword argument can
+    # end in a `:` to specifiy that this argument wants a value, otherwise it
+    # doesn't take a value. (The value in the output when the keyword argument
+    # doesn't have a `:` is `true`).
+
+    # Arguments in either section can end with a `?` (should come after `:`, if
+    # both are present), means optional. FIXME: Not yet implemented.
+
+    # See the test file, tests/arg-parser.t for (working) examples.
+
+    local spec="$1"
+    shift
+
+    local code=''
+
+    --add-var () {
+        test -z "$code" || code="$code\n"
+        code="${code}local $1='$2'"
+    }
+
+    local positional_args="$(echo "$spec" | cut -d\; -f1)"
+    local positional_args_count="$(echo $positional_args |
+            awk -F, '{print NF}')"
+
+    # Set spec values based on the positional arguments.
+    local i=1
+    while ! [[ -z $1 || $1 == --* ]]; do
+
+        if (( $i > $positional_args_count )); then
+            echo "Only $positional_args_count positional arguments allowed." >&2
+            echo "Found at least one more: '$1'" >&2
+            return
+        fi
+
+        local name_spec="$(echo "$positional_args" | cut -d, -f$i)"
+        local name="${${name_spec%\?}%:}"
+        local value="$1"
+
+        --add-var $name "$value"
+
+        shift
+        i=$(($i + 1))
+    done
+
+    local keyword_args="$(echo "$spec" | cut -d\; -f2 | tr , '\n')"
+    local keyword_args_count="$(echo $keyword_args | awk -F, '{print NF}')"
+
+    # Set spec values from keyword arguments, if any. The remaining arguments
+    # are all assumed to be keyword arguments.
+    while [[ $1 == --* ]]; do
+        # Remove the `--` at the start.
+        local arg="${1#--}"
+
+        # Get the argument name and value.
+        if [[ $arg != *=* ]]; then
+            local name="$arg"
+            local value=''
+        else
+            local name="${arg%\=*}"
+            local value="${arg#*=}"
+        fi
+
+        # The specification for this argument, used for validations.
+        local arg_line="$(echo "$keyword_args" | grep -m1 "^$name:\??\?")"
+
+        # Validate argument and value.
+        if [[ -z $arg_line ]]; then
+            # This argument is not known to us.
+            echo "Unknown argument '$name'." >&2
+            return
+
+        elif (echo "$arg_line" | grep -qm1 ':') && [[ -z $value ]]; then
+            # This argument needs a value, but is not provided.
+            echo "Required argument for '$name' not provided." >&2
+            return
+
+        elif (echo "$arg_line" | grep -vqm1 ':') && [[ ! -z $value ]]; then
+            # This argument doesn't need a value, but is provided.
+            echo "No argument required for '$name', but provided '$value'." >&2
+            return
+
+        fi
+
+        if [[ -z $value ]]; then
+            value=true
+        fi
+
+        --add-var "${name//-/_}" "$value"
+        shift
+    done
+
+    echo "$code"
+
+    unfunction -- --add-var
+
+}
+
 # Echo the bundle specs as in the record. The first line is not echoed since it
 # is a blank line.
 -antigen-echo-record () {
diff --git a/tests/arg-parser.t b/tests/arg-parser.t
new file mode 100644
index 0000000..ac7cda8
--- /dev/null
+++ b/tests/arg-parser.t
@@ -0,0 +1,48 @@
+Helper alias.
+
+  $ alias parse='-antigen-parse-args "url?,loc?;btype:?,no-local-clone?"'
+
+No arguments (since all are specified as optional).
+
+  $ parse
+   (glob)
+
+One positional argument.
+
+  $ parse name
+  local url='name'
+
+Two arguments.
+
+  $ parse url location
+  local url='url'
+  local loc='location'
+
+Three arguments.
+
+  $ parse url location crap
+  Only 2 positional arguments allowed.
+  Found at least one more: 'crap'
+
+Keywordo magic.
+
+  $ parse url location --btype=1 --no-local-clone
+  local url='url'
+  local loc='location'
+  local btype='1'
+  local no_local_clone='true'
+
+Unknown keyword argument.
+
+  $ parse --me=genius
+  Unknown argument 'me'.
+
+Missed value for keyword argument.
+
+  $ parse --btype
+  Required argument for 'btype' not provided.
+
+Provide value for keyword argument, that shouldn't be there.
+
+  $ parse --no-local-clone=yes
+  No argument required for 'no-local-clone', but provided 'yes'.
-- 
2.0.0