add basic variable parsing

2 files changed, 38 insertions, 14 deletions

diff --git a/src/parse/ast.rs b/src/parse/ast.rs
index 28593bb..71cb9af 100644
--- a/src/parse/ast.rs
+++ b/src/parse/ast.rs
@@ -142,6 +142,7 @@ struct Word {
     word: String,
     interpolate: bool,
     quoted: bool,
+    var: bool,
 }
 
 impl Word {
@@ -150,22 +151,33 @@ impl Word {
             matches!(rule, Rule::bareword | Rule::double_string);
         let quoted =
             matches!(rule, Rule::single_string | Rule::double_string);
-        let mut word_str = s.to_string();
-        if interpolate {
-            word_str = strip_escape(&word_str);
+        let var = matches!(rule, Rule::var);
+        let word_str = if var {
+            let inner = s.strip_prefix('$').unwrap();
+            inner
+                .strip_prefix('{')
+                .map_or(inner, |inner| inner.strip_suffix('}').unwrap())
+                .to_string()
+        } else if interpolate {
+            strip_escape(s)
         } else {
-            word_str = strip_basic_escape(&word_str);
-        }
+            strip_basic_escape(s)
+        };
         Self {
             word: word_str,
             interpolate,
             quoted,
+            var,
         }
     }
 
     fn eval(self, _env: &Env) -> String {
-        // TODO
-        self.word
+        if self.var {
+            // TODO
+            format!("'value-of-${{{}}}'", self.word)
+        } else {
+            self.word
+        }
     }
 }
 
@@ -247,7 +259,10 @@ impl WordOrRedirect {
         }
         assert!(matches!(
             word.as_rule(),
-            Rule::bareword | Rule::single_string | Rule::double_string
+            Rule::var
+                | Rule::bareword
+                | Rule::single_string
+                | Rule::double_string
         ));
         let word = Word::parse(word.as_str(), word.as_rule());
         if let Some(prefix) = prefix {
@@ -381,6 +396,7 @@ macro_rules! w {
             word: $word.to_string(),
             interpolate: true,
             quoted: false,
+            var: false,
         }
     };
     ($word:expr, $interpolate:expr) => {
@@ -388,6 +404,7 @@ macro_rules! w {
             word: $word.to_string(),
             interpolate: $interpolate,
             quoted: false,
+            var: false,
         }
     };
     ($word:expr, $interpolate:expr, $quoted:expr) => {
@@ -395,6 +412,7 @@ macro_rules! w {
             word: $word.to_string(),
             interpolate: $interpolate,
             quoted: $quoted,
+            var: false,
         }
     };
 }
diff --git a/src/shell.pest b/src/shell.pest
index ffb0f42..b1bcae5 100644
--- a/src/shell.pest
+++ b/src/shell.pest
@@ -3,11 +3,17 @@ escape_char       = @{ "\\" ~ ANY }
 
 bareword_char = @{
     escape_char |
-    !("|" | ";" | "\"" | "'" | WHITESPACE | COMMENT) ~ ANY
+    !("|" | ";" | "\"" | "'" | "$" | WHITESPACE | COMMENT) ~ ANY
 }
 single_string_char = @{ basic_escape_char | (!"'" ~ ANY) }
 double_string_char = @{ escape_char | (!"\"" ~ ANY) }
 
+var = @{
+    ("$" ~ XID_START ~ XID_CONTINUE*) |
+    ("$" ~ ("?" | "$" | "*" | ASCII_DIGIT)) |
+    ("${" ~ (!"}" ~ ANY)+ ~ "}")
+}
+
 redir_prefix  = @{ ASCII_DIGIT* ~ (">>" | ">" | "<") ~ WHITESPACE* }
 bareword      = @{ bareword_char+ }
 single_string = @{ single_string_char+ }
@@ -15,17 +21,17 @@ double_string = @{ double_string_char+ }
 
 word     = ${
     redir_prefix? ~
-    (bareword |
+    (var | bareword |
     "'" ~ single_string ~ "'" |
     "\"" ~ double_string ~ "\"")
 }
 
 exe      = ${ word ~ (w ~ word)* }
-pipeline = ${ exe ~ (w ~ "|" ~ w ~ exe)* }
-commands = ${ pipeline ~ (w ~ ";" ~ w ~ pipeline)* }
+pipeline = ${ exe ~ (w? ~ "|" ~ w? ~ exe)* }
+commands = ${ pipeline ~ (w? ~ ";" ~ w? ~ pipeline)* }
 
-line = ${ SOI ~ w ~ commands ~ w ~ EOI }
+line = ${ SOI ~ w? ~ commands ~ w? ~ EOI }
 
-w          = _{ (WHITESPACE | COMMENT)* }
+w          = _{ (WHITESPACE | COMMENT)+ }
 WHITESPACE = _{ (" " | "\t" | "\n") }
 COMMENT    = _{ "#" ~ ANY* }