2 files changed, 101 insertions, 23 deletions

diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 1827122..ffbdfe5 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -47,6 +47,7 @@ pub trait Expander {
 #[derive(Debug, Clone, PartialEq)]
 pub struct Block {
     pub commands: Vec<Ast<PreExpansion>>,
+    pub finished_parsing: bool,
 }
 
 #[derive(Debug, Clone, PartialEq)]
@@ -84,7 +85,6 @@ pub enum Ast<T: Stage> {
     While(While),
 }
 
-#[allow(unused)]
 #[derive(Debug, Clone, PartialEq)]
 enum IfParseProgress {
     Condition,
@@ -93,6 +93,12 @@ enum IfParseProgress {
     Done,
 }
 
+impl IfParseProgress {
+    pub fn is_done(&self) -> bool {
+        matches!(self, Self::Done)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub struct If<T: Stage> {
     pub condition: Pipes<T>,
@@ -206,6 +212,7 @@ pub fn cmd<const N: usize>(x: [ExpString; N]) -> Command<PreExpansion> {
 pub fn block<const N: usize>(x: [Ast<PreExpansion>; N]) -> Block {
     Block {
         commands: x.to_vec(),
+        finished_parsing: true,
     }
 }
 
@@ -420,16 +427,22 @@ impl Parse for Block {
             commands.push(cmd);
         }
 
-        if b.has() {
+        let finished_parsing = if b.has() {
             if b.peek() != b'}' {
                 return Err(ParseError::Expected('}'));
             }
             b.adv();
+            true
         } else if !b.is_completion() {
             return Err(ParseError::Expected('}'));
-        }
+        } else {
+            false
+        };
 
-        Ok(Self { commands })
+        Ok(Self {
+            commands,
+            finished_parsing,
+        })
     }
 }
 
@@ -1128,6 +1141,8 @@ pub enum ParseError {
     NotAnIf,
 
     NotAWhile,
+
+    ExpectedKeyword(Keyword),
 }
 
 type Result<T> = std::result::Result<T, ParseError>;
@@ -1177,6 +1192,7 @@ impl Block {
     fn empty() -> Self {
         Self {
             commands: Vec::with_capacity(0),
+            finished_parsing: true,
         }
     }
 }
@@ -1395,42 +1411,104 @@ impl<'a> Cursor<'a> {
     fn parse<T: Parse>(&mut self) -> Result<T> {
         T::parse(self)
     }
+
+    fn consume_keyword(&mut self, kw: Keyword) -> Result<()> {
+        self.spaces();
+        let bytes = kw.as_bytes();
+        if self.buf.starts_with(bytes) {
+            if kw.requires_space() && self.buf.len() > bytes.len() {
+                if self.buf[bytes.len()].is_ascii_whitespace() {
+                    self.buf = &self.buf[bytes.len() + 1..];
+                    self.spaces();
+                    Ok(())
+                } else {
+                    self.buf = &self.buf[bytes.len()..];
+                    self.spaces();
+                    Err(ParseError::ExpectedKeyword(kw))
+                }
+            } else {
+                Ok(())
+            }
+        } else {
+            Err(ParseError::ExpectedKeyword(kw))
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum Keyword {
+    If,
+    While,
+    Else,
+    Elif,
+}
+
+impl Keyword {
+    fn as_bytes(&self) -> &bstr {
+        match self {
+            Keyword::If => b"if",
+            Keyword::While => b"while",
+            Keyword::Elif => b"elif",
+            Keyword::Else => b"else",
+        }
+    }
+
+    fn requires_space(&self) -> bool {
+        match self {
+            Keyword::If => true,
+            Keyword::While => true,
+            Keyword::Elif => true,
+            Keyword::Else => false,
+        }
+    }
 }
 
 impl Parse for If<PreExpansion> {
     fn parse(b: &mut Cursor<'_>) -> Result<Self> {
+        b.consume_keyword(Keyword::If)?;
+
+        let mut res = If {
+            condition: Pipes::parse(b)?,
+            true_block: Block::empty(),
+            false_block: Block::empty(),
+            parse_progress: IfParseProgress::Condition,
+        };
+
         b.spaces();
-        if !b.buf.starts_with(b"if ") || b.buf.starts_with(b"if\t") {
-            return Err(ParseError::NotAnIf);
+        if b.is_completion() && b.is_empty() {
+            return Ok(res);
+        }
+
+        res.true_block = Block::parse(b)?;
+        if res.true_block.finished_parsing {
+            res.parse_progress = IfParseProgress::Done;
+        } else {
+            res.parse_progress = IfParseProgress::TrueBlock;
         }
-        b.advance(3);
-        b.spaces();
-        let condition = Pipes::parse(b)?;
-        let true_block = Block::parse(b)?;
 
         b.spaces();
+        if b.is_completion() && b.is_empty() {
+            return Ok(res);
+        }
 
-        let false_block = if b.buf.starts_with(b"else") {
-            b.advance(4);
+        res.false_block = if b.consume_keyword(Keyword::Else).is_ok() {
             Block::parse(b)?
-        } else if b.buf.starts_with(b"elif") {
-            b.advance(2);
+        } else if b.consume_keyword(Keyword::Elif).is_ok() {
             let elif = If::parse(b)?;
             Block {
+                finished_parsing: elif.parse_progress.is_done(),
                 commands: vec![Ast::If(elif)],
             }
         } else {
             Block::empty()
         };
+        if res.false_block.finished_parsing {
+            res.parse_progress = IfParseProgress::Done;
+        } else {
+            res.parse_progress = IfParseProgress::FalseBlock;
+        }
 
-        Ok(If {
-            condition,
-            true_block,
-            false_block,
-
-            // TODO: for completion one should allow more lenient parsing and set this appropriately then
-            parse_progress: IfParseProgress::Done,
-        })
+        Ok(res)
     }
 }
 
diff --git a/src/run/mod.rs b/src/run/mod.rs
index 52d3925..f34b678 100644
--- a/src/run/mod.rs
+++ b/src/run/mod.rs
@@ -451,7 +451,7 @@ impl Executor {
         stdin: InputReader,
         stdout: OutputWriter,
     ) -> SpawnedCmd {
-        self.execute_block(parse::Block { commands: s.stmts }, stdin, stdout)
+        self.execute_block(parse::Block { commands: s.stmts, finished_parsing: true }, stdin, stdout)
     }
 }