begin of a parser

1 files changed, 84 insertions, 0 deletions

diff --git a/src/parse.rs b/src/parse.rs
new file mode 100644
index 0000000..cc495b1
--- /dev/null
+++ b/src/parse.rs
@@ -0,0 +1,84 @@
+pub enum Ast {
+    AssignVar(AssignVar),
+    Pipes(Pipes),
+}
+
+pub struct AssignVar {
+    pub to: String,
+    // TODO: body
+}
+
+pub struct Pipes {
+    pub cmds: Vec<Command>,
+}
+
+pub struct Command {
+    pub path: String,
+    pub args: Vec<String>,
+}
+
+enum ParseError {
+    Incomplete,
+    UnexpectedPipe,
+    UnknownChar(char),
+}
+
+type Result<T> = std::result::Result<T, ParseError>;
+
+pub fn parse(x: &str) -> Result<Ast> {
+    let chars: Vec<char> = x.chars().collect();
+    Ast::parse(&mut &chars[..])
+}
+
+trait Parse: Sized {
+    fn parse(b: &mut &[char]) -> Result<Self>;
+}
+
+fn spaces(b: &mut &[char]) {
+    while let Some(' ' | '\t') = b.get(0) {
+        *b = &b[1..];
+    }
+}
+
+fn parse_quoted_string(b: &mut &[char], delim: char) -> Result<String> {
+    // TODO: escape sequence stuff
+
+    *b = &b[1..];
+    let mut s = String::new();
+    while b.len() > 0 {
+        if b[0] == delim {
+            *b = &b[1..];
+            return Ok(s);
+        }
+
+        s.push(b[0]);
+        *b = &b[1..];
+    }
+    Err(ParseError::Incomplete)
+}
+
+impl Parse for String {
+    fn parse(b: &mut &[char]) -> Result<Self> {
+        spaces(b);
+        if b.is_empty() {
+            return Err(ParseError::Incomplete);
+        }
+        let c = b[0];
+        if c == '|' {
+            Err(ParseError::UnexpectedPipe)
+        } else if c == '\'' || c == '"' {
+            *b = &b[1..];
+            parse_quoted_string(b, c)
+        } else if c.is_ascii_graphic() {
+            parse_quoted_string(b, ' ')
+        } else {
+            Err(ParseError::UnknownChar(c))
+        }
+    }
+}
+
+impl Parse for Ast {
+    fn parse(b: &mut &[char]) -> Result<Self> {
+        todo!()
+    }
+}