🙃

backend/src/cell.rs

@@ -0,0 +1,99 @@
+use std::collections::HashSet;
+
+use crate::evaluator::*;
+
+#[derive(Clone)]
+pub struct Cell {
+    eval: Eval,
+    raw: String,
+    i_dep: HashSet<CellRef>,
+    they_dep: HashSet<CellRef>,
+}
+
+impl Cell {
+    pub fn new(eval: Eval, raw: String) -> Self {
+        Self {
+            eval,
+            raw,
+            i_dep: HashSet::new(),
+            they_dep: HashSet::new(),
+        }
+    }
+
+    pub fn raw(&self) -> String {
+        self.raw.clone()
+    }
+
+    pub fn eval(&self) -> Eval {
+        self.eval.clone()
+    }
+
+    pub fn add_i_dep(&mut self, dep: CellRef) {
+        self.i_dep.insert(dep);
+    }
+
+    pub fn add_they_dep(&mut self, dep: CellRef) {
+        self.they_dep.insert(dep);
+    }
+
+    pub fn clear_i_dep(&mut self) {
+        self.i_dep.clear();
+    }
+
+    pub fn clear_they_dep(&mut self) {
+        self.they_dep.clear();
+    }
+
+    pub fn set_eval(&mut self, eval: Eval) {
+        self.eval = eval;
+    }
+}
+
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+pub struct CellRef {
+    pub row: i64,
+    pub col: i64,
+}
+
+impl CellRef {
+    pub fn new(s: String) -> Result<CellRef, String> {
+        let s = s.trim();
+        let mut col: i64 = 0;
+        let mut i = 0;
+
+        // consume leading letters for the column
+        for (idx, ch) in s.char_indices() {
+            if ch.is_ascii_alphabetic() {
+                let u = ch.to_ascii_uppercase() as u8;
+                let val = (u - b'A' + 1) as i64; // A->1 ... Z->26
+                col = col * 26 + val;
+                i = idx + ch.len_utf8();
+            } else {
+                break;
+            }
+        }
+
+        if col <= 0 {
+            return Err(format!(
+                "Parse error: missing column letters in cell ref: {s}"
+            ));
+        }
+
+        let row_part = &s[i..];
+        if row_part.is_empty() {
+            return Err(format!(
+                "Parse error: missing column letters in cell ref: {s}"
+            ));
+        } else if !row_part.chars().all(|c| c.is_ascii_digit()) {
+            return Err(format!(
+                "Parse error: row part must be numeric in cell ref: {s}"
+            ));
+        }
+
+        if let Ok(row) = row_part.parse::<i64>() {
+            Ok(CellRef { row, col })
+        } else {
+            Err(format!("Parse error: invalid row number."))
+        }
+    }
+}

backend/src/evaluator.rs

@@ -0,0 +1,168 @@
+use crate::cell::{Cell, CellRef};
+use crate::parser::*;
+use crate::tokenizer::Literal;
+use std::collections::HashMap;
+use std::fmt;
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Eval {
+    Literal(Literal),
+}
+
+impl fmt::Display for Eval {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Eval::Literal(lit) => write!(f, "{lit:?}"),
+        }
+    }
+}
+
+pub struct Evaluator {
+    cells: HashMap<CellRef, Cell>,
+}
+
+impl Evaluator {
+    pub fn new() -> Evaluator {
+        return Evaluator {
+            cells: HashMap::new(),
+        };
+    }
+
+    pub fn set_cell(&mut self, cell_ref: CellRef, raw_val: String) -> Result<(), String> {
+        if self.cells.contains_key(&cell_ref) && self.cells[&cell_ref].raw() == raw_val {
+            return Ok(());
+        }
+
+        let eval: Eval;
+
+        if let Some(c) = raw_val.chars().nth(0)
+            && c == '='
+        {
+            eval = self.evaluate(raw_val[1..].to_owned())?;
+        } else {
+            match self.evaluate(raw_val.to_owned()) {
+                Ok(e) => {
+                    eval = e;
+                }
+                Err(_) => eval = Eval::Literal(Literal::String(raw_val.to_owned())),
+            }
+        }
+
+        self.cells.insert(cell_ref, Cell::new(eval, raw_val));
+        Ok(())
+    }
+
+    pub fn get_cell(&mut self, cell_ref: CellRef) -> Result<(String, Eval), String> {
+        if !self.cells.contains_key(&cell_ref) {
+            return Err(format!("Cell at {:?} not found.", cell_ref));
+        }
+
+        let cell = &self.cells[&cell_ref];
+
+        Ok((cell.raw(), cell.eval()))
+    }
+
+    pub fn evaluate(&mut self, str: String) -> Result<Eval, String> {
+        let (mut expr, mut deps) = parse(&str)?;
+
+        self.evaluate_expr(&mut expr)
+    }
+
+    fn evaluate_expr(&mut self, expr: &mut Expr) -> Result<Eval, String> {
+        let res = match expr {
+            Expr::Literal(lit) => Eval::Literal(lit.clone()),
+            Expr::CellRef(re) => self.get_cell(re.to_owned())?.1,
+            Expr::Infix { op, lhs, rhs } => {
+                let lval = self.evaluate_expr(lhs)?;
+                let rval = self.evaluate_expr(rhs)?;
+
+                match op {
+                    InfixOp::ADD => eval_add(&lval, &rval)?,
+                    InfixOp::SUB => eval_sub(&lval, &rval)?,
+                    InfixOp::MUL => eval_mul(&lval, &rval)?,
+                    InfixOp::DIV => eval_div(&lval, &rval)?,
+                    _ => return Err(format!("Evaluation error: Unsupported operator {:?}", op)),
+                }
+            }
+            it => return Err(format!("Evaluation error: Unsupported expression {:?}", it)),
+        };
+
+        Ok(res)
+    }
+}
+
+fn eval_add(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
+    match (lval, rval) {
+        (Eval::Literal(a), Eval::Literal(b)) => {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x + y, |x, y| x + y) {
+                return Ok(Eval::Literal(res));
+            }
+
+            // Try string concatenation
+            if let (Literal::String(x), Literal::String(y)) = (a, b) {
+                let mut res = x.to_owned();
+                res.push_str(y);
+                return Ok(Eval::Literal(Literal::String(res)));
+            }
+
+            Err("Evaluation error: expected string or numeric types for ADD function.".to_string())
+        }
+    }
+}
+
+fn eval_sub(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
+    match (lval, rval) {
+        (Eval::Literal(a), Eval::Literal(b)) => {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x - y, |x, y| x - y) {
+                return Ok(Eval::Literal(res));
+            }
+
+            Err("Evaluation error: expected string or numeric types for SUB function.".to_string())
+        }
+    }
+}
+fn eval_mul(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
+    match (lval, rval) {
+        (Eval::Literal(a), Eval::Literal(b)) => {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x * y, |x, y| x * y) {
+                return Ok(Eval::Literal(res));
+            }
+
+            Err("Evaluation error: expected string or numeric types for MUL function.".to_string())
+        }
+    }
+}
+fn eval_div(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
+    match (lval, rval) {
+        (Eval::Literal(a), Eval::Literal(b)) => {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x / y, |x, y| x / y) {
+                return Ok(Eval::Literal(res));
+            }
+
+            Err("Evaluation error: expected string or numeric types for DIV function.".to_string())
+        }
+    }
+}
+
+fn eval_numeric_infix<FInt, FDouble>(
+    lhs: &Literal,
+    rhs: &Literal,
+    int_op: FInt,
+    double_op: FDouble,
+) -> Option<Literal>
+where
+    FInt: Fn(i64, i64) -> i64,
+    FDouble: Fn(f64, f64) -> f64,
+{
+    match (lhs, rhs) {
+        (Literal::Integer(a), Literal::Integer(b)) => Some(Literal::Integer(int_op(*a, *b))),
+        (Literal::Double(a), Literal::Double(b)) => Some(Literal::Double(double_op(*a, *b))),
+        (Literal::Integer(a), Literal::Double(b)) => {
+            Some(Literal::Double(double_op(*a as f64, *b)))
+        }
+        (Literal::Double(a), Literal::Integer(b)) => {
+            Some(Literal::Double(double_op(*a, *b as f64)))
+        }
+        _ => None,
+    }
+}

backend/src/main.rs

@@ -0,0 +1,69 @@
+mod cell;
+mod evaluator;
+mod parser;
+mod tokenizer;
+
+use std::io;
+
+use websocket::server::WsServer;
+
+use crate::{cell::CellRef, evaluator::Evaluator};
+
+fn main() {
+    // let mut input = String::new();
+    // io::stdin().read_line(&mut input).expect("Expected input.");
+
+    // let mut ast = parser::parse(&input).unwrap();
+    // println!("{}", ast.pretty());
+    let mut evaluator = Evaluator::new();
+    // // println!("{}", evaluator.evaluate(input).unwrap());
+    // let a1 = CellRef { row: 1, col: 2 };
+    // evaluator.set_cell(a1, input).unwrap();
+    // println!("{:?}", evaluator.get_cell(a1).unwrap());
+
+    println!("CMDS : set <cell_ref>, get <cell_ref>");
+    loop {
+        let mut input = String::new();
+        io::stdin().read_line(&mut input).expect("Expected input.");
+
+        let cmds = ["set", "get"];
+        let cmd = &input[0..3];
+        if !cmds.iter().any(|c| c == &cmd) {
+            println!("{} is an invalid command!", cmd);
+            println!("CMDS : set <cell_ref>, get <cell_ref>");
+            continue;
+        }
+
+        let rest = &input[4..];
+        let mut parts = rest.splitn(2, char::is_whitespace);
+
+        let raw_ref = parts.next().unwrap_or("").trim(); // cell reference
+        let raw_str = parts.next().unwrap_or("").trim(); // rest of the string (value)
+        // println!("{} {}", raw_ref, raw_str);
+
+        if let Ok(cell_ref) = CellRef::new(raw_ref.to_owned()) {
+            match cmd {
+                "set" => match evaluator.set_cell(cell_ref, raw_str.to_owned()) {
+                    Ok(_) => println!("Successfully set cell {} to {}.", raw_ref, raw_str),
+                    Err(e) => println!("{}", e),
+                },
+                "get" => match evaluator.get_cell(cell_ref) {
+                    Ok(res) => println!("{:?}", res),
+                    Err(e) => println!("{}", e),
+                },
+                _ => {
+                    panic!("Impossible.");
+                }
+            }
+        } else {
+            println!("{} is an invalid cell reference!", raw_ref);
+            continue;
+        }
+    }
+
+    let rt = Runtime::new().unwrap();
+    let handle = rt.handle().clone();
+    let addr = "127.0.0.1:7050";
+
+    let socket = WsServer::bind(addr, handle);
+}

backend/src/parser.rs

@@ -0,0 +1,291 @@
+use crate::{cell::CellRef, tokenizer::*};
+use std::{collections::HashSet, fmt};
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum PrefixOp {
+    POS,
+    NEG,
+    NOT,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum PostfixOp {
+    PERCENT,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum InfixOp {
+    MUL,
+    DIV,
+    ADD,
+    SUB,
+    AND,
+    OR,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Expr {
+    Literal(Literal),
+    CellRef(CellRef),
+    Function {
+        name: String,
+        args: Vec<Expr>,
+    },
+    Group(Box<Expr>),
+    Prefix {
+        op: PrefixOp,
+        expr: Box<Expr>,
+    },
+    Postfix {
+        op: PostfixOp,
+        expr: Box<Expr>,
+    },
+    Infix {
+        op: InfixOp,
+        lhs: Box<Expr>,
+        rhs: Box<Expr>,
+    },
+}
+
+// Ref: https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html
+// We have left and right precedence as to allow associative operators
+// to parse as you would more expect and to break ties in a predictable manner
+pub trait Precedence {
+    fn prec(&self) -> (u8, u8);
+}
+
+impl Precedence for InfixOp {
+    fn prec(&self) -> (u8, u8) {
+        match self {
+            InfixOp::MUL | InfixOp::DIV | InfixOp::AND => (3, 4),
+            InfixOp::ADD | InfixOp::SUB | InfixOp::OR => (1, 2),
+        }
+    }
+}
+impl Precedence for PrefixOp {
+    fn prec(&self) -> (u8, u8) {
+        match self {
+            _it => (0, 5),
+        }
+    }
+}
+impl Precedence for PostfixOp {
+    fn prec(&self) -> (u8, u8) {
+        match self {
+            _it => (6, 0),
+        }
+    }
+}
+
+impl fmt::Display for Expr {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Expr::Literal(lit) => write!(f, "{lit:?}"),
+            Expr::Group(expr) => write!(f, "({expr})"),
+            Expr::Prefix { op, expr } => write!(f, "({op:?} {expr})"),
+            Expr::Postfix { op, expr } => write!(f, "({op:?} {expr})"),
+            Expr::Infix { op, lhs, rhs } => write!(f, "({lhs} {op:?} {rhs})"),
+            Expr::Function { name, args } => write!(f, "{name}({args:?})"),
+            Expr::CellRef(it) => write!(f, "{it:?}"),
+        }
+    }
+}
+
+#[allow(dead_code)]
+impl Expr {
+    pub fn pretty(&self) -> String {
+        // entry point for users — root printed without └──
+        let mut result = String::new();
+        result.push_str(&format!("{}\n", self.node_name()));
+        result.push_str(&self.pretty_subtree("", true));
+        result
+    }
+
+    fn pretty_subtree(&self, prefix: &str, is_tail: bool) -> String {
+        let mut result = String::new();
+        let new_prefix = if is_tail {
+            format!("{}    ", prefix)
+        } else {
+            format!("{}│   ", prefix)
+        };
+
+        match self {
+            Expr::Literal(_) => {}
+            Expr::CellRef(_) => {}
+            Expr::Group(expr) => {
+                result.push_str(&expr.pretty_branch(&new_prefix, true));
+            }
+            Expr::Prefix { expr, .. } => {
+                result.push_str(&expr.pretty_branch(&new_prefix, true));
+            }
+            Expr::Postfix { expr, .. } => {
+                result.push_str(&expr.pretty_branch(&new_prefix, true));
+            }
+            Expr::Infix { lhs, rhs, .. } => {
+                result.push_str(&lhs.pretty_branch(&new_prefix, false));
+                result.push_str(&rhs.pretty_branch(&new_prefix, true));
+            }
+            Expr::Function { args, .. } => {
+                for (idx, arg) in args.iter().enumerate() {
+                    result.push_str(&arg.pretty_branch(&new_prefix, idx == args.len() - 1));
+                }
+            }
+        }
+        result
+    }
+
+    fn pretty_branch(&self, prefix: &str, is_tail: bool) -> String {
+        let mut result = String::new();
+        let branch = if is_tail { "└── " } else { "├── " };
+        result.push_str(&format!("{}{}{}\n", prefix, branch, self.node_name()));
+        result.push_str(&self.pretty_subtree(prefix, is_tail));
+        result
+    }
+
+    fn node_name(&self) -> String {
+        match self {
+            Expr::Literal(lit) => format!("Literal({:?})", lit),
+            Expr::Group(_) => "Group".to_string(),
+            Expr::Prefix { op, .. } => format!("Prefix({:?})", op),
+            Expr::Postfix { op, .. } => format!("Postfix({:?})", op),
+            Expr::Infix { op, .. } => format!("Infix({:?})", op),
+            Expr::Function { name, .. } => format!("Function({:?})", name),
+            Expr::CellRef(it) => format!("{:?}", it),
+        }
+    }
+}
+
+pub fn parse(input: &str) -> Result<(Expr, HashSet<CellRef>), String> {
+    let mut tokenizer = Tokenizer::new(input)?;
+    // println!("{:?}", tokenizer.tokens);
+    let mut deps = HashSet::new();
+    Ok((_parse(&mut tokenizer, 0, &mut deps)?, deps))
+}
+
+pub fn _parse(
+    input: &mut Tokenizer,
+    min_prec: u8,
+    deps: &mut HashSet<CellRef>,
+) -> Result<Expr, String> {
+    let mut lhs = match input.next() {
+        Token::Literal(it) => Expr::Literal(it),
+        Token::Identifier(id) if id == "true" => Expr::Literal(Literal::Boolean(true)),
+        Token::Identifier(id) if id == "false" => Expr::Literal(Literal::Boolean(false)),
+        Token::Paren('(') => {
+            let lhs = _parse(input, 0, deps)?;
+            if input.next() != Token::Paren(')') {
+                return Err(format!("Parse error: expected closing paren."));
+            }
+            Expr::Group(Box::new(lhs))
+        }
+        Token::Operator(op) => {
+            let prefix_op = match op {
+                '+' => PrefixOp::POS,
+                '-' => PrefixOp::NEG,
+                '!' => PrefixOp::NOT,
+                it => return Err(format!("Parse error: unknown prefix operator {:?}.", it)),
+            };
+
+            let rhs = _parse(input, prefix_op.prec().1, deps)?;
+
+            Expr::Prefix {
+                op: prefix_op,
+                expr: Box::new(rhs),
+            }
+        }
+        Token::Identifier(id) => match input.peek() {
+            Token::Paren('(') => {
+                input.next();
+
+                let mut args: Vec<Expr> = Vec::new();
+                loop {
+                    let nxt = input.peek();
+
+                    if nxt == Token::Paren(')') {
+                        input.next();
+                        break;
+                    } else if nxt != Token::Comma && args.len() != 0 {
+                        return Err(format!(
+                            "Parse error: expected comma while parsing argument of function {:?}.",
+                            id
+                        ));
+                    }
+
+                    if args.len() != 0 {
+                        input.next(); // Skip comma
+                    }
+
+                    let arg = _parse(input, 0, deps)?;
+                    args.push(arg);
+                }
+
+                Expr::Function {
+                    name: id,
+                    args: args,
+                }
+            }
+            _ => {
+                let cell_ref = CellRef::new(id)?;
+                deps.insert(cell_ref);
+                Expr::CellRef(cell_ref)
+            }
+        },
+
+        it => return Err(format!("Parse error: did not expect token {:?}.", it)),
+    };
+
+    // In the reference article this is a loop with match
+    // statement that breaks on Eof and closing paren but this is simpler and works as expected
+    while let Token::Operator(op) = input.peek() {
+        if "+-*/&|".contains(op) {
+            let infix_op = match op {
+                '+' => InfixOp::ADD,
+                '-' => InfixOp::SUB,
+                '*' => InfixOp::MUL,
+                '/' => InfixOp::DIV,
+                '&' => InfixOp::AND,
+                '|' => InfixOp::OR,
+                it => {
+                    return Err(format!("Parse error: do not know infix operator {:?}.", it));
+                }
+            };
+
+            let (l_prec, r_prec) = infix_op.prec();
+            if l_prec < min_prec {
+                break;
+            }
+
+            input.next();
+            let rhs = _parse(input, r_prec, deps)?;
+            lhs = Expr::Infix {
+                op: infix_op,
+                lhs: Box::new(lhs),
+                rhs: Box::new(rhs),
+            };
+        } else if "%".contains(op) {
+            let postfix_op = match op {
+                '%' => PostfixOp::PERCENT,
+                it => {
+                    return Err(format!(
+                        "Parse error: do not know postfix operator {:?}.",
+                        it
+                    ));
+                }
+            };
+
+            let (l_prec, _) = postfix_op.prec();
+            if l_prec < min_prec {
+                break;
+            }
+
+            input.next();
+            lhs = Expr::Postfix {
+                op: postfix_op,
+                expr: Box::new(lhs),
+            };
+        }
+    }
+
+
+    Ok(lhs)
+}

backend/src/tokenizer.rs

@@ -0,0 +1,136 @@
+#[derive(Debug, Clone, PartialEq)]
+pub enum Literal {
+    Integer(i64),
+    Double(f64),
+    Boolean(bool),
+    String(String),
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Token {
+    Identifier(String), // Could be a function
+    Literal(Literal),
+    Operator(char),
+    Paren(char),
+    Comma,
+    Eof,
+}
+
+pub struct Tokenizer {
+    pub tokens: Vec<Token>,
+}
+
+impl Tokenizer {
+    pub fn new(input: &str) -> Result<Tokenizer, String> {
+        let mut tokens = Vec::new();
+        let mut chars = input.chars().peekable();
+
+        while let Some(&c) = chars.peek() {
+            if c.is_whitespace() {
+                chars.next();
+            } else if c.is_ascii_alphabetic() {
+                // parse identifier
+                let mut ident = String::new();
+                while let Some(&ch) = chars.peek() {
+                    if ch.is_ascii_alphanumeric() || ch == '_' {
+                        ident.push(ch);
+                        chars.next();
+                    } else {
+                        break;
+                    }
+                }
+                tokens.push(Token::Identifier(ident));
+            } else if c.is_ascii_digit() {
+                // parse number
+                let mut number = String::new();
+                let mut is_decimal = false;
+
+                while let Some(&ch) = chars.peek() {
+                    if ch.is_ascii_digit() {
+                        number.push(ch);
+                        chars.next();
+                    } else if ch == '.' && !is_decimal {
+                        is_decimal = true;
+                        number.push(ch);
+                        chars.next();
+                    } else {
+                        break;
+                    }
+                }
+                if is_decimal {
+                    tokens.push(Token::Literal(Literal::Double(number.parse().unwrap())))
+                } else {
+                    tokens.push(Token::Literal(Literal::Integer(number.parse().unwrap())))
+                };
+            } else if c == '"' || c == '\'' {
+                // parse string literal
+                let mut string = String::new();
+
+                let quote = c;
+                let mut escapes = 0;
+                chars.next(); // consume opening quote
+
+                while let Some(&ch) = chars.peek() {
+                    chars.next();
+                    if ch == quote && escapes % 2 == 0 {
+                        break;
+                    }
+
+                    if ch == '\\' {
+                        escapes += 1;
+                    } else {
+                        escapes = 0;
+                    }
+
+                    string.push(ch);
+                }
+                tokens.push(Token::Literal(Literal::String(string)));
+            } else if "+-*/^!%&|".contains(c) {
+                tokens.push(Token::Operator(c));
+                chars.next();
+            } else if "()".contains(c) {
+                tokens.push(Token::Paren(c));
+                chars.next();
+            } else if c == ',' {
+                tokens.push(Token::Comma);
+                chars.next();
+            } else {
+                return Err(format!("Encountered unknown token char: {c}"));
+            }
+        }
+
+        tokens.reverse(); // Since we want FIFO and next + peek are implemented as LILO
+        Ok(Tokenizer { tokens })
+    }
+
+    pub fn next(&mut self) -> Token {
+        self.tokens.pop().unwrap_or(Token::Eof)
+    }
+    pub fn peek(&mut self) -> Token {
+        self.tokens.last().cloned().unwrap_or(Token::Eof)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_tokenizer() {
+        let raw = "hello hello 1.23 this 5 (1+2)";
+        let expected: Vec<Token> = vec![
+            Token::Identifier("hello".to_string()),
+            Token::Identifier("hello".to_string()),
+            Token::Literal(Literal::Double(1.23)),
+            Token::Identifier("this".to_string()),
+            Token::Literal(Literal::Integer(5)),
+            Token::Paren('('),
+            Token::Literal(Literal::Integer(1)),
+            Token::Operator('+'),
+            Token::Literal(Literal::Integer(2)),
+            Token::Paren(')'),
+        ];
+        let t = Tokenizer::new(&raw).unwrap();
+        assert_eq!(t.tokens, expected);
+    }
+}