Add {for} block

src/internal/execute.rs

@@ -2,32 +2,64 @@ use core::fmt::Write;
 
 use crate::Value;
 
-use super::parse::{Ast, AstKind, Print};
+use super::parse::{Ast, AstKind, For, Print, ValuePath};
 
 pub fn execute(ast: &Ast, value: &dyn Value) -> String {
 	let mut out = String::new();
-	for node in ast {
-		match node {
-			AstKind::Text(t) => out.push_str(&t),
-			AstKind::Print(p) => print(&mut out, p, value),
-			e => todo!("{e:?}"),
-		}
-	}
+	execute_(&mut out, ast, value);
 
 	out
 }
 
-pub fn print(out: &mut String, p: &Print, value: &dyn Value) {
-	let path = &p.0 .0;
+pub fn execute_(out: &mut String, ast: &Ast, value: &dyn Value) {
+	for node in ast {
+		match node {
+			AstKind::Text(t) => out.push_str(&t),
+			AstKind::Print(p) => print(out, p, value),
+			AstKind::For(f) => for_(out, f, value),
+			e => todo!("{e:?}"),
+		}
+	}
+}
+
+pub fn lookup<'a>(
+	out: &mut String,
+	path: &ValuePath,
+	value: &'a dyn Value,
+) -> Option<&'a dyn Value> {
 	let mut value = value;
-	for name in path {
+	for name in &path.0 {
 		match value.lookup(name) {
 			Some(p) => value = p,
 			None => {
-				let _ = write!(out, "'{name}' missing in current value");
+				let path = path.0.join(".");
+				let _ = write!(out, "'.{path}' not found in current value");
+				return None;
 			},
 		}
 	}
 
+	Some(value)
+}
+
+pub fn print(out: &mut String, p: &Print, value: &dyn Value) {
+	let value = match lookup(out, &p.0, value) {
+		Some(v) => v,
+		None => return,
+	};
+
 	value.print(out)
 }
+
+pub fn for_(out: &mut String, f: &For, value: &dyn Value) {
+	let value = match lookup(out, &f.expr, value) {
+		Some(v) => v,
+		None => return,
+	};
+
+	let mut idx = 0;
+	while let Some(value) = value.for_(idx) {
+		execute_(out, &f.body, value);
+		idx += 0;
+	}
+}

src/internal/parse.rs

@@ -12,8 +12,8 @@ pub struct If {
 
 #[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct For {
-	expr: Expr,
-	body: Ast,
+	pub expr: Expr,
+	pub body: Ast,
 }
 
 #[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -76,38 +76,47 @@ impl<'a> ParseState<'a> {
 
 	pub fn parse(&mut self) {
 		while self.has_input() {
-			let started_at = self.current_byte_offset;
-			let block_start = match self.remaining().find('{') {
-				Some(bs) => bs,
-				None => {
-					self.current_byte_offset = self.last_byte_offset;
+			self.parse_one();
+		}
+
+		self.text_might_end();
 		self.add_current_text_to_ast();
-					break;
-				},
-			};
-			self.current_byte_offset += block_start;
+	}
+
+	pub fn parse_one(&mut self) {
+		assert!(self.has_input());
+		let started_at = self.current_byte_offset;
+		if self.remaining().starts_with('{') {
 			self.text_might_end();
 			self.maybe_parse_block();
+		} else {
+			self.current_byte_offset += 1;
+		}
 
 		if started_at == self.current_byte_offset {
 			panic!("Parser made no progress");
 		}
 	}
-	}
 
 	pub fn maybe_parse_block(&mut self) {
 		assert!(self.remaining().starts_with('{'));
 		self.current_byte_offset += 1;
 		self.skip_whitespace();
 
-		if self.remaining().starts_with('.') {
+		let remaining = self.remaining();
+		if remaining.starts_with('.') {
 			self.maybe_parse_print();
+		} else if remaining.starts_with("for") {
+			self.maybe_parse_for();
 		}
 	}
 
 	pub fn maybe_parse_print(&mut self) {
 		assert!(self.remaining().starts_with('.'));
-		let path = self.parse_path();
+		let path = match self.parse_path() {
+			None => return,
+			Some(vp) => vp,
+		};
 
 		self.skip_whitespace();
 		if !self.remaining().starts_with('}') {
@@ -119,7 +128,46 @@ impl<'a> ParseState<'a> {
 		self.new_empty_text();
 	}
 
-	pub fn parse_path(&mut self) -> ValuePath {
+	pub fn maybe_parse_for(&mut self) {
+		assert!(self.remaining().starts_with("for"));
+		self.current_byte_offset += "for".len();
+		self.skip_whitespace();
+		let path = match self.parse_path() {
+			None => return,
+			Some(vp) => vp,
+		};
+		self.skip_whitespace();
+		if !self.remaining().starts_with('}') {
+			return;
+		}
+		self.current_byte_offset += 1;
+
+		let mut inner = ParseState {
+			template: self.template,
+			last_byte_offset: self.last_byte_offset,
+			speculative_text_starts_at: self.current_byte_offset,
+			speculative_text_ends_at: self.current_byte_offset,
+			current_byte_offset: self.current_byte_offset,
+			ast: Ast::new(),
+		};
+		while inner.has_input() {
+			if inner.remaining().starts_with("{/for}") {
+				break;
+			}
+			inner.parse_one();
+		}
+		self.current_byte_offset = inner.current_byte_offset;
+		if !self.remaining().starts_with("{/for}") {
+			return;
+		}
+		self.current_byte_offset += "{/for}".len();
+		let body = inner.ast;
+
+		self.push_node_and_text(AstKind::For(For { expr: path, body }));
+		self.new_empty_text();
+	}
+
+	pub fn parse_path(&mut self) -> Option<ValuePath> {
 		assert!(self.remaining().starts_with('.'));
 		self.current_byte_offset += 1;
 		let end = self
@@ -132,7 +180,7 @@ impl<'a> ParseState<'a> {
 
 		self.current_byte_offset += end;
 
-		out
+		Some(out)
 	}
 
 	pub fn push_node_and_text(&mut self, node: AstKind) {
@@ -142,12 +190,14 @@ impl<'a> ParseState<'a> {
 
 	pub fn new_empty_text(&mut self) {
 		self.speculative_text_starts_at = self.current_byte_offset;
-		self.speculative_text_ends_at = self.speculative_text_starts_at + 1;
+		self.speculative_text_ends_at = self.speculative_text_starts_at;
 	}
 
 	pub fn skip_whitespace(&mut self) {
 		while self.has_input() {
 			if self.remaining().starts_with(char::is_whitespace) {
+				self.current_byte_offset +=
+					self.remaining().chars().next().unwrap().len_utf8();
 				continue;
 			}
 			break;
@@ -159,7 +209,7 @@ pub fn parse(template: &str) -> Ast {
 	let mut state = ParseState {
 		template,
 		speculative_text_starts_at: 0,
-		speculative_text_ends_at: 1,
+		speculative_text_ends_at: 0,
 		current_byte_offset: 0,
 		last_byte_offset: template.len(),
 		ast: Ast::new(),