gbf @ e827329

M src/gbf.gleam

@@ -0,0 +1,10 @@
+import gbf/lexer
+import gbf/parser
+
+pub fn main() {
+  "+.[<>]"
+  |> lexer.new
+  |> lexer.lex
+  |> parser.parse
+  |> echo
+}

A src/gbf/parser.gleam

@@ -0,0 +1,78 @@
+import gbf/lexer.{type Position, Position}
+import gbf/token.{type Token}
+import gleam/list
+import gleam/pair
+import gleam/result
+
+pub type AST {
+  Leaf(#(Token, Position))
+  Node(children: List(AST), position: Position)
+}
+
+pub type Error {
+  FinishedTooEarly
+  UnexpectedCommand
+  UnexpectedBlock
+}
+
+pub fn parse(tokens: List(#(Token, Position))) -> Result(AST, Error) {
+  let root = Node(children: [], position: Position(0))
+
+  use #(ast, remaining_tokens) <- result.try(parse_tokens(tokens, root))
+
+  case remaining_tokens {
+    [] -> Ok(ast)
+    _ -> Error(FinishedTooEarly)
+  }
+}
+
+fn parse_tokens(tokens: List(#(Token, Position)), node: AST) {
+  case tokens {
+    [] -> Ok(#(node, []))
+    [token, ..rest] -> {
+      case token {
+        #(token.StartBlock, _) -> parse_block(token, rest, node)
+        #(token.EndBlock, _) -> parse_block_end(rest, node)
+        _ -> parse_command(token, rest, node)
+      }
+    }
+  }
+}
+
+fn parse_block_end(tokens: List(#(Token, Position)), node: AST) {
+  Ok(#(node, tokens))
+}
+
+fn parse_block(token, tokens, node) {
+  case node {
+    Leaf(_) -> Error(UnexpectedCommand)
+    Node(children, position) -> {
+      let child_block = Node(children: [], position: pair.second(token))
+      use #(parsed_child_block, remaining_tokens) <- result.try(parse_tokens(
+        tokens,
+        child_block,
+      ))
+
+      let new_children = list.append(children, [parsed_child_block])
+      let new_node = Node(children: new_children, position:)
+
+      parse_tokens(remaining_tokens, new_node)
+    }
+  }
+}
+
+fn parse_command(
+  token: #(Token, Position),
+  tokens: List(#(Token, Position)),
+  node: AST,
+) {
+  case node {
+    Leaf(_) -> Error(UnexpectedBlock)
+    Node(children, position) -> {
+      let command = Leaf(token)
+      let node = Node(children: list.append(children, [command]), position:)
+
+      parse_tokens(tokens, node)
+    }
+  }
+}