parse: implement parsing of if-statements

bshell/parse/syntax/if-else.c

@@ -0,0 +1,110 @@
+#include "../syntax.h"
+
+static bool add_branch(
+	struct if_ast_node *group,
+	struct ast_node *cond,
+	struct ast_node *body)
+{
+	struct if_branch_ast_node *branch
+		= (struct if_branch_ast_node *)ast_node_create(AST_IF_BRANCH);
+	if (!branch) {
+		return false;
+	}
+
+	branch->n_cond = cond;
+	branch->n_body = body;
+	fx_queue_push_back(&group->n_branches, &branch->n_base.n_entry);
+
+	return true;
+}
+
+bool parse_if(struct parse_ctx *ctx, struct ast_node **out)
+{
+	if (!parse_keyword(ctx, KW_IF)) {
+		return false;
+	}
+
+	if (!parse_symbol(ctx, SYM_LEFT_PAREN)) {
+		report_error(ctx, "expected `(` after `if`");
+		return false;
+	}
+
+	struct ast_node *if_cond = NULL, *if_body = NULL;
+	if (!parse_expr(ctx, &if_cond)) {
+		report_error(ctx, "invalid if condition");
+		return false;
+	}
+
+	if (!parse_symbol(ctx, SYM_RIGHT_PAREN)) {
+		report_error(ctx, "expected `)` after if-condition");
+		ast_node_destroy(if_cond);
+		return false;
+	}
+
+	if (!parse_block(ctx, &if_body)) {
+		report_error(ctx, "invalid if body");
+		ast_node_destroy(if_cond);
+		return false;
+	}
+
+	struct if_ast_node *if_group
+		= (struct if_ast_node *)ast_node_create(AST_IF);
+	if (!if_group) {
+		ctx->p_status = BSHELL_ERR_NO_MEMORY;
+		ast_node_destroy(if_cond);
+		ast_node_destroy(if_body);
+		return false;
+	}
+
+	if (!add_branch(if_group, if_cond, if_body)) {
+		ctx->p_status = BSHELL_ERR_NO_MEMORY;
+		ast_node_destroy(if_cond);
+		ast_node_destroy(if_body);
+		ast_node_destroy((struct ast_node *)if_group);
+		return false;
+	}
+
+	bool done = false;
+	while (!done) {
+		struct ast_node *cond = NULL, *body = NULL;
+		if (parse_keyword(ctx, KW_ELSE)) {
+			done = true;
+		} else if (parse_keyword(ctx, KW_ELSEIF)) {
+			if (!parse_expr(ctx, &cond)) {
+				report_error(
+					ctx,
+					"invalid conditional expression");
+				ast_node_destroy((struct ast_node *)if_group);
+				return false;
+			}
+		} else {
+			done = true;
+			break;
+		}
+
+		if (!parse_block(ctx, &body)) {
+			report_error(ctx, "invalid conditional body");
+			if (cond) {
+				ast_node_destroy(cond);
+			}
+
+			ast_node_destroy((struct ast_node *)if_group);
+			return false;
+		}
+
+		if (!add_branch(if_group, cond, body)) {
+			report_error(ctx, "failed to add branch to if-group");
+			if (cond) {
+				ast_node_destroy(cond);
+			}
+
+			ast_node_destroy(body);
+			ast_node_destroy((struct ast_node *)if_group);
+			return false;
+		}
+	}
+
+	*out = (struct ast_node *)if_group;
+
+	return true;
+}