feat: Support recursive macros

DESCRIPTION

@@ -2,7 +2,7 @@ Encoding: UTF-8
 Package: ppn
 Type: Package
 Title: Portable Piecepack Notation Parser
-Version: 0.3.0-1
+Version: 0.3.0-2
 Authors@R: c(person("Trevor L.", "Davis", role=c("aut", "cre"),
              email="trevor.l.davis@gmail.com",
              comment = c(ORCID = "0000-0001-6341-4639")))

NEWS.md

@@ -4,6 +4,7 @@ ppn 0.3.0 (development)
 New features
 ------------
 
+* Macros may now reference other macros (recursive macros).  Macro values are fully expanded at parse time; circular references produce an error.
 * We now export (and document their arguments) the following movetext parsers:
 
   + `piecepack_parser()`

R/default_parser.R

@@ -195,7 +195,7 @@ create_state <- function(df, metadata = list()) {
 	}
 	as.environment(list(
 		df_move_start = df,
-		macros = c(metadata$Macros, attr(df, "macros"), macros),
+		macros = expand_macro_values(c(metadata$Macros, attr(df, "macros"), macros)),
 		max_id = nrow(df),
 		active_id = character(),
 		scale_factor = as.numeric(scale_factor)

R/parse_moves.R

@@ -1170,10 +1170,39 @@ get_y <- function(coords) {
 	}
 }
 
+expand_macro_values <- function(macros) {
+	max_iter <- 100L
+	for (i in seq_len(max_iter)) {
+		changed <- FALSE
+		for (name in names(macros)) {
+			value <- macros[[name]]
+			ml <- str_locate_all(value, "`[^']+'")[[1L]]
+			if (nrow(ml) == 0L) {
+				next
+			}
+			for (r in rev(seq_len(nrow(ml)))) {
+				ref <- str_sub(value, ml[r, 1L] + 1L, ml[r, 2L] - 1L)
+				if (!is.null(macros[[ref]])) {
+					str_sub(value, ml[r, 1L], ml[r, 2L]) <- macros[[ref]]
+					changed <- TRUE
+				}
+			}
+			macros[[name]] <- value
+		}
+		if (!changed) {
+			break
+		}
+		if (i == max_iter) {
+			abort("Circular macro reference detected", class = "circular_macro")
+		}
+	}
+	macros
+}
+
 replace_macros <- function(df, text, state = create_state(df)) {
-	ml <- str_locate_all(text, "`[^']+'")[[1]]
+	ml <- str_locate_all(text, "`[^']+'")[[1L]]
 	for (r in rev(seq_len(nrow(ml)))) {
-		mtext <- str_sub(text, ml[r, 1] + 1, ml[r, 2] - 1)
+		mtext <- str_sub(text, ml[r, 1L] + 1L, ml[r, 2L] - 1L)
 		if (is.null(state$macros[[mtext]])) {
 			abort(paste("Macro", mtext, "is unknown"), class = "identify_macro")
 		}

tests/testthat/_snaps/ppn.md

@@ -337,3 +337,11 @@
 
 
 
+# Setup and GameType work as expected
+
+    Code
+      default_parser(c("1. `a'@b2"), meta_circular)
+    Condition
+      Error in `expand_macro_values()`:
+      ! Circular macro reference detected
+

tests/testthat/test_ppn.R

@@ -908,6 +908,32 @@ test_that("Setup and GameType work as expected", {
 	expect_equal(df$suit, 1)
 	expect_equal(df$piece_side, "pawn_face")
 
+	# macro expanding to multiple submoves (e.g. chess castling)
+	meta_castle <- list(
+		GameType = "International Chess",
+		Macros = list("O-O" = "e1-g1 h1-f1")
+	)
+	g_castle <- default_parser(c("1. `O-O'"), meta_castle)
+	df_before <- g_castle$dfs[[1]]
+	df_after <- g_castle$dfs[[2]]
+	king_id <- df_before$id[near(df_before$x, 5) & near(df_before$y, 1)]
+	rook_id <- df_before$id[near(df_before$x, 8) & near(df_before$y, 1)]
+	expect_equal(df_after$x[df_after$id == king_id], 7)
+	expect_equal(df_after$x[df_after$id == rook_id], 6)
+
+	# recursive macro: macro value references another macro
+	meta_recursive <- list(Macros = list(sun = "S", sp = "`sun'p"))
+	df_recursive <- default_parser(c("1. `sp'@b2"), meta_recursive)$dfs[[2]]
+	expect_equal(df_recursive$piece_side, "pawn_face")
+	expect_equal(df_recursive$suit, 1L)
+
+	# circular macro reference is an error
+	meta_circular <- list(Macros = list(a = "`b'", b = "`a'"))
+	expect_snapshot(
+		error = TRUE,
+		default_parser(c("1. `a'@b2"), meta_circular)
+	)
+
 	none1 <- ""
 	df1 <- read_ppn(textConnection(none1))[[1]]$dfs[[1]]
 	expect_equal(nrow(df1), 0)