feat: PPN notation to rotate pieces around a reference location/piece

There is now support for rotating pieces around a reference location/pieces (#86):

* ``PieceId@>Angle|Location`` means rotating ``PieceId`` pieces ``Angle`` angle around ``Location`` location
* ``PieceId1@>Angle$PieceId2`` is a shortcut for ``PieceId1@>Angle|&PieceId2``
* ``PieceId$>Angle`` is a shortcut for ``PieceId@>Angle$PieceId``

Closes #86

DESCRIPTION

@@ -2,7 +2,7 @@ Encoding: UTF-8
 Package: ppgames
 Type: Package
 Title: Piecepack Games
-Version: 0.6.0-17
+Version: 0.6.0-18
 Author: Trevor L Davis. 
 Maintainer: Trevor L Davis <trevor.l.davis@gmail.com>
 Description: This is an R package designed to make piecepack game diagrams.

NEWS.md

@@ -25,6 +25,11 @@ New features
   - ``N?PieceSpec`` is now a shortcut for ``N&?PieceSpec``
   - An empty PieceSpec now refers to the "last active" piece(s)
   - Brace expansions are now expanded before semi-colons are
+  - There is now support for rotating pieces around a reference location/pieces (#86):
+
+    * ``PieceId@>Angle|Location`` means rotating ``PieceId`` pieces ``Angle`` angle around ``Location`` location
+    * ``PieceId1@>Angle$PieceId2`` is a shortcut for ``PieceId1@>Angle|&PieceId2``
+    * ``PieceId$>Angle`` is a shortcut for ``PieceId@>Angle$PieceId``
 
 * New function ``view_game()`` provides a simple command-line PPN viewer/editor.
 * New function ``cat_game()`` renders a plaintext animation of a game within the terminal.

R/ppn.R

@@ -673,6 +673,8 @@ get_coords_from_piece_id <- function(piece_id, df, state = create_state(df)) {
 process_submove <- function(df, text, state = create_state(df)) {
     if (text == "") {
         df
+    } else if (str_detect(text, "\\$>")) {
+        process_percent_rotate_move(df, text, state)
     } else if (str_detect(text, "@>")) {
         process_rotate_move(df, text, state)
     } else if (str_detect(text, "@%")) {
@@ -709,15 +711,40 @@ process_submove <- function(df, text, state = create_state(df)) {
 process_rotate_move <- function(df, text, state = create_state(df), clockwise = TRUE) {
     id_angle <- str_split(text, "@>")[[1]]
     piece_id <- id_angle[1L]
-    angle <- as.numeric(id_angle[2])
-    angle <- ifelse(clockwise, -angle, angle)
-
     indices <- get_indices_from_piece_id(piece_id, df, state)
-    df$angle[indices] <- df$angle[indices] + angle
+    angle <- id_angle[2L]
+    if (str_detect(angle, "\\|")) {
+        angle_coords <- str_split(angle, "\\|", n=2L)[[1L]]
+        angle <- as.numeric(angle_coords[1L])
+        location <- get_xy(angle_coords[2L], df, state)
+    } else if (str_detect(angle, "\\$")) {
+        angle_coords <- str_split(angle, "\\$", n=2L)[[1L]]
+        angle <- as.numeric(angle_coords[1L])
+        location <- get_xy(paste0("&", angle_coords[2L]), df, state)
+    } else {
+        angle <- as.numeric(angle)
+        location <- NULL
+    }
+    angle <- ifelse(clockwise, -angle, angle)
+    if (!is.null(location)) {
+        p <- piecepackr:::Point2D$new(x = df$x[indices], y = df$x[indices])
+        p <- p$translate(-location$x, -location$y)$rotate(angle)$translate(location$x, location$y)
+        df$x[indices] <- p$x
+        df$y[indices] <- p$y
+    }
+    df$angle[indices] <- (df$angle[indices] + angle)
     state$active_id <- df$id[indices]
     df
 }
 
+process_percent_rotate_move <- function(df, text, state = create_state(df)) {
+    pa <- str_split(text, "\\$>")[[1L]]
+    piece_spec <- pa[1L]
+    angle <- pa[2L]
+    text <- str_glue("{piece_spec}@>{angle}${piece_spec}")
+    process_rotate_move(df, text, state)
+}
+
 process_hash_move <- function(df, text, state = create_state(df)) {
     id1_id2 <- str_split(text, "#")[[1]]
     piece_id1 <- id1_id2[1L]

tests/testthat/test_ppn.R

@@ -488,6 +488,19 @@ test_that("rotations work as expected", {
     expect_equal(df$angle, 0)
     df <- process_move(df, "b2@>-90")
     expect_equal(df$angle, 90)
+    df <- initialize_df(df_none())
+    df <- process_move(df, "C3@(1.5,1.5) S@a1 M@b2 3?C3@>180|b2")
+    expect_equal(df$angle, rep(-180, 3))
+    expect_equal(df$x, c(2.5,3,2))
+    expect_equal(df$y, c(2.5,3,2))
+    df <- process_move(df, "3?C3@>-180$?M")
+    expect_equal(df$angle, rep(0, 3))
+    expect_equal(df$x, c(1.5,1,2))
+    expect_equal(df$y, c(1.5,1,2))
+    df <- process_move(df, "3?C3$>180")
+    expect_equal(df$angle, rep(-180, 3))
+    expect_equal(df$x, c(1.5,2,1))
+    expect_equal(df$y, c(1.5,2,1))
 })
 
 test_that("address works as expected", {