add uninstall script and Just commands

Justfile

@@ -28,5 +28,15 @@ install: (package "@local")
 # install the library with the "@preview" prefix (for pre-release testing)
 install-preview: (package "@preview")
 
+[private]
+remove target:
+  ./scripts/uninstall "{{target}}"
+
+# uninstalls the library from the "@local" prefix
+uninstall: (remove "@local")
+
+# uninstalls the library from the "@preview" prefix (for pre-release testing)
+uninstall-preview: (remove "@preview")
+
 # run ci suite
 ci: test doc

scripts/uninstall

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+set -eu
+
+# adapted from https://github.com/johannes-wolf/cetz/blob/35c0868378cea5ad323cc0d9c2f76de8ed9ba5bd/scripts/package
+# licensed under Apache License 2.0
+
+# Local package directories per platform
+if [[ "$OSTYPE" == "linux"* ]]; then
+  DATA_DIR="${XDG_DATA_HOME:-$HOME/.local/share}"
+elif [[ "$OSTYPE" == "darwin"* ]]; then
+  DATA_DIR="$HOME/Library/Application Support"
+else
+  DATA_DIR="${APPDATA}"
+fi
+
+if (( $# < 1 )) || [[ "${1:-}" == "help" ]]; then
+  echo "uninstall TARGET"
+  echo ""
+  echo "removes the package installed into a directory named '<name>/<version>'"
+  echo "at TARGET. If TARGET is set to @local or @preview, the local Typst package"
+  echo "directory will be used so that the package gets installed for local use."
+  echo "The name and version are read from 'typst.toml' in the project root."
+  echo ""
+  echo "Local package prefix: $DATA_DIR/typst/package/local"
+  echo "Local preview package prefix: $DATA_DIR/typst/package/preview"
+  exit 1
+fi
+
+function read-toml() {
+  local file="$1"
+  local key="$2"
+  # Read a key value pair in the format: <key> = "<value>"
+  # stripping surrounding quotes.
+  perl -lne "print \"\$1\" if /^${key}\\s*=\\s*\"(.*)\"/" < "$file"
+}
+
+ROOT="$(cd "$(dirname "$0")"; pwd -P)/.." # macOS has no realpath
+TARGET="${1:?Missing target path, @local or @preview}"
+PKG_PREFIX="$(read-toml "$ROOT/typst.toml" "name")"
+VERSION="$(read-toml "$ROOT/typst.toml" "version")"
+
+if [[ "$TARGET" == "@local" ]]; then
+  TARGET="${DATA_DIR}/typst/packages/local/"
+  echo "Install dir: $TARGET"
+elif [[ "$TARGET" == "@preview" ]]; then
+  TARGET="${DATA_DIR}/typst/packages/preview/"
+  echo "Install dir: $TARGET"
+fi
+
+TARGET="${TARGET:?}/${PKG_PREFIX:?}/${VERSION:?}"
+echo "Package to uninstall: $TARGET"
+if [[ ! -e "${TARGET:?}" ]]; then
+  echo "Package was not found."
+elif rm -r "${TARGET:?}" 2>/dev/null; then
+  echo "Successfully removed."
+else
+  echo "Removal failed."
+fi