;;; ludic-mode.el --- Major mode for the Ludic game language -*- lexical-binding: t; -*-

;; Highlighting here is a deliberate minimum: enough for a file to be readable
;; with nothing installed. Everything real -- completion, diagnostics, hover,
;; formatting -- comes from ludic-lsp via eglot (built into Emacs 29) or lsp-mode.
;;
;; Usage:
;;   (add-to-list 'load-path "/path/to/gpp/tools/editors/emacs")
;;   (require 'ludic-mode)

;;; Code:

;; The vocabulary mirrors tools/ludic-tools/ludic_syntax.h; that header is the reference.
(defconst ludic--declaration-keywords
  '("program" "import" "property" "model" "enum" "ui" "namespace"
    "const" "var" "function" "extern" "handler" "entry" "event" "scene" "test" "prefab"))

(defconst ludic--clause-keywords
  '("phase" "query" "on" "cancellable" "public" "layer" "start" "shows" "lasts" "loads" "then" "export" "internal"))

(defconst ludic--statement-keywords
  '("let" "return" "if" "else" "while" "for" "in" "spawn" "despawn"
    "enable" "disable" "attach" "detach" "match" "machine" "state" "become" "where"
    "and" "or" "not" "break" "continue" "new" "emit" "cancel" "try"))

(defconst ludic--types
  '("int" "long" "fixed" "countdown" "bool" "entity" "string" "pointer" "byte"
    "words" "fixeds" "pointers" "Vector" "IVec2" "Rect" "void"))
(defconst ludic--phases '("Start" "Input" "FixedUpdate" "Update" "LateUpdate" "Render" "Overlay"))

(defconst ludic-font-lock-keywords
  (list
   (cons (regexp-opt ludic--declaration-keywords 'symbols) 'font-lock-keyword-face)
   (cons (regexp-opt ludic--clause-keywords 'symbols) 'font-lock-preprocessor-face)
   (cons (regexp-opt ludic--statement-keywords 'symbols) 'font-lock-keyword-face)
   (cons (regexp-opt ludic--types 'symbols) 'font-lock-type-face)
   (cons (regexp-opt ludic--phases 'symbols) 'font-lock-builtin-face)
   (cons "\\_<\\(true\\|false\\|null\\)\\_>" 'font-lock-constant-face)
   (cons "@[A-Za-z_][A-Za-z0-9_]*" 'font-lock-preprocessor-face)
   ;; components, archetypes, scenes and UI handles are Capitalised by convention
   (cons "\\_<[A-Z][A-Za-z0-9_]*\\_>" 'font-lock-type-face)
   (cons "\\_<\\([a-z_][A-Za-z0-9_]*\\)\\s-*(" '(1 font-lock-function-name-face))))

(defvar ludic-mode-syntax-table
  (let ((table (make-syntax-table)))
    (modify-syntax-entry ?# "<" table)
    (modify-syntax-entry ?\n ">" table)
    (modify-syntax-entry ?_ "_" table)
    (modify-syntax-entry ?\" "\"" table)
    table)
  "Syntax table for `ludic-mode'.")

;;;###autoload
(define-derived-mode ludic-mode prog-mode "Ludic"
  "Major mode for editing Ludic source."
  :syntax-table ludic-mode-syntax-table
  (setq-local font-lock-defaults '(ludic-font-lock-keywords))
  (setq-local comment-start "# ")
  (setq-local comment-end "")
  (setq-local indent-tabs-mode nil)
  (setq-local tab-width 2)
  (setq-local standard-indent 2))

;;;###autoload
(add-to-list 'auto-mode-alist '("\\.ludic\\'" . ludic-mode))

;; eglot: one line, and the server does the rest. Markdown is registered too so
;; that ```ludic fences are analysed in prose files.
(with-eval-after-load 'eglot
  (add-to-list 'eglot-server-programs '(ludic-mode . ("ludic-lsp" "--stdio"))))

(provide 'ludic-mode)
;;; ludic-mode.el ends here