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perga-mode.el

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+;;; perga-mode.el --- major mode for perga  -*- lexical-binding: t; -*-
+
+;; Author: William Ball <wball@ballcloud.cc>
+;; Maintainer: William Ball <wball@ballcloud.cc>
+;; Version: 0.1
+;; Package-Requires: ((emacs "29.1"))
+;; Homepage: https://forgejo.ballcloud.cc/wball/perga-mode
+;; Keywords: languages, tree-sitter
+
+;; This file is not part of GNU Emacs.
+
+;;; Commentary:
+
+;; Major mode for editing perga code, with Tree-sitter-based
+;; font-lock support.  Requires Emacs 29 or newer.
+
+;;; Code:
+
+(require 'treesit)
+
+(defun perga--ensure-treesit-grammar ()
+  "Ensure the perga Tree-sitter grammar is installed."
+  (unless (treesit-ready-p 'perga)
+    (add-to-list 'treesit-language-source-alist
+		 '(perga . ("~/repos/tree-sitter-perga/")))
+                 ;'(perga . ("https://forgejo.ballcloud.cc/wball/tree-sitter-perga")))
+    (when (yes-or-no-p "Tree-sitter grammar for perga not found. Install it now? ")
+      (treesit-install-language-grammar 'perga))))
+
+(defvar perga--font-lock-rules
+    '(:language perga
+      :override t
+      :feature keyword
+      ([ "fun" "λ" "forall" "∏" "let" "in" "end" "def" "axiom" "variable" "hypothesis" "section" "infixl" "infixr" "[" "]" ] @font-lock-keyword-face)
+
+      :language perga
+      :override t
+      :feature preprocessor
+      ((preprocess
+	(command) @font-lock-preprocessor-face
+	(post_command) @font-lock-string-face))
+
+      :language perga
+      :override t
+      :feature delimiter
+      ([ "=>" "→" "⇒" "," ":=" ";" ":" ] @font-lock-delimiter-face)
+
+      :language perga
+      :override t
+      :feature operator
+      ((symbol) @font-lock-operator-face)
+
+      :language perga
+      :override t
+      :feature constant
+      ([(star) (square)] @font-lock-constant-face)
+
+      :language perga
+      :override t
+      :feature comment
+      ((comment) @font-lock-comment-face)
+
+      :language perga
+      :override t
+      :feature definition
+      ((definition
+	name: (identifier) @font-lock-function-name-face))
+
+      :language perga
+      :override t
+      :feature definition
+      ((axiom
+	name: (identifier) @font-lock-function-name-face))
+
+      :language perga
+      :override t
+      :feature assignment
+      ((binding
+	(identifier) @font-lock-function-name-face))
+
+      :language perga
+      :override t
+      :feature parameter
+      ((param_block
+	param: (identifier)+ @font-lock-variable-name-face))
+
+      :language perga
+      :override t
+      :feature type
+      ((param_block
+	type: (expr) @font-lock-type-face))
+
+      :language perga
+      :override t
+      :feature type
+      ((labs_alt
+	type: (expr) @font-lock-type-face))
+
+      :language perga
+      :override t
+      :feature parameter
+      ((labs_alt
+	param: (identifier)+ @font-lock-variable-name-face))
+
+      :language perga
+      :override t
+      :feature type
+      ((ascription
+	type: (expr) @font-lock-type-face))))
+
+(defun perga--setup ()
+  "Setup treesit for perga-mode."
+  (setq-local treesit-font-lock-settings
+               (apply #'treesit-font-lock-rules
+                      perga--font-lock-rules))
+
+  (setq-local font-lock-defaults nil)
+  
+  (setq-local treesit-font-lock-feature-list
+	      '((comment definition)
+		(keyword type constant preprocessor)
+		(assignment parameter delimiter operator)))
+
+  (setq-local treesit-font-lock-level 3)
+
+  ;; (setq-local treesit-simple-indent-rules
+  ;; 	      `((perga
+  ;; 		 ((parent-is "program") column-0 0)
+  ;; 		 ((node-is ":=") parent 4)
+  ;; 		 ((parent-is "definition") parent 4)
+  ;; 		 ((parent-is "labs") parent 4)
+  ;; 		 (no-node parent 0))))
+
+  (treesit-major-mode-setup))
+
+;;;###autoload
+(define-derived-mode perga-mode prog-mode "perga"
+  "Major mode for perga files."
+  (perga--ensure-treesit-grammar)
+  (when (treesit-ready-p 'perga)
+    (treesit-parser-create 'perga)
+    (perga--setup)))
+
+(defun perga-typecheck-current-file ()
+  "Typecheck the current file using the `perga` executable"
+  (interactive))
+
+(defvar perga-mode-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "C-c c" #'do-stuff)
+    map))
+
+(provide 'perga-mode)
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.pg" . perga-mode))
+
+;;; perga-mode.el ends here