init.el

;;; init.el --- Scala IDE configuration for Emacs 30.2
;;; -*- lexical-binding: t -*-

;; ============================================================
;; SECTION 1: Package Manager Bootstrap
;; ============================================================

(require 'package)

;; Package archives: MELPA (latest) + GNU + NonGNU
(setq package-archives
      '(("gnu"    . "https://elpa.gnu.org/packages/")
        ("nongnu" . "https://elpa.nongnu.org/packages/")
        ("melpa"  . "https://melpa.org/packages/")))

(package-initialize)

;; Refresh package list on first run
(unless package-archive-contents
  (package-refresh-contents))

;; Bootstrap use-package (built into Emacs 29+, but ensure it's loaded)
(require 'use-package)
(setq use-package-always-ensure t
      use-package-verbose t)         ; log what's being loaded (helpful for debugging)

;; ============================================================
;; SECTION 2: Core Editor Behaviour
;; ============================================================

;; UTF-8 everywhere
(set-language-environment "UTF-8")
(prefer-coding-system 'utf-8)

;; UI cleanup
(setq inhibit-startup-screen t
      ring-bell-function 'ignore)
(tool-bar-mode -1)
(menu-bar-mode -1)
(scroll-bar-mode -1)

;; Line numbers in programming modes
(add-hook 'prog-mode-hook #'display-line-numbers-mode)

;; Show matching parens
(show-paren-mode 1)

;; Tabs → spaces, 2-wide (Scala convention)
(setq-default indent-tabs-mode nil
              tab-width 2)

;; Remember recent files
(recentf-mode 1)

;; Better buffer names when files share a name
(require 'uniquify)
(setq uniquify-buffer-name-style 'forward)

;; Auto-refresh buffers when file changes on disk
(global-auto-revert-mode 1)

;; Save backup files to a dedicated dir (not cluttering your project)
(setq backup-directory-alist `(("." . ,(expand-file-name "backups" user-emacs-directory)))
      auto-save-file-name-transforms `((".*" ,(expand-file-name "auto-saves/" user-emacs-directory) t)))

;; ============================================================
;; SECTION 3: which-key — shows available keybindings
;; ============================================================

(use-package which-key
  :config
  (which-key-mode)
  (setq which-key-idle-delay 0.5))

;; ============================================================
;; SECTION 4: Tree-sitter (Emacs 29+ built-in, enhanced syntax)
;; ============================================================

;; tree-sitter gives much richer syntax highlighting than regex modes.
;; scala-ts-mode uses it. We install the grammar if not present.
(use-package treesit-auto
  :config
  (setq treesit-auto-install 'prompt)  ; will ask before downloading grammars
  (treesit-auto-add-to-auto-mode-alist 'all)
  (global-treesit-auto-mode))

;; ============================================================
;; SECTION 5: Scala Mode (syntax + indentation)
;; ============================================================

;; scala-mode is the traditional mode; scala-ts-mode is the tree-sitter version.
;; We install both. lsp-metals works with either.
(use-package scala-mode
  :mode (("\\.scala\\'" . scala-mode)
         ("\\.sc\\'"    . scala-mode))  ; .sc = Scala script / Ammonite
  :interpreter ("scala" . scala-mode)
  :config
  (setq scala-indent:use-javadoc-style t))

;; ============================================================
;; SECTION 6: sbt-mode (build tool integration)
;; ============================================================

(use-package sbt-mode
  :commands (sbt-start sbt-command sbt-run-previous-command)
  :config
  (setq sbt:program-options '("-Dsbt.supershell=false")))

;; ============================================================
;; SECTION 7: Company (completion UI)
;; ============================================================

(use-package company
  :hook (prog-mode . company-mode)
  :config
  (setq company-minimum-prefix-length 1
        company-idle-delay             0.2    ; slight delay avoids flickering
        company-tooltip-align-annotations t
        company-show-quick-access      t))

;; ============================================================
;; SECTION 8: Flycheck (error/warning display)
;; ============================================================

(use-package flycheck
  :hook (prog-mode . flycheck-mode))

;; ============================================================
;; SECTION 9: LSP Mode
;; ============================================================

(use-package lsp-mode
  :hook
  ((scala-mode . lsp-deferred)   ; lsp-deferred starts LSP lazily (better startup)
   (lsp-mode   . lsp-lens-mode)) ; show code lens (references count, run/test actions)
  :init
  ;; lsp-mode prefix key — all LSP commands under C-c l
  (setq lsp-keymap-prefix "C-c l")
  :config
  ;; --- Performance tuning (important for Scala which has large responses) ---
  (setq lsp-idle-delay                    0.5   ; how long to wait before asking server
        lsp-response-timeout              30    ; metals can be slow on cold start
        read-process-output-max           (* 4 1024 1024)  ; 4MB - critical for metals
        gc-cons-threshold                 100000000)       ; reduce GC pressure

  ;; --- UI preferences ---
  (setq lsp-headerline-breadcrumb-enable  t     ; shows class/method path in header
        lsp-headerline-breadcrumb-segments '(project file symbols)
        lsp-enable-snippet                t     ; enables snippet completions
        lsp-completion-enable             t
        lsp-signature-auto-activate       t     ; show signature help as you type args
        lsp-signature-render-documentation t

  ;; --- Diagnostics ---
        lsp-diagnostics-provider          :flycheck  ; use flycheck (not flymake)

  ;; --- File watching (disable for large projects if slow) ---
        lsp-enable-file-watchers          t
        lsp-file-watch-threshold          5000)

  ;; Enable which-key integration for the C-c l prefix
  (lsp-enable-which-key-integration t))

;; ============================================================
;; SECTION 10: LSP UI (hover docs, sideline diagnostics, peek)
;; ============================================================

(use-package lsp-ui
  :hook (lsp-mode . lsp-ui-mode)
  :config
  ;; Sideline: shows errors/warnings inline at end of line
  (setq lsp-ui-sideline-enable            t
        lsp-ui-sideline-show-diagnostics  t
        lsp-ui-sideline-show-hover        nil  ; can be noisy; toggle with C-c l T s
        lsp-ui-sideline-show-code-actions t
        lsp-ui-sideline-delay             0.2)

  ;; Doc popup on hover (eldoc-style but richer)
  (setq lsp-ui-doc-enable                 t
        lsp-ui-doc-position               'at-point  ; alternatives: 'top 'bottom
        lsp-ui-doc-delay                  0.5
        lsp-ui-doc-show-with-cursor       nil  ; show on cursor idle
        lsp-ui-doc-show-with-mouse        t    ; show on mouse hover
        lsp-ui-doc-include-signature      t
        lsp-ui-doc-max-width              80
        lsp-ui-doc-max-height             20)

  ;; Peek: show definitions/references in an inline overlay (very useful)
  (setq lsp-ui-peek-enable                t
        lsp-ui-peek-show-directory        t)

  ;; Imenu integration (M-x imenu lists all symbols in file)
  (setq lsp-ui-imenu-enable               t
        lsp-ui-imenu-auto-refresh         t))

;; ============================================================
;; SECTION 11: lsp-metals (Scala-specific Metals server config)
;; ============================================================

(use-package lsp-metals
  :after lsp-mode
  :custom
  (lsp-metals-server-args             '("-J-Xss4m" "-J-Xms512m" "-J-Xmx2g" "-J-XX:+UseG1GC"
                                        "-J-Dmetals.allow-multiline-string-formatting=off"))
  (lsp-metals-enable-indent-on-paste  t)
  (lsp-metals-enable-semantic-highlighting t)
  (lsp-metals-treeview-show-when-views-received t))

;; ============================================================
;; SECTION 12: DAP Mode (Debugging)
;; ============================================================

;; dap-mode provides the Debug Adapter Protocol client.
;; Metals also acts as a DAP server for Scala.

(use-package dap-mode
  :hook
  ((lsp-mode . dap-mode)
   (dap-mode  . dap-ui-mode)
   (dap-mode  . dap-tooltip-mode)
   (dap-mode  . dap-ui-controls-mode))
  :config
  (setq dap-auto-configure-features '(sessions locals breakpoints expressions tooltip))
  ;; dap-scala is loaded conditionally — only if present
  (with-eval-after-load 'scala-mode
    (when (require 'dap-scala nil 'noerror)
      (message "dap-scala loaded successfully")))
  :bind
  (:map dap-mode-map
   ("<f5>"   . dap-debug)
   ("<f6>"   . dap-next)
   ("<f7>"   . dap-step-in)
   ("<f8>"   . dap-step-out)
   ("C-<f5>" . dap-continue)
   ("C-<f9>" . dap-breakpoint-toggle)))

;; ============================================================
;; SECTION 13: Treemacs (Project file tree, used by lsp-metals tree view)
;; ============================================================

(use-package treemacs
  :bind
  (("C-x t t" . treemacs)
   ("C-x t 1" . treemacs-select-window))
  :config
  (setq treemacs-width 30
        treemacs-show-hidden-files t))

;; lsp-treemacs: integration between lsp-mode and treemacs
;; (used by lsp-metals for the build targets tree)
(use-package lsp-treemacs
  :after (lsp-mode treemacs)
  :config
  (lsp-treemacs-sync-mode 1))

;; ============================================================
;; SECTION 14: Projectile (project management)
;; ============================================================

(use-package projectile
  :bind-keymap
  ("C-c p" . projectile-command-map)
  :config
  (projectile-mode 1)
  (setq projectile-completion-system 'default))

;; ============================================================
;; SECTION 15: Magit (Git integration — too useful to omit)
;; ============================================================

(use-package magit
  :bind ("C-c g" . magit-status))

;; ============================================================
;; SECTION 16: Consult + Vertico (modern minibuffer completion)
;; Optional but transforms M-x, C-x b, C-x f experience
;; ============================================================

(use-package vertico
  :init (vertico-mode))

(use-package orderless
  :config
  (setq completion-styles '(orderless basic)
        completion-category-overrides '((file (styles basic partial-completion)))))

(use-package consult
  :bind
  (("C-x b"   . consult-buffer)
   ("C-x r b" . consult-bookmark)
   ("M-y"     . consult-yank-pop)
   ("M-g g"   . consult-goto-line)
   ("M-s r"   . consult-ripgrep)   ; needs ripgrep installed: sudo apt install ripgrep
   ("M-s f"   . consult-find)))

(use-package marginalia
  :init (marginalia-mode))

;; ============================================================
;; END OF CONFIGURATION
;;; init.el ends here