;;; fancy-banner.el -*- lexical-binding: t; -*-
;;; Commentary:
;;
;; See https://github.com/tecosaur/emacs-config/blob/master/config.org
;;
;;; Code:
;;;
(setq +doom-dashboard--width 120)

(defvar fancy-splash-image-template
  (expand-file-name "misc/splash-images/blackhole-lines-template.svg" doom-private-dir)
  "Default template svg used for the splash image, with substitutions from ")
(defvar fancy-splash-image-nil
  (expand-file-name "misc/splash-images/transparent-pixel.png" doom-private-dir)
  "An image to use at minimum size, usually a transparent pixel")

(defvar fancy-splash-sizes
  `((:height 400 :min-height 50 :padding (0 . 2))
    (:height 350 :min-height 42 :padding (1 . 4))
    (:height 300 :min-height 35 :padding (1 . 3))
    (:height 250 :min-height 30 :padding (1 . 2))
    (:height 0   :min-height 0  :padding (0 . 0) :file ,fancy-splash-image-nil))
  "list of plists with the following properties
  :height the height of the image
  :min-height minimum `frame-height' for image
  :padding `+doom-dashboard-banner-padding' to apply
  :template non-default template file
  :file file to use instead of template")

(setq fancy-splash-sizes
      `((:height 400 :min-height 40 :padding (0 . 4) :template ,(expand-file-name "misc/splash-images/blackhole-lines-0.svg" doom-private-dir))
        (:height 350 :min-height 32 :padding (1 . 4) :template ,(expand-file-name "misc/splash-images/blackhole-lines-0.svg" doom-private-dir))
        (:height 300 :min-height 28 :padding (1 . 4) :template ,(expand-file-name "misc/splash-images/blackhole-lines-1.svg" doom-private-dir))
        (:height 250 :min-height 26 :padding (1 . 3) :template ,(expand-file-name "misc/splash-images/blackhole-lines-2.svg" doom-private-dir))
        (:height 200 :min-height 24 :padding (1 . 3) :template ,(expand-file-name "misc/splash-images/blackhole-lines-3.svg" doom-private-dir))
        (:height 150 :min-height 22 :padding (1 . 2) :template ,(expand-file-name "misc/splash-images/blackhole-lines-4.svg" doom-private-dir))
        (:height 100 :min-height 20 :padding (1 . 2) :template ,(expand-file-name "misc/splash-images/blackhole-lines-5.svg" doom-private-dir))
        (:height 100 :min-height 14 :padding (1 . 2) :template ,(expand-file-name "misc/splash-images/emacs-e-template.svg" doom-private-dir))
        (:height 0   :min-height 0  :padding (0 . 0) :file ,fancy-splash-image-nil)))


(defvar fancy-splash-template-colours
  '(("$colour1" . keywords) ("$colour2" . type) ("$colour3" . base5) ("$colour4" . base8))
  "list of colour-replacement alists of the form (\"$placeholder\" . 'theme-colour) which applied the template")

(unless (file-exists-p (expand-file-name "theme-splashes" doom-cache-dir))
  (make-directory (expand-file-name "theme-splashes" doom-cache-dir) t))

(defun fancy-splash-filename (theme-name height)
  (expand-file-name (concat (file-name-as-directory "theme-splashes")
                            theme-name
                            "-" (number-to-string height) ".svg")
                    doom-cache-dir))

(defun fancy-splash-clear-cache ()
  "Delete all cached fancy splash images"
  (interactive)
  (delete-directory (expand-file-name "theme-splashes" doom-cache-dir) t)
  (message "Cache cleared!"))

(defun fancy-splash-generate-image (template height)
  "Read TEMPLATE and create an image if HEIGHT with colour substitutions as
   described by `fancy-splash-template-colours' for the current theme"
  (with-temp-buffer
    (insert-file-contents template)
    (re-search-forward "$height" nil t)
    (replace-match (number-to-string height) nil nil)
    (dolist (substitution fancy-splash-template-colours)
      (goto-char (point-min))
      (while (re-search-forward (car substitution) nil t)
        (replace-match (doom-color (cdr substitution)) nil nil)))
    (write-region nil nil
                  (fancy-splash-filename (symbol-name doom-theme) height) nil nil)))

(defun fancy-splash-generate-images ()
  "Perform `fancy-splash-generate-image' in bulk"
  (dolist (size fancy-splash-sizes)
    (unless (plist-get size :file)
      (fancy-splash-generate-image (or (plist-get size :file)
                                       (plist-get size :template)
                                       fancy-splash-image-template)
                                   (plist-get size :height)))))

(defun ensure-theme-splash-images-exist (&optional height)
  (unless (file-exists-p (fancy-splash-filename
                          (symbol-name doom-theme)
                          (or height
                              (plist-get (car fancy-splash-sizes) :height))))
    (fancy-splash-generate-images)))

(defun get-appropriate-splash ()
  (let ((height (frame-height)))
    (cl-some (lambda (size) (when (>= height (plist-get size :min-height)) size))
             fancy-splash-sizes)))

(setq fancy-splash-last-size nil)
(setq fancy-splash-last-theme nil)
(defun set-appropriate-splash (&rest _)
  (let ((appropriate-image (get-appropriate-splash)))
    (unless (and (equal appropriate-image fancy-splash-last-size)
                 (equal doom-theme fancy-splash-last-theme)))
    (unless (plist-get appropriate-image :file)
      (ensure-theme-splash-images-exist (plist-get appropriate-image :height)))
    (setq fancy-splash-image
          (or (plist-get appropriate-image :file)
              (fancy-splash-filename (symbol-name doom-theme) (plist-get appropriate-image :height))))
    (setq +doom-dashboard-banner-padding (plist-get appropriate-image :padding))
    (setq fancy-splash-last-size appropriate-image)
    (setq fancy-splash-last-theme doom-theme)
    (+doom-dashboard-reload)))

(add-hook 'window-size-change-functions #'set-appropriate-splash)
(add-hook 'doom-load-theme-hook #'set-appropriate-splash)

(provide 'fancy-banner)
;; fancy-banner.el ends here