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;; the zero Chinese input method framework for emacs.
;; implemented as a minor mode.
;; (load-file "~/lisp/elisp/zero/zero-panel.elc")
;; (load-file "~/lisp/elisp/zero/zero-framework.elc")

;; dependencies

(require 's)
(require 'zero-panel)

;; utils

;; this function is from ibus.el
(defun ibus-compute-pixel-position (&optional pos window)
  "Return geometry of object at POS in WINDOW as a list like \(X Y H).
X and Y are pixel coordinates relative to top left corner of frame which
WINDOW is in. H is the pixel height of the object.

Omitting POS and WINDOW means use current position and selected window,
  (let* ((frame (window-frame (or window (selected-window))))
	 (posn (posn-at-point (or pos (window-point window)) window))
	 (line (cdr (posn-actual-col-row posn)))
	 (line-height (and line
			   (or (window-line-height line window)
			       (and (redisplay t)
				    (window-line-height line window)))))
	 (x-y (or (posn-x-y posn)
		  (let ((geom (pos-visible-in-window-p
			       (or pos (window-point window)) window t)))
		    (and geom (cons (car geom) (cadr geom))))
		  '(0 . 0)))
	 (ax (+ (car (window-inside-pixel-edges window))
		(car x-y)))
	 (ay (+ (cadr (window-pixel-edges window))
		(or (nth 2 line-height) (cdr x-y))))
	 (height (or (car line-height)
		     (with-current-buffer (window-buffer window)
			;; `posn-object-width-height' returns an incorrect value
			;; when the header line is displayed (Emacs bug #4426).
			((and posn
			      (null header-line-format))
			 (cdr (posn-object-width-height posn)))
			((and (bound-and-true-p text-scale-mode)
			      (not (zerop (with-no-warnings
			 (round (* (frame-char-height frame)
				     (expt text-scale-mode-step
			 (frame-char-height frame)))))))
    (list ax ay height)))

(defun zero-get-point-position ()
  "return current point's position (x y) based on origin of screen top left corner"
  (destructuring-bind (x y h) (ibus-compute-pixel-position)
    (list (+ (frame-parameter nil 'left) x)
	  (+ (frame-parameter nil 'top) h y))))

(defun zero-cycle-list (lst item)
  "return the object next to given item in lst, if item is the last object, return the first object in lst.

if item is not in lst, return nil"
  (let ((r (member item lst)))
     ((null r) nil)
     (t (or (cadr r)
	    (car lst))))))

(ert-deftest zero-cycle-list ()
  (should (= (zero-cycle-list '(1 2 3) 1) 2))
  (should (= (zero-cycle-list '(a b c) 'a) 'b))
  (should (= (zero-cycle-list '(a b c) 'b) 'c))
  (should (= (zero-cycle-list '(a b c) 'c) 'a))
  (should (= (zero-cycle-list '(a b c) 'd) nil)))

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;; key logic functions

;; FSM state
(defconst *zero-state-im-off* 'IM-OFF)
(defconst *zero-state-im-waiting-input* 'IM-WAITING-INPUT)
(defconst *zero-state-im-preediting* 'IM-PREEDITING)

(defconst *zero-punctuation-level-basic* 'BASIC)
(defconst *zero-punctuation-level-full* 'FULL)
(defconst *zero-punctuation-level-none* 'NONE)

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;;; concrete input method should define these functions and set them in the
;;; corresponding *-func variable.
(defun zero-build-candidates-default (preedit-str)
(defun zero-can-start-sequence-default (ch)
(defvar zero-build-candidates-func 'zero-build-candidates-default
  "contains a function to build candidates from preedit-str")
(defvar zero-can-start-sequence-func 'zero-can-start-sequence-default
  "contains a function to decide whether a char can start a preedit sequence")
;;; TODO provide hook functions. more complex IM may need to do clean up on these.
;; (defvar zero-on-hook nil)
;; (defvar zero-off-hook nil)

(defvar zero-im nil
  "current input method. if nil, the empty input method will be used.
in the empty input method, only punctuation is handled. Other keys are pass through")
(defvar zero-ims nil
  "a list of registered input methods")

(defvar zero-buffer nil
  "stores the associated buffer.
this is used to help with buffer focus in/out events")

(defvar zero-state *zero-state-im-off*)
(defvar zero-punctuation-level *zero-punctuation-level-basic*
  "punctuation level. should be one of
(defvar zero-punctuation-levels (list *zero-punctuation-level-basic*
  "punctuation levels to use when `zero-cycle-punctuation-level'")
(defvar zero-double-quote-flag nil
  "used when converting double quote to Chinese quote.
if nil, next double quote insert open quote.
otherwise, next double quote insert close quote")
(defvar zero-single-quote-flag nil
  "used when converting single quote to Chinese quote.
if nil, next single quote insert open quote.
otherwise, next single quote insert close quote")
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(defvar zero-preedit-str "")
(defvar zero-candidates nil)

(defvar zero-enable-debug t
  "whether to enable debug.
if t, `zero-debug' will output debug msg in *zero-debug* buffer")

(defun zero-debug (string &rest objects)
  "log debug message in *zero-debug* buffer"
  (if zero-enable-debug
      (with-current-buffer (get-buffer-create "*zero-debug*")
	(insert (apply 'format string objects))
	(goto-char (point-max)))))

;; (zero-debug "msg1\n")
;; (zero-debug "msg2: %s\n" "some obj")
;; (zero-debug "msg3: %s\n" 24)
;; (zero-debug "msg4: %s %s\n" 24 1)

(defun zero-set-state (state)
  "set state to given state"
  (zero-debug "set state to %s\n" state)
  (setq zero-state state))

(defun zero-show-candidates (candidates)
  "show candidates using zero-panel via IPC/RPC"
  (zero-panel-show-candidates zero-preedit-str (length candidates) candidates)
  (zero-debug "candidates: %s\n  " (s-join "\n  " candidates))
  (destructuring-bind (x y) (zero-get-point-position)
    (zero-panel-move x y)))

(defun zero-build-candidates (preedit-str)
  "build candidates list synchronously"
  (if (functionp zero-build-candidates-func)
      (funcall zero-build-candidates-func preedit-str)
    (error "`zero-build-candidates-func' is not a function")))

(defun zero-build-candidates-async (preedit-str)
  "build candidate list, when done show it via `zero-show-candidates'"
  (zero-debug "building candidate list\n")
  (let ((candidates (zero-build-candidates preedit-str)))
    ;; update cache to make SPC and digit key selection possible.
    (setq zero-candidates candidates)
    (zero-show-candidates candidates)))

(defun zero-convert-punctuation-basic (ch)
  "convert punctuation for *zero-punctuation-level-basic*
return ch's Chinese punctuation if ch is converted. return nil otherwise"
  (case ch
    (?, ",")
    (?. "。")
    (?? "?")
    (?! "!")
    (?\\ "、")
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    (otherwise nil)))

(defun zero-convert-punctuation-full (ch)
  "convert punctuation for *zero-punctuation-level-full*
return ch's Chinese punctuation if ch is converted. return nil otherwise"
  (case ch
    (?_ "——")
    (?< "《")
    (?> "》")
    (?\( "(")
    (?\) ")")
    (?\[ "【")
    (?\] "】")
    (?^ "……")
    (?\" (setq zero-double-quote-flag (not zero-double-quote-flag))
	 (if zero-double-quote-flag "“" "”"))
    (?\' (setq zero-single-quote-flag (not zero-single-quote-flag))
	 (if zero-single-quote-flag "‘" "’"))
    (?~ "~")
    (t (zero-convert-punctuation-basic ch))))

(defun zero-convert-punctuation (ch)
  "convert punctuation based on `zero-punctuation-level'
return ch's Chinese punctuation if ch is converted. return nil otherwise"
   ((eq zero-punctuation-level *zero-punctuation-level-basic*)
    (zero-convert-punctuation-basic ch))
   ((eq zero-punctuation-level *zero-punctuation-level-full*)
    (zero-convert-punctuation-full ch))
   (t nil)))

(defun zero-handle-punctuation (ch)
  "if n is a punctuation character, insert mapped Chinese punctuation and return true; otherwise, return false."
  (let ((str (zero-convert-punctuation ch)))
    (when str
      (insert str)

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(defun zero-append-char-to-preedit-str (ch)
  "append char ch to preedit str, update and show candidate list"
  (setq zero-preedit-str
	(concat zero-preedit-str (make-string 1 ch)))
  (zero-debug "appended %c, preedit str is: %s\n" ch zero-preedit-str)

(defun zero-can-start-sequence (ch)
  "return t if char ch can start a preedit sequence."
  (if (functionp zero-can-start-sequence-func)
      (funcall zero-can-start-sequence-func ch)
    (error "`zero-can-start-sequence-func' is not a function")))

(ert-deftest zero-can-start-sequence ()
  (should (zero-can-start-sequence ?a))
  (should (zero-can-start-sequence ?m))
  (should-not (zero-can-start-sequence ?1))
  (should-not (zero-can-start-sequence ?b)))

(defun zero-self-insert-command (n)
  "handle character self-insert-command. This includes characters and digits"
  (interactive "p")
  (let ((ch (elt (this-command-keys-vector) 0)))
    (zero-debug "user typed: %c\n" ch)
     ((eq zero-state *zero-state-im-waiting-input*)
      (if (zero-can-start-sequence ch)
	    (zero-debug "can start sequence, state=IM_PREEDITING\n")
	    (zero-set-state *zero-state-im-preediting*)
	    (zero-append-char-to-preedit-str ch))
	(zero-debug "cannot start sequence, state=IM_WAITING_INPUT\n")
	(unless (zero-handle-punctuation ch)
	  (self-insert-command n))))
     ((eq zero-state *zero-state-im-preediting*)
      (zero-debug "still preediting\n")
       ((and (>= ch ?0) (<= ch ?9))
	;; 1 commit the 0th candidate
	;; 2 commit the 1st candidate
	;; ...
	;; 0 commit the 9th candidate
	(unless (zero-commit-nth-candidate (mod (- (- ch ?0) 1) 10))
	  (zero-append-char-to-preedit-str ch)))
       (t (let ((str (zero-convert-punctuation ch)))
	    (if str
		  (zero-set-state *zero-state-im-waiting-input*)
		  (insert str))
	      (zero-append-char-to-preedit-str ch))))))
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      (zero-debug "unexpected state: %s\n" zero-state)
      (self-insert-command n)))))

(defun zero-preedit-str-changed ()
  "called when preedit str is changed and not empty. update and show candidate list"
  (zero-build-candidates-async zero-preedit-str))

(defun zero-delete-backward-char (n)
  "handle backspace key"
  (interactive "p")
  (unless (integerp n)
    (signal 'wrong-type-argument (list 'integerp n)))
  (if (eq zero-state *zero-state-im-preediting*)
      (let ((len (length zero-preedit-str)))
	(if (> len 1)
	      (setq zero-preedit-str
		    (substring zero-preedit-str 0 (1- len)))
	  (zero-set-state *zero-state-im-waiting-input*)
    (delete-char (- n))))

(defun zero-commit-text (text)
  "commit given text, reset preedit str, hide candidate list"
  (zero-debug "commit text: %s\n" text)
  (insert text)
  (setq zero-preedit-str "")
  (setq zero-candidates nil)

(defun zero-return ()
  "handle RET key press"
  (if (eq zero-state *zero-state-im-preediting*)
	(zero-set-state *zero-state-im-waiting-input*)
	(zero-commit-text zero-preedit-str))

(defun zero-commit-nth-candidate (n)
  "commit nth candidate and return true if it exists, otherwise, return false"
  (let ((candidate (nth n zero-candidates)))
    (if candidate
	  (zero-set-state *zero-state-im-waiting-input*)
	  (zero-commit-text candidate)

(defun zero-commit-preedit-str ()
  (zero-set-state *zero-state-im-waiting-input*)
  (zero-commit-text zero-preedit-str))

(defun zero-commit-first-candidate-or-preedit-str ()
  "commit first candidate if there is one, otherwise commit preedit str"
  (unless (zero-commit-nth-candidate 0)

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(defun zero-space (n)
  "handle SPC key press"
  (interactive "p")
  (if (eq zero-state *zero-state-im-preediting*)
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    (self-insert-command n)))

(defun zero-hide-candidate-list ()
  (zero-debug "hide candidate list\n"))

(defun zero-reset ()
  (zero-debug "reset\n")
  (setq zero-preedit-str "")

(defun zero-focus-in ()
  "a hook function. run when focus in a zero-mode buffer"
  (if (eq zero-state *zero-state-im-preediting*)
      (zero-show-candidates zero-candidates)))

(defun zero-focus-out ()
  "a hook function. run when focus out a zero-mode buffer"
  (if (eq zero-state *zero-state-im-preediting*)

(defun zero-buffer-list-changed ()
  "a hook function, run when buffer list has changed. This includes user has switched buffer"
  (if (eq (car (buffer-list)) zero-buffer)

;; minor mode

;; TODO when zero-framework is stable, move default value to defvar.
;; this will allow user to customize the keymap.
(defvar zero-mode-map nil "zero-mode keymap")
(setq zero-mode-map
	(13 . zero-return)
	(32 . zero-space)
	;; C-.
	(67108910 . zero-cycle-punctuation-level)
	(remap keymap
	       (self-insert-command . zero-self-insert-command)
	       ;; (forward-char . zero-forward-char)
	       ;; (backward-char . zero-backward-char)
	       ;; (forward-word . zero-forward-word)
	       ;; (backward-word . zero-backward-word)
	       (delete-backward-char . zero-delete-backward-char)
	       ;; (delete-char . zero-delete-char)
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(define-minor-mode zero-mode
  "a simple input method written as an emacs minor mode"
  " Zero"
  ;; local variables and variable init
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  (set (make-local-variable 'zero-state) *zero-state-im-off*)
  (make-local-variable 'zero-punctuation-level)
  (make-local-variable 'zero-double-quote-flag)
  (make-local-variable 'zero-single-quote-flag)
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  (set (make-local-variable 'zero-preedit-str) "")
  (set (make-local-variable 'zero-candidates) nil)
  (make-local-variable 'zero-im)
  (make-local-variable 'zero-build-candidates-func)
  (make-local-variable 'zero-can-start-sequence-func)
  (zero-set-im zero-im)
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  (add-hook 'focus-in-hook 'zero-focus-in)
  (add-hook 'focus-out-hook 'zero-focus-out)
  (set (make-local-variable 'zero-buffer) (current-buffer))
  (add-hook 'buffer-list-update-hook 'zero-buffer-list-changed))

;; IM developer API

(defun zero-register-im (im-name im-functions-alist)
  "(re)register an input method in zero. After registration, you can use `zero-set-default-im' and `zero-set-im' to select input method to use.

im-name should be a symbol.
im-functions-alist should be a list of form
  '((:build-candidates . build-candidates-func)
    (:can-start-sequence . can-start-sequence-func))

registered input method is saved in `zero-ims'"
  ;; add or replace entry in `zero-ims'
  (unless (symbolp im-name)
    (signal 'wrong-type-argument (list 'symbolp im-name)))
  (setq zero-ims (assq-delete-all im-name zero-ims))
  (setq zero-ims (push (cons im-name im-functions-alist) zero-ims)))

;; public API

(defun zero-set-punctuation-level (level)
  "set `zero-punctuation-level'"
  (if (not (member level (list *zero-punctuation-level-basic*
      (error "level not supported: %s" level)
    (setq zero-punctuation-level level)))

(defun zero-set-punctuation-levels (levels)
  "set `zero-punctuation-levels'. `zero-cycle-punctuation-level' will cycle current `zero-punctuation-level' among defined levels"
  (dolist (level levels)
    (if (not (member level (list *zero-punctuation-level-basic*
	(error "level not supported: %s" level)))
  (setq zero-punctuation-levels levels))

(defun zero-cycle-punctuation-level ()
  "cycle `zero-punctuation-level' among `zero-punctuation-levels'"
  (setq zero-punctuation-level
	(zero-cycle-list zero-punctuation-levels zero-punctuation-level))
  (message "punctuation level set to %s" zero-punctuation-level))

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(defun zero-set-im (im-name)
  "select zero input method for current buffer.

if im-name is nil, use default empty input method"
  ;; TODO provide completion
  (interactive "SSet input method to: ")
  (if im-name
      (let ((im-functions (cdr (assq im-name zero-ims))))
	(if im-functions
	      (setq zero-build-candidates-func
		    (or (cdr (assq :build-candidates im-functions))
	      (setq zero-can-start-sequence-func
		    (or (cdr (assq :can-start-sequence im-functions))
	      (set (make-local-variable 'zero-im) im-name))
	  (error "input method %s not registered in zero" im-name)))
    (zero-debug "using default empty input method")
    (setq zero-build-candidates-func 'zero-build-candidates-default)
    (setq zero-can-start-sequence-func 'zero-can-start-sequence-default)))

(defun zero-set-default-im (im-name)
  "set given im as default zero input method"
  (unless (symbolp im-name)
    (signal 'wrong-type-argument (list 'symbolp im-name)))
  (setq-default zero-im im-name))

(defun zero-on ()
  (zero-debug "zero-on\n")
  (zero-mode 1)
  (if (eq zero-state *zero-state-im-off*)
      (zero-set-state *zero-state-im-waiting-input*)))

(defun zero-off ()
  (zero-debug "zero-off\n")
  (zero-mode -1)
  (zero-set-state *zero-state-im-off*))

(defun zero-toggle ()
  (if zero-mode

(provide 'zero-framework)