;;; wrap-org-table.el --- reflow org tables to the width standard  -*- lexical-binding: t; -*-
;;
;; Reformats org tables to the org-table standard (claude-rules/org-tables.md):
;;
;;   1. Max 120 columns wide, measured at RENDER width — an org link counts as
;;      its visible label, not its [[target][label]] source. Links are never
;;      split to chase a source-width number.
;;   2. Cells that would push a row past the budget wrap onto continuation
;;      rows (the other columns left blank).
;;   3. A horizontal rule under the header and under every logical data row,
;;      closing rule included.
;;
;; Usage:
;;   emacs --batch -q -l wrap-org-table.el [--width=120] FILE.org [FILE.org ...]
;;     reformat every table in each file, in place. A backup of each file is
;;     copied to /tmp/<basename>.before-table-wrap.<YYYYMMDD-HHMMSS> first.
;;
;; As a library: (wot-reformat-table-string STRING &optional BUDGET) is the
;; pure core; (wot-process-file FILE &optional BUDGET) is the file layer.
;;
;; Column widths: each column starts at its natural width (the widest cell it
;; holds, render-measured). When the row total exceeds the budget, the widest
;; columns shrink first, never below the column's floor — its longest atomic
;; token (a word, or a whole link) — because going lower would force a
;; mid-word or mid-link split. A table whose floors alone exceed the budget is
;; reflowed to the floors (best effort): the source stays over budget and the
;; lint check keeps flagging it for a human to restructure (merge or drop
;; columns — a judgment call this helper doesn't make).

(require 'cl-lib)
(require 'subr-x)

(defconst wot-default-budget 120
  "Default table width budget in render columns, pipes included.")

;;; ---------------------------------------------------------------------------
;;; pure core

(defun wot-render-width (s)
  "Render width of cell text S: org links count as their visible label.
A descriptive link [[target][label]] measures as its label; a bare [[target]]
measures as the target text. Everything else is literal."
  (let ((rendered (replace-regexp-in-string
                   "\\[\\[\\([^][]*\\)\\]\\(?:\\[\\([^][]*\\)\\]\\)?\\]"
                   (lambda (m)
                     (save-match-data
                       (if (string-match
                            "\\[\\[\\([^][]*\\)\\]\\[\\([^][]*\\)\\]\\]" m)
                           (match-string 2 m)
                         (string-match "\\[\\[\\([^][]*\\)\\]\\]" m)
                         (match-string 1 m))))
                   s t t)))
    (length rendered)))

(defun wot-tokenize (s)
  "Split cell text S into tokens; org links are atomic tokens."
  (let ((tokens nil)
        (pos 0)
        (link-re "\\[\\[[^][]*\\]\\(?:\\[[^][]*\\]\\)?\\]"))
    (while (string-match link-re s pos)
      ;; Capture the bounds first: split-string below runs its own matches
      ;; and clobbers the global match data.
      (let ((mb (match-beginning 0))
            (me (match-end 0)))
        (dolist (w (split-string (substring s pos mb) nil t)) (push w tokens))
        (push (substring s mb me) tokens)
        (setq pos me)))
    (dolist (w (split-string (substring s pos) nil t)) (push w tokens))
    (nreverse tokens)))

(defun wot-wrap-cell (s width)
  "Greedy-wrap cell text S into lines of at most WIDTH render columns.
Tokens (words and whole links) are never split; a token wider than WIDTH sits
alone on its own over-width line."
  (let ((tokens (wot-tokenize s))
        (lines nil)
        (current ""))
    (dolist (tok tokens)
      (cond
       ((string-empty-p current)
        (setq current tok))
       ((<= (+ (wot-render-width current) 1 (wot-render-width tok)) width)
        (setq current (concat current " " tok)))
       (t
        (push current lines)
        (setq current tok))))
    (push current lines)
    (nreverse lines)))

(defun wot--column-floor (cells)
  "Floor width for a column holding CELLS: its widest atomic token."
  (let ((floor 1))
    (dolist (cell cells)
      (dolist (tok (wot-tokenize cell))
        (setq floor (max floor (wot-render-width tok)))))
    floor))

(defun wot-allocate-widths (rows budget)
  "Column widths for ROWS (lists of cell strings) under BUDGET total width.
Row overhead is `| ' + ` | ' separators + ` |', i.e. 3*ncols + 1. Columns
start at natural width; the widest shrink first, never below their floor."
  (let* ((ncols (apply #'max (mapcar #'length rows)))
         (cols (cl-loop for i below ncols
                        collect (mapcar (lambda (r) (or (nth i r) "")) rows)))
         (widths (mapcar (lambda (col)
                           (apply #'max 1 (mapcar #'wot-render-width col)))
                         cols))
         (floors (mapcar #'wot--column-floor cols))
         (cell-budget (- budget (+ (* 3 ncols) 1))))
    (cl-loop while (> (apply #'+ widths) cell-budget)
             for idx = (cl-loop with best = nil with best-w = -1
                                for i below ncols
                                when (and (> (nth i widths) (nth i floors))
                                          (> (nth i widths) best-w))
                                do (setq best i best-w (nth i widths))
                                finally return best)
             while idx
             do (setf (nth idx widths) (1- (nth idx widths))))
    widths))

(defun wot--pad (cell width)
  "Pad CELL source text with spaces so its render width is at least WIDTH."
  (concat cell (make-string (max 0 (- width (wot-render-width cell))) ?\s)))

(defun wot--hline (widths indent)
  (concat indent "|"
          (mapconcat (lambda (w) (make-string (+ w 2) ?-)) widths "+")
          "|"))

(defun wot--emit-row (cells widths indent)
  "Physical lines for one logical row: CELLS wrapped to WIDTHS, link-safe."
  (let* ((wrapped (cl-loop for i below (length widths)
                           collect (wot-wrap-cell (or (nth i cells) "")
                                                  (nth i widths))))
         (height (apply #'max (mapcar #'length wrapped))))
    (cl-loop for line below height
             collect (concat indent "| "
                             (mapconcat
                              (lambda (i)
                                (wot--pad (or (nth line (nth i wrapped)) "")
                                          (nth i widths)))
                              (number-sequence 0 (1- (length widths)))
                              " | ")
                             " |"))))

(defun wot--parse-row (line)
  "Cell strings of table LINE, or the symbol `hline'."
  (let ((trimmed (string-trim line)))
    (if (string-prefix-p "|-" trimmed)
        'hline
      (mapcar #'string-trim
              (split-string (string-remove-suffix "|"
                             (string-remove-prefix "|" trimmed))
                            "|")))))

(defun wot--merge-group (group)
  "Merge GROUP (a list of cell-lists) into one logical row.
Each column's non-empty values join with a space — the inverse of the
continuation-row split `wot--emit-row' produces."
  (let ((ncols (apply #'max (mapcar #'length group))))
    (cl-loop for i below ncols
             collect (string-join
                      (cl-remove-if #'string-empty-p
                                    (mapcar (lambda (r) (or (nth i r) ""))
                                            group))
                      " "))))

(defun wot--continuation-group-p (group)
  "Non-nil when GROUP's lines after the first read as continuation rows.
A continuation row carries overflow text in some columns and leaves the rest
empty, so every line past the first must have at least one empty cell. A
group of fully-populated lines is distinct rows that merely share a rule."
  (and (> (length group) 1)
       (cl-every (lambda (r) (cl-some #'string-empty-p r))
                 (cdr group))))

(defun wot--logical-rows (elems)
  "Logical rows from ELEMS, a list of cell-lists and `hline' symbols.
With no hlines, every line is its own row. With hlines, lines group between
rules; a group whose trailing lines look like continuations (each has an
empty cell) merges into one logical row — that makes re-running on
already-conformant output a no-op — while fully-populated groups keep their
line-per-row meaning."
  (if (not (memq 'hline elems))
      elems
    (let ((groups nil) (current nil))
      (dolist (e elems)
        (if (eq e 'hline)
            (when current
              (push (nreverse current) groups)
              (setq current nil))
          (push e current)))
      (when current (push (nreverse current) groups))
      (cl-loop for g in (nreverse groups)
               if (wot--continuation-group-p g)
               collect (wot--merge-group g)
               else append g))))

(defun wot-reformat-table-string (table-string &optional budget)
  "Reformat TABLE-STRING to the org-table standard at BUDGET width.
Wraps over-budget cells onto continuation rows, puts a rule under the header
and under every logical data row, and preserves the table's indentation.
Re-running on already-conformant output is a no-op: rule-delimited
continuation lines merge back into their logical row before re-wrapping."
  (let* ((budget (or budget wot-default-budget))
         (lines (split-string (string-remove-suffix "\n" table-string) "\n"))
         (indent (if (string-match "^[ \t]*" (car lines))
                     (match-string 0 (car lines))
                   ""))
         (parsed (mapcar #'wot--parse-row lines))
         ;; Header = first row when the source separates it with an hline.
         (header-p (and (listp (car parsed)) (eq (cadr parsed) 'hline)))
         (header (and header-p (car parsed)))
         (data-elems (if header-p (cddr parsed) parsed))
         (rows (wot--logical-rows data-elems))
         (widths (wot-allocate-widths (if header (cons header rows) rows)
                                      budget))
         (out nil))
    (when header
      (dolist (l (wot--emit-row header widths indent)) (push l out))
      (push (wot--hline widths indent) out))
    (dolist (row rows)
      (dolist (l (wot--emit-row row widths indent)) (push l out))
      (push (wot--hline widths indent) out))
    (concat (string-join (nreverse out) "\n") "\n")))

;;; ---------------------------------------------------------------------------
;;; file layer

(defun wot-process-file (file &optional budget)
  "Reformat every org table in FILE in place to BUDGET width."
  (with-temp-buffer
    (insert-file-contents file)
    (goto-char (point-min))
    (while (re-search-forward "^[ \t]*|" nil t)
      (let ((start (line-beginning-position)))
        (while (and (not (eobp))
                    (save-excursion (beginning-of-line)
                                    (looking-at "[ \t]*|")))
          (forward-line 1))
        (let* ((end (point))
               (table (buffer-substring-no-properties start end))
               (reformatted (wot-reformat-table-string table budget)))
          (delete-region start end)
          (goto-char start)
          (insert reformatted))))
    (write-region (point-min) (point-max) file)))

;;; ---------------------------------------------------------------------------
;;; CLI

(defun wot--backup (file)
  (copy-file file
             (format "/tmp/%s.before-table-wrap.%s"
                     (file-name-nondirectory file)
                     (format-time-string "%Y%m%d-%H%M%S"))
             t))

(defun wot-main ()
  (let ((budget wot-default-budget)
        (width-arg (cl-find-if (lambda (a) (string-prefix-p "--width=" a))
                               command-line-args-left)))
    (when width-arg
      (setq budget (string-to-number (substring width-arg (length "--width="))))
      (setq command-line-args-left (delete width-arg command-line-args-left)))
    (if (null command-line-args-left)
        (progn
          (princ "Usage: emacs --batch -q -l wrap-org-table.el [--width=120] FILE.org ...\n")
          (kill-emacs 1))
      (let ((files command-line-args-left))
        (setq command-line-args-left nil)
        (dolist (file files)
          (if (file-readable-p file)
              (progn
                (wot--backup file)
                (wot-process-file file budget)
                (princ (format ";; wrap-org-table: file=%s reformatted (budget %d)\n"
                               file budget)))
            (princ (format ";; wrap-org-table: file=%s not readable — skipping\n"
                           file))))))))

(defun wot--cli-invocation-p ()
  "Non-nil when the trailing args look like a real invocation (flags + files),
so the ERT suite can `require' this file without firing the CLI dispatch."
  (and command-line-args-left
       (cl-every (lambda (a)
                   (cond ((string-prefix-p "--width=" a) t)
                         ((string-prefix-p "-" a) nil)
                         (t (file-readable-p a))))
                 command-line-args-left)))

(when (and noninteractive (wot--cli-invocation-p))
  (wot-main))

(provide 'wrap-org-table)
;;; wrap-org-table.el ends here