;;; ---------------------------------------------------------------------
;;;  SEGLEN-bgol.lsp
;;;  Command:  SGL
;;;
;;;  PURPOSE
;;;  Measures and labels the length of every individual segment of a
;;;  selected polyline in one command. Each length label is rotated to
;;;  align with its segment's direction, producing a clean, readable
;;;  survey-boundary-style annotation without manual per-segment
;;;  dimensioning.
;;;
;;;  USAGE
;;;    1. Load this file (APPLOAD or drag-drop onto the drawing window).
;;;    2. Type   SGL   at the command line and press Enter.
;;;    3. Select the polyline whose segments should be measured.
;;;    4. A length label is placed at the midpoint of every segment,
;;;       rotated to match the segment's angle, on layer "BGOL-SGL".
;;;
;;;  NOTES
;;;    - Text rotation is normalized so labels never appear upside-down
;;;      (angles beyond 90-270 degrees are flipped by 180 degrees).
;;;    - This is an original, independently written implementation.
;;;      It is INSPIRED by the general idea of segment-length labeling
;;;      utilities common in survey/civil drafting workflows, but the
;;;      code, command name and file name here are new and are NOT
;;;      copied from, nor identical to, any specific third-party
;;;      product.
;;;
;;;  ---------------------------------------------------------------------
;;;  Developed and shared for the CAD community by:  BGol Community
;;;  Community website:                              https://bgol.in/
;;;  License:  Open-source & free to use, modify, and share for all.
;;;            Provided "as is", without warranty of any kind.
;;;  ---------------------------------------------------------------------

(vl-load-com)

(defun BGOL:SGL-EnsureLayer (lname / )
  (if (not (tblsearch "LAYER" lname))
    (entmake (list '(0 . "LAYER")
                   '(100 . "AcDbSymbolTableRecord")
                   '(100 . "AcDbLayerTableRecord")
                   (cons 2 lname)
                   '(70 . 0)
                   '(62 . 3)          ; green
                   '(6 . "Continuous")))
  )
)

(defun BGOL:SGL-GetVerts (obj / coords pts)
  (setq coords (vlax-safearray->list (vlax-variant-value (vlax-get obj 'Coordinates))))
  (setq pts '())
  (while coords
    (setq pts (append pts (list (list (car coords) (cadr coords)))))
    (setq coords (cddr coords))
  )
  pts
)

(defun BGOL:SGL-MakeText (pt txt ang ht lname)
  (entmake (list '(0 . "TEXT")
                 '(100 . "AcDbEntity")
                 (cons 8 lname)
                 '(100 . "AcDbText")
                 (cons 10 pt)
                 (cons 40 ht)
                 (cons 1 txt)
                 (cons 50 ang)
                 (cons 72 1)
                 (cons 11 pt)
                 '(100 . "AcDbText")))
)

(defun C:SGL ( / ent obj verts closed n i p1 p2 seglen segang midpt txt cnt)
  (BGOL:SGL-EnsureLayer "BGOL-SGL")
  (setq ent (car (entsel "\nSelect polyline to measure segments: ")))
  (if ent
    (progn
      (setq obj (vlax-ename->vla-object ent))
      (setq closed (vlax-get obj 'Closed))
      (setq verts (BGOL:SGL-GetVerts obj))
      (setq n (length verts))
      (setq cnt 0)
      (setq i 0)
      (while (< i (1- n))
        (setq p1 (nth i verts))
        (setq p2 (nth (1+ i) verts))
        (setq seglen (distance p1 p2))
        (setq segang (angle p1 p2))
        (if (or (> segang (/ pi 2.0)) (< segang (- (/ pi 2.0))))
          (if (and (> segang (/ pi 2.0)) (<= segang (* pi 1.5)))
            (setq segang (- segang pi))
          )
        )
        (setq midpt (list (/ (+ (car p1) (car p2)) 2.0) (/ (+ (cadr p1) (cadr p2)) 2.0)))
        (setq txt (rtos seglen 2 2))
        (BGOL:SGL-MakeText midpt txt segang 2.5 "BGOL-SGL")
        (setq cnt (1+ cnt))
        (setq i (1+ i))
      )
      (if closed
        (progn
          (setq p1 (last verts))
          (setq p2 (car verts))
          (setq seglen (distance p1 p2))
          (setq segang (angle p1 p2))
          (if (and (> segang (/ pi 2.0)) (<= segang (* pi 1.5)))
            (setq segang (- segang pi))
          )
          (setq midpt (list (/ (+ (car p1) (car p2)) 2.0) (/ (+ (cadr p1) (cadr p2)) 2.0)))
          (setq txt (rtos seglen 2 2))
          (BGOL:SGL-MakeText midpt txt segang 2.5 "BGOL-SGL")
          (setq cnt (1+ cnt))
        )
      )
      (princ (strcat "\nSGL: labeled " (itoa cnt) " segment(s) with rotated length text (BGOL-SGL)."))
    )
    (princ "\nNo polyline selected.")
  )
  (princ)
)

(princ "\nSEGLEN-bgol.lsp loaded. Type SGL to label every segment length of a polyline.")
(princ "\n  -- Free & open-source, courtesy of BGol Community (https://bgol.in/) --")
(princ)