From 1692a9fc05e040ffa1333d12fd812e37bda36864 Mon Sep 17 00:00:00 2001
From: Vivianne Langdon <puttabutta@gmail.com>
Date: Sun, 3 Mar 2024 14:20:02 -0500
Subject: [PATCH] first pass untested state machine

---
 uniseg/graphemes/stream.scm | 100 ++++++++++++++++++++++++++++++++++--
 1 file changed, 97 insertions(+), 3 deletions(-)

diff --git a/uniseg/graphemes/stream.scm b/uniseg/graphemes/stream.scm
index 511d109..b17956c 100644
--- a/uniseg/graphemes/stream.scm
+++ b/uniseg/graphemes/stream.scm
@@ -1,8 +1,13 @@
 (define-module (runewidth graphemes stream)
+  #:use-module (ice-9 match)
   #:use-module (srfi srfi-41)
   #:use-module (srfi srfi-9 gnu)
   #:export (make-grapheme
-
+            grapheme?
+            grapheme-glyphs
+            grapheme-width
+            grapheme-sentence-end?
+            grapheme-word-end?
             input->grapheme-stream))
 
 (define-immutable-record-type <grapheme>
@@ -17,6 +22,95 @@
   (unless port
     (set! port (current-input-port)))
 
-  (define gr (make-grapheme glyphs width sentence-end? word-end?))
+  ;; The first is what state we are in, and the next is the grapheme
+  ;; property of the current character.
+  ;; Port of https://github.com/rivo/uniseg/blob/master/graphemerules.go
+  (define (state-machine cur-state cur-prop)
+    (match (list cur-state cur-prop)
+      ;; Grapheme boundary #3
+      (('carriage-return 'line-feed)
+       (values 'control+line-feed 'no-boundary))
 
-  (stream-cons c (input->grapheme-stream port)))
+      ;; Grapheme boundary #4
+      ((or ('carriage-return _)
+           ('control+line-feed _))
+       (values 'any 'boundary))
+
+      ;; Grapheme boundary #5
+      ((_ 'carriage-return)
+       (values 'carriage-return 'boundary))
+      ((or (_ 'line-feed)
+           (_ 'control))
+       (values 'control+line-feed 'boundary))
+
+      ;; Grapheme boundary #6
+      (('hangul-syllable-l 'hangul-syllable-l)
+       (values 'hangul-syllable-l 'no-boundary))
+      ((or ('hangul-syllable-l 'hangul-syllable-v)
+           ('hangul-syllable-l 'hangul-syllable-lv))
+       (values 'hangul-syllable-lv 'no-boundary))
+      (('hangul-syllable-l 'hangul-syllable-lvt)
+       (values 'hangul-syllable-lvt 'no-boundary))
+      ((_ 'hangul-syllable-l)
+       (values 'hangul-syllable-l 'boundary))
+
+      ;; Grapheme boundary #7
+      (('hangul-syllable-lv 'hangul-syllable-v)
+       (values 'hangul-syllable-lv 'no-boundary))
+      (('hangul-syllable-lv 'hangul-syllable-t)
+       (values 'hangul-syllable-lvt 'no-boundary))
+      ((or (_ 'hangul-syllable-lv)
+           (_ 'hangul-syllable-v))
+       (values 'hangul-syllable-lv 'boundary))
+
+      ;; Grapheme boundary #8
+      ((or (_ 'hangul-syllable-lvt)
+           (_ 'hangul-syllable-t))
+       (values 'hangul-syllable-lvt 'boundary))
+      (('hangul-syllable-lvt 'hangul-syllable-t)
+       (values 'hangul-syllable-lvt 'no-boundary))
+
+      ;; Grapheme boundary #9
+      ((or (_ 'extend)
+           (_ 'zero-width-joiner))
+       (values 'any 'no-boundary))
+
+      ;; Grapheme boundary #9a
+      ((_ 'spacing-mark)
+       (values 'any 'no-boundary))
+
+      ;; Grapheme boundary #9b
+      (('prepend _)
+       (values 'any 'no-boundary))
+      ((_ 'prepend)
+       (values 'prepend 'boundary))
+
+      ;; Grapheme boundary #11 (emoji!)
+      (('extended-pictographic 'extend)
+       (values 'extended-pictographic 'no-boundary))
+      (('extended-pictographic 'zero-width-joiner)
+       (values 'extended-pictographic+zero-width-joiner 'no-boundary))
+      (('extended-pictographic+zero-width-joiner 'extended-pictographic)
+       (values 'extended-pictographic 'no-boundary))
+      ((_ 'extended-pictographic)
+       (values 'extended-pictographic 'boundary))
+
+
+      ;; Grapheme boundaries #12 and #13
+      (('regional-indicator-odd 'regional-indicator)
+       (values 'regioinal-indicator-even 'no-boundary))
+      (('regional-indicator-even 'regional-indicator)
+       (values 'regional-indicator-odd 'boundary))
+      ((_ 'regional-indicator)
+       (values 'regional-indicator-odd 'boundary))
+
+      (else (values 'other 'other))))
+
+  (define (transition-state state char)
+    "Given the current state and the next char, run a state transition"
+
+
+    )
+
+  (define grapheme (make-grapheme glyphs width sentence-end? word-end?))
+  (stream-cons grapheme (input->grapheme-stream port)))