From 6fbc0be40c38734f33c728ce70c609c6308ba354 Mon Sep 17 00:00:00 2001
From: Jason Evans <jasone@canonware.com>
Date: Sun, 16 Aug 2020 17:39:32 -0700
Subject: [PATCH] XXX Implement Text.Cursor.next_opt .

---
 bootstrap/src/basis/text.ml | 39 ++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/bootstrap/src/basis/text.ml b/bootstrap/src/basis/text.ml
index ec5151f70..7be9d7474 100644
--- a/bootstrap/src/basis/text.ml
+++ b/bootstrap/src/basis/text.ml
@@ -18,12 +18,10 @@ module Pos = struct
     let init ~line ~col =
       {line; col}
 
-(*
     let succ cp t =
       match cp with
       | cp when Codepoint.(cp = nl) -> {line=Uns.succ t.line; col=0}
       | _ -> {t with col=Uns.succ t.col}
-*)
 
     let line t =
       t.line
@@ -52,6 +50,13 @@ module Apos = struct
     let init ~bindex ~cindex ~pos =
       {bindex; cindex; pos}
 
+    let succ cp t =
+      {
+        bindex=Codepoint.Utf8.(length (of_codepoint cp));
+        cindex=Uns.succ t.cindex;
+        pos=Pos.succ cp t.pos;
+      }
+
     let bindex t =
       t.bindex
 
@@ -102,10 +107,8 @@ module Excerpt = struct
     let apos t =
       t.apos
 
-(*XXX
     let string t =
       t.string
-*)
   end
   include T
 (* XXX Remove?
@@ -198,11 +201,6 @@ module Cursor = struct
     let container t =
       t.text
 
-(*XXX
-    let apos t =
-      t.apos
-*)
-
     let pos t =
       Apos.pos t.apos
 
@@ -224,8 +222,27 @@ module Cursor = struct
       end in
       fn (force text)
 
-    let next_opt _t =
-      None (* XXX *)
+    let rec next_opt t =
+      match String.Cursor.(
+        t.scursor < String.Cursor.tl (String.Cursor.container t.scursor)) with
+      | true -> begin
+          let cp, scursor' = String.Cursor.next t.scursor in
+          let apos' = Apos.succ cp t.apos in
+          Some (cp, {t with apos=apos'; scursor=scursor'})
+        end
+      | false -> begin
+          match Ordset.Cursor.(t.ecursor < tl t.text.excerpts) with
+          | true -> begin
+              let excerpt', ecursor' = Ordset.Cursor.next t.ecursor in
+              let scursor' = String.Cursor.hd (Excerpt.string excerpt') in
+              next_opt {t with ecursor=ecursor'; scursor=scursor'}
+            end
+          | false -> begin
+              match Lazy.force (t.text.extend) with
+              | None -> None
+              | Some text' -> next_opt {t with text=text'}
+            end
+        end
 
     let rget_opt t =
       match next_opt t with