From 26892394d6999fca9be6975b0910158fdf8a9fff Mon Sep 17 00:00:00 2001
From: Ekaitz Zarraga <ekaitz@elenq.tech>
Date: Tue, 23 Jan 2024 15:29:23 +0100
Subject: par: piece-table: add for-each

---
 par/piece-table.scm   | 29 +++++++++++++++++++++++++++++
 par/piece-table.sld   |  3 ++-
 tests/piece-table.scm | 13 +++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/par/piece-table.scm b/par/piece-table.scm
index 24608e3..21661e7 100644
--- a/par/piece-table.scm
+++ b/par/piece-table.scm
@@ -185,6 +185,35 @@
 (define (piece-table-text-length piece-table)
   (reduce + 0 (map piece-length (piece-table-pieces piece-table))))
 
+(define (piece-table-for-each piece-table f from to)
+  ;; TODO: default from and to
+  "Calls `f` through the characters of the piece-table, like `string-for-each`
+  would do, but the `f` call also includes the piece (to expose extra data) and
+  the index of the character"
+  (let loop ((idx   0)
+             (start 0)
+             (pieces (piece-table-pieces piece-table)))
+    (let* ((piece (car pieces))
+           (len   (piece-length piece))
+           (end   (+ start len))
+           (more? (not (null? (cdr pieces)))))
+      (when (< idx to) ;; Skip tail
+        (if (or (= idx end) (<= end from))
+          ;; Current piece doesn't contain the section we need or finished
+          ;; Jump to next piece
+          (when more? (loop end end (cdr pieces)))
+          ;; Current piece contains part of the section we need, go char by
+          ;; char
+          (begin
+            (when (<= from idx)
+              (f
+                (string-ref (buffer->string (piece-buffer piece))
+                            (+ (piece-start piece) (- idx start)))
+                idx
+                piece))
+            ;; There are chars to process in this piece
+            (loop (+ idx 1) start pieces)))))))
+
 (define (piece-table-find-line-break piece-table idx)
   (let loop ((idx 0)
              (ps (piece-table-pieces piece-table))
diff --git a/par/piece-table.sld b/par/piece-table.sld
index f867612..427b389 100644
--- a/par/piece-table.sld
+++ b/par/piece-table.sld
@@ -10,5 +10,6 @@
           piece-table-substring
           string->piece-table
           add-buffer-length
-          piece-table-line)
+          piece-table-line
+          piece-table-for-each)
   (include "piece-table.scm"))
diff --git a/tests/piece-table.scm b/tests/piece-table.scm
index 19bd107..453229e 100644
--- a/tests/piece-table.scm
+++ b/tests/piece-table.scm
@@ -47,3 +47,16 @@
   (piece-table-delete! table 12 1)
   (test-equal "OLASOY EKAIT" (piece-table->string table))
 (test-end "delete")
+
+(test-begin "for-each")
+  (define table (make-piece-table "12346890"))
+  (piece-table-insert! table 4 "5" 'normal)
+  (test-equal "123456890" (piece-table->string table))
+  (piece-table-insert! table 6 "7" 'normal)
+  (test-equal "1234567890" (piece-table->string table))
+  (piece-table-for-each table
+                        (lambda (c i p)
+                          (test-equal c (string-ref "1234567890" i)))
+                        0
+                        10)
+(test-end)
-- 
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