par: piece-table: add line accessor function

3 files changed, 41 insertions, 5 deletions

diff --git a/par/piece-table.scm b/par/piece-table.scm
index 0191a1c..24608e3 100644
--- a/par/piece-table.scm
+++ b/par/piece-table.scm
@@ -185,16 +185,30 @@
 (define (piece-table-text-length piece-table)
   (reduce + 0 (map piece-length (piece-table-pieces piece-table))))
 
+(define (piece-table-find-line-break piece-table idx)
+  (let loop ((idx 0)
+             (ps (piece-table-pieces piece-table))
+             (rem idx))
+     (let* ((current (car ps))
+            (len     (piece-length current))
+            (lines   (piece-linebreaks current))
+            (lc      (vector-length lines)))
+        (cond
+          ((< rem lc)         (+ idx (vector-ref lines rem)))
+          ((null? (cdr ps))   (eof-object)) ;; TODO: No more pieces, return the end or eof?
+          (else               (loop (+ idx len) (cdr ps) (- rem lc)))))))
+
 (define (piece-table-text-pos->piece-idx+remainder piece-table pos)
-  "Returns (values piece remainder)"
+  "Returns (values piece remainder) or eof-object"
   (let loop ((idx 0)
              (ps (piece-table-pieces piece-table))
              (rem pos))
      (let* ((current (car ps))
             (len     (piece-length current)))
-      (if (<= rem len)
-        (values idx rem)
-        (loop (+ idx 1) (cdr ps) (- rem len))))))
+       (cond
+         ((<= rem len)       (values idx rem))
+         ((null? (cdr ps))   (eof-object)) ;; TODO: No more pieces, return the end or eof?
+         (else               (loop (+ idx 1) (cdr ps) (- rem len)))))))
 
 (define (list-ref-with-context l i)
   (let ((len (length l)))
@@ -282,3 +296,16 @@
 
 (define (piece-table->string piece-table)
   (piece-table-substring piece-table 0 (piece-table-text-length piece-table)))
+
+;; Interact with lines: interesting for the UI
+(define (piece-table-line piece-table line-number)
+  (let ((start (if (= line-number 0) 0
+                 (+ 1 (piece-table-find-line-break piece-table
+                                                   (- line-number 1)))))
+        (end   (piece-table-find-line-break piece-table line-number)))
+    (cond
+      ((eof-object? start)   start)
+      ((eof-object? end)     (piece-table-substring
+                               piece-table start
+                               (piece-table-text-length piece-table)))
+      (else (piece-table-substring piece-table start end)))))
diff --git a/par/piece-table.sld b/par/piece-table.sld
index 4650cb7..f867612 100644
--- a/par/piece-table.sld
+++ b/par/piece-table.sld
@@ -9,5 +9,6 @@
           piece-table->string
           piece-table-substring
           string->piece-table
-          add-buffer-length)
+          add-buffer-length
+          piece-table-line)
   (include "piece-table.scm"))
diff --git a/tests/piece-table.scm b/tests/piece-table.scm
index 317286c..19bd107 100644
--- a/tests/piece-table.scm
+++ b/tests/piece-table.scm
@@ -30,6 +30,14 @@
     (test-equal  "6X78" (piece-table-substring table 5 9)))
 (test-end "substring")
 
+(test-begin "insert-newlines")
+  (parameterize ((add-buffer-length 10))
+    (define table (make-piece-table "HOLA\nADIOS"))
+    (piece-table-insert! table 4 "\nHABLAMOS" 'normal)
+    (test-equal "HOLA\nHABLAMOS\nADIOS" (piece-table->string table))
+    (test-equal (piece-table-line table 1) "HABLAMOS"))
+(test-end "insert-newlines")
+
 (test-begin "delete")
   (define table (make-piece-table "HOLA SOY EKAITZ"))
   (piece-table-delete! table 4 1)