From 3515f1c805cb3a61240d0187fd98530325be55f6 Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Mon, 29 Dec 2025 19:48:19 -0500
Subject: simplify and clarify txt_split_piece(), txt_insert(), txt_delete()

---
 txt.c | 133 +++++++++++++++++++++++++-----------------------------------------
 1 file changed, 50 insertions(+), 83 deletions(-)

(limited to 'txt.c')

diff --git a/txt.c b/txt.c
index b4b4f54..62017c0 100644
--- a/txt.c
+++ b/txt.c
@@ -33,13 +33,35 @@ void txt_remove_piece(Txt *b, u32 pi) {
 	b->ptbl.n--;
 }
 
-u32 txt_split_piece(Txt *b, u32 pi, u32 i) {
-	TxtPiece *p = &b->ptbl.v[pi];
-	if (i == 0) return pi;
-	if (i == p->n) return pi + 1;
-	txt_insert_piece(b, pi + 1, p->buf, p->ofs + i, p->n - i);
-	b->ptbl.v[pi].n = i;
-	return pi + 1;
+TxtLoc txt_split_piece(TxtLoc l) {
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	if (l.i < p->n) {
+		if (l.i == 0 && l.p > 0) {
+			l.p--;
+			l.i = l.t->ptbl.v[l.p].n;
+		} else {
+			txt_insert_piece(l.t, l.p + 1, p->buf, p->ofs + l.i, p->n - l.i);
+			l.t->ptbl.v[l.p].n = l.i;
+		}
+	}
+	ASSERT(l.p < l.t->ptbl.n);
+	ASSERT(l.i == l.t->ptbl.v[l.p].n);
+	return l;
+}
+
+TxtLoc txt_add_piece(TxtLoc l) {
+	l = txt_split_piece(l);
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	if (p->buf != TXT_ADD || p->ofs + p->n != l.t->buf[TXT_ADD].n) {
+		if (l.i > 0) {
+			txt_insert_piece(l.t, l.p + 1, TXT_ADD, l.t->buf[TXT_ADD].n, 0);
+			l.p++;
+			l.i = 0;
+		} else {
+			txt_replace_piece(l.t, l.p, TXT_ADD, l.t->buf[TXT_ADD].n, 0);
+		}
+	}
+	return l;
 }
 
 static void txt_buf_fit(Txt *b, TxtBufIdx bi, u32 sz) {
@@ -67,59 +89,12 @@ static isize txt_buf_dedup(Txt *b, TxtBufIdx bi, const char *s, u32 n) {
 	}
 }
 
-TxtLoc txt_add_piece(Txt *b, TxtLoc l) {
-	if (l.p > 0 && !l.i) {
-		l.p--;
-		l.i = b->ptbl.v[l.p].n;
-	}
-	if (l.p < b->ptbl.n) {
-		TxtPiece *p = &b->ptbl.v[l.p];
-		int mid = p->ofs + l.i < b->buf[p->buf].n;
-		if (p->buf == TXT_SRC || mid) {
-			l.p = txt_split_piece(b, l.p, l.i);
-			goto insert;
-		}
-	} else {
-insert:
-		if (l.p < b->ptbl.n && b->ptbl.v[l.p].n == 0) {
-			txt_replace_piece(b, l.p, TXT_ADD, b->buf[TXT_ADD].n, 0);
-		} else {
-			txt_insert_piece(b, l.p, TXT_ADD, b->buf[TXT_ADD].n, 0);
-		}
-	}
-	return l;
-}
-
 static int txt_are_pieces_adjacent(Txt *t, u32 a, u32 b) {
 	TxtPiece *pa = &t->ptbl.v[a];
 	TxtPiece *pb = &t->ptbl.v[b];
 	return pa->buf == pb->buf && pa->ofs + pa->n == pb->ofs;
 }
 
-static int txt_trim_empty(TxtLoc *lp) {
-	TxtLoc l = *lp;
-	int deleted = 0;
-	while (l.p > 0 && l.t->ptbl.v[l.p-1].n == 0) {
-		txt_remove_piece(l.t, l.p - 1);
-		l.p--;
-		deleted = 1;
-	}
-	while (l.p + 1 < l.t->ptbl.n && l.t->ptbl.v[l.p+1].n == 0) {
-		txt_remove_piece(l.t, l.p + 1);
-		deleted = 1;
-	}
-	while (l.t->ptbl.n > 1 && l.t->ptbl.v[l.p].n == 0) {
-		txt_remove_piece(l.t, l.p);
-		if (l.p >= l.t->ptbl.n) {
-			l.p = l.t->ptbl.n - 1;
-			l.i = l.t->ptbl.v[l.p].n;
-		}
-		deleted = 1;
-	}
-	*lp = l;
-	return deleted;
-}
-
 static inline TxtLoc resolve_loc(TxtLoc l) {
 	while (l.p + 1 < l.t->ptbl.n && l.i == l.t->ptbl.v[l.p].n) {
 		l.p++;
@@ -132,10 +107,6 @@ static inline TxtLoc resolve_loc(TxtLoc l) {
 static TxtLoc txt_post_edit(TxtLoc l) {
 	l = resolve_loc(l);
 loop:
-	if (txt_trim_empty(&l)) {
-		ASSERT(txt_valid_loc(l));
-		goto loop;
-	}
 	if (l.p > 0 && txt_are_pieces_adjacent(l.t, l.p - 1, l.p)) {
 		l.i = l.t->ptbl.v[l.p - 1].n;
 		l.t->ptbl.v[l.p - 1].n += l.t->ptbl.v[l.p].n;
@@ -155,7 +126,7 @@ loop:
 }
 
 TxtLoc txt_insert(TxtLoc l, const char *s, u32 n) {
-	l = txt_add_piece(l.t, l);
+	l = txt_add_piece(l);
 	TxtPiece *p = &l.t->ptbl.v[l.p];
 	isize ext = txt_buf_dedup(l.t, p->buf, s, n);
 	if (p->n > 0 || ext == -1) {
@@ -169,37 +140,31 @@ TxtLoc txt_insert(TxtLoc l, const char *s, u32 n) {
 	return txt_post_edit(l);
 }
 
-TxtLoc txt_insert_c(TxtLoc l, u32 ch) {
-	char buf[6];
-	u32 n = utf8_encode_len(&ch, 1);
-	utf8_encode(buf, &ch, 1);
-	return txt_insert(l, buf, n);
-}
-
 TxtLoc txt_delete(TxtLoc l, u32 n) {
-	u32 pi = txt_split_piece(l.t, l.p, l.i);
-	if (pi > 0) pi--;
-	l.p = pi;
-	l.i = l.t->ptbl.v[l.p].n;
-	for (;;) {
-		if (l.i != l.t->ptbl.v[l.p].n) break;
-		if (l.i >= n) {
-			l.i -= n;
-			l.t->ptbl.v[l.p].n -= n;
-			break;
-		} else {
-			l.t->ptbl.v[l.p].n -= l.i;
-			n -= l.i;
-			l.i = 0;
-			if (l.p == 0) break;
-			l.p = l.p - 1;
+	l = txt_split_piece(l);
+	while (n > 0) {
+		TxtPiece *p = &l.t->ptbl.v[l.p];
+		u32 sz = p->n > n ? n : p->n;
+		p->n -= sz;
+		l.i -= sz;
+		n -= sz;
+		if (!p->n && l.t->ptbl.n > 1) txt_remove_piece(l.t, l.p);
+		if (l.p == 0) break;
+		if (l.i == 0) {
+			l.p--;
 			l.i = l.t->ptbl.v[l.p].n;
 		}
-		while (txt_trim_empty(&l));
 	}
 	return txt_post_edit(l);
 }
 
+TxtLoc txt_insert_c(TxtLoc l, u32 ch) {
+	char buf[6];
+	u32 n = utf8_encode_len(&ch, 1);
+	utf8_encode(buf, &ch, 1);
+	return txt_insert(l, buf, n);
+}
+
 u32 txt_range_len(TxtLoc lo, TxtLoc hi) {
 	u32 n = 0;
 	while (lo.p < hi.p) {
@@ -438,6 +403,8 @@ int at_end(TxtLoc l) {
 	return l.p + 1 == l.t->ptbl.n && l.i == l.t->ptbl.v[l.p].n;
 }
 
+/* TODO: make these use memchr() or equivalent */
+
 TxtLoc next_newline(TxtLoc l) {
 	do l = cnext(l);
 	while (!at_end(l) && txt_byte(l) != '\n');
-- 
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