From 83df7c5a4bed79c53357fd91c393071de1eb60a2 Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Wed, 31 Dec 2025 05:43:46 -0500
Subject: add (hacky and slow) reverse regex search

---
 main.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 80 insertions(+), 19 deletions(-)

(limited to 'main.c')

diff --git a/main.c b/main.c
index 70a25a6..cee28a8 100644
--- a/main.c
+++ b/main.c
@@ -54,7 +54,8 @@ typedef struct {
 	EditMode mode;
 	u32 count;
 	Str input_line, input_prompt;
-	Str last_search;
+	Str search;
+	int search_dir;
 } Editor;
 
 Editor e = { 0 };
@@ -522,8 +523,60 @@ search_from_start:
 	return 0;
 }
 
+int search_prev_regex(TxtLoc start, Str src, TxtLoc *out) {
+	RegEx re = { 0 };
+	ReSearch s = { 0 };
+	if (re_comp_ex(&re, src, &e.scratch, &e.scratch, RE_COMP_NO_GROUPS)) {
+		/* TODO: report parse error */
+		return 0;
+	}
+	int match_found = 0;
+	TxtLoc end = txt_end(start.t);
+	TxtLoc l = start;
+search_from_end:
+	for (;;) {
+		ReMatch m;
+		Arena a = e.scratch;
+		re_search_start(&s, &re, &e.scratch);
+		TxtLoc t = l;
+		while (!at_end(t)) {
+			TxtLoc p = t;
+			Str chnk = txt_next_chunk(&t);
+			re_search_chunk(&s, chnk.s, chnk.n);
+			if (at_end(t)) re_search_last_chunk(&s);
+			if (re_search_match_at_start(&s, &m) && m.extent.start == 0) {
+				*out = (TxtLoc) { p.t, p.p, p.i + m.extent.start };
+				return 1;
+			}
+			if (~s.flags & RE_SEARCH_MID_MATCH) {
+				if (chnk.n > 0) break;
+				if (txt_after(t, end)) break;
+			}
+		}
+		e.scratch = a;
+		if (at_start(l)) break;
+		l = cprev(l);
+	}
+	if (match_found == 0) {
+		match_found = -1;
+		l = txt_end(l.t);
+		end = start;
+		goto search_from_end;
+	}
+	return 0;
+}
+
+int read_search(void) {
+	Str src = get_input_line(S("Search: "));
+	if (!src.n) return 0;
+	e.search.s = malloc(src.n);
+	if (!e.search.s) FAIL_WITH_MSG("failed to allocate search");
+	memcpy(e.search.s, src.s, src.n);
+	e.search.n = src.n;
+	return 1;
+}
+
 int motion(TxtLoc *lp, u32 c) {
-	static Str last_search = { 0 };
 
 	TxtLoc l = *lp;
 	TxtLoc last_loc = l;
@@ -657,25 +710,33 @@ loop:
 		}
 	} break;
 
-	case '/': {
-		if (last_search.s) free(last_search.s);
-		last_search = (Str) { 0, 0 };
-		Str src = get_input_line(S("Search: "));
-		if (!src.n) return 0;
-		last_search.s = malloc(src.n);
-		if (!last_search.s) FAIL_WITH_MSG("failed to allocate search");
-		memcpy(last_search.s, src.s, src.n);
-		last_search.n = src.n;
-		TxtLoc r;
-		if (search_next_regex(l, src, &r)) {
-			l = r;
+	case '/':
+		if (read_search()) {
+			TxtLoc r;
+			if (search_next_regex(l, e.search, &r)) l = r;
+			e.search_dir = 1;
 		}
-	} break;
+		break;
 
-	case 'n': {
-		TxtLoc r;
-		if (last_search.n > 0 && search_next_regex(cnext(l), last_search, &r)) l = r;
-	} break;
+	case '?':
+		if (read_search()) {
+			TxtLoc r;
+			if (search_prev_regex(l, e.search, &r)) l = r;
+			e.search_dir = -1;
+		}
+		break;
+
+	case 'n':
+		if (!e.search.n) return 0;
+		if (e.search_dir > 0 && !search_next_regex(cnext(l), e.search, &l)) return 0;
+		if (e.search_dir < 0 && !search_prev_regex(cprev(l), e.search, &l)) return 0;
+		break;
+
+	case 'N':
+		if (!e.search.n) return 0;
+		if (e.search_dir < 0 && !search_next_regex(cnext(l), e.search, &l)) return 0;
+		if (e.search_dir > 0 && !search_prev_regex(cprev(l), e.search, &l)) return 0;
+		break;
 
 	default:
 		return 0;
-- 
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