string and peg replacement functions can now take functions

Functions will be invoked with the matched text, and their result will be
coerced to a string and used as the new replacement text.

This also allows passing non-function, non-byteviewable values, which will be
converted into strings during replacement (only once, and only if at least
one match is found).

src/core/peg.c

@@ -1637,7 +1637,7 @@ typedef struct {
     JanetPeg *peg;
     PegState s;
     JanetByteView bytes;
-    JanetByteView repl;
+    Janet subst;
     int32_t start;
 } PegCall;
 
@@ -1653,7 +1653,7 @@ static PegCall peg_cfun_init(int32_t argc, Janet *argv, int get_replace) {
         ret.peg = compile_peg(argv[0]);
     }
     if (get_replace) {
-        ret.repl = janet_getbytes(argv, 1);
+        ret.subst = argv[1];
         ret.bytes = janet_getbytes(argv, 2);
     } else {
         ret.bytes = janet_getbytes(argv, 1);
@@ -1738,7 +1738,8 @@ static Janet cfun_peg_replace_generic(int32_t argc, Janet *argv, int only_one) {
                 trail = i;
             }
             int32_t nexti = (int32_t)(result - c.bytes.bytes);
-            janet_buffer_push_bytes(ret, c.repl.bytes, c.repl.len);
+            JanetByteView subst = janet_text_substitution(&c.subst, c.bytes.bytes + i, nexti - i);
+            janet_buffer_push_bytes(ret, subst.bytes, subst.len);
             trail = nexti;
             if (nexti == i) nexti++;
             i = nexti;
@@ -1754,14 +1755,20 @@ static Janet cfun_peg_replace_generic(int32_t argc, Janet *argv, int only_one) {
 }
 
 JANET_CORE_FN(cfun_peg_replace_all,
-              "(peg/replace-all peg repl text &opt start & args)",
-              "Replace all matches of peg in text with repl, returning a new buffer. The peg does not need to make captures to do replacement.") {
+              "(peg/replace-all peg subst text &opt start & args)",
+              "Replace all matches of `peg` in `text` with `subst`, returning a new buffer. "
+              "The peg does not need to make captures to do replacement. "
+              "If `subst` is a function, it will be called once for each match "
+              "and should return the actual replacement text to use.") {
     return cfun_peg_replace_generic(argc, argv, 0);
 }
 
 JANET_CORE_FN(cfun_peg_replace,
               "(peg/replace peg repl text &opt start & args)",
-              "Replace first match of peg in text with repl, returning a new buffer. The peg does not need to make captures to do replacement. "
+              "Replace first match of `peg` in `text` with `subst`, returning a new buffer. "
+              "The peg does not need to make captures to do replacement. "
+              "If `subst` is a function, it will be called with the matching text, "
+              "and should return the actual replacement text to use. "
               "If no matches are found, returns the input string in a new buffer.") {
     return cfun_peg_replace_generic(argc, argv, 1);
 }

src/core/string.c

@@ -364,14 +364,13 @@ JANET_CORE_FN(cfun_string_findall,
 
 struct replace_state {
     struct kmp_state kmp;
-    const uint8_t *subst;
-    int32_t substlen;
+    Janet subst;
 };
 
 static void replacesetup(int32_t argc, Janet *argv, struct replace_state *s) {
     janet_arity(argc, 3, 4);
     JanetByteView pat = janet_getbytes(argv, 0);
-    JanetByteView subst = janet_getbytes(argv, 1);
+    Janet subst = argv[1];
     JanetByteView text = janet_getbytes(argv, 2);
     int32_t start = 0;
     if (argc == 4) {
@@ -380,13 +379,14 @@ static void replacesetup(int32_t argc, Janet *argv, struct replace_state *s) {
     }
     kmp_init(&s->kmp, text.bytes, text.len, pat.bytes, pat.len);
     s->kmp.i = start;
-    s->subst = subst.bytes;
-    s->substlen = subst.len;
+    s->subst = subst;
 }
 
 JANET_CORE_FN(cfun_string_replace,
               "(string/replace patt subst str)",
               "Replace the first occurrence of `patt` with `subst` in the string `str`. "
+              "If `subst` is a function, it will be called with `patt` only if a match is found, "
+              "and should return the actual replacement text to use. "
               "Will return the new string if `patt` is found, otherwise returns `str`.") {
     int32_t result;
     struct replace_state s;
@@ -397,10 +397,11 @@ JANET_CORE_FN(cfun_string_replace,
         kmp_deinit(&s.kmp);
         return janet_stringv(s.kmp.text, s.kmp.textlen);
     }
-    buf = janet_string_begin(s.kmp.textlen - s.kmp.patlen + s.substlen);
+    JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen);
+    buf = janet_string_begin(s.kmp.textlen - s.kmp.patlen + subst.len);
     safe_memcpy(buf, s.kmp.text, result);
-    safe_memcpy(buf + result, s.subst, s.substlen);
-    safe_memcpy(buf + result + s.substlen,
+    safe_memcpy(buf + result, subst.bytes, subst.len);
+    safe_memcpy(buf + result + subst.len,
                 s.kmp.text + result + s.kmp.patlen,
                 s.kmp.textlen - result - s.kmp.patlen);
     kmp_deinit(&s.kmp);
@@ -411,6 +412,8 @@ JANET_CORE_FN(cfun_string_replaceall,
               "(string/replace-all patt subst str)",
               "Replace all instances of `patt` with `subst` in the string `str`. Overlapping "
               "matches will not be counted, only the first match in such a span will be replaced. "
+              "If `subst` is a function, it will be called with `patt` once for each match, "
+              "and should return the actual replacement text to use. "
               "Will return the new string if `patt` is found, otherwise returns `str`.") {
     int32_t result;
     struct replace_state s;
@@ -419,8 +422,9 @@ JANET_CORE_FN(cfun_string_replaceall,
     replacesetup(argc, argv, &s);
     janet_buffer_init(&b, s.kmp.textlen);
     while ((result = kmp_next(&s.kmp)) >= 0) {
+        JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen);
         janet_buffer_push_bytes(&b, s.kmp.text + lastindex, result - lastindex);
-        janet_buffer_push_bytes(&b, s.subst, s.substlen);
+        janet_buffer_push_bytes(&b, subst.bytes, subst.len);
         lastindex = result + s.kmp.patlen;
         kmp_seti(&s.kmp, lastindex);
     }

src/core/util.c

@@ -663,6 +663,46 @@ JanetBinding janet_binding_from_entry(Janet entry) {
     return binding;
 }
 
+/* If the value at the given address can be coerced to a byte view,
+   return that byte view. If it can't, replace the value at the address
+   with the result of janet_to_string, and return a byte view over that
+   string. */
+static JanetByteView memoize_byte_view(Janet *value) {
+    JanetByteView result;
+    if (!janet_bytes_view(*value, &result.bytes, &result.len)) {
+        JanetString str = janet_to_string(*value);
+        *value = janet_wrap_string(str);
+        result.bytes = str;
+        result.len = janet_string_length(str);
+    }
+    return result;
+}
+
+static JanetByteView to_byte_view(Janet value) {
+    JanetByteView result;
+    if (!janet_bytes_view(value, &result.bytes, &result.len)) {
+        JanetString str = janet_to_string(value);
+        result.bytes = str;
+        result.len = janet_string_length(str);
+    }
+    return result;
+}
+
+JanetByteView janet_text_substitution(Janet *subst, const uint8_t *bytes, uint32_t len) {
+  switch (janet_type(*subst)) {
+      case JANET_CFUNCTION: {
+          Janet matched = janet_stringv(bytes, len);
+          return to_byte_view(janet_unwrap_cfunction(*subst)(1, &matched));
+      }
+      case JANET_FUNCTION: {
+          Janet matched = janet_stringv(bytes, len);
+          return to_byte_view(janet_call(janet_unwrap_function(*subst), 1, &matched));
+      }
+      default:
+          return memoize_byte_view(subst);
+  }
+}
+
 JanetBinding janet_resolve_ext(JanetTable *env, const uint8_t *sym) {
     Janet entry = janet_table_get(env, janet_wrap_symbol(sym));
     return janet_binding_from_entry(entry);

src/core/util.h

@@ -93,6 +93,7 @@ void janet_buffer_format(
     Janet *argv);
 Janet janet_next_impl(Janet ds, Janet key, int is_interpreter);
 JanetBinding janet_binding_from_entry(Janet entry);
+JanetByteView janet_text_substitution(Janet *subst, const uint8_t *bytes, uint32_t len);
 
 /* Registry functions */
 void janet_registry_put(

test/suite0002.janet

@@ -72,6 +72,10 @@
 (assert (= (string/replace "X" "." "XXX...XXX...XXX")  ".XX...XXX...XXX") "string/replace 1")
 (assert (= (string/replace-all "X" "." "XXX...XXX...XXX") "...............") "string/replace-all 1")
 (assert (= (string/replace-all "XX" "." "XXX...XXX...XXX") ".X....X....X") "string/replace-all 2")
+(assert (= (string/replace "xx" string/ascii-upper "xxyxyxyxxxy") "XXyxyxyxxxy") "string/replace function")
+(assert (= (string/replace-all "xx" string/ascii-upper "xxyxyxyxxxy") "XXyxyxyXXxy") "string/replace-all function")
+(assert (= (string/replace "x" 12 "xyx") "12yx") "string/replace stringable")
+(assert (= (string/replace-all "x" 12 "xyx") "12y12") "string/replace-all stringable")
 (assert (= (string/ascii-lower "ABCabc&^%!@:;.") "abcabc&^%!@:;.") "string/ascii-lower")
 (assert (= (string/ascii-upper "ABCabc&^%!@:;.") "ABCABC&^%!@:;.") "string/ascii-lower")
 (assert (= (string/reverse "") "") "string/reverse 1")

test/suite0008.janet

@@ -330,7 +330,6 @@ neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
 (assert (deep= (peg/find-all '"/" p) @[0 4 10 14]) "peg find-all")
 
 # Peg replace and replace-all
-(var ti 0)
 (defn check-replacer
   [x y z]
   (assert (= (string/replace x y z) (string (peg/replace x y z))) "replacer test replace")
@@ -339,6 +338,14 @@ neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
 (check-replacer "abc" "Z" "")
 (check-replacer "aba" "ZZZZZZ" "ababababababa")
 (check-replacer "aba" "" "ababababababa")
+(check-replacer "aba" string/ascii-upper "ababababababa")
+(check-replacer "aba" 123 "ababababababa")
+(assert (= (string (peg/replace-all ~(set "ab") string/ascii-upper "abcaa"))
+           "ABcAA")
+        "peg/replace-all cfunction")
+(assert (= (string (peg/replace-all ~(set "ab") |$ "abcaa"))
+           "abcaa")
+        "peg/replace-all function")
 
 # Peg bug
 (assert (deep= @[] (peg/match '(any 1) @"")) "peg empty pattern 1")