1 files changed, 529 insertions, 0 deletions
diff --git a/lib/readline.h b/lib/readline.h
new file mode 100644
index 0000000..2c05341
--- /dev/null
+++ b/lib/readline.h
@@ -0,0 +1,529 @@
+/*
+ * Copyright (c) 2026 Dylan Araps
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef DYLAN_READLINE
+#define DYLAN_READLINE
+
+#ifndef RL_MAX
+#error "RL_MAX not set"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "str.h"
+#include "utf8.h"
+#include "util.h"
+
+enum {
+  RL_NONE,
+  RL_PARTIAL,
+  RL_FULL,
+  RL_CAP = (RL_MAX >> 1) - 3,
+};
+
+struct readline {
+  str cl;
+  str cr;
+  cut pr;
+
+  usize vx;
+  usize vw;
+
+  usize prw;
+  usize clw;
+  usize crw;
+};
+
+static inline int
+rl_is_ifs(int c)
+{
+  return c == ' ' || c == '\t';
+}
+
+static inline usize
+rl_prompt(const struct readline *r)
+{
+  return r->prw + !!r->prw;
+}
+
+static inline usize
+rl_cursor(const struct readline *r)
+{
+  return rl_prompt(r) + r->clw;
+}
+
+static inline usize
+rl_total(const struct readline *r)
+{
+  return rl_cursor(r) + r->crw;
+}
+
+static inline void
+rl_vw_set(struct readline *r, usize vw)
+{
+  assert(vw);
+  r->vw = vw;
+  if (r->vx >= vw) r->vx = vw - 1;
+}
+
+static inline void
+rl_pr_set(struct readline *r, cut pr)
+{
+  r->pr = pr;
+  usize lw;
+  r->prw = utf8_cols(pr.d, pr.l, &lw);
+}
+
+static inline void
+rl_cr_set(struct readline *r, cut c)
+{
+  assert(c.l <= RL_CAP);
+  memcpy(r->cr.m + (r->cr.c - c.l), c.d, c.l);
+  r->cr.l = c.l;
+  usize lw;
+  r->crw = utf8_cols(c.d, c.l, &lw);
+}
+
+static inline void
+rl_cl_sync(struct readline *r)
+{
+  usize lw;
+  r->clw = utf8_cols(r->cl.m, r->cl.l, &lw);
+  usize c = rl_cursor(r);
+  if (c < r->vw) r->vx = c;
+  else r->vx = r->vw - lw;
+}
+
+static inline void
+rl_init(struct readline *r, usize vw, cut pr)
+{
+  STR_INIT(&r->cl, RL_MAX,      0, 0);
+  STR_INIT(&r->cr, RL_MAX >> 1, 0, 0);
+  rl_vw_set(r, vw);
+  rl_pr_set(r, pr);
+  r->vx = rl_prompt(r);
+  r->clw = 0;
+  r->crw = 0;
+}
+
+static inline const char *
+rl_cr_ptr(const struct readline *r)
+{
+  return r->cr.m + (r->cr.c - r->cr.l);
+}
+
+static inline cut
+rl_cr_get(const struct readline *r)
+{
+  return (cut) { rl_cr_ptr(r), r->cr.l };
+}
+
+static inline cut
+rl_cl_get(const struct readline *r)
+{
+  return (cut) { r->cl.m, r->cl.l };
+}
+
+static inline usize
+rl_cl_last(const struct readline *r, u32 *cp, int *w)
+{
+  usize l = utf8_decode_rev((const unsigned char *)r->cl.m, r->cl.l, cp);
+  *w = utf8_width(*cp);
+  return l;
+}
+
+static inline usize
+rl_cr_first(const struct readline *r, u32 *cp, int *w)
+{
+  const char *p = rl_cr_ptr(r);
+  char *n = utf8_decode((void *)p, cp);
+  *w = utf8_width(*cp);
+  return (usize)(n - p);
+}
+
+static inline usize
+rl_offset(const struct readline *r)
+{
+  usize c = rl_cursor(r);
+  return c > r->vx ? c - r->vx : 0;
+}
+
+static inline int
+rl_empty(const struct readline *r)
+{
+  return !r->cl.l && !r->cr.l;
+}
+
+static inline void
+rl_clear(struct readline *r)
+{
+  rl_pr_set(r, CUT_NULL);
+  r->cl.l = 0;
+  r->cr.l = 0;
+  r->clw = 0;
+  r->crw = 0;
+  r->vx = 0;
+}
+
+static inline usize
+rl_consume_cl(struct readline *r)
+{
+  usize w = 0;
+  do {
+    u32 cp;
+    int cw;
+    usize l = rl_cl_last(r, &cp, &cw);
+    r->cl.l -= l;
+    r->clw -= cw;
+    w += (usize)cw;
+    if (cw != 0) break;
+  } while (r->cl.l);
+  return w;
+}
+
+static inline usize
+rl_consume_cr(struct readline *r)
+{
+  usize w = 0;
+  do {
+    u32 cp;
+    int cw;
+    usize l = rl_cr_first(r, &cp, &cw);
+    r->cr.l -= l;
+    r->crw -= cw;
+    w += (usize)cw;
+    if (cw != 0 && !r->cr.l) break;
+    if (cw != 0) {
+      u32 ncp;
+      int nw;
+      rl_cr_first(r, &ncp, &nw);
+      if (nw != 0) break;
+    }
+  } while (r->cr.l);
+  return w;
+}
+
+static inline int
+rl_take_left_to_right(struct readline *r, usize *wo)
+{
+  if (!r->cl.l) return 0;
+  usize tw = 0;
+  for (;;) {
+    u32 cp;
+    int w;
+    usize l = rl_cl_last(r, &cp, &w);
+    if (r->cr.l + l > RL_CAP)
+      return -1;
+    r->cl.l -= l;
+    r->clw -= w;
+    usize o = r->cr.c - r->cr.l - l;
+    memcpy(r->cr.m + o, r->cl.m + r->cl.l, l);
+    r->cr.l += l;
+    r->crw += w;
+    tw += (usize)w;
+    if (!r->cl.l || w != 0) break;
+  }
+  if (wo) *wo = tw;
+  return 1;
+}
+
+static inline int
+rl_take_right_to_left(struct readline *r, usize *wo)
+{
+  if (!r->cr.l) return 0;
+  usize tw = 0;
+  for (;;) {
+    u32 cp;
+    int w;
+    usize l = rl_cr_first(r, &cp, &w);
+    if (r->cl.l + l > RL_CAP)
+      return -1;
+    str_copy(&r->cl, rl_cr_ptr(r), l);
+    r->cr.l -= l;
+    r->clw += w;
+    r->crw -= w;
+    tw += (usize)w;
+    if (!r->cr.l || w != 0) break;
+  }
+  if (wo) *wo = tw;
+  return 1;
+}
+
+static inline int
+rl_insert(struct readline *r, u32 c, const u8 *b, usize l, usize *n)
+{
+  if (r->cl.l + l >= RL_CAP) return RL_NONE;
+  u8 w = utf8_width(c);
+  str_copy(&r->cl, (const char *)b, l);
+  r->clw += w;
+  if (n) *n = w;
+  if (r->vx + w < r->vw) {
+    r->vx += w;
+    return RL_PARTIAL;
+  } else {
+    r->vx = r->vw - w;
+    return RL_FULL;
+  }
+}
+
+static inline int
+rl_backspace(struct readline *r, usize *n)
+{
+  if (!r->cl.l) return RL_NONE;
+  usize w = rl_consume_cl(r);
+  if (n) *n = w;
+  usize c = rl_cursor(r);
+  if (rl_total(r) < r->vw && r->vx == c + w) {
+    r->vx = c;
+    return RL_PARTIAL;
+  }
+  if (r->vx > c) r->vx = c;
+  return RL_FULL;
+}
+
+static inline int
+rl_delete(struct readline *r, usize *n)
+{
+  if (n) *n = 0;
+  if (!r->cr.l) return RL_NONE;
+  usize w = rl_consume_cr(r);
+  if (n) *n = w;
+  return r->vx + r->crw + w < r->vw ? RL_PARTIAL : RL_FULL;
+}
+
+static inline int
+rl_delete_left(struct readline *r)
+{
+  if (!r->cl.l) return RL_NONE;
+  r->cl.l = 0;
+  r->clw = 0;
+  r->vx = rl_prompt(r);
+  return RL_FULL;
+}
+
+static inline int
+rl_delete_right(struct readline *r)
+{
+  if (!r->cr.l) return RL_NONE;
+  r->cr.l = 0;
+  r->crw = 0;
+  return RL_PARTIAL;
+}
+
+static inline int
+rl_left(struct readline *r, usize *n)
+{
+  if (n) *n = 0;
+  if (!r->cl.l) {
+    if (!rl_offset(r)) return RL_NONE;
+    r->vx = rl_cursor(r);
+    return RL_FULL;
+  }
+  usize w;
+  if (rl_take_left_to_right(r, &w) < 0) return RL_NONE;
+  if (n) *n = w;
+  if (r->vx >= w && r->vx - w > 0) {
+    r->vx -= w;
+    return RL_PARTIAL;
+  }
+  return RL_FULL;
+}
+
+static inline int
+rl_right(struct readline *r, usize *n)
+{
+  if (!r->cr.l) return RL_NONE;
+  usize w;
+  if (rl_take_right_to_left(r, &w) < 0) return RL_NONE;
+  if (n) *n = w;
+  if (r->vx + w + w <= r->vw) {
+    r->vx += w;
+    return RL_PARTIAL;
+  }
+  return RL_FULL;
+}
+
+static inline void
+rl_join(struct readline *r)
+{
+  str_copy(&r->cl, rl_cr_ptr(r), r->cr.l);
+  str_terminate(&r->cl);
+  r->clw += r->crw;
+  r->cr.l = 0;
+  r->crw = 0;
+}
+
+static inline int
+rl_home(struct readline *r)
+{
+  if (!r->cl.l) return RL_NONE;
+  if (r->cr.l + r->cl.l > RL_CAP) return RL_NONE;
+  usize s = rl_offset(r);
+  usize o = r->cr.c - r->cr.l - r->cl.l;
+  memcpy(r->cr.m + o, r->cl.m, r->cl.l);
+  r->cr.l += r->cl.l;
+  r->crw += r->clw;
+  r->cl.l = 0;
+  r->clw = 0;
+  r->vx = rl_prompt(r);
+  return s ? RL_FULL : RL_PARTIAL;
+}
+
+static inline int
+rl_end(struct readline *r)
+{
+  if (!r->cr.l) return RL_NONE;
+  if (r->cl.l + r->cr.l > RL_CAP) return RL_NONE;
+  str_copy(&r->cl, rl_cr_ptr(r), r->cr.l);
+  r->clw += r->crw;
+  r->cr.l = 0;
+  r->crw = 0;
+  usize c = rl_cursor(r);
+  if (c < r->vw) {
+    r->vx = c;
+    return RL_PARTIAL;
+  }
+  u32 cp;
+  int w;
+  rl_cl_last(r, &cp, &w);
+  r->vx = r->vw - w;
+  return RL_FULL;
+}
+
+static inline int
+rl_word_left(struct readline *r)
+{
+  if (!r->cl.l) return RL_NONE;
+  u32 cp;
+  int w;
+  while (r->cl.l) {
+    rl_cl_last(r, &cp, &w);
+    if (!rl_is_ifs(cp)) break;
+    if (rl_left(r, NULL) == RL_NONE) break;
+  }
+  while (r->cl.l) {
+    rl_cl_last(r, &cp, &w);
+    if (rl_is_ifs(cp))  break;
+    if (rl_left(r, NULL) == RL_NONE) break;
+  }
+  return RL_FULL;
+}
+
+static inline int
+rl_word_right(struct readline *r)
+{
+  if (!r->cr.l) return RL_NONE;
+  u32 cp;
+  int w;
+  while (r->cr.l) {
+    rl_cr_first(r, &cp, &w);
+    if (!rl_is_ifs(cp))  break;
+    if (rl_right(r, NULL) == RL_NONE) break;
+  }
+  while (r->cr.l) {
+    rl_cr_first(r, &cp, &w);
+    if (rl_is_ifs(cp))   break;
+    if (rl_right(r, NULL) == RL_NONE) break;
+  }
+  return RL_FULL;
+}
+
+static inline int
+rl_delete_word_prev(struct readline *r)
+{
+  if (!r->cl.l) return -1;
+  usize d = 0;
+  u32 cp;
+  int w;
+  for (; r->cl.l; d++) {
+    rl_cl_last(r, &cp, &w);
+    if (!rl_is_ifs(cp))      break;
+    if (rl_backspace(r, NULL) == RL_NONE) break;
+  }
+  for (; r->cl.l; d++) {
+    rl_cl_last(r, &cp, &w);
+    if (rl_is_ifs(cp))       break;
+    if (rl_backspace(r, NULL) == RL_NONE) break;
+  }
+  return d ? RL_FULL : RL_NONE;
+}
+
+static inline int
+rl_delete_word_right(struct readline *r)
+{
+  if (!r->cr.l) return RL_NONE;
+  usize d = 0;
+  u32 cp;
+  int w;
+  for (; r->cr.l; d++) {
+    rl_cr_first(r, &cp, &w);
+    if (!rl_is_ifs(cp))   break;
+    if (rl_delete(r, NULL) == RL_NONE) break;
+  }
+  for (; r->cr.l; d++) {
+    rl_cr_first(r, &cp, &w);
+    if (rl_is_ifs(cp))    break;
+    if (rl_delete(r, NULL) == RL_NONE) break;
+  }
+  return d ? RL_FULL : RL_NONE;
+}
+
+static inline usize
+rl_write_seg(str *s, const unsigned char *p, usize l, usize c, usize x, usize e)
+{
+  const unsigned char *pe = p + l;
+  u32 cp;
+  while (p < pe) {
+    const unsigned char *nc = utf8_decode((void *)p, &cp);
+    int w = utf8_width(cp);
+    if (c < x && c + w > x)
+      str_push_c(s, ' ');
+    else if (c + w > x && c + w <= e)
+      str_push(s, (const char *)p, (usize)(nc - p));
+    c += w;
+    if (c >= e) return c;
+    p = nc;
+  }
+  return c;
+}
+
+static inline void
+rl_write_range(const struct readline *r, str *s, usize x, usize n)
+{
+  usize c = 0;
+  usize e = x + n;
+  c = rl_write_seg(s, (const unsigned char *)r->pr.d, r->pr.l, c, x, e);
+  if (c >= e) return;
+  c = rl_write_seg(s, (const unsigned char *)r->cl.m, r->cl.l, c, x, e);
+  if (c >= e) return;
+  c = rl_write_seg(s, (const unsigned char *)rl_cr_ptr(r), r->cr.l, c, x, e);
+  if (c < e) str_memset(s, ' ', e - c);
+}
+
+static inline void
+rl_write_visible(const struct readline *r, str *s)
+{
+  rl_write_range(r, s, rl_offset(r), r->vw);
+}
+
+#endif // DYLAN_READLINE
+