repl.c

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/*
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2025 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */


#include "repl.h"
#include "bytecode.h"
#include "parser.h"
#include "value.h"
#include "vm.h"

/* include mapping helper from parser_utils.c */
extern int map_expanded_line_to_include_path(const char *path, int line, char *out_path, size_t out_path_cap, int *out_line);

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#ifndef _WIN32
#include <dirent.h>
#include <limits.h>
#include <sys/stat.h>
#include <termios.h>
#include <unistd.h>
#endif

#ifdef FUN_WITH_REPL

#ifndef FUN_VERSION
#define FUN_VERSION "0.0.0-dev"
#endif

/* --------- REPL history (in-memory + file integration) ---------- */
enum { RL_HIST_MAX = 1000 };
static char *rl_hist[RL_HIST_MAX];
static int rl_count = 0;

/* last history entry (or NULL) */
static const char *rl_hist_last(void) {
 if (rl_count <= 0) return NULL;
 return rl_hist[rl_count - 1];
}

/* add one line to in-memory history (without trailing newline), dedup consecutive */
static void rl_hist_add(const char *s) {
 if (!s) return;
 size_t n = strlen(s);
 /* strip single trailing newline if present */
 while (n > 0 && (s[n - 1] == '\n' || s[n - 1] == '\r'))
 n--;
 if (n == 0) return;
 /* dedupe consecutive identical */
 const char *last = rl_hist_last();
 if (last && strncmp(last, s, n) == 0 && last[n] == '\0') return;

 /* allocate and copy */
 char *cpy = (char *)malloc(n + 1);
 if (!cpy) return;
 memcpy(cpy, s, n);
 cpy[n] = '\0';

 if (rl_count == RL_HIST_MAX) {
 free(rl_hist[0]);
 memmove(&rl_hist[0], &rl_hist[1], sizeof(rl_hist[0]) * (RL_HIST_MAX - 1));
 rl_count--;
 }
 rl_hist[rl_count++] = cpy;
}

/* preload history from file (one line per entry) */
static void rl_hist_load_file(const char *path) {
 if (!path) return;
 FILE *f = fopen(path, "r");
 if (!f) return;
 char line[4096];
 while (fgets(line, sizeof(line), f)) {
 rl_hist_add(line);
 }
 fclose(f);
}

#ifndef _WIN32
static struct termios g_orig_tios;
static int g_raw_enabled = 0;

static void repl_disable_raw(void) {
 if (g_raw_enabled) {
 tcsetattr(STDIN_FILENO, TCSAFLUSH, &g_orig_tios);
 g_raw_enabled = 0;
 }
}
static int repl_enable_raw(void) {
 if (!isatty(STDIN_FILENO)) return 0;
 if (g_raw_enabled) return 1;
 if (tcgetattr(STDIN_FILENO, &g_orig_tios) == -1) return 0;
 struct termios raw = g_orig_tios;
 raw.c_lflag &= ~(ICANON | ECHO);
 raw.c_cc[VMIN] = 1;
 raw.c_cc[VTIME] = 0;
 if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) return 0;
 g_raw_enabled = 1;
 return 1;
}

/* return 1 if path is a directory, else 0 */
static int is_dir_path(const char *path) {
 struct stat st;
 if (stat(path, &st) != 0) return 0;
 return S_ISDIR(st.st_mode);
}

/* Compute longest common prefix of a set of strings (starting from offset base_len) */
static size_t lcp_suffix(const char **names, int count, size_t base_len) {
 if (count <= 0) return base_len;
 size_t lcp = (size_t)-1;
 for (int i = 0; i < count; ++i) {
 size_t nlen = strlen(names[i]);
 size_t cur = 0;
 /* compare suffix part starting at base_len */
 while (base_len + cur < nlen) {
 char c = names[i][base_len + cur];
 int ok = 1;
 for (int j = 0; j < count; ++j) {
 size_t jlen = strlen(names[j]);
 if (base_len + cur >= jlen || names[j][base_len + cur] != c) {
 ok = 0;
 break;
 }
 }
 if (!ok) break;
 cur++;
 }
 if (lcp == (size_t)-1 || cur < lcp) lcp = cur;
 }
 return base_len + (lcp == (size_t)-1 ? 0 : lcp);
}

/* Word-jump helpers (used by Ctrl+Left/Right in the REPL editor).
 * Words are runs of non-space characters; separators are spaces.
 */
static void rl_word_left(const char *out, size_t len, size_t *pos) {
 (void)len;
 if (!out || !pos) return;
 if (*pos == 0) return;
 while (*pos > 0 && out[*pos - 1] == ' ')
 (*pos)--;
 while (*pos > 0 && out[*pos - 1] != ' ')
 (*pos)--;
}
static void rl_word_right(const char *out, size_t len, size_t *pos) {
 if (!out || !pos) return;
 if (*pos >= len) return;
 while (*pos < len && out[*pos] != ' ')
 (*pos)++;
 while (*pos < len && out[*pos] == ' ')
 (*pos)++;
}

/* Expand file path for path-taking REPL commands (e.g., :load, :run) in-place; returns 1 if buffer changed (redraw) */
static int complete_load_path(char *buf, size_t *len_io) {
 size_t len = *len_io;
 if (len < 3) return 0; /* minimally ":x" */
 const char *p = buf;
 while (*p == ' ')
 p++;
 if (*p != ':') return 0;
 p++;
 /* Parse command token (letters only) */
 const char *cmd_start = p;
 while (*p && ((*p >= 'a' && *p <= 'z') || (*p >= 'A' && *p <= 'Z')))
 p++;
 size_t cmd_len = (size_t)(p - cmd_start);
 if (cmd_len == 0) return 0;
 /* Accept both full and short aliases for :load and :run */
 int is_supported = 0;
 if ((cmd_len == 4 && strncmp(cmd_start, "load", 4) == 0) ||
 (cmd_len == 2 && strncmp(cmd_start, "lo", 2) == 0) ||
 (cmd_len == 3 && strncmp(cmd_start, "run", 3) == 0) ||
 (cmd_len == 2 && strncmp(cmd_start, "ru", 2) == 0)) {
 is_supported = 1;
 }
 if (!is_supported) return 0;
 while (*p == ' ' || *p == '\t')
 p++;
 size_t arg_off = (size_t)(p - buf);
 if (arg_off > len) return 0;

 char prefix[PATH_MAX];
 size_t plen = 0;
 if (len - arg_off >= sizeof(prefix))
 plen = sizeof(prefix) - 1;
 else
 plen = len - arg_off;
 memcpy(prefix, buf + arg_off, plen);
 prefix[plen] = '\0';

 char expanded[PATH_MAX];
 if (prefix[0] == '~') {
 const char *home = getenv("HOME");
 if (!home) home = getenv("USERPROFILE");
 if (home)
 snprintf(expanded, sizeof(expanded), "%s%s", home, prefix + 1);
 else
 snprintf(expanded, sizeof(expanded), "%s", prefix);
 } else {
 snprintf(expanded, sizeof(expanded), "%s", prefix);
 }

 char dirpart[PATH_MAX], base[PATH_MAX];
 const char *slash = strrchr(expanded, '/');
 if (slash) {
 size_t dlen = (size_t)(slash - expanded);
 if (dlen == 0) {
 strcpy(dirpart, "/");
 } else {
 memcpy(dirpart, expanded, dlen);
 dirpart[dlen] = '\0';
 }
 snprintf(base, sizeof(base), "%s", slash + 1);
 } else {
 strcpy(dirpart, ".");
 snprintf(base, sizeof(base), "%s", expanded);
 }

 DIR *dp = opendir(dirpart);
 if (!dp) {
 fputc('\a', stdout);
 fflush(stdout);
 return 0;
 }

 const char *names[1024];
 char storage[1024][NAME_MAX + 1];
 int count = 0;
 struct dirent *de;
 size_t blen = strlen(base);
 while ((de = readdir(dp)) != NULL) {
 if (blen == 0 || strncmp(de->d_name, base, blen) == 0) {
 if (count < (int)(sizeof(names) / sizeof(names[0]))) {
 snprintf(storage[count], sizeof(storage[count]), "%s", de->d_name);
 names[count] = storage[count];
 count++;
 }
 }
 }
 closedir(dp);

 if (count == 0) {
 fputc('\a', stdout);
 fflush(stdout);
 return 0;
 }

 size_t new_pref_len = lcp_suffix(names, count, blen);
 int changed = 0;

 char completed[PATH_MAX];
 if (slash) {
 char head[PATH_MAX];
 memcpy(head, expanded, (size_t)(slash - expanded + 1));
 head[slash - expanded + 1] = '\0';
 strncpy(completed, head, sizeof(completed));
 } else {
 snprintf(completed, sizeof(completed), "%s", "");
 }

 strncat(completed, base, sizeof(completed) - strlen(completed) - 1);
 if (new_pref_len > blen) {
 strncat(completed, names[0] + blen, (new_pref_len - blen));
 changed = 1;
 } else if (count == 1) {
 size_t extra = strlen(names[0]) - blen;
 strncat(completed, names[0] + blen, extra);
 changed = 1;
 }

 if (count == 1) {
 char test[PATH_MAX];
 if (slash)
 snprintf(test, sizeof(test), "%.*s/%s", (int)(slash - expanded), expanded, names[0]);
 else
 snprintf(test, sizeof(test), "%s", names[0]);
 if (is_dir_path(test)) {
 strncat(completed, "/", sizeof(completed) - strlen(completed) - 1);
 }
 }

 if (!changed && count > 1) {
 putchar('\n');
 for (int i = 0; i < count; ++i) {
 fputs(names[i], stdout);
 fputc(((i + 1) % 6 == 0) ? '\n' : '\t', stdout);
 }
 if (count % 6 != 0) putchar('\n');
 fflush(stdout);
 return 0;
 }

 size_t comp_len = strlen(completed);
 if (arg_off + comp_len >= PATH_MAX - 1) comp_len = PATH_MAX - 2 - arg_off;
 memcpy(buf + arg_off, completed, comp_len);
 *len_io = arg_off + comp_len;
 buf[*len_io] = '\0';
 return 1;
}

/* ---------- Stdlib symbol completion ---------- */
static char **g_std_syms = NULL;
static int g_std_syms_count = 0;
static int g_std_syms_cap = 0;

static int is_ident_start(int c) {
 return (c == '_' || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'));
}
static int is_ident_char(int c) {
 return is_ident_start(c) || (c >= '0' && c <= '9');
}

static void std_syms_add(const char *name) {
 if (!name || !*name) return;
 /* dedupe */
 for (int i = 0; i < g_std_syms_count; ++i) {
 if (strcmp(g_std_syms[i], name) == 0) return;
 }
 if (g_std_syms_count == g_std_syms_cap) {
 int ncap = g_std_syms_cap == 0 ? 256 : g_std_syms_cap * 2;
 char **nn = (char **)realloc(g_std_syms, (size_t)ncap * sizeof(char *));
 if (!nn) return;
 g_std_syms = nn;
 g_std_syms_cap = ncap;
 }
 size_t n = strlen(name);
 char *cpy = (char *)malloc(n + 1);
 if (!cpy) return;
 memcpy(cpy, name, n + 1);
 g_std_syms[g_std_syms_count++] = cpy;
}

static void scan_symbols_from_file(const char *path) {
 FILE *f = fopen(path, "r");
 if (!f) return;
 char line[4096];
 while (fgets(line, sizeof(line), f)) {
 const char *p = line;
 while (*p == ' ' || *p == '\t')
 p++;
 /* Patterns: fun NAME( ; class NAME ; const NAME ; var NAME */
 const char *kw = NULL;
 if (strncmp(p, "fun ", 4) == 0) {
 kw = "fun";
 p += 4;
 } else if (strncmp(p, "class ", 6) == 0) {
 kw = "class";
 p += 6;
 } else if (strncmp(p, "const ", 6) == 0) {
 kw = "const";
 p += 6;
 } else if (strncmp(p, "var ", 4) == 0) {
 kw = "var";
 p += 4;
 }
 if (!kw) continue;
 while (*p == ' ' || *p == '\t')
 p++;
 if (!is_ident_start((unsigned char)*p)) continue;
 char name[256];
 size_t ni = 0;
 while (is_ident_char((unsigned char)*p) && ni + 1 < sizeof(name)) {
 name[ni++] = *p++;
 }
 name[ni] = '\0';
 if (ni > 0) std_syms_add(name);
 }
 fclose(f);
}

static void scan_dir_recursive(const char *dir) {
 DIR *dp = opendir(dir);
 if (!dp) return;
 struct dirent *de;
 char path[PATH_MAX];
 while ((de = readdir(dp)) != NULL) {
 const char *n = de->d_name;
 if (strcmp(n, ".") == 0 || strcmp(n, "..") == 0) continue;
 snprintf(path, sizeof(path), "%s/%s", dir, n);
 struct stat st;
 if (stat(path, &st) != 0) continue;
 if (S_ISDIR(st.st_mode)) {
 scan_dir_recursive(path);
 } else {
 size_t L = strlen(n);
 if (L >= 4 && strcmp(n + (L - 4), ".fun") == 0) {
 scan_symbols_from_file(path);
 }
 }
 }
 closedir(dp);
}

static void load_stdlib_symbols(const char *libdir) {
 if (!libdir || !*libdir) return;
 scan_dir_recursive(libdir);
}

static void free_stdlib_symbols(void) {
 for (int i = 0; i < g_std_syms_count; ++i)
 free(g_std_syms[i]);
 free(g_std_syms);
 g_std_syms = NULL;
 g_std_syms_count = g_std_syms_cap = 0;
}

/* Complete the trailing identifier in 'buf' using stdlib symbols.
 Returns 1 if buffer changed, 2 if a menu was printed, 0 otherwise. */
static int complete_stdlib_ident(char *buf, size_t *len_io, size_t *pos_io, size_t cap) {
 size_t len = *len_io;
 size_t pos = *pos_io;
 if (pos != len) return 0; /* complete only at end */
 if (len == 0) return 0;

 /* find start of identifier */
 size_t start = len;
 while (start > 0 && is_ident_char((unsigned char)buf[start - 1]))
 start--;
 if (start == len) return 0;

 const char *prefix = buf + start;
 size_t plen = len - start;

 /* collect matches */
 const char *matches[1024];
 int mcount = 0;
 for (int i = 0; i < g_std_syms_count && mcount < (int)(sizeof(matches) / sizeof(matches[0])); ++i) {
 if (strncmp(g_std_syms[i], prefix, plen) == 0) {
 matches[mcount++] = g_std_syms[i];
 }
 }
 if (mcount == 0) {
 fputc('\a', stdout);
 fflush(stdout);
 return 0;
 }

 /* compute longest common extension */
 size_t lcp = (size_t)-1;
 for (int i = 0; i < mcount; ++i) {
 size_t nlen = strlen(matches[i]);
 size_t cur = 0;
 while (plen + cur < nlen) {
 char c = matches[i][plen + cur];
 int ok = 1;
 for (int j = 0; j < mcount; ++j) {
 size_t jlen = strlen(matches[j]);
 if (plen + cur >= jlen || matches[j][plen + cur] != c) {
 ok = 0;
 break;
 }
 }
 if (!ok) break;
 cur++;
 }
 if (lcp == (size_t)-1 || cur < lcp) lcp = cur;
 }
 size_t new_pref_len = plen + (lcp == (size_t)-1 ? 0 : lcp);

 /* build completion text */
 char comp[512];
 size_t write_len = 0;
 if (mcount == 1) {
 snprintf(comp, sizeof(comp), "%s", matches[0]);
 write_len = strlen(comp);
 } else if (new_pref_len > plen) {
 strncpy(comp, prefix, plen);
 comp[plen] = '\0';
 strncat(comp, matches[0] + plen, new_pref_len - plen);
 write_len = strlen(comp);
 } else {
 /* list candidates */
 putchar('\n');
 for (int i = 0; i < mcount; ++i) {
 fputs(matches[i], stdout);
 fputc(((i + 1) % 6 == 0) ? '\n' : '\t', stdout);
 }
 if (mcount % 6 != 0) putchar('\n');
 fflush(stdout);
 return 2;
 }

 /* replace tail from 'start' with comp */
 if (start + write_len >= cap) write_len = cap - 1 - start;
 memmove(buf + start, comp, write_len);
 *len_io = start + write_len;
 buf[*len_io] = '\0';
 *pos_io = *len_io;
 return 1;
}

/* Read one line with prompt, handling backspace, Up/Down history and :load path completion (now with multi-line editing via Ctrl+O) */
static int read_line_edit(char *out, size_t out_cap, const char *prompt) {
#ifdef _WIN32
 if (prompt) fputs(prompt, stdout), fflush(stdout);
 if (!fgets(out, (int)out_cap, stdin)) return 0;
 return 1;
#else
 if (prompt) fputs(prompt, stdout), fflush(stdout);
 if (!repl_enable_raw()) {
 if (!fgets(out, (int)out_cap, stdin)) return 0;
 return 1;
 }

 size_t len = 0;
 size_t pos = 0;
 int hist_pos = rl_count;
 char saved_current[4096];
 int has_saved = 0;

 /* How many terminal rows were drawn in the previous repaint (prompt + lines in 'out').
 We assume no automatic wrapping (only explicit '\n'). */
 static int prev_rows = 1;

#define RL_REDRAW() \
 do { \
 /* Count explicit newlines to estimate rows to draw (prompt line + content lines) */ \
 int rows = 1; \
 int has_nl = 0; \
 for (size_t __i = 0; __i < len; ++__i) { \
 if (out[__i] == '\n') { \
 rows++; \
 has_nl = 1; \
 } \
 } \
 /* Move cursor to the start (top) of the previous render block */ \
 if (prev_rows > 1) { \
 fprintf(stdout, "\x1b[%dA", prev_rows - 1); \
 } \
 fputc('\r', stdout); \
 /* Repaint prompt + content */ \
 if (prompt) fputs(prompt, stdout); \
 fwrite(out, 1, len, stdout); \
 /* Clear everything below the current cursor (removes remnants of older, longer renders) */ \
 fputs("\x1b[J", stdout); \
 /* Cursor policy: keep at end for multi-line; for single-line respect pos */ \
 if (!has_nl && pos < len) { \
 size_t back = (size_t)(len - pos); \
 if (back > 0) fprintf(stdout, "\x1b[%zuD", back); \
 } else { \
 pos = len; \
 } \
 prev_rows = rows; \
 fflush(stdout); \
 } while (0)

 for (;;) {
 int ch = getchar();
 if (ch == EOF) {
 repl_disable_raw();
 return 0;
 }

 if (ch == '\r' || ch == '\n') {
 fputc('\n', stdout);
 if (len + 1 < out_cap) {
 out[len++] = '\n';
 out[len] = '\0';
 } else {
 out[len] = '\0';
 }
 rl_hist_add(out);
 repl_disable_raw();
 return 1;
 } else if (ch == 27) {
 int c1 = getchar();
 if (c1 == '[') {
 char params[16];
 int pi = 0;
 int final = 0;
 for (;;) {
 int cx = getchar();
 if (cx == EOF) break;
 if ((cx >= 'A' && cx <= 'Z') || (cx >= 'a' && cx <= 'z') || cx == '~') {
 final = cx;
 break;
 }
 if (pi + 1 < (int)sizeof(params)) {
 params[pi++] = (char)cx;
 params[pi] = '\0';
 }
 }
 int ctrl = 0;
 if (pi > 0) {
 if (strstr(params, ";5") != NULL || strcmp(params, "5") == 0 || strstr(params, "1;5") != NULL) {
 ctrl = 1;
 }
 }

 /* disallow fine-grained horizontal movement in multi-line mode (cursor stays at end) */
 int has_nl = 0;
 for (size_t __i = 0; __i < len; ++__i) {
 if (out[__i] == '\n') {
 has_nl = 1;
 break;
 }
 }

 if (final == 'A') {
 if (!has_saved) {
 size_t sl = len < sizeof(saved_current) - 1 ? len : sizeof(saved_current) - 1;
 memcpy(saved_current, out, sl);
 saved_current[sl] = '\0';
 has_saved = 1;
 }
 if (hist_pos > 0) {
 hist_pos--;
 const char *h = rl_hist[hist_pos];
 size_t hl = strlen(h);
 if (hl >= out_cap) hl = out_cap - 1;
 memcpy(out, h, hl);
 out[hl] = '\0';
 len = hl;
 pos = len;
 RL_REDRAW();
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else if (final == 'B') {
 if (hist_pos < rl_count) {
 hist_pos++;
 if (hist_pos == rl_count) {
 if (has_saved) {
 size_t hl = strlen(saved_current);
 if (hl >= out_cap) hl = out_cap - 1;
 memcpy(out, saved_current, hl);
 out[hl] = '\0';
 len = hl;
 } else {
 len = 0;
 out[0] = '\0';
 }
 } else {
 const char *h = rl_hist[hist_pos];
 size_t hl = strlen(h);
 if (hl >= out_cap) hl = out_cap - 1;
 memcpy(out, h, hl);
 out[hl] = '\0';
 len = hl;
 }
 pos = len;
 RL_REDRAW();
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else if (final == 'C') {
 if (has_nl) {
 fputc('\a', stdout);
 fflush(stdout);
 pos = len;
 RL_REDRAW();
 } else if (ctrl) {
 size_t old = pos;
 rl_word_right(out, len, &pos);
 if (pos != old)
 RL_REDRAW();
 else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else {
 if (pos < len) {
 pos++;
 fputs("\x1b[C", stdout);
 fflush(stdout);
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 }
 } else if (final == 'D') {
 if (has_nl) {
 fputc('\a', stdout);
 fflush(stdout);
 pos = len;
 RL_REDRAW();
 } else if (ctrl) {
 size_t old = pos;
 rl_word_left(out, len, &pos);
 if (pos != old)
 RL_REDRAW();
 else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else {
 if (pos > 0) {
 pos--;
 fputs("\x1b[D", stdout);
 fflush(stdout);
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 }
 } else {
 /* ignore other CSI sequences */
 }
 }
 } else if (ch == 127 || ch == 8) {
 if (pos > 0) {
 memmove(out + pos - 1, out + pos, len - pos);
 len--;
 pos--;
 out[len] = '\0';
 RL_REDRAW();
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else if (ch == '\t') {
 if (pos != len) {
 fputc('\a', stdout);
 fflush(stdout);
 } else {
 out[len] = '\0';
 size_t newlen = len;
 int changed = complete_load_path(out, &newlen);
 if (changed) {
 len = newlen;
 pos = len;
 } else {
 /* try stdlib symbol completion */
 int res = complete_stdlib_ident(out, &newlen, &pos, out_cap);
 if (res == 1) {
 len = newlen;
 } else if (res == 2) {
 /* menu printed — do not modify buffer, just redraw prompt+line */
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 }
 RL_REDRAW();
 }
 } else if (ch == 15) { /* Ctrl+O -> insert newline at cursor (multi-line editing) */
 if (len + 1 < out_cap) {
 memmove(out + pos + 1, out + pos, len - pos);
 out[pos] = '\n';
 len++;
 pos++;
 out[len] = '\0';
 hist_pos = rl_count;
 RL_REDRAW();
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else if (ch >= 32 && ch <= 126) {
 if (len + 1 < out_cap) {
 memmove(out + pos + 1, out + pos, len - pos);
 out[pos] = (char)ch;
 len++;
 pos++;
 out[len] = '\0';
 hist_pos = rl_count;
 RL_REDRAW();
 } else {
 fputc('\a', stdout);
 fflush(stdout);
 }
 } else {
 /* ignore other control characters */
 }
 }
#endif
}
#endif /* !_WIN32 */

/* ---------- Small utilities ---------- */

static int is_blank_line(const char *s) {
 for (const char *p = s; *p; ++p) {
 if (*p != ' ' && *p != '\t' && *p != '\r' && *p != '\n') return 0;
 }
 return 1;
}

static const char *lstrip(const char *s) {
 while (*s == ' ' || *s == '\t')
 s++;
 return s;
}

static int ends_with_opener(const char *line) {
 size_t n = strlen(line);
 while (n > 0 && (line[n - 1] == ' ' || line[n - 1] == '\t' || line[n - 1] == '\r' || line[n - 1] == '\n'))
 n--;
 if (n == 0) return 0;
 char c = line[n - 1];
 if (c == '+' || c == '-' || c == '*' || c == '/' || c == '%' ||
 c == '<' || c == '>' || c == '=' || c == '!' || c == '&' || c == '|' || c == ',') {
 return 1;
 }
 return 0;
}

/* Compute how many indentation levels (2 spaces per level) are still open. */
static int compute_open_indent_blocks(const char *buf) {
 int in_block_comment = 0;
 int open = 0;
 int have_baseline = 0;
 int cur = 0;

 const char *p = buf;
 while (*p) {
 const char *line = p;
 while (*p && *p != '\n')
 p++;
 const char *line_end = p;
 if (*p == '\n') p++;

 if (in_block_comment) {
 const char *q = line;
 while (q < line_end) {
 if (q + 1 < line_end && q[0] == '*' && q[1] == '/') {
 in_block_comment = 0;
 q += 2;
 break;
 }
 q++;
 }
 if (in_block_comment) continue;
 }

 const char *s = line;
 int spaces = 0;
 while (s < line_end && *s == ' ') {
 spaces++;
 s++;
 }
 while (s < line_end && *s == '\t') {
 s++;
 }

 const char *t = s;
 if (t >= line_end) continue;

 if ((t + 1) <= line_end && t[0] == '/' && (t + 1 < line_end && (t[1] == '/' || t[1] == '*'))) {
 if (t[1] == '/') {
 continue;
 } else if (t[1] == '*') {
 in_block_comment = 1;
 continue;
 }
 }

 int lvl = spaces / 2;
 if (!have_baseline) {
 cur = lvl;
 have_baseline = 1;
 continue;
 }
 if (lvl > cur) {
 open += (lvl - cur);
 } else if (lvl < cur) {
 int dec = (cur - lvl);
 if (dec > open)
 open = 0;
 else
 open -= dec;
 }
 cur = lvl;
 }
 return open;
}

/* Detect if current buffer looks incomplete. */
static int buffer_looks_incomplete(const char *buf) {
 int in_single = 0, in_double = 0, escape = 0;
 int in_block_comment = 0, in_line_comment = 0;
 int paren = 0;

 const char *p = buf;
 const char *last_sig_line = NULL;

 while (*p) {
 char c = *p;

 if (in_line_comment) {
 if (c == '\n') in_line_comment = 0;
 p++;
 continue;
 }
 if (in_block_comment) {
 if (c == '*' && p[1] == '/') {
 in_block_comment = 0;
 p += 2;
 continue;
 }
 p++;
 continue;
 }

 if (!in_single && !in_double) {
 if (c == '/' && p[1] == '/') {
 in_line_comment = 1;
 p += 2;
 continue;
 }
 if (c == '/' && p[1] == '*') {
 in_block_comment = 1;
 p += 2;
 continue;
 }
 }

 if (in_single) {
 if (!escape && c == '\\') {
 escape = 1;
 p++;
 continue;
 }
 if (!escape && c == '\'') {
 in_single = 0;
 p++;
 continue;
 }
 escape = 0;
 p++;
 continue;
 } else if (in_double) {
 if (!escape && c == '\\') {
 escape = 1;
 p++;
 continue;
 }
 if (!escape && c == '"') {
 in_double = 0;
 p++;
 continue;
 }
 escape = 0;
 p++;
 continue;
 } else {
 if (c == '\'') {
 in_single = 1;
 p++;
 continue;
 }
 if (c == '"') {
 in_double = 1;
 p++;
 continue;
 }
 if (c == '(') {
 paren++;
 p++;
 continue;
 }
 if (c == ')') {
 if (paren > 0) paren--;
 p++;
 continue;
 }
 }

 if (c == '\n') {
 const char *q = p + 1;
 while (*q == ' ' || *q == '\t')
 q++;
 if (*q && *q != '\n') last_sig_line = q;
 }
 p++;
 }

 if (!last_sig_line) {
 const char *q = buf;
 const char *candidate = NULL;
 while (*q) {
 const char *line_start = q;
 while (*q && *q != '\n')
 q++;
 const char *t = line_start;
 while (*t == ' ' || *t == '\t')
 t++;
 if (*t && *t != '\n' && *t != '\r') candidate = t;
 if (*q == '\n') q++;
 }
 last_sig_line = candidate;
 }

 if (in_single || in_double || in_block_comment || paren > 0) return 1;

 if (last_sig_line) {
 if (strncmp(lstrip(last_sig_line), "if", 2) == 0 ||
 strncmp(lstrip(last_sig_line), "else", 4) == 0 ||
 strncmp(lstrip(last_sig_line), "while", 5) == 0 ||
 strncmp(lstrip(last_sig_line), "for", 3) == 0 ||
 strncmp(lstrip(last_sig_line), "fun", 3) == 0) {
 return 1;
 }
 if (ends_with_opener(last_sig_line)) return 1;
 }

 return 0;
}

static void show_repl_help(void) {
 printf("Commands:\n");
 printf(" :help | :h Show this help\n");
 printf(" :quit | :q | :exit Exit the REPL\n");
 printf(" :reset | :re Reset VM state (clears globals)\n");
 printf(" :dump | :du | :globals | :gl Dump current globals\n");
 printf(" :globals [pattern] Dump globals filtering by value substring\n");
 printf(" :vars | :v [pattern] Alias for :globals\n");
 printf(" :clear | :cl Clear current input buffer\n");
 printf(" :print | :pr Show current buffer\n");
 printf(" :run | :ru [file] Execute current buffer or the given file immediately\n");
 printf(" :profile | :pf Execute buffer and show timing + instruction count\n");
 printf(" :save | :sa <file> Save current buffer to file\n");
 printf(" :load | :lo <file> Load file into buffer (does not run)\n");
 printf(" :paste | :pa [run] Enter paste mode; end with a single '.' line (optional 'run')\n");
 printf(" :history | :hi [N] Show last N lines of history (default 50)\n");
 printf(" :time | :ti on|off|toggle Toggle/enable/disable timing\n");
 printf(" :env | :en [NAME[=VALUE]] Get or set environment variable\n");
 printf(" :backtrace | :bt | :ba Show backtrace of VM frames (most recent first)\n");
 printf(" :frame | :fr N Select frame N for :locals/:list/:disasm (default: top)\n");
 printf(" :list | :li [±K] Show K lines of source around current frame line (default 5)\n");
 printf(" :disasm | :di [±N] Disassemble around current frame ip (default 5)\n");
 printf(" :mdump | :md WHAT [offset [len]] [raw] [to <file>] Dump VM memory region\n");
 printf(" WHAT = code | stack | globals | consts\n");
 printf(" 'raw' writes binary bytes instead of a formatted hexdump\n");
 printf(" :stack | :st [N] Show top N (default all) stack values\n");
 printf(" :top | :to Show the top of the VM stack\n");
 printf(" :locals | :lc [FRAME] Show locals of frame (default: selected frame)\n");
 printf(" :printv | :pv WHAT Print value: local[i] | stack[i] | global[i]\n");
 printf(" :break | :br [file:]line Set a breakpoint (default file = current frame file)\n");
 printf(" :info | :in breaks List breakpoints\n");
 printf(" :delete | :de ID Delete breakpoint by ID\n");
 printf(" :clear breaks | :cb Remove all breakpoints\n");
 printf(" :cont | :co Continue execution (exit REPL if in debug stop)\n");
 printf(" :step | :sp Step one instruction\n");
 printf(" :next | :ne Step over (current frame)\n");
 printf(" :finish | :fi Run until the current frame returns\n");
}

static char *read_entire_file(const char *path, size_t *out_len) {
 FILE *f = fopen(path, "rb");
 if (!f) return NULL;
 if (fseek(f, 0, SEEK_END) != 0) {
 fclose(f);
 return NULL;
 }
 long sz = ftell(f);
 if (sz < 0) {
 fclose(f);
 return NULL;
 }
 rewind(f);
 char *buf = (char *)malloc((size_t)sz + 1);
 if (!buf) {
 fclose(f);
 return NULL;
 }
 size_t n = fread(buf, 1, (size_t)sz, f);
 fclose(f);
 buf[n] = '\0';
 if (out_len) *out_len = n;
 return buf;
}

static int write_entire_file(const char *path, const char *data, size_t len) {
 FILE *f = fopen(path, "wb");
 if (!f) return 0;
 size_t n = fwrite(data, 1, len, f);
 fclose(f);
 return n == len;
}

/* ---------- REPL command matching helper ---------- */
static int cmd_is_one_of(const char *cmd, const char *const names[]) {
 if (!cmd || !*cmd) return 0;
 for (int i = 0; names[i] != NULL; ++i) {
 if (strcmp(cmd, names[i]) == 0) return 1;
 }
 return 0;
}

/* ---------- Hexdump helper ---------- */
static void hexdump_to(FILE *out, const unsigned char *data, size_t len, size_t base_off) {
 if (!out || !data || len == 0) return;
 const size_t width = 16;
 char ascii[17];
 ascii[16] = '\0';
 for (size_t i = 0; i < len; i += width) {
 size_t chunk = (len - i < width) ? (len - i) : width;
 /* address */
 fprintf(out, "%08zx ", base_off + i);
 /* hex bytes */
 for (size_t j = 0; j < width; ++j) {
 if (j < chunk) {
 fprintf(out, "%02x ", data[i + j]);
 unsigned char c = data[i + j];
 ascii[j] = (c >= 32 && c <= 126) ? (char)c : '.';
 } else {
 fputs(" ", out);
 ascii[j] = ' ';
 }
 if (j == 7) fputc(' ', out); /* extra space between 8-byte halves */
 }
 ascii[chunk < width ? chunk : width] = '\0';
 fprintf(out, " |%s|\n", ascii);
 }
}

static void print_last_n_lines(const char *path, int n) {
 if (n <= 0) n = 50;
 size_t flen = 0;
 char *content = read_entire_file(path, &flen);
 if (!content) {
 printf("No history available.\n");
 return;
 }
 int lines = 0;
 for (size_t i = flen; i > 0; --i) {
 if (content[i - 1] == '\n') {
 lines++;
 if (lines > n) {
 content[i] = '\0';
 printf("%s", content + i);
 free(content);
 return;
 }
 }
 }
 printf("%s", content);
 free(content);
}

static void append_history(FILE *hist, const char *buffer) {
 if (!hist || !buffer) return;
 fputs(buffer, hist);
 if (buffer[0] && buffer[strlen(buffer) - 1] != '\n') fputc('\n', hist);
 fflush(hist);
}

/* ---------- Env helpers ---------- */
static void env_show_usage(void) {
 printf("Usage:\n");
 printf(" :env NAME Show environment variable NAME\n");
 printf(" :env NAME=VALUE Set environment variable NAME to VALUE\n");
 printf(" :env Show this usage\n");
}

static void env_get(const char *name) {
 const char *v = getenv(name);
 if (v)
 printf("%s=%s\n", name, v);
 else
 printf("%s is not set\n", name);
}

static void env_set(const char *name, const char *value) {
#ifdef _WIN32
 if (_putenv_s(name, value ? value : "") != 0) {
 printf("Failed to set %s\n", name);
 }
#else
 if (setenv(name, value ? value : "", 1) != 0) {
 printf("Failed to set %s\n", name);
 }
#endif
}

/* ---------- REPL Entry ---------- */

int fun_run_repl(VM *vm) {
 int repl_timing = 0;
 int selected_frame = -1; /* -1 means use current top frame */

 printf("Fun %s REPL\n", FUN_VERSION);
 printf("Type :help for commands. Submit an empty line to run.\n");

 /* Load stdlib symbols for completion */
 {
 char libdir[PATH_MAX];
 const char *envlib = getenv("FUN_LIB_DIR");
 if (envlib && *envlib) {
 snprintf(libdir, sizeof(libdir), "%s", envlib);
 } else {
#ifdef DEFAULT_LIB_DIR
 snprintf(libdir, sizeof(libdir), "%s", DEFAULT_LIB_DIR);
#else
 snprintf(libdir, sizeof(libdir), "%s", "lib");
#endif
 }
 /* strip trailing slash if present, not strictly necessary */
 size_t L = strlen(libdir);
 if (L > 1 && libdir[L - 1] == '/') libdir[L - 1] = '\0';
 load_stdlib_symbols(libdir);
 }

 char *buffer = NULL;
 size_t bufcap = 0;
 size_t buflen = 0;

 /* History setup */
 char hist_path[1024];
 FILE *hist = NULL;
 const char *home = getenv("HOME");
 if (!home) home = getenv("USERPROFILE");
 if (home) {
 snprintf(hist_path, sizeof(hist_path), "%s/.fun_history", home);
 rl_hist_load_file(hist_path);
 hist = fopen(hist_path, "a+");
 } else {
 snprintf(hist_path, sizeof(hist_path), ".fun_history");
 rl_hist_load_file(hist_path);
 hist = fopen(hist_path, "a+");
 }

 for (;;) {
 if (buflen + 1 > bufcap) {
 size_t newcap = bufcap == 0 ? 1024 : bufcap * 2;
 while (newcap < buflen + 1)
 newcap *= 2;
 buffer = (char *)realloc(buffer, newcap);
 bufcap = newcap;
 }
 buffer[buflen] = '\0';
 int indent_debt = (buflen > 0) ? compute_open_indent_blocks(buffer) : 0;

 char prompt[64];
 if (buflen == 0) {
 snprintf(prompt, sizeof(prompt), "fun> ");
 } else if (indent_debt > 0) {
 snprintf(prompt, sizeof(prompt), "...%d> ", indent_debt);
 } else {
 snprintf(prompt, sizeof(prompt), "... ");
 }

 char line[4096];
#ifndef _WIN32
 if (!read_line_edit(line, sizeof(line), prompt)) {
 puts("");
 break; // EOF
 }
#else
 fputs(prompt, stdout);
 fflush(stdout);
 if (!fgets(line, sizeof(line), stdin)) {
 puts("");
 break;
 }
#endif
 if (hist) {
 const char *lp = line;
 int only_nl = 1;
 while (*lp) {
 if (*lp != '\n' && *lp != '\r') {
 only_nl = 0;
 break;
 }
 lp++;
 }
 if (!only_nl) append_history(hist, line);
 }

 if (line[0] == ':') {
 char cmd[64] = {0};
 char arg[2048] = {0};
 sscanf(line, ":%63s %2047[^\n]", cmd, arg);

 if (cmd_is_one_of(cmd, (const char *[]){"quit", "q", "qu", "exit", NULL})) {
 break;
 } else if (cmd_is_one_of(cmd, (const char *[]){"help", "h", NULL})) {
 show_repl_help();
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"reset", "re", NULL})) {
 vm_reset(vm);
 printf("VM state reset.\n");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"dump", "du", NULL})) {
 vm_dump_globals(vm);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"globals", "vars", "gl", "v", "va", NULL})) {
 const char *pattern = lstrip(arg);
 int filtered = (pattern && *pattern);
 printf("=== globals%s%s ===\n", filtered ? " matching '" : "", filtered ? pattern : "");
 if (filtered) printf("'\n");
 for (int i = 0; i < MAX_GLOBALS; ++i) {
 if (vm->globals[i].type == VAL_NIL) continue;
 char *sv = value_to_string_alloc(&vm->globals[i]);
 if (!filtered || (sv && strstr(sv, pattern))) {
 printf("[%d] %s\n", i, sv ? sv : "nil");
 }
 free(sv);
 }
 printf("===============\n");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"clear", "cl", NULL})) {
 buflen = 0;
 printf("(buffer cleared)\n");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"print", "pr", NULL})) {
 if (buflen == 0)
 printf("(buffer empty)\n");
 else {
 if (buflen >= bufcap) {
 buffer = (char *)realloc(buffer, buflen + 1);
 bufcap = buflen + 1;
 }
 buffer[buflen] = '\0';
 printf("%s", buffer);
 if (buflen > 0 && buffer[buflen - 1] != '\n') printf("\n");
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"run", "ru", "profile", "pf", NULL})) {
 int is_profile = cmd_is_one_of(cmd, (const char *[]){"profile", "pf", NULL});
 // 'arg' is a fixed-size local array, so its address is always non-null.
 // Only check whether it contains a non-empty string.
 int from_file = (arg[0] != '\0');

 const char *src = NULL;
 char *filebuf = NULL;
 if (from_file) {
 size_t flen = 0;
 filebuf = read_entire_file(arg, &flen);
 if (!filebuf) {
 printf("Failed to load '%s'\n", arg);
 continue;
 }
 src = filebuf;
 } else {
 if (buflen == 0) {
 printf("(buffer empty)\n");
 continue;
 }
 if (buflen + 1 > bufcap) {
 buffer = (char *)realloc(buffer, buflen + 1);
 bufcap = buflen + 1;
 }
 buffer[buflen] = '\0';
 src = buffer;
 }

 clock_t t_parse0 = 0, t_parse1 = 0, t_run0 = 0, t_run1 = 0;
 if (is_profile) t_parse0 = clock();
 Bytecode *bc = parse_string_to_bytecode(src);
 if (is_profile) t_parse1 = clock();

 if (bc) {
 if (repl_timing || is_profile) t_run0 = clock();
 vm_run(vm, bc);
 if (repl_timing || is_profile) t_run1 = clock();

 if (is_profile) {
 double ms_parse = (double)(t_parse1 - t_parse0) * 1000.0 / (double)CLOCKS_PER_SEC;
 double ms_run = (double)(t_run1 - t_run0) * 1000.0 / (double)CLOCKS_PER_SEC;
 printf("[profile] parse: %.2f ms, run: %.2f ms, total: %.2f ms, instr: %lld\n",
 ms_parse, ms_run, ms_parse + ms_run, vm->instr_count);
 } else if (repl_timing) {
 double ms = (double)(t_run1 - t_run0) * 1000.0 / (double)CLOCKS_PER_SEC;
 printf("[time] %.2f ms\n", ms);
 }

 vm_print_output(vm);
 vm_clear_output(vm);
 bytecode_free(bc);
 if (!from_file) append_history(hist, buffer);
 } else {
 int line_no = 0, col_no = 0;
 char emsg[256];
 if (parser_last_error(emsg, sizeof(emsg), &line_no, &col_no)) {
 printf("Parse error at %d:%d: %s\n", line_no, col_no, emsg);
 int cur_line = 1;
 const char *p = src ? src : buffer;
 while (*p && cur_line < line_no) {
 if (*p == '\n') cur_line++;
 p++;
 }
 const char *line_start = p;
 while (*p && *p != '\n')
 p++;
 fwrite(line_start, 1, (size_t)(p - line_start), stdout);
 printf("\n");
 for (int i = 1; i < col_no; ++i)
 putchar(' ');
 printf("^\n");
#ifdef FUN_DEBUG
 if (hist && !from_file) {
 fprintf(hist, "// ERROR %d:%d: %s\n", line_no, col_no, emsg);
 fflush(hist);
 }
#endif
 } else {
 printf("Parse error.\n");
#ifdef FUN_DEBUG
 if (hist && !from_file) {
 fprintf(hist, "// ERROR: parse error\n");
 fflush(hist);
 }
#endif
 }
 }
 if (from_file) {
 free(filebuf);
 } else {
 buflen = 0; /* keep behavior: clear buffer only when running current buffer */
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"save", "sa", NULL})) {
 if (arg[0] == '\0') {
 printf("Usage: :save <file>\n");
 continue;
 }
 if (buflen == 0) {
 printf("(buffer empty)\n");
 continue;
 }
 if (!write_entire_file(arg, buffer, buflen)) {
 printf("Failed to save to '%s'\n", arg);
 } else {
 printf("Saved %zu bytes to '%s'\n", buflen, arg);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"load", "lo", NULL})) {
 if (arg[0] == '\0') {
 printf("Usage: :load <file>\n");
 continue;
 }
 size_t flen = 0;
 char *filebuf = read_entire_file(arg, &flen);
 if (!filebuf) {
 printf("Failed to load '%s'\n", arg);
 continue;
 }
 if (flen + 1 > bufcap) {
 size_t newcap = flen + 1;
 buffer = (char *)realloc(buffer, newcap);
 bufcap = newcap;
 }
 memcpy(buffer, filebuf, flen);
 buflen = flen;
 buffer[buflen] = '\0';
 free(filebuf);
 printf("Loaded %zu bytes into buffer. Use :run or submit an empty line to execute.\n", buflen);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"paste", "pa", NULL})) {
 int run_after = 0;
 const char *opt = lstrip(arg);
 if (opt && (strcmp(opt, "run") == 0 || strcmp(opt, "exec") == 0)) run_after = 1;
 printf("(paste mode: end with single '.' line)%s\n", run_after ? " [will run]" : "");
 for (;;) {
 fputs("... paste> ", stdout);
 fflush(stdout);
 char pline[8192];
 if (!fgets(pline, sizeof(pline), stdin)) {
 puts("");
 break;
 }
 if ((strcmp(pline, ".\n") == 0) || (strcmp(pline, ".\r\n") == 0) || (strcmp(pline, ".") == 0)) {
 break;
 }
 size_t pl = strlen(pline);
 if (buflen + pl + 1 > bufcap) {
 size_t newcap = bufcap == 0 ? 1024 : bufcap * 2;
 while (newcap < buflen + pl + 1)
 newcap *= 2;
 buffer = (char *)realloc(buffer, newcap);
 bufcap = newcap;
 }
 memcpy(buffer + buflen, pline, pl);
 buflen += pl;
 }
 if (run_after) {
 if (buflen + 1 > bufcap) {
 buffer = (char *)realloc(buffer, buflen + 1);
 bufcap = buflen + 1;
 }
 buffer[buflen] = '\0';
 Bytecode *bc = parse_string_to_bytecode(buffer);
 if (bc) {
 clock_t t0 = clock();
 vm_run(vm, bc);
 clock_t t1 = clock();
 double ms = (double)(t1 - t0) * 1000.0 / (double)CLOCKS_PER_SEC;
 printf("[time] %.2f ms\n", ms);
 vm_print_output(vm);
 vm_clear_output(vm);
 bytecode_free(bc);
 append_history(hist, buffer);
 } else {
 int line_no = 0, col_no = 0;
 char emsg[256];
 if (parser_last_error(emsg, sizeof(emsg), &line_no, &col_no)) {
 printf("Parse error at %d:%d: %s\n", line_no, col_no, emsg);
#ifdef FUN_DEBUG
 if (hist) {
 fprintf(hist, "// ERROR %d:%d: %s\n", line_no, col_no, emsg);
 fflush(hist);
 }
#endif
 } else {
 printf("Parse error.\n");
#ifdef FUN_DEBUG
 if (hist) {
 fprintf(hist, "// ERROR: parse error\n");
 fflush(hist);
 }
#endif
 }
 }
 buflen = 0;
 } else {
 printf("(pasted %zu bytes into buffer)\n", buflen);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"history", "hi", NULL})) {
 int n = 50;
 if (arg[0] != '\0') n = atoi(arg);
 if (n <= 0) n = 50;
 print_last_n_lines(hist_path, n);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"time", "ti", NULL})) {
 if (strcmp(lstrip(arg), "on") == 0)
 repl_timing = 1;
 else if (strcmp(lstrip(arg), "off") == 0)
 repl_timing = 0;
 else if (strcmp(lstrip(arg), "toggle") == 0)
 repl_timing = !repl_timing;
 else {
 printf("Usage: :time on|off|toggle (currently %s)\n", repl_timing ? "on" : "off");
 continue;
 }
 printf("Timing %s\n", repl_timing ? "enabled" : "disabled");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"env", "en", NULL})) {
 const char *spec = lstrip(arg);
 if (!spec || *spec == '\0') {
 env_show_usage();
 continue;
 }
 const char *eq = strchr(spec, '=');
 if (!eq) {
 env_get(spec);
 } else {
 char name[256];
 size_t nlen = (size_t)(eq - spec);
 if (nlen >= sizeof(name)) nlen = sizeof(name) - 1;
 memcpy(name, spec, nlen);
 name[nlen] = '\0';
 const char *val = eq + 1;
 env_set(name, val);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"backtrace", "bt", "ba", NULL})) {
 if (vm->fp < 0) {
 printf("(no frames)\n");
 continue;
 }
 printf("Backtrace (most recent call first):\n");
 for (int i = vm->fp; i >= 0; --i) {
 Frame *f = &vm->frames[i];
 const char *fname = (f->fn && f->fn->name) ? f->fn->name : "<entry>";
 const char *sfile = (f->fn && f->fn->source_file) ? f->fn->source_file : "<unknown>";
 int ip = f->ip - 1;
 printf(" #%d %s at %s ip=%d line=%d\n", i, fname, sfile, ip, vm->current_line);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"stack", "st", NULL})) {
 int n = -1;
 const char *p = lstrip(arg);
 if (p && *p) n = atoi(p);
 int count = vm->sp + 1;
 if (count <= 0) {
 printf("(stack empty)\n");
 continue;
 }
 int start = 0;
 if (n > 0 && n < count) start = count - n;
 printf("Stack size=%d\n", count);
 for (int i = start; i < count; ++i) {
 char *sv = value_to_string_alloc(&vm->stack[i]);
 printf("[%d] %s\n", i, sv ? sv : "nil");
 free(sv);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"locals", "lc", NULL})) {
 int idx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 const char *p = lstrip(arg);
 if (p && *p) {
 int v = atoi(p);
 if (v >= 0 && v <= vm->fp) idx = v;
 }
 if (idx < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *f = &vm->frames[idx];
 const char *fname = (f->fn && f->fn->name) ? f->fn->name : "<entry>";
 printf("Locals in frame #%d (%s):\n", idx, fname);
 int any = 0;
 for (int i = 0; i < MAX_FRAME_LOCALS; ++i) {
 if (f->locals[i].type != VAL_NIL) {
 char *sv = value_to_string_alloc(&f->locals[i]);
 printf(" %d: %s\n", i, sv ? sv : "nil");
 free(sv);
 any = 1;
 }
 }
 if (!any) printf(" (no non-nil locals)\n");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"frame", "fr", NULL})) {
 const char *p = lstrip(arg);
 if (!p || !*p) {
 printf("Usage: :frame N\n");
 continue;
 }
 int v = atoi(p);
 if (v < 0 || v > vm->fp) {
 printf("Invalid frame index. Current top is %d\n", vm->fp);
 continue;
 }
 selected_frame = v;
 Frame *f = &vm->frames[selected_frame];
 const char *fname = (f->fn && f->fn->name) ? f->fn->name : "<entry>";
 const char *sfile = (f->fn && f->fn->source_file) ? f->fn->source_file : "<unknown>";
 printf("Selected frame #%d: %s (%s)\n", selected_frame, fname, sfile);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"list", "li", NULL})) {
 int k = 5;
 const char *p = lstrip(arg);
 if (p && *p) k = atoi(p);
 if (k <= 0) k = 5;
 int idx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (idx < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *f = &vm->frames[idx];
 if (!f->fn || !f->fn->source_file) {
 printf("(no source info)\n");
 continue;
 }
 /* derive current line for this frame by scanning LINE markers up to ip-1 */
 int line = vm->current_line;
 int upto = f->ip - 1;
 if (upto < 0) upto = 0;
 for (int i = 0; i <= upto && i < f->fn->instr_count; ++i) {
 Instruction ins = f->fn->instructions[i];
 if (ins.op == OP_LINE) line = ins.operand;
 }
 const char *path = f->fn->source_file;
 /* Map to included file if the current line belongs to an included chunk */
 char mapped_path[1024];
 int mapped_line = line;
 if (map_expanded_line_to_include_path(path, line, mapped_path, sizeof(mapped_path), &mapped_line)) {
 path = mapped_path;
 line = mapped_line;
 }
 size_t flen = 0;
 char *src = read_entire_file(path, &flen);
 if (!src) {
 printf("Unable to read %s\n", path);
 continue;
 }
 int start = line - k;
 if (start < 1) start = 1;
 int end = line + k;
 int cur = 1;
 const char *s = src;
 while (*s && cur <= end) {
 const char *ls = s;
 while (*s && *s != '\n')
 s++;
 int print = (cur >= start && cur <= end);
 if (print) {
 printf("%c %5d | ", (cur == line ? '>' : ' '), cur);
 fwrite(ls, 1, (size_t)(s - ls), stdout);
 printf("\n");
 }
 if (*s == '\n') s++;
 cur++;
 }
 free(src);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"disasm", "disassemble", "di", NULL})) {
 int n = 5;
 const char *p = lstrip(arg);
 if (p && *p) n = atoi(p);
 if (n <= 0) n = 5;
 int idx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (idx < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *f = &vm->frames[idx];
 if (!f->fn) {
 printf("(no function)\n");
 continue;
 }

 /* Ensure we have a valid instruction buffer */
 if (f->fn->instr_count <= 0 || f->fn->instructions == NULL) {
 printf("(no instructions)\n");
 continue;
 }

 int count = f->fn->instr_count;
 int curip = f->ip - 1;
 if (curip < 0) curip = 0;
 if (curip >= count) curip = count - 1;

 int from = curip - n;
 if (from < 0) from = 0;
 int to = curip + n;
 if (to >= count) to = count - 1;
 if (to < from) { /* nothing to show */
 continue;
 }

 for (int i = from; i <= to; ++i) {
 Instruction ins = f->fn->instructions[i];
 const char *opname = opcode_is_valid(ins.op) ? opcode_names[ins.op] : "???";
 printf("%c %6d: %-14s %d\n", (i == curip ? '>' : ' '), i, opname, ins.operand);
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"mdump", "md", NULL})) {
 /* Syntax: :mdump WHAT [offset [len]] [raw] [to <file>]
 WHAT: code | stack | globals | consts
 'raw' writes binary bytes instead of a formatted hexdump */
 const char *p = lstrip(arg);
 if (!p || !*p) {
 printf("Usage: :mdump WHAT [offset [len]] [raw] [to <file>]\n");
 printf(" WHAT = code | stack | globals | consts\n");
 printf(" 'raw' writes binary bytes instead of a formatted hexdump\n");
 continue;
 }

 char what[32];
 int consumed = 0;
 if (sscanf(p, "%31s %n", what, &consumed) != 1) {
 printf("Usage: :mdump WHAT [offset [len]] [raw] [to <file>]\n");
 continue;
 }
 p += consumed;

 size_t off = 0;
 size_t len = (size_t)-1; /* default later to clamp */
 int want_raw = 0; /* output raw bytes instead of hexdump */

 /* parse optional off */
 while (*p == ' ' || *p == '\t')
 p++;
 if (*p && (isdigit((unsigned char)*p))) {
 char *endp = NULL;
 long long v = strtoll(p, &endp, 10);
 if (endp && endp != p && v >= 0) {
 off = (size_t)v;
 p = endp;
 }
 }
 /* parse optional len */
 while (*p == ' ' || *p == '\t')
 p++;
 if (*p && (isdigit((unsigned char)*p))) {
 char *endp = NULL;
 long long v = strtoll(p, &endp, 10);
 if (endp && endp != p && v >= 0) {
 len = (size_t)v;
 p = endp;
 }
 }

 /* optional: 'raw' keyword */
 while (*p == ' ' || *p == '\t')
 p++;
 if (strncmp(p, "raw", 3) == 0 && (p[3] == '\0' || isspace((unsigned char)p[3]))) {
 want_raw = 1;
 p += 3;
 }

 /* optional: to <file> */
 while (*p == ' ' || *p == '\t')
 p++;
 int to_file = 0;
 char path[PATH_MAX];
 path[0] = '\0';
 if (strncmp(p, "to", 2) == 0 && (p[2] == '\0' || isspace((unsigned char)p[2]))) {
 p += 2;
 while (*p == ' ' || *p == '\t')
 p++;
 if (!*p) {
 printf("Missing <file> after 'to'\n");
 continue;
 }
 /* read until whitespace end or end of string; simple paths without spaces */
 size_t i = 0;
 while (*p && !isspace((unsigned char)*p) && i + 1 < sizeof(path))
 path[i++] = *p++;
 path[i] = '\0';
 if (path[0] == '\0') {
 printf("Invalid file path\n");
 continue;
 }
 to_file = 1;
 }

 const unsigned char *base = NULL;
 size_t total = 0;
 int ok_region = 1;

 if (strcmp(what, "code") == 0) {
 int idx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (idx < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *fr = &vm->frames[idx];
 if (!fr->fn || fr->fn->instr_count <= 0 || fr->fn->instructions == NULL) {
 printf("(no code to dump)\n");
 continue;
 }
 base = (const unsigned char *)fr->fn->instructions;
 total = (size_t)fr->fn->instr_count * sizeof(Instruction);
 } else if (strcmp(what, "consts") == 0) {
 int idx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (idx < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *fr = &vm->frames[idx];
 if (!fr->fn || fr->fn->const_count <= 0 || fr->fn->constants == NULL) {
 printf("(no constants to dump)\n");
 continue;
 }
 base = (const unsigned char *)fr->fn->constants;
 total = (size_t)fr->fn->const_count * sizeof(Value);
 } else if (strcmp(what, "stack") == 0) {
 int count = vm->sp + 1;
 if (count <= 0) {
 printf("(stack empty)\n");
 continue;
 }
 base = (const unsigned char *)vm->stack;
 total = (size_t)count * sizeof(Value);
 } else if (strcmp(what, "globals") == 0) {
 base = (const unsigned char *)vm->globals;
 total = (size_t)MAX_GLOBALS * sizeof(Value);
 } else {
 ok_region = 0;
 }

 if (!ok_region) {
 printf("Unknown region '%s'. Use one of: code, stack, globals, consts\n", what);
 continue;
 }
 if (!base || total == 0) {
 printf("(nothing to dump)\n");
 continue;
 }

 if (off >= total) {
 printf("(empty range: offset beyond end)\n");
 continue;
 }
 size_t avail = total - off;
 if (len == (size_t)-1 || len == 0 || len > avail) {
 /* default to min(256, avail) */
 len = avail < 256 ? avail : 256;
 }

 if (!to_file) {
 if (want_raw) {
 /* Write raw bytes directly to stdout with no header */
 fwrite(base + off, 1, len, stdout);
 fflush(stdout);
 } else {
 printf("Hexdump %s: total=%zu, offset=%zu, len=%zu\n", what, total, off, len);
 hexdump_to(stdout, base + off, len, off);
 }
 } else {
 FILE *fout = fopen(path, "wb");
 if (!fout) {
 printf("Failed to open '%s' for writing\n", path);
 continue;
 }
 if (want_raw) {
 fwrite(base + off, 1, len, fout);
 fclose(fout);
 printf("Wrote raw bytes (%zu from %s) to %s\n", len, what, path);
 } else {
 hexdump_to(fout, base + off, len, off);
 fclose(fout);
 printf("Wrote hexdump (%zu bytes from %s) to %s\n", len, what, path);
 }
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"printv", "pv", NULL})) {
 const char *spec = lstrip(arg);
 if (!spec || !*spec) {
 printf("Usage: :printv local[i] | stack[i] | global[i]\n");
 continue;
 }
 int idx = -1;
 if (sscanf(spec, "local[%d]", &idx) == 1) {
 int fidx = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (fidx < 0 || idx < 0 || idx >= MAX_FRAME_LOCALS) {
 printf("(out of range)\n");
 continue;
 }
 Frame *f = &vm->frames[fidx];
 char *sv = value_to_string_alloc(&f->locals[idx]);
 printf("%s\n", sv ? sv : "nil");
 free(sv);
 } else if (sscanf(spec, "stack[%d]", &idx) == 1) {
 if (idx < 0 || idx > vm->sp) {
 printf("(out of range)\n");
 continue;
 }
 char *sv = value_to_string_alloc(&vm->stack[idx]);
 printf("%s\n", sv ? sv : "nil");
 free(sv);
 } else if (sscanf(spec, "global[%d]", &idx) == 1) {
 if (idx < 0 || idx >= MAX_GLOBALS) {
 printf("(out of range)\n");
 continue;
 }
 char *sv = value_to_string_alloc(&vm->globals[idx]);
 printf("%s\n", sv ? sv : "nil");
 free(sv);
 } else {
 printf("Usage: :printv local[i] | stack[i] | global[i]\n");
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"top", "to", NULL})) {
 if (vm->sp < 0) {
 printf("(stack empty)\n");
 continue;
 }
 char *sv = value_to_string_alloc(&vm->stack[vm->sp]);
 printf("%s\n", sv ? sv : "nil");
 free(sv);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"break", "br", NULL})) {
 const char *p = lstrip(arg);
 if (!p || !*p) {
 printf("Usage: :break [file:]line\n");
 continue;
 }
 const char *colon = strchr(p, ':');
 char filebuf[1024];
 int line = 0;
 if (colon) {
 size_t fl = (size_t)(colon - p);
 if (fl >= sizeof(filebuf)) fl = sizeof(filebuf) - 1;
 memcpy(filebuf, p, fl);
 filebuf[fl] = '\0';
 line = atoi(colon + 1);
 } else {
 int idxf = (selected_frame >= 0 && selected_frame <= vm->fp) ? selected_frame : vm->fp;
 if (idxf < 0) {
 printf("(no current frame)\n");
 continue;
 }
 Frame *f = &vm->frames[idxf];
 const char *sf = (f->fn && f->fn->source_file) ? f->fn->source_file : NULL;
 if (!sf) {
 printf("(no current source file)\n");
 continue;
 }
 snprintf(filebuf, sizeof(filebuf), "%s", sf);
 line = atoi(p);
 }
 if (line <= 0) {
 printf("Invalid line\n");
 continue;
 }
 int id = vm_debug_add_breakpoint(vm, filebuf, line);
 if (id >= 0)
 printf("Breakpoint %d set at %s:%d\n", id, filebuf, line);
 else
 printf("Failed to set breakpoint\n");
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"info", "in", NULL})) {
 const char *what = lstrip(arg);
 if (what && strcmp(what, "breaks") == 0) {
 vm_debug_list_breakpoints(vm);
 } else {
 printf("Usage: :info breaks\n");
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"delete", "de", NULL})) {
 int id = atoi(lstrip(arg));
 if (vm_debug_delete_breakpoint(vm, id))
 printf("Deleted breakpoint %d\n", id);
 else
 printf("No such breakpoint %d\n", id);
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"cb", NULL})) {
 vm_debug_clear_breakpoints(vm);
 printf("Cleared all breakpoints\n");
 continue;
 } else if (strcmp(cmd, "clear") == 0) {
 const char *what = lstrip(arg);
 if (what && strcmp(what, "breaks") == 0) {
 vm_debug_clear_breakpoints(vm);
 printf("Cleared all breakpoints\n");
 } else {
 printf("Usage: :clear breaks\n");
 }
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"cont", "continue", "co", NULL})) {
 vm_debug_request_continue(vm);
 printf("Continuing...\n");
 if (vm->on_error_repl) return 0; /* exit REPL to continue execution */
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"step", "sp", NULL})) {
 vm_debug_request_step(vm);
 printf("Stepping one instruction...\n");
 if (vm->on_error_repl) return 0;
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"next", "ne", NULL})) {
 vm_debug_request_next(vm);
 printf("Stepping over...\n");
 if (vm->on_error_repl) return 0;
 continue;
 } else if (cmd_is_one_of(cmd, (const char *[]){"finish", "fi", NULL})) {
 vm_debug_request_finish(vm);
 printf("Running until current frame returns...\n");
 if (vm->on_error_repl) return 0;
 continue;
 } else {
 printf("Unknown command. Use :help\n");
 continue;
 }
 }

 if (is_blank_line(line)) {
 if (buflen == 0) continue;

 if (buflen + 1 > bufcap) {
 buffer = (char *)realloc(buffer, buflen + 1);
 bufcap = buflen + 1;
 }
 buffer[buflen] = '\0';

 int indent_debt2 = compute_open_indent_blocks(buffer);
 if (buffer_looks_incomplete(buffer) || indent_debt2 > 0) {
 if (indent_debt2 > 0) {
 printf("(incomplete, open block indent +%d)\n", indent_debt2);
 } else {
 printf("(incomplete, continue typing)\n");
 }
 continue;
 }

 Bytecode *bc = parse_string_to_bytecode(buffer);
 if (bc) {
 clock_t t0 = 0, t1 = 0;
 if (repl_timing) t0 = clock();
 vm_run(vm, bc);
 if (repl_timing) {
 t1 = clock();
 double ms = (double)(t1 - t0) * 1000.0 / (double)CLOCKS_PER_SEC;
 printf("[time] %.2f ms\n", ms);
 }
 vm_print_output(vm);
 vm_clear_output(vm);
 bytecode_free(bc);
 append_history(hist, buffer);
 } else {
 int line_no = 0, col_no = 0;
 char emsg[256];
 if (parser_last_error(emsg, sizeof(emsg), &line_no, &col_no)) {
 printf("Parse error at %d:%d: %s\n", line_no, col_no, emsg);
 int cur_line = 1;
 const char *p = buffer;
 while (*p && cur_line < line_no) {
 if (*p == '\n') cur_line++;
 p++;
 }
 const char *line_start = p;
 while (*p && *p != '\n')
 p++;
 fwrite(line_start, 1, (size_t)(p - line_start), stdout);
 printf("\n");
 for (int i = 1; i < col_no; ++i)
 putchar(' ');
 printf("^\n");
#ifdef FUN_DEBUG
 if (hist) {
 fprintf(hist, "// ERROR %d:%d: %s\n", line_no, col_no, emsg);
 fflush(hist);
 }
#endif
 } else {
 printf("Parse error.\n");
#ifdef FUN_DEBUG
 if (hist) {
 fprintf(hist, "// ERROR: parse error\n");
 fflush(hist);
 }
#endif
 }
 }
 buflen = 0;
 continue;
 }

 size_t linelen = strlen(line);
 if (buflen + linelen + 1 > bufcap) {
 size_t newcap = bufcap == 0 ? 1024 : bufcap * 2;
 while (newcap < buflen + linelen + 1)
 newcap *= 2;
 buffer = (char *)realloc(buffer, newcap);
 bufcap = newcap;
 }
 memcpy(buffer + buflen, line, linelen);
 buflen += linelen;
 }

 if (hist) fclose(hist);
 free_stdlib_symbols();
 free(buffer);
 return 0;
}

#endif /* FUN_WITH_REPL */