added preview function

sfm

@@ -83,6 +83,7 @@ INFO_MSG=""     # ephemeral message shown in botbar
 SHOW_HIDDEN=0   # 1 = show dotfiles
 SORT_MODE="name" # name | size | date
 SHOW_DETAILS=0   # 1 = show size+date column
+SHOW_PREVIEW=0   # 1 = show preview pane on right
 TRASH_DIR="${XDG_DATA_HOME:-$HOME/.local/share}/sfm-trash"
 mkdir -p "$TRASH_DIR"
 PREV_CWD=""     # last visited directory, for jumping back
@@ -432,6 +433,85 @@ render_row() {
     fi
 }
 
+draw_preview() {
+    _rows=$1; _cols=$2; _px=$3; _pw=$4
+    entry=$(get_entry "$SEL")
+    # clear preview area first
+    _r=2
+    while [ "$_r" -le $((_rows - 1)) ]; do
+        goto "$_r" "$_px"
+        printf '\033[K'
+        _r=$((_r + 1))
+    done
+    [ -z "$entry" ] && return
+    _path=$(joinpath "${entry%/}"); _path="${_path%@}"
+
+    # draw vertical divider
+    _r=2
+    while [ "$_r" -le $((_rows - 1)) ]; do
+        goto "$_r" $((_px - 1))
+        printf '%s|%s' "${CYAN}" "${RESET}"
+        _r=$((_r + 1))
+    done
+
+    case "$entry" in
+        */)
+            # directory: show entry count
+            _dc=$(ls -1 "$_path" 2>/dev/null | wc -l | tr -d '[:space:]')
+            goto 2 "$_px"
+            printf '%s[dir] %s items%s' "${CYAN}" "${_dc}" "${RESET}"
+            ;;
+        *@)
+            # symlink
+            _tgt=$(readlink "$_path" 2>/dev/null || echo "?")
+            goto 2 "$_px"
+            printf '%s[symlink]%s' "${MAGENTA}${BOLD}" "${RESET}"
+            goto 3 "$_px"
+            printf '%s-> %s%s' "${WHITE}" "${_tgt}" "${RESET}"
+            ;;
+        *)
+            # detect if text via extension or mime
+            _ext="${entry##*.}"
+            _ext=$(printf '%s' "$_ext" | tr '[:upper:]' '[:lower:]')
+            _is_text=0
+            case "$_ext" in
+                txt|md|markdown|rst|log|conf|cfg|ini|toml|yaml|yml|\
+                sh|bash|zsh|py|rb|pl|lua|js|ts|json|xml|html|htm|\
+                css|c|h|cpp|rs|go|java|php|r|sql|vim|env|gitignore|\
+                diff|patch|csv|tsv|lock|mod|sum) _is_text=1 ;;
+            esac
+            if [ "$_is_text" = "0" ] && command -v file >/dev/null 2>&1; then
+                case "$(file --mime-type -b "$_path" 2>/dev/null)" in
+                    text/*) _is_text=1 ;;
+                esac
+            fi
+            if [ "$_is_text" = "1" ]; then
+                _max_lines=$((_rows - 3))
+                _line_n=0
+                while IFS= read -r _line && [ "$_line_n" -lt "$_max_lines" ]; do
+                    # truncate to preview width
+                    if [ "${#_line}" -gt "$((_pw - 1))" ]; then
+                        _line=$(printf '%s' "$_line" | cut -c1-$((_pw - 2)))
+                        _line="${_line}~"
+                    fi
+                    goto "$((_line_n + 2))" "$_px"
+                    printf '%s%s%s' "${WHITE}" "$_line" "${RESET}"
+                    _line_n=$((_line_n + 1))
+                done < "$_path"
+                if [ "$_line_n" -eq 0 ]; then
+                    goto 2 "$_px"
+                    printf '%s(empty file)%s' "${WHITE}" "${RESET}"
+                fi
+            else
+                # binary / unknown
+                goto 2 "$_px"
+                _sz=$(ls -lh "$_path" 2>/dev/null | awk '{print $5}')
+                printf '%s[binary] %s%s' "${YELLOW}" "${_sz}" "${RESET}"
+            fi
+            ;;
+    esac
+}
+
 draw_topbar() {
     _cols=$1
     spaces=$(printf '%*s' "$_cols" '')
@@ -494,6 +574,15 @@ draw() {
     COLS=$(term_cols)
     LIST_ROWS=$((ROWS - 2))   # row 1 = topbar, row ROWS = botbar
 
+    # split layout when preview enabled
+    if [ "$SHOW_PREVIEW" = "1" ]; then
+        LIST_COLS=$((COLS / 2))
+        PREV_COL=$((LIST_COLS + 2))
+        PREV_WIDTH=$((COLS - LIST_COLS - 2))
+    else
+        LIST_COLS=$COLS
+    fi
+
     # clamp selection
     [ "$SEL" -lt 0 ] && SEL=0
     [ "$COUNT" -gt 0 ] && [ "$SEL" -ge "$COUNT" ] && SEL=$((COUNT - 1))
@@ -509,7 +598,6 @@ draw() {
     [ "$OFFSET" != "$PREV_OFFSET" ] && NEED_FULL_REDRAW=1
 
     if [ "$NEED_FULL_REDRAW" = "1" ]; then
-        # --- full repaint: move to top without erasing, overwrite every row ---
         printf '\033[H'
         draw_topbar "$COLS"
 
@@ -517,7 +605,7 @@ draw() {
         idx=$OFFSET
         while [ "$row" -le $((LIST_ROWS + 1)) ] && [ "$idx" -lt "$COUNT" ]; do
             sel=0; [ "$idx" -eq "$SEL" ] && sel=1
-            render_row "$row" "$idx" "$sel" "$COLS"
+            render_row "$row" "$idx" "$sel" "$LIST_COLS"
             row=$((row + 1))
             idx=$((idx + 1))
         done
@@ -527,18 +615,19 @@ draw() {
             printf '%s  (empty)%s%s' "${WHITE}" "${ERASE_LINE}" "${RESET}"
             row=3
         fi
-        # blank leftover rows (e.g. after entering a smaller directory)
+        # blank leftover rows
         while [ "$row" -le $((LIST_ROWS + 1)) ]; do
             goto "$row" 1
             printf '%s' "${ERASE_LINE}"
             row=$((row + 1))
         done
 
+        [ "$SHOW_PREVIEW" = "1" ] && draw_preview "$ROWS" "$COLS" "$PREV_COL" "$PREV_WIDTH"
+
         draw_botbar "$ROWS" "$COLS"
         NEED_FULL_REDRAW=0
     else
-        # --- fast path: only touch the two rows whose highlight state changed ---
+        # --- fast path ---
-        # if nothing moved, skip entirely — no flicker at boundaries
         if [ "$SEL" = "$PREV_SEL" ] && [ "$OFFSET" = "$PREV_OFFSET" ]; then
             return 2>/dev/null || true
         fi
@@ -546,12 +635,14 @@ draw() {
         new_row=$(( (SEL      - OFFSET) + 2 ))
 
         if [ "$prev_row" -ge 2 ] && [ "$prev_row" -le $((LIST_ROWS + 1)) ]; then
-            render_row "$prev_row" "$PREV_SEL" 0 "$COLS"
+            render_row "$prev_row" "$PREV_SEL" 0 "$LIST_COLS"
         fi
         if [ "$new_row" -ge 2 ] && [ "$new_row" -le $((LIST_ROWS + 1)) ]; then
-            render_row "$new_row" "$SEL" 1 "$COLS"
+            render_row "$new_row" "$SEL" 1 "$LIST_COLS"
         fi
 
+        [ "$SHOW_PREVIEW" = "1" ] && draw_preview "$ROWS" "$COLS" "$PREV_COL" "$PREV_WIDTH"
+
         draw_botbar "$ROWS" "$COLS"
     fi
 
@@ -765,7 +856,7 @@ do_help() {
     bw=$((COLS - 4))
     [ "$bw" -gt 52 ] && bw=52
     [ "$bw" -lt 36 ] && bw=36
-    bh=41
+    bh=42
     _help_bx=$(( (COLS - bw) / 2 )); [ "$_help_bx" -lt 1 ] && _help_bx=1
     _help_by=$(( (ROWS - bh) / 2 )); [ "$_help_by" -lt 1 ] && _help_by=1
     _help_iw=$((bw - 2))
@@ -787,32 +878,33 @@ do_help() {
     help_row 11 "  i     file info in status bar"
     help_row 12 "  s     cycle sort: name/size/date"
     help_row 13 "  T     toggle size/date details"
-    help_sep 14
+    help_row 14 "  P     toggle preview pane"
-    help_row 15 "  space  toggle multi-select"
+    help_sep 15
-    help_row 16 "  a      select all / deselect all"
+    help_row 16 "  space  toggle multi-select"
-    help_row 17 "  y      yank/copy  (works on selection)"
+    help_row 17 "  a      select all / deselect all"
-    help_row 18 "  x      cut        (works on selection)"
+    help_row 18 "  y      yank/copy  (works on selection)"
-    help_row 19 "  p      paste"
+    help_row 19 "  x      cut        (works on selection)"
-    help_row 20 "  d      delete     (works on selection)"
+    help_row 20 "  p      paste"
-    help_sep 21
+    help_row 21 "  d      delete     (works on selection)"
-    help_row 22 "  r   rename         R   refresh"
+    help_sep 22
-    help_row 23 "  m   make directory"
+    help_row 23 "  r   rename         R   refresh"
-    help_row 24 "  n   new file"
+    help_row 24 "  m   make directory"
-    help_row 25 "  u   trash file (safe delete)"
+    help_row 25 "  n   new file"
-    help_row 26 "  U   open trash directory"
+    help_row 26 "  u   trash file (safe delete)"
-    help_row 27 "  !   drop to shell in CWD"
+    help_row 27 "  U   open trash directory"
-    help_row 28 "  o   open with custom program"
+    help_row 28 "  !   drop to shell in CWD"
-    help_sep 29
+    help_row 29 "  o   open with custom program"
-    help_row 30 "  b   bookmark current dir"
+    help_sep 30
-    help_row 31 "  B   open bookmark picker"
+    help_row 31 "  b   bookmark current dir"
-    help_row 32 "  c   copy path to clipboard"
+    help_row 32 "  B   open bookmark picker"
-    help_row 33 "  ~   go to home directory"
+    help_row 33 "  c   copy path to clipboard"
-    help_row 34 "  \`   jump to previous directory"
+    help_row 34 "  ~   go to home directory"
-    help_sep 35
+    help_row 35 "  \`   jump to previous directory"
-    help_row 36 "  q   quit"
+    help_sep 36
-    help_row 37 "  ?   this help"
+    help_row 37 "  q   quit"
-    help_row 38 ""
+    help_row 38 "  ?   this help"
-    help_row 39 "  press any key to close..."
+    help_row 39 ""
+    help_row 40 "  press any key to close..."
 
     goto "$(( _help_by + bh ))" "$_help_bx"
     printf '%s+%s+%s' "${BOLD}${CYAN}" "$_help_hl" "${RESET}"
@@ -877,11 +969,18 @@ do_toggle_hidden() {
 
 do_toggle_details() {
     if [ "$SHOW_DETAILS" = "0" ]; then
-        SHOW_DETAILS=1
+        SHOW_DETAILS=1; INFO_MSG="details on"
-        INFO_MSG="details on"
     else
-        SHOW_DETAILS=0
+        SHOW_DETAILS=0; INFO_MSG="details off"
-        INFO_MSG="details off"
+    fi
+    NEED_FULL_REDRAW=1
+}
+
+do_toggle_preview() {
+    if [ "$SHOW_PREVIEW" = "0" ]; then
+        SHOW_PREVIEW=1; INFO_MSG="preview on"
+    else
+        SHOW_PREVIEW=0; INFO_MSG="preview off"
     fi
     NEED_FULL_REDRAW=1
 }
@@ -1385,6 +1484,7 @@ while true; do
         /)   do_search        ;;
         '.')  do_toggle_hidden   ;;
         T)    do_toggle_details  ;;
+        P)    do_toggle_preview  ;;
         i)   do_info          ;;
         '!') do_shell         ;;
         o)   do_open_with     ;;