Capture Slack emojis from the Wayland clipboard to disk, with optional desktop notifications and a watch mode for bulk export

capture-emoji.sh

#!/usr/bin/env bash
set -euo pipefail

## LLM-produced -- tamp those expectations down

# Usage: capture-emoji.sh [--notify]
# Reads a Slack emoji from the Wayland clipboard and saves it to the script's
# directory. Pass --notify to fire a desktop notification on success or failure.
#
# Three-way outcome:
#   success      -- emoji saved, notification fired (if --notify)
#   silent skip  -- clipboard does not contain a Slack emoji; exit 0, no notification
#   real failure -- clipboard looked like an emoji but processing broke; exit 1,
#                   failure notification fired (if --notify)

DIR="$(cd "$(dirname "$0")" && pwd)"
mkdir -p "$DIR"

# State -- initialize all before the EXIT trap is registered (set -u safety)
NOTIFY=false
NAME=""
EXT=""
OUT=""
ERROR_MSG=""
SUCCESS=false

[[ "${1:-}" == "--notify" ]] && NOTIFY=true

TMP=$(mktemp)

on_exit() {
  local rc=$?
  rm -f "$TMP"
  $NOTIFY || return
  if [[ $SUCCESS == true && $rc -eq 0 ]]; then
    notify-send \
      -a "Slack Emoji" \
      -i "$OUT" \
      -t 3000 \
      "Emoji saved" ":${NAME}: -> $(basename "$OUT")" || true
  else
    notify-send \
      -a "Slack Emoji" \
      -i dialog-error \
      -u low \
      -t 2000 \
      "Emoji capture failed" "${ERROR_MSG:-unexpected error (exit ${rc})}" || true
  fi
}

trap on_exit EXIT

# Sets ERROR_MSG, prints to stderr, and exits 1 (triggers on_exit with failure).
fail() {
  ERROR_MSG="$1"
  echo "Error: $1" >&2
  exit 1
}

# Silent skip: clipboard was cleared or selection has no usable type
[[ "${CLIPBOARD_STATE:-}" == "nil" ]] && exit 0

# Silent skip: no text/html in clipboard -- not a Slack emoji
HTML=$(wl-paste --type text/html 2>/dev/null) || exit 0
[[ -z "$HTML" ]] && exit 0

# Silent skip: no emoji markers in HTML -- not a Slack emoji
# Assumes a single <img> tag in the clipboard HTML (true for Slack web and desktop).
# Try data-stringify-emoji=":NAME:" first (Slack web), fall back to alt=":NAME:" (Slack desktop).
NAME=$(grep -oP 'data-stringify-emoji=":\K[^:]+(?=:")' <<<"$HTML" | head -1 || true)
if [[ -z "$NAME" ]]; then
  NAME=$(grep -oP 'alt=":\K[^:]+(?=:")' <<<"$HTML" | head -1 || true)
fi
[[ -z "$NAME" ]] && exit 0

# From here the clipboard looks like a Slack emoji -- failures become real errors.

SRC=$(grep -oP 'src="\K[^"]+(?=")' <<<"$HTML" | head -1 || true)
[[ -z "$SRC" ]] && fail "could not extract src URL from clipboard HTML"

# Guard: base64 data URIs are from old Slack clients and are not supported
[[ "$SRC" == data:* ]] && fail "base64 data URIs are not supported -- please use a current Slack client"

# Guard: only fetch from Slack's emoji CDN
[[ "$SRC" == https://emoji.slack-edge.com/* ]] ||
  fail "unexpected src URL (expected https://emoji.slack-edge.com/...): $SRC"

# Guard: prevent path traversal via malformed emoji names
[[ "$NAME" =~ ^[A-Za-z0-9_+\-]+$ ]] || fail "invalid emoji name: $NAME"

EXT="${SRC##*.}"

if [[ "$EXT" == gif ]]; then
  curl -sL --fail "$SRC" -o "$TMP" || fail "failed to download $SRC"
  FRAMES=$(identify "$TMP" 2>/dev/null | wc -l)
  if [[ "${FRAMES:-0}" -gt 1 ]]; then
    OUT="$DIR/$NAME.gif"
    cp "$TMP" "$OUT"
  else
    echo "Warning: .gif URL yielded a single frame; saving as PNG" >&2
    EXT="png"
    OUT="$DIR/$NAME.png"
    convert "$TMP" "$OUT"
  fi
else
  EXT="png"
  OUT="$DIR/$NAME.png"
  wl-paste --type image/png >"$OUT" 2>/dev/null ||
    fail "could not read image/png from clipboard"
  read -r W H < <(identify -format "%w %h\n" "$OUT" 2>/dev/null | head -1) || true
  if [[ -z "${W:-}" ]] || [[ "$W" -lt 8 ]] || [[ "$H" -lt 8 ]]; then
    rm -f "$OUT"
    fail "clipboard PNG appears invalid (dimensions: ${W:-?}x${H:-?})"
  fi
fi

SUCCESS=true
echo "Saved: $OUT"

watch-emoji.sh

#!/usr/bin/env bash
set -euo pipefail

# Watches the Wayland clipboard and captures any Slack emoji that is copied.
# Fires a desktop notification on success or failure (via capture-emoji.sh --notify).
# Press Ctrl-C to stop.

DIR="$(cd "$(dirname "$0")" && pwd)"

echo "Watching clipboard for Slack emojis... (Ctrl-C to stop)"
exec wl-paste --watch "$DIR/capture-emoji.sh" --notify