refactor(output): centralize formatted terminal messages

Add a shared emit() helper for styled terminal output and route error(),
msg(), warn(), verbose(), and debug() through it.

This removes duplicated printf formatting across the output helpers
while keeping the existing prefixes, colors, quiet/verbose/debug gating,
and stderr handling for errors. emit() also joins additional message
arguments into a single trailing string, matching the output pattern
used by the individual helpers.

The output helpers now differ only in their prefix, color, and
visibility condition, making future formatting changes easier and less
error-prone.

1 files changed, 30 insertions, 14 deletions

diff --git a/transcode.sh b/transcode.sh
index 1fd1fe0..9fca292 100755
--- a/transcode.sh
+++ b/transcode.sh
@@ -196,41 +196,57 @@ readonly EXIT_OK EXIT_RUNTIME_FAILURE EXIT_USAGE_ERROR EXIT_CONFIG_ERROR EXIT_MI
 # functions and runtime behaviour such as displaying usage instructions.
 ###############################################################################
 
-error() {
+emit() {
+  local prefix="$1"
+  local color="$2"
+  shift 2
+
+  if [[ $# -eq 0 ]]; then
+    printf "%b%s%b\n" "${BOLD}${color}" "$prefix" "$ALL_OFF"
+    return
+  fi
+
   local mesg="$1"
   shift
-  printf "${BOLD}${RED}==> ERROR:${ALL_OFF} ${BOLD}%s${ALL_OFF} %s\n" "$mesg" "$@" >&2
+
+  local rest=""
+  if [[ $# -gt 0 ]]; then
+    printf -v rest ' %s' "$@"
+    rest="${rest# }"
+  fi
+
+  printf "%b%s%b %b%s%b" "${BOLD}${color}" "$prefix" "$ALL_OFF" "$BOLD" "$mesg" "$ALL_OFF"
+  if [[ -n "$rest" ]]; then
+    printf " %s" "$rest"
+  fi
+  printf "\n"
+}
+
+error() {
+  emit "==> ERROR:" "$RED" "$@" >&2
 }
 
 msg() {
   if [[ $QUIET -eq 0 ]]; then
-    local mesg="$1"
-    shift
-    printf "${BOLD}${GREEN}==>${ALL_OFF} ${BOLD}%s${ALL_OFF} %s\n" "$mesg" "$@"
+    emit "==>" "$GREEN" "$@"
   fi
 }
 
 warn() {
   if [[ $QUIET -eq 0 ]]; then
-    local mesg="$1"
-    shift
-    printf "${BOLD}${YELLOW}==>${ALL_OFF} ${BOLD}%s${ALL_OFF} %s\n" "$mesg" "$@"
+    emit "==>" "$YELLOW" "$@"
   fi
 }
 
 verbose() {
   if [[ $VERBOSE -eq 1 && $QUIET -eq 0 ]]; then
-    local mesg="$1"
-    shift
-    printf "${BOLD}${BLUE}==>${ALL_OFF} ${BOLD}%s${ALL_OFF} %s\n" "$mesg" "$@"
+    emit "==>" "$BLUE" "$@"
   fi
 }
 
 debug() {
   if [[ $DEBUG -eq 1 ]]; then
-    local mesg="$1"
-    shift
-    printf "${BOLD}${MAGENTA}==> DEBUG:${ALL_OFF} ${BOLD}%s${ALL_OFF} %s\n" "$mesg" "$@"
+    emit "==> DEBUG:" "$MAGENTA" "$@"
   fi
 }