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

# title_one_line.sh — one centered line with fade in/out in a time window
# Requires: ffmpeg with libfreetype

show_help() {
  cat <<'EOF'
Usage:
  title_one_line.sh -i INPUT -o OUTPUT --text "YOUR TEXT" [options]

Required:
  -i, --input      Input video
  -o, --output     Output video
      --text       Text to display (one line)

Timing:
  --start          Start time seconds (default: 30)
  --end            End time seconds (default: 34)
  --fade-in        Fade-in seconds (default: 0.6)
  --fade-out       Fade-out seconds (default: 0.6)

Style:
  --fs             Font size (default: 78)
  --dy             Vertical nudge in px (default: 0)  # negative = up
  --font           Font family (FontConfig), e.g. "DejaVu Sans"
  --fontfile       Path to TTF/OTF (overrides --font)
  --shadow         1 to add shadow, 0 to disable (default: 1)
  --color          Text color (default: white)

Encoding:
  --crf            x264 CRF (default: 18)
  --preset         x264 preset (default: medium)

Examples:
  title_one_line.sh -i in.mp4 -o out.mp4 --text "ROSE ASH VILLAGE HALL presents"
  title_one_line.sh -i in.mp4 -o out.mp4 --text "Summer Fête" --start 12 --end 18 --fs 90 --dy -30
EOF
}

# --- defaults ---
INPUT=""
OUTPUT=""
TEXT=""
START="30"
END="34"
FADEIN="0.6"
FADEOUT="0.6"
FS="78"
DY="0"
FONT=""
FONTFILE=""
SHADOW="1"
COLOR="white"
CRF="18"
PRESET="medium"

# --- parse args ---
[[ $# -eq 0 ]] && { show_help; exit 1; }

while [[ $# -gt 0 ]]; do
  case "$1" in
    -i|--input)   INPUT="${2:-}"; shift 2;;
    -o|--output)  OUTPUT="${2:-}"; shift 2;;
    --text)       TEXT="${2:-}"; shift 2;;
    --start)      START="${2:-}"; shift 2;;
    --end)        END="${2:-}"; shift 2;;
    --fade-in)    FADEIN="${2:-}"; shift 2;;
    --fade-out)   FADEOUT="${2:-}"; shift 2;;
    --fs)         FS="${2:-}"; shift 2;;
    --dy)         DY="${2:-}"; shift 2;;
    --font)       FONT="${2:-}"; shift 2;;
    --fontfile)   FONTFILE="${2:-}"; shift 2;;
    --shadow)     SHADOW="${2:-}"; shift 2;;
    --color)      COLOR="${2:-}"; shift 2;;
    --crf)        CRF="${2:-}"; shift 2;;
    --preset)     PRESET="${2:-}"; shift 2;;
    -h|--help)    show_help; exit 0;;
    *) echo "Unknown arg: $1"; echo; show_help; exit 1;;
  esac
done

[[ -z "$INPUT" || -z "$OUTPUT" || -z "$TEXT" ]] && { echo "Error: -i, -o and --text are required."; exit 1; }
command -v ffmpeg >/dev/null 2>&1 || { echo "Error: ffmpeg not found."; exit 1; }

# Escape text for drawtext (backslash, colon, percent, and single quote)
esc() {
  local s="$1"
  s="${s//\\/\\\\}"   # backslashes
  s="${s//:/\\:}"     # colons
  s="${s//%/\\%}"     # percent
  s="${s//\'/\\\'}"   # single quotes
  echo "$s"
}
ETEXT="$(esc "$TEXT")"

# Font options: prefer fontfile, else family, else default
FONT_OPTS=""
if [[ -n "$FONTFILE" ]]; then
  FONT_OPTS="fontfile='${FONTFILE}'"
elif [[ -n "$FONT" ]]; then
  FONT_OPTS="font='${FONT}'"
fi

# Optional shadow for contrast
SHADOW_OPTS=""
if [[ "$SHADOW" == "1" ]]; then
  SHADOW_OPTS=":shadowcolor=black@0.6:shadowx=2:shadowy=2"
fi

# Alpha expression: fade in, hold, fade out (commas escaped)
ALPHA="if(lt(t\\,${START})\\,0\\,if(lt(t\\,${START}+${FADEIN})\\,(t-${START})/${FADEIN}\\,if(lt(t\\,${END}-${FADEOUT})\\,1\\,if(lt(t\\,${END})\\,(${END}-t)/${FADEOUT}\\,0))))"

DT="drawtext=${FONT_OPTS}:text='${ETEXT}':fontcolor=${COLOR}:fontsize=${FS}${SHADOW_OPTS}:x=(w-text_w)/2:y=(h-text_h)/2+${DY}:alpha='${ALPHA}'"

VF="${DT}"

echo "Running:"
echo " ffmpeg -hide_banner -y -i '$INPUT' -vf \"$VF\" -c:v libx264 -crf $CRF -preset $PRESET -c:a copy '$OUTPUT'"

ffmpeg -hide_banner -y -i "$INPUT" -vf "$VF" -c:v libx264 -crf "$CRF" -preset "$PRESET" -c:a copy "$OUTPUT"

echo "Done: $OUTPUT"