#!/usr/bin/env bash
# detect_pink_intro_hsv.sh <file.mp4> [duration_s] [fps] [hue_min] [hue_max] [sat_min] [val_min] [min_ratio]
#
# Detect a magenta/pink intro by averaging frames to 1x1 and classifying in HSV.
#
# Defaults:
#   duration_s = 1.0
#   fps        = 6
#   hue_min    = 285     # degrees, magenta band start
#   hue_max    = 330     # degrees, magenta band end
#   sat_min    = 0.35    # require some saturation
#   val_min    = 0.35    # avoid very dark frames
#   min_ratio  = 0.6     # % of sampled frames that must be pink-ish
#
# Exit codes: 0 detected, 1 not detected, 2 usage error

set -euo pipefail

file="${1:-}"
duration="${2:-1.0}"
sample_fps="${3:-6}"
HMIN="${4:-285}"
HMAX="${5:-330}"
SMIN="${6:-0.35}"
VMIN="${7:-0.35}"
MIN_RATIO="${8:-0.6}"

if [[ -z "$file" ]]; then
  echo "Usage: $0 <file.mp4> [duration_s] [fps] [hue_min] [hue_max] [sat_min] [val_min] [min_ratio]" >&2
  exit 2
fi
[[ -f "$file" ]] || { echo "File not found: $file" >&2; exit 2; }

# Stream 1x1 RGB for sampled frames; each frame = 3 bytes. Parse with od+awk.
summary="$(
  LC_ALL=C ffmpeg -hide_banner -v error \
    -i "$file" -t "$duration" \
    -vf "fps=${sample_fps},scale=1:1:flags=area,format=rgb24" \
    -f rawvideo - 2>/dev/null \
  | od -An -tu1 -w3 \
  | awk -v HMIN="$HMIN" -v HMAX="$HMAX" -v SMIN="$SMIN" -v VMIN="$VMIN" '
      function max(a,b){return a>b?a:b}
      function min(a,b){return a<b?a:b}
      # Convert RGB(0..255) to HSV; return H in degrees [0,360), S,V in [0,1]
      function rgb2hsv(R,G,B,   r,g,b,M,m,d,H,S,V) {
        r=R/255.0; g=G/255.0; b=B/255.0;
        M=r; if(g>M) M=g; if(b>M) M=b;
        m=r; if(g<m) m=g; if(b<m) m=b;
        d=M-m; V=M;
        if (M==0) { S=0 } else { S=(d==0?0:d/M) }
        if (d==0) { H=0 }
        else if (M==r) { H = 60.0 * fmod(((g-b)/d), 6) }
        else if (M==g) { H = 60.0 * (((b-r)/d) + 2) }
        else           { H = 60.0 * (((r-g)/d) + 4) }
        if (H < 0) H += 360.0
        hsv[1]=H; hsv[2]=S; hsv[3]=V
      }
      function fmod(a,b){ return a - int(a/b)*b }
      BEGIN{ total=0; pink=0; }
      NF==3 {
        R=$1; G=$2; B=$3;
        total++;
        rgb2hsv(R,G,B);
        H=hsv[1]; S=hsv[2]; V=hsv[3];
        # classify: hue in magenta band AND sufficiently saturated/bright
        if (H>=HMIN && H<=HMAX && S>=SMIN && V>=VMIN) pink++;
        # save last metrics to show a couple of examples (optional)
        if (total<=10) printf "DBG frame%02d: RGB=(%3d,%3d,%3d) HSV=(%6.1f°, %4.2f, %4.2f)\n", total,R,G,B,H,S,V > "/dev/stderr"
      }
      END {
        if (total==0) { printf "TOTAL=0 PINK=0 RATIO=0\n"; exit; }
        printf "TOTAL=%d PINK=%d RATIO=%.3f\n", total, pink, pink/total;
      }'
)"

if ! printf "%s" "$summary" | grep -q 'TOTAL='; then
  echo "No frames parsed (clip too short or pipeline issue)."
  exit 1
fi

eval "$summary"  # sets TOTAL,PINK,RATIO
echo "File: $file"
echo "Analyzed: first ${duration}s @ ${sample_fps} fps → frames: ${TOTAL}"
echo "Pink-ish frames (hue in ${HMIN}-${HMAX}°, S>=${SMIN}, V>=${VMIN}): ${PINK}"
echo "Ratio: ${RATIO} (threshold: ${MIN_RATIO})"

awk -v r="$RATIO" -v thr="$MIN_RATIO" 'BEGIN{ exit !(r+0 >= thr+0) }' \
  && { echo "DETECTED: Pink intro present"; exit 0; }
echo "Not detected"; exit 1