#!/bin/bash
# SPDX-License-Identifier: BSD-3-Clause
# build_video.sh - build the final open-iov 1.0.0 demo video: a drawtext
# title card, the split-screen main segment (two GZDOOM VMs, one per pane,
# captured through the KVMFR ivshmem path), and an optional end card,
# concatenated into one 1280x720@30 libx264 yuv420p mp4.
#
# Usage:
#   build_video.sh <title-text> <main.mp4> [end-text]
#   build_video.sh <title-text> <dirA> <dirB> [end-text]
#     title-text  text for the title card (required, non-empty)
#     main.mp4    pre-built split-screen video (e.g. from split_screen.sh)
#     dirA dirB   two frame-%04d.ppm dirs; split_screen.sh (next to this
#                 script) is invoked first at FPS to build the main segment
#     end-text    optional text for the end card (omitted = no end card)
#
# Output: $OUT if set, else ./open-iov-1.0.0-demo.mp4 in the current dir.
# Env knobs: FPS (default 30), CARD_SECS (default 5), FONTSIZE (default 48).
#
# Approach: title/end cards are generated with ffmpeg drawtext (white on
# dark 0x101010, 1280x720); the main segment is normalized to 1280x720@30
# (aspect-preserving fit + letterbox pad, audio dropped - the demo video is
# video-only); the three segments are concatenated with the concat demuxer
# followed by ONE re-encode. Stream-copy concat is brittle across
# separately-generated mp4s (timestamp/param mismatches); the re-encode is
# cheap at these lengths and guarantees a clean single-stream output.
# The title font is auto-detected (DejaVuSans/NotoSans); the script fails
# with a clear message if no TTF font exists.
#
# Requires: ffmpeg with libx264 + drawtext (libfreetype); split_screen.sh
# next to this script for the two-dirs form.
set -euo pipefail

usage() {
    sed -n '3,31p' "$0" | sed 's/^# \{0,1\}//'
}

die() { echo "build_video.sh: ERROR: $*" >&2; exit 1; }

# grep -q would SIGPIPE the ffmpeg producer under pipefail; capture first.
ffmpeg_has() {  # $1 = encoder/filter token
    local out
    out=$(ffmpeg -hide_banner "$2" 2>/dev/null) || true
    case "$out" in *" $1 "*) return 0 ;; *) return 1 ;; esac
}

command -v ffmpeg >/dev/null 2>&1 || die "ffmpeg not found in PATH"
ffmpeg_has libx264 -encoders || die "ffmpeg has no libx264 encoder"
ffmpeg_has drawtext -filters || die "ffmpeg has no drawtext filter (needs libfreetype)"

# --- locate a usable TTF font -------------------------------------------
FONT=""
for f in \
    /usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf \
    /usr/share/fonts/truetype/dejavu/DejaVuSans.ttf \
    /usr/share/fonts/truetype/noto/NotoSans-Regular.ttf \
    /usr/share/fonts/dejavu/DejaVuSans.ttf; do
    if [ -f "$f" ]; then FONT=$f; break; fi
done
if [ -z "$FONT" ] && command -v fc-match >/dev/null 2>&1; then
    f=$(fc-match -f '%{file}' sans 2>/dev/null || true)
    [ -n "$f" ] && [ -f "$f" ] && FONT=$f
fi
[ -n "$FONT" ] || die "no usable TTF font found (looked for DejaVuSans, NotoSans; \
install fonts-dejavu-core or set up fontconfig)"
echo "build_video.sh: font=$FONT" >&2

# --- args ----------------------------------------------------------------
[ "$#" -ge 1 ] || { usage; exit 2; }
TITLE=$1; shift
[ -n "$TITLE" ] || die "title text must be non-empty"
MAIN="" DIR_A="" DIR_B="" END=""
if [ "$#" -ge 1 ] && [ -d "$1" ]; then
    DIR_A=$1
    [ "$#" -ge 2 ] && [ -d "$2" ] || die "two-dirs form needs two directories: <dirA> <dirB> [end-text]"
    DIR_B=$2
    END=${3:-}
elif [ "$#" -ge 1 ]; then
    [ -f "$1" ] || die "main input not found: $1"
    MAIN=$1
    END=${2:-}
else
    die "missing main input (mp4 file or two frame dirs)"
fi

FPS=${FPS:-30}
CARD_SECS=${CARD_SECS:-5}
FONTSIZE=${FONTSIZE:-48}
OUT=${OUT:-$PWD/open-iov-1.0.0-demo.mp4}
HERE=$(cd "$(dirname "$0")" && pwd)

TMP=$(mktemp -d "${TMPDIR:-/tmp}/build_video.XXXXXX")
trap 'rm -rf "$TMP"' EXIT

# --- cards (drawtext; text via textfile so ':' ',' '%' etc. are literal) --
make_card() {
    local text=$1 out=$2 tf="$TMP/card-$$.txt"
    printf '%s' "$text" > "$tf"
    ffmpeg -hide_banner -loglevel warning -y \
        -f lavfi -i "color=c=0x101010:s=1280x720:r=$FPS:d=$CARD_SECS" \
        -vf "drawtext=fontfile=$FONT:textfile=$tf:fontcolor=white:fontsize=$FONTSIZE:expansion=none:x=(w-text_w)/2:y=(h-text_h)/2" \
        -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
        "$out"
}

echo "build_video.sh: title card (${CARD_SECS}s)..." >&2
make_card "$TITLE" "$TMP/title.mp4"

# --- main segment --------------------------------------------------------
if [ -n "$DIR_A" ]; then
    [ -x "$HERE/split_screen.sh" ] || die "split_screen.sh not found/executable next to build_video.sh"
    echo "build_video.sh: building split-screen main from $DIR_A + $DIR_B..." >&2
    "$HERE/split_screen.sh" "$DIR_A" "$DIR_B" "$TMP/split.mp4" "$FPS"
    MAIN=$TMP/split.mp4
fi
echo "build_video.sh: normalizing main segment to 1280x720@$FPS..." >&2
ffmpeg -hide_banner -loglevel warning -y -i "$MAIN" \
    -vf "scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:(ow-iw)/2:(oh-ih)/2,setsar=1,fps=$FPS" \
    -an -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
    "$TMP/main.mp4"

# --- concat [title, main, end] ------------------------------------------
printf "file '%s'\n" "$TMP/title.mp4" "$TMP/main.mp4" > "$TMP/list.txt"
if [ -n "$END" ]; then
    echo "build_video.sh: end card (${CARD_SECS}s)..." >&2
    make_card "$END" "$TMP/end.mp4"
    printf "file '%s'\n" "$TMP/end.mp4" >> "$TMP/list.txt"
fi

echo "build_video.sh: concatenating..." >&2
ffmpeg -hide_banner -loglevel warning -y -f concat -safe 0 -i "$TMP/list.txt" \
    -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
    -r "$FPS" -movflags +faststart \
    "$OUT"

[ -s "$OUT" ] || die "ffmpeg produced no output: $OUT"
if command -v ffprobe >/dev/null 2>&1; then
    ffprobe -v error -select_streams v:0 \
        -show_entries stream=width,height,r_frame_rate,duration \
        -show_entries format=duration,size \
        -of default=nw=1 "$OUT" | sed 's/^/build_video.sh: /' >&2
fi
echo "VIDEO_DONE $OUT" >&2