#!/bin/sh
# Generate a post's banner video (01.mp4) and preview image (01.png) via
# the Replicate black-forest-labs/flux-3 text-to-video model, using the
# prompt.{scene,environment,style,video} fields already present in the
# post's frontmatter.
#
# Usage:
#   sh scripts/create-video.sh <path-to-post-dir-or-index.md> [--force] [--dry-run]
#
# Requires: REPLICATE_API_TOKEN exported in the environment.
#
# Video settings (matching every existing post's square/silent convention,
# just at higher resolution): 1:1 aspect ratio, 1080p, 5s, no audio.

set -e

print_usage() {
  echo "Usage: sh scripts/create-video.sh <post-dir-or-index.md> [options]"
  echo ""
  echo "Generates a post's banner video (01.mp4) via the Replicate flux-3"
  echo "text-to-video model, using that post's prompt.{scene,environment,style,video}"
  echo "frontmatter fields, then extracts the first frame as 01.png."
  echo ""
  echo "Arguments:"
  echo "  <post-dir-or-index.md>   Path to content/posts/<slug>/ or its index.md"
  echo ""
  echo "Options:"
  echo "  -f, --force     Overwrite existing 01.mp4 / 01.png"
  echo "  --dry-run       Print the constructed prompt and request JSON, make no API call"
  echo "  -h, --help      Show this help"
  echo ""
  echo "Requires REPLICATE_API_TOKEN to be exported in the environment."
}

FORCE=0
DRY_RUN=0
POST_ARG=""

for arg in "$@"; do
  case "$arg" in
    -f|--force) FORCE=1 ;;
    --dry-run) DRY_RUN=1 ;;
    -h|--help) print_usage; exit 0 ;;
    -*)
      echo "Unknown option: $arg" >&2
      exit 1
      ;;
    *) POST_ARG="$arg" ;;
  esac
done

if [ -z "$POST_ARG" ]; then
  print_usage >&2
  exit 1
fi

if [ -d "$POST_ARG" ]; then
  BUNDLE_DIR="${POST_ARG%/}"
  INDEX_MD="$BUNDLE_DIR/index.md"
else
  INDEX_MD="$POST_ARG"
  BUNDLE_DIR=$(dirname "$POST_ARG")
fi

if [ ! -f "$INDEX_MD" ]; then
  echo "Error: $INDEX_MD not found" >&2
  exit 1
fi

if [ -z "$REPLICATE_API_TOKEN" ]; then
  echo "Error: REPLICATE_API_TOKEN is not set in your environment." >&2
  echo "Export it before running this script, e.g.:" >&2
  echo "  export REPLICATE_API_TOKEN=r8_..." >&2
  exit 1
fi

DEST_MP4="$BUNDLE_DIR/01.mp4"
DEST_PNG="$BUNDLE_DIR/01.png"

if [ "$FORCE" -ne 1 ]; then
  if [ -e "$DEST_MP4" ]; then
    echo "Error: $DEST_MP4 already exists (use --force to overwrite)" >&2
    exit 1
  fi
  if [ -e "$DEST_PNG" ]; then
    echo "Error: $DEST_PNG already exists (use --force to overwrite)" >&2
    exit 1
  fi
fi

PROMPT_JSON=$(yq --front-matter=extract -o=json '.prompt' "$INDEX_MD")

if [ "$PROMPT_JSON" = "null" ] || [ -z "$PROMPT_JSON" ]; then
  echo "Error: $INDEX_MD has no prompt.* fields in its frontmatter" >&2
  exit 1
fi

SCENE=$(printf '%s' "$PROMPT_JSON" | jq -r '.scene // empty')
ENVIRONMENT=$(printf '%s' "$PROMPT_JSON" | jq -r '.environment // empty')
STYLE=$(printf '%s' "$PROMPT_JSON" | jq -r '.style // empty')
VIDEO=$(printf '%s' "$PROMPT_JSON" | jq -r '.video // empty')

if [ -z "$SCENE" ]; then
  echo "Error: prompt.scene is missing/empty in $INDEX_MD" >&2
  exit 1
fi
if [ -z "$ENVIRONMENT" ]; then
  echo "Error: prompt.environment is missing/empty in $INDEX_MD" >&2
  exit 1
fi
if [ -z "$STYLE" ]; then
  echo "Error: prompt.style is missing/empty in $INDEX_MD" >&2
  exit 1
fi
if [ -z "$VIDEO" ]; then
  echo "Error: prompt.video is missing/empty in $INDEX_MD" >&2
  exit 1
fi

SLUG=$(yq --front-matter=extract '.slug' "$INDEX_MD")
echo "▶ ${SLUG:-$(basename "$BUNDLE_DIR")}: building prompt from frontmatter"

PROMPT="${SCENE} ${ENVIRONMENT} ${STYLE} ${VIDEO}"

INPUT_JSON=$(jq -n \
  --arg prompt "$PROMPT" \
  --arg duration "5" \
  --arg resolution "1080p" \
  --arg aspect_ratio "1:1" \
  '{
    input: {
      prompt: $prompt,
      images: [],
      duration: $duration,
      resolution: $resolution,
      aspect_ratio: $aspect_ratio,
      generate_audio: false
    }
  }')

if [ "$DRY_RUN" -eq 1 ]; then
  echo "--- Constructed prompt ---"
  echo "$PROMPT"
  echo "--- Request body ---"
  echo "$INPUT_JSON" | jq .
  echo "(dry run — no API call made)"
  exit 0
fi

echo "▶ Submitting generation request to Replicate (flux-3)..."
CREATE_RESPONSE=$(curl -sS \
  -X POST \
  -H "Authorization: Bearer $REPLICATE_API_TOKEN" \
  -H "Content-Type: application/json" \
  -H "Prefer: wait=60" \
  -d "$INPUT_JSON" \
  https://api.replicate.com/v1/models/black-forest-labs/flux-3/predictions \
  -w '\n%{http_code}')

HTTP_CODE=$(printf '%s' "$CREATE_RESPONSE" | tail -n1)
BODY=$(printf '%s' "$CREATE_RESPONSE" | sed '$d')

case "$HTTP_CODE" in
  2??) : ;;
  *)
    echo "Error: Replicate API returned HTTP $HTTP_CODE" >&2
    echo "$BODY" | jq -r '.detail // .error // .' >&2
    exit 1
    ;;
esac

STATUS=$(printf '%s' "$BODY" | jq -r '.status')
GET_URL=$(printf '%s' "$BODY" | jq -r '.urls.get')
PREDICTION_ID=$(printf '%s' "$BODY" | jq -r '.id')
POLL_BODY="$BODY"

if [ -z "$GET_URL" ] || [ "$GET_URL" = "null" ]; then
  echo "Error: unexpected response from Replicate (no urls.get):" >&2
  echo "$BODY" >&2
  exit 1
fi

POLL_INTERVAL=5
MAX_WAIT=600
ELAPSED=0

while :; do
  case "$STATUS" in
    succeeded) break ;;
    failed|canceled)
      ERR=$(printf '%s' "$POLL_BODY" | jq -r '.error // "unknown error"')
      echo "Error: prediction $STATUS: $ERR" >&2
      exit 1
      ;;
  esac

  if [ "$ELAPSED" -ge "$MAX_WAIT" ]; then
    echo "Error: timed out after ${MAX_WAIT}s waiting on prediction $PREDICTION_ID" >&2
    echo "Check status manually: curl -H \"Authorization: Bearer \$REPLICATE_API_TOKEN\" $GET_URL" >&2
    exit 1
  fi

  sleep "$POLL_INTERVAL"
  ELAPSED=$((ELAPSED + POLL_INTERVAL))

  POLL_BODY=$(curl -sS -H "Authorization: Bearer $REPLICATE_API_TOKEN" "$GET_URL")
  STATUS=$(printf '%s' "$POLL_BODY" | jq -r '.status')
  echo "  … ${ELAPSED}s elapsed, status: $STATUS"
done

OUTPUT_URL=$(printf '%s' "$POLL_BODY" | jq -r '.output')
if [ -z "$OUTPUT_URL" ] || [ "$OUTPUT_URL" = "null" ]; then
  echo "Error: prediction succeeded but no output URL was returned" >&2
  echo "$POLL_BODY" >&2
  exit 1
fi

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

TMP_MP4="$TMP_DIR/01.mp4"
TMP_PNG="$TMP_DIR/01.png"

echo "▶ Downloading generated video..."
curl -fSL -o "$TMP_MP4" "$OUTPUT_URL"

echo "▶ Extracting first frame as preview PNG..."
ffmpeg -y -loglevel error -i "$TMP_MP4" -vframes 1 "$TMP_PNG" < /dev/null

mv "$TMP_MP4" "$DEST_MP4"
mv "$TMP_PNG" "$DEST_PNG"

echo "✓ Wrote $DEST_MP4 and $DEST_PNG"