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

if [[ $# -lt 1 ]]; then
  echo "Usage: $0 <jsonl-file> [max-bytes-per-file]" >&2
  exit 1
fi

FILE="$1"
MAX_BYTES="${2:-1048576}"

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

SIZE=$(wc -c < "$FILE")

if [[ "$SIZE" -le "$MAX_BYTES" ]]; then
  cat "$FILE"
  exit 0
fi

HALF=$(( MAX_BYTES / 2 ))

head -c "$HALF" "$FILE"
printf '\n...TRUNCATED...\n'
tail -c "$HALF" "$FILE"