#!/usr/bin/env bash

set -euo pipefail

# pdf_to_png.sh (magick-only backend, behaves like pdf_to_image)
#
# Convert one or more PDF files to image files using ImageMagick v7 `magick`.
# Default output format is jpg, but can be changed with -f.

# Source common library
SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
# shellcheck source=../lib/common.sh
source "$SCRIPT_DIR/../lib/common.sh"

OUTPUT_DIR=""
OUTPUT_FORMAT="jpg"
PDF_FILES=()

usage() {
  cat << EOF
Usage:
  $(basename "$0") [OPTIONS] PDF_FILE [PDF_FILE...]

Convert one or more PDF files to images using ImageMagick 'magick'.

Options:
  -o DIR     Output directory (default: current directory)
  -f FORMAT  Output image format (default: jpg)
  -h         Show this help

Examples:
  $(basename "$0") file.pdf
  $(basename "$0") -f png file1.pdf file2.pdf
  $(basename "$0") -o out -f webp file.pdf
EOF
}

ensure_magick() {
  require_imagemagick "magick" || exit 1
}

parse_args() {
  local opt
  OUTPUT_DIR=""
  OUTPUT_FORMAT="jpg"
  PDF_FILES=()

  while getopts ":o:f:h" opt; do
    case "$opt" in
      o)
        OUTPUT_DIR="$OPTARG"
        ;;
      f)
        OUTPUT_FORMAT="$OPTARG"
        ;;
      h)
        usage
        exit 0
        ;;
      *)
        usage
        exit 1
        ;;
    esac
  done

  shift $((OPTIND - 1))

  if [[ $# -lt 1 ]]; then
    echo "Error: at least one PDF file must be specified." >&2
    usage
    exit 1
  fi

  PDF_FILES=("$@")

  if [[ -z ${OUTPUT_DIR:-} ]]; then
    OUTPUT_DIR="${PWD}"
  fi

  if [[ ! -d $OUTPUT_DIR ]]; then
    mkdir -p "$OUTPUT_DIR"
  fi
}

convert_pdf() {
  local pdf_file="$1"
  local base name out_pattern

  name="$(basename "$pdf_file")"
  base="${name%.*}"
  out_pattern="${OUTPUT_DIR%/}/${base}_page-"

  log "Converting '$pdf_file' to $OUTPUT_FORMAT using magick -> ${out_pattern}*.${OUTPUT_FORMAT}"
  magick -density 300 "$pdf_file" -quality 90 "${out_pattern}%d.${OUTPUT_FORMAT}"
}

main() {
  ensure_magick
  parse_args "$@"

  local pdf
  for pdf in "${PDF_FILES[@]}"; do
    if [[ ! -f $pdf ]]; then
      echo "Warning: '$pdf' is not a regular file, skipping." >&2
      continue
    fi

    convert_pdf "$pdf"
  done

  log "Done converting PDFs to ${OUTPUT_FORMAT}. Output directory: $OUTPUT_DIR"
}

main "$@"