Fix epub Remarkable black bar issue

fix_epub_black_bar.sh

#!/bin/bash

set -e # Exit immediately if a command exits with a non-zero status.

# --- Configuration ---
# CSS rule to comment out (adjust if needed, mindful of regex special chars)
TARGET_RULE_TEXT="background-color: inherit;"
# Regex pattern for sed (basic version: handles spaces around colon)
# Using \| as delimiter to avoid escaping slashes in rule
SED_PATTERN='background-color[[:space:]]*:[[:space:]]*inherit;'
# Replacement pattern for sed (comments out the matched pattern)
SED_REPLACEMENT='/* & */' # & substitutes the matched pattern

# --- Input Validation ---
if [ -z "$1" ]; then
  echo "Usage: $0 <input_epub_file>"
  exit 1
fi

input_epub="$1"
if [ ! -f "$input_epub" ]; then
  echo "Error: Input file not found: '$input_epub'"
  exit 1
fi

# --- Prepare Filenames and Directories ---
# Attempt to get absolute path for robustness
# Fix: Correctly combine directory and basename in fallback using echo
input_epub_abs=$(readlink -f "$input_epub" 2>/dev/null || echo "$(cd "$(dirname "$input_epub")" && pwd)/$(basename "$input_epub")")

# Derive output filename relative to the original file's directory
base_name=$(basename "$input_epub" .epub)
dir_name=$(dirname "$input_epub_abs")
output_epub="$dir_name/${base_name}-FIXED.epub"

# Create temporary directory safely
tmp_dir=$(mktemp -d -t epub_fix_XXXXXX)
echo "Using temporary directory: $tmp_dir"

# --- Cleanup Function ---
# Ensures temporary directory is removed on exit, error, or interrupt
cleanup() {
  echo "Cleaning up temporary directory: $tmp_dir"
  rm -rf "$tmp_dir"
}
trap cleanup EXIT HUP INT QUIT TERM

# --- Unzip EPUB ---
echo "Unzipping '$input_epub_abs' to '$tmp_dir'..."
# Use -o to overwrite files without prompting if dir wasn't properly cleaned before
unzip -o -q "$input_epub_abs" -d "$tmp_dir"
if [ $? -ne 0 ]; then
  echo "Error: Failed to unzip '$input_epub_abs'"
  exit 1 # Exit is handled by set -e, but explicit exit is clearer
fi
echo "Unzip complete."

# --- Modify CSS Files ---
echo "Searching for CSS/HTML/XHTML files and commenting out '$TARGET_RULE_TEXT'..."
# Use find with -exec to directly call sed on found files.
# Using {} + executes sed on multiple files at once for efficiency.
# -i.bak creates backups, ensuring portability (GNU/BSD sed).
# Using | as sed delimiter avoids issues with slashes in patterns.
find "$tmp_dir" -type f \( -name "*.css" -o -name "*.xhtml" -o -name "*.html" \) \
     -exec sed -i.bak "s|$SED_PATTERN|$SED_REPLACEMENT|g" {} +

# Check the exit status of find (optional, set -e should handle it)
if [ $? -ne 0 ]; then
    echo "Warning: find or sed command might have failed. Check output and .bak files in $tmp_dir if necessary."
    # Decide if script should exit here or continue. Continuing allows zipping partially modified files.
fi

# Clean up backup files created by sed -i.bak
echo "Cleaning up sed backup files..."
find "$tmp_dir" -type f -name "*.bak" -delete

echo "CSS processing complete."

# --- Re-zip EPUB ---
echo "Re-zipping contents into '$output_epub'..."
mimetype_path="$tmp_dir/mimetype"
if [ ! -f "$mimetype_path" ]; then
    echo "Error: 'mimetype' file not found in '$tmp_dir'. Cannot create valid EPUB."
    exit 1
fi

# Navigate to temp directory for correct relative paths in zip
original_pwd=$(pwd)
cd "$tmp_dir"

# Create the new EPUB, ensuring mimetype is first and uncompressed (-X0)
# Using a subshell to avoid permission issues with output file if created in restricted dir
(zip -X0 "$output_epub" mimetype)
if [ $? -ne 0 ]; then
  echo "Error: Failed to add 'mimetype' to '$output_epub'"
  cd "$original_pwd" # Go back before exiting
  exit 1
fi

# Add the rest of the files, recursively (-r), grow existing archive (-g), exclude mimetype
# -D prevents adding directory entries, often needed for EPUB validation
(zip -rgD "$output_epub" . -x mimetype)
if [ $? -ne 0 ]; then
  echo "Error: Failed to add contents to '$output_epub'"
  cd "$original_pwd" # Go back before exiting
  exit 1
fi

# Return to original directory
cd "$original_pwd"

echo "Successfully created fixed EPUB: '$output_epub'"

# Cleanup is handled by the trap EXIT
exit 0