#!/bin/bash

# Usage: ./md2data_safe.sh FILE [--css CSS_FILE] [--size LIMIT]
# Converts HTML or Markdown to Base64 Data URL
# Default size limit is 30000 characters

# ----------------- Functions -----------------

show_help() {
    echo "Usage: $0 FILE [--css CSS_FILE] [--size LIMIT]"
    echo
    echo "Parameters:"
    echo "  FILE         HTML or Markdown file to convert"
    echo "  --css FILE   Optional single CSS file to inject"
    echo "  --size LIMIT Optional maximum size for Data URL (default: 30000)"
    exit 0
}

check_file_exists() {
    local file="$1"
    if [ ! -f "$file" ]; then
        echo "Error: file '$file' not found." >&2
        exit 1
    fi
}

convert_md_to_html() {
    local file="$1"
    if ! command -v pandoc >/dev/null 2>&1; then
        echo "Error: pandoc is not installed." >&2
        exit 1
    fi
    pandoc "$file" -f markdown -t html -s
}

minify_css() {
    local css_file="$1"
    tr -d '\n' < "$css_file" | sed -E 's/[[:space:]]+/ /g;s/ *{ */{/g;s/ *} */}/g;s/ *; */;/g'
}

escape_css_for_sed() {
    local css="$1"
    css=${css//\\/\\\\}  # Escape backslash
    css=${css//\//\\/}   # Escape slashes
    css=${css//&/\\&}    # Escape &
    echo "$css"
}

inject_css() {
    local html_file="$1"
    local css="$2"
    local escaped_css
    escaped_css=$(escape_css_for_sed "$css")

    if grep -q "</head>" "$html_file"; then
        sed "/<\/head>/i <style>$escaped_css</style>" "$html_file"
    else
        echo "<style>$escaped_css</style>"
        cat "$html_file"
    fi
}

generate_data_url() {
    if base64 --help 2>&1 | grep -q -- '-w'; then
        base64 -w 0
    else
        base64
    fi
}

check_size() {
    local size="$1"
    local limit="$2"
    echo "Data URL size: $size characters"
    if [ "$size" -gt "$limit" ]; then
        echo "WARNING: Data URL exceeds recommended limit of $limit characters."
    else
        echo "Data URL is within a safe size for most browsers."
    fi
}

# ----------------- Argument Parsing -----------------

CSS_FILE=""
LIMIT=30000
FILE=""

while [[ $# -gt 0 ]]; do
    case "$1" in
        --help|-h)
            show_help
            ;;
        --css)
            CSS_FILE="$2"
            shift 2
            ;;
        --size)
            LIMIT="$2"
            shift 2
            ;;
        -*)
            echo "Unknown option: $1" >&2
            exit 1
            ;;
        *)
            FILE="$1"
            shift
            ;;
    esac
done

if [[ -z "$FILE" ]]; then
    show_help
fi

check_file_exists "$FILE"
EXT="${FILE##*.}"

# ----------------- Main Processing -----------------

# Temporary HTML file for streaming
TMP_HTML=$(mktemp)
trap 'rm -f "$TMP_HTML"' EXIT

# Convert Markdown or copy HTML
if [[ "$EXT" == "md" ]]; then
    convert_md_to_html "$FILE" > "$TMP_HTML"
else
    cp "$FILE" "$TMP_HTML"
fi

# Minify and inject CSS if provided
if [[ -n "$CSS_FILE" ]]; then
    check_file_exists "$CSS_FILE"
    MIN_CSS=$(minify_css "$CSS_FILE")
    TMP_HTML_INJECTED=$(mktemp)
    inject_css "$TMP_HTML" "$MIN_CSS" > "$TMP_HTML_INJECTED"
    mv "$TMP_HTML_INJECTED" "$TMP_HTML"
    echo "Injected CSS size: ${#MIN_CSS} characters"
fi

# Generate Base64 Data URL
DATA_URL="data:text/html;charset=utf-8;base64,$(generate_data_url < "$TMP_HTML")"

# Check size
SIZE=${#DATA_URL}
check_size "$SIZE" "$LIMIT"

# Display clickable HTML link
echo
echo "Clickable HTML link:"
echo "<a href=\"$DATA_URL\" target=\"_blank\">Open $FILE</a>"