# HTML-based Invoice Generator
import io
import os
import zipfile
import tempfile
import shutil
from typing import Dict, List
import base64
import subprocess
import sys

import pandas as pd
import streamlit as st
from num2words import num2words

# Try to import Playwright for PDF conversion
PLAYWRIGHT_AVAILABLE = False

try:
    from playwright.sync_api import sync_playwright
    PLAYWRIGHT_AVAILABLE = True
except ImportError:
    pass

# Install Playwright browsers at runtime (disabled by default for hosted envs)
_playwright_flag = os.path.join(tempfile.gettempdir(), 'playwright_installed')
_allow_runtime_install = os.environ.get('PLAYWRIGHT_RUNTIME_INSTALL') == '1'
if PLAYWRIGHT_AVAILABLE and _allow_runtime_install and not os.path.exists(_playwright_flag):
    try:
        cmd = [sys.executable, "-m", "playwright", "install", "chromium"]
        subprocess.run(cmd, check=True)
        with open(_playwright_flag, 'w') as f:
            f.write('installed')
        print("✅ Playwright browsers installed!")
    except Exception as e:
        print(f"⚠️ Failed to install Playwright browsers: {e}")
else:
    if not _allow_runtime_install:
        print("ℹ️ Skipping runtime Playwright install (build-time install expected).")

# Try to import PyPDF for PDF page extraction
PYPDF_AVAILABLE = False

try:
    from pypdf import PdfReader, PdfWriter
    PYPDF_AVAILABLE = True
except ImportError:
    pass

# -------------------------
# Utility helpers
# -------------------------

def safe_str(x):
    if pd.isna(x):
        return ""
    return str(x)

def format_amount(x):
    """Format amount as Indian currency format"""
    try:
        num = float(x)
        if num == 0:
            return "0.00"
        return f"{num:,.2f}"
    except Exception:
        return "0.00"

def to_words(value):
    """Convert number to words"""
    try:
        num = float(value)
        if num == 0:
            return "Zero Rupees Only"
        if num.is_integer():
            num = int(num)
        return num2words(num, to="cardinal", lang="en").title() + " Only"
    except Exception:
        return "Zero Rupees Only"

# -------------------------
# HTML Template Processing
# -------------------------

def fill_html_template(template_path: str, invoice_data: dict, output_path: str):
    """Fill HTML template with invoice data and save"""
    
    # Read the HTML template
    with open(template_path, 'r', encoding='utf-8') as f:
        html_content = f.read()
    
    # Prepare data for injection
    data = {
        'invoice_no': invoice_data.get('Invoice No', ''),
        'invoice_date': invoice_data.get('Invoice Date', ''),
        'customer_name': invoice_data.get('Customer Name', ''),
        'buyer_gstin': invoice_data.get('Customer GSTIN', ''),
        'buyer_pan': invoice_data.get('Customer PAN', ''),
        'buyer_cin': invoice_data.get('Customer CIN', ''),
        'po_no': invoice_data.get('PO No', ''),
        'buyer_state': invoice_data.get('Customer State', ''),
    }
    
    # Handle customer address (split into multiple lines)
    address = invoice_data.get('Customer Address', '')
    if address:
        address_parts = [p.strip() for p in address.split(',')]
        data['customer_address_1'] = address_parts[0] if len(address_parts) > 0 else ''
        data['customer_address_2'] = address_parts[1] if len(address_parts) > 1 else ''
        data['customer_address_3'] = ', '.join(address_parts[2:]) if len(address_parts) > 2 else ''
    else:
        data['customer_address_1'] = data['customer_address_2'] = data['customer_address_3'] = ''
    
    # Calculate totals dynamically
    items = invoice_data.get('Items', [])
    total_taxable = 0
    total_cgst = 0
    total_sgst = 0
    total_igst = 0
    
    for item in items:
        taxable_value = float(item.get('Taxable Value', 0))
        cgst_percentage = float(item.get('CGST %', 0))
        sgst_percentage = float(item.get('SGST %', 0))
        igst_percentage = float(item.get('IGST %', 0))
        
        # Calculate tax amounts dynamically
        cgst_amount = round((taxable_value * cgst_percentage / 100), 2)
        sgst_amount = round((taxable_value * sgst_percentage / 100), 2)
        igst_amount = round((taxable_value * igst_percentage / 100), 2)
        
        # Add to totals
        total_taxable += taxable_value
        total_cgst += cgst_amount
        total_sgst += sgst_amount
        total_igst += igst_amount
    
    # Calculate grand total
    grand_total = total_taxable + total_cgst + total_sgst + total_igst
    
    # Add totals to data
    data.update({
        'total_taxable': format_amount(total_taxable),
        'total_cgst': format_amount(total_cgst),
        'total_sgst': format_amount(total_sgst),
        'total_igst': format_amount(total_igst),
        'grand_total': format_amount(grand_total),
        'rounding': format_amount(0),  # Can be calculated if needed
        'net_amount': format_amount(grand_total),
        'words_total': to_words(grand_total),
        'words_cgst': to_words(total_cgst),
        'words_sgst': to_words(total_sgst),
        'words_igst': to_words(total_igst),
    })
    
    # Prepare items data for JavaScript injection
    items_js = []
    for i, item in enumerate(items):
        taxable_value = float(item.get('Taxable Value', 0))
        cgst_percentage = float(item.get('CGST %', 0))
        sgst_percentage = float(item.get('SGST %', 0))
        igst_percentage = float(item.get('IGST %', 0))
        
        # Calculate tax amounts dynamically from percentages
        cgst_amount = round((taxable_value * cgst_percentage / 100), 2)
        sgst_amount = round((taxable_value * sgst_percentage / 100), 2)
        igst_amount = round((taxable_value * igst_percentage / 100), 2)
        
        # Calculate total amount
        total_amount = taxable_value + cgst_amount + sgst_amount + igst_amount
        
        items_js.append({
            'sr': i + 1,
            'desc': item.get('Service Details', ''),
            'hsn': item.get('HSN', ''),
            'tax': taxable_value,
            'cgst_p': cgst_percentage,
            'cgst_a': cgst_amount,  # Dynamically calculated
            'sgst_p': sgst_percentage,
            'sgst_a': sgst_amount,  # Dynamically calculated
            'igst_p': igst_percentage,
            'igst_a': igst_amount,  # Dynamically calculated
            'total': round(total_amount, 2),  # Dynamically calculated
        })
    
    # Create JavaScript injection code
    js_injection = f"""
<script>
// Data injection
const invoiceData = {data};
const itemsData = {items_js};

// Inject data into template
inject({{ ...invoiceData, items: itemsData }});
</script>
"""
    
    # Insert the injection script before the closing body tag
    html_content = html_content.replace('</body>', f'{js_injection}\n</body>')
    
    # Handle logo images (convert to base64 if exists)
    # Check for both company logos
    logo_paths = ['assets/inephos.png', 'assets/srestham.png']
    for logo_path in logo_paths:
        if os.path.exists(logo_path):
            with open(logo_path, 'rb') as img_file:
                img_b64 = base64.b64encode(img_file.read()).decode()
                img_src = f"data:image/png;base64,{img_b64}"
                html_content = html_content.replace(f'src="{logo_path}"', f'src="{img_src}"')
    
    # Also handle any remaining generic image references
    if os.path.exists('image.png'):
        with open('image.png', 'rb') as img_file:
            img_b64 = base64.b64encode(img_file.read()).decode()
            img_src = f"data:image/png;base64,{img_b64}"
            html_content = html_content.replace('src="image.png"', f'src="{img_src}"')
    
    # Write the filled HTML
    with open(output_path, 'w', encoding='utf-8') as f:
        f.write(html_content)
    
    print(f"✅ Generated HTML invoice: {output_path}")
    return output_path


def html_to_pdf_playwright(html_path: str, pdf_path: str) -> bool:
    """Convert HTML to PDF using Playwright with Windows compatibility"""
    import asyncio
    import sys
    import traceback
    
    async def create_pdf():
        from playwright.async_api import async_playwright
        
        async with async_playwright() as p:
            browser = await p.chromium.launch(headless=True)
            page = await browser.new_page()
            
            # Load the HTML file
            file_url = f"file:///{os.path.abspath(html_path).replace(os.sep, '/')}"
            await page.goto(file_url, wait_until='networkidle')
            
            # Generate PDF with proper settings
            await page.pdf(
                path=pdf_path,
                format='A4',
                margin={
                    'top': '16mm',
                    'bottom': '16mm', 
                    'left': '10mm',
                    'right': '10mm'
                },
                print_background=True,
                prefer_css_page_size=True
            )
            
            await browser.close()
    
    def _try_generate() -> bool:
        try:
            # Set event loop policy for Windows compatibility
            if sys.platform == "win32":
                asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())
            asyncio.run(create_pdf())
            return True
        except Exception as ex:
            raise ex

    def _install_playwright_browser_once() -> bool:
        flag = os.path.join(tempfile.gettempdir(), 'playwright_browser_installed')
        if os.path.exists(flag):
            return True
        try:
            subprocess.run([sys.executable, "-m", "playwright", "install", "chromium"], check=True)
            with open(flag, 'w') as f:
                f.write('installed')
            print("✅ Playwright Chromium downloaded at runtime.")
            return True
        except Exception as ex:
            print(f"❌ Runtime Playwright browser install failed: {ex}")
            return False

    try:
        # Set event loop policy for Windows compatibility
        if sys.platform == "win32":
            asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())
        # First attempt
        if _try_generate():
            return True
        
    except Exception as e:
        print(f"Playwright conversion failed: {e}")
        err_text = f"{e}\n{traceback.format_exc()}"
        # If browsers are not downloaded, try to fetch them once and retry
        if "Executable doesn't exist" in err_text or "playwright install" in err_text:
            if _install_playwright_browser_once():
                try:
                    if _try_generate():
                        return True
                except Exception as e2:
                    print(f"Retry after browser install failed: {e2}")
        # Additional debugging for Windows issues
        if "NotImplementedError" in str(e):
            print("Windows asyncio compatibility issue detected. Trying alternative approach...")
            try:
                # Alternative: Use subprocess to call playwright directly
                import subprocess
                import json
                
                # Create a simple script to run playwright
                script_content = f'''
import asyncio
import sys
from playwright.async_api import async_playwright

async def main():
    async with async_playwright() as p:
        browser = await p.chromium.launch(headless=True)
        page = await browser.new_page()
        await page.goto("file:///{os.path.abspath(html_path).replace(os.sep, '/')}", wait_until='networkidle')
        await page.pdf(
            path="{pdf_path.replace(os.sep, '/')}",
            format='A4',
            margin={{"top": "16mm", "bottom": "16mm", "left": "10mm", "right": "10mm"}},
            print_background=True,
            prefer_css_page_size=True
        )
        await browser.close()

if __name__ == "__main__":
    asyncio.run(main())
'''
                
                # Write temporary script
                script_path = os.path.join(os.path.dirname(pdf_path), 'temp_pdf_script.py')
                with open(script_path, 'w', encoding='utf-8') as f:
                    f.write(script_content)
                
                # Run script in subprocess
                result = subprocess.run([sys.executable, script_path], 
                                      capture_output=True, text=True, timeout=30)
                
                # Clean up
                if os.path.exists(script_path):
                    os.remove(script_path)
                
                if result.returncode == 0 and os.path.exists(pdf_path):
                    return True
                else:
                    print(f"Subprocess approach failed: {result.stderr}")
                    
            except Exception as e2:
                print(f"Alternative approach also failed: {e2}")
        
        return False


def html_to_pdf(html_path: str, pdf_path: str) -> bool:
    """Convert HTML to PDF using Playwright (mandatory)"""
    if PLAYWRIGHT_AVAILABLE:
        return html_to_pdf_playwright(html_path, pdf_path)
    else:
        print("❌ Playwright not available. PDF generation is mandatory!")
        print("Please install: pip install playwright && playwright install chromium")
        return False

def extract_first_page_pdf(input_pdf_path: str, output_pdf_path: str) -> bool:
    """Extract only the first page from a PDF file"""
    if not PYPDF_AVAILABLE:
        print("⚠️ PyPDF not available. Keeping original PDF.")
        # Copy the original file if PyPDF is not available
        try:
            shutil.copy2(input_pdf_path, output_pdf_path)
            return True
        except Exception as e:
            print(f"❌ Failed to copy PDF: {e}")
            return False
    
    try:
        # Read the input PDF
        reader = PdfReader(input_pdf_path)
        
        # Create a new PDF writer
        writer = PdfWriter()
        
        # Add only the first page (if it exists)
        if len(reader.pages) > 0:
            writer.add_page(reader.pages[0])
            
            # Write the first page to the output file
            with open(output_pdf_path, 'wb') as output_file:
                writer.write(output_file)
            
            print(f"✅ Extracted first page: {output_pdf_path}")
            return True
        else:
            print(f"⚠️ No pages found in PDF: {input_pdf_path}")
            return False
            
    except Exception as e:
        print(f"❌ Failed to extract first page from {input_pdf_path}: {e}")
        # Fallback: copy the original file
        try:
            shutil.copy2(input_pdf_path, output_pdf_path)
            return True
        except Exception as e2:
            print(f"❌ Failed to copy PDF as fallback: {e2}")
            return False

def process_invoices_html(data_file, template_path: str, company_name: str):
    """Process invoices using HTML template approach"""
    
    # Read customer data
    df = pd.read_excel(data_file, engine="openpyxl")
    df.columns = [str(c).strip().lower() for c in df.columns]
    
    # Create temporary directory for processing
    with tempfile.TemporaryDirectory() as temp_dir:
        invoices = []
        html_files = []
        pdf_files = []
        
        # Process each row as a separate invoice
        for i, r in df.iterrows():
            # Create invoice data structure
            invoice_data = {
                'Invoice No': safe_str(r.get("invoice no", f"INV/{i+1}")),
                'Invoice Date': safe_str(r.get("invoice date", "")),
                'Customer Name': safe_str(r.get("customer name", "")),
                'Customer Address': safe_str(r.get("customer address", "")),
                'Customer GSTIN': safe_str(r.get("customer_gstin", "")),
                'Customer PAN': safe_str(r.get("customer_pan", "")),
                'Customer CIN': safe_str(r.get("customer_cin", "")),
                'Customer State': safe_str(r.get("customer_state", "")),
                'PO No': safe_str(r.get("po_no", "")),
                'Total Amount': r.get("total amount", 0) or 0,
                'Items': [{
                    'Service Details': safe_str(r.get("service details", "")),
                    'HSN': safe_str(r.get("hsn", "")),
                    'Taxable Value': r.get("taxable value", 0) or 0,
                    'CGST %': r.get("cgst %", 0) or 0,
                    'SGST %': r.get("sgst %", 0) or 0,
                    'IGST %': r.get("igst %", 0) or 0,
                    # Tax amounts and total will be calculated dynamically
                }]
            }
            
            # Generate HTML file
            html_filename = f"{invoice_data['Invoice No']}_{company_name}.html"
            html_path = os.path.join(temp_dir, html_filename)
            
            # Fill template
            fill_html_template(template_path, invoice_data, html_path)
            html_files.append((html_filename, html_path))
            
            # Convert to PDF (mandatory with Playwright)
            pdf_filename = f"{invoice_data['Invoice No']}_{company_name}.pdf"
            pdf_path_temp = os.path.join(temp_dir, f"temp_{pdf_filename}")
            pdf_path_final = os.path.join(temp_dir, pdf_filename)
            
            if html_to_pdf(html_path, pdf_path_temp):
                # Extract only first page from the generated PDF
                if extract_first_page_pdf(pdf_path_temp, pdf_path_final):
                    pdf_files.append((pdf_filename, pdf_path_final))
                    # Clean up temporary PDF
                    if os.path.exists(pdf_path_temp):
                        os.remove(pdf_path_temp)
                else:
                    st.error(f"❌ Failed to extract first page for {invoice_data['Invoice No']}")
                    print(f"❌ First page extraction failed for {invoice_data['Invoice No']}")
            else:
                st.error(f"❌ Failed to generate PDF for {invoice_data['Invoice No']}")
                print(f"❌ PDF generation failed for {invoice_data['Invoice No']}")
            
            invoices.append(invoice_data)
        
        # Create ZIP file with results
        zip_buffer = io.BytesIO()
        with zipfile.ZipFile(zip_buffer, "w", zipfile.ZIP_DEFLATED) as zf:
            # Add HTML files
            for filename, filepath in html_files:
                zf.write(filepath, filename)
            
            # Add PDF files if available
            for filename, filepath in pdf_files:
                if os.path.exists(filepath):
                    zf.write(filepath, filename)
        
        zip_buffer.seek(0)
        return zip_buffer, len(invoices)

# -------------------------
# Streamlit UI
# -------------------------
st.set_page_config(page_title="HTML-Based Invoice Generator", layout="wide")
st.title("🌐 HTML-Based Invoice Generator — Inephos & Srestham")

st.markdown("""
Upload your customer data Excel file. The system will:
1. 📄 Generate individual HTML invoices using the template
2. 🎨 Apply beautiful styling and formatting
3. 📁 Convert to PDF (if weasyprint/playwright is available)
4. 📦 Package everything in a downloadable ZIP

**Benefits of HTML approach:**
- ✨ Perfect visual control and styling
- ⚡ Faster processing than Excel manipulation
- 🎯 Production-ready professional output
- 🔧 Easy to customize and maintain
""")

# Upload section
col1, col2 = st.columns(2)

with col1:
    st.subheader("📊 Customer Data")
    data_file = st.file_uploader("Upload customer Excel (.xlsx/.xlsm)", type=["xlsx", "xlsm"])
    
    if data_file:
        st.success("✅ Customer data uploaded")
        
        # Preview data
        try:
            preview_df = pd.read_excel(data_file, engine="openpyxl").head(3)
            st.write("**Data Preview:**")
            st.dataframe(preview_df)
        except Exception as e:
            st.error(f"Error reading file: {e}")

with col2:
    st.subheader("🎨 Template Selection")
    
    # Check available templates
    inephos_available = os.path.exists('inephos.html')
    srestham_available = os.path.exists('srestham.html')
    
    if inephos_available and srestham_available:
        st.success("✅ Both templates found")
        
        # Radio button for template selection
        selected_template = st.radio(
            "Select Company Template:",
            options=["Inephos", "Srestham"],
            horizontal=True,
            help="Choose which company's invoice template to use"
        )
        
        template_file = "inephos.html" if selected_template == "Inephos" else "srestham.html"
        st.info(f"Using: {template_file}")
        
    elif inephos_available:
        st.warning("⚠️ Only Inephos template found")
        selected_template = "Inephos"
        template_file = "inephos.html"
        
    elif srestham_available:
        st.warning("⚠️ Only Srestham template found")
        selected_template = "Srestham" 
        template_file = "srestham.html"
        
    else:
        st.error("❌ No templates found")
        st.write("Make sure inephos.html and/or srestham.html are in the same directory")
        selected_template = None
        template_file = None

# Processing section
if template_file:
    st.markdown("---")
    st.subheader("🚀 Generate Invoices")
    
    col3, col4 = st.columns(2)
    
    with col3:
        # Enable Inephos button only when Inephos is selected
        inephos_enabled = (selected_template == "Inephos")
        if st.button("🏢 Generate Inephos Invoices", 
                    use_container_width=True, 
                    disabled=not inephos_enabled,
                    help="Select Inephos template to enable this button"):
            if not data_file:
                st.error("Please upload customer data file.")
            else:
                with st.spinner("Generating Inephos invoices..."):
                    try:
                        zip_buffer, count = process_invoices_html(data_file, "inephos.html", "inephos")
                        st.success(f"✅ Generated {count} Inephos invoices successfully!")
                        
                        file_types = "HTML files and PDFs"
                        
                        st.download_button(
                            label=f"📥 Download ZIP ({file_types})",
                            data=zip_buffer,
                            file_name="inephos_invoices.zip",
                            mime="application/zip"
                        )
                    except Exception as e:
                        st.error(f"Error generating invoices: {e}")
                        st.exception(e)
    
    with col4:
        # Enable Srestham button only when Srestham is selected
        srestham_enabled = (selected_template == "Srestham")
        if st.button("🏢 Generate Srestham Invoices", 
                    use_container_width=True, 
                    disabled=not srestham_enabled,
                    help="Select Srestham template to enable this button"):
            if not data_file:
                st.error("Please upload customer data file.")
            else:
                with st.spinner("Generating Srestham invoices..."):
                    try:
                        zip_buffer, count = process_invoices_html(data_file, "srestham.html", "srestham")
                        st.success(f"✅ Generated {count} Srestham invoices successfully!")
                        
                        file_types = "HTML files and PDFs"
                        
                        st.download_button(
                            label=f"📥 Download ZIP ({file_types})",
                            data=zip_buffer,
                            file_name="srestham_invoices.zip",
                            mime="application/zip"
                        )
                    except Exception as e:
                        st.error(f"Error generating invoices: {e}")
                        st.exception(e)

# Information section
st.markdown("---")
st.subheader("ℹ️ Setup & Dependencies")

col5, col6 = st.columns(2)

with col5:
    st.markdown("""
    **Installation for PDF conversion:**
    ```bash
    # Playwright (mandatory for PDF generation)
    pip install playwright
    playwright install chromium
    
    # PyPDF (recommended for first-page extraction)
    pip install pypdf
    ```
    """)

with col6:
    st.markdown(f"""
    **Current Status:**
    - Playwright: {'✅ Available' if PLAYWRIGHT_AVAILABLE else '❌ Not installed (REQUIRED)'}
    - PyPDF: {'✅ Available' if PYPDF_AVAILABLE else '⚠️ Not installed (recommended)'}
    - Inephos Template: {'✅ Found' if os.path.exists('inephos.html') else '❌ Missing'}
    - Srestham Template: {'✅ Found' if os.path.exists('srestham.html') else '❌ Missing'}
    
    **Output:** HTML invoices + First-page PDFs (mandatory)
    """)

if not PLAYWRIGHT_AVAILABLE:
    st.error("🚨 **Playwright is required for PDF generation! Install it to continue.**")
    st.code("pip install playwright && playwright install chromium")