"""
@helper InvoiceGenerator (Backend/app/core/invoice_generator.py)
@purpose Utilities to compile standard Letter-sized PDF invoices and compact 80mm thermal roll receipts on-the-fly using ReportLab.
"""
from io import BytesIO
from reportlab.lib.pagesizes import letter
from reportlab.lib import colors
from reportlab.lib.units import inch
from PIL import Image as PILImage
from reportlab.platypus import SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle, PageBreak, Image as RLImage
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_CENTER, TA_RIGHT, TA_LEFT
from datetime import datetime
import json
import os
from pathlib import Path

def get_invoice_logo_element(max_w=2.0 * inch, max_h=0.8 * inch):
    """
    Finds the latest uploaded invoice branding logo in uploads/invoice_branding/logo/
    and returns a ReportLab RLImage element.
    """
    backend_root = Path(__file__).resolve().parents[2]
    logo_dir = backend_root / "uploads" / "invoice_branding" / "logo"
    
    if logo_dir.exists():
        # Get active non-variant files sorted by modification time
        files = [f for f in logo_dir.glob("*.*") if not any(s in f.name for s in ["_thumbnail", "_medium", "_large", "_raw"])]
        if not files:
            files = list(logo_dir.glob("*.*"))
            
        files = sorted(files, key=os.path.getmtime, reverse=True)
        for logo_file in files:
            try:
                pil_img = PILImage.open(logo_file)
                bio = BytesIO()
                if pil_img.mode in ("RGBA", "P"):
                    pil_img = pil_img.convert("RGBA")
                else:
                    pil_img = pil_img.convert("RGB")
                    
                pil_img.save(bio, format="PNG")
                bio.seek(0)
                
                w, h = pil_img.size
                if w <= 0 or h <= 0:
                    continue
                aspect = h / float(w)
                render_w = max_w
                render_h = max_w * aspect
                if render_h > max_h:
                    render_h = max_h
                    render_w = max_h / aspect
                    
                return RLImage(bio, width=render_w, height=render_h)
            except Exception as e:
                print(f"Error loading logo {logo_file}: {e}")
                continue
    return None

def get_invoice_branding_data(db=None):
    company_name = "iFixKart"
    gstin = "33AAAAA0000A1Z5"
    address = "Offline Main Store Counter, Chennai | +91 9876543210"
    gst_rate = 18.0
    
    if db:
        try:
            from app.models.SettingModel import Setting
            setting = db.query(Setting).filter(Setting.setting_key == "invoice_branding").first()
            if setting and setting.setting_value:
                val = setting.setting_value
                if isinstance(val, dict):
                    company_name = val.get("companyName") or company_name
                    gstin = val.get("gstin") or gstin
                    address = val.get("storeAddress") or address
                    if "gstRate" in val and val["gstRate"] is not None:
                        try:
                            gst_rate = float(val["gstRate"])
                        except (ValueError, TypeError):
                            pass
        except Exception:
            pass
            
    return {
        "companyName": company_name,
        "gstin": gstin,
        "storeAddress": address,
        "gstRate": gst_rate
    }

def generate_invoice_pdf(order, customer, order_items, db=None) -> bytes:
    """
    Generate a professional standard Letter-size GST Invoice on-the-fly.
    """
    buffer = BytesIO()
    doc = SimpleDocTemplate(
        buffer,
        pagesize=letter,
        rightMargin=36,
        leftMargin=36,
        topMargin=36,
        bottomMargin=36
    )

    styles = getSampleStyleSheet()
    
    # Custom styles
    title_style = ParagraphStyle(
        'InvoiceTitle',
        parent=styles['Heading1'],
        fontName='Helvetica-Bold',
        fontSize=22,
        textColor=colors.HexColor('#1b2559'),
        spaceAfter=4
    )
    
    subtitle_style = ParagraphStyle(
        'InvoiceSubtitle',
        parent=styles['Normal'],
        fontName='Helvetica-Bold',
        fontSize=10,
        textColor=colors.HexColor('#e4382f'),
        spaceAfter=10
    )
    
    label_style = ParagraphStyle(
        'MetaLabel',
        parent=styles['Normal'],
        fontName='Helvetica-Bold',
        fontSize=9,
        textColor=colors.HexColor('#94a3b8'),
        spaceAfter=3
    )

    text_style = ParagraphStyle(
        'MetaText',
        parent=styles['Normal'],
        fontName='Helvetica',
        fontSize=9,
        textColor=colors.HexColor('#1e293b'),
        spaceAfter=3
    )

    bold_text_style = ParagraphStyle(
        'MetaTextBold',
        parent=styles['Normal'],
        fontName='Helvetica-Bold',
        fontSize=9,
        textColor=colors.HexColor('#1e293b'),
        spaceAfter=3
    )

    story = []

    # 1. Header (Logo/Title & Metadata)
    logo_element = get_invoice_logo_element(max_w=2.2 * inch, max_h=0.85 * inch)
    
    left_cell = []
    if logo_element:
        left_cell.append(logo_element)
    else:
        left_cell.append(Paragraph("GST INVOICE", title_style))
        left_cell.append(Paragraph("iFixKart Solutions Platform", subtitle_style))

    header_data = [
        [
            left_cell,
            Paragraph(f"<b>GST INVOICE</b><br/><b>Invoice No:</b> INV-{order.order_no.split('-')[-1]}<br/><b>Date:</b> {order.created_at.strftime('%d-%b-%Y')}<br/><b>Status:</b> {order.status}", ParagraphStyle('RightText', parent=text_style, alignment=TA_RIGHT))
        ]
    ]
    
    header_table = Table(header_data, colWidths=[3.5 * inch, 4.0 * inch])
    header_table.setStyle(TableStyle([
        ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ('BOTTOMPADDING', (0,0), (-1,-1), 0),
        ('TOPPADDING', (0,0), (-1,-1), 0),
    ]))
    story.append(header_table)
    story.append(Spacer(1, 15))

    # 2. Billing & Store Coordinates
    branding = get_invoice_branding_data(db)
    seller_html = f"<b>{branding['companyName']}</b><br/>{branding['storeAddress']}<br/><b>GSTIN:</b> {branding['gstin']}"

    # Parse shipping address
    cust_addr_str = "Customer Billing Details"
    if order.shipping_address_json:
        try:
            addr = json.loads(order.shipping_address_json)
            cust_addr_str = f"<b>{addr.get('full_name')}</b><br/>{addr.get('street_address')}<br/>{addr.get('city')}, {addr.get('state')} - {addr.get('pincode')}<br/>Phone: {addr.get('phone')}"
        except Exception:
            cust_addr_str = order.shipping_address_json

    details_data = [
        [
            Paragraph("SELLER (IFIXKART STORE)", label_style),
            Paragraph("BILLED TO (CUSTOMER)", label_style)
        ],
        [
            Paragraph(seller_html, text_style),
            Paragraph(cust_addr_str, text_style)
        ]
    ]
    details_table = Table(details_data, colWidths=[3.75 * inch, 3.75 * inch])
    details_table.setStyle(TableStyle([
        ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ('BACKGROUND', (0,0), (-1,-1), colors.HexColor('#f8fafc')),
        ('PADDING', (0,0), (-1,-1), 10),
        ('BOX', (0,0), (-1,-1), 0.5, colors.HexColor('#e2e8f0')),
    ]))
    story.append(details_table)
    story.append(Spacer(1, 20))

    # 3. Items Table
    th_style = ParagraphStyle('TH', parent=styles['Normal'], fontName='Helvetica-Bold', fontSize=9, textColor=colors.white)
    th_right = ParagraphStyle('THR', parent=styles['Normal'], fontName='Helvetica-Bold', fontSize=9, textColor=colors.white, alignment=TA_RIGHT)
    
    td_style = ParagraphStyle('TD', parent=styles['Normal'], fontName='Helvetica', fontSize=9, textColor=colors.HexColor('#334155'))
    td_right = ParagraphStyle('TDR', parent=styles['Normal'], fontName='Helvetica', fontSize=9, textColor=colors.HexColor('#334155'), alignment=TA_RIGHT)

    table_data = [[
        Paragraph("S.No", th_style),
        Paragraph("Item SKU & Name", th_style),
        Paragraph("Unit Price", th_right),
        Paragraph("Qty", th_right),
        Paragraph("Total Price", th_right)
    ]]

    for idx, item in enumerate(order_items):
        table_data.append([
            Paragraph(str(idx + 1), td_style),
            Paragraph(f"<b>{item.sku}</b> - {item.product_name}", td_style),
            Paragraph(f"Rs. {float(item.unit_price):.2f}", td_right),
            Paragraph(str(item.quantity), td_right),
            Paragraph(f"Rs. {float(item.total_price):.2f}", td_right)
        ])

    items_table = Table(table_data, colWidths=[0.5 * inch, 3.8 * inch, 1.1 * inch, 0.6 * inch, 1.5 * inch])
    items_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,0), colors.HexColor('#1b2559')),
        ('ALIGN', (0,0), (-1,-1), 'LEFT'),
        ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
        ('BOTTOMPADDING', (0,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 8),
        ('GRID', (0,0), (-1,-1), 0.5, colors.HexColor('#cbd5e1')),
    ]))
    story.append(items_table)
    story.append(Spacer(1, 15))

    # 4. Totals & Tax Calculation Breakdown
    subtotal = float(order.total_amount)
    tax_amount = float(order.tax_amount)
    gst_rate = float(branding.get("gstRate", 18.0))
    half_rate = round(gst_rate / 2.0, 1)
    cgst = round(tax_amount / 2, 2)
    sgst = round(tax_amount / 2, 2)
    igst = 0.0

    totals_data = [
        [Paragraph("", text_style), Paragraph("Taxable Value:", label_style), Paragraph(f"Rs. {subtotal:.2f}", td_right)],
        [Paragraph("", text_style), Paragraph(f"CGST ({half_rate:.1f}%):", label_style), Paragraph(f"Rs. {cgst:.2f}", td_right)],
        [Paragraph("", text_style), Paragraph(f"SGST ({half_rate:.1f}%):", label_style), Paragraph(f"Rs. {sgst:.2f}", td_right)],
        [Paragraph("", text_style), Paragraph("IGST (0.0%):", label_style), Paragraph(f"Rs. {igst:.2f}", td_right)],
        [Paragraph("", text_style), Paragraph("<b>Grand Total:</b>", ParagraphStyle('GrandLabel', parent=label_style, fontSize=11, textColor=colors.HexColor('#1b2559'))), Paragraph(f"<b>Rs. {float(order.final_amount):.2f}</b>", ParagraphStyle('GrandVal', parent=td_right, fontSize=11, fontName='Helvetica-Bold', textColor=colors.HexColor('#1b2559')))]
    ]
    
    totals_table = Table(totals_data, colWidths=[4.2 * inch, 1.8 * inch, 1.5 * inch])
    totals_table.setStyle(TableStyle([
        ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
        ('LINEBELOW', (1,0), (-1,-2), 0.5, colors.HexColor('#e2e8f0')),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
    ]))
    story.append(totals_table)
    story.append(Spacer(1, 50))

    # 5. Legal Footer
    footer_text = Paragraph(
        "This is a computer-generated GST Tax Invoice. No signature is required. Thank you for choosing iFixKart!",
        ParagraphStyle('Footer', parent=styles['Normal'], fontName='Helvetica-Oblique', fontSize=8, textColor=colors.HexColor('#94a3b8'), alignment=TA_CENTER)
    )
    story.append(footer_text)

    doc.build(story)
    pdf_bytes = buffer.getvalue()
    buffer.close()
    return pdf_bytes

def generate_thermal_invoice_pdf(order, customer, order_items) -> bytes:
    """
    Generate an 80mm thermal roll print receipt (walking invoice format) on-the-fly.
    Page width is exactly 80mm (approx 226 pt). Page length is dynamic/extended (e.g. 450 pt).
    """
    buffer = BytesIO()
    
    # 80mm roll size: 226pt wide, 450pt tall
    doc = SimpleDocTemplate(
        buffer,
        pagesize=(226, 450),
        rightMargin=10,
        leftMargin=10,
        topMargin=15,
        bottomMargin=15
    )

    styles = getSampleStyleSheet()
    
    title_style = ParagraphStyle(
        'ThermalTitle',
        parent=styles['Heading2'],
        fontName='Helvetica-Bold',
        fontSize=12,
        textColor=colors.black,
        alignment=TA_CENTER,
        spaceAfter=2
    )

    subtitle_style = ParagraphStyle(
        'ThermalSubtitle',
        parent=styles['Normal'],
        fontName='Helvetica-Bold',
        fontSize=8,
        textColor=colors.black,
        alignment=TA_CENTER,
        spaceAfter=10
    )

    text_style = ParagraphStyle(
        'ThermalText',
        parent=styles['Normal'],
        fontName='Helvetica',
        fontSize=7,
        textColor=colors.black,
        spaceAfter=2
    )

    text_right = ParagraphStyle(
        'ThermalTextRight',
        parent=text_style,
        alignment=TA_RIGHT
    )

    story = []

    # 1. Header
    thermal_logo = get_invoice_logo_element(max_w=1.8 * inch, max_h=0.6 * inch)
    if thermal_logo:
        thermal_logo.hAlign = 'CENTER'
        story.append(thermal_logo)
        story.append(Spacer(1, 4))
        
    story.append(Paragraph("iFixKart Retail POS", title_style))
    story.append(Paragraph("Solutions Pvt Ltd - Store #1<br/>100 Tech Arcade Main Road, Chennai<br/>GSTIN: 33AAFCI8824J1ZP", subtitle_style))
    story.append(Spacer(1, 5))

    # 2. Transaction Meta Info
    story.append(Paragraph(f"<b>Invoice:</b> walk_inv_{order.order_id[:8]}", text_style))
    story.append(Paragraph(f"<b>Order No:</b> {order.order_no}", text_style))
    story.append(Paragraph(f"<b>Date:</b> {order.created_at.strftime('%d-%b-%Y %H:%M')}", text_style))
    payment_method = getattr(order, "payment_method", None) or "COD"
    story.append(Paragraph(f"<b>Payment:</b> {payment_method} ({order.payment_status})", text_style))
    story.append(Spacer(1, 10))

    # 3. Item List Header
    item_header = [
        [Paragraph("<b>Item Description</b>", text_style), Paragraph("<b>Qty</b>", text_right), Paragraph("<b>Total</b>", text_right)]
    ]
    
    # 4. Item List Rows
    for item in order_items:
        # Truncate long names to save receipt slip width
        short_name = item.product_name[:24] + '..' if len(item.product_name) > 26 else item.product_name
        item_header.append([
            Paragraph(f"{item.sku}<br/>{short_name}", text_style),
            Paragraph(str(item.quantity), text_right),
            Paragraph(f"Rs. {float(item.total_price):.1f}", text_right)
        ])

    # Table Widths: item=120pt, qty=30pt, total=56pt -> Total 206pt
    items_table = Table(item_header, colWidths=[120, 30, 56])
    items_table.setStyle(TableStyle([
        ('LINEBELOW', (0,0), (-1,0), 0.5, colors.black),
        ('LINEBELOW', (0,-1), (-1,-1), 0.5, colors.black),
        ('PADDING', (0,0), (-1,-1), 3),
        ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
    ]))
    story.append(items_table)
    story.append(Spacer(1, 8))

    # 5. Taxes & Total Breakout
    tax_amount = float(order.tax_amount)
    cgst = round(tax_amount / 2, 2)
    sgst = round(tax_amount / 2, 2)

    totals_data = [
        [Paragraph("Taxable Value:", text_style), Paragraph(f"Rs. {float(order.total_amount):.2f}", text_right)],
        [Paragraph("CGST (9%):", text_style), Paragraph(f"Rs. {cgst:.2f}", text_right)],
        [Paragraph("SGST (9%):", text_style), Paragraph(f"Rs. {sgst:.2f}", text_right)],
        [Paragraph("<b>Grand Total:</b>", ParagraphStyle('GrandLabelThermal', parent=text_style, fontName='Helvetica-Bold', fontSize=9)), Paragraph(f"<b>Rs. {float(order.final_amount):.2f}</b>", ParagraphStyle('GrandValThermal', parent=text_right, fontName='Helvetica-Bold', fontSize=9))]
    ]
    
    totals_table = Table(totals_data, colWidths=[110, 96])
    totals_table.setStyle(TableStyle([
        ('LINEABOVE', (0,-1), (-1,-1), 0.5, colors.black),
        ('PADDING', (0,0), (-1,-1), 2),
    ]))
    story.append(totals_table)
    story.append(Spacer(1, 20))

    # 6. Thermal Footer
    story.append(Paragraph("Thank you for your purchase!", ParagraphStyle('F1', parent=text_style, fontName='Helvetica-Bold', alignment=TA_CENTER)))
    story.append(Paragraph("For support: support@ifixkart.com", ParagraphStyle('F2', parent=text_style, alignment=TA_CENTER)))

    doc.build(story)
    pdf_bytes = buffer.getvalue()
    buffer.close()
    return pdf_bytes