app.py

import io
# streamlit_invoice_generator.py
import os
import zipfile
from typing import Dict, List

import pandas as pd
import streamlit as st
from PIL import Image
from reportlab.lib.pagesizes import A4
from reportlab.pdfgen import canvas
from PyPDF2 import PdfReader, PdfWriter
from num2words import num2words   # ✅ added for number-to-words

# -------------------------
# Utility helpers
# -------------------------
PAGE_W, PAGE_H = A4

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

def format_amount(x):
    try:
        num = float(x)
        return f"{round(num):,}"   # ✅ rounds to nearest whole number with commas
    except Exception:
        return safe_str(x)

def to_words(value):   # ✅ helper for number to words
    try:
        num = float(value)
        if num.is_integer():
            num = int(num)
        return num2words(num, to="cardinal", lang="en").title() + " Only"
    except Exception:
        return ""

# overlay creation: draws text at specified positions
def create_overlay_pdf(invoice: dict, positions: dict, logo_path: str = None) -> io.BytesIO:
    packet = io.BytesIO()
    c = canvas.Canvas(packet, pagesize=A4)

    # draw fields (all keys in positions)
    for field, meta in positions.items():
        if field in ["logo", "items_start_y", "items_row_height", "items_columns"]:
            continue
        if not (isinstance(meta, tuple) and len(meta) == 5):
            continue
        val = invoice.get(field, "")
        x, y, fontname, fontsize, align = meta
        c.setFont(fontname, fontsize)

        if any(key in field.lower() for key in ["amount", "total"]):
            text = format_amount(val)
        else:
            text = safe_str(val)

        if align == "right":
            c.drawRightString(x, y, text)
        elif align == "center":
            c.drawCentredString(x, y, text)
        else:
            c.drawString(x, y, text)

    # draw items table
    if "items_start_y" in positions:
        y = positions["items_start_y"]
        row_height = positions.get("items_row_height", 18)
        col_map = positions.get("items_columns", {})
        for idx, it in enumerate(invoice.get("Items", []), start=1):
            x = col_map.get("sr")
            if x is not None:
                c.drawString(x, y, str(idx))
            x = col_map.get("desc")
            if x is not None:
                c.drawString(x, y, safe_str(it.get("Service Details", "")))
            x = col_map.get("hsn")
            if x is not None:
                c.drawString(x, y, safe_str(it.get("HSN", "")))
            x = col_map.get("taxable")
            if x is not None:
                c.drawRightString(x, y, format_amount(it.get("Taxable Value", 0)))
            x_perc = col_map.get("cgst_perc")
            if x_perc is not None:
                c.drawRightString(x_perc, y, safe_str(it.get("CGST %", "")))
            x_amt = col_map.get("cgst")
            if x_amt is not None:
                c.drawRightString(x_amt, y, format_amount(it.get("CGST Amount", 0)))
            x_perc = col_map.get("sgst_perc")
            if x_perc is not None:
                c.drawRightString(x_perc, y, safe_str(it.get("SGST %", "")))
            x_amt = col_map.get("sgst")
            if x_amt is not None:
                c.drawRightString(x_amt, y, format_amount(it.get("SGST Amount", 0)))
            x_perc = col_map.get("igst_perc")
            if x_perc is not None:
                c.drawRightString(x_perc, y, safe_str(it.get("IGST %", "")))
            x_amt = col_map.get("igst")
            if x_amt is not None:
                c.drawRightString(x_amt, y, format_amount(it.get("IGST Amount", 0)))
            x = col_map.get("total")
            if x is not None:
                c.drawRightString(x, y, format_amount(it.get("Total Amount", 0)))
            y -= row_height

        # ---- Draw TOTAL row ----
        totals = {
            "HSN": "",
            "Taxable Value": sum(it.get("Taxable Value", 0) for it in invoice.get("Items", [])),
            "CGST Amount": sum(it.get("CGST Amount", 0) for it in invoice.get("Items", [])),
            "SGST Amount": sum(it.get("SGST Amount", 0) for it in invoice.get("Items", [])),
            "IGST Amount": sum(it.get("IGST Amount", 0) for it in invoice.get("Items", [])),
            "Total Amount": sum(it.get("Total Amount", 0) for it in invoice.get("Items", [])),
        }

        y -= row_height  # extra gap before TOTAL row
        c.setFont("Helvetica", 9)

        x = col_map.get("taxable")
        if x is not None:
            c.drawRightString(x, y - 150, format_amount(totals["Taxable Value"]))

        x = col_map.get("cgst")
        if x is not None:
            c.drawRightString(x, y - 150, format_amount(totals["CGST Amount"]))

        x = col_map.get("sgst")
        if x is not None:
            c.drawRightString(x, y - 150, format_amount(totals["SGST Amount"]))

        x = col_map.get("igst")
        if x is not None:
            c.drawRightString(x, y - 150, format_amount(totals["IGST Amount"]))

        x = col_map.get("total")
        if x is not None:
            c.drawRightString(x, y - 150, format_amount(totals["Total Amount"]))

    # ✅ add "In Words" fields
    if "Total Invoice Words" in positions:
        total_amt = invoice.get("Total Amount", 0)
        x, y, fontname, fontsize, align = positions["Total Invoice Words"]
        c.setFont(fontname, fontsize)
        c.drawString(x, y, to_words(total_amt))

    if "CGST Words" in positions:
        cgst_amt = sum(it.get("CGST Amount", 0) for it in invoice.get("Items", []))
        x, y, fontname, fontsize, align = positions["CGST Words"]
        c.setFont(fontname, fontsize)
        c.drawString(x, y, to_words(cgst_amt))

    if "SGST Words" in positions:
        sgst_amt = sum(it.get("SGST Amount", 0) for it in invoice.get("Items", []))
        x, y, fontname, fontsize, align = positions["SGST Words"]
        c.setFont(fontname, fontsize)
        c.drawString(x, y, to_words(sgst_amt))

    if "IGST Words" in positions:
        igst_amt = sum(it.get("IGST Amount", 0) for it in invoice.get("Items", []))
        x, y, fontname, fontsize, align = positions["IGST Words"]
        c.setFont(fontname, fontsize)
        c.drawString(x, y, to_words(igst_amt))

    # ✅ Always show Rounding Off = 0
    if "Rounding Off" in positions:
        x, y, fontname, fontsize, align = positions["Rounding Off"]
        c.setFont(fontname, fontsize)
        c.drawRightString(x, y, "0")

    c.save()
    packet.seek(0)
    return packet

def merge_overlay_with_template(template_bytes: bytes, overlay_bytes: bytes) -> bytes:
    template_reader = PdfReader(io.BytesIO(template_bytes))
    overlay_reader = PdfReader(io.BytesIO(overlay_bytes))
    writer = PdfWriter()
    template_page = template_reader.pages[0]
    template_page.merge_page(overlay_reader.pages[0])
    writer.add_page(template_page)
    out = io.BytesIO()
    writer.write(out)
    out.seek(0)
    return out.read()

# -------------------------
# Streamlit UI
# -------------------------
st.set_page_config(page_title="Tax Invoice Generator", layout="wide")

# ====== UI: Styles & Header ======
st.markdown(
    """
    <style>
      :root {
        --brand: #2457f5;
        --brand-2: #0ea5e9;
        --text: #0f172a;
        --muted: #475569;
        --bg-soft: #f8fafc;
        --card-border: #e2e8f0;
      }
      .app-header {
        background: linear-gradient(90deg, rgba(36,87,245,.08), rgba(14,165,233,.08));
        border: 1px solid var(--card-border);
        border-radius: 12px;
        padding: 18px 20px;
        margin-bottom: 10px;
      }
      .app-title { margin: 0; font-size: 28px; color: var(--text); }
      .app-sub { margin: 6px 0 0; color: var(--muted); }
      .section-title { font-size: 16px; margin: 10px 0 6px; color: var(--text); }
      .tip { color: var(--muted); font-size: 14px; }
      /* Uploader */
      [data-testid="stFileUploadDropzone"] {
        border-radius: 12px;
        border: 1px dashed var(--card-border);
        background: var(--bg-soft);
      }
      /* Buttons */
      div.stButton > button {
        border-radius: 10px;
        border: 1px solid var(--card-border);
        background: linear-gradient(180deg, white, #f3f6fb);
        color: var(--text);
        padding: 10px 14px;
      }
      div.stButton > button:hover { border-color: #cbd5e1; background: #eef2f8; }
      /* Download buttons */
      [data-testid="stDownloadButton"] > button {
        border-radius: 10px; padding: 10px 14px; font-weight: 600;
        background: linear-gradient(90deg, var(--brand), var(--brand-2));
        border: none; color: white;
      }
      /* Containers & spacing */
      .block-container { padding-top: 1rem; }
    </style>
    <div class="app-header">
      <h1 class="app-title">Tax Invoice Generator</h1>
      <p class="app-sub">Professional invoices for Inephos & Srestham from your Excel data</p>
    </div>
    """,
    unsafe_allow_html=True,
)

with st.expander("How it works", expanded=True):
    st.markdown(
        "- Upload a single-sheet Excel file with your invoice data.\n"
        "- Choose the company template and click Generate.\n"
        "- Download a ZIP with professionally formatted PDFs."
    )

# ✅ Load templates internally
with open("uploads/inephos_template.pdf", "rb") as f:
    template_inephos_bytes = f.read()

with open("uploads/srestham_template.pdf", "rb") as f:
    template_srestham_bytes = f.read()

# --- Layout: Upload in center, buttons angled outward ---
st.markdown("<div class='section-title'>1) Upload your data</div>", unsafe_allow_html=True)
col1, col2, col3 = st.columns([1,2,1])
with col2:
    data_file = st.file_uploader("Upload customer Excel (.xlsx/.xlsm)", type=["xlsx", "xlsm"]) 
    st.caption("Tip: Keep column headers simple like 'invoice no', 'taxable value', 'cgst %', etc.")
    # Preview uploaded file (non-destructive; resets pointer afterwards)
    if data_file is not None:
        try:
            preview_df = pd.read_excel(data_file, engine="openpyxl")
            st.markdown("**Preview**")
            st.dataframe(preview_df.head(5), width='stretch')
            detected_cols = ", ".join([str(c).strip().lower() for c in preview_df.columns])
            st.caption(f"Detected columns: {detected_cols}")
        except Exception as e:
            st.warning(f"Could not preview file: {e}")
        finally:
            try:
                data_file.seek(0)
            except Exception:
                pass

# --- Buttons appear like branches ---
st.markdown("<div class='section-title'>2) Generate invoices</div>", unsafe_allow_html=True)
col1, col2, col3, col4 = st.columns([1.5,1,1,1.5])

# -------------------------
# Invoice generation helpers
# -------------------------
DEFAULT_POSITIONS = {
    "Invoice No":    (120, 645, "Helvetica", 8, "left"),
    "Invoice Date":  (368, 645, "Helvetica", 8, "left"),
    "Customer Name": (55, 615, "Helvetica", 10, "left"),
    "Customer Address": (55, 600, "Helvetica", 9, "left"),

    # New fields:
    "GSTIN": (362, 621, "Helvetica", 8, "left"),
    "PAN":   (362, 607, "Helvetica", 8, "left"),
    "CIN":   (362, 594, "Helvetica", 8, "left"),
    "PO No": (362, 582, "Helvetica", 8, "left"),
    "State": (362, 569, "Helvetica", 8, "left"),

    "items_start_y": 500,
    "items_row_height": 30,
    "items_columns": {
        "sr": 56,
        "desc": 75,
        "hsn": 225,
        "taxable": 298,
        "cgst_perc": 311,
        "cgst": 345,
        "sgst_perc": 357,
        "sgst": 396,
        "igst_perc": 411,
        "igst": 447,
        "total": 505
    },

    "Total Amount": (506, 265, "Helvetica", 9, "right"),
    "Total Invoice Words": (228, 251, "Helvetica", 9, "left"),
    "CGST Words": (228, 236, "Helvetica", 9, "left"),
    "SGST Words": (228, 222, "Helvetica", 9, "left"),
    "IGST Words": (228, 208, "Helvetica", 9, "left"),

    # ✅ Position for Rounding Off
    "Rounding Off": (506, 277, "Helvetica", 9, "right"),
}

def build_invoice_dict(r, group=None, inv_no=None):
    """Helper to build invoice dict with new fields — always sum Total Amount from items"""
    if group is not None:
        total_amount = 0
        for _, row in group.iterrows():
            taxable = row.get("taxable value", 0) or 0
            cgst_amt = taxable * (row.get("cgst %", 0) or 0) / 100
            sgst_amt = taxable * (row.get("sgst %", 0) or 0) / 100
            igst_amt = taxable * (row.get("igst %", 0) or 0) / 100
            total_amount += taxable + cgst_amt + sgst_amt + igst_amt
    else:
        taxable = r.get("taxable value", 0) or 0
        cgst_amt = taxable * (r.get("cgst %", 0) or 0) / 100
        sgst_amt = taxable * (r.get("sgst %", 0) or 0) / 100
        igst_amt = taxable * (r.get("igst %", 0) or 0) / 100
        total_amount = taxable + cgst_amt + sgst_amt + igst_amt

    return {
        "Invoice No": safe_str(inv_no if inv_no else r.get("invoice no", "")),
        "Invoice Date": safe_str(r.get("invoice date","")),
        "Customer Name": safe_str(r.get("customer name","")),
        "Customer Address": safe_str(r.get("customer address","")),
        "GSTIN": safe_str(r.get("gstin","")),
        "PAN": safe_str(r.get("pan","")),
        "CIN": safe_str(r.get("cin","")),
        "PO No": safe_str(r.get("po no","")),
        "State": safe_str(r.get("state","")),
        "Total Amount": total_amount,
    }

def build_items(group_or_row):
    """Build item rows; calculate tax amounts from % columns"""
    taxable_val = group_or_row.get("taxable value", 0) or 0

    # --- Get tax % ---
    cgst_perc = group_or_row.get("cgst %", 0) or 0
    sgst_perc = group_or_row.get("sgst %", 0) or 0
    igst_perc = group_or_row.get("igst %", 0) or 0

    # --- Calculate tax amounts ---
    cgst_amt = taxable_val * cgst_perc / 100
    sgst_amt = taxable_val * sgst_perc / 100
    igst_amt = taxable_val * igst_perc / 100

    # --- Calculate total ---
    total_amt = taxable_val + cgst_amt + sgst_amt + igst_amt

    return {
        "Service Details": safe_str(group_or_row.get("service details","")),
        "HSN": safe_str(group_or_row.get("hsn","")),
        "Taxable Value": taxable_val,
        "CGST %": cgst_perc,
        "SGST %": sgst_perc,
        "IGST %": igst_perc,
        "CGST Amount": cgst_amt,
        "SGST Amount": sgst_amt,
        "IGST Amount": igst_amt,
        "Total Amount": total_amt,
    }

# -------------------------
# Invoice generation buttons (angled outward)
# -------------------------
with col2:
    if st.button("🏢 Generate Inephos Invoices"):
        if not data_file:
            st.error("Please upload the customer Excel.")
        else:
            with st.spinner("Generating Inephos PDF invoices…"):
                df = pd.read_excel(data_file, engine="openpyxl")
                df.columns = [str(c).strip().lower() for c in df.columns]

                invoices = []
                if "invoice no" in df.columns:
                    grouped = df.groupby("invoice no")
                    for inv_no, group in grouped:
                        first = group.iloc[0]
                        items = [build_items(r) for _, r in group.iterrows()]
                        inv = build_invoice_dict(first, group, inv_no)
                        inv["Items"] = items
                        invoices.append(inv)
                else:
                    for i, r in df.iterrows():
                        inv = build_invoice_dict(r)
                        inv["Items"] = [build_items(r)]
                        invoices.append(inv)

                zip_buffer = io.BytesIO()
                with zipfile.ZipFile(zip_buffer, "w", zipfile.ZIP_DEFLATED) as zf:
                    for inv in invoices:
                        overlay = create_overlay_pdf(inv, DEFAULT_POSITIONS, logo_path=None)
                        final_pdf_bytes = merge_overlay_with_template(template_inephos_bytes, overlay.read())
                        filename = f"{inv.get('Invoice No')}_inephos.pdf"
                        zf.writestr(filename, final_pdf_bytes)
                zip_buffer.seek(0)
                st.success(f"✅ Generated {len(invoices)} invoices for Inephos.")
                st.download_button("📥 Download ZIP — Inephos", data=zip_buffer, file_name="inephos_invoices.zip")

with col3:
    if st.button("🏢 Generate Srestham Invoices"):
        if not data_file:
            st.error("Please upload the customer Excel.")
        else:
            with st.spinner("Generating Srestham PDF invoices…"):
                df = pd.read_excel(data_file, engine="openpyxl")
                df.columns = [str(c).strip().lower() for c in df.columns]

                invoices = []
                if "invoice no" in df.columns:
                    grouped = df.groupby("invoice no")
                    for inv_no, group in grouped:
                        first = group.iloc[0]
                        items = [build_items(r) for _, r in group.iterrows()]
                        inv = build_invoice_dict(first, group, inv_no)
                        inv["Items"] = items
                        invoices.append(inv)
                else:
                    for i, r in df.iterrows():
                        inv = build_invoice_dict(r)
                        inv["Items"] = [build_items(r)]
                        invoices.append(inv)

                zip_buffer = io.BytesIO()
                with zipfile.ZipFile(zip_buffer, "w", zipfile.ZIP_DEFLATED) as zf:
                    for inv in invoices:
                        overlay = create_overlay_pdf(inv, DEFAULT_POSITIONS, logo_path=None)
                        final_pdf_bytes = merge_overlay_with_template(template_srestham_bytes, overlay.read())
                        filename = f"{inv.get('Invoice No')}_srestham.pdf"
                        zf.writestr(filename, final_pdf_bytes)
                zip_buffer.seek(0)
                st.success(f"✅ Generated {len(invoices)} invoices for Srestham.")
                st.download_button("📥 Download ZIP — Srestham", data=zip_buffer, file_name="srestham_invoices.zip")

# ====== Footer ======
st.divider()
st.caption("Built for reliable invoice creation.")