"""
Export Engine — Generates downloadable files from extracted JSON field data.

Supported formats:
  - CSV:  Python csv module
  - XLSX: openpyxl with styled headers
  - DOCX: python-docx with a formatted field-value table
  - PDF:  ReportLab with a clean, professional layout
"""
import csv
import io
from pathlib import Path

from openpyxl import Workbook
from openpyxl.styles import Font, PatternFill, Alignment, Border, Side
from docx import Document
from docx.shared import Inches, Pt, RGBColor
from docx.enum.table import WD_TABLE_ALIGNMENT
from reportlab.lib import colors
from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import mm
from reportlab.platypus import SimpleDocTemplate, Table, TableStyle, Paragraph, Spacer

from models.schemas import ExtractedField


def export_to_csv(fields: list[ExtractedField], filename: str = "export") -> bytes:
    """Generate a CSV file from extracted fields."""
    output = io.StringIO()
    writer = csv.writer(output)

    # Header row
    writer.writerow(["Field Name", "Extracted Value"])

    # Data rows
    for field in fields:
        writer.writerow([field.name, field.value])

    return output.getvalue().encode("utf-8-sig")  # BOM for Excel compatibility


def export_to_xlsx(fields: list[ExtractedField], filename: str = "export") -> bytes:
    """Generate a styled XLSX file from extracted fields."""
    wb = Workbook()
    ws = wb.active
    ws.title = "Extracted Data"

    # Styles
    header_font = Font(name="Calibri", bold=True, size=12, color="FFFFFF")
    header_fill = PatternFill(start_color="556B2F", end_color="556B2F", fill_type="solid")  # Olive
    header_alignment = Alignment(horizontal="center", vertical="center", wrap_text=True)
    cell_font = Font(name="Calibri", size=11)
    cell_alignment = Alignment(vertical="top", wrap_text=True)
    thin_border = Border(
        left=Side(style="thin"),
        right=Side(style="thin"),
        top=Side(style="thin"),
        bottom=Side(style="thin"),
    )

    # Headers
    headers = ["Field Name", "Extracted Value"]
    for col, header in enumerate(headers, start=1):
        cell = ws.cell(row=1, column=col, value=header)
        cell.font = header_font
        cell.fill = header_fill
        cell.alignment = header_alignment
        cell.border = thin_border

    # Data rows
    for row_idx, field in enumerate(fields, start=2):
        # Openpyxl has a 32767 character limit per cell
        safe_val = str(field.value)
        if len(safe_val) > 32000:
            safe_val = safe_val[:32000] + "... [TRUNCATED]"
            
        ws.cell(row=row_idx, column=1, value=field.name).font = cell_font
        ws.cell(row=row_idx, column=2, value=safe_val).font = cell_font

        for col in range(1, 3):
            ws.cell(row=row_idx, column=col).alignment = cell_alignment
            ws.cell(row=row_idx, column=col).border = thin_border

    # Auto-width columns
    ws.column_dimensions["A"].width = 30
    ws.column_dimensions["B"].width = 60

    # Save to bytes
    output = io.BytesIO()
    wb.save(output)
    return output.getvalue()


def export_to_docx(fields: list[ExtractedField], filename: str = "export") -> bytes:
    """Generate a formatted DOCX file from extracted fields."""
    doc = Document()

    # Title
    title = doc.add_heading("Puff n Parse — Extracted Data", level=1)
    title_run = title.runs[0]
    title_run.font.color.rgb = RGBColor(0x55, 0x6B, 0x2F)  # Olive

    doc.add_paragraph(f"Total fields extracted: {len(fields)}")
    doc.add_paragraph("")

    # Create a table with field data
    table = doc.add_table(rows=1, cols=2)
    table.alignment = WD_TABLE_ALIGNMENT.CENTER
    table.style = "Light Grid Accent 3"

    # Header row
    header_cells = table.rows[0].cells
    header_cells[0].text = "Field Name"
    header_cells[1].text = "Extracted Value"

    for cell in header_cells:
        for paragraph in cell.paragraphs:
            for run in paragraph.runs:
                run.font.bold = True
                run.font.size = Pt(11)

    # Data rows
    for field in fields:
        row_cells = table.add_row().cells
        row_cells[0].text = field.name
        
        safe_val = str(field.value)
        if len(safe_val) > 32000:
            safe_val = safe_val[:32000] + "... [TRUNCATED]"
        row_cells[1].text = safe_val

    # Footer
    doc.add_paragraph("")
    footer = doc.add_paragraph("Generated by Puff n Parse — From B 2 C")
    footer.runs[0].font.size = Pt(8)
    footer.runs[0].font.color.rgb = RGBColor(0x99, 0x99, 0x99)

    # Save to bytes
    output = io.BytesIO()
    doc.save(output)
    return output.getvalue()


def export_to_pdf(fields: list[ExtractedField], filename: str = "export") -> bytes:
    """Generate a clean, professional PDF from extracted fields."""
    output = io.BytesIO()
    doc = SimpleDocTemplate(
        output,
        pagesize=A4,
        topMargin=20 * mm,
        bottomMargin=20 * mm,
        leftMargin=15 * mm,
        rightMargin=15 * mm,
    )

    styles = getSampleStyleSheet()

    # Custom styles
    title_style = ParagraphStyle(
        "CustomTitle",
        parent=styles["Title"],
        fontSize=18,
        textColor=colors.HexColor("#556B2F"),
        spaceAfter=12,
    )
    normal_style = ParagraphStyle(
        "CustomNormal",
        parent=styles["Normal"],
        fontSize=10,
        leading=14,
    )

    elements = []

    # Title
    elements.append(Paragraph("Puff n Parse — Extracted Data", title_style))
    elements.append(Paragraph(f"Total fields extracted: {len(fields)}", normal_style))
    elements.append(Spacer(1, 12))

    import xml.sax.saxutils as saxutils

    field_name_style = ParagraphStyle(
        "FieldName",
        parent=styles["Normal"],
        fontSize=11,
        fontName="Helvetica-Bold",
        textColor=colors.HexColor("#556B2F"),
        spaceAfter=4,
    )

    for field in fields:
        safe_name = saxutils.escape(str(field.name)).replace('\n', '<br/>')
        
        safe_val_str = str(field.value)
        if len(safe_val_str) > 32000:
            safe_val_str = safe_val_str[:32000] + "... [TRUNCATED]"
            
        safe_val = saxutils.escape(safe_val_str).replace('\n', '<br/>')
        
        elements.append(Paragraph(safe_name, field_name_style))
        elements.append(Paragraph(safe_val, normal_style))
        elements.append(Spacer(1, 12))

    elements.append(Spacer(1, 20))

    # Footer
    footer_style = ParagraphStyle(
        "Footer",
        parent=styles["Normal"],
        fontSize=7,
        textColor=colors.HexColor("#999999"),
    )
    elements.append(Paragraph("Generated by Puff n Parse — From B 2 C", footer_style))

    doc.build(elements)
    return output.getvalue()


def generate_export(fields: list[ExtractedField], format: str, filename: str = "export") -> tuple[bytes, str, str]:
    """
    Generate an export file in the requested format.

    Returns: (file_bytes, content_type, file_extension)
    """
    format_map = {
        "csv": (export_to_csv, "text/csv", ".csv"),
        "xlsx": (export_to_xlsx, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", ".xlsx"),
        "docx": (export_to_docx, "application/vnd.openxmlformats-officedocument.wordprocessingml.document", ".docx"),
        "pdf": (export_to_pdf, "application/pdf", ".pdf"),
    }

    if format not in format_map:
        raise ValueError(f"Unsupported export format: {format}")

    export_fn, content_type, extension = format_map[format]
    file_bytes = export_fn(fields, filename)

    return file_bytes, content_type, extension