"""Background job for isolated report generation.

This job runs in the ARQ worker process, NOT in the API process.
This isolates PDF/HTML rendering from the API:
- No shell access in worker
- No Docker socket
- No unnecessary secrets
- CPU/RAM limited by worker process
- Only approved templates
- URL fetching disabled (safe_url_fetcher)

The job:
1. Fetches the template from DB
2. Renders the template (SandboxedEnvironment)
3. Generates PDF/CSV/Excel/JSON
4. Stores the result in DMS
5. Returns the DMS file ID
"""

from __future__ import annotations

import io
import logging
import uuid
from typing import Any

from sqlalchemy import select

from app.core.db import create_db_session
from app.core.job_registry import register_job
from app.core.storage import get_storage_backend
from app.plugins.builtins.report_generator.models import ReportTemplate
from app.plugins.builtins.report_generator.pdf_generator import (
    generate_pdf_from_template_content,
    render_template_string,
)

logger = logging.getLogger(__name__)


def _generate_csv(rendered: str) -> io.BytesIO:
    import csv
    buf = io.BytesIO()
    writer = csv.writer(io.TextIOWrapper(buf, encoding="utf-8", newline=""))
    for line in rendered.strip().split("\n"):
        writer.writerow(line.split(","))
    buf.seek(0)
    return buf


def _generate_excel(rendered: str) -> io.BytesIO:
    import openpyxl
    wb = openpyxl.Workbook()
    ws = wb.active
    for i, line in enumerate(rendered.strip().split("\n"), 1):
        for j, cell in enumerate(line.split(","), 1):
            ws.cell(row=i, column=j, value=cell)
    buf = io.BytesIO()
    wb.save(buf)
    buf.seek(0)
    return buf


async def generate_report_job(
    ctx: dict[str, Any],
    tenant_id: str,
    user_id: str,
    template_id: str,
    data: dict[str, Any],
    output_format: str | None = None,
) -> dict[str, Any]:
    """Background job: Generate a report and store in DMS.

    Returns:
        {"dms_file_id": ..., "filename": ..., "format": ..., "size": ...}
    """
    import hashlib

    from app.plugins.builtins.contracts import get_contract_registry
    _dms_contract = get_contract_registry().get("dms")
    dms_file = _dms_contract.dms_file

    async with create_db_session() as db:
        # 1. Fetch template
        result = await db.execute(
            select(ReportTemplate).where(
                ReportTemplate.id == uuid.UUID(template_id),
                ReportTemplate.tenant_id == uuid.UUID(tenant_id),
                ReportTemplate.deleted_at.is_(None),
            )
        )
        template = result.scalar_one_or_none()
        if template is None:
            raise ValueError(f"Template {template_id} not found")

        fmt = output_format or template.output_format

        # 2. Generate content
        if fmt in ("pdf", "print"):
            raw_bytes, ext = generate_pdf_from_template_content(
                template.content, data, fmt,
            )
        elif fmt == "csv":
            rendered = render_template_string(template.content, data)
            file_data = _generate_csv(rendered)
            raw_bytes = file_data.getvalue()
            ext = "csv"
        elif fmt == "excel":
            rendered = render_template_string(template.content, data)
            file_data = _generate_excel(rendered)
            raw_bytes = file_data.getvalue()
            ext = "xlsx"
        elif fmt == "json":
            rendered = render_template_string(template.content, data)
            import json
            raw_bytes = json.dumps(rendered, indent=2).encode()
            ext = "json"
        else:
            raise ValueError(f"Unsupported format: {fmt}")

        # 3. Store in DMS
        content_hash = hashlib.sha256(raw_bytes).hexdigest()
        storage_path = f"reports/{tenant_id}/{uuid.uuid4().hex}.{ext}"
        storage = get_storage_backend()
        await storage.save(storage_path, raw_bytes)

        dms_file = dms_file(
            tenant_id=uuid.UUID(tenant_id),
            name=f"{template.name}.{ext}",
            folder_id=None,
            uploaded_by=uuid.UUID(user_id),
            mime_type="application/pdf" if fmt in ("pdf", "print") else f"text/{ext}",
            size_bytes=len(raw_bytes),
            storage_path=storage_path,
            content_hash=content_hash,
            owner_id=uuid.UUID(user_id),
        )
        db.add(dms_file)
        await db.flush()
        await db.commit()
        await db.refresh(dms_file)

        return {
            "dms_file_id": str(dms_file.id),
            "filename": dms_file.name,
            "format": fmt,
            "size": len(raw_bytes),
        }


# Register with the job registry
register_job("generate_report", generate_report_job)