"""Company service — CRUD, FTS search, filter, pagination, soft-delete, N:M, export."""

from __future__ import annotations

import csv
import io
import uuid
from datetime import datetime, timezone
from typing import Any

from sqlalchemy import select, func, or_, desc, asc, delete
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.audit import log_audit, log_deletion
from app.models.company import Company
from app.models.contact import Contact, CompanyContact


def _company_to_dict(c: Company, include_contacts: bool = False) -> dict[str, Any]:
    """Serialize a Company ORM object to dict."""
    data: dict[str, Any] = {
        "id": str(c.id),
        "name": c.name,
        "account_number": c.account_number,
        "industry": c.industry,
        "phone": c.phone,
        "email": c.email,
        "website": c.website,
        "description": c.description,
        "created_at": c.created_at.isoformat() if c.created_at else None,
        "updated_at": c.updated_at.isoformat() if c.updated_at else None,
    }
    if include_contacts:
        data["contacts"] = []  # populated by caller if needed
    return data


async def list_companies(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    page: int = 1,
    page_size: int = 20,
    search: str | None = None,
    industry: str | None = None,
    sort_by: str = "name",
    sort_order: str = "asc",
) -> dict[str, Any]:
    """List companies with pagination, FTS search, industry filter, and sorting.

    Returns {items, total, page, page_size}.
    """
    page = max(1, page)
    page_size = max(1, min(100, page_size))

    base = select(Company).where(
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )

    # Industry filter
    if industry:
        base = base.where(Company.industry == industry)

    # FTS search using PostgreSQL tsvector @@ plainto_tsquery, with ILIKE fallback
    if search:
        pattern = f"%{search}%"
        base = base.where(
            or_(
                Company.search_tsv.op("@@")(
                    func.plainto_tsquery("english", search)
                ),
                Company.name.ilike(pattern),
                Company.industry.ilike(pattern),
                Company.description.ilike(pattern),
            )
        )

    # Sorting
    sort_col = getattr(Company, sort_by, Company.name)
    if sort_order == "desc":
        base = base.order_by(desc(sort_col))
    else:
        base = base.order_by(asc(sort_col))

    # Count total (without pagination)
    count_q = select(func.count()).select_from(base.subquery())
    total_result = await db.execute(count_q)
    total = total_result.scalar_one()

    # Paginate
    offset = (page - 1) * page_size
    paginated = base.offset(offset).limit(page_size)
    result = await db.execute(paginated)
    companies = result.scalars().all()

    return {
        "items": [_company_to_dict(c) for c in companies],
        "total": total,
        "page": page,
        "page_size": page_size,
    }


async def get_company_detail(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    company_id: uuid.UUID,
) -> dict[str, Any] | None:
    """Get a single company with its contacts array."""
    q = select(Company).where(
        Company.id == company_id,
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    result = await db.execute(q)
    company = result.scalar_one_or_none()
    if company is None:
        return None

    data = _company_to_dict(company, include_contacts=True)
    # Fetch linked contacts
    contacts_q = (
        select(Contact, CompanyContact)
        .join(CompanyContact, CompanyContact.contact_id == Contact.id)
        .where(
            CompanyContact.company_id == company_id,
            CompanyContact.tenant_id == tenant_id,
            Contact.deleted_at.is_(None),
        )
    )
    contacts_result = await db.execute(contacts_q)
    contacts_list = []
    for contact, link in contacts_result.all():
        contacts_list.append({
            "id": str(contact.id),
            "first_name": contact.first_name,
            "last_name": contact.last_name,
            "email": contact.email,
            "phone": contact.phone,
            "position": contact.position,
            "role_at_company": link.role_at_company,
            "is_primary": link.is_primary,
        })
    data["contacts"] = contacts_list
    return data


async def create_company(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    data: dict[str, Any],
) -> dict[str, Any]:
    """Create a new company and audit-log it."""
    company = Company(
        tenant_id=tenant_id,
        name=data["name"],
        account_number=data.get("account_number"),
        industry=data.get("industry"),
        phone=data.get("phone"),
        email=data.get("email"),
        website=data.get("website"),
        description=data.get("description"),
        created_by=user_id,
        updated_by=user_id,
    )
    db.add(company)
    await db.flush()
    await db.refresh(company)
    await log_audit(
        db, tenant_id, user_id, "create", "company", company.id,
        changes={"name": data["name"]},
    )
    return _company_to_dict(company)


async def update_company(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    company_id: uuid.UUID,
    data: dict[str, Any],
) -> dict[str, Any] | None:
    """Update a company (partial update) and audit-log changes."""
    q = select(Company).where(
        Company.id == company_id,
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    result = await db.execute(q)
    company = result.scalar_one_or_none()
    if company is None:
        return None

    changes: dict[str, Any] = {}
    for field in ("name", "account_number", "industry", "phone", "email", "website", "description"):
        if field in data and data[field] is not None:
            old_val = getattr(company, field)
            changes[field] = {"old": old_val, "new": data[field]}
            setattr(company, field, data[field])
    company.updated_by = user_id

    await db.flush()
    await db.refresh(company)
    await log_audit(db, tenant_id, user_id, "update", "company", company_id, changes=changes)
    return _company_to_dict(company)


async def soft_delete_company(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    company_id: uuid.UUID,
    cascade: bool = False,
) -> bool:
    """Soft-delete a company. If cascade=True, also soft-delete linked CompanyContact rows."""
    q = select(Company).where(
        Company.id == company_id,
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    result = await db.execute(q)
    company = result.scalar_one_or_none()
    if company is None:
        return False

    company.deleted_at = datetime.now(timezone.utc)
    company.updated_by = user_id

    if cascade:
        # Delete N:M links for this company
        await db.execute(
            delete(CompanyContact).where(
                CompanyContact.company_id == company_id,
                CompanyContact.tenant_id == tenant_id,
            )
        )

    await db.flush()
    await log_audit(
        db, tenant_id, user_id, "delete", "company", company_id,
        changes={"name": company.name, "cascade": cascade},
    )
    return True


async def link_contact(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    company_id: uuid.UUID,
    contact_id: uuid.UUID,
    role_at_company: str | None = None,
    is_primary: bool = False,
) -> dict[str, Any] | None:
    """Link a contact to a company (N:M). Returns link data or None if either not found."""
    # Verify company exists and is in tenant
    comp_q = select(Company).where(
        Company.id == company_id,
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    comp_result = await db.execute(comp_q)
    if comp_result.scalar_one_or_none() is None:
        return None

    # Verify contact exists and is in tenant
    cont_q = select(Contact).where(
        Contact.id == contact_id,
        Contact.tenant_id == tenant_id,
        Contact.deleted_at.is_(None),
    )
    cont_result = await db.execute(cont_q)
    if cont_result.scalar_one_or_none() is None:
        return None

    # Check if link already exists
    existing_q = select(CompanyContact).where(
        CompanyContact.company_id == company_id,
        CompanyContact.contact_id == contact_id,
        CompanyContact.tenant_id == tenant_id,
    )
    existing_result = await db.execute(existing_q)
    existing = existing_result.scalar_one_or_none()
    if existing is not None:
        # Update existing link
        existing.role_at_company = role_at_company
        existing.is_primary = is_primary
        await db.flush()
        await log_audit(
            db, tenant_id, user_id, "link", "company_contact", existing.id,
            changes={"company_id": str(company_id), "contact_id": str(contact_id)},
        )
        return {
            "id": str(existing.id),
            "company_id": str(company_id),
            "contact_id": str(contact_id),
            "role_at_company": role_at_company,
            "is_primary": is_primary,
        }

    link = CompanyContact(
        tenant_id=tenant_id,
        company_id=company_id,
        contact_id=contact_id,
        role_at_company=role_at_company,
        is_primary=is_primary,
    )
    db.add(link)
    await db.flush()
    await log_audit(
        db, tenant_id, user_id, "link", "company_contact", link.id,
        changes={"company_id": str(company_id), "contact_id": str(contact_id)},
    )
    return {
        "id": str(link.id),
        "company_id": str(company_id),
        "contact_id": str(contact_id),
        "role_at_company": role_at_company,
        "is_primary": is_primary,
    }


async def unlink_contact(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    company_id: uuid.UUID,
    contact_id: uuid.UUID,
) -> bool:
    """Unlink a contact from a company (N:M)."""
    q = select(CompanyContact).where(
        CompanyContact.company_id == company_id,
        CompanyContact.contact_id == contact_id,
        CompanyContact.tenant_id == tenant_id,
    )
    result = await db.execute(q)
    link = result.scalar_one_or_none()
    if link is None:
        return False

    await db.delete(link)
    await db.flush()
    await log_audit(
        db, tenant_id, user_id, "unlink", "company_contact", link.id,
        changes={"company_id": str(company_id), "contact_id": str(contact_id)},
    )
    return True


async def export_companies_csv(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    industry: str | None = None,
    search: str | None = None,
) -> str:
    """Export companies as CSV string."""
    base = select(Company).where(
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    if industry:
        base = base.where(Company.industry == industry)
    if search:
        pattern = f"%{search}%"
        base = base.where(
            or_(
                Company.search_tsv.op("@@")(
                    func.plainto_tsquery("english", search)
                ),
                Company.name.ilike(pattern),
                Company.industry.ilike(pattern),
                Company.description.ilike(pattern),
            )
        )
    base = base.order_by(Company.name)
    result = await db.execute(base)
    companies = result.scalars().all()

    output = io.StringIO()
    writer = csv.writer(output)
    writer.writerow(["id", "name", "account_number", "industry", "phone", "email", "website", "description"])
    for c in companies:
        writer.writerow([
            str(c.id), c.name, c.account_number or "", c.industry or "",
            c.phone or "", c.email or "", c.website or "", c.description or "",
        ])
    return output.getvalue()


async def export_companies_xlsx(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    industry: str | None = None,
    search: str | None = None,
) -> bytes:
    """Export companies as XLSX bytes."""
    from openpyxl import Workbook

    base = select(Company).where(
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    if industry:
        base = base.where(Company.industry == industry)
    if search:
        pattern = f"%{search}%"
        base = base.where(
            or_(
                Company.search_tsv.op("@@")(
                    func.plainto_tsquery("english", search)
                ),
                Company.name.ilike(pattern),
                Company.industry.ilike(pattern),
                Company.description.ilike(pattern),
            )
        )
    base = base.order_by(Company.name)
    result = await db.execute(base)
    companies = result.scalars().all()

    wb = Workbook()
    ws = wb.active
    ws.title = "Companies"
    headers = ["id", "name", "account_number", "industry", "phone", "email", "website", "description"]
    ws.append(headers)
    for c in companies:
        ws.append([
            str(c.id), c.name, c.account_number or "", c.industry or "",
            c.phone or "", c.email or "", c.website or "", c.description or "",
        ])

    buf = io.BytesIO()
    wb.save(buf)
    return buf.getvalue()


async def get_company_emails(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    company_id: uuid.UUID,
) -> list[dict[str, Any]]:
    """Get emails for a company (mail plugin inactive — returns empty array)."""
    # Verify company exists
    q = select(Company).where(
        Company.id == company_id,
        Company.tenant_id == tenant_id,
        Company.deleted_at.is_(None),
    )
    result = await db.execute(q)
    if result.scalar_one_or_none() is None:
        return []  # Caller should check existence separately
    return []