from flask import Blueprint, request, jsonify
from server.database import Session
from models.models import SchoolHoliday
from datetime import datetime
import csv
import io

holidays_bp = Blueprint("holidays", __name__, url_prefix="/api/holidays")


@holidays_bp.route("", methods=["GET"])
def list_holidays():
    session = Session()
    region = request.args.get("region")
    q = session.query(SchoolHoliday)
    if region:
        q = q.filter(SchoolHoliday.region == region)
    rows = q.order_by(SchoolHoliday.start_date.asc()).all()
    data = [r.to_dict() for r in rows]
    session.close()
    return jsonify({"holidays": data})


@holidays_bp.route("/upload", methods=["POST"])
def upload_holidays():
    """
    Accepts a CSV file upload (multipart/form-data) with columns like:
    name,start_date,end_date,region
    Dates can be in ISO (YYYY-MM-DD) or common European format (DD.MM.YYYY).
    """
    if "file" not in request.files:
        return jsonify({"error": "No file part"}), 400
    file = request.files["file"]
    if file.filename == "":
        return jsonify({"error": "No selected file"}), 400

    try:
        content = file.read().decode("utf-8", errors="ignore")
        # Try to auto-detect delimiter; default ','
        sniffer = csv.Sniffer()
        dialect = None
        try:
            dialect = sniffer.sniff(content[:1024])
        except Exception:
            pass
        reader = csv.DictReader(io.StringIO(
            content), dialect=dialect) if dialect else csv.DictReader(io.StringIO(content))

        required = {"name", "start_date", "end_date"}
        if not required.issubset(set(h.lower() for h in reader.fieldnames or [])):
            return jsonify({"error": "CSV must contain headers: name, start_date, end_date"}), 400

        def parse_date(s: str):
            s = (s or "").strip()
            if not s:
                return None
            # Try ISO first
            for fmt in ("%Y-%m-%d", "%d.%m.%Y", "%Y/%m/%d"):
                try:
                    return datetime.strptime(s, fmt).date()
                except ValueError:
                    continue
            raise ValueError(f"Unsupported date format: {s}")

        session = Session()
        inserted = 0
        updated = 0
        for row in reader:
            # Normalize headers to lower-case keys
            norm = {k.lower(): (v or "").strip() for k, v in row.items()}
            name = norm.get("name")
            start_date = parse_date(norm.get("start_date"))
            end_date = parse_date(norm.get("end_date"))
            region = norm.get("region") or None
            if not name or not start_date or not end_date:
                continue

            existing = (
                session.query(SchoolHoliday)
                .filter(
                    SchoolHoliday.name == name,
                    SchoolHoliday.start_date == start_date,
                    SchoolHoliday.end_date == end_date,
                    SchoolHoliday.region.is_(
                        region) if region is None else SchoolHoliday.region == region,
                )
                .first()
            )

            if existing:
                # Optionally update region or source_file_name
                existing.region = region
                existing.source_file_name = file.filename
                updated += 1
            else:
                session.add(SchoolHoliday(
                    name=name,
                    start_date=start_date,
                    end_date=end_date,
                    region=region,
                    source_file_name=file.filename,
                ))
                inserted += 1

        session.commit()
        session.close()
        return jsonify({"success": True, "inserted": inserted, "updated": updated})
    except Exception as e:
        return jsonify({"error": str(e)}), 400