from __future__ import annotations
"""API routes for Fristen-Tracking (Issue #17)."""

from datetime import date, datetime
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel

from tracker.db.session import get_connection

router = APIRouter(prefix="/fristen", tags=["fristen"])


def _db():
    conn = get_connection()
    try:
        yield conn
    finally:
        conn.close()


class FristCreate(BaseModel):
    kette_id: int
    vorlage_id: Optional[int] = None
    typ: str  # überarbeitung, bericht, prüfung, umsetzung, sonstiges
    datum: str  # YYYY-MM-DD
    beschreibung: Optional[str] = None


class FristUpdate(BaseModel):
    status: Optional[str] = None
    datum: Optional[str] = None
    beschreibung: Optional[str] = None


@router.get("")
def list_fristen(
    kette_id: Optional[int] = None,
    status: Optional[str] = Query(None, description="offen, überfällig, erfüllt, alle"),
    typ: Optional[str] = None,
    page: int = 1,
    page_size: int = 50,
    conn=Depends(_db),
):
    """Fristen auflisten mit Joins auf ketten + vorlagen."""
    where_clauses = []
    params: list = []

    if kette_id is not None:
        where_clauses.append("f.kette_id = ?")
        params.append(kette_id)

    if status and status != "alle":
        if status == "überfällig":
            where_clauses.append("(f.status = 'überfällig' OR (f.status = 'offen' AND f.datum < date('now')))")
        else:
            where_clauses.append("f.status = ?")
            params.append(status)

    if typ:
        where_clauses.append("f.typ = ?")
        params.append(typ)

    where_sql = (" WHERE " + " AND ".join(where_clauses)) if where_clauses else ""

    # Count
    total = conn.execute(f"SELECT COUNT(*) as cnt FROM fristen f{where_sql}", params).fetchone()["cnt"]

    # Query with joins
    offset = (page - 1) * page_size
    rows = conn.execute(
        f"""SELECT f.*,
                   k.status AS kette_status,
                   v_ursprung.aktenzeichen AS kette_aktenzeichen,
                   v_ursprung.betreff AS kette_betreff,
                   v_frist.aktenzeichen AS vorlage_aktenzeichen
            FROM fristen f
            LEFT JOIN ketten k ON f.kette_id = k.id
            LEFT JOIN vorlagen v_ursprung ON k.ursprung_id = v_ursprung.id
            LEFT JOIN vorlagen v_frist ON f.vorlage_id = v_frist.id
            {where_sql}
            ORDER BY
                CASE WHEN f.status = 'überfällig' OR (f.status = 'offen' AND f.datum < date('now')) THEN 0
                     WHEN f.status = 'offen' THEN 1
                     ELSE 2 END,
                f.datum ASC
            LIMIT ? OFFSET ?""",
        params + [page_size, offset],
    ).fetchall()

    items = []
    for r in rows:
        item = dict(r)
        # Mark overdue in response
        if item["status"] == "offen" and item["datum"] and item["datum"] < date.today().isoformat():
            item["status"] = "überfällig"
        items.append(item)

    return {"items": items, "total": total, "page": page, "page_size": page_size}


@router.post("")
def create_frist(body: FristCreate, conn=Depends(_db)):
    """Neue Frist manuell anlegen."""
    # Validate kette exists
    kette = conn.execute("SELECT id FROM ketten WHERE id = ?", (body.kette_id,)).fetchone()
    if not kette:
        raise HTTPException(status_code=404, detail="Kette nicht gefunden")

    if body.vorlage_id:
        vorlage = conn.execute("SELECT id FROM vorlagen WHERE id = ?", (body.vorlage_id,)).fetchone()
        if not vorlage:
            raise HTTPException(status_code=404, detail="Vorlage nicht gefunden")

    cursor = conn.execute(
        """INSERT INTO fristen (kette_id, vorlage_id, typ, datum, beschreibung, quelle, status, erstellt_at)
           VALUES (?, ?, ?, ?, ?, 'manuell', 'offen', ?)""",
        (body.kette_id, body.vorlage_id, body.typ, body.datum, body.beschreibung, datetime.now().isoformat()),
    )
    conn.commit()
    frist_id = cursor.lastrowid

    row = conn.execute("SELECT * FROM fristen WHERE id = ?", (frist_id,)).fetchone()
    return dict(row)


@router.patch("/{frist_id}")
def update_frist(frist_id: int, body: FristUpdate, conn=Depends(_db)):
    """Frist aktualisieren (Status, Datum, Beschreibung)."""
    existing = conn.execute("SELECT * FROM fristen WHERE id = ?", (frist_id,)).fetchone()
    if not existing:
        raise HTTPException(status_code=404, detail="Frist nicht gefunden")

    updates = []
    params = []

    if body.status is not None:
        updates.append("status = ?")
        params.append(body.status)
    if body.datum is not None:
        updates.append("datum = ?")
        params.append(body.datum)
    if body.beschreibung is not None:
        updates.append("beschreibung = ?")
        params.append(body.beschreibung)

    if not updates:
        raise HTTPException(status_code=400, detail="Keine Änderungen angegeben")

    updates.append("aktualisiert_at = ?")
    params.append(datetime.now().isoformat())
    params.append(frist_id)

    conn.execute(f"UPDATE fristen SET {', '.join(updates)} WHERE id = ?", params)
    conn.commit()

    row = conn.execute("SELECT * FROM fristen WHERE id = ?", (frist_id,)).fetchone()
    return dict(row)


@router.delete("/{frist_id}")
def delete_frist(frist_id: int, conn=Depends(_db)):
    """Frist löschen."""
    existing = conn.execute("SELECT * FROM fristen WHERE id = ?", (frist_id,)).fetchone()
    if not existing:
        raise HTTPException(status_code=404, detail="Frist nicht gefunden")

    conn.execute("DELETE FROM fristen WHERE id = ?", (frist_id,))
    conn.commit()
    return {"ok": True, "deleted": frist_id}


@router.get("/ueberfaellig")
def get_ueberfaellige(conn=Depends(_db)):
    """Überfällige Fristen abrufen und automatisch Status setzen."""
    today = date.today().isoformat()

    # Update status for overdue fristen
    conn.execute(
        "UPDATE fristen SET status = 'überfällig', aktualisiert_at = ? WHERE status = 'offen' AND datum < ?",
        (datetime.now().isoformat(), today),
    )
    conn.commit()

    rows = conn.execute(
        """SELECT f.*,
                  k.status AS kette_status,
                  v_ursprung.aktenzeichen AS kette_aktenzeichen,
                  v_ursprung.betreff AS kette_betreff
           FROM fristen f
           LEFT JOIN ketten k ON f.kette_id = k.id
           LEFT JOIN vorlagen v_ursprung ON k.ursprung_id = v_ursprung.id
           WHERE f.status = 'überfällig'
           ORDER BY f.datum ASC""",
    ).fetchall()

    return {"items": [dict(r) for r in rows], "total": len(rows)}