from datetime import datetime
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel, Field
from sqlalchemy.orm import Session

from app.database.database import get_db
from app.database.models import Goal, User

router = APIRouter(prefix="/api/goals", tags=["Goals"])


def _resolve_user(db: Session, user_id: Optional[str]) -> str:
    if user_id:
        return user_id
    user = db.query(User).first()
    if not user:
        raise HTTPException(status_code=404, detail="No users found. Seed the database first.")
    return user.id


class ContributeRequest(BaseModel):
    amount: float = Field(gt=0)


@router.get("")
def list_goals(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = _resolve_user(db, user_id)
    goals = db.query(Goal).filter(Goal.user_id == uid).order_by(Goal.target_date.asc()).all()
    items = []
    total_target = 0.0
    total_saved = 0.0
    for g in goals:
        progress = min(100.0, (g.current_amount / g.target_amount * 100) if g.target_amount > 0 else 0)
        total_target += g.target_amount
        total_saved += g.current_amount
        days_left = None
        if g.target_date:
            days_left = max(0, (g.target_date.replace(tzinfo=None) - datetime.utcnow()).days)
        plan = g.ai_generated_plan or {}
        items.append({
            "id": g.id,
            "title": g.title,
            "target_amount": g.target_amount,
            "current_amount": g.current_amount,
            "progress_percent": round(progress, 1),
            "target_date": g.target_date.isoformat() if g.target_date else None,
            "days_left": days_left,
            "monthly_contribution": plan.get("monthly_contribution"),
            "months_remaining": plan.get("months_remaining"),
            "on_track": progress >= 50 or (days_left is not None and days_left > 180),
        })
    return {
        "goals": items,
        "summary": {
            "count": len(items),
            "total_target": round(total_target, 2),
            "total_saved": round(total_saved, 2),
            "overall_progress": round(total_saved / total_target * 100, 1) if total_target > 0 else 0,
        },
    }


@router.post("/{goal_id}/contribute")
def contribute_to_goal(
    goal_id: str,
    body: ContributeRequest,
    user_id: Optional[str] = None,
    db: Session = Depends(get_db),
):
    uid = _resolve_user(db, user_id)
    goal = db.query(Goal).filter(Goal.id == goal_id, Goal.user_id == uid).first()
    if not goal:
        raise HTTPException(status_code=404, detail="Goal not found")
    goal.current_amount = min(goal.target_amount, goal.current_amount + body.amount)
    db.commit()
    db.refresh(goal)
    progress = min(100.0, goal.current_amount / goal.target_amount * 100) if goal.target_amount > 0 else 0
    return {
        "id": goal.id,
        "current_amount": goal.current_amount,
        "progress_percent": round(progress, 1),
        "completed": goal.current_amount >= goal.target_amount,
    }