import copy
import json
import os
from datetime import date
from storage import load_json, save_json

DATA_DIR = os.environ.get("DATA_DIR", os.path.join(os.path.dirname(__file__), "data"))
SINKING_FILE = os.path.join(DATA_DIR, "sinking_funds.json")

FUND_COLORS = {
    "Travel":              "#C5BBA0",
    "Vet & Pets":          "#A0B8C5",
    "Holidays & Gifts":    "#D4B8C5",
    "Renovations":         "#C5A8A0",
    "Studio Build":        "#B4A0C5",
    "Emergency Fund":      "#A8C5A0",
}

DEFAULT_FUNDS = [
    {"name": "Travel",           "type": "ongoing", "monthly": 0, "balance": 0, "notes": ""},
    {"name": "Vet & Pets",       "type": "ongoing", "monthly": 0, "balance": 0, "notes": ""},
    {"name": "Holidays & Gifts", "type": "ongoing", "monthly": 0, "balance": 0, "notes": ""},
    {"name": "Renovations",      "type": "ongoing", "monthly": 0, "balance": 0, "notes": "Subcategories coming later"},
    {"name": "Studio Build",     "type": "ongoing", "monthly": 0, "balance": 0, "notes": "Goal amount TBD"},
    {"name": "Emergency Fund",   "type": "ongoing", "monthly": 0, "balance": 0, "notes": "Target: 3–6 months expenses"},
]


def load_funds():
    funds = load_json(SINKING_FILE, None)
    if funds is None:
        # First run — seed with a copy of the defaults (never hand out the
        # module-level list, which callers mutate in place).
        funds = copy.deepcopy(DEFAULT_FUNDS)
        save_funds(funds)
    return funds


def save_funds(funds):
    save_json(SINKING_FILE, funds)


def months_until(target_date_str):
    try:
        target = date.fromisoformat(target_date_str)
        today = date.today()
        months = (target.year - today.year) * 12 + (target.month - today.month)
        return max(months, 1)
    except Exception:
        return None


def monthly_needed(balance, goal, target_date_str):
    m = months_until(target_date_str)
    if not m:
        return None
    remaining = max(goal - balance, 0)
    return round(remaining / m, 2)