import os
from datetime import date, timedelta
from plaid.api import plaid_api
from plaid.configuration import Configuration
from plaid.api_client import ApiClient
from plaid.model.products import Products
from plaid.model.country_code import CountryCode
from plaid.exceptions import ApiException
from plaid.model.accounts_balance_get_request import AccountsBalanceGetRequest
from plaid.model.transactions_get_request import TransactionsGetRequest
from plaid.model.transactions_get_request_options import TransactionsGetRequestOptions
from plaid.model.link_token_create_request import LinkTokenCreateRequest
from plaid.model.link_token_create_request_user import LinkTokenCreateRequestUser
from plaid.model.item_public_token_exchange_request import ItemPublicTokenExchangeRequest

# ---------- Client setup ----------

def _make_client():
    env = os.environ.get("PLAID_ENV", "sandbox")
    host = {
        "sandbox":     "https://sandbox.plaid.com",
        "development": "https://development.plaid.com",
        "production":  "https://production.plaid.com",
    }[env]

    config = Configuration(
        host=host,
        api_key={
        "clientId": os.environ["PLAID_CLIENT_ID"],   # reads from .env
        "secret":   os.environ["PLAID_SECRET"]
        }
    )
    return plaid_api.PlaidApi(ApiClient(config))

plaid_client = _make_client()


# ---------- Balances ----------

def get_balances(access_token: str) -> str:
    request = AccountsBalanceGetRequest(access_token=access_token)
    response = plaid_client.accounts_balance_get(request)

    lines = ["USER'S CURRENT ACCOUNT BALANCES:"]
    for account in response['accounts']:
        name    = account['name']
        subtype = str(account['subtype'])
        current = account['balances']['current']

        if current is None:
            continue

        # Skip mortgage and line of credit — not relevant for daily budgeting
        if subtype in ['mortgage', 'line of credit']:
            continue

        if subtype == 'credit card':
            limit     = account['balances']['limit'] or 0
            owing     = current
            available = limit - current if limit > 0 else 0
            lines.append(
                f"- {name} (Credit Card): "
                f"${owing:.2f} owing, ${available:.2f} available out of ${limit:.2f} limit"
            )
        elif subtype == 'checking':
            available = account['balances']['available'] or current
            lines.append(f"- {name} (Chequing): ${current:.2f} balance, ${available:.2f} available")
        elif subtype == 'savings':
            lines.append(f"- {name} (Savings): ${current:.2f}")
        elif subtype == 'rrsp':
            lines.append(f"- {name} (RRSP): ${current:.2f}")
        else:
            lines.append(f"- {name} ({subtype}): ${current:.2f}")

    return "\n".join(lines)
    request = AccountsBalanceGetRequest(access_token=access_token)
    response = plaid_client.accounts_balance_get(request)

    lines = ["USER'S CURRENT ACCOUNT BALANCES:"]
    for account in response['accounts']:
        name    = account['name']
        subtype = account['subtype']
        current = account['balances']['current']

        if current is None:
            continue

        if subtype == 'credit card':
            limit     = account['balances']['limit'] or 0
            available = account['balances']['available'] or (limit - current)
            lines.append(
                f"- {name} (Credit Card): "
                f"${current:.2f} owing, ${available:.2f} available"
            )
        elif subtype in ['mortgage', 'line of credit']:
            lines.append(f"- {name} ({subtype}): ${current:.2f} outstanding")
        else:
            lines.append(f"- {name} ({subtype}): ${current:.2f}")

    return "\n".join(lines)

# ---------- Transactions ----------

def get_transactions(access_token: str, days: int = 30) -> str:
    end_date = date.today()
    start_date = end_date - timedelta(days=days)
    week_start = end_date - timedelta(days=end_date.weekday())

    request = TransactionsGetRequest(
        access_token=access_token,
        start_date=start_date,
        end_date=end_date,
        options=TransactionsGetRequestOptions(
            count=200,
            include_personal_finance_category=True
        )
    )
    response = plaid_client.transactions_get(request)
    transactions = response['transactions']

    if not transactions:
        return "No transactions found in the last 30 days."

    today_total = 0.0
    week_total = 0.0
    month_total = 0.0
    income_total = 0.0
    category_totals: dict[str, float] = {}

    for txn in transactions:
        amount = txn['amount']
        name = txn['name']
        txn_date = txn['date']
        category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

        # Skip internal transfers between own accounts
        if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
            continue

        # Detect payroll mislabeled as loan payments
        name_lower = name.lower()
        if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
            income_total += amount
            continue

        # Skip other loan payments (mortgage, LOC) — not daily spending
        if category == 'LOAN_PAYMENTS':
            continue

        # Income (negative = money in)
        if amount < 0:
            income_total += abs(amount)
            continue

        # Spending
        month_total += amount
        readable = category.replace("_", " ").title()
        category_totals[readable] = category_totals.get(readable, 0) + amount

        if txn_date >= week_start:
            week_total += amount

        if txn_date == end_date:
            today_total += amount

    lines = ["FINANCIAL SUMMARY (pre-calculated, do NOT recalculate):"]
    lines.append(f"Today's spending: ${today_total:.2f}")
    lines.append(f"This week's spending (since {week_start}): ${week_total:.2f}")
    lines.append(f"This month's spending (last {days} days): ${month_total:.2f}")

    if income_total > 0:
        lines.append(f"Income received (last {days} days): +${income_total:.2f}")

    lines.append(f"Average daily spending: ${month_total / max(days, 1):.2f}")

    lines.append("\nSPENDING BY CATEGORY:")
    for category, total in sorted(category_totals.items(), key=lambda x: -x[1]):
        pct = (total / month_total * 100) if month_total > 0 else 0
        lines.append(f"- {category}: ${total:.2f} ({pct:.0f}%)")

    lines.append("\nRECENT TRANSACTIONS (last 5):")
    count = 0
    for txn in transactions:
        if count >= 5:
            break
        amount = txn['amount']
        category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')
        if amount <= 0 or category in ['TRANSFER_IN', 'TRANSFER_OUT', 'LOAN_PAYMENTS']:
            continue
        lines.append(f"  - {txn['date']} {txn['name']}: ${amount:.2f}")
        count += 1

    return "\n".join(lines)
    end_date = date.today()
    start_date = end_date - timedelta(days=days)
    week_start = end_date - timedelta(days=end_date.weekday())

    request = TransactionsGetRequest(
        access_token=access_token,
        start_date=start_date,
        end_date=end_date,
        options=TransactionsGetRequestOptions(
            count=100,
            include_personal_finance_category=True
        )
    )
    response = plaid_client.transactions_get(request)
    transactions = response['transactions']

    if not transactions:
        return "No transactions found in the last 30 days."

    # Pre-calculate everything — never let LLM do math
    today_total = 0.0
    week_total = 0.0
    month_total = 0.0
    income_total = 0.0
    category_totals: dict[str, float] = {}
    today_transactions: list[str] = []
    week_transactions: list[str] = []

    for txn in transactions:
        amount = txn['amount']
        name = txn['name']
        txn_date = txn['date']
        category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

        # Income (negative = money in)
        if amount < 0:
            income_total += abs(amount)
            continue

        # Skip internal transfers
        if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
            continue

        name_lower = name.lower()
        if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
            income_total += amount
            continue

        # Spending totals by time period
        month_total += amount
        category_totals[category] = category_totals.get(category, 0) + amount

        if txn_date >= week_start:
            week_total += amount
            week_transactions.append(f"  - {txn_date} {name}: ${amount:.2f}")

        if txn_date == end_date:
            today_total += amount
            today_transactions.append(f"  - {name}: ${amount:.2f}")

    # Build compact summary — no raw transaction dumps
    lines = ["FINANCIAL SUMMARY (pre-calculated, do NOT recalculate):"]
    lines.append(f"Today's spending: ${today_total:.2f}")
    lines.append(f"This week's spending (since {week_start}): ${week_total:.2f}")
    lines.append(f"This month's spending (last {days} days): ${month_total:.2f}")
    
    if income_total > 0:
        lines.append(f"Income received (last {days} days): +${income_total:.2f}")

    lines.append(f"Average daily spending: ${month_total / max(days, 1):.2f}")

    lines.append("\nSPENDING BY CATEGORY:")
    for category, total in sorted(category_totals.items(), key=lambda x: -x[1]):
        readable = category.replace("_", " ").title()
        pct = (total / month_total * 100) if month_total > 0 else 0
        lines.append(f"- {readable}: ${total:.2f} ({pct:.0f}%)")

    # Only include recent transactions, limited to 5
    lines.append("\nRECENT TRANSACTIONS (last 5):")
    for txn in transactions[:5]:
        amount = txn['amount']
        if amount <= 0:
            continue
        prefix = "-"
        lines.append(f"  {prefix} {txn['date']} {txn['name']}: ${abs(amount):.2f}")

    return "\n".join(lines)

# ---------- Combined snapshot ----------

def get_financial_snapshot(access_token: str) -> str:
    try:
        balances = get_balances(access_token)
        transactions = get_transactions(access_token)
        return f"{balances}\n\n{transactions}"
    except Exception as e:
        error_str = str(e)
        print(f"Plaid API Exception caught: {error_str}", flush=True)
        if "ITEM_LOGIN_REQUIRED" in error_str:
            return "BANK_REAUTH_REQUIRED"
        return "NO_BANK_DATA"

# ---------- Update Mode Link Token ----------

def create_update_link_token(user_id: str, access_token: str) -> str:
    """
    Creates a Plaid Link token in Update Mode for a broken access token.
    Launches direct bank sync to clear the ITEM_LOGIN_REQUIRED status.
    """
    request = LinkTokenCreateRequest(
        user=LinkTokenCreateRequestUser(client_user_id=user_id),
        client_name="FISCAL",
        country_codes=[CountryCode("CA")],
        language="en",
        access_token=access_token # Passing this parameter triggers Update Mode
    )
    response = plaid_client.link_token_create(request)
    return response["link_token"]


def create_link_token(user_id: str) -> str:
    """Creates a Plaid Link token for the given user."""
    request = LinkTokenCreateRequest(
        user=LinkTokenCreateRequestUser(client_user_id=user_id),
        client_name="FISCAL",
        products=[Products("transactions")],
        country_codes=[CountryCode("CA")],
        language="en",
    )
    response = plaid_client.link_token_create(request)
    return response["link_token"]

def exchange_public_token(public_token: str) -> str:
    """Exchanges a public token for a permanent access token."""
    request = ItemPublicTokenExchangeRequest(public_token=public_token)
    response = plaid_client.item_public_token_exchange(request)
    return response["access_token"]


def get_chart_data(access_token: str) -> dict:
    """Returns burn-down velocity chart data based on chequing account."""
    end_date = date.today()
    start_date = end_date.replace(day=1)

    # Get balances
    accounts = []
    chequing_balance = 0.0
    chequing_account_id = None

    try:
        balance_req = AccountsBalanceGetRequest(access_token=access_token)
        balance_resp = plaid_client.accounts_balance_get(balance_req)
        for account in balance_resp['accounts']:
            current = account['balances']['current']
            if current is None:
                continue
            subtype = str(account['subtype'])
            
            # Find the main chequing account
            if subtype == 'checking':
                chequing_balance = current
                chequing_account_id = account['account_id']

            # Skip mortgage and line of credit from display
            if subtype in ['mortgage', 'line of credit']:
                continue

            accounts.append({
                "name": account['name'],
                "type": subtype,
                "balance": round(current, 2),
            })
    except Exception as e:
        print(f"Balance error in chart_data: {e}", flush=True)

    # Get transactions
    burndown = []
    income_total = 0.0
    expense_total = 0.0

    try:
        request = TransactionsGetRequest(
            access_token=access_token,
            start_date=start_date,
            end_date=end_date,
            options=TransactionsGetRequestOptions(
                count=300,
                include_personal_finance_category=True
            )
        )
        response = plaid_client.transactions_get(request)
        transactions = response['transactions']

        # Separate spending by day across chequing + credit cards
        daily_net: dict[str, float] = {}

        for txn in transactions:
            amount = txn['amount']
            txn_date = str(txn['date'])
            category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

            # Skip internal transfers between own accounts
            if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
                continue

            # Skip loan payments that are actually payroll
            name_lower = txn['name'].lower()
            if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
                income_total += amount
                daily_net[txn_date] = daily_net.get(txn_date, 0) - amount  # income adds to balance
                continue

            if amount < 0:
                # Money coming in (income)
                income_total += abs(amount)
                daily_net[txn_date] = daily_net.get(txn_date, 0) + abs(amount)  # adds to balance
            else:
                # Money going out (spending)
                expense_total += amount
                daily_net[txn_date] = daily_net.get(txn_date, 0) - amount  # subtracts from balance

        # Reconstruct daily balance working BACKWARD from today's chequing balance
        # today_balance = chequing_balance
        # yesterday_balance = today_balance - net_change_today
        # (because net_change is already applied to get to today's balance)
        
        daily_balances: dict[str, float] = {}
        running = chequing_balance
        
        # Work backward from today
        current = end_date
        while current >= start_date:
            day_str = str(current)
            daily_balances[day_str] = running
            # Undo this day's net change to get previous day's balance
            net_today = daily_net.get(day_str, 0)
            running = running - net_today  # undo: if we spent $50 (net=-50), previous day was +50 higher
            current -= timedelta(days=1)

        # Now build burndown in forward order
        current = start_date
        while current <= end_date:
            day_str = str(current)
            balance = daily_balances.get(day_str, 0)
            day_spend = 0
            
            # Calculate just spending for this day (not net)
            for txn in transactions:
                if str(txn['date']) == day_str and txn['amount'] > 0:
                    cat = txn.get('personal_finance_category', {}).get('primary', 'OTHER')
                    if cat not in ['TRANSFER_IN', 'TRANSFER_OUT']:
                        day_spend += txn['amount']

            burndown.append({
                "date": current.strftime("%b %d"),
                "balance": round(balance, 2),
                "spent": round(day_spend, 2),
            })
            current += timedelta(days=1)

    except Exception as e:
        print(f"Transaction error in chart_data: {e}", flush=True)

    return {
        "burndown": burndown,
        "income_total": round(income_total, 2),
        "expense_total": round(expense_total, 2),
        "accounts": accounts,
    }
    """Returns burn-down velocity chart data."""
    end_date = date.today()
    start_date = end_date.replace(day=1)  # Start of current month

    # Get balances
    accounts = []
    try:
        balance_req = AccountsBalanceGetRequest(access_token=access_token)
        balance_resp = plaid_client.accounts_balance_get(balance_req)
        for account in balance_resp['accounts']:
            current = account['balances']['current']
            if current is None:
                continue
            accounts.append({
                "name": account['name'],
                "type": str(account['subtype']),
                "balance": round(current, 2),
            })
    except Exception as e:
        print(f"Balance error in chart_data: {e}", flush=True)

    # Get transactions for current month
    burndown = []
    income_total = 0.0
    expense_total = 0.0

    try:
        request = TransactionsGetRequest(
            access_token=access_token,
            start_date=start_date,
            end_date=end_date,
            options=TransactionsGetRequestOptions(
                count=200,
                include_personal_finance_category=True
            )
        )
        response = plaid_client.transactions_get(request)
        transactions = response['transactions']

        # Build daily income and spending
        daily_income: dict[str, float] = {}
        daily_spending: dict[str, float] = {}

        for txn in transactions:
            amount = txn['amount']
            txn_date = str(txn['date'])
            category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

            if amount < 0:
                income_total += abs(amount)
                daily_income[txn_date] = daily_income.get(txn_date, 0) + abs(amount)
                continue

            if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
                continue

            name_lower = txn['name'].lower()
            if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
                income_total += amount
                daily_income[txn_date] = daily_income.get(txn_date, 0) + amount
                continue

            expense_total += amount
            daily_spending[txn_date] = daily_spending.get(txn_date, 0) + amount

        # Build burn-down: start with total income, subtract spending each day
        running_balance = income_total
        current = start_date
        while current <= end_date:
            day_str = str(current)
            day_spend = daily_spending.get(day_str, 0)
            day_income = daily_income.get(day_str, 0)
            running_balance = running_balance - day_spend + (day_income if current != start_date else 0)

            burndown.append({
                "date": current.strftime("%b %d"),
                "balance": round(running_balance, 2),
                "spent": round(day_spend, 2),
            })
            current += timedelta(days=1)

    except Exception as e:
        print(f"Transaction error in chart_data: {e}", flush=True)

    return {
        "burndown": burndown,
        "income_total": round(income_total, 2),
        "expense_total": round(expense_total, 2),
        "accounts": accounts,
    }
    """Returns structured JSON for frontend charts."""
    end_date = date.today()
    start_date = end_date - timedelta(days=30)

    # Get balances (usually ready immediately)
    try:
        balance_req = AccountsBalanceGetRequest(access_token=access_token)
        balance_resp = plaid_client.accounts_balance_get(balance_req)
        accounts = []
        for account in balance_resp['accounts']:
            current = account['balances']['current']
            if current is None:
                continue
            accounts.append({
                "name": account['name'],
                "type": str(account['subtype']),
                "balance": round(current, 2),
            })
    except Exception as e:
        print(f"Balance error in chart_data: {e}", flush=True)
        accounts = []

    # Get transactions (may not be ready yet)
    category_chart = []
    weekly_data = []
    income_total = 0.0
    expense_total = 0.0

    try:
        request = TransactionsGetRequest(
            access_token=access_token,
            start_date=start_date,
            end_date=end_date,
            options=TransactionsGetRequestOptions(
                count=200,
                include_personal_finance_category=True
            )
        )
        response = plaid_client.transactions_get(request)
        transactions = response['transactions']

        category_totals: dict[str, float] = {}
        daily_spending: dict[str, float] = {}
        daily_income: dict[str, float] = {}

        for txn in transactions:
            amount = txn['amount']
            txn_date = str(txn['date'])
            category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

            if amount < 0:
                income_total += abs(amount)
                daily_income[txn_date] = daily_income.get(txn_date, 0) + abs(amount)
                continue

            if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
                continue

            name_lower = txn['name'].lower()
            if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
                income_total += amount
                daily_income[txn_date] = daily_income.get(txn_date, 0) + amount
                continue

            expense_total += amount
            readable = category.replace("_", " ").title()
            category_totals[readable] = category_totals.get(readable, 0) + amount
            daily_spending[txn_date] = daily_spending.get(txn_date, 0) + amount

        category_chart = [
            {"name": cat, "value": round(total, 2)}
            for cat, total in sorted(category_totals.items(), key=lambda x: -x[1])
        ]

        for i in range(4):
            week_end = end_date - timedelta(weeks=i)
            week_start_d = week_end - timedelta(days=6)
            week_label = f"{week_start_d.strftime('%b %d')} - {week_end.strftime('%b %d')}"
            week_spending = sum(v for k, v in daily_spending.items() if str(week_start_d) <= k <= str(week_end))
            week_income = sum(v for k, v in daily_income.items() if str(week_start_d) <= k <= str(week_end))
            weekly_data.append({"week": week_label, "spending": round(week_spending, 2), "income": round(week_income, 2)})
        weekly_data.reverse()

    except Exception as e:
        print(f"Transaction error in chart_data: {e}", flush=True)

    return {
        "category_chart": category_chart,
        "weekly_chart": weekly_data,
        "income_vs_expenses": {
            "income": round(income_total, 2),
            "expenses": round(expense_total, 2),
        },
        "accounts": accounts,
    }
    """Returns structured JSON for frontend charts."""
    end_date = date.today()
    start_date = end_date - timedelta(days=30)

    # Get transactions
    request = TransactionsGetRequest(
        access_token=access_token,
        start_date=start_date,
        end_date=end_date,
        options=TransactionsGetRequestOptions(
            count=200,
            include_personal_finance_category=True
        )
    )
    response = plaid_client.transactions_get(request)
    transactions = response['transactions']

    # Get balances
    balance_req = AccountsBalanceGetRequest(access_token=access_token)
    balance_resp = plaid_client.accounts_balance_get(balance_req)

    # 1. Spending by category
    category_totals: dict[str, float] = {}
    income_total = 0.0
    expense_total = 0.0
    
    # 2. Daily spending for weekly breakdown
    daily_spending: dict[str, float] = {}
    daily_income: dict[str, float] = {}

    for txn in transactions:
        amount = txn['amount']
        txn_date = str(txn['date'])
        category = txn.get('personal_finance_category', {}).get('primary', 'OTHER')

        if amount < 0:
            income_total += abs(amount)
            daily_income[txn_date] = daily_income.get(txn_date, 0) + abs(amount)
            continue

        if category in ['TRANSFER_IN', 'TRANSFER_OUT']:
            continue

        name_lower = txn['name'].lower()
        if category == 'LOAN_PAYMENTS' and any(w in name_lower for w in ['payroll', 'salary', 'direct dep', 'employer', 'wages']):
            income_total += amount
            daily_income[txn_date] = daily_income.get(txn_date, 0) + amount
            continue

        expense_total += amount
        readable = category.replace("_", " ").title()
        category_totals[readable] = category_totals.get(readable, 0) + amount
        daily_spending[txn_date] = daily_spending.get(txn_date, 0) + amount

    # Build category chart data (sorted by amount)
    category_chart = [
        {"name": cat, "value": round(total, 2)}
        for cat, total in sorted(category_totals.items(), key=lambda x: -x[1])
    ]

    # Build weekly chart data (last 4 weeks)
    weekly_data = []
    for i in range(4):
        week_end = end_date - timedelta(weeks=i)
        week_start = week_end - timedelta(days=6)
        week_label = f"{week_start.strftime('%b %d')} - {week_end.strftime('%b %d')}"

        week_spending = sum(
            v for k, v in daily_spending.items()
            if str(week_start) <= k <= str(week_end)
        )
        week_income = sum(
            v for k, v in daily_income.items()
            if str(week_start) <= k <= str(week_end)
        )

        weekly_data.append({
            "week": week_label,
            "spending": round(week_spending, 2),
            "income": round(week_income, 2),
        })

    weekly_data.reverse()

    # Build account balances
    accounts = []
    for account in balance_resp['accounts']:
        current = account['balances']['current']
        if current is None:
            continue
        accounts.append({
            "name": account['name'],
            "type": str(account['subtype']),
            "balance": round(current, 2),
        })

    return {
        "category_chart": category_chart,
        "weekly_chart": weekly_data,
        "income_vs_expenses": {
            "income": round(income_total, 2),
            "expenses": round(expense_total, 2),
        },
        "accounts": accounts,
    }