package models

import (
	"math"
	"time"

	"github.com/google/uuid"
)

// OutletLoyaltySettings are an outlet's loyalty settings (docs/prd-point-coin.md F1).
type OutletLoyaltySettings struct {
	Point LoyaltyEarnSettings `json:"point"`
	Coin  LoyaltyEarnSettings `json:"coin"`
	// Paying with EnakPoint. EnakCoin cannot pay, so it has no counterpart.
	PointPayment LoyaltyPointPaymentSettings `json:"point_payment"`
}

// LoyaltyEarnSettings is how much of one currency an order earns:
// floor(basis / EarnPerAmount) × EarnValue, nothing below MinOrderAmount, and at most
// MaxPerOrder when set.
type LoyaltyEarnSettings struct {
	Enabled        bool   `json:"enabled"`
	EarnPerAmount  int64  `json:"earn_per_amount"`
	EarnValue      int64  `json:"earn_value"`
	MinOrderAmount int64  `json:"min_order_amount"`
	MaxPerOrder    *int64 `json:"max_per_order"`
}

type LoyaltyPointPaymentSettings struct {
	AcceptPayment    bool  `json:"accept_payment"`
	MinPaymentPoints int64 `json:"min_payment_points"`
	// Largest share of the order total, 0–100, that EnakPoint may pay.
	MaxPaymentPercent int64 `json:"max_payment_percent"`
}

// OrganizationLoyaltySettings are the loyalty settings shared by every outlet of an
// organization (docs/prd-point-coin.md F2, F12).
type OrganizationLoyaltySettings struct {
	// Rupiah value of one EnakPoint when paying.
	PointValue int64 `json:"point_value"`
	// CoinAmount EnakCoin exchange into PointAmount EnakPoint.
	Exchange    LoyaltyExchangeSettings `json:"exchange"`
	Transfer    LoyaltyTransferSettings `json:"transfer"`
	PointExpiry LoyaltyExpirySettings   `json:"point_expiry"`
	CoinExpiry  LoyaltyExpirySettings   `json:"coin_expiry"`
}

type LoyaltyExchangeSettings struct {
	CoinAmount  int64 `json:"coin_amount"`
	PointAmount int64 `json:"point_amount"`
}

type LoyaltyTransferSettings struct {
	Enabled           bool   `json:"enabled"`
	MinAmount         int64  `json:"min_amount"`
	MaxPerTransaction *int64 `json:"max_per_transaction"`
	DailyLimit        *int64 `json:"daily_limit"`
}

// LoyaltyExpirySettings is how long one currency lasts once received. The expiry
// model is still open (note N4); these are only the stored settings.
type LoyaltyExpirySettings struct {
	Enabled bool  `json:"enabled"`
	Period  int64 `json:"period"`
	// DAY or MONTH.
	Unit         string `json:"unit"`
	EndOfMonth   bool   `json:"end_of_month"`
	ReminderDays int64  `json:"reminder_days"`
}

// LoyaltySettingChange is one row of the loyalty settings history.
type LoyaltySettingChange struct {
	ID             uuid.UUID  `json:"id"`
	OrganizationID uuid.UUID  `json:"organization_id"`
	OutletID       *uuid.UUID `json:"outlet_id"`
	Key            string     `json:"key"`
	// Nil when the key had no stored value, that is it was on its default.
	OldValue  *string   `json:"old_value"`
	NewValue  *string   `json:"new_value"`
	ChangedBy uuid.UUID `json:"changed_by"`
	CreatedAt time.Time `json:"created_at"`
}

// OutletLoyaltySettingsView is GET and PUT /outlets/:id/loyalty-settings.
type OutletLoyaltySettingsView struct {
	OutletID uuid.UUID `json:"outlet_id"`
	OutletLoyaltySettings
	// The organization's rupiah value of one EnakPoint, which the cashback depends on.
	PointValue int64 `json:"point_value"`
	// Effective EnakPoint cashback in percent: earn_value × point_value /
	// earn_per_amount × 100. Shown next to the setting so an owner cannot misread the
	// scale (F1).
	PointCashbackPercent float64 `json:"point_cashback_percent"`
	// Set on PUT: the keys that changed.
	Changes []LoyaltySettingChange `json:"changes,omitempty"`
}

// LoyaltyCashbackPercent is earnValue × pointValue / earnPerAmount as a percentage,
// rounded to two decimals.
func LoyaltyCashbackPercent(earnValue, pointValue, earnPerAmount int64) float64 {
	if earnPerAmount <= 0 {
		return 0
	}
	return math.Round(float64(earnValue)*float64(pointValue)*10000/float64(earnPerAmount)) / 100
}

// OrganizationLoyaltySettingsView is GET and PUT /marketing/loyalty-settings.
type OrganizationLoyaltySettingsView struct {
	OrganizationLoyaltySettings
	// What the balances in circulation are worth, before and after the change.
	Impact LoyaltySettingsImpact `json:"impact"`
	// On PUT, the keys that changed; on a dry run, the keys that would.
	Changes []LoyaltySettingChange `json:"changes"`
	// True when nothing was saved.
	DryRun bool `json:"dry_run"`
}

// LoyaltySettingsImpact shows how a change of point value or exchange rate changes what
// the balances in circulation are worth (F2). Before and after are equal when neither
// changes.
type LoyaltySettingsImpact struct {
	OutstandingPoints int64 `json:"outstanding_points"`
	OutstandingCoins  int64 `json:"outstanding_coins"`

	PointValueBefore  int64 `json:"point_value_before"`
	PointValueAfter   int64 `json:"point_value_after"`
	PointRupiahBefore int64 `json:"point_rupiah_before"`
	PointRupiahAfter  int64 `json:"point_rupiah_after"`

	// The coins in circulation exchanged at the rate, in EnakPoint and in rupiah.
	CoinsAsPointsBefore int64 `json:"coins_as_points_before"`
	CoinsAsPointsAfter  int64 `json:"coins_as_points_after"`
	CoinRupiahBefore    int64 `json:"coin_rupiah_before"`
	CoinRupiahAfter     int64 `json:"coin_rupiah_after"`
}

// NewLoyaltySettingsImpact computes the impact of moving from one organization setting
// to another on the balances in circulation.
func NewLoyaltySettingsImpact(points, coins int64, before, after OrganizationLoyaltySettings) LoyaltySettingsImpact {
	asPoints := func(s OrganizationLoyaltySettings) int64 {
		if s.Exchange.CoinAmount <= 0 {
			return 0
		}
		return coins * s.Exchange.PointAmount / s.Exchange.CoinAmount
	}
	impact := LoyaltySettingsImpact{
		OutstandingPoints:   points,
		OutstandingCoins:    coins,
		PointValueBefore:    before.PointValue,
		PointValueAfter:     after.PointValue,
		PointRupiahBefore:   points * before.PointValue,
		PointRupiahAfter:    points * after.PointValue,
		CoinsAsPointsBefore: asPoints(before),
		CoinsAsPointsAfter:  asPoints(after),
	}
	impact.CoinRupiahBefore = impact.CoinsAsPointsBefore * before.PointValue
	impact.CoinRupiahAfter = impact.CoinsAsPointsAfter * after.PointValue
	return impact
}