package processor

import (
	"context"
	"math"
	"strings"
	"time"

	"github.com/google/uuid"

	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/models"
	"apskel-pos-be/internal/repository"
)

// enakGameAnalyticsMaxDays bounds a range, so one request cannot scan years of ledger.
const enakGameAnalyticsMaxDays = 366

// EnakGameAnalyticsProcessor answers the EnakGame dashboards (docs/tasks-enakgame.md
// EG-903, PRD §36) for an organization and a range of days in Asia/Jakarta.
type EnakGameAnalyticsProcessor struct {
	analytics repository.EnakGameAnalyticsRepository
}

func NewEnakGameAnalyticsProcessor(analytics repository.EnakGameAnalyticsRepository) *EnakGameAnalyticsProcessor {
	return &EnakGameAnalyticsProcessor{analytics: analytics}
}

// analyticsRange reads from and to, both days included, as [start, end).
func analyticsRange(q models.EnakGameAnalyticsQuery) (start, end time.Time, err error) {
	from, err := time.Parse("2006-01-02", strings.TrimSpace(q.From))
	if err != nil {
		return start, end, enakGameRejected("from must be a date like 2026-10-01")
	}
	to, err := time.Parse("2006-01-02", strings.TrimSpace(q.To))
	if err != nil {
		return start, end, enakGameRejected("to must be a date like 2026-10-31")
	}
	if to.Before(from) {
		return start, end, enakGameRejected("to cannot be before from")
	}
	if daysBetween(from, to)+1 > enakGameAnalyticsMaxDays {
		return start, end, enakGameRejected("the range can span at most %d days", enakGameAnalyticsMaxDays)
	}
	return jakartaMidnight(from), jakartaMidnight(to.AddDate(0, 0, 1)), nil
}

// Games is how the organization's games were played, by the day each session
// started.
func (p *EnakGameAnalyticsProcessor) Games(ctx context.Context, organizationID uuid.UUID, q models.EnakGameAnalyticsQuery) (*models.EnakGameAnalytics, error) {
	start, end, err := analyticsRange(q)
	if err != nil {
		return nil, err
	}
	var gameID *uuid.UUID
	if s := strings.TrimSpace(q.GameID); s != "" {
		id, err := uuid.Parse(s)
		if err != nil {
			return nil, enakGameRejected("game_id must be a UUID")
		}
		gameID = &id
	}
	rows, err := p.analytics.SessionStats(ctx, organizationID, start, end, gameID)
	if err != nil {
		return nil, err
	}
	out := &models.EnakGameAnalytics{From: strings.TrimSpace(q.From), To: strings.TrimSpace(q.To), Games: []models.EnakGameGameStats{}}
	for _, row := range rows {
		if row.GameID == nil {
			out.Totals = gameStats(row)
			continue
		}
		g := models.EnakGameGameStats{GameID: *row.GameID, EnakGameStats: gameStats(row)}
		if row.GameName != nil {
			g.GameName = *row.GameName
		}
		out.Games = append(out.Games, g)
	}
	return out, nil
}

func gameStats(r repository.GameSessionStats) models.EnakGameStats {
	s := models.EnakGameStats{
		Plays: r.Plays, Completed: r.Completed, Refunded: r.Refunded, Expired: r.Expired, Flagged: r.Flagged,
		Players: r.Players, AverageScore: r.AverageScore, CoinIssued: r.CoinIssued,
		EntryCostPaid: r.EntryCost, CoinRefunded: r.CoinRefunded,
	}
	if r.Completed > 0 {
		s.AverageReward = ratio(r.CoinIssued, r.Completed)
	}
	if r.Plays > 0 {
		s.RewardPerPlay = ratio(r.CoinIssued, r.Plays)
	}
	return s
}

// ratio is part / whole with two decimals.
func ratio(part, whole int64) float64 {
	return math.Round(float64(part)*100/float64(whole)) / 100
}

// Economy is how EnakCoin and EnakPoint moved in the organization, from the ledger.
func (p *EnakGameAnalyticsProcessor) Economy(ctx context.Context, organizationID uuid.UUID, q models.EnakGameAnalyticsQuery) (*models.EnakGameEconomyAnalytics, error) {
	start, end, err := analyticsRange(q)
	if err != nil {
		return nil, err
	}
	flows, err := p.analytics.WalletFlows(ctx, organizationID, start, end)
	if err != nil {
		return nil, err
	}
	balances, err := p.analytics.BalancesAt(ctx, organizationID, end)
	if err != nil {
		return nil, err
	}
	out := economy(flows, balances)
	out.From, out.To = strings.TrimSpace(q.From), strings.TrimSpace(q.To)
	return out, nil
}

// economy turns ledger totals into the headline numbers. Transfers move value between
// customers and count in none of them; ByType still lists them.
func economy(flows []repository.WalletFlow, balances map[string]int64) *models.EnakGameEconomyAnalytics {
	type key struct{ currency, txType string }
	byKey := make(map[key]repository.WalletFlow, len(flows))
	out := &models.EnakGameEconomyAnalytics{ByType: make([]models.WalletFlowTotals, 0, len(flows))}
	for _, f := range flows {
		byKey[key{f.Currency, f.Type}] = f
		out.ByType = append(out.ByType, models.WalletFlowTotals{
			Currency: f.Currency, Type: f.Type, Credit: f.Credit, Debit: f.Debit, Transactions: f.Transactions,
		})
	}
	coin := func(txType string) repository.WalletFlow { return byKey[key{constants.WalletCurrencyCoin, txType}] }
	point := func(txType string) repository.WalletFlow { return byKey[key{constants.WalletCurrencyPoint, txType}] }

	c := &out.Coin
	c.GameRewards = coin(constants.WalletTxTypeGameReward).Credit
	c.Generated = c.GameRewards + coin(constants.WalletTxTypeEarn).Credit - coin(constants.WalletTxTypeEarnReversal).Debit +
		coin(constants.WalletTxTypeMigration).Credit + coin(constants.WalletTxTypeAdjustment).Credit
	c.SpentOnGames = coin(constants.WalletTxTypeGameSpend).Debit - coin(constants.WalletTxTypeGameSpendRefund).Credit
	c.Exchanged = coin(constants.WalletTxTypeExchangeOut).Debit
	c.Spent = c.SpentOnGames + c.Exchanged
	c.Expired = coin(constants.WalletTxTypeExpire).Debit
	c.Outstanding = balances[constants.WalletCurrencyCoin]

	pt := &out.Point
	pt.Earned = point(constants.WalletTxTypeEarn).Credit - point(constants.WalletTxTypeEarnReversal).Debit
	pt.Exchanged = point(constants.WalletTxTypeExchangeIn).Credit
	pt.Redeemed = point(constants.WalletTxTypeRewardRedeem).Debit - point(constants.WalletTxTypeRewardRedeemRefund).Credit
	pt.Expired = point(constants.WalletTxTypeExpire).Debit
	pt.Balance = balances[constants.WalletCurrencyPoint]
	return out
}