package financial

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"github.com/felt-app/felt/internal/audit"
	"github.com/felt-app/felt/internal/server/middleware"
	"github.com/felt-app/felt/internal/template"
)

// PrizePoolSummary contains the full prize pool breakdown for a tournament.
type PrizePoolSummary struct {
	TotalEntries       int              `json:"total_entries"`       // Unique entries only
	TotalRebuys        int              `json:"total_rebuys"`
	TotalAddOns        int              `json:"total_addons"`
	TotalReEntries     int              `json:"total_reentries"`
	TotalBuyInAmount   int64            `json:"total_buyin_amount"`  // cents
	TotalRebuyAmount   int64            `json:"total_rebuy_amount"`  // cents
	TotalAddOnAmount   int64            `json:"total_addon_amount"`  // cents
	TotalReEntryAmount int64            `json:"total_reentry_amount"` // cents
	TotalRake          int64            `json:"total_rake"`          // All rake combined
	RakeByCategory     map[string]int64 `json:"rake_by_category"`   // house, staff, league, season_reserve
	PrizePool          int64            `json:"prize_pool"`          // After rake, before guarantee
	Guarantee          int64            `json:"guarantee"`           // Configured guarantee
	HouseContribution  int64            `json:"house_contribution"`  // If pool < guarantee
	FinalPrizePool     int64            `json:"final_prize_pool"`    // Max(PrizePool, Guarantee)
	TotalBountyPool    int64            `json:"total_bounty_pool"`   // PKO bounties
	TotalChipsInPlay   int64            `json:"total_chips_in_play"` // CHIP-03
	AverageStack       int64            `json:"average_stack"`       // CHIP-04
	RemainingPlayers   int              `json:"remaining_players"`
}

// Payout represents a single position's payout.
type Payout struct {
	Position   int   `json:"position"`
	Amount     int64 `json:"amount"`     // cents
	Percentage int64 `json:"percentage"` // basis points (e.g., 5000 = 50.00%)
}

// BubblePrizeProposal represents a proposed bubble prize redistribution.
type BubblePrizeProposal struct {
	ID               int64           `json:"id"`
	TournamentID     string          `json:"tournament_id"`
	Amount           int64           `json:"amount"` // cents
	OriginalPayouts  []Payout        `json:"original_payouts"`
	AdjustedPayouts  []Payout        `json:"adjusted_payouts"`
	FundedFrom       json.RawMessage `json:"funded_from"` // JSON array of {position, reduction_amount}
	Status           string          `json:"status"`
}

// FundingSource documents how much was shaved from each position.
type FundingSource struct {
	Position        int   `json:"position"`
	ReductionAmount int64 `json:"reduction_amount"` // cents
}

// CalculatePrizePool computes the full prize pool breakdown for a tournament.
func (e *Engine) CalculatePrizePool(ctx context.Context, tournamentID string) (*PrizePoolSummary, error) {
	summary := &PrizePoolSummary{
		RakeByCategory: make(map[string]int64),
	}

	// Count unique entries (distinct players with non-undone buyins)
	err := e.db.QueryRowContext(ctx,
		`SELECT COUNT(DISTINCT player_id) FROM transactions
		 WHERE tournament_id = ? AND type = 'buyin' AND undone = 0`,
		tournamentID,
	).Scan(&summary.TotalEntries)
	if err != nil {
		return nil, fmt.Errorf("financial: count entries: %w", err)
	}

	// Sum amounts by type (non-undone only)
	rows, err := e.db.QueryContext(ctx,
		`SELECT type, COUNT(*), COALESCE(SUM(amount), 0)
		 FROM transactions
		 WHERE tournament_id = ? AND undone = 0
		 AND type IN ('buyin', 'rebuy', 'addon', 'reentry')
		 GROUP BY type`,
		tournamentID,
	)
	if err != nil {
		return nil, fmt.Errorf("financial: sum amounts: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var txType string
		var count int
		var amount int64
		if err := rows.Scan(&txType, &count, &amount); err != nil {
			return nil, fmt.Errorf("financial: scan amount: %w", err)
		}
		switch txType {
		case TxTypeBuyIn:
			summary.TotalBuyInAmount = amount
		case TxTypeRebuy:
			summary.TotalRebuys = count
			summary.TotalRebuyAmount = amount
		case TxTypeAddon:
			summary.TotalAddOns = count
			summary.TotalAddOnAmount = amount
		case TxTypeReentry:
			summary.TotalReEntries = count
			summary.TotalReEntryAmount = amount
		}
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	// Sum rake by category
	rakeRows, err := e.db.QueryContext(ctx,
		`SELECT COALESCE(json_extract(metadata, '$.category'), 'unknown'), COALESCE(SUM(amount), 0)
		 FROM transactions
		 WHERE tournament_id = ? AND type = 'rake' AND undone = 0
		 GROUP BY json_extract(metadata, '$.category')`,
		tournamentID,
	)
	if err != nil {
		return nil, fmt.Errorf("financial: sum rake: %w", err)
	}
	defer rakeRows.Close()

	for rakeRows.Next() {
		var category string
		var amount int64
		if err := rakeRows.Scan(&category, &amount); err != nil {
			return nil, fmt.Errorf("financial: scan rake: %w", err)
		}
		summary.RakeByCategory[category] = amount
		summary.TotalRake += amount
	}
	if err := rakeRows.Err(); err != nil {
		return nil, err
	}

	// Prize pool = total contributions minus rake
	totalContributions := summary.TotalBuyInAmount + summary.TotalRebuyAmount +
		summary.TotalAddOnAmount + summary.TotalReEntryAmount
	summary.PrizePool = totalContributions - summary.TotalRake

	// Load guarantee from tournament (stored in buyin config or tournament)
	// For now, guarantee comes from the payout structure or a tournament setting
	summary.Guarantee = 0 // TODO: load from tournament config when guarantee field is added
	if summary.PrizePool < summary.Guarantee {
		summary.HouseContribution = summary.Guarantee - summary.PrizePool
	}
	summary.FinalPrizePool = summary.PrizePool
	if summary.Guarantee > 0 && summary.PrizePool < summary.Guarantee {
		summary.FinalPrizePool = summary.Guarantee
	}

	// Bounty pool for PKO
	err = e.db.QueryRowContext(ctx,
		`SELECT COALESCE(SUM(bounty_value), 0) FROM tournament_players
		 WHERE tournament_id = ? AND status = 'active'`,
		tournamentID,
	).Scan(&summary.TotalBountyPool)
	if err != nil {
		return nil, fmt.Errorf("financial: sum bounties: %w", err)
	}

	// Chips in play and remaining players
	err = e.db.QueryRowContext(ctx,
		`SELECT COALESCE(SUM(current_chips), 0), COUNT(*)
		 FROM tournament_players
		 WHERE tournament_id = ? AND status IN ('active', 'deal')`,
		tournamentID,
	).Scan(&summary.TotalChipsInPlay, &summary.RemainingPlayers)
	if err != nil {
		return nil, fmt.Errorf("financial: chip stats: %w", err)
	}

	if summary.RemainingPlayers > 0 {
		summary.AverageStack = summary.TotalChipsInPlay / int64(summary.RemainingPlayers)
	}

	return summary, nil
}

// CalculatePayouts computes the payout table for a tournament based on its
// entry count and payout structure. All math uses int64 cents. Rounding is
// always DOWN to the venue's configured denomination. Remainder goes to 1st.
func (e *Engine) CalculatePayouts(ctx context.Context, tournamentID string) ([]Payout, error) {
	// Load prize pool
	summary, err := e.CalculatePrizePool(ctx, tournamentID)
	if err != nil {
		return nil, err
	}

	// Load tournament's payout structure ID
	ti, err := e.loadTournamentInfo(ctx, tournamentID)
	if err != nil {
		return nil, err
	}

	// Load payout structure
	payoutSvc := template.NewPayoutService(e.db)
	ps, err := payoutSvc.GetPayoutStructure(ctx, ti.PayoutStructureID)
	if err != nil {
		return nil, fmt.Errorf("financial: load payout structure: %w", err)
	}

	// Load venue rounding denomination
	roundingDenom := e.loadRoundingDenomination(ctx)

	// Select bracket by unique entry count
	bracket := selectBracket(ps.Brackets, summary.TotalEntries)
	if bracket == nil {
		return nil, fmt.Errorf("financial: no payout bracket for %d entries", summary.TotalEntries)
	}

	return CalculatePayoutsFromPool(summary.FinalPrizePool, bracket.Tiers, roundingDenom)
}

// CalculatePayoutsFromPool is the pure calculation function. It takes a prize pool,
// payout tiers, and rounding denomination, and returns the payout table.
// CRITICAL: sum(payouts) must ALWAYS equal prizePool.
func CalculatePayoutsFromPool(prizePool int64, tiers []template.PayoutTier, roundingDenomination int64) ([]Payout, error) {
	if len(tiers) == 0 {
		return nil, fmt.Errorf("financial: no payout tiers")
	}
	if prizePool <= 0 {
		return nil, fmt.Errorf("financial: prize pool must be positive")
	}
	if roundingDenomination <= 0 {
		roundingDenomination = 1 // No rounding
	}

	payouts := make([]Payout, len(tiers))
	var allocated int64

	for i, tier := range tiers {
		// Raw amount from percentage (basis points / 10000)
		raw := prizePool * tier.PercentageBasisPoints / 10000

		// Round DOWN to rounding denomination
		rounded := (raw / roundingDenomination) * roundingDenomination

		payouts[i] = Payout{
			Position:   tier.Position,
			Amount:     rounded,
			Percentage: tier.PercentageBasisPoints,
		}
		allocated += rounded
	}

	// Assign remainder to 1st place (standard poker convention)
	remainder := prizePool - allocated
	if remainder != 0 {
		// Find position 1
		for i := range payouts {
			if payouts[i].Position == 1 {
				payouts[i].Amount += remainder
				break
			}
		}
	}

	// CRITICAL ASSERTION: sum must equal prize pool
	var sum int64
	for _, p := range payouts {
		sum += p.Amount
	}
	if sum != prizePool {
		// This should never happen. If it does, it's a bug.
		return nil, fmt.Errorf("financial: CRITICAL payout sum mismatch: sum=%d prizePool=%d (diff=%d)", sum, prizePool, sum-prizePool)
	}

	return payouts, nil
}

// ApplyPayouts creates payout transactions for each finishing position.
func (e *Engine) ApplyPayouts(ctx context.Context, tournamentID string, payouts []Payout) error {
	operatorID := middleware.OperatorIDFromCtx(ctx)

	for _, p := range payouts {
		// Find player at this finishing position
		var playerID string
		err := e.db.QueryRowContext(ctx,
			`SELECT player_id FROM tournament_players
			 WHERE tournament_id = ? AND finishing_position = ?`,
			tournamentID, p.Position,
		).Scan(&playerID)
		if err == sql.ErrNoRows {
			continue // No player at this position yet
		}
		if err != nil {
			return fmt.Errorf("financial: find player at position %d: %w", p.Position, err)
		}

		tx := &Transaction{
			ID:           generateUUID(),
			TournamentID: tournamentID,
			PlayerID:     playerID,
			Type:         TxTypePayout,
			Amount:       p.Amount,
			Chips:        0,
			OperatorID:   operatorID,
			CreatedAt:    time.Now().Unix(),
		}
		metaJSON, _ := json.Marshal(map[string]interface{}{
			"position":   p.Position,
			"percentage": p.Percentage,
		})
		tx.Metadata = metaJSON

		if err := e.insertTransaction(ctx, tx); err != nil {
			return err
		}

		// Update player's prize_amount
		_, err = e.db.ExecContext(ctx,
			`UPDATE tournament_players SET prize_amount = ?, updated_at = unixepoch()
			 WHERE tournament_id = ? AND player_id = ?`,
			p.Amount, tournamentID, playerID,
		)
		if err != nil {
			return fmt.Errorf("financial: update prize amount: %w", err)
		}

		// Audit entry
		tournamentIDPtr := &tournamentID
		_, _ = e.trail.Record(ctx, audit.AuditEntry{
			TournamentID: tournamentIDPtr,
			Action:       audit.ActionFinancialPayout,
			TargetType:   "player",
			TargetID:     playerID,
			NewState:     metaJSON,
		})
	}

	e.broadcast(tournamentID, "financial.payouts_applied", payouts)
	return nil
}

// CalculateBubblePrize proposes a bubble prize by shaving from top positions.
func (e *Engine) CalculateBubblePrize(ctx context.Context, tournamentID string, amount int64) (*BubblePrizeProposal, error) {
	if amount <= 0 {
		return nil, fmt.Errorf("financial: bubble prize amount must be positive")
	}

	// Get current payouts
	payouts, err := e.CalculatePayouts(ctx, tournamentID)
	if err != nil {
		return nil, err
	}

	if len(payouts) < 2 {
		return nil, fmt.Errorf("financial: need at least 2 payout positions for bubble prize")
	}

	// Shave from top prizes proportionally (1st-3rd primarily, extending to 4th-5th if needed)
	funding, adjustedPayouts, err := redistributeForBubble(payouts, amount)
	if err != nil {
		return nil, err
	}

	fundedFromJSON, _ := json.Marshal(funding)

	// Insert proposal into bubble_prizes table
	res, err := e.db.ExecContext(ctx,
		`INSERT INTO bubble_prizes (tournament_id, amount, funded_from, status, created_at)
		 VALUES (?, ?, ?, 'proposed', ?)`,
		tournamentID, amount, string(fundedFromJSON), time.Now().Unix(),
	)
	if err != nil {
		return nil, fmt.Errorf("financial: insert bubble prize proposal: %w", err)
	}
	proposalID, _ := res.LastInsertId()

	return &BubblePrizeProposal{
		ID:              proposalID,
		TournamentID:    tournamentID,
		Amount:          amount,
		OriginalPayouts: payouts,
		AdjustedPayouts: adjustedPayouts,
		FundedFrom:      fundedFromJSON,
		Status:          "proposed",
	}, nil
}

// ConfirmBubblePrize confirms and applies a bubble prize proposal.
func (e *Engine) ConfirmBubblePrize(ctx context.Context, tournamentID string, proposalID int64) error {
	// Verify proposal exists and is pending
	var status string
	var amount int64
	err := e.db.QueryRowContext(ctx,
		"SELECT status, amount FROM bubble_prizes WHERE id = ? AND tournament_id = ?",
		proposalID, tournamentID,
	).Scan(&status, &amount)
	if err == sql.ErrNoRows {
		return fmt.Errorf("financial: bubble prize proposal not found")
	}
	if err != nil {
		return fmt.Errorf("financial: load bubble prize: %w", err)
	}
	if status != "proposed" {
		return fmt.Errorf("financial: bubble prize already %s", status)
	}

	// Update status to confirmed
	_, err = e.db.ExecContext(ctx,
		"UPDATE bubble_prizes SET status = 'confirmed' WHERE id = ?",
		proposalID,
	)
	if err != nil {
		return fmt.Errorf("financial: confirm bubble prize: %w", err)
	}

	// Audit
	metadataJSON, _ := json.Marshal(map[string]interface{}{
		"proposal_id": proposalID,
		"amount":      amount,
	})
	tournamentIDPtr := &tournamentID
	_, _ = e.trail.Record(ctx, audit.AuditEntry{
		TournamentID: tournamentIDPtr,
		Action:       audit.ActionFinancialBubblePrize,
		TargetType:   "tournament",
		TargetID:     tournamentID,
		NewState:     metadataJSON,
	})

	e.broadcast(tournamentID, "financial.bubble_prize_confirmed", map[string]interface{}{
		"proposal_id": proposalID,
		"amount":      amount,
	})

	return nil
}

// redistributeForBubble shaves from top positions to fund a bubble prize.
// Shaves proportionally from 1st-3rd, extending to 4th-5th if needed.
func redistributeForBubble(payouts []Payout, bubbleAmount int64) ([]FundingSource, []Payout, error) {
	// Determine how many positions to shave from (top 3, or top 5 if needed)
	maxShavePositions := 3
	if maxShavePositions > len(payouts) {
		maxShavePositions = len(payouts)
	}

	// Calculate total from shaveable positions
	var shaveableTotal int64
	for i := 0; i < maxShavePositions; i++ {
		shaveableTotal += payouts[i].Amount
	}

	// If top 3 can't cover it, extend to 5
	if shaveableTotal < bubbleAmount && len(payouts) > maxShavePositions {
		maxShavePositions = 5
		if maxShavePositions > len(payouts) {
			maxShavePositions = len(payouts)
		}
		shaveableTotal = 0
		for i := 0; i < maxShavePositions; i++ {
			shaveableTotal += payouts[i].Amount
		}
	}

	if shaveableTotal < bubbleAmount {
		return nil, nil, fmt.Errorf("financial: bubble prize %d exceeds total shaveable amount %d", bubbleAmount, shaveableTotal)
	}

	// Proportionally shave
	adjusted := make([]Payout, len(payouts))
	copy(adjusted, payouts)

	funding := make([]FundingSource, 0, maxShavePositions)
	var totalShaved int64

	for i := 0; i < maxShavePositions; i++ {
		var shaveAmount int64
		if i == maxShavePositions-1 {
			// Last position gets remainder
			shaveAmount = bubbleAmount - totalShaved
		} else {
			// Proportional share
			shaveAmount = bubbleAmount * payouts[i].Amount / shaveableTotal
		}

		if shaveAmount > adjusted[i].Amount {
			shaveAmount = adjusted[i].Amount
		}

		adjusted[i].Amount -= shaveAmount
		totalShaved += shaveAmount

		funding = append(funding, FundingSource{
			Position:        payouts[i].Position,
			ReductionAmount: shaveAmount,
		})
	}

	return funding, adjusted, nil
}

// selectBracket finds the payout bracket matching the given entry count.
func selectBracket(brackets []template.PayoutBracket, entryCount int) *template.PayoutBracket {
	for i := range brackets {
		if entryCount >= brackets[i].MinEntries && entryCount <= brackets[i].MaxEntries {
			return &brackets[i]
		}
	}
	// If entry count exceeds all brackets, use the last one
	if len(brackets) > 0 && entryCount > brackets[len(brackets)-1].MaxEntries {
		return &brackets[len(brackets)-1]
	}
	return nil
}

// loadRoundingDenomination loads the venue's rounding denomination.
func (e *Engine) loadRoundingDenomination(ctx context.Context) int64 {
	var denom int64
	err := e.db.QueryRowContext(ctx, "SELECT rounding_denomination FROM venue_settings WHERE id = 1").Scan(&denom)
	if err != nil {
		log.Printf("financial: load rounding denomination: %v (defaulting to 100)", err)
		return 100 // Default: 1.00 unit
	}
	return denom
}