package billing

import (
	"context"
	"errors"
	"fmt"
	"math"
	"strings"

	"github.com/jackc/pgx/v5"
)

func (s *Service) ListAccounts(ctx context.Context, tenantID string) ([]Account, error) {
	query := `
		SELECT t.id::text, t.name, COALESCE(w.currency, $1), COALESCE(w.balance_micros, 0),
		       COALESCE(w.reserved_micros, 0), COALESCE(w.balance_micros - w.reserved_micros, 0),
		       COALESCE(w.updated_at, t.created_at)
		FROM tenants t LEFT JOIN tenant_wallets w ON w.tenant_id = t.id`
	args := []any{s.currency}
	if strings.TrimSpace(tenantID) != "" {
		query += ` WHERE t.id=$2`
		args = append(args, tenantID)
	}
	query += ` ORDER BY t.name`
	rows, err := s.db.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("query billing accounts: %w", err)
	}
	defer rows.Close()
	result := make([]Account, 0)
	for rows.Next() {
		var item Account
		if err := rows.Scan(&item.TenantID, &item.TenantName, &item.Currency, &item.BalanceMicros,
			&item.ReservedMicros, &item.AvailableMicros, &item.UpdatedAt); err != nil {
			return nil, fmt.Errorf("scan billing account: %w", err)
		}
		result = append(result, item)
	}
	return result, rows.Err()
}

func (s *Service) ListLedger(ctx context.Context, tenantID string, limit int) ([]LedgerEntry, error) {
	if limit < 1 || limit > 500 {
		limit = 200
	}
	query := `
		SELECT id::text, tenant_id::text, COALESCE(project_id::text, ''), currency, amount_micros,
		       balance_after_micros, kind, source_type, source_id, description, created_at
		FROM billing_ledger`
	args := []any{}
	if strings.TrimSpace(tenantID) != "" {
		query += ` WHERE tenant_id = $1 ORDER BY created_at DESC LIMIT $2`
		args = append(args, tenantID, limit)
	} else {
		query += ` ORDER BY created_at DESC LIMIT $1`
		args = append(args, limit)
	}
	rows, err := s.db.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("query billing ledger: %w", err)
	}
	defer rows.Close()
	result := make([]LedgerEntry, 0)
	for rows.Next() {
		var item LedgerEntry
		if err := rows.Scan(&item.ID, &item.TenantID, &item.ProjectID, &item.Currency, &item.AmountMicros,
			&item.BalanceAfterMicros, &item.Kind, &item.SourceType, &item.SourceID,
			&item.Description, &item.CreatedAt); err != nil {
			return nil, fmt.Errorf("scan billing ledger: %w", err)
		}
		result = append(result, item)
	}
	return result, rows.Err()
}

func (s *Service) ListTopUpOrders(ctx context.Context, tenantID string, limit int) ([]TopUpOrder, error) {
	if limit < 1 || limit > 200 {
		limit = 50
	}
	query := `SELECT id::text,tenant_id::text,amount_minor,amount_micros,currency,status,trigger_type,
		COALESCE(stripe_session_id,''),COALESCE(checkout_url,''),created_at,paid_at,
		COALESCE(stripe_customer_id,''),COALESCE(stripe_payment_intent_id,''),COALESCE(stripe_charge_id,''),
		COALESCE(stripe_invoice_id,''),COALESCE(invoice_url,''),COALESCE(invoice_pdf_url,''),COALESCE(receipt_url,''),
		refunded_micros,disputed_micros,reconciliation_status,reconciled_at,reconciliation_error FROM topup_orders`
	args := []any{}
	if strings.TrimSpace(tenantID) != "" {
		query += ` WHERE tenant_id=$1 ORDER BY created_at DESC LIMIT $2`
		args = []any{tenantID, limit}
	} else {
		query += ` ORDER BY created_at DESC LIMIT $1`
		args = []any{limit}
	}
	rows, err := s.db.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("query top-up orders: %w", err)
	}
	defer rows.Close()
	result := make([]TopUpOrder, 0)
	for rows.Next() {
		var item TopUpOrder
		if err := rows.Scan(&item.ID, &item.TenantID, &item.AmountMinor, &item.AmountMicros, &item.Currency, &item.Status, &item.TriggerType,
			&item.StripeSessionID, &item.CheckoutURL, &item.CreatedAt, &item.PaidAt, &item.StripeCustomerID,
			&item.StripePaymentIntentID, &item.StripeChargeID, &item.StripeInvoiceID, &item.InvoiceURL,
			&item.InvoicePDFURL, &item.ReceiptURL, &item.RefundedMicros, &item.DisputedMicros,
			&item.ReconciliationStatus, &item.ReconciledAt, &item.ReconciliationError); err != nil {
			return nil, err
		}
		result = append(result, item)
	}
	return result, rows.Err()
}

func (s *Service) GetTopUpOrder(ctx context.Context, tenantID, orderID string) (TopUpOrder, error) {
	var result TopUpOrder
	query := `SELECT id::text,tenant_id::text,amount_minor,amount_micros,currency,status,trigger_type,
		COALESCE(stripe_session_id,''),COALESCE(checkout_url,''),created_at,paid_at,
		COALESCE(stripe_customer_id,''),COALESCE(stripe_payment_intent_id,''),COALESCE(stripe_charge_id,''),
		COALESCE(stripe_invoice_id,''),COALESCE(invoice_url,''),COALESCE(invoice_pdf_url,''),COALESCE(receipt_url,''),
		refunded_micros,disputed_micros,reconciliation_status,reconciled_at,reconciliation_error FROM topup_orders WHERE id=$1`
	args := []any{orderID}
	if strings.TrimSpace(tenantID) != "" {
		query += ` AND tenant_id=$2`
		args = append(args, tenantID)
	}
	err := s.db.QueryRow(ctx, query, args...).Scan(&result.ID, &result.TenantID, &result.AmountMinor, &result.AmountMicros,
		&result.Currency, &result.Status, &result.TriggerType, &result.StripeSessionID, &result.CheckoutURL, &result.CreatedAt, &result.PaidAt,
		&result.StripeCustomerID, &result.StripePaymentIntentID, &result.StripeChargeID, &result.StripeInvoiceID,
		&result.InvoiceURL, &result.InvoicePDFURL, &result.ReceiptURL, &result.RefundedMicros, &result.DisputedMicros,
		&result.ReconciliationStatus, &result.ReconciledAt, &result.ReconciliationError)
	if errors.Is(err, pgx.ErrNoRows) {
		return TopUpOrder{}, ErrTopUpOrderNotFound
	}
	if err != nil {
		return TopUpOrder{}, fmt.Errorf("get top-up order: %w", err)
	}
	return result, nil
}

func (s *Service) AdjustBalance(ctx context.Context, input AdjustmentInput) (LedgerEntry, error) {
	input.TenantID = strings.TrimSpace(input.TenantID)
	input.Description = normalizeDescription(input.Description)
	if input.TenantID == "" || input.AmountMicros == 0 {
		return LedgerEntry{}, ErrInvalidAmount
	}
	tx, err := s.db.BeginTx(ctx, pgx.TxOptions{IsoLevel: pgx.ReadCommitted})
	if err != nil {
		return LedgerEntry{}, fmt.Errorf("begin balance adjustment: %w", err)
	}
	defer tx.Rollback(ctx)
	if _, err := tx.Exec(ctx, `
		INSERT INTO tenant_wallets (tenant_id, currency) VALUES ($1, $2)
		ON CONFLICT (tenant_id) DO NOTHING`, input.TenantID, s.currency); err != nil {
		return LedgerEntry{}, fmt.Errorf("ensure adjustment wallet: %w", err)
	}
	var currency string
	var balance, held int64
	if err := tx.QueryRow(ctx, `SELECT currency, balance_micros, reserved_micros FROM tenant_wallets WHERE tenant_id = $1 FOR UPDATE`, input.TenantID).Scan(&currency, &balance, &held); err != nil {
		return LedgerEntry{}, fmt.Errorf("lock adjustment wallet: %w", err)
	}
	if currency != s.currency {
		return LedgerEntry{}, fmt.Errorf("tenant wallet currency %s does not match %s", currency, s.currency)
	}
	if input.AmountMicros > 0 && balance > math.MaxInt64-input.AmountMicros {
		return LedgerEntry{}, ErrInvalidAmount
	}
	newBalance := balance + input.AmountMicros
	if newBalance < held || newBalance < 0 {
		return LedgerEntry{}, ErrInsufficientBalance
	}
	if _, err := tx.Exec(ctx, `UPDATE tenant_wallets SET balance_micros = $2, updated_at = now() WHERE tenant_id = $1`, input.TenantID, newBalance); err != nil {
		return LedgerEntry{}, fmt.Errorf("apply balance adjustment: %w", err)
	}
	sourceID := "adj_" + randomHex(16)
	var result LedgerEntry
	err = tx.QueryRow(ctx, `
		INSERT INTO billing_ledger (tenant_id, currency, amount_micros, balance_after_micros, kind, source_type, source_id, description)
		VALUES ($1,$2,$3,$4,'adjustment','admin',$5,$6)
		RETURNING id::text, tenant_id::text, '', currency, amount_micros, balance_after_micros,
		          kind, source_type, source_id, description, created_at`,
		input.TenantID, s.currency, input.AmountMicros, newBalance, sourceID, input.Description,
	).Scan(&result.ID, &result.TenantID, &result.ProjectID, &result.Currency, &result.AmountMicros,
		&result.BalanceAfterMicros, &result.Kind, &result.SourceType, &result.SourceID,
		&result.Description, &result.CreatedAt)
	if err != nil {
		return LedgerEntry{}, fmt.Errorf("write adjustment ledger entry: %w", err)
	}
	if err := tx.Commit(ctx); err != nil {
		return LedgerEntry{}, fmt.Errorf("commit balance adjustment: %w", err)
	}
	return result, nil
}

// ReleaseUnmeteredReservation is an audited operational escape hatch for a
// fail-closed success that cannot be reconciled. It never invents usage or
// changes wallet balance; it only returns the existing hold to availability.
func (s *Service) ReleaseUnmeteredReservation(ctx context.Context, tenantID, requestID string, input ReleaseReservationInput, actor ResolutionActor) (ReservationRelease, error) {
	tenantID = strings.TrimSpace(tenantID)
	requestID = strings.TrimSpace(requestID)
	reason := normalizeDescription(input.Reason)
	if tenantID == "" || requestID == "" || reason == "" || actor.ID == "" || actor.Type == "" {
		return ReservationRelease{}, fmt.Errorf("%w: tenant, request, reason, and actor are required", ErrReservationNotReleasable)
	}
	tx, err := s.db.BeginTx(ctx, pgx.TxOptions{IsoLevel: pgx.ReadCommitted})
	if err != nil {
		return ReservationRelease{}, fmt.Errorf("begin reservation release: %w", err)
	}
	defer tx.Rollback(ctx)
	var result ReservationRelease
	var projectID, currency, status string
	if err := tx.QueryRow(ctx, `SELECT request_id,tenant_id::text,project_id::text,currency,reserved_micros,status
		FROM billing_reservations WHERE request_id=$1 AND tenant_id=$2 FOR UPDATE`, requestID, tenantID).Scan(
		&result.RequestID, &result.TenantID, &projectID, &currency, &result.ReservedMicros, &status); errors.Is(err, pgx.ErrNoRows) {
		return ReservationRelease{}, ErrReservationNotReleasable
	} else if err != nil {
		return ReservationRelease{}, fmt.Errorf("lock reservation for release: %w", err)
	}
	if status == "released" {
		var evidenceExists bool
		if err := tx.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM billing_ledger
			WHERE source_type='unmetered_reservation' AND source_id=$1)`, requestID).Scan(&evidenceExists); err != nil {
			return ReservationRelease{}, fmt.Errorf("read reservation release evidence: %w", err)
		}
		if !evidenceExists {
			return ReservationRelease{}, fmt.Errorf("%w: reservation was released by normal settlement", ErrReservationNotReleasable)
		}
		if err := tx.QueryRow(ctx, `SELECT COALESCE(settled_at,created_at) FROM billing_reservations WHERE request_id=$1`, requestID).Scan(&result.ReleasedAt); err != nil {
			return ReservationRelease{}, err
		}
		result.Status = status
		return result, tx.Commit(ctx)
	}
	if status != "metering_failed" {
		return ReservationRelease{}, fmt.Errorf("%w: reservation status is %s", ErrReservationNotReleasable, status)
	}
	var balance, held int64
	if err := tx.QueryRow(ctx, `SELECT balance_micros,reserved_micros FROM tenant_wallets WHERE tenant_id=$1 FOR UPDATE`, tenantID).Scan(&balance, &held); err != nil {
		return ReservationRelease{}, fmt.Errorf("lock wallet for reservation release: %w", err)
	}
	if result.ReservedMicros > held {
		return ReservationRelease{}, errors.New("wallet reservation invariant violated during release")
	}
	if _, err := tx.Exec(ctx, `UPDATE tenant_wallets SET reserved_micros=reserved_micros-$2,updated_at=now() WHERE tenant_id=$1`, tenantID, result.ReservedMicros); err != nil {
		return ReservationRelease{}, fmt.Errorf("release wallet hold: %w", err)
	}
	if err := tx.QueryRow(ctx, `UPDATE billing_reservations SET status='released',settled_at=now()
		WHERE request_id=$1 RETURNING status,settled_at`, requestID).Scan(&result.Status, &result.ReleasedAt); err != nil {
		return ReservationRelease{}, fmt.Errorf("mark reservation released: %w", err)
	}
	command, err := tx.Exec(ctx, `UPDATE usage_events SET metering_status='released_unmetered'
		WHERE request_id=$1 AND tenant_id=$2 AND metering_status='missing' AND usage_reported=FALSE`, requestID, tenantID)
	if err != nil {
		return ReservationRelease{}, fmt.Errorf("mark unmetered usage resolved: %w", err)
	}
	if command.RowsAffected() != 1 {
		return ReservationRelease{}, errors.New("unmetered usage invariant violated during release")
	}
	description := fmt.Sprintf("Unmetered reservation released by %s %s: %s", actor.Type, actor.ID, reason)
	if _, err := tx.Exec(ctx, `INSERT INTO billing_ledger
		(tenant_id,project_id,currency,amount_micros,balance_after_micros,kind,source_type,source_id,description)
		VALUES ($1,$2,$3,0,$4,'release','unmetered_reservation',$5,$6)
		ON CONFLICT (source_type,source_id) DO NOTHING`, tenantID, projectID, currency, balance, requestID, description); err != nil {
		return ReservationRelease{}, fmt.Errorf("write reservation release evidence: %w", err)
	}
	if err := tx.Commit(ctx); err != nil {
		return ReservationRelease{}, fmt.Errorf("commit reservation release: %w", err)
	}
	return result, nil
}

func (s *Service) createTopUpOrder(ctx context.Context, input CheckoutInput) (string, int64, error) {
	if !s.stripeEnabled {
		return "", 0, ErrStripeDisabled
	}
	if strings.TrimSpace(input.TenantID) == "" || input.AmountMinor < s.minTopUpMinor || input.AmountMinor > s.maxTopUpMinor {
		return "", 0, ErrInvalidAmount
	}
	amountMicros, err := minorToMicros(s.currency, input.AmountMinor)
	if err != nil {
		return "", 0, err
	}
	var orderID string
	err = s.db.QueryRow(ctx, `
		INSERT INTO topup_orders (tenant_id, amount_minor, amount_micros, currency)
		VALUES ($1,$2,$3,$4) RETURNING id::text`, input.TenantID, input.AmountMinor, amountMicros, s.currency,
	).Scan(&orderID)
	if err != nil {
		return "", 0, fmt.Errorf("create top-up order: %w", err)
	}
	return orderID, amountMicros, nil
}

func minorToMicros(currency string, amount int64) (int64, error) {
	if amount <= 0 {
		return 0, ErrInvalidAmount
	}
	factor := int64(10_000)
	switch strings.ToLower(currency) {
	case "bif", "clp", "djf", "gnf", "jpy", "kmf", "krw", "mga", "pyg", "rwf", "ugx", "vnd", "vuv", "xaf", "xof", "xpf":
		factor = 1_000_000
	case "bhd", "jod", "kwd", "omr", "tnd":
		factor = 1_000
	}
	if amount > math.MaxInt64/factor {
		return 0, ErrInvalidAmount
	}
	return amount * factor, nil
}

func isNotFound(err error) bool {
	return errors.Is(err, pgx.ErrNoRows)
}