package payments

import (
	"context"
	"errors"
	"fmt"
	"log"
	"strings"
	"time"

	"crussell/clock"
	"crussell/db"
	"crussell/internal/square"
)

// SweepStalePendingPayments resolves pending payment records that are older
// than Square's idempotency-key retention window (~24h). A pending record
// means the DB committed but the Square charge outcome is unknown; it
// normally resolves on a same-key client retry. But if the client abandoned
// the attempt, the record stays pending forever — and retrying it after the
// key expires would ISSUE A SECOND CHARGE (Square no longer dedups). Failing
// stale pendings closes that double-charge window: a late retry finds a
// 'failed' record and stops instead of charging again.
//
// Before failing a row, the sweep reconciles it against Square: a
// genuinely-charged row (Square success, DB post-charge failure) with a
// square_payment_id is rescued to 'completed' instead of being swept to
// 'failed' with no automatic resolution — the money would otherwise be lost
// in limbo (MINOR-R3). Reconciliation is deliberately minimal: status +
// updated_at only, no split/VAT recomputation (that is the handler's job; the
// row is >24h stale and this is a reconciliation rescue).
//
// Only online/till card payments can be pending — cash/giftcard/on_the_house
// are committed synchronously and never enter this state. Both the payments
// table and till_sales carry pending card-sale rows and are swept here.
const stalePendingPaymentAge = 24 * time.Hour

func SweepStalePendingPayments(ctx context.Context) (int, error) {
	cutoff := clock.Now().Add(-stalePendingPaymentAge)

	payCount, payCompleted, err := sweepStaleRows(ctx, "payments", cutoff)
	if err != nil {
		return 0, err
	}

	// till_sales rows for card payments (stored as 'online_square' or
	// 'in_person_card' in the payment_method enum — saved_card/online_square/
	// card_machine requests all persist as one of those) can also be pending.
	// Sweep them too — a lost-response till sale would otherwise stay pending
	// and a retry after key retention would reuse the stored key → Square sees
	// an expired key → second charge (R3). Cash / on_the_house are committed
	// synchronously and never pending.
	tillCount, tillCompleted, err := sweepStaleRows(ctx, "till_sales", cutoff)
	if err != nil {
		return 0, err
	}

	total := payCount + tillCount
	if total > 0 {
		log.Printf("[SWEEP] Resolved %d stale pending payments (%d payments, %d till sales) older than %s — late retries will be rejected, preventing a second Square charge; %d reconciled to completed against Square (%d payments, %d till sales)", total, payCount, tillCount, stalePendingPaymentAge, payCompleted+tillCompleted, payCompleted, tillCompleted)
	}
	if payCount > 0 {
		log.Printf("CRITICAL: %d pending payments swept to failed may have been charged at Square with a lost response — manual reconciliation required before refunding/charging", payCount-payCompleted)
	}
	if tillCount > 0 {
		log.Printf("CRITICAL: %d pending till sales swept to failed may have been charged at Square with a lost response — manual reconciliation required", tillCount-tillCompleted)
	}
	return total, nil
}

// staleRow is one stale pending row read by the sweep so it can reconcile
// rows that carry a Square reference BEFORE failing them.
type staleRow struct {
	ID              string
	SquarePaymentID string
}

// sweepStaleRows resolves the stale pending rows of one table. Rows with a
// square_payment_id are reconciled at Square first (COMPLETED → 'completed',
// anything else → 'failed' exactly as the legacy bulk UPDATE did); rows
// without one cannot be reconciled and are failed directly. Returns the total
// rows resolved and how many were rescued to 'completed'.
func sweepStaleRows(ctx context.Context, table string, cutoff time.Time) (resolved int, completed int, err error) {
	switch table {
	case "payments", "till_sales":
	default:
		return 0, 0, fmt.Errorf("sweep: unknown stale table %q", table)
	}
	// The legacy till_sales sweep only touched card methods — cash and
	// on_the_house are committed synchronously and never pending, but keep the
	// predicate so behaviour is byte-identical for any unexpected row.
	methodFilter := ""
	if table == "till_sales" {
		methodFilter = ` AND payment_method IN ('online_square', 'in_person_card')`
	}
	rows, err := db.Conn.Query(ctx, `
		SELECT id, COALESCE(square_payment_id, '')
		FROM `+table+`
		WHERE status = 'pending' AND created_at < $1`+methodFilter+`
	`, cutoff)
	if err != nil {
		return 0, 0, err
	}
	var stale []staleRow
	for rows.Next() {
		var r staleRow
		if err := rows.Scan(&r.ID, &r.SquarePaymentID); err != nil {
			log.Printf("Failed to scan stale pending row from %s: %v", table, err)
			continue
		}
		stale = append(stale, r)
	}
	rows.Close()

	for _, r := range stale {
		if r.SquarePaymentID != "" {
			switch reconcileStalePaymentAtSquare(ctx, table, r.SquarePaymentID) {
			case staleReconcileCompleted:
				if tag, upErr := db.Conn.Exec(ctx, `
					UPDATE `+table+` SET status = 'completed', updated_at = NOW()
					WHERE id = $1 AND status = 'pending'
				`, r.ID); upErr != nil {
					log.Printf("Failed to rescue stale pending row %s to completed: %v", r.ID, upErr)
				} else if n := int(tag.RowsAffected()); n > 0 {
					resolved++
					completed++
				}
				continue
			case staleReconcileLeavePending:
				// Square's answer was ambiguous (transport/5xx) — the charge
				// may still be in flight at Square. Do NOT touch the row: the
				// next sweep run reconciles it again, and a same-key retry
				// must still be able to reuse the pending row if the charge
				// actually completed.
				log.Printf("Stale pending %s row %s left pending (Square reconcile ambiguous) — will retry next sweep", table, r.ID)
				continue
			}
			// staleReconcileDefinitivelyFailed falls through to the fail path.
		}
		if tag, upErr := db.Conn.Exec(ctx, `
			UPDATE `+table+` SET status = 'failed', updated_at = NOW()
			WHERE id = $1 AND status = 'pending'
		`, r.ID); upErr != nil {
			log.Printf("Failed to mark stale pending row %s failed: %v", r.ID, upErr)
		} else if n := int(tag.RowsAffected()); n > 0 {
			resolved++
		}
	}
	return resolved, completed, nil
}

// staleReconcileResult is the tri-state outcome of reconciling one stale
// pending row against Square. Only a definitively-resolved outcome touches the
// row: an ambiguous answer (transport error / 5xx) leaves it pending so a
// same-key retry can still reuse it if the charge actually completed.
type staleReconcileResult int

const (
	// staleReconcileLeavePending — Square's answer was ambiguous; the row stays
	// pending for the next sweep run.
	staleReconcileLeavePending staleReconcileResult = iota
	// staleReconcileCompleted — Square confirms the charge completed; rescue
	// the row to 'completed'.
	staleReconcileCompleted
	// staleReconcileDefinitivelyFailed — Square proves the charge never
	// completed (payment not found / non-completed status); mark the row
	// 'failed' exactly as the legacy bulk sweep did.
	staleReconcileDefinitivelyFailed
)

// reconcileStalePaymentAtSquare asks Square for the authoritative status of a
// stale pending charge and returns the tri-state result. A COMPLETED payment
// rescues the row to 'completed'; a NOT_FOUND error or any non-COMPLETED status
// proves the charge never completed and fails the row as the legacy bulk sweep
// did. Any OTHER error (transport / 5xx / ambiguous) is NOT treated as a
// definitive failure — the charge may still have completed at Square, and
// marking the row failed would close the double-charge window (blocking a
// same-key retry with a 409) even though the money moved. Such rows stay
// pending for a later run.
func reconcileStalePaymentAtSquare(ctx context.Context, table, squarePaymentID string) staleReconcileResult {
	pr, err := SquareClient.GetPayment(ctx, squarePaymentID)
	if err != nil {
		if squarePaymentErrorIsNotFound(err) {
			log.Printf("Stale pending %s reconcile: Square payment %s not found (%v) — marking failed as the legacy sweep would", table, squarePaymentID, err)
			return staleReconcileDefinitivelyFailed
		}
		log.Printf("Stale pending %s reconcile for Square payment %s hit an ambiguous error (%v) — leaving pending for a later sweep run", table, squarePaymentID, err)
		return staleReconcileLeavePending
	}
	if pr.Status != "COMPLETED" {
		log.Printf("Stale pending %s is %q at Square — marking failed", table, pr.Status)
		return staleReconcileDefinitivelyFailed
	}
	return staleReconcileCompleted
}

// squarePaymentErrorIsNotFound reports whether a GetPayment error proves the
// payment does not exist at Square. The structured Square error code is the
// primary check (square.ErrorCode); the message fallback also covers the dev
// mock (a plain "payment not found" error) and a non-JSON 404 response.
func squarePaymentErrorIsNotFound(err error) bool {
	if err == nil {
		return false
	}
	if square.ErrorCode(err) == "NOT_FOUND" {
		return true
	}
	msg := strings.ToUpper(err.Error())
	return strings.Contains(msg, "NOT_FOUND") ||
		strings.Contains(msg, "NOT FOUND") ||
		strings.Contains(msg, "HTTP 404")
}

// staleTerminalCheckoutAge is how old a still-pending terminal checkout must
// be before the sweep cancels it. Terminal checkouts normally complete within
// minutes; an hour is far past any legitimate card-reader interaction while
// still short enough that a completed charge can never be misread as stale.
const staleTerminalCheckoutAge = 1 * time.Hour

// SweepStaleTerminalCheckouts cancels terminal (card-machine) checkouts that
// are still PENDING/IN_PROGRESS long after they were created, so the terminal
// stops waiting on a customer who walked away. A checkout created by
// CreateTerminalPayment / CreateTillSale that is never polled would otherwise
// sit live at Square indefinitely; if it later completes it is an invisible,
// untracked charge.
//
// Two tables track live checkout IDs and are both swept:
//   - terminal_checkouts: booking terminal checkouts created by
//     CreateTerminalPayment. PENDING/IN_PROGRESS rows older than the cutoff
//     are resolved at Square first: a checkout still waiting at Square is
//     cancelled and re-checked once — if it completed during the cancel window
//     the row is marked 'completed' (the poll handler records the payment),
//     otherwise 'failed'; a COMPLETED checkout releases the in-flight guard
//     (the poll handler records the payment); a definitively
//     cancelled/expired checkout is marked 'failed'; an ambiguous status is
//     left for a later run.
//   - till_sales.square_checkout_id: card-machine till sales. A checkout still
//     waiting at Square is cancelled and the sale marked 'failed' (the
//     payment_status enum has no 'cancelled' value, and 'failed' is the same
//     terminal state the stale-pending sweep uses, blocking the till
//     pending-retry path); a checkout that completed during the cancel window
//     leaves the sale pending for the poll handler to record.
//
// Each row is checked at Square FIRST and only cancelled when the checkout is
// provably still waiting (ErrCheckoutPending): a COMPLETED checkout is never
// cancelled, and a checkout whose status is unknown (transport error) is left
// alone for a later run. After a cancel the checkout is re-checked once — the
// customer may have completed the payment in the cancel window, in which case
// the row is resolved to 'completed' rather than 'failed'.
func SweepStaleTerminalCheckouts(ctx context.Context) (int, error) {
	cutoff := clock.Now().Add(-staleTerminalCheckoutAge)

	var pending []staleTerminalCheckoutRow

	// Booking terminal checkouts (CreateTerminalPayment) live in the
	// terminal_checkouts table. A stale PENDING/IN_PROGRESS row means the
	// checkout is still live at Square (or was left after a crash / lost poll).
	rows, err := db.Conn.Query(ctx, `
		SELECT 'terminal_checkout', checkout_id, checkout_id
		FROM terminal_checkouts
		WHERE status IN ('PENDING', 'IN_PROGRESS')
		  AND created_at < $1
	`, cutoff)
	if err != nil {
		return 0, err
	}
	for rows.Next() {
		var r staleTerminalCheckoutRow
		if err := rows.Scan(&r.Kind, &r.RowID, &r.CheckoutID); err != nil {
			log.Printf("Failed to scan stale terminal checkout row: %v", err)
			continue
		}
		pending = append(pending, r)
	}
	rows.Close()

	// Till-sale card-machine checkouts are tracked on the till_sales row.
	rows, err = db.Conn.Query(ctx, `
		SELECT 'till_sale', id, square_checkout_id
		FROM till_sales
		WHERE status = 'pending' AND square_checkout_id IS NOT NULL
		  AND created_at < $1
	`, cutoff)
	if err != nil {
		return 0, err
	}
	for rows.Next() {
		var r staleTerminalCheckoutRow
		if err := rows.Scan(&r.Kind, &r.RowID, &r.CheckoutID); err != nil {
			log.Printf("Failed to scan stale terminal checkout row: %v", err)
			continue
		}
		pending = append(pending, r)
	}
	rows.Close()

	resolved := 0
	for _, r := range pending {
		// A provisional (pre-Square) terminal_checkouts row carries a synthetic
		// "tmp-" checkout_id (or an empty one) — no checkout was ever created
		// at Square for it, so it is PROVABLY not live (R3). Resolve it to
		// failed directly without a Square round-trip; a hard crash between the
		// row insert and the Square CreateCheckout call is the only way one
		// exists.
		if r.CheckoutID == "" || strings.HasPrefix(r.CheckoutID, "tmp-") {
			if markTerminalCheckoutRowFailed(ctx, r) {
				resolved++
			}
			log.Printf("Provisional (pre-Square) terminal checkout row %s (%s) resolved as failed — no live checkout at Square", r.RowID, r.Kind)
			continue
		}

		// Conservative status check: only cancel a checkout that is provably
		// still waiting at Square. A COMPLETED checkout must never be
		// cancelled, and an ambiguous status (network error) is left alone for
		// the next run.
		pr, gErr := SquareClient.GetCheckout(ctx, r.CheckoutID)
		switch {
		case errors.Is(gErr, square.ErrCheckoutPending):
			// Still live at the terminal — cancel it. A customer can complete
			// the payment in the small window between the GetCheckout above and
			// the cancel, so re-check once before marking the row failed: a
			// COMPLETED charge must never be recorded as failed.
			if cErr := SquareClient.CancelCheckout(ctx, r.CheckoutID); cErr != nil {
				log.Printf("Failed to cancel stale terminal checkout %s (%s %s): %v", r.CheckoutID, r.Kind, r.RowID, cErr)
				continue
			}
			recheck, rErr := SquareClient.GetCheckout(ctx, r.CheckoutID)
			switch {
			case rErr == nil && recheck.Status == "COMPLETED":
				// The customer completed the payment during the cancel window.
				// The poll handler records it — mark the row COMPLETED (or
				// leave the till sale pending) instead of failed.
				if r.Kind == "terminal_checkout" {
					if tag, upErr := db.Conn.Exec(ctx, `
						UPDATE terminal_checkouts SET status = 'COMPLETED', updated_at = NOW()
						WHERE checkout_id = $1 AND status IN ('PENDING', 'IN_PROGRESS')
					`, r.RowID); upErr != nil {
						log.Printf("Failed to mark terminal checkout %s completed after cancel re-check: %v", r.RowID, upErr)
					} else if int(tag.RowsAffected()) > 0 {
						resolved++
					}
				} else {
					log.Printf("Terminal checkout %s completed during sweep cancel — leaving sale %s pending (poll handler records it)", r.CheckoutID, r.RowID)
				}
				log.Printf("Cancelled stale terminal checkout %s (%s %s, pending >%s) but re-check shows COMPLETED — recorded as completed, payment handled by the poll handler", r.CheckoutID, r.Kind, r.RowID, staleTerminalCheckoutAge)
			case isTerminalCheckoutError(rErr) || errors.Is(rErr, square.ErrCheckoutPending):
				// The cancel landed (CANCELED / cancel-requested / expired /
				// still-reporting-pending-but-now-cancelled) — it can never
				// complete, so resolve the row to the terminal 'failed' state.
				if markTerminalCheckoutRowFailed(ctx, r) {
					resolved++
				}
				log.Printf("Cancelled stale terminal checkout %s (%s %s, pending >%s) — marked failed", r.CheckoutID, r.Kind, r.RowID, staleTerminalCheckoutAge)
			default:
				// The cancel succeeded but the re-check itself is ambiguous —
				// leave the row for a later run.
				log.Printf("Terminal checkout %s was cancelled but its re-check is ambiguous (%v) — leaving %s %s pending for a later sweep", r.CheckoutID, rErr, r.Kind, r.RowID)
			}
		case gErr == nil && pr.Status == "COMPLETED":
			if r.Kind == "terminal_checkout" {
				// The payment is recorded by the poll handler; release the
				// in-flight guard so a fresh charge can be created.
				if tag, upErr := db.Conn.Exec(ctx, `
					UPDATE terminal_checkouts SET status = 'COMPLETED', updated_at = NOW()
					WHERE checkout_id = $1 AND status IN ('PENDING', 'IN_PROGRESS')
				`, r.RowID); upErr != nil {
					log.Printf("Failed to mark terminal checkout %s completed: %v", r.RowID, upErr)
				} else if int(tag.RowsAffected()) > 0 {
					resolved++
				}
			} else {
				// The till poll handler records it — leave the sale pending.
				log.Printf("Terminal checkout %s already COMPLETED at Square — leaving sale %s pending (poll handler records it)", r.CheckoutID, r.RowID)
			}
		case isTerminalCheckoutError(gErr):
			// Definitely cancelled / cancel-requested / expired — the checkout
			// can never complete, so resolve it to the terminal 'failed' state.
			if markTerminalCheckoutRowFailed(ctx, r) {
				resolved++
			}
			log.Printf("Terminal checkout %s is definitively terminal (%v) — marked %s %s failed", r.CheckoutID, gErr, r.Kind, r.RowID)
		default:
			// Ambiguous transport/unknown status — leave for a later run.
			log.Printf("Terminal checkout %s status unknown (%v) — leaving %s %s pending for a later sweep", r.CheckoutID, gErr, r.Kind, r.RowID)
		}
	}
	return resolved, nil
}

// staleTerminalCheckoutRow is one live-checkout row the sweep reads from
// either table so it can resolve the checkout at Square before touching the
// row. Kind is "terminal_checkout" (booking, terminal_checkouts table) or
// "till_sale" (till_sales.square_checkout_id).
type staleTerminalCheckoutRow struct {
	Kind       string
	RowID      string
	CheckoutID string
}

// markTerminalCheckoutRowFailed moves one tracked row to the terminal 'failed'
// state after its checkout is cancelled or proven terminal at Square. Returns
// true when the row was updated (status was still active).
func markTerminalCheckoutRowFailed(ctx context.Context, r staleTerminalCheckoutRow) bool {
	var table, where string
	if r.Kind == "till_sale" {
		table = "till_sales"
		where = "id = $1 AND status = 'pending'"
	} else {
		table = "terminal_checkouts"
		where = "checkout_id = $1 AND status IN ('PENDING', 'IN_PROGRESS')"
	}
	tag, err := db.Conn.Exec(ctx, `
		UPDATE `+table+` SET status = 'failed', updated_at = NOW()
		WHERE `+where, r.RowID)
	if err != nil {
		log.Printf("Failed to mark %s %s failed: %v", r.Kind, r.RowID, err)
		return false
	}
	return int(tag.RowsAffected()) > 0
}

// isTerminalCheckoutError reports whether a GetCheckout error proves the
// checkout can never complete. Square's HTTP client returns ErrCheckoutPending
// for a still-live checkout and surfaces a definitively CANCELED status as a
// "square: checkout <id> is CANCELED (not COMPLETED)" error; an expired
// checkout returns a NOT_FOUND API error (the mock uses "checkout not found").
// Any other error (timeout, 5xx) leaves the money state ambiguous, so the
// checkout must stay in flight.
func isTerminalCheckoutError(err error) bool {
	if err == nil || errors.Is(err, square.ErrCheckoutPending) {
		return false
	}
	msg := strings.ToUpper(err.Error())
	return strings.Contains(msg, "CANCELED") ||
		strings.Contains(msg, "CANCEL_REQUESTED") ||
		strings.Contains(msg, "NOT_FOUND") ||
		strings.Contains(msg, "NOT FOUND")
}