package mailstore

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"time"

	pgtable "galaxy/mail/internal/adapters/postgres/jet/mail/table"
	"galaxy/mail/internal/domain/attempt"
	"galaxy/mail/internal/domain/common"
	deliverydomain "galaxy/mail/internal/domain/delivery"
	"galaxy/mail/internal/domain/idempotency"
	"galaxy/mail/internal/service/acceptgenericdelivery"
	"galaxy/mail/internal/service/listdeliveries"
	"galaxy/mail/internal/service/resenddelivery"

	pg "github.com/go-jet/jet/v2/postgres"
)

// resendIdempotencyExpiry stores the synthetic idempotency_expires_at value
// applied to resend deliveries. Resend rows do not carry a caller-supplied
// idempotency reservation; the fingerprint is stored as the empty string and
// the loadIdempotencyByScope helper treats those rows as non-idempotent —
// the expiry is therefore irrelevant in practice but must satisfy the
// `NOT NULL > created_at` invariant used by the deliveries column.
const resendIdempotencyExpiry = 100 * 365 * 24 * time.Hour

// maxIdempotencyExpiry is the fallback expiry duration used when no caller-
// supplied idempotency.Record reservation accompanies the write.
var maxIdempotencyExpiry = resendIdempotencyExpiry

// GetIdempotency loads the idempotency reservation for one (source, key)
// scope. It is shared by the auth-acceptance and generic-acceptance flows.
func (store *Store) GetIdempotency(ctx context.Context, source deliverydomain.Source, key common.IdempotencyKey) (idempotency.Record, bool, error) {
	if store == nil {
		return idempotency.Record{}, false, errors.New("get idempotency: nil store")
	}
	operationCtx, cancel, err := store.operationContext(ctx, "get idempotency")
	if err != nil {
		return idempotency.Record{}, false, err
	}
	defer cancel()

	record, ok, err := loadIdempotencyByScope(operationCtx, store.db, source, key)
	if err != nil {
		return idempotency.Record{}, false, fmt.Errorf("get idempotency: %w", err)
	}
	return record, ok, nil
}

// GetDeadLetter loads the dead_letters row for deliveryID when one exists.
func (store *Store) GetDeadLetter(ctx context.Context, deliveryID common.DeliveryID) (deliverydomain.DeadLetterEntry, bool, error) {
	if store == nil {
		return deliverydomain.DeadLetterEntry{}, false, errors.New("get dead-letter: nil store")
	}
	operationCtx, cancel, err := store.operationContext(ctx, "get dead-letter")
	if err != nil {
		return deliverydomain.DeadLetterEntry{}, false, err
	}
	defer cancel()

	entry, ok, err := loadDeadLetter(operationCtx, store.db, deliveryID)
	if err != nil {
		return deliverydomain.DeadLetterEntry{}, false, fmt.Errorf("get dead-letter: %w", err)
	}
	return entry, ok, nil
}

// GetDeliveryPayload returns the raw attachment payload bundle for deliveryID
// when one exists.
func (store *Store) GetDeliveryPayload(ctx context.Context, deliveryID common.DeliveryID) (acceptgenericdelivery.DeliveryPayload, bool, error) {
	if store == nil {
		return acceptgenericdelivery.DeliveryPayload{}, false, errors.New("get delivery payload: nil store")
	}
	operationCtx, cancel, err := store.operationContext(ctx, "get delivery payload")
	if err != nil {
		return acceptgenericdelivery.DeliveryPayload{}, false, err
	}
	defer cancel()

	encoded, ok, err := loadDeliveryPayload(operationCtx, store.db, deliveryID)
	if err != nil {
		return acceptgenericdelivery.DeliveryPayload{}, false, fmt.Errorf("get delivery payload: %w", err)
	}
	if !ok {
		return acceptgenericdelivery.DeliveryPayload{}, false, nil
	}
	payload, err := unmarshalDeliveryPayload(deliveryID, encoded)
	if err != nil {
		return acceptgenericdelivery.DeliveryPayload{}, false, fmt.Errorf("get delivery payload: %w", err)
	}
	return payload, true, nil
}

// ListAttempts loads exactly expectedCount attempts in attempt_no ASC order
// for deliveryID. A gap in the stored sequence surfaces as an error so
// operator reads fail closed on durable-state corruption.
func (store *Store) ListAttempts(ctx context.Context, deliveryID common.DeliveryID, expectedCount int) ([]attempt.Attempt, error) {
	if store == nil {
		return nil, errors.New("list attempts: nil store")
	}
	if expectedCount < 0 {
		return nil, errors.New("list attempts: negative expected count")
	}
	if expectedCount == 0 {
		return []attempt.Attempt{}, nil
	}
	if err := deliveryID.Validate(); err != nil {
		return nil, fmt.Errorf("list attempts: %w", err)
	}
	operationCtx, cancel, err := store.operationContext(ctx, "list attempts")
	if err != nil {
		return nil, err
	}
	defer cancel()

	out, err := loadAttempts(operationCtx, store.db, deliveryID, expectedCount)
	if err != nil {
		return nil, fmt.Errorf("list attempts: %w", err)
	}
	return out, nil
}

// List returns one filtered ordered page of delivery records keyed by
// (created_at DESC, delivery_id DESC). Filters compose into SQL WHERE
// clauses — every supported filter is index-friendly.
func (store *Store) List(ctx context.Context, input listdeliveries.Input) (listdeliveries.Result, error) {
	if store == nil {
		return listdeliveries.Result{}, errors.New("list deliveries: nil store")
	}
	if err := input.Validate(); err != nil {
		return listdeliveries.Result{}, fmt.Errorf("list deliveries: %w", err)
	}
	limit := input.Limit
	if limit <= 0 {
		limit = listdeliveries.DefaultLimit
	}

	operationCtx, cancel, err := store.operationContext(ctx, "list deliveries")
	if err != nil {
		return listdeliveries.Result{}, err
	}
	defer cancel()

	if input.Cursor != nil {
		cursorStmt := pg.SELECT(pgtable.Deliveries.CreatedAt).
			FROM(pgtable.Deliveries).
			WHERE(pgtable.Deliveries.DeliveryID.EQ(pg.String(input.Cursor.DeliveryID.String())))
		cursorQuery, cursorArgs := cursorStmt.Sql()
		row := store.db.QueryRowContext(operationCtx, cursorQuery, cursorArgs...)
		var createdAt sql.NullTime
		if err := row.Scan(&createdAt); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return listdeliveries.Result{}, listdeliveries.ErrInvalidCursor
			}
			return listdeliveries.Result{}, fmt.Errorf("list deliveries: validate cursor: %w", err)
		}
		if !createdAt.Valid || !createdAt.Time.UTC().Equal(input.Cursor.CreatedAt.UTC()) {
			return listdeliveries.Result{}, listdeliveries.ErrInvalidCursor
		}
	}

	conditions := make([]pg.BoolExpression, 0, 8)

	if input.Cursor != nil {
		cursorCreatedAt := pg.TimestampzT(input.Cursor.CreatedAt.UTC())
		cursorID := pg.String(input.Cursor.DeliveryID.String())
		// (created_at, delivery_id) < (cursorCreatedAt, cursorID) expressed as
		// the equivalent OR/AND expansion since jet has no row-comparison
		// builder.
		conditions = append(conditions, pg.OR(
			pgtable.Deliveries.CreatedAt.LT(cursorCreatedAt),
			pg.AND(
				pgtable.Deliveries.CreatedAt.EQ(cursorCreatedAt),
				pgtable.Deliveries.DeliveryID.LT(cursorID),
			),
		))
	}
	if input.Filters.Status != "" {
		conditions = append(conditions, pgtable.Deliveries.Status.EQ(pg.String(string(input.Filters.Status))))
	}
	if input.Filters.Source != "" {
		conditions = append(conditions, pgtable.Deliveries.Source.EQ(pg.String(string(input.Filters.Source))))
	}
	if !input.Filters.TemplateID.IsZero() {
		conditions = append(conditions, pgtable.Deliveries.TemplateID.EQ(pg.String(input.Filters.TemplateID.String())))
	}
	if !input.Filters.IdempotencyKey.IsZero() {
		conditions = append(conditions, pgtable.Deliveries.IdempotencyKey.EQ(pg.String(input.Filters.IdempotencyKey.String())))
	}
	if input.Filters.FromCreatedAt != nil {
		conditions = append(conditions, pgtable.Deliveries.CreatedAt.GT_EQ(pg.TimestampzT(input.Filters.FromCreatedAt.UTC())))
	}
	if input.Filters.ToCreatedAt != nil {
		conditions = append(conditions, pgtable.Deliveries.CreatedAt.LT_EQ(pg.TimestampzT(input.Filters.ToCreatedAt.UTC())))
	}
	if !input.Filters.Recipient.IsZero() {
		recipientSub := pg.SELECT(pgtable.DeliveryRecipients.DeliveryID).
			FROM(pgtable.DeliveryRecipients).
			WHERE(pg.AND(
				pgtable.DeliveryRecipients.Kind.NOT_EQ(pg.String(recipientKindReplyTo)),
				pg.LOWER(pgtable.DeliveryRecipients.Email).EQ(pg.LOWER(pg.String(input.Filters.Recipient.String()))),
			))
		conditions = append(conditions, pgtable.Deliveries.DeliveryID.IN(recipientSub))
	}

	stmt := pg.SELECT(deliverySelectColumns).
		FROM(pgtable.Deliveries)

	if len(conditions) > 0 {
		stmt = stmt.WHERE(pg.AND(conditions...))
	}
	stmt = stmt.
		ORDER_BY(pgtable.Deliveries.CreatedAt.DESC(), pgtable.Deliveries.DeliveryID.DESC()).
		LIMIT(int64(limit + 1))

	query, args := stmt.Sql()
	rows, err := store.db.QueryContext(operationCtx, query, args...)
	if err != nil {
		return listdeliveries.Result{}, fmt.Errorf("list deliveries: %w", err)
	}
	defer rows.Close()

	items := make([]deliverydomain.Delivery, 0, limit+1)
	for rows.Next() {
		record, _, err := scanDelivery(rows)
		if err != nil {
			return listdeliveries.Result{}, fmt.Errorf("list deliveries: scan: %w", err)
		}
		envelope, err := loadEnvelope(operationCtx, store.db, record.DeliveryID)
		if err != nil {
			return listdeliveries.Result{}, fmt.Errorf("list deliveries: load envelope: %w", err)
		}
		record.Envelope = envelope
		items = append(items, record)
	}
	if err := rows.Err(); err != nil {
		return listdeliveries.Result{}, fmt.Errorf("list deliveries: %w", err)
	}

	result := listdeliveries.Result{}
	if len(items) > limit {
		next := listdeliveries.Cursor{
			CreatedAt:  items[limit-1].CreatedAt.UTC(),
			DeliveryID: items[limit-1].DeliveryID,
		}
		result.NextCursor = &next
		items = items[:limit]
	}
	result.Items = items
	return result, nil
}

// CreateResend writes the cloned delivery, its first attempt, and the
// optional cloned payload bundle inside one transaction. Resend deliveries
// share the (source, idempotency_key) UNIQUE constraint, so a duplicate clone
// surfaces as a generic acceptance conflict — but the resend service
// generates fresh idempotency keys, so a conflict here always indicates a
// caller bug rather than user-replay.
func (store *Store) CreateResend(ctx context.Context, input resenddelivery.CreateResendInput) error {
	if store == nil {
		return errors.New("create resend: nil store")
	}
	if ctx == nil {
		return errors.New("create resend: nil context")
	}
	if err := input.Validate(); err != nil {
		return fmt.Errorf("create resend: %w", err)
	}

	return store.withTx(ctx, "create resend", func(ctx context.Context, tx *sql.Tx) error {
		// Use the delivery's own UpdatedAt as a deterministic finite expiry —
		// the resend has no caller-supplied idempotency.Record reservation.
		fallbackExpiresAt := input.Delivery.CreatedAt.Add(maxIdempotencyExpiry)
		first := input.FirstAttempt
		if err := insertDelivery(ctx, tx, input.Delivery, idempotency.Record{}, fallbackExpiresAt, &first); err != nil {
			if isUniqueViolation(err) {
				return fmt.Errorf("create resend: %w", err)
			}
			return fmt.Errorf("create resend: insert delivery: %w", err)
		}
		if err := insertAttempt(ctx, tx, input.FirstAttempt); err != nil {
			return fmt.Errorf("create resend: insert first attempt: %w", err)
		}
		if input.DeliveryPayload != nil {
			payload, err := marshalDeliveryPayload(*input.DeliveryPayload)
			if err != nil {
				return fmt.Errorf("create resend: %w", err)
			}
			payloadStmt := pgtable.DeliveryPayloads.INSERT(
				pgtable.DeliveryPayloads.DeliveryID,
				pgtable.DeliveryPayloads.Payload,
			).VALUES(
				input.Delivery.DeliveryID.String(),
				payload,
			)
			payloadQuery, payloadArgs := payloadStmt.Sql()
			if _, err := tx.ExecContext(ctx, payloadQuery, payloadArgs...); err != nil {
				return fmt.Errorf("create resend: insert delivery payload: %w", err)
			}
		}
		return nil
	})
}