package redisstate

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

	"galaxy/lobby/internal/ports"

	"github.com/redis/go-redis/v9"
)

// StreamOffsetStore provides the Redis-backed storage used for
// persisted Redis Stream consumer progress. The key per stream label is
// produced by Keyspace.StreamOffset.
type StreamOffsetStore struct {
	client *redis.Client
	keys   Keyspace
}

// NewStreamOffsetStore constructs one Redis-backed stream-offset store.
func NewStreamOffsetStore(client *redis.Client) (*StreamOffsetStore, error) {
	if client == nil {
		return nil, errors.New("new lobby stream offset store: nil redis client")
	}
	return &StreamOffsetStore{
		client: client,
		keys:   Keyspace{},
	}, nil
}

// Load returns the last processed entry id for streamLabel when one is
// stored.
func (store *StreamOffsetStore) Load(ctx context.Context, streamLabel string) (string, bool, error) {
	if store == nil || store.client == nil {
		return "", false, errors.New("load lobby stream offset: nil store")
	}
	if ctx == nil {
		return "", false, errors.New("load lobby stream offset: nil context")
	}
	if strings.TrimSpace(streamLabel) == "" {
		return "", false, errors.New("load lobby stream offset: stream label must not be empty")
	}

	value, err := store.client.Get(ctx, store.keys.StreamOffset(streamLabel)).Result()
	switch {
	case errors.Is(err, redis.Nil):
		return "", false, nil
	case err != nil:
		return "", false, fmt.Errorf("load lobby stream offset: %w", err)
	}
	return value, true, nil
}

// Save stores entryID as the new offset for streamLabel.
func (store *StreamOffsetStore) Save(ctx context.Context, streamLabel, entryID string) error {
	if store == nil || store.client == nil {
		return errors.New("save lobby stream offset: nil store")
	}
	if ctx == nil {
		return errors.New("save lobby stream offset: nil context")
	}
	if strings.TrimSpace(streamLabel) == "" {
		return errors.New("save lobby stream offset: stream label must not be empty")
	}
	if strings.TrimSpace(entryID) == "" {
		return errors.New("save lobby stream offset: entry id must not be empty")
	}

	if err := store.client.Set(ctx, store.keys.StreamOffset(streamLabel), entryID, 0).Err(); err != nil {
		return fmt.Errorf("save lobby stream offset: %w", err)
	}
	return nil
}

// Compile-time interface assertion.
var _ ports.StreamOffsetStore = (*StreamOffsetStore)(nil)