// Package diagram provide diagram data structure and operation
package diagram

import (
	"context"
	"fmt"
	"strconv"

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

// RedisClient define struct to accessing redis data that does not require the use of distributed locks
type RedisClient struct {
	Client *redis.Client
}

// QueryLatestMeasurementValue returns the score whose member contains the
// greatest numeric timestamp. Measurement ZSets currently store timestamp in
// member and measurement value in score.
func (rc *RedisClient) QueryLatestMeasurementValue(ctx context.Context, key string) (float64, error) {
	if rc.Client == nil {
		return 0, fmt.Errorf("redis client is not initialized")
	}

	members, err := rc.Client.ZRangeWithScores(ctx, key, 0, -1).Result()
	if err != nil {
		return 0, err
	}
	return latestMeasurementValue(members, key)
}

func latestMeasurementValue(members []redis.Z, key string) (float64, error) {
	if len(members) == 0 {
		return 0, fmt.Errorf("real-time measurement value not found for key %q", key)
	}

	var latestTimestamp int64
	var latestValue float64
	found := false
	for _, member := range members {
		timestamp, err := strconv.ParseInt(fmt.Sprint(member.Member), 10, 64)
		if err != nil {
			continue
		}
		if !found || timestamp > latestTimestamp {
			latestTimestamp = timestamp
			latestValue = member.Score
			found = true
		}
	}
	if !found {
		return 0, fmt.Errorf("real-time measurement timestamps are invalid for key %q", key)
	}
	return latestValue, nil
}

// NewRedisClient define func of new redis client instance
func NewRedisClient() *RedisClient {
	return &RedisClient{
		Client: GetRedisClientInstance(),
	}
}

// QueryByZRange define func to query real time data from redis zset
func (rc *RedisClient) QueryByZRange(ctx context.Context, key string, size int64) ([]redis.Z, error) {
	client := rc.Client
	args := redis.ZRangeArgs{
		Key:     key,
		Start:   0,
		Stop:    size,
		ByScore: false,
		ByLex:   false,
		Rev:     false,
		Offset:  0,
		Count:   0,
	}
	return client.ZRangeArgsWithScores(ctx, args).Result()
}