efritz/gache

package gache

import (
    "fmt"

    "github.com/efritz/deepjoy"
    "github.com/garyburd/redigo/redis"
)

type (
    redisCache struct {
        client deepjoy.Client
        prefix string
        ttl    int
    }
)

// NewRedisCache creates a Cache instance using a local memory backend.
func NewRedisCache(client deepjoy.Client, configs ...RedisConfig) Cache {
    rc := &redisCache{
        client: client,
        ttl:    3600,
    }

    for _, config := range configs {
        config(rc)
    }

    return rc
}

// GetValue retrieves a value associated with a key from
// Redis. The read replica will be queried for this method
// only if the deepjoy Client is configured to do so.
func (rc *redisCache) GetValue(key string) (string, error) {
    val, err := rc.client.ReadReplica().Do("GET", rc.makeKey(key))
    if err == nil && val == nil {
        return "", nil
    }

    return redis.String(val, err)
}

// SetValue associates a key with a value in Redis.
func (rc *redisCache) SetValue(key, value string, tags ...string) error {
    args := []interface{}{}
    args = append(args, setScript)
    args = append(args, 0)
    args = append(args, rc.makeKey(key))
    args = append(args, value)
    args = append(args, rc.ttl)
    args = append(args, tagsToArgs(tags)...)

    _, err := rc.client.Do("EVAL", args...)
    return err
}

// Remove removes a value from Redis.
func (rc *redisCache) Remove(key string) error {
    _, err := rc.client.Do("DEL", rc.makeKey(key))
    return err
}

// BustTags removes all keys associated with the given tags
// from Redis.
func (rc *redisCache) BustTags(tags ...string) error {
    args := []interface{}{}
    args = append(args, bustScript)
    args = append(args, 0)
    args = append(args, tagsToArgs(tags)...)

    _, err := rc.client.Do("EVAL", args...)
    return err
}

func (rc *redisCache) makeKey(key string) string {
    if rc.prefix == "" {
        return key
    }

    return fmt.Sprintf("%s.%s", rc.prefix, key)
}

func tagsToArgs(tags []string) []interface{} {
    args := []interface{}{}
    for _, tag := range tags {
        args = append(args, tag)
    }

    return args
}