package session

import (
	"context"
	"sync"
	"time"

	"github.com/go-redis/redis/v8"
	"go.mongodb.org/mongo-driver/bson"
	"repositories.action2quare.com/ayo/gocommon"
	"repositories.action2quare.com/ayo/gocommon/logger"
)

type innerSession[T any] struct {
	inner    *T
	expireAt time.Time
}

type cache_stage[T any] struct {
	cache   map[string]innerSession[T]
	deleted map[string]bool
}

func make_cache_stage[T any]() *cache_stage[T] {
	return &cache_stage[T]{
		cache:   make(map[string]innerSession[T]),
		deleted: make(map[string]bool),
	}
}

type Consumer[T any] struct {
	lock        sync.Mutex
	redisClient *redis.Client
	ttl         time.Duration
	ctx         context.Context
	stages      [2]*cache_stage[T]
	startTime   time.Time
}

func NewConsumer[T any](ctx context.Context, redisUrl string, ttl time.Duration) (*Consumer[T], error) {
	redisClient, err := gocommon.NewRedisClient(redisUrl)
	if err != nil {
		return nil, err
	}

	consumer := &Consumer[T]{
		redisClient: redisClient,
		ttl:         ttl,
		ctx:         ctx,
		stages:      [2]*cache_stage[T]{make_cache_stage[T](), make_cache_stage[T]()},
		startTime:   time.Now(),
	}

	updateChannel := communication_channel_name_prefix + "_u"
	deleteChannel := communication_channel_name_prefix + "_d"
	sub := redisClient.Subscribe(ctx, updateChannel, deleteChannel)

	go func() {
		stageswitch := time.Now().Add(ttl)
		tickTimer := time.After(ttl)

		for {
			select {
			case <-ctx.Done():
				return

			case <-tickTimer:
				consumer.changeStage()
				stageswitch = stageswitch.Add(ttl)
				tempttl := time.Until(stageswitch)
				tickTimer = time.After(tempttl)

			case msg := <-sub.Channel():
				if msg == nil {
					return
				}

				if len(msg.Payload) == 0 {
					continue
				}

				switch msg.Channel {
				case updateChannel:
					key := msg.Payload
					raw, err := redisClient.Get(ctx, key).Result()
					if err != nil {
						logger.Println(err)
					} else if len(raw) > 0 {
						var si T
						if bson.Unmarshal([]byte(raw), &si) == nil {
							consumer.add(key, &si)
						}
					}
				case deleteChannel:
					key := msg.Payload
					consumer.delete(key)
				}
			}
		}
	}()

	return consumer, nil
}

func (c *Consumer[T]) add_internal(key string, si *T, ttl time.Duration) {
	inner := innerSession[T]{
		inner:    si,
		expireAt: time.Now().Add(ttl),
	}

	c.stages[0].cache[key] = inner
	delete(c.stages[0].deleted, key)
	c.stages[1].cache[key] = inner
	delete(c.stages[1].deleted, key)

	logger.Printf("add : %v, %v\n", *c.stages[0], *c.stages[1])
}

func (c *Consumer[T]) add(key string, si *T) {
	c.lock.Lock()
	defer c.lock.Unlock()

	c.add_internal(key, si, c.ttl)
}

func (c *Consumer[T]) delete(key string) {
	c.lock.Lock()
	defer c.lock.Unlock()

	delete(c.stages[0].cache, key)
	c.stages[0].deleted[key] = true
	delete(c.stages[1].cache, key)
	c.stages[1].deleted[key] = true

	logger.Printf("delete : %v, %v\n", *c.stages[0], *c.stages[1])
}

func (c *Consumer[T]) changeStage() {
	c.lock.Lock()
	defer c.lock.Unlock()

	logger.Printf("changeStage : %v, %v\n", *c.stages[0], *c.stages[1])

	c.stages[1] = c.stages[0]
	c.stages[0] = make_cache_stage[T]()

	logger.Printf("---> : %v, %v\n", *c.stages[0], *c.stages[1])
}

func (c *Consumer[T]) Query(key string) *T {
	c.lock.Lock()
	defer c.lock.Unlock()

	if _, deleted := c.stages[0].deleted[key]; deleted {
		return nil
	}

	if _, deleted := c.stages[1].deleted[key]; deleted {
		return nil
	}

	found, ok := c.stages[0].cache[key]
	if !ok {
		found, ok = c.stages[1].cache[key]
	}

	if ok {
		if found.expireAt.After(time.Now()) {
			return found.inner
		}
	}

	payload, err := c.redisClient.Get(c.ctx, key).Result()
	if err == redis.Nil {
		return nil
	} else if err != nil {
		logger.Println("consumer Query :", err)
		return nil
	}

	if len(payload) > 0 {
		var si T
		if bson.Unmarshal([]byte(payload), &si) == nil {
			ttl, err := c.redisClient.TTL(c.ctx, key).Result()
			if err != nil {
				logger.Println("consumer Query :", err)
				return nil
			}

			c.add_internal(key, &si, ttl)
			return &si
		}
	}
	return nil
}

func (c *Consumer[T]) Touch(key string) bool {
	c.lock.Lock()
	defer c.lock.Unlock()

	ok, err := c.redisClient.Expire(c.ctx, key, c.ttl).Result()
	if err == redis.Nil {
		return false
	} else if err != nil {
		logger.Println("consumer Touch :", err)
		return false
	}

	if ok {
		newexpire := time.Now().Add(c.ttl)
		found, ok := c.stages[0].cache[key]
		if ok {
			found.expireAt = newexpire
		}

		found, ok = c.stages[1].cache[key]
		if ok {
			found.expireAt = newexpire
		}
	}

	return ok
}