package cache

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"aiaa-notification-service/internal/config"

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

type Cache struct {
	rdb *redis.Client
}

// CachedRule holds the minimal info needed after rule matching.
type CachedRule struct {
	RuleID     int    `json:"rule_id"`
	TemplateID int    `json:"template_id"`
	Content    string `json:"content"`
	Conditions string `json:"conditions"` // JSON string, empty if null
}

type CachedChannel struct {
	ID     int              `json:"id"`
	Type   string           `json:"type"`
	Config *json.RawMessage `json:"config"`
}

func NewCache(cfg config.RedisConfig) (*Cache, error) {
	rdb := redis.NewClient(&redis.Options{
		Addr:     cfg.Addr(),
		Password: cfg.Password,
		DB:       cfg.DB,
	})
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	if err := rdb.Ping(ctx).Err(); err != nil {
		return nil, fmt.Errorf("redis ping: %w", err)
	}
	return &Cache{rdb: rdb}, nil
}

// --- Rule cache ---

func ruleKey(sourceID int, event string) string {
	return fmt.Sprintf("notify:rule:%d:%s", sourceID, event)
}

func (c *Cache) GetRule(ctx context.Context, sourceID int, event string) (*CachedRule, error) {
	data, err := c.rdb.Get(ctx, ruleKey(sourceID, event)).Bytes()
	if err != nil {
		return nil, err
	}
	var cr CachedRule
	if err := json.Unmarshal(data, &cr); err != nil {
		return nil, err
	}
	return &cr, nil
}

func (c *Cache) SetRule(ctx context.Context, sourceID int, event string, cr *CachedRule) error {
	data, err := json.Marshal(cr)
	if err != nil {
		return err
	}
	return c.rdb.Set(ctx, ruleKey(sourceID, event), data, 5*time.Minute).Err()
}

func (c *Cache) InvalidateRule(ctx context.Context, sourceID int, event string) error {
	return c.rdb.Del(ctx, ruleKey(sourceID, event)).Err()
}

// --- Channel cache ---

func channelsKey(ruleID int) string {
	return fmt.Sprintf("notify:channels:%d", ruleID)
}

func (c *Cache) GetChannels(ctx context.Context, ruleID int) ([]CachedChannel, error) {
	data, err := c.rdb.Get(ctx, channelsKey(ruleID)).Bytes()
	if err != nil {
		return nil, err
	}
	var channels []CachedChannel
	if err := json.Unmarshal(data, &channels); err != nil {
		return nil, err
	}
	return channels, nil
}

func (c *Cache) SetChannels(ctx context.Context, ruleID int, channels []CachedChannel) error {
	data, err := json.Marshal(channels)
	if err != nil {
		return err
	}
	return c.rdb.Set(ctx, channelsKey(ruleID), data, 5*time.Minute).Err()
}

func (c *Cache) InvalidateChannels(ctx context.Context, ruleID int) error {
	return c.rdb.Del(ctx, channelsKey(ruleID)).Err()
}

// --- Bulk invalidation ---

func (c *Cache) InvalidateBySource(ctx context.Context, sourceID int) error {
	pattern := fmt.Sprintf("notify:rule:%d:*", sourceID)
	iter := c.rdb.Scan(ctx, 0, pattern, 0).Iterator()
	var errs []error
	for iter.Next(ctx) {
		if err := c.rdb.Del(ctx, iter.Val()).Err(); err != nil {
			errs = append(errs, err)
		}
	}
	if len(errs) > 0 {
		return fmt.Errorf("invalidate by source %d: %d deletions failed: %w", sourceID, len(errs), errs[0])
	}
	return iter.Err()
}

func (c *Cache) InvalidateByTemplate(ctx context.Context, templateID int) error {
	// Template changes mean all cached rule info is stale. Simplest: scan all rule keys.
	// In production, you'd maintain a template to rule reverse index. For v1, scan is acceptable.
	iter := c.rdb.Scan(ctx, 0, "notify:rule:*", 0).Iterator()
	var errs []error
	for iter.Next(ctx) {
		if err := c.rdb.Del(ctx, iter.Val()).Err(); err != nil {
			errs = append(errs, err)
		}
	}
	if len(errs) > 0 {
		return fmt.Errorf("invalidate by template %d: %d deletions failed: %w", templateID, len(errs), errs[0])
	}
	return iter.Err()
}

// --- Rate limiter ---

func (c *Cache) CheckRateLimit(ctx context.Context, sourceID int, limitPerSec int) (bool, int, error) {
	key := fmt.Sprintf("ratelimit:%d", sourceID)
	now := time.Now().UnixNano() / 1e6 // milliseconds for uniqueness
	windowStart := time.Now().Unix() - 1

	script := redis.NewScript(`
		local key = KEYS[1]
		local now = tonumber(ARGV[1])
		local window_start = tonumber(ARGV[2])
		local limit = tonumber(ARGV[3])

		redis.call('ZREMRANGEBYSCORE', key, '-inf', window_start)
		local count = redis.call('ZCARD', key)

		if count >= limit then
			return 0
		end

		redis.call('ZADD', key, now, now)
		redis.call('EXPIRE', key, 2)
		return 1
	`)

	result, err := script.Run(ctx, c.rdb, []string{key}, now, windowStart, limitPerSec).Int()
	if err != nil {
		return false, 1, fmt.Errorf("rate limit check: %w", err)
	}

	if result == 0 {
		return false, 1, nil // rate limited
	}
	return true, 0, nil // allowed
}

func (c *Cache) Close() error {
	return c.rdb.Close()
}