package redispkg

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"log"
	"time"

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

type R struct{ c *redis.Client }

func New(url string) *R {
	if url == "" {
		return &R{}
	}
	opt, err := redis.ParseURL(url)
	if err != nil {
		log.Printf("bad REDIS_URL (%v): redis disabled", err)
		return &R{}
	}
	return &R{c: redis.NewClient(opt)}
}

func (r *R) Get(ctx context.Context, key string) (string, bool) {
	if r.c == nil {
		return "", false
	}
	v, err := r.c.Get(ctx, key).Result()
	if err != nil {
		return "", false // 故障=miss
	}
	return v, true
}

func (r *R) Set(ctx context.Context, key, val string, ttl time.Duration) {
	if r.c == nil {
		return
	}
	if err := r.c.Set(ctx, key, val, ttl).Err(); err != nil {
		log.Printf("redis set %s: %v", key, err)
	}
}

func (r *R) IncrWindow(ctx context.Context, key string, ttl time.Duration) int {
	if r.c == nil {
		return 1
	}
	n, err := r.c.Incr(ctx, key).Result()
	if err != nil {
		return 1
	}
	if n == 1 {
		r.c.Expire(ctx, key, ttl)
	}
	return int(n)
}

func (r *R) Lock(ctx context.Context, key string, ttl time.Duration) (func(), bool) {
	noop := func() {}
	if r.c == nil {
		return noop, true
	}
	b := make([]byte, 8)
	rand.Read(b)
	tok := hex.EncodeToString(b)
	ok, err := r.c.SetNX(ctx, key, tok, ttl).Result()
	if err != nil { // spec §9: Redis 故障降级放行,锁只做尽力去重
		log.Printf("redis lock %s: %v (proceeding without lock)", key, err)
		return noop, true
	}
	if !ok {
		return noop, false // 锁被持有,别的副本在扫
	}
	return func() {
		r.c.Eval(ctx,
			"if redis.call('get',KEYS[1])==ARGV[1] then return redis.call('del',KEYS[1]) else return 0 end",
			[]string{key}, tok)
	}, true
}