package main

import (
	"errors"
	"net"
	"path/filepath"
	"sort"
	"strconv"
	"time"
)

func handleGet(conn net.Conn, args []string) {
	if len(args) != 2 {
        err := errors.New("wrong number of arguments for 'GET'")
        conn.Write(serializeRESP(err))
		return
    }
    
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{}{
		item, exists := s.data[key]
		if !exists {
			return nil
		}

		if item.ExpiresAt != nil && time.Now().After(*item.ExpiresAt) {
			delete(s.data, key)
			return nil
		}

		strValue, ok := item.Value.(string)
		if !ok {
			err := errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
			return err
		}
		return strValue
	})


	conn.Write(serializeRESP(result))
}

func handleExists(conn net.Conn, args []string) {
	if len(args) != 2 {
        err := errors.New("wrong number of arguments for 'EXISTS'")
        conn.Write(serializeRESP(err))
		return
    }

	key := args[1]
	result := db.ExecuteRead(key, func(s *Shard) interface{}{
		_, exists := s.data[key]
		if exists {
			return 1
		} else {
			return 0
		}
	})

	conn.Write(serializeRESP(result))
}

func handleSet(conn net.Conn, args []string) {
	if len(args) != 3 {
        err := errors.New("wrong number of arguments for 'SET'")
        conn.Write(serializeRESP(err))
		return
    }

	key := args[1]
	result := db.Execute(key, func(s *Shard) interface{}{
		item := Item{Value: args[2]}
		s.data[key] = item
		return SimpleString("OK")
	})

	conn.Write(serializeRESP(result))
}

func handleDel(conn net.Conn, args []string) {

	if len(args) < 2 {
        err := errors.New("wrong number of arguments for 'DEL'")
        conn.Write(serializeRESP(err))
		return
    }
	keys := args[1:]
	deletedKeys := db.ExecuteMulti(keys, func(shards []*Shard) interface{}{
		count := 0
		for _, key := range keys{
			shard := db.getShard(key)
			_, exists := shard.data[key]
			if exists {
				delete(shard.data, key)
				count += 1
			} 
		}
		return count
	})
	conn.Write(serializeRESP(deletedKeys))
}


func handleIncr(conn net.Conn, args []string) {

	if len(args) != 2 {
        err := errors.New("wrong number of arguments for 'INCR'")
        conn.Write(serializeRESP(err))
		return
    }

	key := args[1]
	result := db.Execute(key, func(s *Shard)interface{}{
		item, exists := s.data[key]
		if exists {
			strValue, ok := item.Value.(string)
			if !ok {
				err := errors.New("value is not an integer or out of range")
				return err
			}

			currentInt, err := strconv.Atoi(strValue)
			if err != nil {
				err := errors.New("value is not an integer or out of range")
				return err
			}

			newValueStr := strconv.Itoa(currentInt + 1)
			s.data[key] = Item{Value: newValueStr}
			return currentInt + 1
		} else {
			s.data[key] = Item{Value: "1"}
			return 1
		}

	})

	conn.Write(serializeRESP(result))
}

func handleDecr(conn net.Conn, args []string) {

	if len(args) != 2 {
        err := errors.New("wrong number of arguments for 'DECR'")
        conn.Write(serializeRESP(err))
		return
    }

	key := args[1]
	result := db.Execute(key, func(s *Shard)interface{}{
		item, exists := s.data[key]
		if exists {
			strValue, ok := item.Value.(string)
			if !ok {
				err := errors.New("value is not an integer or out of range")
				return err
			}

			currentInt, err := strconv.Atoi(strValue)
			if err != nil {
				err := errors.New("value is not an integer or out of range")
				return err
			}

			newValueStr := strconv.Itoa(currentInt + 1)
			s.data[key] = Item{Value: newValueStr}
			return currentInt - 1
		} else {
			s.data[key] = Item{Value: "1"}
			return -1
		}

	})

	conn.Write(serializeRESP(result))
}

func handlePing(conn net.Conn, args []string) {
	if len(args) != 1 {
        err := errors.New("wrong number of arguments for 'PING'")
        conn.Write(serializeRESP(err))
		return
    }
	conn.Write(serializeRESP(SimpleString("PONG")))
}

func handleFlushall(conn net.Conn, args []string) {
	if len(args) != 1 {
        err := errors.New("wrong number of arguments for 'FLUSHALL'")
        conn.Write(serializeRESP(err))
		return
    }
	result := db.ExecuteAll(func(shards []*Shard)interface{}{
		for _, shard := range shards{
			shard.data = make(map[string]Item)
		}
		return SimpleString("OK")
	})
	conn.Write(serializeRESP(result))
}

func handleRename(conn net.Conn, args []string){
	if len(args) != 3 {
        err := errors.New("wrong number of arguments for 'RENAME'")
        conn.Write(serializeRESP(err))
		return
    }
	keys := args[1:]

	result := db.ExecuteMulti(keys,func(shards []*Shard)interface{}{
		item, exists := db.getShard(keys[0]).data[keys[0]]
		if !exists {

			return errors.New("no such key")
		}

		db.getShard(keys[1]).data[keys[1]] = item
		delete(db.getShard(keys[0]).data, keys[0])

		return SimpleString("OK")
	})
	conn.Write(serializeRESP(result))
}

func handleRpush(conn net.Conn, args []string) {
	if len(args) < 3 {
		err := errors.New("wrong number of arguments for 'RPUSH'")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]
	newItems := args[2:]

	result := db.Execute(key, func(s *Shard) interface{} {
		var list []string
		existingItem, exists := s.data[key]
		if exists {
			var ok bool
			list, ok = existingItem.Value.([]string)
			if !ok {
				return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
			}
		} else {
			list = []string{}
		}
		list = append(list, newItems...)
		s.data[key] = Item{Value: list}
		return len(list)
	})
	conn.Write(serializeRESP(result))
}

func handleLpush(conn net.Conn, args []string) {
	if len(args) < 3 {
		err := errors.New("wrong number of arguments for 'LPUSH'")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]
	newItems := args[2:]

	result := db.Execute(key, func(s *Shard) interface{} {
		var list []string
		existingItem, exists := s.data[key]
		if exists {
			var ok bool
			list, ok = existingItem.Value.([]string)
			if !ok {
				return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
			}
		} else {
			list = []string{}
		}
		list = append(newItems, list...)
		s.data[key] = Item{Value: list}
		return len(list)
	})
	conn.Write(serializeRESP(result))
}

func handleLrange(conn net.Conn, args []string) {
	if len(args) != 4 {
		err := errors.New("wrong number of arguments for 'LRANGE'")
		conn.Write(serializeRESP(err))
		return
	}
	start, err1 := strconv.Atoi(args[2])
	stop, err2 := strconv.Atoi(args[3])
	if err1 != nil || err2 != nil {
		err := errors.New("value is not an integer or out of range")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return []string{}
		}
		if item.ExpiresAt != nil && time.Now().After(*item.ExpiresAt) {
			delete(s.data, key)
			return nil
		}
		typedList, ok := item.Value.([]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		size := len(typedList)
		if start < 0 {
			start += size
			if start < 0 {
				start = 0
			}
		}
		if stop < 0 {
			stop += size
			if stop < 0 {
				stop = 0
			}
		}
		if stop >= size {
			stop = size - 1
		}
		if start > stop || start >= size {
			return []string{}
		}
		return typedList[start : stop+1]
	})
	conn.Write(serializeRESP(result))
}

func handleLpop(conn net.Conn, args []string) {
	if len(args) != 2 {
		err := errors.New("wrong number of arguments for 'LPOP'")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]

	result := db.Execute(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		typedList, ok := item.Value.([]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		if len(typedList) == 0 {
			return nil
		}
		newItem := typedList[0]
		newList := typedList[1:]
		if len(newList) <= 0 {
			delete(s.data, key)
		} else {
			s.data[key] = Item{Value: newList}
		}
		return newItem
	})
	conn.Write(serializeRESP(result))
}

func handleRpop(conn net.Conn, args []string) {
	if len(args) != 2 {
		err := errors.New("wrong number of arguments for 'RPOP'")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]

	result := db.Execute(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		typedList, ok := item.Value.([]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		if len(typedList) == 0 {
			return nil
		}
		newItem := typedList[len(typedList)-1]
		newList := typedList[:len(typedList)-1]
		if len(newList) <= 0 {
			delete(s.data, key)
		} else {
			s.data[key] = Item{Value: newList}
		}
		return newItem
	})
	conn.Write(serializeRESP(result))
}

func handleExpire(conn net.Conn, args []string) {
	if len(args) != 3 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'EXPIRE'")))
		return
	}
	key := args[1]
	seconds, err := strconv.Atoi(args[2])
	if err != nil {
		conn.Write(serializeRESP(errors.New("value is not an integer")))
		return
	}

	result := db.Execute(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return 0
		}
		expiry := time.Now().Add(time.Duration(seconds) * time.Second)
		item.ExpiresAt = &expiry
		s.data[key] = item
		return 1
	})
	conn.Write(serializeRESP(result))
}

func handleHset(conn net.Conn, args []string) {
	if len(args) < 4 || (len(args)-2)%2 != 0 {
		err := errors.New("wrong number of arguments for 'HSET'")
		conn.Write(serializeRESP(err))
		return
	}
	key := args[1]

	result := db.Execute(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		var hash map[string]string
		if exists {
			var ok bool
			hash, ok = item.Value.(map[string]string)
			if !ok {
				return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
			}
		} else {
			hash = make(map[string]string)
		}
		count := 0
		for i := 2; i < len(args); i += 2 {
			hash[args[i]] = args[i+1]
			count++
		}
		s.data[key] = Item{Value: hash}
		return count
	})
	conn.Write(serializeRESP(result))
}

func handleHget(conn net.Conn, args []string) {
	if len(args) != 3 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'HGET'")))
		return
	}
	key := args[1]
	field := args[2]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		hash, ok := item.Value.(map[string]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		val, found := hash[field]
		if !found {
			return nil
		}
		return val
	})
	conn.Write(serializeRESP(result))
}

func handleHgetall(conn net.Conn, args []string) {
	if len(args) != 2 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'HGETALL'")))
		return
	}
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		hash, ok := item.Value.(map[string]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		return hash
	})
	conn.Write(serializeRESP(result))
}

func handleHkeys(conn net.Conn, args []string) {
	if len(args) != 2 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'HKEYS'")))
		return
	}
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		hash, ok := item.Value.(map[string]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		keys := make([]string, 0, len(hash))
		for k := range hash {
			keys = append(keys, k)
		}
		return keys
	})
	conn.Write(serializeRESP(result))
}

func handleHvalues(conn net.Conn, args []string) {
	if len(args) != 2 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'HVALUES'")))
		return
	}
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return nil
		}
		hash, ok := item.Value.(map[string]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}
		values := make([]string, 0, len(hash))
		for _, v := range hash {
			values = append(values, v)
		}
		return values
	})
	conn.Write(serializeRESP(result))
}

func handleType(conn net.Conn, args []string) {
	if len(args) != 2 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'TYPE'")))
		return
	}
	key := args[1]

	result := db.ExecuteRead(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return SimpleString("none")
		}
		switch item.Value.(type) {
		case string:
			return SimpleString("string")
		case []string:
			return SimpleString("list")
		case map[string]string:
			return SimpleString("hash")
		default:
			return SimpleString("unknown")
		}
	})
	conn.Write(serializeRESP(result))
}

func handleDbsize(conn net.Conn, args []string) {
	if len(args) != 1 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'DBSIZE'")))
		return
	}
	result := db.ExecuteReadAll(func(shards []*Shard) interface{} {
		count := 0
		for _, shard := range shards {
			count += len(shard.data)
		}
		return count
	})
	conn.Write(serializeRESP(result))
}

func handleKeys(conn net.Conn, args []string) {
	if len(args) < 2 || len(args) > 3 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'KEYS'")))
		return
	}
	pattern := args[1]
	limit := -1
	if len(args) == 3 {
		val, err := strconv.Atoi(args[2])
		if err != nil {
			conn.Write(serializeRESP(errors.New("value is not an integer")))
			return
		}
		limit = val
	}

	result := db.ExecuteReadAll(func(shards []*Shard) interface{} {
		var matches []string
		for _, shard := range shards {
			for key := range shard.data {
				matched, err := filepath.Match(pattern, key)
				if err != nil {
					return errors.New("illegal glob pattern")
				}
				if matched {
					matches = append(matches, key)
				}
			}
		}
		sort.Strings(matches)
		if limit != -1 && len(matches) > limit {
			matches = matches[:limit]
		}
		return matches
	})
	conn.Write(serializeRESP(result))
}

func handleLrem(conn net.Conn, args []string) {
	if len(args) != 4 {
		conn.Write(serializeRESP(errors.New("wrong number of arguments for 'LREM'")))
		return
	}
	key := args[1]
	count, err := strconv.Atoi(args[2])
	toBeRemoved := args[3]
	if err != nil {
		conn.Write(serializeRESP(errors.New("value is not an integer")))
		return
	}

	result := db.Execute(key, func(s *Shard) interface{} {
		item, exists := s.data[key]
		if !exists {
			return 0
		}
		list, ok := item.Value.([]string)
		if !ok {
			return errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")
		}

		counter := 0
		absCount := count
		if count < 0 {
			absCount = -count
		}

		var newList []string
		if count == 0 {
			newList = []string{}
			for _, value := range list {
				if value == toBeRemoved {
					counter++
				} else {
					newList = append(newList, value)
				}
			}
		} else if count > 0 {
			newList = []string{}
			for _, value := range list {
				if value == toBeRemoved && counter < absCount {
					counter++
				} else {
					newList = append(newList, value)
				}
			}
		} else { // count < 0
			reversedNewList := []string{}
			for i := len(list) - 1; i >= 0; i-- {
				value := list[i]
				if value == toBeRemoved && counter < absCount {
					counter++
				} else {
					reversedNewList = append(reversedNewList, value)
				}
			}
			newList = make([]string, len(reversedNewList))
			for i, v := range reversedNewList {
				newList[len(reversedNewList)-1-i] = v
			}
		}

		if len(newList) == 0 {
			delete(s.data, key)
		} else {
			item.Value = newList
			s.data[key] = item
		}
		return counter
	})
	conn.Write(serializeRESP(result))
}