package main

import (
	"errors"
	"net"
	"strconv"
	"time"
)

func handleGet(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

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

    key := args[1]

	item, exists := db.data[key]
	if !exists {
		conn.Write(serializeRESP(nil)) 
        return
	}

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

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

	conn.Write(serializeRESP(strValue))
}

func handleExists(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

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

	key := args[1]

	_, exists := db.data[key]
	if exists {
		conn.Write(serializeRESP(1))
	} else {
		conn.Write(serializeRESP(0))
	}
}

func handleSet(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

	if len(args) != 3 {
        err := errors.New("wrong number of arguments for 'SET'")
        conn.Write(serializeRESP(err))
		return
    }

	key := args[1]
	item := Item{Value: args[2]}

	db.data[key] = item
	conn.Write(serializeRESP(SimpleString("OK")))
}

func handleDel(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

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

	key := args[1]

	_, exists := db.data[key]
	if exists {
		delete(db.data, key)
		conn.Write(serializeRESP(1))
	} else {
		conn.Write(serializeRESP(0))
	}
}

func handleIncr(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

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

	key := args[1]

	item, exists := db.data[key]
	if exists {
		strValue, ok := item.Value.(string)
		if !ok {
			err := errors.New("value is not an integer or out of range")
			conn.Write(serializeRESP(err))
			return
		}

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

		newValueStr := strconv.Itoa(currentInt + 1)
		db.data[key] = Item{Value: newValueStr}
		conn.Write(serializeRESP(currentInt + 1))
	} else {
		db.data[key] = Item{Value: "1"}
		conn.Write(serializeRESP(1))
	}
}

func handleDecr(conn net.Conn, args []string) {
	db.mu.Lock()
	defer db.mu.Unlock()

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

	key := args[1]

	item, exists := db.data[key]
	if exists {
		strValue, ok := item.Value.(string)
		if !ok {
			err := errors.New("value is not an integer or out of range")
			conn.Write(serializeRESP(err))
			return
		}

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

		newValueStr := strconv.Itoa(currentInt - 1)
		db.data[key] = Item{Value:newValueStr}
		conn.Write(serializeRESP(currentInt - 1))
	} else {
		db.data[key] = Item{Value: "-1"}
		conn.Write(serializeRESP(-1))
	}
}

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) {
	db.mu.Lock()
	defer db.mu.Unlock()

	if len(args) != 1 {
        err := errors.New("wrong number of arguments for 'FLUSHALL'")
        conn.Write(serializeRESP(err))
		return
    }

	db.data = make(map[string]Item)
	conn.Write(serializeRESP(SimpleString("OK")))
}

func handleRpush(conn net.Conn, args []string) {
	key := args[1]
	newItems := args[2:]

	if len(args) < 3 {
        err := errors.New("wrong number of arguments for 'RPUSH'")
        conn.Write(serializeRESP(err))
		return
    }

	db.mu.Lock()
	defer db.mu.Unlock()

	var list []string
	existingItem, exists := db.data[key]

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

func handleLpush(conn net.Conn, args []string) {
	key := args[1]
	newItems := args[2:]

	if len(args) < 3 {
        err := errors.New("wrong number of arguments for 'LPUSH'")
        conn.Write(serializeRESP(err))
		return
    }

	db.mu.Lock()
	defer db.mu.Unlock()

	var list []string
	existingItem, exists := db.data[key]

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

func handleLrange(conn net.Conn, args []string) {
    db.mu.Lock()
    defer db.mu.Unlock()

	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]

    item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP([]string{}))

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

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

    resultList := typedList[start : stop+1]
    conn.Write(serializeRESP(resultList))
}

func handleLpop(conn net.Conn, args []string){
	db.mu.Lock()
    defer db.mu.Unlock()

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

	key := args[1]
    item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

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

	if len(typedList) == 0 {
        conn.Write(serializeRESP(nil))
        return
    }

	newItem := typedList[0]
	newList := typedList[1:]
	if len(newList) <= 0 {
		delete(db.data, key)
	}else{
		db.data[key] = Item{Value: newList}
	}
	conn.Write(serializeRESP(newItem))

}

func handleRpop(conn net.Conn, args []string){
	db.mu.Lock()
    defer db.mu.Unlock()

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

	key := args[1]
    item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

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

	if len(typedList) == 0 {
        conn.Write(serializeRESP(nil))
        return
    }
	
	newItem := typedList[len(typedList)-1]
	newList := typedList[:len(typedList)-1]
	if len(newList) <= 0 {
		delete(db.data, key)
	}else{
		db.data[key] = Item{Value: newList}
	}
	conn.Write(serializeRESP(newItem))

}

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("ERR value is not an integer")))
        return
    }
	db.mu.Lock()
    defer db.mu.Unlock()

	item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(0)) // Key doesn't exist
        return
    }

	expiry := time.Now().Add(time.Duration(seconds) * time.Second)
    item.ExpiresAt = &expiry
    db.data[key] = item
    conn.Write(serializeRESP(1))
}

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]
	db.mu.Lock()
    defer db.mu.Unlock()

    item, exists := db.data[key]
    
    var hash map[string]string

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

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

    key := args[1]
    field := args[2]

    db.mu.Lock()
    defer db.mu.Unlock()

    item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

    hash, ok := item.Value.(map[string]string)
    if !ok {
        conn.Write(serializeRESP(errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")))
        return
    }

    val, found := hash[field]
    if !found {
        conn.Write(serializeRESP(nil))
        return
    }

    conn.Write(serializeRESP(val))
}

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

	db.mu.Lock()
    defer db.mu.Unlock()

    item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

    hash, ok := item.Value.(map[string]string)
    if !ok {
        conn.Write(serializeRESP(errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")))
        return
    }
	conn.Write(serializeRESP(hash))
}

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

	db.mu.Lock()
    defer db.mu.Unlock()

	item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

    hash, ok := item.Value.(map[string]string)
    if !ok {
        conn.Write(serializeRESP(errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")))
        return
    }
	result := make([]string, 0, len(hash))
	for key := range hash {
		result = append(result, key)
	}
	conn.Write(serializeRESP(result))
}

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

	db.mu.Lock()
    defer db.mu.Unlock()

	item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(nil))
        return
    }

    hash, ok := item.Value.(map[string]string)
    if !ok {
        conn.Write(serializeRESP(errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")))
        return
    }
	result := make([]string, 0, len(hash))
	for _, value := range hash {
		result = append(result, value)
	}
	conn.Write(serializeRESP(result))
}

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

	db.mu.Lock()
    defer db.mu.Unlock()

	item, exists := db.data[key]
    if !exists {
        conn.Write(serializeRESP(SimpleString("none")))
        return
    }

	switch item.Value.(type) {
    case string:
        conn.Write(serializeRESP(SimpleString("string")))
    case []string:
		conn.Write(serializeRESP(SimpleString("list")))
	case map[string]string:
		conn.Write(serializeRESP(SimpleString("hash")))
	default:
        conn.Write(serializeRESP(SimpleString("unknown")))
    }
}