// Commands from https://redis.io/commands#string

package miniredis

import (
	"math/big"
	"strconv"
	"strings"
	"time"

	"github.com/alicebob/miniredis/v2/server"
)

// commandsString handles all string value operations.
func commandsString(m *Miniredis) {
	m.srv.Register("APPEND", m.cmdAppend)
	m.srv.Register("BITCOUNT", m.cmdBitcount, server.ReadOnlyOption())
	m.srv.Register("BITOP", m.cmdBitop)
	m.srv.Register("BITPOS", m.cmdBitpos, server.ReadOnlyOption())
	m.srv.Register("DECRBY", m.cmdDecrby)
	m.srv.Register("DECR", m.cmdDecr)
	m.srv.Register("GETBIT", m.cmdGetbit, server.ReadOnlyOption())
	m.srv.Register("GET", m.cmdGet, server.ReadOnlyOption())
	m.srv.Register("GETEX", m.cmdGetex)
	m.srv.Register("GETRANGE", m.cmdGetrange, server.ReadOnlyOption())
	m.srv.Register("GETSET", m.cmdGetset)
	m.srv.Register("GETDEL", m.cmdGetdel)
	m.srv.Register("INCRBYFLOAT", m.cmdIncrbyfloat)
	m.srv.Register("INCRBY", m.cmdIncrby)
	m.srv.Register("INCR", m.cmdIncr)
	m.srv.Register("MGET", m.cmdMget, server.ReadOnlyOption())
	m.srv.Register("MSET", m.cmdMset)
	m.srv.Register("MSETNX", m.cmdMsetnx)
	m.srv.Register("PSETEX", m.cmdPsetex)
	m.srv.Register("SETBIT", m.cmdSetbit)
	m.srv.Register("SETEX", m.cmdSetex)
	m.srv.Register("SET", m.cmdSet)
	m.srv.Register("SETNX", m.cmdSetnx)
	m.srv.Register("SETRANGE", m.cmdSetrange)
	m.srv.Register("STRLEN", m.cmdStrlen, server.ReadOnlyOption())
}

// SET
func (m *Miniredis) cmdSet(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(2)) {
		return
	}

	var opts struct {
		key     string
		value   string
		nx      bool // set iff not exists
		xx      bool // set iff exists
		keepttl bool // set keepttl
		ttlSet  bool
		ttl     time.Duration
		get     bool
	}

	opts.key, opts.value, args = args[0], args[1], args[2:]
	for len(args) > 0 {
		timeUnit := time.Second
		switch arg := strings.ToUpper(args[0]); arg {
		case "NX":
			opts.nx = true
			args = args[1:]
			continue
		case "XX":
			opts.xx = true
			args = args[1:]
			continue
		case "KEEPTTL":
			opts.keepttl = true
			args = args[1:]
			continue
		case "PX", "PXAT":
			timeUnit = time.Millisecond
			fallthrough
		case "EX", "EXAT":
			if len(args) < 2 {
				setDirty(c)
				c.WriteError(msgInvalidInt)
				return
			}
			if opts.ttlSet {
				// multiple ex/exat/px/pxat options set
				setDirty(c)
				c.WriteError(msgSyntaxError)
				return
			}
			expire, err := strconv.Atoi(args[1])
			if err != nil {
				setDirty(c)
				c.WriteError(msgInvalidInt)
				return
			}
			if expire <= 0 {
				setDirty(c)
				c.WriteError(msgInvalidSETime)
				return
			}

			if arg == "PXAT" || arg == "EXAT" {
				opts.ttl = m.at(expire, timeUnit)
			} else {
				opts.ttl = time.Duration(expire) * timeUnit
			}
			opts.ttlSet = true

			args = args[2:]
			continue
		case "GET":
			opts.get = true
			args = args[1:]
			continue
		default:
			setDirty(c)
			c.WriteError(msgSyntaxError)
			return
		}
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		readonly := false
		if opts.nx {
			if db.exists(opts.key) {
				if opts.get {
					// special case for SET NX GET
					readonly = true
				} else {
					c.WriteNull()
					return
				}
			}
		}
		if opts.xx {
			if !db.exists(opts.key) {
				if opts.get {
					// special case for SET XX GET
					readonly = true
				} else {
					c.WriteNull()
					return
				}
			}
		}
		if opts.keepttl {
			if val, ok := db.ttl[opts.key]; ok {
				opts.ttl = val
			}
		}
		if opts.get {
			if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
				c.WriteError(msgWrongType)
				return
			}
		}

		old, existed := db.stringKeys[opts.key]
		if !readonly {
			db.del(opts.key, true) // be sure to remove existing values of other type keys.
			// a vanilla SET clears the expire
			if opts.ttl >= 0 { // EXAT/PXAT can expire right away
				db.stringSet(opts.key, opts.value)
			}
			if opts.ttl != 0 {
				db.ttl[opts.key] = opts.ttl
			}
		}
		if opts.get {
			if !existed {
				c.WriteNull()
			} else {
				c.WriteBulk(old)
			}
			return
		}
		c.WriteOK()
	})
}

// SETEX
func (m *Miniredis) cmdSetex(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(3)) {
		return
	}

	key := args[0]
	ttl, err := strconv.Atoi(args[1])
	if err != nil {
		setDirty(c)
		c.WriteError(msgInvalidInt)
		return
	}
	if ttl <= 0 {
		setDirty(c)
		c.WriteError(msgInvalidSETEXTime)
		return
	}
	value := args[2]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		db.del(key, true) // Clear any existing keys.
		db.stringSet(key, value)
		db.ttl[key] = time.Duration(ttl) * time.Second
		c.WriteOK()
	})
}

// PSETEX
func (m *Miniredis) cmdPsetex(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(3)) {
		return
	}

	var opts struct {
		key   string
		ttl   int
		value string
	}

	opts.key = args[0]
	if ok := optInt(c, args[1], &opts.ttl); !ok {
		return
	}
	if opts.ttl <= 0 {
		setDirty(c)
		c.WriteError(msgInvalidPSETEXTime)
		return
	}
	opts.value = args[2]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		db.del(opts.key, true) // Clear any existing keys.
		db.stringSet(opts.key, opts.value)
		db.ttl[opts.key] = time.Duration(opts.ttl) * time.Millisecond
		c.WriteOK()
	})
}

// SETNX
func (m *Miniredis) cmdSetnx(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	key, value := args[0], args[1]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if _, ok := db.keys[key]; ok {
			c.WriteInt(0)
			return
		}

		db.stringSet(key, value)
		c.WriteInt(1)
	})
}

// MSET
func (m *Miniredis) cmdMset(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(2)) {
		return
	}

	if len(args)%2 != 0 {
		setDirty(c)
		// non-default error message
		c.WriteError("ERR wrong number of arguments for MSET")
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		for len(args) > 0 {
			key, value := args[0], args[1]
			args = args[2:]

			db.del(key, true) // clear TTL
			db.stringSet(key, value)
		}
		c.WriteOK()
	})
}

// MSETNX
func (m *Miniredis) cmdMsetnx(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(2)) {
		return
	}

	if len(args)%2 != 0 {
		setDirty(c)
		// non-default error message (yes, with 'MSET').
		c.WriteError("ERR wrong number of arguments for MSET")
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		keys := map[string]string{}
		existing := false
		for len(args) > 0 {
			key := args[0]
			value := args[1]
			args = args[2:]
			keys[key] = value
			if _, ok := db.keys[key]; ok {
				existing = true
			}
		}

		res := 0
		if !existing {
			res = 1
			for k, v := range keys {
				// Nothing to delete. That's the whole point.
				db.stringSet(k, v)
			}
		}
		c.WriteInt(res)
	})
}

// GET
func (m *Miniredis) cmdGet(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(1)) {
		return
	}

	key := args[0]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if !db.exists(key) {
			c.WriteNull()
			return
		}
		if db.t(key) != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		c.WriteBulk(db.stringGet(key))
	})
}

// GETEX
func (m *Miniredis) cmdGetex(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(1)) {
		return
	}

	var opts struct {
		key     string
		ttl     time.Duration
		persist bool // remove existing TTL on the key.
	}

	opts.key, args = args[0], args[1:]
	if len(args) > 0 {
		timeUnit := time.Second
		switch arg := strings.ToUpper(args[0]); arg {
		case "PERSIST":
			if len(args) > 1 {
				setDirty(c)
				c.WriteError(msgSyntaxError)
				return
			}
			opts.persist = true
		case "PX", "PXAT":
			timeUnit = time.Millisecond
			fallthrough
		case "EX", "EXAT":
			if len(args) != 2 {
				setDirty(c)
				c.WriteError(msgSyntaxError)
				return
			}
			expire, err := strconv.Atoi(args[1])
			if err != nil {
				setDirty(c)
				c.WriteError(msgInvalidInt)
				return
			}
			if expire <= 0 {
				setDirty(c)
				c.WriteError(msgInvalidSETime)
				return
			}

			if arg == "PXAT" || arg == "EXAT" {
				opts.ttl = m.at(expire, timeUnit)
			} else {
				opts.ttl = time.Duration(expire) * timeUnit
			}
		default:
			setDirty(c)
			c.WriteError(msgSyntaxError)
			return
		}
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if !db.exists(opts.key) {
			c.WriteNull()
			return
		}
		switch {
		case opts.persist:
			delete(db.ttl, opts.key)
		case opts.ttl != 0:
			db.ttl[opts.key] = opts.ttl
		}

		if db.t(opts.key) != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		c.WriteBulk(db.stringGet(opts.key))
	})
}

// GETSET
func (m *Miniredis) cmdGetset(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	key, value := args[0], args[1]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		old, ok := db.stringKeys[key]
		db.stringSet(key, value)
		// a GETSET clears the ttl
		delete(db.ttl, key)

		if !ok {
			c.WriteNull()
			return
		}
		c.WriteBulk(old)
	})
}

// GETDEL
func (m *Miniredis) cmdGetdel(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(1)) {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		key := args[0]

		if !db.exists(key) {
			c.WriteNull()
			return
		}

		if db.t(key) != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v := db.stringGet(key)
		db.del(key, true)
		c.WriteBulk(v)
	})
}

// MGET
func (m *Miniredis) cmdMget(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(1)) {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		c.WriteLen(len(args))
		for _, k := range args {
			if t, ok := db.keys[k]; !ok || t != keyTypeString {
				c.WriteNull()
				continue
			}
			v, ok := db.stringKeys[k]
			if !ok {
				// Should not happen, we just checked keys[]
				c.WriteNull()
				continue
			}
			c.WriteBulk(v)
		}
	})
}

// INCR
func (m *Miniredis) cmdIncr(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(1)) {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		key := args[0]
		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}
		v, err := db.stringIncr(key, +1)
		if err != nil {
			c.WriteError(err.Error())
			return
		}
		// Don't touch TTL
		c.WriteInt(v)
	})
}

// INCRBY
func (m *Miniredis) cmdIncrby(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	var opts struct {
		key   string
		delta int
	}
	opts.key = args[0]
	if ok := optInt(c, args[1], &opts.delta); !ok {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v, err := db.stringIncr(opts.key, opts.delta)
		if err != nil {
			c.WriteError(err.Error())
			return
		}
		// Don't touch TTL
		c.WriteInt(v)
	})
}

// INCRBYFLOAT
func (m *Miniredis) cmdIncrbyfloat(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	key := args[0]
	delta, _, err := big.ParseFloat(args[1], 10, 128, 0)
	if err != nil {
		setDirty(c)
		c.WriteError(msgInvalidFloat)
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v, err := db.stringIncrfloat(key, delta)
		if err != nil {
			c.WriteError(err.Error())
			return
		}
		// Don't touch TTL
		c.WriteBulk(formatBig(v))
	})
}

// DECR
func (m *Miniredis) cmdDecr(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(1)) {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		key := args[0]
		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}
		v, err := db.stringIncr(key, -1)
		if err != nil {
			c.WriteError(err.Error())
			return
		}
		// Don't touch TTL
		c.WriteInt(v)
	})
}

// DECRBY
func (m *Miniredis) cmdDecrby(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	var opts struct {
		key   string
		delta int
	}
	opts.key = args[0]
	if ok := optInt(c, args[1], &opts.delta); !ok {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v, err := db.stringIncr(opts.key, -opts.delta)
		if err != nil {
			c.WriteError(err.Error())
			return
		}
		// Don't touch TTL
		c.WriteInt(v)
	})
}

// STRLEN
func (m *Miniredis) cmdStrlen(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(1)) {
		return
	}

	key := args[0]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		c.WriteInt(len(db.stringKeys[key]))
	})
}

// APPEND
func (m *Miniredis) cmdAppend(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	key, value := args[0], args[1]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		newValue := db.stringKeys[key] + value
		db.stringSet(key, newValue)

		c.WriteInt(len(newValue))
	})
}

// GETRANGE
func (m *Miniredis) cmdGetrange(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(3)) {
		return
	}

	var opts struct {
		key   string
		start int
		end   int
	}
	opts.key = args[0]
	if ok := optInt(c, args[1], &opts.start); !ok {
		return
	}
	if ok := optInt(c, args[2], &opts.end); !ok {
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v := db.stringKeys[opts.key]
		c.WriteBulk(withRange(v, opts.start, opts.end))
	})
}

// SETRANGE
func (m *Miniredis) cmdSetrange(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(3)) {
		return
	}

	var opts struct {
		key   string
		pos   int
		subst string
	}
	opts.key = args[0]
	if ok := optInt(c, args[1], &opts.pos); !ok {
		return
	}
	if opts.pos < 0 {
		setDirty(c)
		c.WriteError("ERR offset is out of range")
		return
	}
	opts.subst = args[2]

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		v := []byte(db.stringKeys[opts.key])
		end := opts.pos + len(opts.subst)
		if len(v) < end {
			newV := make([]byte, end)
			copy(newV, v)
			v = newV
		}
		copy(v[opts.pos:end], opts.subst)
		db.stringSet(opts.key, string(v))
		c.WriteInt(len(v))
	})
}

// BITCOUNT
func (m *Miniredis) cmdBitcount(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(1)) {
		return
	}

	var opts struct {
		useRange bool
		start    int
		end      int
		key      string
	}
	opts.key, args = args[0], args[1:]
	if len(args) >= 2 {
		opts.useRange = true
		if ok := optInt(c, args[0], &opts.start); !ok {
			return
		}
		if ok := optInt(c, args[1], &opts.end); !ok {
			return
		}
		args = args[2:]
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if !db.exists(opts.key) {
			c.WriteInt(0)
			return
		}
		if db.t(opts.key) != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}

		// Real redis only checks after it knows the key is there and a string.
		if len(args) != 0 {
			c.WriteError(msgSyntaxError)
			return
		}

		v := db.stringKeys[opts.key]
		if opts.useRange {
			v = withRange(v, opts.start, opts.end)
		}

		c.WriteInt(countBits([]byte(v)))
	})
}

// BITOP
func (m *Miniredis) cmdBitop(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, atLeast(3)) {
		return
	}

	var opts struct {
		op     string
		target string
		input  []string
	}
	opts.op = strings.ToUpper(args[0])
	opts.target = args[1]
	opts.input = args[2:]

	// 'op' is tested when the transaction is executed.
	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		switch opts.op {
		case "AND", "OR", "XOR":
			first := opts.input[0]
			if t, ok := db.keys[first]; ok && t != keyTypeString {
				c.WriteError(msgWrongType)
				return
			}
			res := []byte(db.stringKeys[first])
			for _, vk := range opts.input[1:] {
				if t, ok := db.keys[vk]; ok && t != keyTypeString {
					c.WriteError(msgWrongType)
					return
				}
				v := db.stringKeys[vk]
				cb := map[string]func(byte, byte) byte{
					"AND": func(a, b byte) byte { return a & b },
					"OR":  func(a, b byte) byte { return a | b },
					"XOR": func(a, b byte) byte { return a ^ b },
				}[opts.op]
				res = sliceBinOp(cb, res, []byte(v))
			}
			db.del(opts.target, false) // Keep TTL
			if len(res) == 0 {
				db.del(opts.target, true)
			} else {
				db.stringSet(opts.target, string(res))
			}
			c.WriteInt(len(res))
		case "NOT":
			// NOT only takes a single argument.
			if len(opts.input) != 1 {
				c.WriteError("ERR BITOP NOT must be called with a single source key.")
				return
			}
			key := opts.input[0]
			if t, ok := db.keys[key]; ok && t != keyTypeString {
				c.WriteError(msgWrongType)
				return
			}
			value := []byte(db.stringKeys[key])
			for i := range value {
				value[i] = ^value[i]
			}
			db.del(opts.target, false) // Keep TTL
			if len(value) == 0 {
				db.del(opts.target, true)
			} else {
				db.stringSet(opts.target, string(value))
			}
			c.WriteInt(len(value))
		default:
			c.WriteError(msgSyntaxError)
		}
	})
}

// BITPOS
func (m *Miniredis) cmdBitpos(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, between(2, 4)) {
		return
	}

	var opts struct {
		Key     string
		Bit     int
		Start   int
		End     int
		WithEnd bool
	}

	opts.Key = args[0]
	if ok := optInt(c, args[1], &opts.Bit); !ok {
		return
	}
	if len(args) > 2 {
		if ok := optInt(c, args[2], &opts.Start); !ok {
			return
		}
	}
	if len(args) > 3 {
		if ok := optInt(c, args[3], &opts.End); !ok {
			return
		}
		opts.WithEnd = true
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.Key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		} else if !ok {
			// non-existing key behaves differently
			if opts.Bit == 0 {
				c.WriteInt(0)
			} else {
				c.WriteInt(-1)
			}
			return
		}
		value := db.stringKeys[opts.Key]
		start := opts.Start
		end := opts.End
		if start < 0 {
			start += len(value)
			if start < 0 {
				start = 0
			}
		}
		if start > len(value) {
			start = len(value)
		}

		if opts.WithEnd {
			if end < 0 {
				end += len(value)
			}
			if end < 0 {
				end = 0
			}
			end++ // +1 for redis end semantics
			if end > len(value) {
				end = len(value)
			}
		} else {
			end = len(value)
		}

		if start != 0 || opts.WithEnd {
			if end < start {
				value = ""
			} else {
				value = value[start:end]
			}
		}
		pos := bitPos([]byte(value), opts.Bit == 1)
		if pos >= 0 {
			pos += start * 8
		}
		// Special case when looking for 0, but not when start and end are
		// given.
		if opts.Bit == 0 && pos == -1 && !opts.WithEnd && len(value) > 0 {
			pos = start*8 + len(value)*8
		}
		c.WriteInt(pos)
	})
}

// GETBIT
func (m *Miniredis) cmdGetbit(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(2)) {
		return
	}

	var opts struct {
		key string
		bit int
	}
	opts.key = args[0]
	if ok := optIntErr(c, args[1], &opts.bit, "ERR bit offset is not an integer or out of range"); !ok {
		return
	}
	if opts.bit < 0 {
		setDirty(c)
		c.WriteError("ERR bit offset is not an integer or out of range")
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}
		value := db.stringKeys[opts.key]

		ourByteNr := opts.bit / 8
		var ourByte byte
		if ourByteNr > len(value)-1 {
			ourByte = '\x00'
		} else {
			ourByte = value[ourByteNr]
		}
		res := 0
		if toBits(ourByte)[opts.bit%8] {
			res = 1
		}
		c.WriteInt(res)
	})
}

// SETBIT
func (m *Miniredis) cmdSetbit(c *server.Peer, cmd string, args []string) {
	if !m.isValidCMD(c, cmd, args, exactly(3)) {
		return
	}

	var opts struct {
		key    string
		bit    int
		newBit int
	}
	opts.key = args[0]
	if ok := optIntErr(c, args[1], &opts.bit, "ERR bit offset is not an integer or out of range"); !ok {
		return
	}
	if opts.bit < 0 {
		setDirty(c)
		c.WriteError("ERR bit offset is not an integer or out of range")
		return
	}
	if ok := optIntErr(c, args[2], &opts.newBit, "ERR bit is not an integer or out of range"); !ok {
		return
	}
	if opts.newBit != 0 && opts.newBit != 1 {
		setDirty(c)
		c.WriteError("ERR bit is not an integer or out of range")
		return
	}

	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
		db := m.db(ctx.selectedDB)

		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
			c.WriteError(msgWrongType)
			return
		}
		value := []byte(db.stringKeys[opts.key])

		ourByteNr := opts.bit / 8
		ourBitNr := opts.bit % 8
		if ourByteNr > len(value)-1 {
			// Too short. Expand.
			newValue := make([]byte, ourByteNr+1)
			copy(newValue, value)
			value = newValue
		}
		old := 0
		if toBits(value[ourByteNr])[ourBitNr] {
			old = 1
		}
		if opts.newBit == 0 {
			value[ourByteNr] &^= 1 << uint8(7-ourBitNr)
		} else {
			value[ourByteNr] |= 1 << uint8(7-ourBitNr)
		}
		db.stringSet(opts.key, string(value))

		c.WriteInt(old)
	})
}

// Redis range. both start and end can be negative.
func withRange(v string, start, end int) string {
	s, e := redisRange(len(v), start, end, true /* string getrange symantics */)
	return v[s:e]
}

func countBits(v []byte) int {
	count := 0
	for _, b := range []byte(v) {
		for b > 0 {
			count += int((b % uint8(2)))
			b = b >> 1
		}
	}
	return count
}

// sliceBinOp applies an operator to all slice elements, with Redis string
// padding logic.
func sliceBinOp(f func(a, b byte) byte, a, b []byte) []byte {
	maxl := len(a)
	if len(b) > maxl {
		maxl = len(b)
	}
	lA := make([]byte, maxl)
	copy(lA, a)
	lB := make([]byte, maxl)
	copy(lB, b)
	res := make([]byte, maxl)
	for i := range res {
		res[i] = f(lA[i], lB[i])
	}
	return res
}

// Return the number of the first bit set/unset.
func bitPos(s []byte, bit bool) int {
	for i, b := range s {
		for j, set := range toBits(b) {
			if set == bit {
				return i*8 + j
			}
		}
	}
	return -1
}

// toBits changes a byte in 8 bools.
func toBits(s byte) [8]bool {
	r := [8]bool{}
	for i := range r {
		if s&(uint8(1)<<uint8(7-i)) != 0 {
			r[i] = true
		}
	}
	return r
}
