package core

import (
	"bytes"
	"encoding/gob"
	"errors"
	"fmt"
	"log"
	"math"
	"math/big"
	"os"
	"strconv"
	"strings"
)

type Pos int
type Bytecode byte

const (
	// InstructionReturn return to previous call pointer
	InstructionReturn Bytecode = iota
	// InstructionPop pop and delete the first item on the stack
	InstructionPop

	// InstructionAddFloat pop two floats and add them
	InstructionAddFloat
	// InstructionSubFloat pop two floats and subtract the second from the first
	InstructionSubFloat
	// InstructionMulFloat pop two floats and multiply them
	InstructionMulFloat
	// InstructionDivFloat pop two floats and divide the second by the first
	InstructionDivFloat
	// InstructionNegateFloat negate the float; if it was positive, make it negative, and vice versa.
	InstructionNegateFloat

	// InstructionAddInt pop two ints and add them
	InstructionAddInt
	// InstructionSubInt pop two ints and subtract the second from the first
	InstructionSubInt
	// InstructionMulInt pop two ints and multiply them
	InstructionMulInt
	// InstructionDivInt pop two ints and divide the second by the first
	InstructionDivInt
	// InstructionModInt pop two ints and compute the modulo of the first by the second
	InstructionModInt
	// InstructionNegateInt negate the int; if it was positive, make it negative, and vice versa.
	InstructionNegateInt

	// InstructionEquals whether the two top values on the stack are equal
	InstructionEquals
	// InstructionNotEqual whether the two top values on the stack are not equal
	InstructionNotEqual
	// InstructionNot inverts boolean (true => false, false => true)
	InstructionNot

	// InstructionLessFloat pops two from stack, pushes whether the lowest is less than the highest
	InstructionLessFloat
	// InstructionLessOrEqualFloat pops two from stack, pushes whether the lowest is less or equal than the highest
	InstructionLessOrEqualFloat
	// InstructionGreaterFloat pops two from stack, pushes whether the lowest is greater than the highest
	InstructionGreaterFloat
	// InstructionGreaterOrEqualFloat pops two from stack, pushes whether the lowest is greater or equal than the highest
	InstructionGreaterOrEqualFloat

	// InstructionLessInt pops two from stack, pushes whether the lowest is less than the highest
	InstructionLessInt
	// InstructionLessOrEqualInt pops two from stack, pushes whether the lowest is less or equal than the highest
	InstructionLessOrEqualInt
	// InstructionGreaterInt pops two from stack, pushes whether the lowest is greater than the highest
	InstructionGreaterInt
	// InstructionGreaterOrEqualInt pops two from stack, pushes whether the lowest is greater or equal than the highest
	InstructionGreaterOrEqualInt

	// InstructionAccessProperty gets a property from a value, and pops it onto the stack
	InstructionAccessProperty
	// InstructionCall pops a function object from the stack and begins execution of the chunk
	InstructionCall

	// InstructionDescend increase the scope depth
	InstructionDescend
	// InstructionAscend decrease the scope depth, and remove all variables on the stack which belong in a higher scope
	InstructionAscend

	// InstructionJump jump forwards by the value of the next two bytes as a u16
	InstructionJump
	// InstructionJumpFalse jump by the value of the two next bytes as an unsigned integer if the first value (popped) from the stack is false
	InstructionJumpFalse
	// InstructionLoop jump by the value of the two next bytes as an unsigned integer backwards if the first value (popped) from the stack is true
	InstructionLoop

	// InstructionGetLocal Push a constant to the stack (2 bytes, second = constant index)
	InstructionGetLocal
	// InstructionSetLocal Set a local variable
	InstructionSetLocal
	// InstructionDeclareLocal Declare a new local variable in the uppermost scope
	InstructionDeclareLocal
	// InstructionGetGlobal Set a global variable (the next byte is the index of the constant with the name of the variable
	InstructionGetGlobal
	// InstructionSetGlobal Push a constant to the stack (2 bytes, second = constant index)
	InstructionSetGlobal

	// InstructionStringConversion Take the top value on the stack and convert it to a string
	InstructionStringConversion
	// InstructionConcatStrings Add two strings together, with the second value on the stack as left and the top as right
	InstructionConcatStrings

	// InstructionSwap swap the two top items on the stack (1, 2 -> 2, 1)
	InstructionSwap
	// InstructionDuplicate push a copy of the item on top of the stack (1 -> 1, 1)
	InstructionDuplicate

	// InstructionAnd pop two booleans and push true if both are true
	InstructionAnd
	// InstructionOr pop two booleans and push true if either are true
	InstructionOr

	// InstructionConstant Push a constant to the stack (2 bytes, second = constant index)
	InstructionConstant
	// InstructionTrue Push a true literal to the stack
	InstructionTrue
	// InstructionFalse Push a false literal to the stack
	InstructionFalse
	// InstructionNil Push a nil literal to the stack
	InstructionNil

	// InstructionAppend Append to a list. stack: (... > list > item) => (... > list)
	InstructionAppend
	// InstructionFormList Form items on the stack into a list. The 2 bytes after the instructions are the amount of
	// items to include. The order is reversed compared to on the stack; the top value on the stack is the last in the
	// list.
	InstructionFormList
	// InstructionConcatLists concatenate lists, producing a new list with the values of both lists. Pops two lists.
	InstructionConcatLists

	// InstructionFormTuple pop n+1 (u16) items from the stack, and create a new tuple with the items. The top value
	// on the stack is the last value in the tuple.
	InstructionFormTuple
	// InstructionDestructureTuple pop a tuple, and push all its items to the stack, with the top item on the stack
	// being the last item in the tuple.
	InstructionDestructureTuple

	// InstructionNewRecord Create a new empty record.
	InstructionNewRecord
	// InstructionSetRecordItem Set the value of an item in the record, and create it if it does not already exist.
	// [..., record, item]; the following byte should be the index of a string constant with the name of the property.
	InstructionSetRecordItem

	// InstructionIndexList index into a list. The lower item is the container, and the top item
	// is the index. [..., container, index] -> [..., item]
	InstructionIndexList
	// InstructionIndexTuple index into a tuple. The lower item is the container, and the top item
	// is the index. [..., container, index] -> [..., item]
	InstructionIndexTuple
	// InstructionIndexString index into a string. The lower item is the container, and the top item
	// is the index. [..., container, index] -> [..., item]. Produces a new string with only the character
	// at the indexed position
	InstructionIndexString

	// InstructionSetIndexList set the item at a given index in a list.
	// [..., item, container, index] -> [..., item]
	InstructionSetIndexList

	// InstructionBreakpoint for debugging purposes
	InstructionBreakpoint
)

func (b Bytecode) String() string {
	switch b {
	case InstructionReturn:
		return "RETURN"
	case InstructionPop:
		return "POP"
	case InstructionAddFloat:
		return "ADD_FLOAT"
	case InstructionSubFloat:
		return "SUB_FLOAT"
	case InstructionMulFloat:
		return "MUL_FLOAT"
	case InstructionDivFloat:
		return "DIV_FLOAT"
	case InstructionNegateFloat:
		return "NEGATE_FLOAT"
	case InstructionAddInt:
		return "ADD_INT"
	case InstructionSubInt:
		return "SUB_INT"
	case InstructionMulInt:
		return "MUL_INT"
	case InstructionDivInt:
		return "DIV_INT"
	case InstructionNegateInt:
		return "NEGATE_INT"
	case InstructionEquals:
		return "EQUALS"
	case InstructionNotEqual:
		return "NOT_EQUALS"
	case InstructionNot:
		return "NOT"
	case InstructionLessFloat:
		return "LESS_FLOAT"
	case InstructionLessOrEqualFloat:
		return "LESS_OR_EQUAL_FLOAT"
	case InstructionGreaterFloat:
		return "GREATER_FLOAT"
	case InstructionGreaterOrEqualFloat:
		return "GREATER_OR_EQUAL_FLOAT"
	case InstructionLessInt:
		return "LESS_INT"
	case InstructionLessOrEqualInt:
		return "LESS_OR_EQUAL_INT"
	case InstructionGreaterInt:
		return "GREATER_INT"
	case InstructionGreaterOrEqualInt:
		return "GREATER_OR_EQUAL_INT"
	case InstructionJump:
		return "JUMP"
	case InstructionJumpFalse:
		return "JUMP_FALSE"
	case InstructionLoop:
		return "LOOP"
	case InstructionConstant:
		return "CONSTANT"
	case InstructionTrue:
		return "TRUE"
	case InstructionFalse:
		return "FALSE"
	case InstructionNil:
		return "NIL"
	case InstructionGetLocal:
		return "GET_LOCAL"
	case InstructionDeclareLocal:
		return "DECLARE_LOCAL"
	case InstructionSetLocal:
		return "SET_LOCAL"
	case InstructionGetGlobal:
		return "GET_GLOBAL"
	case InstructionSetGlobal:
		return "SET_GLOBAL"
	case InstructionCall:
		return "CALL"
	case InstructionDescend:
		return "DESCEND"
	case InstructionAscend:
		return "ASCEND"
	case InstructionStringConversion:
		return "STRING_CONVERSION"
	case InstructionConcatStrings:
		return "STRING_CONCATENATION"
	case InstructionSwap:
		return "SWAP"
	case InstructionAnd:
		return "AND"
	case InstructionOr:
		return "OR"
	case InstructionFormList:
		return "FORM_LIST"
	case InstructionBreakpoint:
		return "BREAKPOINT"
	case InstructionAppend:
		return "APPEND"
	case InstructionAccessProperty:
		return "ACCESS_PROPERTY"
	case InstructionConcatLists:
		return "CONCAT_LISTS"
	case InstructionDuplicate:
		return "DUPLICATE"
	case InstructionFormTuple:
		return "FORM_TUPLE"
	case InstructionIndexList:
		return "INDEX_LIST"
	case InstructionIndexTuple:
		return "INDEX_TUPLE"
	case InstructionDestructureTuple:
		return "DESTRUCTURE_TUPLE"
	case InstructionModInt:
		return "MOD_INT"
	case InstructionNewRecord:
		return "NEW_RECORD"
	case InstructionSetRecordItem:
		return "SET_PROPERTY"
	case InstructionIndexString:
		return "INDEX_STRING"
	}
	return "UNDEFINED"
}

type Chunk struct {
	Bytecode  []Bytecode
	Constants []Value
}

func (c *Chunk) String() string {
	b := strings.Builder{}

	b.WriteString("=v= chunk =v=\n")
	for i, bc := range c.Bytecode {
		b.WriteString(fmt.Sprintf("i=%d \t%d \t(%s)\n", i, bc, bc))
	}

	b.WriteString("=-= constants =-=\n")

	for i, ct := range c.Constants {
		b.WriteString(fmt.Sprintf("c=%d \t%s\n", i, ct.DebugString()))

		f, ok := ct.(*FunctionValue)
		if ok {
			b.WriteString(f.Chunk.String())
		}
	}

	b.WriteString("=^= chunk =^=\n")

	return b.String()
}

func (c *Chunk) Equals(other *Chunk) bool {
	if len(c.Bytecode) != len(other.Bytecode) {
		return false
	}

	for i, bc := range c.Bytecode {
		if other.Bytecode[i] != bc {
			return false
		}
	}

	if len(c.Constants) != len(other.Constants) {
		return false
	}

	for i := 0; i < len(c.Constants); i++ {
		if other.Constants[i] != c.Constants[i] {
			return false
		}
	}

	return true
}

func NewChunk(bytecode []Bytecode, constants []Value) *Chunk {
	return &Chunk{bytecode, constants}
}

func RegisterGOBTypes() {
	gob.Register(&StringValue{""})
	gob.Register(&BoolValue{false})
	gob.Register(&FloatValue{0})
	gob.Register(&FunctionValue{
		Name:   "",
		Params: nil,
		Chunk:  nil,
	})

	// Signatures
	gob.Register(&NilSignature{})
	gob.Register(&FloatSignature{})
	gob.Register(&StringSignature{})
	gob.Register(&FunctionSignature{})
	gob.Register(&ListSignature{})
	gob.Register(&ObjectSignature{})
	gob.Register(&BooleanSignature{})

}

func (c *Chunk) Serialize() []byte {
	b := bytes.Buffer{}

	e := gob.NewEncoder(&b)

	err := e.Encode(c)
	if err != nil {
		log.Fatal(err)
	}

	return b.Bytes()
}

func DeserializeChunk(b []byte) *Chunk {
	m := Chunk{}

	buf := bytes.Buffer{}
	buf.Write(b)

	d := gob.NewDecoder(&buf)

	err := d.Decode(&m)

	if err != nil {
		log.Fatal(err)
	}

	return &m
}

type VM struct {
	// Replace with chunk of bytecode
	chunk *Chunk

	// instruction pointer
	ip Pos

	// global variable storage
	globals map[string]Value
	// local variable storage
	scope *Scope

	Stack *Stack[Value]
	call  *Stack[Call]
}

type Scope struct {
	current map[string]Value
	parent  *Scope
}

type Call struct {
	chunk *Chunk
	ip    Pos
	scope *Scope
}

var DefaultGlobals = map[string]Value{
	"println": &BuiltinFunctionValue{
		"write", // always remember where you come from...
		&FunctionSignature{
			[]TypeSignature{&AnySignature{}},
			&NilSignature{},
		},
		func(_ *VM, this Value, v []Value) (Value, error) {
			println(v[0].String())
			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"print": &BuiltinFunctionValue{
		"print",
		&FunctionSignature{
			[]TypeSignature{&AnySignature{}},
			&NilSignature{},
		},
		func(_ *VM, this Value, v []Value) (Value, error) {
			print(v[0].String())
			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"format": &BuiltinFunctionValue{
		"format",
		&FunctionSignature{
			[]TypeSignature{
				&StringSignature{},
				&ListSignature{
					&AnySignature{},
				},
			},
			&StringSignature{},
		},
		func(vm *VM, value Value, m []Value) (Value, error) {
			b := strings.Builder{}
			template := m[0].(*StringValue).Text
			valuies := m[1].(*ListValue).Items

			vi := 0
			last := 0
			for i := 0; i < len(template); i++ {
				if template[i] == '%' {
					b.WriteString(template[last:i])
					b.WriteString(valuies[vi].String())
					vi++
					last = i + 1
				}
			}

			b.WriteString(template[last:])

			return GoToValue(b.String()), nil
		},
		nil,
		true,
	},
	"char": &BuiltinFunctionValue{
		"char",
		&FunctionSignature{
			[]TypeSignature{&IntegerSignature{}},
			&StringSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			n := args[0].(*IntegerValue).Number
			b := n.Bytes()[0]

			return &StringValue{
				string([]byte{b}),
			}, nil
		},
		nil,
		true,
	},
	"byte": &BuiltinFunctionValue{
		"byte",
		&FunctionSignature{
			[]TypeSignature{&StringSignature{}},
			&IntegerSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			s := args[0].(*StringValue).Text
			n := new(big.Int).SetBytes([]byte(s))

			return &IntegerValue{n}, nil
		},
		nil,
		true,
	},
	"assert": &BuiltinFunctionValue{
		"assert",
		&FunctionSignature{
			[]TypeSignature{
				&BooleanSignature{},
			},
			&NilSignature{},
		},
		func(vm *VM, this Value, params []Value) (Value, error) {
			b := params[0].(*BoolValue)

			if !b.Boolean {
				return nil, errors.New(fmt.Sprintf("assertion failed: %s", b))
			}

			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"assertEq": &BuiltinFunctionValue{
		"assertEq",
		&FunctionSignature{
			[]TypeSignature{
				&AnySignature{},
				&AnySignature{},
			},
			&NilSignature{},
		},
		func(vm *VM, this Value, params []Value) (Value, error) {
			a := params[0]
			b := params[1]

			if !a.Equals(b) {
				return nil, errors.New(fmt.Sprintf("assertion failed: %s does not equal %s", a, b))
			}

			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"assertNotEq": &BuiltinFunctionValue{
		"assertNotEq",
		&FunctionSignature{
			[]TypeSignature{
				&AnySignature{},
				&AnySignature{},
			},
			&NilSignature{},
		},
		func(vm *VM, this Value, params []Value) (Value, error) {
			a := params[0]
			b := params[1]

			if a.Equals(b) {
				return nil, errors.New(fmt.Sprintf("assertion failed: %s does not equal %s", a, b))
			}

			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"str": &BuiltinFunctionValue{
		"str",
		&FunctionSignature{
			[]TypeSignature{&AnySignature{}},
			&StringSignature{},
		},
		func(vm *VM, _ Value, args []Value) (Value, error) {
			return GoToValue(args[0].String()), nil
		},
		nil,
		true,
	},
	"int": &BuiltinFunctionValue{
		"int",
		&FunctionSignature{
			[]TypeSignature{
				quickComposite(
					&IntegerSignature{},
					&FloatSignature{},
					&StringSignature{},
				),
			},
			&CompositeSignature{
				&IntegerSignature{},
				&NilSignature{},
			},
		},
		func(vm *VM, _ Value, args []Value) (Value, error) {
			switch v := args[0].(type) {
			case *IntegerValue:
				return &IntegerValue{v.Number}, nil // this might need to clone the value instead
			case *FloatValue:
				n := new(big.Int).SetInt64(int64(v.Number))
				return &IntegerValue{n}, nil
			case *StringValue:
				n, success := new(big.Int).SetString(v.Text, 0) // determine base
				if !success {
					return &NilValue{}, nil
				}

				return &IntegerValue{n}, nil
			default:
				return nil, errors.New(fmt.Sprintf("%s cannot become an integer (undefined)", v))
			}
		},
		nil,
		true,
	},
	"float": &BuiltinFunctionValue{
		"float",
		&FunctionSignature{
			[]TypeSignature{
				quickComposite(
					&FloatSignature{},
					&IntegerSignature{},
					&StringSignature{},
				),
			},
			&FloatSignature{},
		},
		func(vm *VM, _ Value, args []Value) (Value, error) {
			switch v := args[0].(type) {
			case *IntegerValue:
				n, _ := v.Number.Float64()
				return &FloatValue{n}, nil
			case *FloatValue:
				return v.Copy(), nil
			case *StringValue:
				num, err := strconv.ParseFloat(v.Text, FloatSize)
				if err != nil {
					return &FloatValue{}, nil
				}

				return &FloatValue{num}, nil
			default:
				return nil, errors.New(fmt.Sprintf("%s cannot become an integer (undefined)", v))
			}
		},
		nil,
		true,
	},
	"typeof": &BuiltinFunctionValue{
		Name: "typeof",
		Signature: &FunctionSignature{
			In:  []TypeSignature{&AnySignature{}},
			Out: &StringSignature{},
		},
		F: func(vm *VM, this Value, args []Value) (Value, error) {
			v := args[0]
			sig := SignatureOf(v)

			return GoToValue(sig.String()), nil
		},
		Constant: true,
	},
	"exit": &BuiltinFunctionValue{
		"exit",
		&FunctionSignature{
			[]TypeSignature{&FloatSignature{}},
			&NilSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			os.Exit(int(args[0].(*FloatValue).Number))
			return &NilValue{}, nil
		},
		nil,
		false,
	},
	"floor": &BuiltinFunctionValue{
		"floor",
		&FunctionSignature{
			[]TypeSignature{&FloatSignature{}},
			&FloatSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			return &FloatValue{math.Floor(args[0].(*FloatValue).Number)}, nil
		},
		nil,
		true,
	},
	"ceil": &BuiltinFunctionValue{
		"ceil",
		&FunctionSignature{
			[]TypeSignature{&FloatSignature{}},
			&FloatSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			return &FloatValue{math.Ceil(args[0].(*FloatValue).Number)}, nil
		},
		nil,
		true,
	},
	"roundd": &BuiltinFunctionValue{
		"roundd",
		&FunctionSignature{
			[]TypeSignature{&FloatSignature{}, &IntegerSignature{}},
			&FloatSignature{},
		},
		func(vm *VM, this Value, args []Value) (Value, error) {
			x := args[0].(*FloatValue).Number
			decimals, _ := args[1].(*IntegerValue).Number.Float64()
			multiplier := math.Pow(10, decimals)
			return &FloatValue{math.Round(x*multiplier) / multiplier}, nil
		},
		nil,
		true,
	},
}

func NewVM(chunk *Chunk, stackSize Pos, callstackSize Pos) *VM {
	vm := &VM{
		chunk: chunk,
		Stack: NewStack[Value](stackSize),
		call:  NewStack[Call](callstackSize),

		globals: DefaultGlobals,
		scope: &Scope{
			current: map[string]Value{},
		},
	}

	return vm
}

// Next execute instruction
// returns true if more instructions should be executed
func (vm *VM) Next() bool {
	if !vm.HasNext() {
		return false
	}

	switch vm.NextByte() {
	case InstructionReturn:
		if vm.call.Current == 0 {
			return false
		}

		v := vm.Stack.Pop()
		c := vm.call.Pop()

		// reset stack current and variable end and scope
		vm.scope = c.scope

		// reset to calling position
		vm.ip = c.ip
		vm.chunk = c.chunk

		vm.Stack.Push(v)

	case InstructionPop:
		vm.Stack.Pop()

	case InstructionConstant:
		c := vm.ReadConstant()

		if c, ok := c.(*FunctionValue); ok {
			c.Scope = vm.scope
		}

		vm.Stack.Push(c)

	case InstructionAddFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&FloatValue{l + r})

	case InstructionSubFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&FloatValue{l - r})

	case InstructionMulFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&FloatValue{l * r})

	case InstructionDivFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&FloatValue{l / r})

	case InstructionNegateFloat:
		v := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&FloatValue{-v})

	case InstructionAddInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Add(l, r)})

	case InstructionSubInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Sub(l, r)})

	case InstructionMulInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Mul(l, r)})

	case InstructionDivInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Div(l, r)})

	case InstructionModInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Mod(l, r)})

	case InstructionNegateInt:
		v := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&IntegerValue{new(big.Int).Neg(v)})

	case InstructionEquals:
		vm.Stack.Push(
			&BoolValue{vm.Stack.Pop().Equals(vm.Stack.Pop())},
		)

	case InstructionNotEqual:
		vm.Stack.Push(
			&BoolValue{!vm.Stack.Pop().Equals(vm.Stack.Pop())},
		)

	case InstructionNot:
		b := vm.Stack.Pop().(*BoolValue).Boolean
		vm.Stack.Push(&BoolValue{!b})

	case InstructionAnd:
		r := vm.Stack.Pop().(*BoolValue).Boolean
		l := vm.Stack.Pop().(*BoolValue).Boolean
		vm.Stack.Push(&BoolValue{l && r})

	case InstructionOr:
		r := vm.Stack.Pop().(*BoolValue).Boolean
		l := vm.Stack.Pop().(*BoolValue).Boolean
		vm.Stack.Push(&BoolValue{l || r})

	case InstructionLessFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&BoolValue{l < r})

	case InstructionLessOrEqualFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&BoolValue{l <= r})

	case InstructionGreaterFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&BoolValue{l > r})

	case InstructionGreaterOrEqualFloat:
		r := vm.Stack.Pop().(*FloatValue).Number
		l := vm.Stack.Pop().(*FloatValue).Number

		vm.Stack.Push(&BoolValue{l >= r})

	case InstructionLessInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&BoolValue{l.Cmp(r) == -1})

	case InstructionLessOrEqualInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&BoolValue{l.Cmp(r) != 1})

	case InstructionGreaterInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&BoolValue{l.Cmp(r) == 1})

	case InstructionGreaterOrEqualInt:
		r := vm.Stack.Pop().(*IntegerValue).Number
		l := vm.Stack.Pop().(*IntegerValue).Number

		vm.Stack.Push(&BoolValue{l.Cmp(r) != -1})

	case InstructionCall:
		v := vm.Stack.Pop()
		switch f := v.(type) {
		case *FunctionValue:
			vm.call.Push(Call{
				chunk: vm.chunk,
				ip:    vm.ip,
				scope: vm.scope,
			})

			vm.scope = f.Scope
			vm.descend()

			for i := len(f.Params) - 1; i >= 0; i-- {
				vm.addVar(f.Params[i].Name, vm.Stack.Pop())
			}

			if f.Parent != nil {
				vm.addVar("this", f.Parent)
			}

			vm.chunk = f.Chunk
			vm.ip = 0
		case *BuiltinFunctionValue:
			args := make([]Value, len(f.Signature.In))

			for i := len(f.Signature.In) - 1; i >= 0; i-- {
				args[i] = vm.Stack.Pop()
			}

			v, err := f.F(vm, f.Parent, args)
			if err != nil {
				vm.error(err.Error())
			}

			if v == nil {
				v = &NilValue{}
			}

			vm.Stack.Push(v)
		default:
			vm.error(fmt.Sprintf("%s (%s) is not callable ", v.DebugString(), v.Type()))
			return false
		}

	case InstructionJump:
		vm.ip += Pos(vm.NextU16())

	case InstructionLoop:
		vm.ip -= Pos(vm.NextU16())

	case InstructionJumpFalse:
		n := vm.NextU16()
		if !vm.Stack.Pop().(*BoolValue).Boolean {
			vm.ip += Pos(n)
		}

	case InstructionGetLocal:
		name := vm.GetConstant(vm.NextByte()).(*StringValue).Text
		v := vm.getVar(name)

		if v == nil {
			vm.error(fmt.Sprintf("cannot get local: undefined variable %s", name))
			return false
		}

		vm.Stack.Push(v)

	case InstructionSetLocal:
		value := vm.Stack.Peek().Copy()
		name := vm.GetConstant(vm.NextByte()).(*StringValue).Text

		vm.setVar(name, value)

	case InstructionDeclareLocal:
		vm.addVar(
			vm.GetConstant(vm.NextByte()).(*StringValue).Text,
			vm.Stack.Peek().Copy(),
		)

	case InstructionGetGlobal:
		vm.Stack.Push(vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).Text])

	case InstructionSetGlobal:
		vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).Text] = vm.Stack.Pop()

	case InstructionTrue:
		vm.Stack.Push(&BoolValue{true})

	case InstructionFalse:
		vm.Stack.Push(&BoolValue{false})

	case InstructionNil:
		vm.Stack.Push(&NilValue{})

	case InstructionFormList:
		n := int(vm.NextU16())

		items := make([]Value, n)
		for i := n - 1; i >= 0; i-- {
			items[i] = vm.Stack.Pop()
		}

		vm.Stack.Push(&ListValue{
			items,
		})

	case InstructionAppend:
		value := vm.Stack.Pop()
		list := vm.Stack.Pop().(*ListValue)
		list.Items = append(list.Items, value)
		vm.Stack.Push(list)

	case InstructionConcatLists:
		r := vm.Stack.Pop().(*ListValue)
		l := vm.Stack.Pop().(*ListValue)

		vm.Stack.Push(&ListValue{
			append(l.Items, r.Items...),
		})

	case InstructionFormTuple:
		n := int(vm.NextU16())

		items := make([]Value, n)
		for i := n - 1; i >= 0; i-- {
			items[i] = vm.Stack.Pop()
		}

		vm.Stack.Push(&TupleValue{
			items,
		})

	case InstructionDestructureTuple:
		t := vm.Stack.Pop().(*TupleValue)

		vm.Stack.Push(t.Items...)

	case InstructionDescend:
		vm.descend()

	case InstructionAscend:
		vm.ascend()

	case InstructionStringConversion:
		v := vm.Stack.Pop()
		vm.Stack.Push(&StringValue{v.String()})

	case InstructionConcatStrings:
		r := vm.Stack.Pop().(*StringValue).Text
		l := vm.Stack.Pop().(*StringValue).Text

		vm.Stack.Push(&StringValue{l + r})

	case InstructionSwap:
		r := vm.Stack.Pop()
		l := vm.Stack.Pop()

		vm.Stack.Push(r, l)

	case InstructionDuplicate:
		vm.Stack.Push(vm.Stack.Peek().Copy())

	case InstructionAccessProperty:
		source := vm.Stack.Pop()
		property := vm.ReadConstant()

		member, err := source.Get(property.(*StringValue).String())
		if err != nil {
			vm.error(err.Error())
		}

		// add parent if function
		if member.Type() == FunctionValueType {
			member.(*FunctionValue).Parent = source
		} else if member.Type() == BuiltinFunctionValueType {
			member.(*BuiltinFunctionValue).Parent = source
		}

		vm.Stack.Push(member)

	case InstructionSetRecordItem:
		i := vm.Stack.Pop()
		prop := vm.ReadConstant().(*StringValue)
		r := vm.Stack.Peek().(*RecordValue)

		r.Entries[prop.Text] = i

	case InstructionNewRecord:
		vm.Stack.Push(&RecordValue{
			map[string]Value{},
		})

	case InstructionIndexList:
		i := vm.Stack.Pop().(*IntegerValue)
		l := vm.Stack.Pop().(*ListValue)

		n := int(i.Number.Int64())

		if n < 0 || len(l.Items) <= n {
			vm.error(fmt.Sprintf("index %d out of bounds", n))
		}

		vm.Stack.Push(l.Items[n].Copy())

	case InstructionIndexTuple:
		i := vm.Stack.Pop().(*IntegerValue)
		t := vm.Stack.Pop().(*TupleValue)

		n := int(i.Number.Int64())

		if n < 0 || len(t.Items) <= n {
			vm.error(fmt.Sprintf("index %d out of bounds", n))
		}

		vm.Stack.Push(t.Items[n].Copy())

	case InstructionIndexString:
		i := vm.Stack.Pop().(*IntegerValue)
		s := vm.Stack.Pop().(*StringValue)

		n := int(i.Number.Int64())

		if n < 0 || len(s.Text) <= n {
			vm.error(fmt.Sprintf("index %d out of bounds", n))
		}

		vm.Stack.Push(&StringValue{string(s.Text[n])})

	case InstructionSetIndexList:
		n := vm.Stack.Pop().(*IntegerValue)
		l := vm.Stack.Pop().(*ListValue)

		i := n.Number.Int64()

		if i < 0 || int64(len(l.Items)) <= i {
			vm.error(fmt.Sprintf("index %d out of bounds", i))
		}

		l.Items[i] = vm.Stack.Peek().Copy()

	case InstructionBreakpoint:
		/*
			// I'm keeping this
			s := vm.scope
			log.Printf("breakpoint %d", vm.ip)
			for s != nil {
				log.Printf("%s", s.current)
				s = s.parent
			}
		*/
		vm.Stack.Push(&NilValue{})

	default:
		panic("invalid byte code")
	}

	return true
}

func (vm *VM) Call(v Value, args []Value) (Value, error) {
	switch f := v.(type) {
	case *FunctionValue:
		vm.call.Push(Call{
			chunk: vm.chunk,
			ip:    vm.ip,
			scope: vm.scope,
		})

		vm.scope = f.Scope
		vm.descend()

		for i := 0; i < len(f.Params); i++ {
			vm.addVar(f.Params[i].Name, args[i])
		}

		if f.Parent != nil {
			vm.addVar("this", f.Parent)
		}

		vm.chunk = f.Chunk
		vm.ip = 0

		for vm.chunk.Bytecode[vm.ip] != InstructionReturn && vm.Next() {
		}

		vm.Next()

		return vm.Stack.Pop(), nil

	case *BuiltinFunctionValue:
		return f.F(vm, f.Parent, args)
	}

	return nil, errors.New(fmt.Sprintf("value is not a function (%s)", v.DebugString()))
}

func (vm *VM) SetChunk(c *Chunk) {
	vm.chunk = c
}

func (vm *VM) TryNextByte() (Bytecode, error) {
	if !vm.HasNext() {
		return 0, errors.New("there are no more instructions")
	}

	for int(vm.ip) >= len(vm.chunk.Bytecode) && vm.call.Current > 0 {
		c := vm.call.Pop()

		vm.ip = c.ip
		vm.chunk = c.chunk
		vm.scope = c.scope
	}

	if int(vm.ip) >= len(vm.chunk.Bytecode) {
		return 0, errors.New("there are no more instructions")
	}

	v := vm.chunk.Bytecode[vm.ip]
	vm.ip++

	return v, nil
}

func (vm *VM) NextByte() Bytecode {
	b, err := vm.TryNextByte()

	if err != nil {
		panic(err)
	}

	return b
}

func (vm *VM) ascend() {
	if vm.scope.parent == nil {
		panic("invalid scope")
	}

	vm.scope = vm.scope.parent
}

func (vm *VM) descend() {
	old := vm.scope

	vm.scope = &Scope{
		map[string]Value{},
		old,
	}
}

func (vm *VM) addVar(name string, value Value) {
	vm.scope.current[name] = value
}

func (vm *VM) getVar(name string) Value {
	s := vm.scope

	for s != nil {
		if v, ok := s.current[name]; ok {
			return v
		}

		s = s.parent
	}

	return nil
}

func (vm *VM) setVar(name string, v Value) {
	s := vm.scope

	for s != nil {
		if _, ok := s.current[name]; ok {
			s.current[name] = v
			break
		}

		s = s.parent
	}
}

func (vm *VM) HasNext() bool {
	return vm.ip < Pos(len(vm.chunk.Bytecode)) || vm.call.Current > 0
}

func (vm *VM) GetConstant(id Bytecode) Value {
	return vm.chunk.Constants[id].Copy()
}

func (vm *VM) ReadConstant() Value {
	return vm.GetConstant(vm.NextByte())
}

func (vm *VM) NextU16() uint16 {
	return (uint16(vm.NextByte()) << 8) | uint16(vm.NextByte())
}

func (vm *VM) error(error string) {
	log.Fatal(error)
}

func (vm *VM) SetGlobal(name string, value Value) {
	vm.globals[name] = value
}

func (vm *VM) GetGlobal(name string) Value {
	return vm.globals[name]
}