package object

import (
	"bytes"
	"fmt"
	"hash/fnv"
	"monkey/ast"
	"monkey/code"
	"strings"
)

type ObjectType string

const (
	INTEGER_OBJ           = "int"
	BOOLEAN_OBJ           = "bool"
	NULL_OBJ              = "null"
	RETURN_VALUE_OBJ      = "return"
	ERROR_OBJ             = "error"
	FUNCTION_OBJ          = "fn"
	STRING_OBJ            = "str"
	BUILTIN_OBJ           = "builtin"
	ARRAY_OBJ             = "array"
	HASH_OBJ              = "hash"
	COMPILED_FUNCTION_OBJ = "COMPILED_FUNCTION"
	CLOSURE_OBJ           = "closure"
)

// Comparable is the interface for comparing two Object and their underlying
// values. It is the responsibility of the caller (left) to check for types.
// Returns `true` iif the types and values are identical, `false` otherwise.
type Comparable interface {
	Equal(other Object) bool
}

// Immutable is the interface for all immutable objects which must implement
// the Clone() method used by binding names to values.
type Immutable interface {
	Clone() Object
}

type Object interface {
	Type() ObjectType
	String() string
	Inspect() string
}

type Integer struct {
	Value int64
}

type CompiledFunction struct {
	Instructions  code.Instructions
	NumLocals     int
	NumParameters int
}

func (i *Integer) Type() ObjectType {
	return INTEGER_OBJ
}
func (i *Integer) Inspect() string {
	return fmt.Sprintf("%d", i.Value)
}
func (i *Integer) Clone() Object {
	return &Integer{Value: i.Value}
}
func (i *Integer) String() string {
	return i.Inspect()
}
func (i *Integer) Equal(other Object) bool {
	if obj, ok := other.(*Integer); ok {
		return i.Value == obj.Value
	}
	return false
}

type Boolean struct {
	Value bool
}

func (b *Boolean) Type() ObjectType {
	return BOOLEAN_OBJ
}
func (b *Boolean) Inspect() string {
	return fmt.Sprintf("%t", b.Value)
}
func (b *Boolean) Clone() Object {
	return &Boolean{Value: b.Value}
}
func (b *Boolean) String() string {
	return b.Inspect()
}
func (b *Boolean) Equal(other Object) bool {
	if obj, ok := other.(*Boolean); ok {
		return b.Value == obj.Value
	}
	return false
}

type Null struct{}

func (n *Null) Type() ObjectType {
	return NULL_OBJ
}
func (n *Null) Inspect() string {
	return "null"
}
func (n *Null) String() string {
	return n.Inspect()
}
func (n *Null) Equal(other Object) bool {
	_, ok := other.(*Null)
	return ok
}

type ReturnValue struct {
	Value Object
}

func (rv *ReturnValue) Type() ObjectType {
	return RETURN_VALUE_OBJ
}
func (rv *ReturnValue) Inspect() string {
	return rv.Value.Inspect()
}
func (rv *ReturnValue) String() string {
	return rv.Inspect()
}

type Error struct {
	Message string
}

func (e *Error) Type() ObjectType {
	return ERROR_OBJ
}
func (e *Error) Inspect() string {
	return "Error: " + e.Message
}
func (e *Error) Clone() Object {
	return &Error{Message: e.Message}
}
func (e *Error) String() string {
	return e.Message
}

type Function struct {
	Parameters []*ast.Identifier
	Body       *ast.BlockStatement
	Env        *Environment
}

func (f *Function) Type() ObjectType {
	return FUNCTION_OBJ
}
func (f *Function) Inspect() string {
	var out bytes.Buffer

	params := []string{}
	for _, p := range f.Parameters {
		params = append(params, p.String())
	}

	out.WriteString("fn")
	out.WriteString("(")
	out.WriteString(strings.Join(params, ", "))
	out.WriteString(") {\n")
	out.WriteString(f.Body.String())
	out.WriteString("\n}")

	return out.String()
}
func (f *Function) String() string {
	return f.Inspect()
}

type String struct {
	Value string
}

func (s *String) Type() ObjectType {
	return STRING_OBJ
}
func (s *String) Inspect() string {
	return fmt.Sprintf("%#v", s.Value)
}
func (s *String) Clone() Object {
	return &String{Value: s.Value}
}
func (s *String) String() string {
	return s.Value
}
func (s *String) Equal(other Object) bool {
	if obj, ok := other.(*String); ok {
		return s.Value == obj.Value
	}
	return false
}

type BuiltinFunction func(args ...Object) Object

type Builtin struct {
	Name string
	Fn   BuiltinFunction
}

func (b *Builtin) Type() ObjectType {
	return BUILTIN_OBJ
}
func (b *Builtin) Inspect() string {
	return fmt.Sprintf("<built-in function %s>", b.Name)
}
func (b *Builtin) String() string {
	return b.Inspect()
}

type Array struct {
	Elements []Object
}

func (ao *Array) Type() ObjectType {
	return ARRAY_OBJ
}
func (ao *Array) Inspect() string {
	var out bytes.Buffer

	elements := []string{}
	for _, e := range ao.Elements {
		elements = append(elements, e.Inspect())
	}

	out.WriteString("[")
	out.WriteString(strings.Join(elements, ", "))
	out.WriteString("]")

	return out.String()
}
func (ao *Array) String() string {
	return ao.Inspect()
}
func (ao *Array) Equal(other Object) bool {
	if obj, ok := other.(*Array); ok {
		if len(ao.Elements) != len(obj.Elements) {
			return false
		}
		for i, el := range ao.Elements {
			cmp, ok := el.(Comparable)
			if !ok {
				return false
			}
			if !cmp.Equal(obj.Elements[i]) {
				return false
			}
		}

		return true
	}
	return false
}

type HashKey struct {
	Type  ObjectType
	Value uint64
}

func (b *Boolean) HashKey() HashKey {
	var value uint64

	if b.Value {
		value = 1
	} else {
		value = 0
	}

	return HashKey{Type: b.Type(), Value: value}
}

type Hashable interface {
	HashKey() HashKey
}

func (i *Integer) HashKey() HashKey {
	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
}

func (s *String) HashKey() HashKey {
	h := fnv.New64a()
	h.Write([]byte(s.Value))

	return HashKey{Type: s.Type(), Value: h.Sum64()}
}

type HashPair struct {
	Key   Object
	Value Object
}

type Hash struct {
	Pairs map[HashKey]HashPair
}

func (h *Hash) Type() ObjectType {
	return HASH_OBJ
}
func (h *Hash) Inspect() string {
	var out bytes.Buffer

	pairs := []string{}
	for _, pair := range h.Pairs {
		pairs = append(pairs, fmt.Sprintf("%s: %s", pair.Key.Inspect(), pair.Value.Inspect()))
	}

	out.WriteString("{")
	out.WriteString(strings.Join(pairs, ", "))
	out.WriteString("}")

	return out.String()
}
func (h *Hash) String() string {
	return h.Inspect()
}
func (h *Hash) Equal(other Object) bool {
	if obj, ok := other.(*Hash); ok {
		if len(h.Pairs) != len(obj.Pairs) {
			return false
		}
		for _, pair := range h.Pairs {
			left := pair.Value
			hashed := left.(Hashable)
			right, ok := obj.Pairs[hashed.HashKey()]
			if !ok {
				return false
			}
			cmp, ok := left.(Comparable)
			if !ok {
				return false
			}
			if !cmp.Equal(right.Value) {
				return false
			}
		}

		return true
	}
	return false
}

func (cf *CompiledFunction) Type() ObjectType {
	return COMPILED_FUNCTION_OBJ
}
func (cf *CompiledFunction) Inspect() string {
	return fmt.Sprintf("CompiledFunction[%p]", cf)
}
func (cf *CompiledFunction) String() string {
	return cf.Inspect()
}

type Closure struct {
	Fn   *CompiledFunction
	Free []Object
}

func (c *Closure) Type() ObjectType {
	return CLOSURE_OBJ
}
func (c *Closure) Inspect() string {
	return fmt.Sprintf("Closure[%p]", c)
}
func (c *Closure) String() string {
	return c.Inspect()
}