package convert

import (
	"fmt"
	"sort"
	"strconv"
	"unicode/utf8"

	. "gitea.zaclys.com/bvaudour/gob/option"
)

type BoolType interface {
	~bool
}

type CharType interface {
	~byte | ~rune
}

type StringType interface {
	~string
}

type IntType interface {
	~int | ~int8 | ~int16 | ~int32 | ~int64
}

type UintType interface {
	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64
}

type FloatType interface {
	~float32 | ~float64
}

type ComplexType interface {
	~complex64 | ~complex128
}

type IntegerType interface {
	IntType | UintType
}

type RealType interface {
	IntegerType | FloatType
}

type NumberType interface {
	RealType | ComplexType
}

type convFunc = func(Value, Value) bool

func isConvertible(t1, t2 Type) bool {
	return t1.AssignableTo(t2) || t1.EquivalentTo(t2)
}

func getConvFunc(t Type) (f Option[convFunc]) {
	switch {
	case t.Is(Bool):
		f = Some(fromBool)
	case t.Is(Char):
		f = Some(fromChar)
	case t.Is(Int):
		f = Some(fromInt)
	case t.Is(Uint):
		f = Some(fromUint)
	case t.Is(Float):
		f = Some(fromFloat)
	case t.Is(Complex):
		f = Some(fromComplex)
	case t.Is(String):
		f = Some(fromString)
	case t.Is(Slice.Or(Array)):
		f = Some(fromSlice)
	case t.IsSet():
		f = Some(fromSet)
	case t.Is(Map):
		f = Some(fromMap)
	case t.Is(Struct):
		f = Some(fromStruct)
	}
	return
}

func safeConv(src, dest Value) bool {
	ts, td := src.Type(), dest.Type()
	if ts.AssignableTo(td) {
		dest.Set(src)
		return true
	} else if ts.EquivalentTo(td) {
		dest.Set(src.Convert(td))
		return true
	}
	return false
}

func unsafeConv(src, dest Value) bool {
	f, ok := getConvFunc(src.Type()).Get()
	return ok && f(src, dest)
}

func conv(src, dest Value, safe ...bool) bool {
	if safeConv(src, dest) {
		return true
	} else if len(safe) == 0 || !safe[0] {
		return unsafeConv(src, dest)
	} else if src.Is(Slice.Or(Array)) && dest.Is(Slice.Or(Array)) {
		return safeConvSlice(src, dest)
	} else if src.Is(Map) && dest.Is(Map) {
		return safeConvMap(src, dest)
	}
	return false
}

func safeConvSlice(src, dest Value) (ok bool) {
	l, t := src.Len(), dest.Type()
	isArray := t.Is(Array)
	var v Value
	if isArray {
		if t.Len() != l {
			return
		}
		v = SliceOf(SliceTypeOf(t.Elem()), l, src.Cap())
	} else {
		v = SliceOf(t, l, src.Cap())
	}
	ok = true
	for i := 0; i < l; i++ {
		e1, e2 := src.Index(i), v.Index(i)
		if ok = Convert(e1.Interface(), e2.Pointer().Interface(), true); !ok {
			return
		}
	}
	if isArray {
		v = v.Convert(PointerTo(t)).Elem()
	}
	dest.Set(v)
	return
}

func safeConvMap(src, dest Value) (ok bool) {
	t := dest.Type()
	tk, tv := t.Key(), t.Elem()
	v := MapOf(t)
	keys := src.Keys()
	ok = true
	for _, k1 := range keys {
		k2 := PointerOf(tk)
		if ok = Convert(k1.Interface(), k2.Interface(), true); !ok {
			return
		}
		e1, e2 := src.MapIndex(k1), PointerOf(tv)
		if ok = Convert(e1.Interface(), e2.Interface(), true); !ok {
			return
		}
		v.SetMapIndex(k2.Elem(), e2.Elem())
	}
	dest.Set(v)
	return
}

func toSlice(src, dest Value) (ok bool) {
	t := dest.Type()
	r := AddressableOf(t.Elem())
	if ok = conv(src, r); ok {
		sl := SliceOf(t, 1, 1)
		sl.Index(0).Set(r)
		dest.Set(sl)
	}
	return
}

func toArray(src, dest Value) (ok bool) {
	t := dest.Type()
	tsl := SliceTypeOf(t.Elem())
	sl := AddressableOf(tsl)
	if ok = toSlice(src, sl); ok {
		dest.Set(sl.Convert(t))
	}
	return
}

func toSet(src, dest Value) (ok bool) {
	t := dest.Type()
	r := AddressableOf(t.Key())
	if ok = conv(src, r); ok {
		m := MapOf(t)
		m.AddToSet(r)
		dest.Set(m)
	}
	return
}

func fromBool(src, dest Value) (ok bool) {
	e := src.Bool()
	var r any
	switch {
	case dest.Is(Bool):
		r, ok = e, true
	case dest.Is(Number):
		r, ok = 0, true
		if e {
			r = 1
		}
	case dest.Is(String):
		r, ok = strconv.FormatBool(e), true
	case dest.Is(Slice):
		return toSlice(src, dest)
	case dest.Is(Array):
		return toArray(src, dest)
	case dest.IsSet():
		return toSet(src, dest)
	}
	if ok {
		v := ValueOf(r).Convert(dest.Type())
		dest.Set(v)
	}
	return
}

func fromChar(src, dest Value) (ok bool) {
	e := src.Int()
	var r any
	switch {
	case dest.Is(Bool):
		r, ok = e != 0, true
	case dest.Is(Char):
		r, ok = e, true
	case dest.Is(Number):
		r, ok = e-int64('0'), true
	case dest.Is(String):
		r, ok = fmt.Sprintf("%c", e), true
	case dest.Is(Slice):
		return toSlice(src, dest)
	case dest.Is(Array):
		return toArray(src, dest)
	case dest.IsSet():
		return toSet(src, dest)
	}
	if ok {
		v := ValueOf(r).Convert(dest.Type())
		dest.Set(v)
	}
	return
}

func fromString(src, dest Value) (ok bool) {
	e := src.String()
	var r any
	var err error
	switch {
	case dest.Is(Bool):
		r, err = strconv.ParseBool(e)
		ok = err == nil
	case dest.Is(Char):
		if ok = utf8.RuneCountInString(e) == 1; ok {
			r, _ = utf8.DecodeRuneInString(e)
		}
	case dest.Is(Int):
		r, err = strconv.ParseInt(e, 0, 64)
		ok = err == nil
	case dest.Is(Uint):
		r, err = strconv.ParseUint(e, 0, 64)
		ok = err == nil
	case dest.Is(Float):
		r, err = strconv.ParseFloat(e, 64)
		ok = err == nil
	case dest.Is(Complex):
		r, err = strconv.ParseComplex(e, 128)
		ok = err == nil
	case dest.Is(Slice):
		return toSlice(src, dest)
	case dest.Is(Array):
		return toArray(src, dest)
	case dest.IsSet():
		return toSet(src, dest)
	}
	if ok {
		v := ValueOf(r).Convert(dest.Type())
		dest.Set(v)
	}
	return
}

func fromNumber[T RealType](src, dest Value, e T, f func(T) any) (ok bool) {
	var r any
	switch {
	case dest.Is(Bool):
		r, ok = e != 0, true
	case dest.Is(Char):
		r, ok = rune(int64(e))+'0', true

	case dest.Is(Number):
		r, ok = e, true
	case dest.Is(String):
		r, ok = f(e), true
	case dest.Is(Slice):
		return toSlice(src, dest)
	case dest.Is(Array):
		return toArray(src, dest)
	case dest.IsSet():
		return toSet(src, dest)
	}
	if ok {
		v := ValueOf(r).Convert(dest.Type())
		dest.Set(v)
	}
	return
}

func fromInt(src, dest Value) (ok bool) {
	e := src.Int()
	return fromNumber(
		src,
		dest,
		e,
		func(n int64) any { return strconv.FormatInt(n, 10) },
	)
}

func fromUint(src, dest Value) (ok bool) {
	e := src.Uint()
	return fromNumber(
		src,
		dest,
		e,
		func(n uint64) any { return strconv.FormatUint(n, 10) },
	)
}

func fromFloat(src, dest Value) (ok bool) {
	e := src.Float()
	return fromNumber(
		src,
		dest,
		e,
		func(n float64) any { return strconv.FormatFloat(n, 'f', -1, 64) },
	)
}

func fromComplex(src, dest Value) (ok bool) {
	e := src.Complex()
	var r any
	switch {
	case dest.Is(Bool):
		r, ok = e != 0, true
	case dest.Is(Char):
		r, ok = rune(real(e))+'0', true
	case dest.Is(Real):
		r, ok = real(e), true
	case dest.Is(Complex):
		r, ok = e, true
	case dest.Is(String):
		r, ok = strconv.FormatComplex(e, 'f', -1, 64), true
	case dest.Is(Slice):
		return toSlice(src, dest)
	case dest.Is(Array):
		return toArray(src, dest)
	case dest.IsSet():
		return toSet(src, dest)
	}
	if ok {
		v := ValueOf(r).Convert(dest.Type())
		dest.Set(v)
	}
	return
}

func fromSlice(src, dest Value) (ok bool) {
	t, l := dest.Type(), src.Len()
	var r Value
	switch {
	case dest.Is(Slice):
		r, ok = SliceOf(t, l, src.Cap()), true
		for i := 0; i < l; i++ {
			if ok = conv(src.Index(i, true), r.Index(i)); !ok {
				return
			}
		}
	case dest.Is(Array):
		if ok = l == t.Len(); !ok {
			return
		}
		tsl := SliceTypeOf(t.Elem())
		r = SliceOf(tsl, l, src.Cap())
		if ok = fromSlice(src, r); !ok {
			return
		}
		r = r.Convert(PointerTo(t)).Elem()
	case dest.IsSet():
		tk := t.Key()
		r = MapOf(t)
		for i := 0; i < l; i++ {
			e1, e2 := src.Index(i, true), AddressableOf(tk)
			if ok = conv(e1, e2); !ok {
				return
			}
			r.AddToSet(e2)
		}
	case dest.Is(Map):
		t := dest.Type()
		tk, tv := t.Key(), t.Elem()
		r = MapOf(t)
		for i := 0; i < l; i++ {
			e1, e2 := src.Index(i, true), AddressableOf(tv)
			if ok = conv(e1, e2); !ok {
				return
			}
			k := AddressableOf(tk)
			if ok = conv(ValueOf(i), k); !ok {
				return
			}
			r.SetMapIndex(k, e2)
		}
	default:
		if ok = l == 1; ok {
			return conv(src.Index(0, true), dest)
		}
	}
	if ok {
		dest.Set(r)
	}
	return
}

func fromSet(src, dest Value) (ok bool) {
	t, keys := dest.Type(), src.Keys()
	var r Value
	switch {
	case dest.Is(Slice):
		r, ok = SliceOf(t, len(keys), len(keys)), true
		for i, k := range keys {
			if ok = conv(src.MapIndex(k, true), r.Index(i)); !ok {
				return
			}
		}
	case dest.Is(Array):
		if ok = len(keys) == t.Len(); !ok {
			return
		}
		tsl := SliceTypeOf(t.Elem())
		r = SliceOf(tsl, len(keys), len(keys))
		if ok = fromSet(src, r); ok {
			r = r.Convert(PointerTo(t)).Elem()
		}
	case dest.IsSet():
		tk := t.Key()
		r, ok = MapOf(t), true
		for _, k := range keys {
			e1, e2 := src.MapIndex(k, true), AddressableOf(tk)
			if ok = conv(e1, e2); !ok {
				return
			}
			r.AddToSet(e2)
		}
	default:
		if ok = len(keys) == 1; ok {
			ok = conv(src.MapIndex(keys[0], true), dest)
		}
	}
	if ok {
		dest.Set(r)
	}
	return
}

func fromMap(src, dest Value) (ok bool) {
	t, keys := dest.Type(), src.Keys()
	var r Value
	switch {
	case dest.Is(Slice):
		idx := make([]int, len(keys))
		ki := make(map[Value]int)
		for i, k := range keys {
			var e int
			if ok = conv(ValueOf(k.Interface()), ValueOf(&e).Elem()); !ok {
				return
			}
			ki[k], idx[i] = e, e
		}
		sort.Ints(idx)
		for i, j := range idx {
			if ok = i == j; !ok {
				return
			}
		}
		r, ok = SliceOf(t, len(keys), len(keys)), true
		for _, k := range keys {
			if ok = conv(src.MapIndex(k, true), r.Index(ki[k])); !ok {
				return
			}
		}
	case dest.Is(Array):
		if ok = t.Len() != len(keys); !ok {
			return
		}
		tsl := SliceTypeOf(t.Elem())
		r = AddressableOf(tsl)
		if ok = fromMap(src, r); ok {
			r = r.Convert(PointerTo(t)).Elem()
		}
	case dest.Is(Map):
		tk, tv := t.Key(), t.Elem()
		r, ok = MapOf(t), true
		for _, k := range keys {
			e1, e2 := src.MapIndex(k, true), AddressableOf(tv)
			if ok = conv(e1, e2); !ok {
				return
			}
			kd := AddressableOf(tk)
			if ok = conv(ValueOf(k.Interface()), kd); !ok {
				return
			}
			r.SetMapIndex(kd, e2)
		}
	case dest.Is(Struct):
		r, ok = AddressableOf(t), true
		for _, k := range keys {
			var fs string
			if !Convert(k.Interface(), &fs) {
				continue
			}
			if f, exists := t.FieldByName(fs); !exists || f.PkgPath != "" {
				continue
			}
			e1, e2 := src.MapIndex(k, true), r.FieldByName(fs)
			if !e1.Is(Ptr) && e2.Is(Ptr) {
				e2.Set(PointerOf(e2.TypeElem()))
				e2 = e2.Elem()
			}
			if ok = conv(e1, e2); !ok {
				return
			}
		}
	}
	if ok {
		dest.Set(r)
	}
	return
}

func fromStruct(src, dest Value) (ok bool) {
	ts, t := src.Type(), dest.Type()
	fields := ts.Fields()
	var r Value
	switch {
	case dest.Is(Struct):
		r, ok = AddressableOf(t), true
		for _, f := range fields {
			if _, exists := t.FieldByName(f.Name); !exists {
				continue
			}
			e1, e2 := src.FieldByName(f.Name, true), r.FieldByName(f.Name)
			if !e1.Is(Ptr) && e2.Is(Ptr) {
				e2.Set(PointerOf(e2.TypeElem()))
				e2 = e2.Elem()
			} else if e1.Is(Ptr) && !e2.Is(Ptr) {
				if e1.IsNil() {
					e1 = ZeroOf(e1.Type().Elem())
				} else {
					e1 = e1.Elem()
				}
			}
			if ok = conv(e1, e2); !ok {
				return
			}
		}
	case dest.Is(Map):
		r, ok = MapOf(t), true
		tk, tv := t.Key(), t.Elem()
		for _, f := range fields {
			e1, e2 := src.FieldByName(f.Name, true), AddressableOf(tv)
			if e1.Is(Ptr) && !e2.Is(Ptr) {
				if e1.IsNil() {
					e1 = ZeroOf(e1.Type().Elem())
				} else {
					e1 = e1.Elem()
				}
			}
			if ok = conv(e1, e2); !ok {
				return
			}
			k := AddressableOf(tk)
			if ok = conv(ValueOf(f.Name), k); !ok {
				return
			}
			r.SetMapIndex(k, e2)
		}
	}
	if ok {
		dest.Set(r)
	}
	return
}

// Convert convertit la valeur du paramètre source vers
// le paramètre destination et retourne true si l’opération
// s’est effectuée avec succès.
// La destination doit être un pointeur, afin de pouvoir modifier
// sa valeur.
// Si le paramètre optionnel safe est fourni et vaut true,
// la destination n’est modifiée que si son type est équivalent
// à celui de la source (par exemple int vers int64, mais
// pas int vers string).
func Convert(src, dest any, safe ...bool) bool {
	vs, vd := ValueOf(src), ValueOf(dest)
	if !vd.Is(Ptr) || vd.IsNil() {
		return false
	}
	return conv(vs, vd.Elem(), safe...)
}

func setDefault[T any](def ...T) (out T) {
	if len(def) > 0 {
		out = def[0]
	}
	return
}

func toSingle[T BoolType | StringType | NumberType](src any, def ...T) (dest T) {
	if ok := Convert(src, &dest); !ok {
		dest = setDefault(def...)
	}
	return
}

func ToBool[T BoolType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToChar[T CharType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToInt[T IntType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToUint[T UintType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToInteger[T IntegerType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToFloat[T FloatType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToComplex[T ComplexType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToString[T StringType](src any, def ...T) T {
	return toSingle(src, def...)
}

func ToSlice[T any](src any, def ...T) (dest []T) {
	if ok := Convert(src, &dest); !ok {
		dest = def
	}
	return
}

func ToMap[K comparable, V any](src any, def ...map[K]V) (dest map[K]V) {
	if ok := Convert(src, &dest); !ok {
		if len(def) > 0 {
			dest = def[0]
		} else {
			dest = make(map[K]V)
		}
	}
	return
}

func ToSet[K comparable](src any, def ...map[K]struct{}) map[K]struct{} {
	return ToMap(src, def...)
}

// SetZero réinitialise la variable pointée
// par le paramètre d’entrée à sa valeur initiale
func SetZero(dst any) bool {
	vd := ValueOf(dst)
	if !vd.Is(Ptr) {
		return false
	}
	z := ZeroOf(vd.TypeElem())
	vd.SetElem(z)
	return true
}

func clone(v Value, deep ...bool) Value {
	t := v.Type()
	var c Value
	switch {
	case v.IsNil():
		c = v
	case v.Is(Ptr):
		if len(deep) == 0 || !deep[0] {
			return v
		}
		vc := clone(v.Elem(), deep...)
		c = PointerOf(t.Elem())
		c.SetElem(vc)
	case v.Is(Slice):
		l := v.Len()
		c := SliceOf(t, l, v.Cap())
		for i := 0; i < l; i++ {
			s, d := v.Index(i), c.Index(i)
			d.Set(clone(s, deep...))
		}
	case v.Is(Array):
		l := v.Len()
		tsl := SliceTypeOf(t.Elem())
		c := SliceOf(tsl, l, v.Cap())
		for i := 0; i < l; i++ {
			s, d := v.Index(i), c.Index(i)
			d.Set(clone(s, deep...))
		}
		c = c.Convert(PointerTo(t)).Elem()
	case v.Is(Map):
		c = MapOf(t)
		for _, k := range v.Keys() {
			s := v.MapIndex(k)
			c.SetMapIndex(clone(k, deep...), clone(s, deep...))
		}
	case v.Is(Struct):
		c := ValueOf(t)
		n := t.NumField()
		for i := 0; i < n; i++ {
			f := t.Field(i)
			if f.PkgPath != "" {
				continue
			}
			s, d := v.Field(i), c.Field(i)
			d.Set(clone(s, deep...))
		}
	default:
		c = PointerOf(t)
		Convert(v.Interface(), c.Interface())
		c = c.Elem()
	}
	return c
}

// CloneInterface est l’équivalent rapide de Clone
// si la valeur de sortie n’a pas besoin d’être typée.
func CloneInterface(e any, deep ...bool) any {
	c := clone(ValueOf(e), deep...)
	return c.Interface()
}

// Clone retourne une copie de l’élément fournit en paramètre.
// Si deep est fourni et vaut true, le clonage s’effectue récursivement.
func Clone[T any](e T, deep ...bool) T {
	c := clone(ValueOf(e), deep...)
	if c.IsNil() {
		return e
	}
	var out T
	v := ValueOf(&out)
	v.SetElem(c)
	return v.Interface().(T)
}