package ini

import (
	"encoding"
	"fmt"
	"reflect"
	"strconv"
	"strings"
)

// Types to look for ("Marshaler"/"Unmarshaler" interface)
var (
	marshalerType       = reflect.TypeOf(new(Marshaler)).Elem()
	unmarshalerType     = reflect.TypeOf(new(Unmarshaler)).Elem()
	textMarshalerType   = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
	textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
)

// INIDecoderError is returned on decoding error
type INIDecoderError struct {
	msg string
	err error
	f   *field
}

// Error returns an formatted string of the INIDecoderError
func (i *INIDecoderError) Error() string {
	return fmt.Sprintf(
		"INI Decoder Error: %s. %s. Field %s, namespace: %s",
		i.msg, i.err.Error(), i.f.t.Name(), i.f.ns,
	)
}

// INIEncoderError is returned on encoding error
type INIEncoderError struct {
	msg string
	err error
	f   *field
}

// Error returns an formatted string of the INIEncoderError
func (i *INIEncoderError) Error() string {
	return fmt.Sprintf(
		"INI Encoder Error: %s. Field: %s, namespace: %s",
		i.msg, i.err.Error(), i.f.t.Name(), i.f.ns,
	)
}

// decoder and encoder methods
type decodeFn func([]byte) error
type encodeFn func() ([]byte, error)

type field struct {
	ns string

	t reflect.Type
	v reflect.Value

	p interface{}

	// decoder or encoder method (will be changed when a cache for "elements" is implemented)
	fn interface{} // Use setFn to set this!
}

func newField(v reflect.Value, p interface{}, i int) *field {
	f := &field{
		t: v.Type(),
		v: v,
		p: nil,
	}

	if p != nil {
		switch p.(type) {
		case reflect.Type:
			f.p = p.(reflect.Type).Field(i)
		case reflect.Value:
			f.p = p.(reflect.Value).Type().Field(i)
		}
	}

	return f
}

// implements checks if the field implements the type t, or a pointer method to type t
func (f *field) implements(t reflect.Type) bool {
	return (f.t.Implements(t) || (f.t.Kind() != reflect.Ptr && reflect.PtrTo(f.t).Implements(t)))
}

// setNS determines the namespace for the field
func (f *field) setNS(ns string) string {
	if f.p == nil {
		f.ns = ns + "." + f.t.Name()
		return f.ns
	}

	if tag := f.p.(reflect.StructField).Tag.Get("ini"); len(tag) != 0 {
		f.ns = ns + "." + tag
		return f.ns
	}

	f.ns = ns + "." + f.p.(reflect.StructField).Name
	return f.ns
}

// setFN sets the function
func (f *field) setFn(fn interface{}) {
	f.fn = fn
}

// decode returns the decoder-method (do not call f.fn, for future changes!)
func (f *field) decode(b []byte) error {
	return f.fn.(decodeFn)(b)
}

// encode returns the decoder-method (do not call f.fn directly, for future changes!)
func (f *field) encode() ([]byte, error) {
	return f.fn.(encodeFn)()
}

/**
 DECODER METHODS
**/

func (f *field) valid() error {

	if f.v.CanAddr() {
		return nil
	}

	return fmt.Errorf("Field '%s' not addressable", f.ns)
}

func (f *field) uintDecoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Unsigned integer decoder",
			err: err,
			f:   f,
		}
	}

	i, err := strconv.ParseUint(string(b), 10, 64)

	if err != nil {
		return &INIDecoderError{
			msg: "Unsigned integer decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetUint(i)

	return nil
}

func (f *field) intDecoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Integer decoder",
			err: err,
			f:   f,
		}
	}

	i, err := strconv.ParseInt(string(b), 10, 64)

	if err != nil {
		return &INIDecoderError{
			msg: "Integer decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetInt(i)

	return nil
}

func (f *field) float32Decoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Float (32) decoder",
			err: err,
			f:   f,
		}
	}

	i, err := strconv.ParseFloat(string(b), 32)

	if err != nil {
		return &INIDecoderError{
			msg: "Float (32) decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetFloat(i)

	return nil
}

func (f *field) float64Decoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Float (64) decoder",
			err: err,
			f:   f,
		}
	}

	i, err := strconv.ParseFloat(string(b), 64)

	if err != nil {
		return &INIDecoderError{
			msg: "Float (64) decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetFloat(i)

	return nil
}

func (f *field) strDecoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "String decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetString(string(b))
	return nil
}

func (f *field) boolDecoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Boolean decoder",
			err: err,
			f:   f,
		}
	}

	f.v.SetBool(true)
	return nil
}

func (f *field) unmarshalerDecoder(b []byte) error {

	if err := f.valid(); err != nil {
		return &INIDecoderError{
			msg: "Unmarshaler decoder",
			err: err,
			f:   f,
		}
	}

	v := f.v

	if v.Kind() != reflect.Ptr && v.Type().Name() != "" {
		v = v.Addr()
	}

	if v.IsNil() {
		v.Set(reflect.New(v.Type().Elem()))
	}

	if i, ok := v.Interface().(Unmarshaler); ok {
		if err := i.UnmarshalINI(b); err != nil {
			return &INIDecoderError{
				msg: "UnmarshalINI decoder",
				err: err,
				f:   f,
			}
		}
		return nil
	}

	if i, ok := v.Interface().(encoding.TextUnmarshaler); ok {
		if err := i.UnmarshalText(b); err != nil {
			return &INIDecoderError{
				msg: "UnmarshalText decoder",
				err: err,
				f:   f,
			}
		}
		return nil
	}

	return fmt.Errorf("Cannot load Unmarshaler")
}

/**
 ENCODER METHODS
**/

func (f *field) nskey() string {
	return f.ns[strings.LastIndexByte(f.ns, '.')+1:]
}

func (f *field) uintEncoder() ([]byte, error) {
	i := strconv.FormatUint(f.v.Uint(), 10)
	return []byte(f.nskey() + " = " + i), nil
}

func (f *field) intEncoder() ([]byte, error) {
	i := strconv.FormatInt(f.v.Int(), 10)
	return []byte(f.nskey() + " = " + i), nil
}

func (f *field) float32Encoder() ([]byte, error) {
	i := strconv.FormatFloat(f.v.Float(), 'G', -1, 32)
	return []byte(f.nskey() + " = " + i), nil
}

func (f *field) float64Encoder() ([]byte, error) {
	i := strconv.FormatFloat(f.v.Float(), 'G', -1, 64)
	return []byte(f.nskey() + " = " + i), nil
}

func (f *field) strEncoder() ([]byte, error) {
	str := strings.Replace(f.v.String(), "\n", "\\\n", -1)
	return []byte(f.nskey() + " = " + str), nil
}

func (f *field) boolEncoder() ([]byte, error) {
	if f.v.Bool() {
		return []byte(f.nskey()), nil
	}
	return nil, nil
}

func (f *field) structEncoder() ([]byte, error) {

	split := strings.SplitN(f.ns, ".", 3)

	if len(split) == 2 {
		return nil, nil
	}

	if len(split) != 3 {
		return nil, &INIEncoderError{
			msg: "Struct encoder",
			err: fmt.Errorf("Invalid namespace"),
			f:   f,
		}
	}

	return []byte("\n[" + split[2] + "]"), nil
}

func (f *field) marshalerDecoder() ([]byte, error) {

	if err := f.valid(); err != nil {
		return nil, &INIEncoderError{
			msg: "Unmarshaler decoder",
			err: err,
			f:   f,
		}
	}

	v := f.v

	if v.Kind() != reflect.Ptr && v.Type().Name() != "" {
		v = v.Addr()
	}

	if v.IsNil() {
		v.Set(reflect.New(v.Type().Elem()))
	}

	if i, ok := v.Interface().(Marshaler); ok {
		b, err := i.MarshalINI()

		if err != nil {
			return nil, err
		}

		if b == nil {
			return nil, nil
		}

		return append([]byte(f.nskey()+" = "), b...), nil
	}

	if i, ok := v.Interface().(encoding.TextMarshaler); ok {
		b, err := i.MarshalText()

		if err != nil {
			return nil, err
		}

		if b == nil {
			return nil, nil
		}

		return append([]byte(f.nskey()+" = "), b...), nil
	}

	return nil, fmt.Errorf("Cannot load Marshaler")
}