package toml

import (
	"bytes"
	"errors"
	"fmt"
	"reflect"
	"strings"
	"time"
)

/*
Tree structural types and corresponding marshal types
-------------------------------------------------------------------------------
*Tree                        (*)struct, (*)map[string]interface{}
[]*Tree                      (*)[](*)struct, (*)[](*)map[string]interface{}
[]interface{} (as interface{})   (*)[]primitive, (*)[]([]interface{})
interface{}                      (*)primitive

Tree primitive types and  corresponding marshal types
-----------------------------------------------------------
uint64     uint, uint8-uint64, pointers to same
int64      int, int8-uint64, pointers to same
float64    float32, float64, pointers to same
string     string, pointers to same
bool       bool, pointers to same
time.Time  time.Time{}, pointers to same
*/

type tomlOpts struct {
	name      string
	include   bool
	omitempty bool
}

var timeType = reflect.TypeOf(time.Time{})
var marshalerType = reflect.TypeOf(new(Marshaler)).Elem()

// Check if the given marshall type maps to a Tree primitive
func isPrimitive(mtype reflect.Type) bool {
	switch mtype.Kind() {
	case reflect.Ptr:
		return isPrimitive(mtype.Elem())
	case reflect.Bool:
		return true
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return true
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return true
	case reflect.Float32, reflect.Float64:
		return true
	case reflect.String:
		return true
	case reflect.Struct:
		return mtype == timeType || isCustomMarshaler(mtype)
	default:
		return false
	}
}

// Check if the given marshall type maps to a Tree slice
func isTreeSlice(mtype reflect.Type) bool {
	switch mtype.Kind() {
	case reflect.Slice:
		return !isOtherSlice(mtype)
	default:
		return false
	}
}

// Check if the given marshall type maps to a non-Tree slice
func isOtherSlice(mtype reflect.Type) bool {
	switch mtype.Kind() {
	case reflect.Ptr:
		return isOtherSlice(mtype.Elem())
	case reflect.Slice:
		return isPrimitive(mtype.Elem()) || isOtherSlice(mtype.Elem())
	default:
		return false
	}
}

// Check if the given marshall type maps to a Tree
func isTree(mtype reflect.Type) bool {
	switch mtype.Kind() {
	case reflect.Map:
		return true
	case reflect.Struct:
		return !isPrimitive(mtype)
	default:
		return false
	}
}

func isCustomMarshaler(mtype reflect.Type) bool {
	return mtype.Implements(marshalerType)
}

func callCustomMarshaler(mval reflect.Value) ([]byte, error) {
	return mval.Interface().(Marshaler).MarshalTOML()
}

// Marshaler is the interface implemented by types that
// can marshal themselves into valid TOML.
type Marshaler interface {
	MarshalTOML() ([]byte, error)
}

/*
Marshal returns the TOML encoding of v.  Behavior is similar to the Go json
encoder, except that there is no concept of a Marshaler interface or MarshalTOML
function for sub-structs, and currently only definite types can be marshaled
(i.e. no `interface{}`).

Note that pointers are automatically assigned the "omitempty" option, as TOML
explicity does not handle null values (saying instead the label should be
dropped).
*/
func Marshal(v interface{}) ([]byte, error) {
	mtype := reflect.TypeOf(v)
	if mtype.Kind() != reflect.Struct {
		return []byte{}, errors.New("Only a struct can be marshaled to TOML")
	}
	sval := reflect.ValueOf(v)
	if isCustomMarshaler(mtype) {
		return callCustomMarshaler(sval)
	}
	t, err := valueToTree(mtype, sval)
	if err != nil {
		return []byte{}, err
	}
	s, err := t.ToTomlString()
	return []byte(s), err
}

// Convert given marshal struct or map value to toml tree
func valueToTree(mtype reflect.Type, mval reflect.Value) (*Tree, error) {
	if mtype.Kind() == reflect.Ptr {
		return valueToTree(mtype.Elem(), mval.Elem())
	}
	tval := newTree()
	switch mtype.Kind() {
	case reflect.Struct:
		for i := 0; i < mtype.NumField(); i++ {
			mtypef, mvalf := mtype.Field(i), mval.Field(i)
			opts := tomlOptions(mtypef)
			if opts.include && (!opts.omitempty || !isZero(mvalf)) {
				val, err := valueToToml(mtypef.Type, mvalf)
				if err != nil {
					return nil, err
				}
				tval.Set(opts.name, val)
			}
		}
	case reflect.Map:
		for _, key := range mval.MapKeys() {
			mvalf := mval.MapIndex(key)
			val, err := valueToToml(mtype.Elem(), mvalf)
			if err != nil {
				return nil, err
			}
			tval.Set(key.String(), val)
		}
	}
	return tval, nil
}

// Convert given marshal slice to slice of Toml trees
func valueToTreeSlice(mtype reflect.Type, mval reflect.Value) ([]*Tree, error) {
	tval := make([]*Tree, mval.Len(), mval.Len())
	for i := 0; i < mval.Len(); i++ {
		val, err := valueToTree(mtype.Elem(), mval.Index(i))
		if err != nil {
			return nil, err
		}
		tval[i] = val
	}
	return tval, nil
}

// Convert given marshal slice to slice of toml values
func valueToOtherSlice(mtype reflect.Type, mval reflect.Value) (interface{}, error) {
	tval := make([]interface{}, mval.Len(), mval.Len())
	for i := 0; i < mval.Len(); i++ {
		val, err := valueToToml(mtype.Elem(), mval.Index(i))
		if err != nil {
			return nil, err
		}
		tval[i] = val
	}
	return tval, nil
}

// Convert given marshal value to toml value
func valueToToml(mtype reflect.Type, mval reflect.Value) (interface{}, error) {
	if mtype.Kind() == reflect.Ptr {
		return valueToToml(mtype.Elem(), mval.Elem())
	}
	switch {
	case isCustomMarshaler(mtype):
		return callCustomMarshaler(mval)
	case isTree(mtype):
		return valueToTree(mtype, mval)
	case isTreeSlice(mtype):
		return valueToTreeSlice(mtype, mval)
	case isOtherSlice(mtype):
		return valueToOtherSlice(mtype, mval)
	default:
		switch mtype.Kind() {
		case reflect.Bool:
			return mval.Bool(), nil
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			return mval.Int(), nil
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			return mval.Uint(), nil
		case reflect.Float32, reflect.Float64:
			return mval.Float(), nil
		case reflect.String:
			return mval.String(), nil
		case reflect.Struct:
			return mval.Interface().(time.Time), nil
		default:
			return nil, fmt.Errorf("Marshal can't handle %v(%v)", mtype, mtype.Kind())
		}
	}
}

// Unmarshal attempts to unmarshal the Tree into a Go struct pointed by v.
// Neither Unmarshaler interfaces nor UnmarshalTOML functions are supported for
// sub-structs, and only definite types can be unmarshaled.
func (t *Tree) Unmarshal(v interface{}) error {
	mtype := reflect.TypeOf(v)
	if mtype.Kind() != reflect.Ptr || mtype.Elem().Kind() != reflect.Struct {
		return errors.New("Only a pointer to struct can be unmarshaled from TOML")
	}

	sval, err := valueFromTree(mtype.Elem(), t)
	if err != nil {
		return err
	}
	reflect.ValueOf(v).Elem().Set(sval)
	return nil
}

// Unmarshal parses the TOML-encoded data and stores the result in the value
// pointed to by v. Behavior is similar to the Go json encoder, except that there
// is no concept of an Unmarshaler interface or UnmarshalTOML function for
// sub-structs, and currently only definite types can be unmarshaled to (i.e. no
// `interface{}`).
func Unmarshal(data []byte, v interface{}) error {
	t, err := LoadReader(bytes.NewReader(data))
	if err != nil {
		return err
	}
	return t.Unmarshal(v)
}

// Convert toml tree to marshal struct or map, using marshal type
func valueFromTree(mtype reflect.Type, tval *Tree) (reflect.Value, error) {
	if mtype.Kind() == reflect.Ptr {
		return unwrapPointer(mtype, tval)
	}
	var mval reflect.Value
	switch mtype.Kind() {
	case reflect.Struct:
		mval = reflect.New(mtype).Elem()
		for i := 0; i < mtype.NumField(); i++ {
			mtypef := mtype.Field(i)
			opts := tomlOptions(mtypef)
			if opts.include {
				key := opts.name
				exists := tval.Has(key)
				if exists {
					val := tval.Get(key)
					mvalf, err := valueFromToml(mtypef.Type, val)
					if err != nil {
						return mval, formatError(err, tval.GetPosition(key))
					}
					mval.Field(i).Set(mvalf)
				}
			}
		}
	case reflect.Map:
		mval = reflect.MakeMap(mtype)
		for _, key := range tval.Keys() {
			val := tval.Get(key)
			mvalf, err := valueFromToml(mtype.Elem(), val)
			if err != nil {
				return mval, formatError(err, tval.GetPosition(key))
			}
			mval.SetMapIndex(reflect.ValueOf(key), mvalf)
		}
	}
	return mval, nil
}

// Convert toml value to marshal struct/map slice, using marshal type
func valueFromTreeSlice(mtype reflect.Type, tval []*Tree) (reflect.Value, error) {
	mval := reflect.MakeSlice(mtype, len(tval), len(tval))
	for i := 0; i < len(tval); i++ {
		val, err := valueFromTree(mtype.Elem(), tval[i])
		if err != nil {
			return mval, err
		}
		mval.Index(i).Set(val)
	}
	return mval, nil
}

// Convert toml value to marshal primitive slice, using marshal type
func valueFromOtherSlice(mtype reflect.Type, tval []interface{}) (reflect.Value, error) {
	mval := reflect.MakeSlice(mtype, len(tval), len(tval))
	for i := 0; i < len(tval); i++ {
		val, err := valueFromToml(mtype.Elem(), tval[i])
		if err != nil {
			return mval, err
		}
		mval.Index(i).Set(val)
	}
	return mval, nil
}

// Convert toml value to marshal value, using marshal type
func valueFromToml(mtype reflect.Type, tval interface{}) (reflect.Value, error) {
	if mtype.Kind() == reflect.Ptr {
		return unwrapPointer(mtype, tval)
	}
	switch {
	case isTree(mtype):
		return valueFromTree(mtype, tval.(*Tree))
	case isTreeSlice(mtype):
		return valueFromTreeSlice(mtype, tval.([]*Tree))
	case isOtherSlice(mtype):
		return valueFromOtherSlice(mtype, tval.([]interface{}))
	default:
		switch mtype.Kind() {
		case reflect.Bool:
			val, ok := tval.(bool)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to bool", tval, tval)
			}
			return reflect.ValueOf(val), nil
		case reflect.Int:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to int", tval, tval)
			}
			return reflect.ValueOf(int(val)), nil
		case reflect.Int8:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to int", tval, tval)
			}
			return reflect.ValueOf(int8(val)), nil
		case reflect.Int16:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to int", tval, tval)
			}
			return reflect.ValueOf(int16(val)), nil
		case reflect.Int32:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to int", tval, tval)
			}
			return reflect.ValueOf(int32(val)), nil
		case reflect.Int64:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to int", tval, tval)
			}
			return reflect.ValueOf(val), nil
		case reflect.Uint:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to uint", tval, tval)
			}
			return reflect.ValueOf(uint(val)), nil
		case reflect.Uint8:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to uint", tval, tval)
			}
			return reflect.ValueOf(uint8(val)), nil
		case reflect.Uint16:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to uint", tval, tval)
			}
			return reflect.ValueOf(uint16(val)), nil
		case reflect.Uint32:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to uint", tval, tval)
			}
			return reflect.ValueOf(uint32(val)), nil
		case reflect.Uint64:
			val, ok := tval.(int64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to uint", tval, tval)
			}
			return reflect.ValueOf(uint64(val)), nil
		case reflect.Float32:
			val, ok := tval.(float64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to float", tval, tval)
			}
			return reflect.ValueOf(float32(val)), nil
		case reflect.Float64:
			val, ok := tval.(float64)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to float", tval, tval)
			}
			return reflect.ValueOf(val), nil
		case reflect.String:
			val, ok := tval.(string)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to string", tval, tval)
			}
			return reflect.ValueOf(val), nil
		case reflect.Struct:
			val, ok := tval.(time.Time)
			if !ok {
				return reflect.ValueOf(nil), fmt.Errorf("Can't convert %v(%T) to time", tval, tval)
			}
			return reflect.ValueOf(val), nil
		default:
			return reflect.ValueOf(nil), fmt.Errorf("Unmarshal can't handle %v(%v)", mtype, mtype.Kind())
		}
	}
}

func unwrapPointer(mtype reflect.Type, tval interface{}) (reflect.Value, error) {
	val, err := valueFromToml(mtype.Elem(), tval)
	if err != nil {
		return reflect.ValueOf(nil), err
	}
	mval := reflect.New(mtype.Elem())
	mval.Elem().Set(val)
	return mval, nil
}

func tomlOptions(vf reflect.StructField) tomlOpts {
	tag := vf.Tag.Get("toml")
	parse := strings.Split(tag, ",")
	result := tomlOpts{vf.Name, true, false}
	if parse[0] != "" {
		if parse[0] == "-" && len(parse) == 1 {
			result.include = false
		} else {
			result.name = strings.Trim(parse[0], " ")
		}
	}
	if vf.PkgPath != "" {
		result.include = false
	}
	if len(parse) > 1 && strings.Trim(parse[1], " ") == "omitempty" {
		result.omitempty = true
	}
	if vf.Type.Kind() == reflect.Ptr {
		result.omitempty = true
	}
	return result
}

func isZero(val reflect.Value) bool {
	switch val.Type().Kind() {
	case reflect.Map:
		fallthrough
	case reflect.Array:
		fallthrough
	case reflect.Slice:
		return val.Len() == 0
	default:
		return reflect.DeepEqual(val.Interface(), reflect.Zero(val.Type()).Interface())
	}
}

func formatError(err error, pos Position) error {
	if err.Error()[0] == '(' { // Error already contains position information
		return err
	}
	return fmt.Errorf("%s: %s", pos, err)
}