package dbc

import (
	"fmt"
	"reflect"

	"github.com/localhots/gobelt/reflect2"
)

type namedParams interface {
	Get(name string) (val interface{}, ok bool)
}

var (
	_ namedParams = namedParamsMap{}
	_ namedParams = &namedParamsStruct{}
)

func newNamedParams(val interface{}) (namedParams, error) {
	switch tval := val.(type) {
	case map[string]interface{}:
		return newNamedParamsMap(tval)
	default:
		return newNamedParamsStruct(val)
	}
}

type namedParamsMap struct {
	m map[string]interface{}
}

func newNamedParamsMap(m map[string]interface{}) (namedParamsMap, error) {
	return namedParamsMap{m}, nil
}

func (p namedParamsMap) Get(name string) (val interface{}, ok bool) {
	val, ok = p.m[name]
	return
}

type namedParamsStruct struct {
	s   reflect.Value
	idx map[string]int
}

func newNamedParamsStruct(s interface{}) (*namedParamsStruct, error) {
	val := reflect.ValueOf(s)
	if val.Kind() == reflect.Ptr {
		val = val.Elem()
	}
	if val.Kind() != reflect.Struct {
		return nil, fmt.Errorf("Unsupported named parameters type: %T", s)
	}
	return &namedParamsStruct{
		s:   val,
		idx: reflect2.TagIndex(val.Type(), tagName),
	}, nil
}

func (p *namedParamsStruct) Get(name string) (val interface{}, ok bool) {
	i, ok := p.idx[name]
	if !ok {
		return nil, false
	}
	return p.s.Field(i).Interface(), true
}