// Во имя Бога Милостивого, Милосердного!!!
package goconf

import (
	"errors"
	"go/ast"
	"go/parser"
	"go/token"
	"reflect"
	"strconv"
)

type ConfigParser struct {
	config   interface{}
	filename string
}

func LoadConfig(config interface{}, config_go string) error {
	p := &ConfigParser{config: config, filename: config_go}
	return p.parse()
}

func (c *ConfigParser) parse() error {
	fset := token.NewFileSet()
	af, err := parser.ParseFile(fset, c.filename, nil, parser.ParseComments)
	if err != nil {
		return err
	}

	return c.parseAST(af)
}

func (c *ConfigParser) parseAST(af *ast.File) error {
	ast.Inspect(af, c.searchForConfigAndShouldContinue)
	return nil
}
func (c *ConfigParser) searchForConfigAndShouldContinue(n ast.Node) bool {
	vs, ok := n.(*ast.ValueSpec)
	if ok && vs.Names[0].Name == "config" {
		c.digConfig(vs)
		return false
	}
	return true
}

func (c *ConfigParser) digConfig(config ast.Node) error {
	ast.Inspect(config, c.searchForConfigElementsAndShouldContinue)
	return nil
}
func (c *ConfigParser) searchForConfigElementsAndShouldContinue(n ast.Node) bool {
	definition, ok := n.(*ast.CompositeLit)
	if ok {
		t, ok := definition.Type.(*ast.Ident)
		if ok && t.Name == "Config" {
			c.digConfigElements(definition.Elts)
			return false
		}
	}
	return true
}

func (c *ConfigParser) digConfigElements(elements []ast.Expr) error {
	for _, e := range elements {
		c.digConfigElement(e)
	}
	return nil
}
func (c *ConfigParser) digConfigElement(e ast.Expr) error {
	keyvalue, ok := e.(*ast.KeyValueExpr)
	if !ok {
		return errors.New("Not ast.KeyValueExpr")
	}

	key, ok := keyvalue.Key.(*ast.Ident)
	if !ok {
		return errors.New("Key not found")
	}

	switch keyvalue.Value.(type) {
	case *ast.BasicLit, *ast.Ident:
		return c.setConfigElement(key.Name, keyvalue.Value)
	default:
		return errors.New("Value not found")
	}

	return nil
}

func (c *ConfigParser) setConfigElement(key string, value ast.Expr) error {
	config := reflect.ValueOf(c.config)

	kind := config.Kind()
	if config.IsNil() || kind != reflect.Ptr {
		return errors.New("Bad config pointer")
	}

	config = config.Elem()
	kind = config.Kind()
	if kind != reflect.Struct {
		return errors.New("Config is not a struct")
	}

	vt := config.Type()
	numFields := config.NumField()
	for i := 0; i < numFields; i++ {
		c.setConfigElementField(key, value, config, i, vt)
	}

	return nil
}
func (c *ConfigParser) setConfigElementField(key string, value ast.Expr, config reflect.Value, i int, vt reflect.Type) error {
	if vt.Field(i).Name != key {
		return nil
	}

	vf := config.Field(i)
	uv := unpackValue(vf)
	kind := uv.Kind()

	switch kind {
	case reflect.String:
		c.setConfigFieldToString(uv, value)
	case reflect.Int:
		c.setConfigFieldToInt(uv, value)
	case reflect.Bool:
		c.setConfigFieldToBool(uv, value)
	}
	return nil
}

func unpackValue(v reflect.Value) reflect.Value {
	if v.Kind() == reflect.Interface && !v.IsNil() {
		v = v.Elem()
	}
	return v
}

func (c *ConfigParser) setConfigFieldToString(uv reflect.Value, v ast.Expr) error {
	switch v.(type) {
	case *ast.BasicLit:
	default:
		return errors.New("Not string")
	}

	value := v.(*ast.BasicLit)

	if value.Kind != token.STRING {
		return errors.New("Not string")
	}
	s, err := strconv.Unquote(value.Value)
	if err != nil {
		return err
	}
	uv.SetString(s)
	return nil
}

func (c *ConfigParser) setConfigFieldToInt(uv reflect.Value, v ast.Expr) error {
	switch v.(type) {
	case *ast.BasicLit:
	default:
		return errors.New("Not int")
	}

	value := v.(*ast.BasicLit)

	if value.Kind != token.INT {
		return errors.New("Not int")
	}
	num, err := strconv.Atoi(value.Value)
	if err != nil {
		return err
	}
	uv.SetInt(int64(num))
	return nil
}

func (c *ConfigParser) setConfigFieldToBool(uv reflect.Value, v ast.Expr) error {
	switch v.(type) {
	case *ast.Ident:
	default:
		return errors.New("Not bool")
	}

	value := v.(*ast.Ident)

	switch value.Name {
	case "true":
		uv.SetBool(true)
	case "false":
		uv.SetBool(false)
	default:
		return errors.New("Not bool")
	}

	return nil
}