package raku

import (
    "errors"
    "fmt"
    "io/ioutil"
    "os"
    "github.com/yhirose/go-peg"    
)

type Parser struct {
    *peg.Parser
}

type Result struct {
    * peg.Ast
}

func parserCheck(err error) {
    if perr, ok := err.(*peg.Error); ok {
        for _, d := range perr.Details {
            fmt.Println(d)
        }
        os.Exit(1)
    }
}

var defaultParser *Parser

/** Loads a PEG parser from the given file name. */
func LoadParser(filename string) (*Parser, error) {
    result := &Parser{}
    data, err := ioutil.ReadFile(filename)
    if err == nil {
        result.Parser, err = peg.NewParser(string(data))
        if err == nil {
            result.EnableAst()            
        }        
        return result, err
    } else {
        return nil, err
    }
}


func InitDefaultParser(peg_filename string) error {
    var err error
    defaultParser, err = LoadParser(peg_filename)
    return err
}

func wrapResult(wrapme peg.Any) *Result {
    result := &Result{};
    ast, ok := wrapme.(*peg.Ast)
    if ok {
        result.Ast = ast
        return result
    } 
    return nil    
}

func (parser Parser) Parse(source string) (*Result, error) {
    ast, err := parser.ParseAndGetValue(source, nil)
    return wrapResult(ast), err
}

func (parser Parser) ParseFile(filename string) (*Result, error) {    
    source, err := ioutil.ReadFile(filename)
    if err == nil {
        return parser.Parse(string(source))
    } else {
        return nil, err
    }
}

func parse(source string) (*Result, error) {
    if defaultParser == nil {
        return nil, errors.New("Default parser not initialized!")
    }
    return defaultParser.Parse(source)
}

func parseFile(filename string) (*Result, error) {
    if defaultParser == nil {
        return nil, errors.New("Default parser not initialized!")
    }
    return defaultParser.ParseFile(filename)
}


type Method func (raku * Raku, message string, target Object, args ... interface{}) (Object, error)

type Command struct {
    Name string
    Method 
}

type CommandMap = map[string] Command

type Class interface {
    Object
    Parent() * Class
    Selector(name string) * Method
}

type Object interface {
    Class() Class
    Send(raku * Raku, message string, args ... interface {}) (Object, error)
}

var RootClass * DefaultClass = &DefaultClass{}

type DefaultObject struct {
    class Class
    * Raku
    CommandMap
}

func (object DefaultObject) Selector(name string) Method {
    command, ok := object.CommandMap[name]
    if !ok {
        method := object.class.Selector(name)
        if method == nil { 
            return nil
        }
        return method
    }
    return command.Method
}


func (object DefaultObject) Class() Object {
    return RootClass
}

const METHOD_MISSING = "method_missing"

func (object DefaultObject) Send(raku * Raku, message string, args ... interface {}) (Object, error) {    
    method := object.Selector(message)
    if (method != nil) {
        return method(object.Raku, message, object, args ...)
    }
    method = object.Selector(METHOD_MISSING)
    if (method != nil) {
        return method(object.Raku, message, object, args ...)
    }
    return nil, fmt.Errorf("Cannot send message %s to object %v.", message, object)
}

type DefaultClass struct {
    parent * Class
    DefaultObject
}

func (class DefaultClass) Parent() Object {
    return class.parent
}

type NilClass struct {
    DefaultClass
}

var Nil Object = &DefaultObject{NilClass};

var Root * Object = &DefaultObject{RootClass}

type Boolean struct {
    DefaultObject
}

var True  * Boolean = &Boolean{Root}
var False * Boolean = &Boolean{Root}


func (boolean Boolean) Parent() Object {
    return Nil
}

func (boolean Boolean) Send(raku * Raku, message string, args ... interface {}) (Object, error) {
    return Root.Send(raku, message, args ...);
}


func (method Method) Parent() Object {
    return Nil
}

func (method Method) Send(raku * Raku, message string, args ... interface {}) (Object, error) {
    return method(raku, message, method, args...) 
}




type Raku struct {
    * Parser
    CommandMap
    Root    * Object
    Nil     * NilClass    
    True    * Boolean
    False   * Boolean

}

func New(peg_filename string) (*Raku, error) {
    var err error
    result := &Raku{}
    result.Parser, err = LoadParser(peg_filename)
    if (err == nil) {
                
    } 
    return result, err
}


func Evaluate(raku * Raku, result Result) {
    _
}