// raku

/* Raku is an easy to use scripting language that can also be used easily interactively

Desired simplified syntax:

PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> EXPRESSION eox | BLOCK .
EXPRESSION -> word PARAMETERS.
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> word | VALUE | PARENTHESIS | BLOCK | operator.
PARENTHESIS -> bep PARAMETER eop .
BLOCK -> bob STATEMENTS eob .
VALUE -> string | long | double | symbol.


Desrired syntax (verified LL(1) on smlweb.cpsc.ucalgary.ca)

PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> EXPRESSION EOX  | DEFINITION | BLOCK .
DEFINITION -> define WORDOP WORDOPS BLOCK.
WORDOPS -> WORDOP WORDOPS | .
EXPRESSION -> WORDVALUE PARAMETERS.
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> WORDVALUE | PARENTHESIS | BLOCK | operator.
PARENTHESIS -> '(' EXPRESSION ')' | ot EXPRESSION ct.
BLOCK -> oe STATEMENTS ce | do STATEMENTS end .
WORDOP -> word | operator | a | the.
WORDVALUE -> word | VALUE | a | the.
VALUE -> string | number | symbol.
EOX -> eol | period.

Lexer:


Yet another syntax, which supports operators, but requires () to use them,
and [ ]  to indicate expressions inside expressions. 

PROGRAM -> STATEMENTS.

STATEMENTS -> STATEMENT STATEMENTS | .

STATEMENT ->
  EXPRESSION EOX
| BLOCK .

EXPRESSION -> 
  CALL
| PARENTHESIS
| RECTANGLE
.

CALL -> WORD PARAMETERS .
RECTANGLE -> '[' EXPRESSION ']' | 
with EXPRESSION end .
PARENTHESIS -> '(' OPERATION ')' 
| let OPERATION  end .
OPERATION -> PARAMETER OPLIST .
OPLIST -> op OPLIST | .
OP -> operator PARAMETER .
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> WORDVALUE | BLOCK | 
PARENTHESIS | RECTANGLE .
BLOCK -> '{' STATEMENTS '}' | do STATEMENTS end .
WORDVALUE -> word | VALUE | a | the.
VALUE -> string | number | symbol.
EOX -> '\n' .


Most simple "lisp but with less parenthesis" syntax:


PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> CALL | EOX | BLOCK .
BLOCK -> '{' STATEMENTS '}' .
CALL -> word PARAMETERS EOX .
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> WORDVALUE | BLOCK .
WORDVALUE -> word | VALUE .
VALUE -> string | number | symbol.
EOX -> '\n' .


LMore TCL-is allows operators in () and forces evaluation of blocks in [].

PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> 
  COMMAND
| SUBSTITUTION
| BLOCK
| EXPRESSION
| EOX 
.

BLOCK -> 
  '{' STATEMENTS '}' 
| do STATEMENTS end .

SUBSTITUTION ->
  '[' STATEMENTS ']'
| evaluate STATEMENTS end .

EXPRESSION -> 
  '(' EXPRBODY ')'
| calculate EXPRBODY end .

EXPRBODY -> OPERAND OPERANDS.
OPERANDS ->  operator OPERANDS | .
OPERAND -> PARAMETER .

COMMAND -> word PARAMETERS EOX .
ARGUMENTS -> WORDVALUE ARGUMENTS | .
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> WORDVALUE | SUBSTITUTION | EXPRESSION | BLOCK .
WORDVALUE -> word | VALUE .
VALUE -> string | number | symbol | true | false | nothing .
EOX -> '\n' .

set (door's state) to closed .


# Type a grammar here:
PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> 
  COMMAND
| SUBSTITUTION
| BLOCK
|  EXPRESSION
| EOX 
.

BLOCK -> 
  '{' STATEMENTS '}' 
| do STATEMENTS end .

SUBSTITUTION ->
  '[' STATEMENTS ']'
| evaluate STATEMENTS end .

EXPRESSION -> 
  '(' EXPRBODY ')'
| calculate EXPRBODY end .

EXPRBODY -> OPERAND OPERANDS.
OPERANDS ->  operator OPERANDS | .
OPERAND -> PARAMETER .

COMMAND -> word PARAMETERS EOX .
ARGUMENTS -> WORDVALUE ARGUMENTS | .
PARAMETERS -> PARAMETER PARAMETERS | .
PARAMETER -> WORDVALUE | SUBSTITUTION | EXPRESSION | BLOCK .
WORDVALUE -> word | VALUE .
VALUE -> string | number | symbol | true | false | nothing .
EOX -> '\n' .




# Or, this gramar, also useful as a generic command parser for 
# AIF or MUx itself. Though necessarily more complex .
PROGRAM -> STATEMENTS.
STATEMENTS -> STATEMENT STATEMENTS | .
STATEMENT -> 
  COMMAND
| SUBSTITUTION
| BLOCK
|  EXPRESSION
| EOX 
.

BLOCK -> 
  '{' STATEMENTS '}' 
| do STATEMENTS end .

SUBSTITUTION ->
  '[' STATEMENTS ']'
| evaluate STATEMENTS end .

EXPRESSION -> 
  '(' EXPRBODY ')'
| calculate EXPRBODY end .

EXPRBODY -> OPERAND OPERANDS.
OPERANDS ->  operator OPERANDS | .
OPERAND -> PARAMETER .

COMMAND -> word ARGUMENTS EOX .
ARGUMENTS -> ARGUMENT ARGUMENT_SEP ARGUMENTS | .
ARGUMENT_SEP -> ',' | preposition | article | . 
ARGUMENT -> LITERAL | SUBSTITUTION | EXPRESSION | BLOCK .
WORDLIT -> word | LITERAL .
LITERAL -> string | number | symbol | true | false | nothing .
EOX -> '\n' .





type Duration (is a) number
( also could say a Duration (is a) number )

type Effect (is an) integer

constant No Effect is 1
constant Healing Effect is an Effect which is 1 
the Damaging Effect is an Effect which is 2 
( the is another way to say constant / variable )

type Spell (is a) record (which) has  
    (a) name (which is a/as a) String
    (a) Duration
    (an) Effect
end



variable cure light is a Spell which has 
    name is "Cure Light"
    Duration is Duration 0.0
    Effect is Healing Effect
end
( could have been the cure light is a spell ... )

to cast (a) Spell at (a) Being do
( ... )
end 

to cast (a) s which is a Spell at (a) b which is a Being do
( ... )
end 

to add n1 which is a Number to n2 which is a Number do

end


to add one Number to another Number do
    one becomes one plus another
end

to duck do
    let text be "You duck"
    one becomes one plus another
end



type spellike (is an) interface which has 
    cast (a) at Being
end

type Spell aliases spell








cast cure light at Ben


English single word prepositions :

in
aboard
about
above
absent
across
after
against
along
alongside
amid
amidst
among
apropos
apud
around
as
astride
at
on
atop 
ontop
bar
before
behind
below
beneath
beside
besides
between
beyond
but
by
chez
circa
come
dehors
despite
down
during
except
for
from
in
inside
into
less
like
minus
near
nearer
nearest
notwithstanding
of
off
on
onto
opposite
out
outside
over
pace
past
per
post
pre
pro
qua
re
sans
save
short
since
than
through
thru
throughout
to
toward 
towards
under
underneath
unlike
until
up
upon
upside
versus
via
vice
vis-à-vis
with
within
without
worth





*/
package raku

import (
    "bytes"
    "errors"
    "fmt"
    "io"
    "reflect"
    "runtime"
    "strings"
    "unicode"

    // "gitlab.com/beoran/woe/graphviz"
    "gitlab.com/beoran/woe/monolog"
    "gitlab.com/beoran/woe/tree"
)


type TokenChannel chan *Token

type Lexer struct {
    Reader  io.Reader
    Positions []Position
    Token   Token
    rule    LexerRule
    Output  TokenChannel
    buffer  []byte
    runes   []rune
}

type LexerRule func(lexer *Lexer) LexerRule

func (me *Lexer) Last() Position {
    return me.Positions[1]
}

func (me *Lexer) Current() Position {
    return me.Positions[0]
}

func (me *Lexer) LastPtr() * Position {
    return &me.Positions[1]
}

func (me *Lexer) CurrentPtr() * Position {
    return &me.Positions[0]
}


func (me *Lexer) PushPosition(pos Position) {
    newpos := make([]Position, len(me.Positions) + 1)
    newpos[0] = pos
    for i := 1 ; i < len(me.Positions); i++ {
        newpos[i] = me.Positions[i-1]
    }
    me.Positions = newpos
}

func (me *Lexer) PushCurrentPosition()  {
    current := me.Current()
    me.PushPosition(current)
}

func (me *Lexer) PopPosition() * Position {
    if (len(me.Positions) <= 2) { 
        return nil
    }
    
    result := &me.Positions[0];
    newpos := make([]Position, len(me.Positions) - 1)
    for i := 1 ; i < len(me.Positions); i++ {
        newpos[i-1] = me.Positions[i]
    }    
    me.Positions = newpos
    return result
}


func (me *Lexer) Emit(t TokenType, v TokenText) {
    tok := &Token{t, v, me.Current()}
    me.Output <- tok
}

func (me *Lexer) Error(message string, args ...interface{}) {
    value := fmt.Sprintf(message, args...)
    monolog.Error("Lex Error: %s", value)
    me.Emit(TokenError, TokenText(value))
}

func LexError(me *Lexer) LexerRule {
    me.Error("Error")
    return nil
}

func (me *Lexer) SkipComment() bool {
    if me.Peek() == '#' {
        if me.Next() == '(' {
            return me.SkipNotIn(")")
        } else {
            return me.SkipNotIn("\r\n")
        }
    }
    return true
}

/* Returns whether or not a keyword was found, and if so, the TokenType
of the keyword.*/
func LookupKeyword(word string) (bool, TokenType) {
    kind, found := keywordMap[word]
    return found, kind
}

/* Returns whether or not a special operator or sigil was found, and if so,
returns the TokenTyp of the sigil.*/
func LookupSigil(sigil string) (bool, TokenType) {
    fmt.Printf("LookupSigil: %s\n", sigil)
    kind, found := sigilMap[sigil]
    return found, kind
}

func LexSigil(me *Lexer) LexerRule {
    me.Found(TokenType(me.Peek()))
    _ = me.Next()
    me.Advance()
    return LexNormal
}

func LexWord(me *Lexer) LexerRule {
    me.SkipNotIn(" \t\r\n'({[]})")

    iskw, kind := LookupKeyword(me.CurrentStringValue())
    if iskw {
        me.Found(kind)
    } else {
        me.Found(TokenWord)
    }
    return LexNormal
}

func LexSymbol(me *Lexer) LexerRule {
    me.SkipNotIn(" \t\r\n'({[]})")
    me.Found(TokenSymbol)
    return LexNormal
}

func LexNumber(me *Lexer) LexerRule {
    me.SkipNotIn(" \t\r\n'({[]})")
    me.Found(TokenNumber)
    return LexNormal
}

func LexWhitespace(me *Lexer) LexerRule {
    me.SkipWhitespace()
    me.Advance()
    return LexNormal
}

func LexComment(me *Lexer) LexerRule {
    if !me.SkipComment() {
        me.Error("Unterminated comment")
        return LexError
    }
    me.Advance()
    return LexNormal
}

func LexPunctuator(me *Lexer) LexerRule {
    me.Found(TokenType(me.Peek()))
    _ = me.Next()
    me.Advance()
    return LexNormal
}

func LexEOL(me *Lexer) LexerRule {
    me.SkipIn("\r\n")
    me.Found(TokenEOL)
    return LexNormal
}

func LexOperator(me *Lexer) LexerRule {
    me.SkipIn(operator_chars)
    me.Found(TokenOperator)
    return LexNormal
}

func lexEscape(me *Lexer) error {
    _ = me.Next()
    return nil
}

func LexString(me *Lexer) LexerRule {
    open := me.Peek()
    do_escape := open == '"'
    peek := me.Next()
    me.Advance()
    for ; peek != '\000'; peek = me.Next() {
        if do_escape && peek == '\\' {
            if err := lexEscape(me); err != nil {
                return LexError
            }
        } else if peek == open {
            me.Found(TokenString)
            _ = me.Next()
            me.Advance()
            return LexNormal
        }
    }
    me.Error("Unexpected EOF in string.")
    return nil
}

func LexNumberOrOperator(me *Lexer) LexerRule {
    if unicode.IsDigit(me.Next()) {
        return LexNumber
    } else {
        _ = me.Previous()
        return LexOperator
    }
}

func LexNormal(me *Lexer) LexerRule {
    peek := me.Peek()
    if peek == '#' {
        return LexComment
    } else if strings.ContainsRune(" \t", peek) {
        return LexWhitespace
    } else if strings.ContainsRune(".,;:", peek) {
        return LexPunctuator
    } else if strings.ContainsRune("([{}])", peek) {
        return LexSigil
    } else if strings.ContainsRune("$", peek) {
        return LexSymbol
    } else if strings.ContainsRune("\r\n", peek) {
        return LexEOL
    } else if strings.ContainsRune("+-", peek) {
        return LexNumberOrOperator
    } else if strings.ContainsRune("\"`", peek) {
        return LexString
    } else if peek == '\000' {
        me.Emit(TokenEOF, "")
        return nil
    } else if unicode.IsLetter(peek) {
        return LexWord
    } else if unicode.IsDigit(peek) {
        return LexNumber
    } else if strings.ContainsRune(operator_chars, peek) {
        return LexOperator
    } else {
        return LexError
    }
}

func OpenLexer(reader io.Reader) *Lexer {
    lexer := &Lexer{}
    lexer.Reader    = reader
    lexer.Output    = make(TokenChannel)
    lexer.Positions = make([]Position, 2)
    // lexer.buffer = new(byte[1024])
    return lexer
}

func (me *Lexer) ReadReaderOnce() (bool, error) {
    buffer := make([]byte, 1024)

    n, err := me.Reader.Read(buffer)
    monolog.Debug("read %v %d %v\n", buffer[:n], n, err)
    if n > 0 {
        me.buffer = append(me.buffer, buffer[:n]...)
        monolog.Debug("append  %s", me.buffer)
    }

    if err == io.EOF {
        return true, nil
    } else if err != nil {
        me.Error("Error reading from reader: %s", err)
        return true, err
    }
    return false, nil
}

func (me *Lexer) ReadReader() error {
    me.buffer = make([]byte, 0)
    more, err := me.ReadReaderOnce()
    for err == nil && more {
        more, err = me.ReadReaderOnce()
    }
    me.runes = bytes.Runes(me.buffer)

    return err
}

func (me *Lexer) Peek() rune {
    if (me.Current().Index) >= len(me.runes) {
        return '\000'
    }
    return me.runes[me.Current().Index]
}

func (me *Lexer) PeekNext() rune {
    if (me.Current().Index + 1) >= len(me.runes) {
        return '\000'
    }
    return me.runes[me.Current().Index+1]
}

func (me *Lexer) Next() rune {
    if me.Peek() == '\n' {
        me.CurrentPtr().Column = 0
        me.CurrentPtr().Row++
    }
    me.CurrentPtr().Index++
    if me.Current().Index >= len(me.runes) {
        //me.Emit(TokenEOF, "")
    }
    return me.Peek()
}

func (me *Lexer) Previous() rune {
    if me.Current().Index > 0 {
        me.CurrentPtr().Index--

        if me.Peek() == '\n' {
            me.CurrentPtr().Column = 0
            me.CurrentPtr().Row++
        }
    }
    return me.Peek()
}

func (me *Lexer) SkipRune() {
    _ = me.Next()
}

func (me *Lexer) SkipIn(set string) bool {
    for strings.ContainsRune(set, me.Next()) {
        monolog.Debug("SkipIn: %s %c\n", set, me.Peek())
        if me.Peek() == '\000' {
            return false
        }
    }
    return true
}

func (me *Lexer) SkipNotIn(set string) bool {
    _ = me.Next()
    for !strings.ContainsRune(set, me.Peek()) {
        if me.Next() == '\000' {
            return false
        }
    }
    return true
}

func (me *Lexer) SkipWhile(should_skip func(r rune) bool) bool {
    for should_skip(me.Peek()) {
        if me.Next() == '\000' {
            return false
        }
    }
    return true
}

func (me *Lexer) SkipWhitespace() {
    me.SkipIn(" \t")
}

func (me *Lexer) Advance() {
    (*me.LastPtr()) = me.Current()
}

func (me *Lexer) Rewind() {
    (*me.CurrentPtr()) = me.Last()
}

func (me *Lexer) CurrentRuneValue() []rune {
    return me.runes[me.Last().Index:me.Current().Index]
}

func (me *Lexer) CurrentStringValue() string {
    return string(me.CurrentRuneValue())
}

func (me *Lexer) Found(kind TokenType) {
    me.Emit(kind, TokenText(me.CurrentStringValue()))
    me.Advance()
}

func GetFunctionName(fun interface{}) string {
    return runtime.FuncForPC(reflect.ValueOf(fun).Pointer()).Name()
}

func (me *Lexer) Start() {
    if err := me.ReadReader(); err == nil || err == io.EOF {
        rule := LexNormal
        for rule != nil {
            monolog.Debug("Lexer Rule: %s\n", GetFunctionName(rule))
            rule = rule(me)
        }
    } else {
        me.Error("Could not read in input buffer: %s", err)
    }
    close(me.Output)
}

func (me *Lexer) TryLexing() {
    go me.Start()

    for token := range me.Output {
        monolog.Info("Token %s", token)
    }
}

type AstType int

const (
    AstTypeProgram = AstType(iota)
    AstTypeStatements
    AstTypeStatement
    AstTypeDefinition
    AstTypeWords
    AstTypeExpression
    AstTypeWordExpression
    AstTypeWordCallop
    AstTypeOperation
    AstTypeOperations
    AstTypeCallArgs
    AstTypeValueExpression
    AstTypeValueCallop
    AstTypeParametersNonempty
    AstTypeParameters
    AstTypeParameter
    AstTypeBlock
    AstTypeWordValue
    AstTypeWord
    AstTypeValue
    AstTypeEox
    AstTypeOperator
    AstTypeParenthesis
    AstTypeModifier
    AstTypeError
)

var astTypeMap map[AstType]string = map[AstType]string{
    AstTypeProgram:            "Program",
    AstTypeStatements:         "Statements",
    AstTypeStatement:          "Statement",
    AstTypeDefinition:         "Definition",
    AstTypeWords:              "Words",
    AstTypeExpression:         "Expression",
    AstTypeWordExpression:     "WordExpression",
    AstTypeWordCallop:         "WordCallop",
    AstTypeOperation:          "Operation",
    AstTypeOperations:         "Operations",
    AstTypeCallArgs:           "CallArgs",
    AstTypeValueExpression:    "ValueExpression",
    AstTypeValueCallop:        "ValueCallop",
    AstTypeParametersNonempty: "ParametersNonempty",
    AstTypeParameters:         "Parameters",
    AstTypeParameter:          "Parameter",
    AstTypeBlock:              "Block",
    AstTypeWordValue:          "WordValue",
    AstTypeWord:               "Word",
    AstTypeValue:              "Value",
    AstTypeEox:                "Eox",
    AstTypeOperator:           "Operator",
    AstTypeParenthesis:        "Parenthesis",
    AstTypeModifier:           "Modifier",
    AstTypeError:              "Error",
}

func (me AstType) String() string {
    name, found := astTypeMap[me]
    if found {
        return name
    } else {
        return fmt.Sprintf("Unknown AstType %d", int(me))
    }
}

type Ast struct {
    tree.Node
    AstType
    *Token
}

func (me *Ast) Run(run *Runtime) (*Value, error) {
    switch me.AstType {
    case AstTypeProgram:
        return me.RunProgram(run)
    case AstTypeStatements:
        return me.RunStatements(run)
    case AstTypeStatement:
        return me.RunStatement(run)
    case AstTypeDefinition:
        return me.RunDefinition(run)
    case AstTypeWords:
        return me.RunWords(run)
    case AstTypeExpression:
        return me.RunExpression(run)
    case AstTypeWordExpression:
        return me.RunWord(run)
    case AstTypeWordCallop:
        return me.RunWordCallop(run)
    case AstTypeOperation:
        return me.RunOperation(run)
    case AstTypeOperations:
        return me.RunOperations(run)
    case AstTypeCallArgs:
        return me.RunCallArgs(run)
    case AstTypeValueExpression:
        return me.RunValueExpression(run)
    case AstTypeValueCallop:
        return me.RunValueCallop(run)
    case AstTypeParametersNonempty:
        return me.RunParametersNonempty(run)
    case AstTypeParameters:
        return me.RunParameters(run)
    case AstTypeParameter:
        return me.RunParameter(run)
    case AstTypeBlock:
        return me.RunBlock(run)
    case AstTypeWordValue:
        return me.RunWordValue(run)
    case AstTypeWord:
        return me.RunWord(run)
    case AstTypeValue:
        return me.RunValue(run)
    case AstTypeEox:
        return me.RunEox(run)
    case AstTypeOperator:
        return me.RunOperator(run)
    case AstTypeParenthesis:
        return me.RunParenthesis(run)
    case AstTypeModifier:
        return me.RunModifier(run)
    case AstTypeError:
        return me.RunError(run)
    default:
        return nil, errors.New("Shoudln't happen")
    }
}

func (me *Ast) RunProgram(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunStatements(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunStatement(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunDefinition(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunWords(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunExpression(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunWordExpression(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunWordCallop(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunOperation(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunOperations(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunCallArgs(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunValueExpression(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunValueCallop(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunParametersNonempty(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunParameters(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunParameter(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunBlock(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunWordValue(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunWord(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunValue(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunEox(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunOperator(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunParenthesis(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunModifier(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}
func (me *Ast) RunError(run *Runtime) (*Value, error) {
    return nil, errors.New("Not implemented")
}

func (me *Ast) NewChild(kind AstType, token *Token) *Ast {
    child := &Ast{}
    child.AstType = kind
    child.Token = token
    tree.AppendChild(me, child)
    return child
}

func (me *Ast) Walk(walker func(ast *Ast) *Ast) *Ast {
    node_res := tree.Walk(me,
        func(node tree.Noder) tree.Noder {
            ast_res := walker(node.(*Ast))
            if ast_res == nil {
                return nil
            } else {
                return ast_res
            }
        })
    if node_res != nil {
        return node_res.(*Ast)
    } else {
        return nil
    }
}

func (me *Ast) Remove() {
    _ = tree.Remove(me)
}

func NewAst(kind AstType) *Ast {
    ast := &Ast{}
    ast.AstType = kind
    ast.Token = nil
    return ast
}


type DefineType int

const (
    DefineTypeNone = DefineType(iota)
    DefineTypeGo
    DefineTypeUser
    DefineTypeVar
)



type Variable struct {
    Value
    Name string
}

type DefinePattern struct {
    Parts []string
}

type GoDefineFunc func(runtime *Runtime, args ...Value) Value

type ScriptDefine struct {
    DefineType
    DefinePattern
    *Ast
}

type GoDefine struct {
    DefineType
    *DefinePattern
    GoDefineFunc
}

type Define interface {
}

type Environment struct {
    Parent    *Environment
    Defines   map[string]Define
    Variables map[string]*Variable
    Stack     []Value
}

type Instruction int

const (
    InstructionNop = Instruction(iota)
    InstructionCall
    InstructionPush
    InstructionPop
)

func (env *Environment) AddDefine(name string, def Define) {
    env.Defines[name] = def
}

func (env *Environment) NewGoDefine(name string, fn GoDefineFunc, pattern ...string) {
    defpattern := new(DefinePattern)
    defpattern.Parts = append(defpattern.Parts, pattern...)
    godefine := &GoDefine{DefineTypeGo, defpattern, fn}
    env.AddDefine(name, godefine)
}

type Runtime struct {
    Environment
    start *Ast
    now   *Ast
}

func RuntimePuts(runtime *Runtime, args ...Value) Value {
    var iargs []interface{}
    for arg := range args {
        iargs = append(iargs, arg)
    }
    fmt.Print(iargs)
    return true
}

func (run *Runtime) Init() {
    run.NewGoDefine("puts", RuntimePuts, "$", "*")
}

func (run *Runtime) Start(ast *Ast) {
    run.start = ast
    run.now = ast
}

func (run *Runtime) RunOnce() {
    // run.now.Node
}

func main() {
    fmt.Println("Hello World!")
}