yack

Documentation

Overview

Package yack reads and runs yack dialogs.

The EBNF grammar for yack files:

SourceFile = { Line } .

Line = [ (LabelTag | ConditionalStatement) ] [ comment ] newline .

LabelTag = ":" label .

ConditionalStatement = Statement { Condition } .

Condition = "[" ("once" | "showonce" | "onceever" | "showonceever" |
                 "temponce" | actor_name | Code) "]" .

Statement = SayStmt | GotoStmt | ExecuteStmt | ChoiceStmt | ShutUpStmt |
            PauseStmt | WaitForStmt | WaitWhileStmt | ParrotStmt | DialogStmt |
            OverrideStmt | AllowObjectsStmt | LimitStmt .

SayStmt          = actor_name ":" string_lit [ GotoStmt ] .
GotoStmt         = "->" label .
ExecuteStmt      = "!" Code .
ChoiceStmt       = int_lit (string_lit | ("$" Code)) GotoStmt .
ShutUpStmt       = "shutup" .
PauseStmt        = "pause" float_lit .
WaitForStmt      = "waitfor" [ actor_name ] .
WaitWhileStmt    = "waitwhile" Code .
ParrotStmt       = "parrot" bool_lit .
DialogStmt       = "dialog" actor_name .
OverrideStmt     = "override" label .
AllowObjectsStmt = "allowobjects" bool_lit .
LimitStmt        = "limit" int_lit .

Code = /* Scripting language expression, e.g. Squirrel */ .

comment        = ";" { unicode_char } .
actor_name     = unicode_letter { unicode_letter | unicode_digit } .
label          = letter_uscore { letter_uscore | unicode_digit } .
letter_uscore  = unicode_letter | "_" .
bool_lit       = "yes" | "YES" | "no" | "NO" .
int_lit        = decimal_digits .
float_lit      = decimal_digits | decimal_digits "." [ decimal_digits ] |
                 "." decimal_digits .
decimal_digits = { decimal_digit } .
decimal_digit  = "0" … "9" .
string_lit     = `"` { unicode_value } `"` .
unicode_value  = unicode_char | escaped_char .
escaped_char   = `\` ( "n" | `\` | `"` ) .

newline        = /* the Unicode code point U+000A */ .
unicode_char   = /* an arbitrary Unicode code point except newline */ .
unicode_letter = /* a Unicode code point classified as "Letter" */ .
unicode_digit  = /* a Unicode code point classified as "Number, decimal digit" */ .

Index

• type ChoiceOption
• type Choices
  • func (c *Choices) Choose(index int) *Choices
• type ConditionalStatement
  • func (c ConditionalStatement) String() string
• type Dialog
  • func Load(path string) (*Dialog, error)
  • func Read(r io.Reader) (*Dialog, error)
  • func (d *Dialog) String() string
• type Runner
  • func NewRunner(s Scripting, t Talk, startActor string) *Runner
  • func (r *Runner) Start(d *Dialog) *Choices
  • func (r *Runner) StartAt(d *Dialog, label string) *Choices
• type Scripting
• type Talk

Types

type ChoiceOption

type ChoiceOption struct {
	Text string
	// contains filtered or unexported fields
}

type Choices

type Choices struct {
	Actor   string
	Options []*ChoiceOption
	// contains filtered or unexported fields
}

func (*Choices) Choose

func (c *Choices) Choose(index int) *Choices

type ConditionalStatement

type ConditionalStatement struct {
	Statement  stmt.Statement
	Conditions []cond.Condition
}

A ConditionalStatement is a statement guarded by zero or more conditions.

func (ConditionalStatement) String

func (c ConditionalStatement) String() string

String formats the conditional statement in yack syntax, e.g. "statement [condition1] [condition2] [condition3]"

type Dialog

type Dialog struct {
	Statements []ConditionalStatement
	Labels     map[string]int
}

Dialog is a parsed yack dialog. It consists of a sequence of statements, each one guarded by zero or more conditions, and a label index. Each label points via index to a statement in the statements slice.

func Load

func Load(path string) (*Dialog, error)

Load reads and parses a dialog from a yack file. File IO or syntax errors are returned as error.

func Read

func Read(r io.Reader) (*Dialog, error)

Read reads a dialog from a source in yack format. Syntax errors are returned as error.

func (*Dialog) String

func (d *Dialog) String() string

String formats the dialog in yack syntax.

type Runner

type Runner struct {
	// contains filtered or unexported fields
}

func NewRunner

func NewRunner(s Scripting, t Talk, startActor string) *Runner

func (*Runner) Start

func (r *Runner) Start(d *Dialog) *Choices

Start begins the given dialog at the "start" label and returns dialog choices when available. If the Options slice of the returned Choices object is empty the end of the dialog has been reached.

func (*Runner) StartAt

func (r *Runner) StartAt(d *Dialog, label string) *Choices

StartAt begins the given dialog at the specified label and returns choices. If the Options slice of the returned Choices object is empty the end of the dialog has been reached.

type Scripting

type Scripting interface {
	Eval(code string) (result any, err error)
}

Scripting provides an interface for the evaluation of expressions in a scripting language. It can be used to plug in an interpreter or VM for any scripting language, e.g. Squirrel, Lua or JavaScript.

type Talk

type Talk interface {
	// Say makes the actor say a text.
	Say(actor, text string)
	// ShutUp makes all actors stop talking.
	ShutUp()
}