Hilbish/golibs/bait/bait.go

377 lines
9.0 KiB
Go

// the event emitter
/*
Bait is the event emitter for Hilbish. Much like Node.js and
its `events` system, many actions in Hilbish emit events.
Unlike Node.js, Hilbish events are global. So make sure to
pick a unique name!
Usage of the Bait module consists of userstanding
event-driven architecture, but it's pretty simple:
If you want to act on a certain event, you can `catch` it.
You can act on events via callback functions.
Examples of this are in the Hilbish default config!
Consider this part of it:
```lua
bait.catch('command.exit', function(code)
running = false
doPrompt(code ~= 0)
doNotifyPrompt()
end)
```
What this does is, whenever the `command.exit` event is thrown,
this function will set the user prompt.
*/
package bait
import (
"errors"
"hilbish/util"
rt "github.com/arnodel/golua/runtime"
"github.com/arnodel/golua/lib/packagelib"
)
type listenerType int
const (
goListener listenerType = iota
luaListener
)
// Recoverer is a function which is called when a panic occurs in an event.
type Recoverer func(event string, handler *Listener, err interface{})
// Listener is a struct that holds the handler for an event.
type Listener struct{
typ listenerType
once bool
caller func(...interface{})
luaCaller *rt.Closure
}
type Bait struct{
Loader packagelib.Loader
recoverer Recoverer
handlers map[string][]*Listener
rtm *rt.Runtime
}
// New creates a new Bait instance.
func New(rtm *rt.Runtime) *Bait {
b := &Bait{
handlers: make(map[string][]*Listener),
rtm: rtm,
}
b.Loader = packagelib.Loader{
Load: b.loaderFunc,
Name: "bait",
}
return b
}
// Emit throws an event.
func (b *Bait) Emit(event string, args ...interface{}) {
handles := b.handlers[event]
if handles == nil {
return
}
for idx, handle := range handles {
defer func() {
if err := recover(); err != nil {
b.callRecoverer(event, handle, err)
}
}()
if handle.typ == luaListener {
funcVal := rt.FunctionValue(handle.luaCaller)
var luaArgs []rt.Value
for _, arg := range args {
var luarg rt.Value
switch arg.(type) {
case rt.Value: luarg = arg.(rt.Value)
default: luarg = rt.AsValue(arg)
}
luaArgs = append(luaArgs, luarg)
}
_, err := rt.Call1(b.rtm.MainThread(), funcVal, luaArgs...)
if err != nil {
if event != "error" {
b.Emit("error", event, handle.luaCaller, err.Error())
return
}
// if there is an error in an error event handler, panic instead
// (calls the go recoverer function)
panic(err)
}
} else {
handle.caller(args...)
}
if handle.once {
b.removeListener(event, idx)
}
}
}
// On adds a Go function handler for an event.
func (b *Bait) On(event string, handler func(...interface{})) *Listener {
listener := &Listener{
typ: goListener,
caller: handler,
}
b.addListener(event, listener)
return listener
}
// OnLua adds a Lua function handler for an event.
func (b *Bait) OnLua(event string, handler *rt.Closure) *Listener {
listener :=&Listener{
typ: luaListener,
luaCaller: handler,
}
b.addListener(event, listener)
return listener
}
// Off removes a Go function handler for an event.
func (b *Bait) Off(event string, listener *Listener) {
handles := b.handlers[event]
for i, handle := range handles {
if handle == listener {
b.removeListener(event, i)
}
}
}
// OffLua removes a Lua function handler for an event.
func (b *Bait) OffLua(event string, handler *rt.Closure) {
handles := b.handlers[event]
for i, handle := range handles {
if handle.luaCaller == handler {
b.removeListener(event, i)
}
}
}
// Once adds a Go function listener for an event that only runs once.
func (b *Bait) Once(event string, handler func(...interface{})) *Listener {
listener := &Listener{
typ: goListener,
once: true,
caller: handler,
}
b.addListener(event, listener)
return listener
}
// OnceLua adds a Lua function listener for an event that only runs once.
func (b *Bait) OnceLua(event string, handler *rt.Closure) *Listener {
listener := &Listener{
typ: luaListener,
once: true,
luaCaller: handler,
}
b.addListener(event, listener)
return listener
}
// SetRecoverer sets the function to be executed when a panic occurs in an event.
func (b *Bait) SetRecoverer(recoverer Recoverer) {
b.recoverer = recoverer
}
func (b *Bait) addListener(event string, listener *Listener) {
if b.handlers[event] == nil {
b.handlers[event] = []*Listener{}
}
b.handlers[event] = append(b.handlers[event], listener)
}
func (b *Bait) removeListener(event string, idx int) {
b.handlers[event][idx] = b.handlers[event][len(b.handlers[event]) - 1]
b.handlers[event] = b.handlers[event][:len(b.handlers[event]) - 1]
}
func (b *Bait) callRecoverer(event string, handler *Listener, err interface{}) {
if b.recoverer == nil {
panic(err)
}
b.recoverer(event, handler, err)
}
func (b *Bait) loaderFunc(rtm *rt.Runtime) (rt.Value, func()) {
exports := map[string]util.LuaExport{
"catch": util.LuaExport{b.bcatch, 2, false},
"catchOnce": util.LuaExport{b.bcatchOnce, 2, false},
"throw": util.LuaExport{b.bthrow, 1, true},
"release": util.LuaExport{b.brelease, 2, false},
"hooks": util.LuaExport{b.bhooks, 1, false},
}
mod := rt.NewTable()
util.SetExports(rtm, mod, exports)
return rt.TableValue(mod), nil
}
func handleHook(t *rt.Thread, c *rt.GoCont, name string, catcher *rt.Closure, args ...interface{}) {
funcVal := rt.FunctionValue(catcher)
var luaArgs []rt.Value
for _, arg := range args {
var luarg rt.Value
switch arg.(type) {
case rt.Value: luarg = arg.(rt.Value)
default: luarg = rt.AsValue(arg)
}
luaArgs = append(luaArgs, luarg)
}
_, err := rt.Call1(t, funcVal, luaArgs...)
if err != nil {
e := rt.NewError(rt.StringValue(err.Error()))
e = e.AddContext(c.Next(), 1)
// panicking here won't actually cause hilbish to panic and instead will
// print the error and remove the hook (look at emission recover from above)
panic(e)
}
}
// catch(name, cb)
// Catches an event. This function can be used to act on events.
// #param name string The name of the hook.
// #param cb function The function that will be called when the hook is thrown.
/*
#example
bait.catch('hilbish.exit', function()
print 'Goodbye Hilbish!'
end)
#example
*/
func (b *Bait) bcatch(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
name, catcher, err := util.HandleStrCallback(t, c)
if err != nil {
return nil, err
}
b.OnLua(name, catcher)
return c.Next(), nil
}
// catchOnce(name, cb)
// Catches an event, but only once. This will remove the hook immediately after it runs for the first time.
// #param name string The name of the event
// #param cb function The function that will be called when the event is thrown.
func (b *Bait) bcatchOnce(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
name, catcher, err := util.HandleStrCallback(t, c)
if err != nil {
return nil, err
}
b.OnceLua(name, catcher)
return c.Next(), nil
}
// hooks(name) -> table
// Returns a table of functions that are hooked on an event with the corresponding `name`.
// #param name string The name of the hook
// #returns table<function>
func (b *Bait) bhooks(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
if err := c.Check1Arg(); err != nil {
return nil, err
}
evName, err := c.StringArg(0)
if err != nil {
return nil, err
}
noHooks := errors.New("no hooks for event " + evName)
handlers := b.handlers[evName]
if handlers == nil {
return nil, noHooks
}
luaHandlers := rt.NewTable()
for _, handler := range handlers {
if handler.typ != luaListener { continue }
luaHandlers.Set(rt.IntValue(luaHandlers.Len() + 1), rt.FunctionValue(handler.luaCaller))
}
if luaHandlers.Len() == 0 {
return nil, noHooks
}
return c.PushingNext1(t.Runtime, rt.TableValue(luaHandlers)), nil
}
// release(name, catcher)
// Removes the `catcher` for the event with `name`.
// For this to work, `catcher` has to be the same function used to catch
// an event, like one saved to a variable.
// #param name string Name of the event the hook is on
// #param catcher function Hook function to remove
/*
#example
local hookCallback = function() print 'hi' end
bait.catch('event', hookCallback)
-- a little while later....
bait.release('event', hookCallback)
-- and now hookCallback will no longer be ran for the event.
#example
*/
func (b *Bait) brelease(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
name, catcher, err := util.HandleStrCallback(t, c)
if err != nil {
return nil, err
}
b.OffLua(name, catcher)
return c.Next(), nil
}
// throw(name, ...args)
// #param name string The name of the hook.
// #param args ...any The arguments to pass to the hook.
// Throws a hook with `name` with the provided `args`.
/*
#example
bait.throw('greeting', 'world')
-- This can then be listened to via
bait.catch('gretting', function(greetTo)
print('Hello ' .. greetTo)
end)
#example
*/
func (b *Bait) bthrow(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
if err := c.Check1Arg(); err != nil {
return nil, err
}
name, err := c.StringArg(0)
if err != nil {
return nil, err
}
ifaceSlice := make([]interface{}, len(c.Etc()))
for i, v := range c.Etc() {
ifaceSlice[i] = v
}
b.Emit(name, ifaceSlice...)
return c.Next(), nil
}