govendor

vendor/github.com/fluffle/goirc/client/dispatch.go

@@ -0,0 +1,192 @@
+package client
+
+import (
+	"github.com/fluffle/goirc/logging"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+// Handlers are triggered on incoming Lines from the server, with the handler
+// "name" being equivalent to Line.Cmd. Read the RFCs for details on what
+// replies could come from the server. They'll generally be things like
+// "PRIVMSG", "JOIN", etc. but all the numeric replies are left as ascii
+// strings of digits like "332" (mainly because I really didn't feel like
+// putting massive constant tables in).
+//
+// Foreground handlers have a guarantee of protocol consistency: all the
+// handlers for one event will have finished before the handlers for the
+// next start processing. They are run in parallel but block the event
+// loop, so care should be taken to ensure these handlers are quick :-)
+//
+// Background handlers are run in parallel and do not block the event loop.
+// This is useful for things that may need to do significant work.
+type Handler interface {
+	Handle(*Conn, *Line)
+}
+
+// Removers allow for a handler that has been previously added to the client
+// to be removed.
+type Remover interface {
+	Remove()
+}
+
+// HandlerFunc allows a bare function with this signature to implement the
+// Handler interface. It is used by Conn.HandleFunc.
+type HandlerFunc func(*Conn, *Line)
+
+func (hf HandlerFunc) Handle(conn *Conn, line *Line) {
+	hf(conn, line)
+}
+
+// Handlers are organised using a map of linked-lists, with each map
+// key representing an IRC verb or numeric, and the linked list values
+// being handlers that are executed in parallel when a Line from the
+// server with that verb or numeric arrives.
+type hSet struct {
+	set map[string]*hList
+	sync.RWMutex
+}
+
+type hList struct {
+	start, end *hNode
+}
+
+// Storing the forward and backward links in the node allows O(1) removal.
+// This probably isn't strictly necessary but I think it's kinda nice.
+type hNode struct {
+	next, prev *hNode
+	set        *hSet
+	event      string
+	handler    Handler
+}
+
+// A hNode implements both Handler (with configurable panic recovery)...
+func (hn *hNode) Handle(conn *Conn, line *Line) {
+	defer conn.cfg.Recover(conn, line)
+	hn.handler.Handle(conn, line)
+}
+
+// ... and Remover.
+func (hn *hNode) Remove() {
+	hn.set.remove(hn)
+}
+
+func handlerSet() *hSet {
+	return &hSet{set: make(map[string]*hList)}
+}
+
+// When a new Handler is added for an event, it is wrapped in a hNode and
+// returned as a Remover so the caller can remove it at a later time.
+func (hs *hSet) add(ev string, h Handler) Remover {
+	hs.Lock()
+	defer hs.Unlock()
+	ev = strings.ToLower(ev)
+	l, ok := hs.set[ev]
+	if !ok {
+		l = &hList{}
+	}
+	hn := &hNode{
+		set:     hs,
+		event:   ev,
+		handler: h,
+	}
+	if !ok {
+		l.start = hn
+	} else {
+		hn.prev = l.end
+		l.end.next = hn
+	}
+	l.end = hn
+	hs.set[ev] = l
+	return hn
+}
+
+func (hs *hSet) remove(hn *hNode) {
+	hs.Lock()
+	defer hs.Unlock()
+	l, ok := hs.set[hn.event]
+	if !ok {
+		logging.Error("Removing node for unknown event '%s'", hn.event)
+		return
+	}
+	if hn.next == nil {
+		l.end = hn.prev
+	} else {
+		hn.next.prev = hn.prev
+	}
+	if hn.prev == nil {
+		l.start = hn.next
+	} else {
+		hn.prev.next = hn.next
+	}
+	hn.next = nil
+	hn.prev = nil
+	hn.set = nil
+	if l.start == nil || l.end == nil {
+		delete(hs.set, hn.event)
+	}
+}
+
+func (hs *hSet) dispatch(conn *Conn, line *Line) {
+	hs.RLock()
+	defer hs.RUnlock()
+	ev := strings.ToLower(line.Cmd)
+	list, ok := hs.set[ev]
+	if !ok {
+		return
+	}
+	wg := &sync.WaitGroup{}
+	for hn := list.start; hn != nil; hn = hn.next {
+		wg.Add(1)
+		go func(hn *hNode) {
+			hn.Handle(conn, line.Copy())
+			wg.Done()
+		}(hn)
+	}
+	wg.Wait()
+}
+
+// Handle adds the provided handler to the foreground set for the named event.
+// It will return a Remover that allows that handler to be removed again.
+func (conn *Conn) Handle(name string, h Handler) Remover {
+	return conn.fgHandlers.add(name, h)
+}
+
+// HandleBG adds the provided handler to the background set for the named
+// event. It may go away in the future.
+// It will return a Remover that allows that handler to be removed again.
+func (conn *Conn) HandleBG(name string, h Handler) Remover {
+	return conn.bgHandlers.add(name, h)
+}
+
+func (conn *Conn) handle(name string, h Handler) Remover {
+	return conn.intHandlers.add(name, h)
+}
+
+// HandleFunc adds the provided function as a handler in the foreground set
+// for the named event.
+// It will return a Remover that allows that handler to be removed again.
+func (conn *Conn) HandleFunc(name string, hf HandlerFunc) Remover {
+	return conn.Handle(name, hf)
+}
+
+func (conn *Conn) dispatch(line *Line) {
+	// We run the internal handlers first, including all state tracking ones.
+	// This ensures that user-supplied handlers that use the tracker have a
+	// consistent view of the connection state in handlers that mutate it.
+	conn.intHandlers.dispatch(conn, line)
+	go conn.bgHandlers.dispatch(conn, line)
+	conn.fgHandlers.dispatch(conn, line)
+}
+
+// LogPanic is used as the default panic catcher for the client. If, like me,
+// you are not good with computer, and you'd prefer your bot not to vanish into
+// the ether whenever you make unfortunate programming mistakes, you may find
+// this useful: it will recover panics from handler code and log the errors.
+func (conn *Conn) LogPanic(line *Line) {
+	if err := recover(); err != nil {
+		_, f, l, _ := runtime.Caller(2)
+		logging.Error("%s:%d: panic: %v", f, l, err)
+	}
+}