make client more configurable

client.go

@@ -3,6 +3,7 @@ package eventsource
 import (
 	"context"
 	"io"
+	"log"
 	"net/http"
 	"sync"
 	"time"
@@ -11,14 +12,20 @@ import (
 // Client wraps an http connection and converts it to an
 // event stream.
 type Client struct {
-	flusher  http.Flusher
-	write    io.Writer
-	ctx      context.Context
-	events   chan Event
-	closed   bool
-	waiter   sync.WaitGroup
-	lock     sync.Mutex
-	flushing *time.Timer
+	flusher      http.Flusher
+	write        io.Writer
+	ctx          context.Context
+	events       chan Event
+	closed       bool
+	waiter       sync.WaitGroup
+	lock         sync.Mutex
+	flushing     *time.Timer
+	flushLatency time.Duration
+}
+
+type Options struct {
+	ChannelSize  int
+	FlushLatency time.Duration
 }
 
 // NewClient creates a client wrapping a response writer.
@@ -27,10 +34,28 @@ type Client struct {
 // original http.Request helps determine which headers, but the request it is
 // optional.
 // Returns nil on error.
-func NewClient(w http.ResponseWriter, req *http.Request) *Client {
+func NewClient(w http.ResponseWriter, req *http.Request, options ...Options) *Client {
+	if len(options) > 1 {
+		log.Panicln("only one Options value may be provided")
+	}
+
+	flushLatency := 100 * time.Millisecond
+	channelSize := 100
+
+	if len(options) == 1 {
+		options := options[0]
+		if options.FlushLatency > 0 {
+			flushLatency = options.FlushLatency
+		}
+		if options.ChannelSize > 0 {
+			channelSize = options.ChannelSize
+		}
+	}
+
 	c := &Client{
-		events: make(chan Event, 100),
-		write:  w,
+		events:       make(chan Event, channelSize),
+		write:        w,
+		flushLatency: flushLatency,
 	}
 
 	// Check to ensure we support flushing
@@ -122,7 +147,7 @@ func (c *Client) run() {
 			c.lock.Lock()
 			io.Copy(c.write, &ev)
 			if c.flushing == nil {
-				c.flushing = time.AfterFunc(100*time.Millisecond, c.flush)
+				c.flushing = time.AfterFunc(c.flushLatency, c.flush)
 			}
 			c.lock.Unlock()