refactor: move packet definitions to their own file

I also decided to make the packet datatype package private.

2 files changed, 39 insertions, 33 deletions

diff --git a/packet.go b/packet.go
new file mode 100644
index 0000000..5b3a5ba
--- /dev/null
+++ b/packet.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"net/url"
+)
+
+// packet accrues data as it passes through our concurrent
+// pipeline. Formerly the web crawler only transmitted [url.URL]'s,
+// but usingn a compound data type allows us to add URL
+// depth-tracking.
+type packet struct {
+	url   url.URL
+	depth int
+}
+
+// String implements the Stringer interface. We need this mainly
+// because a [url.URL]'s String method only works when that URL is a
+// pointer.
+func (p packet) String() string {
+	return fmt.Sprintf("[%d] %s", p.depth, &p.url)
+}
+
+// convertToPackets converts the batch of URLs to a slice of packet
+// structs, configuring each one with the given depth.
+func convertToPackets(batch []url.URL, depth int) []packet {
+	var ps []packet
+
+	for _, u := range batch {
+		newPacket := packet{u, depth}
+		ps = append(ps, newPacket)
+	}
+
+	return ps
+}
diff --git a/workers.go b/workers.go
index 43e398d..4d646fd 100644
--- a/workers.go
+++ b/workers.go
@@ -14,32 +14,16 @@ import (
    - manages urls channel.
 */
 
-// Packet accrues data as it passes through our concurrent
-// pipeline. Formerly the web crawler only transmitted [url.URL]'s,
-// but usingn a compound data type allows us to add URL
-// depth-tracking.
-type Packet struct {
-	url   url.URL
-	depth int
-}
-
-// String implements the Stringer interface. We need this mainly
-// because a [url.URL]'s String method only works when that URL is a
-// pointer.
-func (p Packet) String() string {
-	return fmt.Sprintf("[%d] %s", p.depth, &p.url)
-}
-
 // workers launches a worker queue for crawling a given Web domain.
 func workers(startURL url.URL, maxConcurrency, maxURLs int) {
-	worklist := make(chan []Packet)
+	worklist := make(chan []packet)
 
 	// Unseen URLs.
-	packets := make(chan Packet)
+	packets := make(chan packet)
 
 	go func() {
-		startPacket := Packet{startURL, 0}
-		worklist <- []Packet{startPacket}
+		startPacket := packet{startURL, 0}
+		worklist <- []packet{startPacket}
 	}()
 
 	var wg sync.WaitGroup
@@ -105,16 +89,3 @@ loop:
 	cancel()
 	wg.Wait()
 }
-
-// convertToPackets converts the batch of URLs to a slice of Packet
-// structs, configuring each one with the given depth.
-func convertToPackets(batch []url.URL, depth int) []Packet {
-	var ps []Packet
-
-	for _, u := range batch {
-		newPacket := Packet{u, depth}
-		ps = append(ps, newPacket)
-	}
-
-	return ps
-}