From 9280ecb7e0b0039d6c1f4800373eb76452145078 Mon Sep 17 00:00:00 2001
From: René 'Necoro' Neumann <necoro@necoro.eu>
Date: Wed, 22 Apr 2020 23:40:53 +0200
Subject: Concurrent feed processing; central imap handler

---
 internal/imap/commando.go | 92 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 internal/imap/commando.go

(limited to 'internal/imap/commando.go')

diff --git a/internal/imap/commando.go b/internal/imap/commando.go
new file mode 100644
index 0000000..fbfeaec
--- /dev/null
+++ b/internal/imap/commando.go
@@ -0,0 +1,92 @@
+package imap
+
+import "github.com/Necoro/feed2imap-go/internal/log"
+
+const maxPipeDepth = 10
+
+type commander struct {
+	client *Client
+	pipe   chan<- execution
+	done   chan<- struct{}
+}
+
+type command interface {
+	execute(client *Client) error
+}
+
+type ErrorHandler func(error) string
+
+type execution struct {
+	cmd          command
+	done         chan<- struct{}
+	errorHandler ErrorHandler
+}
+
+type addCommando struct {
+	folder   Folder
+	messages []string
+}
+
+func (cmd addCommando) execute(client *Client) error {
+	return client.putMessages(cmd.folder, cmd.messages)
+}
+
+type ensureCommando struct {
+	folder Folder
+}
+
+func (cmd ensureCommando) execute(client *Client) error {
+	return client.ensureFolder(cmd.folder)
+}
+
+func (commander *commander) execute(command command, handler ErrorHandler) {
+	done := make(chan struct{})
+	commander.pipe <- execution{command, done, handler}
+	<-done
+}
+
+func executioner(client *Client, pipe <-chan execution, done <-chan struct{}) {
+	for {
+		select {
+		case <-done:
+			return
+		case execution := <-pipe:
+			select { // break as soon as done is there
+			case <-done:
+				return
+			default:
+			}
+			if err := execution.cmd.execute(client); err != nil {
+				if execution.errorHandler == nil {
+					log.Error(err)
+				} else {
+					log.Error(execution.errorHandler(err))
+				}
+			}
+			close(execution.done)
+		}
+	}
+}
+
+func (client *Client) startCommander() {
+	if client.commander != nil {
+		return
+	}
+
+	pipe := make(chan execution, maxPipeDepth)
+	done := make(chan struct{})
+
+	client.commander = &commander{client, pipe, done}
+
+	go executioner(client, pipe, done)
+}
+
+func (client *Client) stopCommander() {
+	if client.commander == nil {
+		return
+	}
+
+	close(client.commander.done)
+
+	client.commander = nil
+}
-- 
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