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/client.go   | 29 +++++++++++++--
 internal/imap/commando.go | 92 +++++++++++++++++++++++++++++++++++++++++++++++
 internal/imap/imap.go     |  4 ++-
 3 files changed, 121 insertions(+), 4 deletions(-)
 create mode 100644 internal/imap/commando.go

(limited to 'internal/imap')

diff --git a/internal/imap/client.go b/internal/imap/client.go
index 3f004e2..da06f54 100644
--- a/internal/imap/client.go
+++ b/internal/imap/client.go
@@ -17,6 +17,7 @@ type Client struct {
 	mailboxes mailboxes
 	delimiter string
 	toplevel  Folder
+	commander *commander
 }
 
 type Folder struct {
@@ -50,6 +51,8 @@ func (mbs mailboxes) add(elem *imap.MailboxInfo) {
 
 func (client *Client) Disconnect() {
 	if client != nil {
+		client.stopCommander()
+
 		connected := (client.c.State() & imap.ConnectedState) != 0
 		_ = client.c.Logout()
 
@@ -119,7 +122,7 @@ func (client *Client) fetchDelimiter() error {
 	return nil
 }
 
-func (client *Client) EnsureFolder(folder Folder) error {
+func (client *Client) ensureFolder(folder Folder) error {
 	if client.mailboxes.contains(folder) {
 		return nil
 	}
@@ -146,6 +149,26 @@ func (client *Client) EnsureFolder(folder Folder) error {
 	}
 }
 
-func (client *Client) PutMessage(folder Folder, message string, date time.Time) error {
-	return client.c.Append(folder.String(), nil, date, strings.NewReader(message))
+func (client *Client) EnsureFolder(folder Folder, errorHandler ErrorHandler) {
+	client.commander.execute(ensureCommando{folder}, errorHandler)
+}
+
+func (client *Client) putMessages(folder Folder, messages []string) error {
+	if len(messages) == 0 {
+		return nil
+	}
+
+	now := time.Now()
+	for _, msg := range messages {
+		reader := strings.NewReader(msg)
+		if err := client.c.Append(folder.str, nil, now, reader); err != nil {
+			return fmt.Errorf("uploading message to %s: %w", folder, err)
+		}
+	}
+
+	return nil
+}
+
+func (client *Client) PutMessages(folder Folder, messages []string, errorHandler ErrorHandler) {
+	client.commander.execute(addCommando{folder, messages}, errorHandler)
 }
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
+}
diff --git a/internal/imap/imap.go b/internal/imap/imap.go
index f284f81..4965ca5 100644
--- a/internal/imap/imap.go
+++ b/internal/imap/imap.go
@@ -121,9 +121,11 @@ func Connect(url *url.URL) (*Client, error) {
 
 	log.Printf("Determined '%s' as toplevel, with '%s' as delimiter", client.toplevel, client.delimiter)
 
-	if err = client.EnsureFolder(client.toplevel); err != nil {
+	if err = client.ensureFolder(client.toplevel); err != nil {
 		return nil, err
 	}
 
+	client.startCommander()
+
 	return &client, nil
 }
-- 
cgit v1.2.3-70-g09d2