From 32f20dda222eec551f4967bc1bd16299f408a6c9 Mon Sep 17 00:00:00 2001
From: nasa9084 <nasa.9084.bassclarinet@gmail.com>
Date: Tue, 30 Jun 2020 01:23:13 +0900
Subject: [PATCH] add: support apply filter to existing emails

---
 commands/apply.go | 10 +++++++++-
 commands/util.go  |  1 +
 gmail/filter.go   | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/commands/apply.go b/commands/apply.go
index fdde775..a1c7457 100644
--- a/commands/apply.go
+++ b/commands/apply.go
@@ -21,7 +21,8 @@ func init() {
 }
 
 type ApplyCommand struct {
-	Target string `short:"f" long:"filename" required:"yes"`
+	Target                string `short:"f" long:"filename" required:"yes"`
+	ApplyToExistingEmails bool   `short:"e" long:"apply-to-existing"`
 }
 
 func (cmd *ApplyCommand) Execute([]string) error {
@@ -95,6 +96,13 @@ func (cmd *ApplyCommand) applyFilter(data []byte) error {
 		if err := c.CreateFilter(ctx, filter); err != nil {
 			return err
 		}
+
+		if cmd.ApplyToExistingEmails {
+			log.Printf("Apply filter %s to existing emails", filter.String())
+			if err := c.ApplyLabelToExistingEmail(ctx, filter); err != nil {
+				return err
+			}
+		}
 	}
 
 	return nil
diff --git a/commands/util.go b/commands/util.go
index d2f3457..5f82212 100644
--- a/commands/util.go
+++ b/commands/util.go
@@ -20,6 +20,7 @@ import (
 
 var oauthScope = []string{
 	gmail.GmailLabelsScope,
+	gmail.GmailModifyScope,
 	gmail.GmailSettingsBasicScope,
 }
 
diff --git a/gmail/filter.go b/gmail/filter.go
index e4f225d..a78f9a1 100644
--- a/gmail/filter.go
+++ b/gmail/filter.go
@@ -109,6 +109,55 @@ func (c *Client) DeleteFilterByID(ctx context.Context, id string) error {
 	return nil
 }
 
+func (c *Client) ApplyLabelToExistingEmail(ctx context.Context, filter Filter) error {
+	if filter.Action.AddLabel == "" {
+		return nil
+	}
+
+	gf, err := c.convertFilterToGmail(filter)
+	if err != nil {
+		return err
+	}
+
+	if err := c.svc.Users.Messages.List("me").Q(filter.Criteria.String()).MaxResults(999).Pages(
+		ctx,
+		func(msgsResp *gmail.ListMessagesResponse) error {
+			if len(msgsResp.Messages) == 0 {
+				return nil
+			}
+
+			messageIDs := make([]string, 0, len(msgsResp.Messages))
+
+			for _, msg := range msgsResp.Messages {
+				messageIDs = append(messageIDs, msg.Id)
+			}
+
+			var begin int
+			for begin < len(messageIDs) {
+				end := begin + 1000
+				if len(messageIDs) < end {
+					end = len(messageIDs)
+				}
+				batchModifyMessagesRequest := &gmail.BatchModifyMessagesRequest{
+					AddLabelIds:    gf.Action.AddLabelIds,
+					RemoveLabelIds: gf.Action.RemoveLabelIds,
+					Ids:            messageIDs[begin:end],
+				}
+
+				if err := c.svc.Users.Messages.BatchModify("me", batchModifyMessagesRequest).Context(ctx).Do(); err != nil {
+					return err
+				}
+				begin = end
+			}
+			return nil
+		},
+	); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (c *Client) convertFilterFromGmail(gf *gmail.Filter) Filter {
 	var f Filter
 	f.id = gf.Id