[geary/mjog/mail-merge-plugin: 147/157] Plugin.Email: Add load_body_as method and implement it

[Michael Gratton <mjog src gnome org>]

commit 13754d377f8b9775af402a8ecf8e05b40a4498ae
Author: Michael Gratton <mike vee net>
Date:   Thu May 7 17:25:31 2020 +1000

    Plugin.Email: Add load_body_as method and implement it
    
    Allows email plugins access to email boxy text.

 .../application-email-store-factory.vala           | 34 ++++++++++++++++++++
 src/client/plugin/plugin-email.vala                | 36 ++++++++++++++++++++++
 2 files changed, 70 insertions(+)
---
diff --git a/src/client/application/application-email-store-factory.vala 
b/src/client/application/application-email-store-factory.vala
index 542ab5022..6816dbaa3 100644
--- a/src/client/application/application-email-store-factory.vala
+++ b/src/client/application/application-email-store-factory.vala
@@ -189,6 +189,40 @@ internal class Application.EmailStoreFactory : Geary.BaseObject {
             return Util.Email.get_primary_originator(this.backing);
         }
 
+        public async string load_body_as(Plugin.Email.BodyType type,
+                                         bool convert,
+                                         GLib.Cancellable? cancellable)
+            throws GLib.Error {
+            if (!(Geary.Email.REQUIRED_FOR_MESSAGE in this.backing.fields)) {
+                Geary.Account account = this.account.backing.account;
+                this.backing = yield account.local_fetch_email_async(
+                    this.backing.id,
+                    Geary.Email.REQUIRED_FOR_MESSAGE | this.backing.fields,
+                    cancellable
+                );
+            }
+
+            Geary.RFC822.Message message = this.backing.get_message();
+            string body = "";
+            switch (type) {
+            case PLAIN:
+                if (message.has_plain_body()) {
+                    body = message.get_plain_body(false, null) ?? "";
+                } else {
+                    body = message.get_searchable_body(false) ?? "";
+                }
+                break;
+
+            case HTML:
+                if (message.has_html_body()) {
+                    body = message.get_html_body(null) ?? "";
+                } else {
+                    body = message.get_plain_body(true, null) ?? "";
+                }
+                break;
+            }
+            return body;
+        }
     }
 
 
diff --git a/src/client/plugin/plugin-email.vala b/src/client/plugin/plugin-email.vala
index 1ae5b0853..1a9656c33 100644
--- a/src/client/plugin/plugin-email.vala
+++ b/src/client/plugin/plugin-email.vala
@@ -15,6 +15,15 @@ public interface Plugin.Email :
     Geary.EmailHeaderSet {
 
 
+    /** Defines the formats that email body text can be loaded as. */
+    public enum BodyType {
+        /** Specifies `text/plain` body parts. */
+        PLAIN,
+        /** Specifies `text/html` body parts. */
+        HTML;
+    }
+
+
     /** Returns a unique identifier for this email. */
     public abstract EmailIdentifier identifier { get; }
 
@@ -31,6 +40,33 @@ public interface Plugin.Email :
      */
     public abstract Geary.RFC822.MailboxAddress? get_primary_originator();
 
+    /**
+     * Load the text of the email body as the given type.
+     *
+     * This method traverses the MIME multipart structure of the email
+     * body finding inline text parts and assembles them into a
+     * complete email body, as would be displayed to a person reading
+     * the email. If multiple matching parts are found, they will be
+     * concatenated.
+     *
+     * If no alternative parts for the requested type exist and
+     * `convert` is true, if alternatives for other supported types
+     * are present, an attempt will be made to convert to the
+     * requested type. For example, requesting HTML for an email with
+     * plain text only will attempt to reformat the plain text by
+     * inserting HTML tags. Otherwise an {@link Error.NOT_SUPPORTED}
+     * error is thrown.
+     *
+     * An error will be thrown if no body parts could be found, for
+     * example if an email has not completely been downloaded from the
+     * server.
+     */
+    public abstract async string load_body_as(
+        BodyType type,
+        bool convert,
+        GLib.Cancellable? cancellable
+    ) throws GLib.Error;
+
 }