[REF] mail, *: refactor messaging with OWL

This commit is a significant rewriting of client-side discuss, chatter,
chat window, and messaging menu using OWL. The behavior should be broadly
the same, with some slight functional changes here and there.

From a technical standpoint, the code of messaging is mainly organized in 2
main groups of modules:

- models, which are logical entities that depict the client-side state of
  messaging as a whole.
- components, which are in charge of displaying information from models.

This refactoring also introduces new JS guidelines regarding folder structure
(/static) and naming rules for JS modules.

Community PR: https://github.com/odoo/odoo/pull/39023
Enterprise PR: https://github.com/odoo/enterprise/pull/6249

Task-1914207

This PR is a collaborative work by Alexandre, Julien, Sébastien and Xavier,
with the precious help of Lucas to speed it up towards the end.

closes odoo/odoo#39023

Related: odoo/enterprise#6249
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>
Co-authored-by: Alexandre Kühn <aku@odoo.com>
Co-authored-by: Julien Giannone <jgi@odoo.com>
Co-authored-by: Lucas Perais <lpe@odoo.com>
Co-authored-by: Sébastien Theys <seb@odoo.com>
Co-authored-by: Xavier Dubuc <xdu@odoo.com>

3 files changed, 177 insertions, 0 deletions

diff --git a/addons/mail/static/src/components/drop_zone/drop_zone.js b/addons/mail/static/src/components/drop_zone/drop_zone.js
new file mode 100644
index 00000000000..2eb4dc8ef74
--- /dev/null
+++ b/addons/mail/static/src/components/drop_zone/drop_zone.js
@@ -0,0 +1,136 @@
+odoo.define('mail/static/src/components/drop_zone/drop_zone.js', function (require) {
+'use strict';
+
+const { Component, useState } = owl;
+
+class DropZone extends Component {
+
+    /**
+     * @override
+     */
+    constructor(...args) {
+        super(...args);
+        this.state = useState({
+            /**
+             * Determine whether the user is dragging files over the dropzone.
+             * Useful to provide visual feedback in that case.
+             */
+            isDraggingInside: false,
+        });
+        /**
+         * Counts how many drag enter/leave happened on self and children. This
+         * ensures the drop effect stays active when dragging over a child.
+         */
+        this._dragCount = 0;
+    }
+
+    //--------------------------------------------------------------------------
+    // Public
+    //--------------------------------------------------------------------------
+
+    /**
+     * Returns whether the given node is self or a children of self.
+     *
+     * @param {Node} node
+     * @returns {boolean}
+     */
+    contains(node) {
+        return this.el.contains(node);
+    }
+
+    //--------------------------------------------------------------------------
+    // Private
+    //--------------------------------------------------------------------------
+
+    /**
+     * Making sure that dragging content is external files.
+     * Ignoring other content dragging like text.
+     *
+     * @private
+     * @param {DataTransfer} dataTransfer
+     * @returns {boolean}
+     */
+    _isDragSourceExternalFile(dataTransfer) {
+        const dragDataType = dataTransfer.types;
+        if (dragDataType.constructor === window.DOMStringList) {
+            return dragDataType.contains('Files');
+        }
+        if (dragDataType.constructor === Array) {
+            return dragDataType.includes('Files');
+        }
+        return false;
+    }
+
+    //--------------------------------------------------------------------------
+    // Handlers
+    //--------------------------------------------------------------------------
+
+    /**
+     * Shows a visual drop effect when dragging inside the dropzone.
+     *
+     * @private
+     * @param {DragEvent} ev
+     */
+    _onDragenter(ev) {
+        ev.preventDefault();
+        if (this._dragCount === 0) {
+            this.state.isDraggingInside = true;
+        }
+        this._dragCount++;
+    }
+
+    /**
+     * Hides the visual drop effect when dragging outside the dropzone.
+     *
+     * @private
+     * @param {DragEvent} ev
+     */
+    _onDragleave(ev) {
+        this._dragCount--;
+        if (this._dragCount === 0) {
+            this.state.isDraggingInside = false;
+        }
+    }
+
+    /**
+     * Prevents default (from the template) in order to receive the drop event.
+     * The drop effect cursor works only when set on dragover.
+     *
+     * @private
+     * @param {DragEvent} ev
+     */
+    _onDragover(ev) {
+        ev.preventDefault();
+        ev.dataTransfer.dropEffect = 'copy';
+    }
+
+    /**
+     * Triggers the `o-dropzone-files-dropped` event when new files are dropped
+     * on the dropzone, and then removes the visual drop effect.
+     *
+     * The parents should handle this event to process the files as they wish,
+     * such as uploading them.
+     *
+     * @private
+     * @param {DragEvent} ev
+     */
+    _onDrop(ev) {
+        ev.preventDefault();
+        if (this._isDragSourceExternalFile(ev.dataTransfer)) {
+            this.trigger('o-dropzone-files-dropped', {
+                files: ev.dataTransfer.files,
+            });
+        }
+        this.state.isDraggingInside = false;
+    }
+
+}
+
+Object.assign(DropZone, {
+    props: {},
+    template: 'mail.DropZone',
+});
+
+return DropZone;
+
+});
diff --git a/addons/mail/static/src/components/drop_zone/drop_zone.scss b/addons/mail/static/src/components/drop_zone/drop_zone.scss
new file mode 100644
index 00000000000..e1a901cb12e
--- /dev/null
+++ b/addons/mail/static/src/components/drop_zone/drop_zone.scss
@@ -0,0 +1,29 @@
+// ------------------------------------------------------------------
+// Layout
+// ------------------------------------------------------------------
+
+.o_DropZone {
+    display: flex;
+    position: absolute;
+    left: 0;
+    bottom: 0;
+    height: 100%;
+    width: 100%;
+    z-index: 1;
+    align-items: center;
+    justify-content: center;
+}
+
+// ------------------------------------------------------------------
+// Style
+// ------------------------------------------------------------------
+
+.o_DropZone {
+    color: $o-enterprise-primary-color;
+    background: rgba(255, 255, 255, 0.9);
+    border: 2px dashed $o-enterprise-primary-color;
+
+    &.o-dragging-inside {
+        border-width: 5px;
+    }
+}
diff --git a/addons/mail/static/src/components/drop_zone/drop_zone.xml b/addons/mail/static/src/components/drop_zone/drop_zone.xml
new file mode 100644
index 00000000000..b3db940fde9
--- /dev/null
+++ b/addons/mail/static/src/components/drop_zone/drop_zone.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-name="mail.DropZone" owl="1">
+        <div class="o_DropZone" t-att-class="{ 'o-dragging-inside': state.isDraggingInside }" t-on-dragenter="_onDragenter" t-on-dragleave="_onDragleave" t-on-dragover="_onDragover" t-on-drop="_onDrop">
+            <h4>
+                Drag Files Here <i class="fa fa-download"/>
+            </h4>
+        </div>
+    </t>
+
+</templates>