Add a simple text file editor

The design is a bit unusual in comparison with our other components, but
keeping track of the complex state interactions is difficult enough on
its own, without getting React involved, so we use a separate class.

Co-Authored-By: Garrett LeSage <garrett@redhat.com>
Co-Authored-By: Jelle van der Waa <jelle@vdwaa.nl>

src/dialogs/editor.scss

@@ -0,0 +1,47 @@
+.file-editor-modal {
+  block-size: 100%;
+
+  &.is-modified {
+    // Add a background highlight on the modal itself
+    &::after {
+      background: linear-gradient(to bottom, var(--pf-v5-global--warning-color--100), transparent 0.33em);
+      content: '';
+      inset: 0;
+      pointer-events: none;
+      position: absolute;
+    }
+
+    // Add a circle to indicate that there are changes
+    .pf-v5-c-modal-box__title-text::after {
+      aspect-ratio: 1;
+      background: var(--pf-v5-global--warning-color--100);
+      block-size: 1cap;
+      border-radius: 0.5cap;
+      content: '';
+      display: inline-block;
+      margin-inline-start: 0.5cap;
+    }
+  }
+}
+
+.file-editor {
+  block-size: 100%;
+
+  textarea {
+    font-family: monospace;
+    hyphens: none;
+    white-space: wrap break-spaces;
+  }
+}
+
+.file-editor-alert {
+  margin-block-end: var(--pf-v5-global--spacer--md);
+}
+
+.file-editor-title-label {
+  margin-inline-start: var(--pf-v5-global--spacer--sm);
+
+  .pf-v5-theme-dark & {
+    background-color: var(--pf-v5-global--BackgroundColor--100);
+  }
+}

src/dialogs/editor.tsx

@@ -0,0 +1,258 @@
+/*
+ * This file is part of Cockpit.
+ *
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * Cockpit is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * Cockpit is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Cockpit; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import React from 'react';
+
+import { Alert, AlertActionLink } from '@patternfly/react-core/dist/esm/components/Alert';
+import { Button } from '@patternfly/react-core/dist/esm/components/Button';
+import { Label } from '@patternfly/react-core/dist/esm/components/Label';
+import { Modal, ModalVariant } from '@patternfly/react-core/dist/esm/components/Modal';
+import { TextArea } from '@patternfly/react-core/dist/esm/components/TextArea';
+import { Stack } from '@patternfly/react-core/dist/esm/layouts/Stack';
+import { debounce } from "throttle-debounce";
+
+import cockpit from 'cockpit';
+import { EventEmitter } from 'cockpit/event.ts';
+import type { Dialogs, DialogResult } from 'dialogs';
+
+import "./editor.scss";
+
+const _ = cockpit.gettext;
+
+// 1MB
+export const MAX_EDITOR_FILE_SIZE = 1000000;
+
+class EditorState {
+    /* eslint-disable-next-line @typescript-eslint/no-explicit-any */
+    error: any | null = null; // if there is an error to show
+    modified: boolean = false; // if there are unsaved changes
+    saving: boolean = false; // saving in progress?
+    tag_at_load: string | null = null; // the one we loaded
+    tag_now: string | null = null; // the one on disk
+    content: string = '';
+    writable: boolean = false;
+}
+
+/* eslint-disable-next-line @typescript-eslint/no-explicit-any */
+function translate_error(error: any) {
+    if (error.problem === "not-found") {
+        return _("The file has been removed on disk");
+    } else if (error?.problem === 'change-conflict') {
+        return _("The existing file changed unexpectedly");
+    } else {
+        return cockpit.message(error);
+    }
+}
+
+class Editor extends EventEmitter<{ updated(state: EditorState): void }> {
+    file: cockpit.FileHandle<string>;
+    state: EditorState;
+
+    update(updates: Partial<EditorState>) {
+        Object.assign(this.state, updates);
+        this.emit('updated', { ...this.state });
+    }
+
+    modify(content: string) {
+        this.update({ content, modified: true });
+    }
+
+    load_file() {
+        // Can't do this async because we can't get the tag via await
+        this.file.read()
+                .then(((content: string, tag: string) => {
+                    this.update({ content, tag_now: tag, tag_at_load: tag, error: null });
+                }) as any /* eslint-disable-line @typescript-eslint/no-explicit-any */)
+                .catch(error => this.update({ error }));
+    }
+
+    constructor(filename: string) {
+        super();
+        this.file = cockpit.file(filename, { max_read_size: MAX_EDITOR_FILE_SIZE, superuser: "try" });
+        this.state = new EditorState();
+
+        this.load_file();
+
+        cockpit.spawn(['test', '-w', filename], { superuser: "try" })
+                .then(() => this.update({ writable: true }))
+                .catch(() => this.update({ writable: false }));
+
+        const handle_watch = debounce(500, (_content: string | null, tag_now: string | null) => {
+            this.update({ tag_now });
+        });
+
+        this.file.watch(handle_watch, { read: false });
+    }
+
+    async save() {
+        if (!this.state.tag_now) {
+            console.error("Unable to save as 'tag_now' is not initialised");
+            return;
+        }
+
+        try {
+            const content = this.state.content;
+            const content_with_nl = content && !content.endsWith('\n') ? content + '\n' : content;
+
+            this.update({ saving: true });
+            const tag = await this.file.replace(content_with_nl, this.state.tag_now);
+            this.update({ saving: false, modified: false, tag_now: tag, tag_at_load: tag });
+        } catch (exc: any /* eslint-disable-line @typescript-eslint/no-explicit-any */) {
+            this.update({ error: exc, saving: false });
+        }
+    }
+
+    close() {
+        this.file.close();
+    }
+}
+
+export const EditFileModal = ({ dialogResult, path } : {
+    dialogResult: DialogResult<void>,
+    path: string
+}) => {
+    const [last_tag, setLastTag] = React.useState<string | null>(null);
+    const [state, setState] = React.useState(new EditorState());
+    const [editor, setEditor] = React.useState<Editor | null>(null);
+
+    React.useEffect(() => {
+        const editor = new Editor(path);
+        editor.on('updated', setState);
+        setEditor(editor);
+        return () => {
+            editor.close();
+        };
+    }, [path]);
+
+    const { modified } = state;
+    React.useEffect(() => {
+        const before_unload = (event: BeforeUnloadEvent) => {
+            event.preventDefault();
+
+            // Included for legacy support, e.g. Chrome/Edge < 119
+            event.returnValue = true;
+        };
+        if (modified) {
+            window.addEventListener('beforeunload', before_unload);
+            return () => {
+                window.removeEventListener('beforeunload', before_unload);
+            };
+        }
+    }, [modified]);
+
+    const handleEscape = (event: KeyboardEvent) => {
+        if (state?.modified) {
+            event.preventDefault();
+        } else {
+            dialogResult.resolve();
+        }
+    };
+
+    /* Translators: This is the title of a modal dialog.  $0 represents a filename. */
+    let title = <>{cockpit.format(state?.writable ? _("Edit “$0”") : _("View “$0”"), path)}</>;
+    if (!state.writable) {
+        // TODO: dark mode and lack of spacing
+        title = (<>{title}<Label className="file-editor-title-label" variant="filled">{_("Read-only")}</Label></>);
+    }
+
+    // File has changed on disk while editing.
+    const change_conflict = state.tag_now !== state.tag_at_load;
+    const file_removed = state.tag_now === "-";
+
+    return (
+        <Modal
+          position="top"
+          // @ts-expect-error incorrect PatternFly typing https://github.com/patternfly/patternfly-react/issues/10361
+          title={title}
+          isOpen
+          onClose={() => dialogResult.resolve()}
+          variant={ModalVariant.large}
+          className={`file-editor-modal ${modified ? 'is-modified' : ''}`}
+          onEscapePress={handleEscape}
+          footer={
+              <>
+                  {change_conflict && !file_removed &&
+                  <Button
+                    variant="warning"
+                    onClick={() => editor && editor.save()}
+                  >
+                      {_("Overwrite")}
+                  </Button>}
+                  {state?.writable && (!change_conflict || file_removed) &&
+                  <Button
+                    variant="primary"
+                    isDisabled={
+                        !editor ||
+                            state.saving ||
+                            !modified ||
+                            !state.writable
+                    }
+                    onClick={() => editor && editor.save()}
+                  >
+                      {_("Save")}
+                  </Button>}
+                  <Button variant={state.writable ? "link" : "secondary"} onClick={() => dialogResult.resolve()}>
+                      {modified ? _("Cancel") : _("Close")}
+                  </Button>
+              </>
+          }
+        >
+            <Stack>
+                {state.tag_now === state.tag_at_load && state.error !== null &&
+                <Alert
+                  className="file-editor-alert"
+                  variant="danger"
+                  title={translate_error(state.error)}
+                  isInline
+                />}
+                {state.tag_now !== state.tag_at_load && last_tag !== state.tag_now &&
+                <Alert
+                  className="file-editor-alert"
+                  isInline
+                  variant="warning"
+                  title={file_removed
+                      ? _("The file has been removed on disk")
+                      : _("The file has changed on disk")}
+                  actionLinks={
+                      <>
+                          {!file_removed &&
+                          <AlertActionLink onClick={() => editor && editor.load_file()}>
+                              {_("Reload")}
+                          </AlertActionLink>}
+                          <AlertActionLink onClick={() => setLastTag(state.tag_now)}>
+                              {_("Ignore")}
+                          </AlertActionLink>
+                      </>
+                  }
+                />}
+                <TextArea
+                  id="editor-text-area"
+                  className="file-editor"
+                  isDisabled={!state.writable}
+                  value={state.content}
+                  onChange={(_ev, content) => editor && editor.modify(content)}
+                />
+            </Stack>
+        </Modal>
+    );
+};
+
+export function edit_file(dialogs: Dialogs, path: string) {
+    dialogs.run(EditFileModal, { path });
+}

src/menu.tsx

@@ -28,6 +28,7 @@ import type { Dialogs } from 'dialogs';
 import type { FolderFileInfo } from "./app";
 import { basename } from "./common.ts";
 import { confirm_delete } from './dialogs/delete.tsx';
+import { edit_file, MAX_EDITOR_FILE_SIZE } from './dialogs/editor.tsx';
 import { show_create_directory_dialog } from './dialogs/mkdir.tsx';
 import { edit_permissions } from './dialogs/permissions.jsx';
 import { show_rename_dialog } from './dialogs/rename.tsx';
@@ -90,38 +91,54 @@ export function get_menu_items(
             }
         );
     } else if (selected.length === 1) {
+        const item = selected[0];
+        // Only allow code, text and unknown file types as we detect things by
+        // extensions, so not allowing unknown file types would disallow one
+        // from editing for example /etc/hostname
+        const allowed_edit_types = ["code-file", "text-file", "file"];
+        if (item.type === 'reg' &&
+            allowed_edit_types.includes(item?.category?.class || "") &&
+            item.size !== undefined && item.size < MAX_EDITOR_FILE_SIZE)
+            menuItems.push(
+                {
+                    id: "open-file",
+                    title: _("Open text file"),
+                    onClick: () => edit_file(dialogs, path + item.name)
+                },
+                { type: "divider" },
+            );
         menuItems.push(
             {
                 id: "copy-item",
                 title: _("Copy"),
-                onClick: () => setClipboard([path + selected[0].name]),
+                onClick: () => setClipboard([path + item.name])
             },
             { type: "divider" },
             {
                 id: "edit-permissions",
                 title: _("Edit permissions"),
-                onClick: () => edit_permissions(dialogs, selected[0], path)
+                onClick: () => edit_permissions(dialogs, item, path)
             },
             {
                 id: "rename-item",
                 title: _("Rename"),
-                onClick: () => show_rename_dialog(dialogs, path, selected[0])
+                onClick: () => show_rename_dialog(dialogs, path, item)
             },
             { type: "divider" },
             {
                 id: "delete-item",
                 title: _("Delete"),
                 className: "pf-m-danger",
-                onClick: () => confirm_delete(dialogs, path, selected, setSelected)
+                onClick: () => confirm_delete(dialogs, path, [item], setSelected)
             },
         );
-        if (selected[0].type === "reg")
+        if (item.type === "reg")
             menuItems.push(
                 { type: "divider" },
                 {
                     id: "download-item",
                     title: _("Download"),
-                    onClick: () => downloadFile(path, selected[0])
+                    onClick: () => downloadFile(path, item)
                 }
             );
     } else if (selected.length > 1) {