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feat: Prevent local PouchDB modification to be replicated to remote DB #1243

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@Ldoppea Ldoppea commented Sep 13, 2024

For now we don't want to replicate local changes into remote PouchDB as we first want to ensure everything works as expected locally before activating two-way replication in the future

In previous commits we configured the application's cozy-client to use
CozyPouchLink

This link is configured for all react-native side queries, but not for
cozy-app queries as they are served inside of WebViews and use a
different cozy-client instance

We want cozy-apps to benefits from the CozyPouchLink by redirecting
their queries to the react-native side using the new FlagshipLink
interface

With this interface, all cozy-apps queries can be redirected to the
react-native side using cozy-intent/post-me

In order to intercept them, then we should declare
`FlagshipLinkRequest()` method `localMethods`

Related PR: cozy/cozy-client#1505
When a cozy-app's WebView is served offline, then the cozy-app bundle
is served from local folder using the CozyProxyWebview, and since
previous commits, the cozy-client's queries are served through
`FlagshipLink`

With those mechanisms, nearly all data are available offline except two
things:
- cozy-stack static assets (i.e. some css files, avatar, partners logos
etc)
- `fetchJSON()` requests

This commit tries to handle the static assets part

Those assets are often served with HTTP cache activated, and so the
WebView should be able to load them correctly when the device is
offline. However on Android, the WebView's cache seems not to persist
after the application is closed

Activating the `cacheMode=LOAD_CACHE_ELSE_NETWORK` seems to fix this
behavior. But it prioritizes too much the cache over fresh data, so we
want to activate it only when strictly necessary, which is when the
application is offline

This also allows to load partners logos that are not cached by the
cozy-stack (as of today). But we expect to modify the cozy-stack to
enable cache on them
With previous changes, we now expect the CozyPouchLink to be the last
link of the chain, so forwarding the query would result to an exception
thrown

This mean we cannot forward the query when warmup queries are not
finished yet

So we want to allow CozyPouchLink to ignore the verification step and
process the query independently of the warmup queries status

To allow this we introduce the `ignoreWarmup` parameter. When set to
`true` the CozyPouchLink will process the query even if warmup is not
finished yet

Related PR: cozy/cozy-client#1506
Some cozy-apps declare a data `schema` into cozy-client instance

This schema is then used for processing queries

As we now process cozy-app queries on the react-native side through
FlagshipLinkRequest, we want to declared this schema in the Flagship
app's cozy-client

For now we only need to implement the one from cozy-home

The ideal implementation would be to extract it from the cozy-app's
bundle, but we did not implement anything to support this (we should
first investigate how to do this). So for now it is hardcoded
By adding offline support through PouchDB, we expect database related
bugs to happens in the future

In order to ease debugging them, we want to allow exploring the local
PouchDB files

The easier way is to add the ability to extract them from the device
and send them through email to cozy's support team
When the application is offline, we want the user to be able to access
their files that are accessible offline

To make this possible, we want the Flagship app to provide a new
`downloadFileAndPreview()` interface that can be called from cozy-apps

Internally this method should allow to download and preview files, but
also to store them in the device's storage in order to make them
accessible later even when the app is offline

This method will be called from cozy-client through `file` model

For now we make files accessible only if they have already downloaded
once

In the following commit we will make important files accessible in a
proactive way
We want the user's important files to always be accessible offline

To make this possible, we want the app to download them in background
on startup

We consider important files as files from `mespapiers` with specific
qualification labels like passport, identification papers, vehicle
registration, etc.
As we store offline accessible files in the device's storage, we want
to prevent them to fill the entire device's storage

We chose to keep only files that were accessed in the previous month.
All other files would be deleted

Important files are never deleted as long as they exist on the Cozy
instance
`NetStatusBoundary` is used to display an `offline` error screen when
the app is offline

Now that we implemented offline mode, we now want to disable the
`NetStatusBoundary` for cozy-apps as they should now be accessible when
offline

`NetStatusBoundary` is kept only on onboarding screens
In a previous commit we changed the return type for
`getIndexHtmlForSlug()`

We did not change the return objects for every execution paths

This commit fixes that
For now offline mode has only been implemented in cozy-home and
mespapiers apps

This commit prevents other cozy-apps to be opened offline

Later we will declare offline support in cozy-apps' manifests, so this
hard coded condition is meant to be replaced in the future
Cozy-apps can be opened offline only when they support this mode but
also when they have been opened at least one time to retrieve necessary
data to make them run offline

When those conditions are not met, we want to display an error message
to explain the user why the app cannot be opened

For now this message is in an Alert form, but later we may want to
improve the UI for this part
In iOS, we disabled HttpServer for all cozy-apps as the WebView API may
behave differently

The side effect is that we cannot open those app when offline as we
cannot inject minimal code to make them work without network access

So we want to enable HttpServer on those apps when we detect the app to
be offline

Related PR: #486
For now we don't want to replicate local changes into remote PouchDB as
we first want to ensure everything works as expected locally before
activating two-way replication in the future
@Ldoppea
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Ldoppea commented Sep 24, 2024

The commit has been cherry picked in #1209

@Ldoppea Ldoppea closed this Sep 24, 2024
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2 participants