# Moonwell Launcher Web API Spec

## Scope

This document specifies the current launcher behavior for:

- authentication against the Moonwell Web API
- installation directory selection
- local file scan and hash calculation
- manifest-based synchronization
- launch and game authorization for the Rust MoonWell 1.12.1 client

The launcher no longer uses S3/MinIO directly. All server interaction goes
through the Web API.

## Configuration

The launcher API base URL is provided via:

- `MOONWELL_API_BASE_URL`
- optional `MOONWELL_AUTH_ADDRESS` for the game auth endpoint (`host[:port]`)

Current integration mode is compile-time:

- `flutter run -d windows --dart-define=MOONWELL_API_BASE_URL=https://host`
- `flutter build windows --dart-define=MOONWELL_API_BASE_URL=https://host`

## API Flow

The launcher uses these endpoints from `openapi.json`:

1. `POST /api/launcher/login`
2. `POST /api/launcher/register`
3. `GET /api/launcher/manifest`
4. `GET /api/launcher/download/{path}`
5. `GET /api/launcher/news`
6. `GET /api/launcher/realms`
7. `GET /api/launcher/account`
8. `POST /api/launcher/game-ticket`

Registration sequence:

1. User opens the registration tab and provides `username`, `email`,
   `password`, `password_confirmation`, optional `invite_code`, and accepts
   `terms`.
2. Launcher sends the payload to `POST /api/launcher/register`.
3. After a successful `201` response, the form returns to the login tab and
   displays the API success message.
4. Validation and invite errors returned by the API are shown in the form.

Authentication sequence:

1. User enters launcher credentials.
2. Launcher requests a bearer token from `POST /api/launcher/login`.
3. Launcher requests the manifest from `GET /api/launcher/manifest`.
4. Successful login persists `LauncherSession` locally.
5. On next launcher start, saved session is reused to fetch manifest again.
6. `LauncherSession` and `ClientManifest` are passed into the home screen.
7. If an installation directory is saved, synchronization starts
   automatically with the fetched manifest.
8. While the launcher is open, it refreshes the manifest every five minutes.
9. A server build hash that differs from the verified local build hash starts
   synchronization automatically.

Logout sequence:

1. User presses `Logout`.
2. Launcher cancels any active sync.
3. Launcher clears the locally persisted `LauncherSession`.
4. Launcher returns to the login screen.

File download sequence:

1. Launcher resolves files that are missing, stale, or changed.
2. For each required file, launcher calls `GET /api/launcher/download/{path}` with bearer auth.
3. API returns JSON with a temporary presigned `url` and `expires_in`.
4. Launcher downloads the file directly from storage using the presigned URL.
5. Download is written into `*.moonwell.part`.
6. Downloaded file is verified against manifest `sha256`.
7. Temporary file replaces the destination file only after successful verify.

News sequence:

1. After the launcher reaches the authenticated home screen, it requests `GET /api/launcher/news`.
2. The response payload is read from the top-level `data` array.
3. Each news item provides `id`, `title`, `body`, optional `image_url`, and `created_at`.
4. News failures do not block patching or play flow; the launcher shows a local error state only inside the news panel.
5. Pressing a news item opens `<MOONWELL_API_BASE_URL>/news/{id}` in the
   system browser.

Realm status sequence:

1. After the authenticated home screen opens, the launcher requests
   `GET /api/launcher/realms`.
2. The first item in the top-level `data` array supplies the realm name,
   online state, and game build shown in the sync panel.
3. Realm information is refreshed every minute while the launcher remains
   open.
4. A failed refresh keeps the last known realm state and is retried on the next
   interval.

Account sequence:

1. After the authenticated home screen opens, the launcher requests
   `GET /api/launcher/account` with bearer authentication.
2. Only `username` is stored in launcher UI state and displayed in the account
   menu.
3. The response `balance` field is intentionally ignored and never displayed.
4. Account metadata failures do not block patching or launching the game.

Game authorization sequence:

1. Immediately before starting the game, the launcher calls
   `POST /api/launcher/game-ticket` with bearer authentication and
   `{ "client_build": 5875 }` in the JSON body.
2. The API returns `account`, a 16-character `A-Z0-9` single-use `ticket`, and
   `expires_at`. The account is 3–16 uppercase `A-Z0-9` characters. The ticket
   must remain valid for at least five more seconds, including at process start.
3. Issuing a ticket atomically revokes any previous unused game ticket for the
   same account. Production lifetime must not exceed 60 seconds.
4. The launcher never persists or logs the ticket.
5. The auth server uses the ticket as the temporary SRP password and consumes
   it atomically after a successful logon proof.

## Installation Directory Rules

The user selects a single installation root directory.

All paths in the manifest are treated as relative to that root.

Path safety rules:

- backslashes are normalized to `/`
- leading `./` is removed
- absolute paths are rejected
- path traversal via `..` is rejected

## Ignored Directories

Unmanaged files in these directories outside `Data/` and `WoW/Data/` are
preserved and excluded from verification:

- `Cache`
- `Errors`
- `Logs`
- `Screenshots`
- `WTF`
- `benilla-config`
- `.moonwell_launcher`
- `Interface/AddOns`

Files under these directories:

- are not included in local scan
- do not participate in local `buildHash`
- are not compared against server manifest

Inside `Data/` and `WoW/Data/`, the manifest is authoritative for every file,
including nested files whose names contain `wtf`, `cache`, or `addons`.
The exclusions above do not exempt files inside Data from cleanup.

## Local Scan

For every existing manifest file in the installation directory, the launcher computes:

- normalized relative path
- file size in bytes
- file `sha256`

The result is stored as a `ClientInstallationSnapshot`. Paths are always relative
to the selected installation root, including files in nested directories.

The scan separately collects stale paths without hashing their contents:

- every file absent from the manifest in `Data/` and `WoW/Data/`
- every file absent from the manifest in obsolete `Extentions/` and
  `WoW/Extentions/` directories, including unused subdirectories and the
  Extentions directory itself when no manifest files require it
- `WoW.exe` and `*.dll` absent from the manifest directly in the installation
  root or `WoW/` (binary names are matched without case sensitivity)
- unused Data subdirectories, ordered after their children; the Data roots and
  directories needed by manifest files are retained

These paths do not contribute to `buildHash`, but prevent sync from completing
until cleanup and final verification succeed. Other unmanaged files are preserved.
On Windows, manifest membership checks for cleanup ignore path letter case.
Directory links are not traversed during cleanup. Links absent from the manifest
inside Data are removed as links, and deletion through a parent pointing outside
the installation is rejected. Directory deletion is never recursive.

## Hash Cache

To accelerate repeated scans, the launcher stores a local hash cache in:

- `<install-root>/.moonwell_launcher/hash_cache.json`

This metadata directory is excluded from verification.

Each cache entry is keyed by normalized relative path and stores:

- `size`
- `modifiedMs`
- `sha256`

Cache reuse rule:

- if `path`, `size`, and `modifiedMs` still match, the cached `sha256` is reused
- otherwise `sha256` is recomputed and the cache entry is replaced

The cache is an optimization only. The server remains the source of truth via
the manifest comparison.

## Diagnostics

During sync, the launcher writes a log file to:

- `<install-root>/.moonwell_launcher/launcher.log`

If an installation directory is not available yet, the launcher falls back to a
temporary system log directory.

For failed downloads:

- HTTP and storage download failures are logged with file path and status code
- checksum mismatches log expected and actual `size` and `sha256`
- invalid payloads are preserved as `*.moonwell.part.failed` for inspection

## buildHash Algorithm

`buildHash` is deterministic and calculated identically for local snapshot and
remote manifest.

For each file entry, the launcher builds a canonical string:

`<normalized-path>:<size>:<sha256-lowercase>`

Then:

1. sort all canonical strings lexicographically
2. join them with `\n`
3. compute `sha256` of the resulting UTF-8 payload

This means file ordering in the manifest does not affect `buildHash`.

## Sync Algorithm

The current sync flow is:

1. Load manifest.
2. Scan local installation.
3. Compute local `buildHash`.
4. Compare local files to manifest files by `path`, `size`, and `sha256`.
5. Identify stale paths in the cleanup areas described above.
6. If local `buildHash` matches server `buildHash` and there are no stale files
   and no mismatches, finish successfully.
7. Delete stale paths, including unused Data subdirectories after their children.
8. Download changed and missing files.
9. Verify every downloaded file by `sha256`.
10. Re-scan the installation.
11. Recompute local `buildHash`.
12. Fail if final snapshot still differs from manifest or stale paths remain.

## Pause and Resume Semantics

Pause is implemented as cooperative cancellation:

- the current sync stream is cancelled
- the next sync starts a fresh comparison from current disk state
- already replaced files remain valid
- partial `*.moonwell.part` files are removed before the next download attempt

## Launch Behavior

When the user presses `Play`:

1. launcher requests a single-use game ticket for build 5875
2. launcher resolves `<install-root>/MoonWell.exe` on Windows,
   `<install-root>/MoonWell.app/Contents/MacOS/launch` on macOS, or
   `<install-root>/MoonWell` on Linux
3. launcher reads the auth address from `MOONWELL_AUTH_ADDRESS` when configured,
   otherwise from `set realmlist <host[:port]>` in `realmlist.wtf`; this file is
   never modified and the default auth port is 3724
4. launcher resolves the player's data in `Data/`, falling back to `WoW/Data/`,
   and verifies that the ticket still has at least five seconds of validity
5. launcher starts MoonWell with working directory set to the installation root,
   no authorization command-line arguments, and these child environment values:
   - `WOW_USER=<account>`
   - `WOW_PASS=<ticket>`
   - `WOW_HOST=<auth-address>`
   - `WOW_DATA=<absolute-data-directory>`
   - `BENILLA_HOME=<install-root>/benilla-config`
   - `WOW_LOCALE=auto` (select the installed `Data/ruRU` or `WoW/Data/ruRU` language pack,
     otherwise English; override any locale inherited from the launcher's parent)
6. launcher retains a process handle; while the process is alive, it disables repeated game launches
   and client synchronization
7. when the process exits, the launcher returns to the ready-to-play state

Launching never edits `WTF/Config.wtf` or clears `Cache`. macOS executes the
bundle launcher directly; that script `exec`s MoonWell so the handle follows
the game rather than an `open` helper. Settings remain outside the `.app`.
If the executable, data directory, or auth endpoint is missing or invalid,
launch fails with an error. A consumed ticket cannot authenticate again; close
the client and press Play for a fresh ticket after a session ends.

Language archives are ordinary client-manifest entries, including their nested paths,
sizes and SHA-256 hashes. Synchronization verifies and retains required `ruRU` files
and removes obsolete archives under the same manifest-authoritative Data policy.

## Error Behavior

The launcher surfaces errors for:

- invalid API configuration
- authentication failure
- registration validation or server failure
- manifest load failure
- path traversal attempts
- checksum mismatch after download
- missing downloaded temp files before verification
- final verification mismatch after update
- missing MoonWell executable, WoW data, or game auth endpoint
- invalid, expired, or unavailable game ticket

## Tested Invariants

The automated tests cover:

- deterministic `buildHash`
- path normalization used by `buildHash`
- preservation of user state and unrelated unmanaged files during cleanup
- removal of unmanaged Data files, unused subdirectories, WoW.exe, DLLs, and
  obsolete Extentions directories
- preservation of manifest-listed DLLs and WoW.exe
- cache cleanup behavior
- safe path resolution
- sync flow with fully up-to-date client
- sync flow with stale files and changed files
- cleanup when all manifest files are already up to date
- rejection of stale paths remaining after final verification