# Migration from legacy packs

This project is meant to replace legacy `.pck` or EterPack-style content
delivery gradually, not through a single risky cutover.

## Target state

- Linux builds produce `.m2p`
- the client loads `.m2p` first
- runtime master key delivery is required
- silent fallback to legacy packs is disabled in production

## Suggested migration phases

### Phase 1: parallel loader

- keep the legacy loader in the client
- add `.m2p` support beside it
- verify the new loader against real content sets
- keep fallback only in development if needed

### Phase 2: pipeline validation

- build `.m2p` from the same source tree as legacy packs
- run `verify` for every archive
- run `diff` between the source tree and `.m2p`
- compare in-game behavior between legacy and `.m2p`

### Phase 3: runtime delivery

- stop embedding a real content key in the client
- deliver the runtime key through launcher, environment, or mapping
- verify startup failure behavior when the runtime key is missing

### Phase 4: production cutover

- package only `.m2p` for release clients
- disable silent fallback to legacy packs
- remove stale pack generation from release CI
- keep extract/debug tools only for internal use

## Recommended checks

- duplicate normalized paths
- invalid relative paths
- case-collision problems on Windows
- decompression failures
- manifest signature failures
- key mismatch by `key_id`

## Practical migration loop

1. Pick one legacy pack group.
2. Rebuild it as `.m2p`.
3. Verify it.
4. Diff it against the source tree.
5. Boot the client with runtime keys.
6. Validate asset loads in logs and in-game.
7. Move to the next pack group.

## Confirmed startup-safe pack group

The following startup pack set has already been validated against the real
client runtime on the Linux VPS:

- `root`
- `patch1`
- `patch2`
- `season3_eu`
- `metin2_patch_snow`
- `metin2_patch_snow_dungeon`
- `metin2_patch_etc_costume1`
- `metin2_patch_pet1`
- `metin2_patch_pet2`
- `metin2_patch_ramadan_costume`
- `metin2_patch_flame`
- `metin2_patch_flame_dungeon`
- `locale`
- `uiscript`
- `uiloading`
- `ETC`
- `item`
- `effect`
- `icon`
- `property`

Validation method:

1. build each pack as `.m2p`
2. remove the matching legacy `.pck`
3. provide the runtime master key through:
   - `M2PACK_MASTER_KEY_HEX`
   - `M2PACK_KEY_ID=1`
4. start the Linux-built Windows client with `xvfb-run + wine`

Observed result:

- `PackInitialize` succeeded
- Python startup succeeded
- `app.Create(...)` succeeded
- client reached `MainStream.SetLoginPhase()`

Recommended next pack groups:

1. remaining startup-adjacent patch packs
2. world and map content such as outdoor, terrain, tree, and zone
3. late-load gameplay content such as pc, npc, monster, and sound

## Risk notes

- Do not mix silent fallback with production security claims.
- Do not ship a client that accepts `.m2p` without runtime key enforcement.
- Do not keep real secret keys inside the repository.