105 lines
5.3 KiB
Markdown
105 lines
5.3 KiB
Markdown
# RegionIO
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A Minecraft Java Edition server core written in Go, targeting version
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**26.1.2** (protocol **775**). RegionIO implements the connection lifecycle
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(status → login → configuration → play), multiplayer chunk streaming, shared
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block editing, persistent worlds, and an overworld generator built on the real
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`noise_router` `final_density` tree.
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## Status
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- **Network**: full handshake/status/login (offline mode)/configuration/play
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state machine with zlib compression, keep-alive, and chunk streaming.
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- **Registries**: 28 synchronized registries + tags, captured verbatim from the
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26.1.2 vanilla server and sent during configuration.
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- **World**: revisioned, concurrency-safe chunk snapshots; memoized
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`level_chunk_with_light` frames; ticket-aware bounded LRU cache; shared frame
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admission limit; Anvil `.mca` persistence with autosave and seed metadata.
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- **Generation**: vanilla-derived overworld terrain from the embedded datapack
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(`ImprovedNoise`/`PerlinNoise`/`BlendedNoise`/`NormalNoise` + the density
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function interpreter), 3D multi-noise biomes, surface-rule interpretation,
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deterministic decoration, and basic template structures.
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- **Gameplay**: four-player session registry; player join/leave and movement
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synchronization; chunk-scoped visibility for players and mobs; shared
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creative block place/break; broadcast chat; and hotbar item→block mapping.
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- **Lighting**: stored vanilla nibble arrays for sky and block light; horizontal
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and cross-chunk propagation; incremental updates after edits; persisted
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`SkyLight`/`BlockLight`; load-time border reconciliation; and chunk-scoped
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`light_update` broadcasts.
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- **Chunk lifecycle**: per-client view and prefetch tickets, strict near-first
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ring streaming, stale-recenter cutoff, explicit client unload packets, and
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eviction only after the final owner releases a chunk.
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- **Safety**: duplicate chunk generation is coalesced; corrupt stored chunks are
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not silently regenerated or overwritten; a world cannot reopen with another
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seed.
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## Build & run
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```
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go build ./...
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go run ./cmd/regionio -seed 12345 -port 25565 -viewdistance 2
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```
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The world seed defaults to `0`; override it with the `-seed` flag or the
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`REGIONIO_SEED` environment variable. The server listens on `0.0.0.0:25565`.
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Changing the seed for an existing world directory is rejected. The server caps
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the client-requested chunk radius at `2` by default because cold density-based
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generation is expensive; raise it with `-viewdistance 3` after the surrounding
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world has been generated and cached.
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## Testing
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```
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go test ./...
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go test -race ./internal/network ./internal/server ./internal/world \
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-run 'Test(Integration|BoundaryEdit|PlayerInfo|PlayerRegistry|Concurrent|Incremental|EncodeLight|Cache|Store|Eviction|Region|Ticket|Streamer|LoadSixteen)'
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# or run both gates:
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make verify
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```
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The integration suite exercises four clients across two visibility regions:
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join, movement, leaving, mob visibility, and local block/light updates. A
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two-client scenario separately covers shared block edits and chat. Concurrency
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tests cover simultaneous frame encoding, editing, autosave, cache misses, and
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session movement/broadcasts. A 16-client lifecycle test exercises overlapping
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ticket ownership, bounded global frame work, packet output, and cleanup after
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disconnect. Lighting tests compare the initial flat chunk and a 31x31x31
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glowstone propagation volume against fixtures captured from the official
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vanilla 26.1.2 server. Optional terrain parity diagnostics compare surface
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heights against `/tmp/vanilla_ground.json` when that capture is present.
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## v0.4 scope
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RegionIO v0.4 is a small creative multiplayer server core, not a complete
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vanilla gameplay implementation. Player and mob visibility is chunk-scoped,
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but there is no interest prioritization or delta-movement compression yet.
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Lighting matches vanilla's block-state dampening, emission, and face-occlusion
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properties and reconciles persisted borders when chunks re-enter the live
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cache. Streaming prioritizes Chebyshev rings and abandons unstarted stale work;
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an already admitted frame calculation completes atomically rather than being
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interrupted halfway. Unowned clean chunks remain as an LRU warm cache until
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capacity pressure evicts them. Structures, placed features, mob AI,
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authentication, inventory, and survival mechanics remain intentionally partial.
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The density router is vanilla-derived, while biome/surface/decoration layers
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still contain approximations and require stricter parity fixtures.
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## Project layout
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```
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cmd/regionio/ entry point (config, listener, graceful shutdown)
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internal/
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protocol/ wire primitives: VarInt, framing, compression, packet IDs
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nbt/ NBT encoder/decoder (with modified UTF-8)
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registry/ embedded synchronized registries + tags
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world/ chunk model, level_chunk encoder, cache, generators, biomes
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worldgen/ noise core + density-function interpreter + climate finder
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network/ per-connection state machine (handler/conn/play/login/...)
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server/ shared core: config, status response, profiles
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```
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## Notes
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The vanilla `server.jar` and its unpacked `libraries/`/`versions/` are **not**
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included (obtain them from Mojang). The embedded data under `internal/`
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(registries, biome parameters, the overworld datapack) is derived from vanilla
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reports and is all that is required to build and run.
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