From dd36013f5e31f3d24276e6e3c4c2f5859d8e00ec Mon Sep 17 00:00:00 2001
From: "neelesh.poli2006@gmail.com"
 <72574589+neeleshpoli@users.noreply.github.com>
Date: Fri, 20 Dec 2024 19:10:59 -0600
Subject: [PATCH] Implement level.dat reading and use the seed in the world for
 chunk generation

---
 pumpkin-world/src/chunk/anvil.rs | 55 ++++++++++++++++++++++++++++++--
 pumpkin-world/src/chunk/mod.rs   |  6 ++++
 pumpkin-world/src/level.rs       | 21 ++++++++----
 3 files changed, 74 insertions(+), 8 deletions(-)

diff --git a/pumpkin-world/src/chunk/anvil.rs b/pumpkin-world/src/chunk/anvil.rs
index 86389be6..af24f70b 100644
--- a/pumpkin-world/src/chunk/anvil.rs
+++ b/pumpkin-world/src/chunk/anvil.rs
@@ -4,10 +4,11 @@ use std::{
 };
 
 use flate2::bufread::{GzDecoder, ZlibDecoder};
+use serde::Deserialize;
 
-use crate::level::SaveFile;
+use crate::{chunk::ChunkParsingError, level::SaveFile};
 
-use super::{ChunkData, ChunkReader, ChunkReadingError, CompressionError};
+use super::{ChunkData, ChunkReader, ChunkReadingError, CompressionError, WorldInfo};
 
 #[derive(Clone)]
 pub struct AnvilChunkReader {}
@@ -158,6 +159,56 @@ impl ChunkReader for AnvilChunkReader {
 
         ChunkData::from_bytes(&decompressed_chunk, *at).map_err(ChunkReadingError::ParsingError)
     }
+
+    fn read_world_info(&self, save_file: &SaveFile) -> Result<WorldInfo, ChunkReadingError> {
+        let path = save_file.root_folder.join("level.dat");
+
+        let mut world_info_file = OpenOptions::new()
+            .read(true)
+            .open(path)
+            .map_err(|e| ChunkReadingError::IoError(e.kind()))?;
+
+        let mut buffer = Vec::new();
+        world_info_file
+            .read_to_end(&mut buffer)
+            .map_err(|e| ChunkReadingError::IoError(e.kind()))?;
+
+        let decompressed_data = Compression::GZip
+            .decompress_data(buffer)
+            .map_err(ChunkReadingError::Compression)?;
+        let info = fastnbt::from_bytes::<LevelDat>(&decompressed_data).map_err(|e| {
+            ChunkReadingError::ParsingError(ChunkParsingError::ErrorDeserializingChunk(
+                e.to_string(),
+            ))
+        })?;
+
+        Ok(WorldInfo {
+            seed: info.data.world_gen_settings.seed,
+        })
+    }
+}
+
+#[derive(Deserialize)]
+pub struct LevelDat {
+    // No idea why its formatted like this
+    #[serde(rename = "Data")]
+    pub data: WorldData,
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct WorldData {
+    pub world_gen_settings: WorldGenSettings,
+    // TODO: Implement the rest of the fields
+    // Fields below this comment are being deserialized, but are not being used
+    pub spawn_x: i32,
+    pub spawn_y: i32,
+    pub spawn_z: i32,
+}
+
+#[derive(Deserialize)]
+pub struct WorldGenSettings {
+    pub seed: i64,
 }
 
 #[cfg(test)]
diff --git a/pumpkin-world/src/chunk/mod.rs b/pumpkin-world/src/chunk/mod.rs
index fcbb53f1..5e69e8f6 100644
--- a/pumpkin-world/src/chunk/mod.rs
+++ b/pumpkin-world/src/chunk/mod.rs
@@ -25,6 +25,7 @@ pub trait ChunkReader: Sync + Send {
         save_file: &SaveFile,
         at: &Vector2<i32>,
     ) -> Result<ChunkData, ChunkReadingError>;
+    fn read_world_info(&self, save_file: &SaveFile) -> Result<WorldInfo, ChunkReadingError>;
 }
 
 #[derive(Error, Debug)]
@@ -326,3 +327,8 @@ pub enum ChunkParsingError {
     #[error("Error deserializing chunk: {0}")]
     ErrorDeserializingChunk(String),
 }
+
+pub struct WorldInfo {
+    pub seed: i64,
+    // TODO: Implement all fields
+}
diff --git a/pumpkin-world/src/level.rs b/pumpkin-world/src/level.rs
index 2a6a9571..eb107b55 100644
--- a/pumpkin-world/src/level.rs
+++ b/pumpkin-world/src/level.rs
@@ -13,6 +13,7 @@ use tokio::{
 use crate::{
     chunk::{
         anvil::AnvilChunkReader, ChunkData, ChunkParsingError, ChunkReader, ChunkReadingError,
+        WorldInfo,
     },
     world_gen::{get_world_gen, Seed, WorldGenerator},
 };
@@ -28,6 +29,7 @@ use crate::{
 /// For more details on world generation, refer to the `WorldGenerator` module.
 pub struct Level {
     pub seed: Seed,
+    pub world_info: Option<WorldInfo>,
     save_file: Option<SaveFile>,
     loaded_chunks: Arc<DashMap<Vector2<i32>, Arc<RwLock<ChunkData>>>>,
     chunk_watchers: Arc<DashMap<Vector2<i32>, usize>>,
@@ -55,20 +57,26 @@ impl Level {
                 region_folder.exists(),
                 "World region folder does not exist, despite there being a root folder."
             );
-            // TODO: read seed from level.dat
-            let seed = get_or_create_seed();
+            let save_file = SaveFile {
+                root_folder,
+                region_folder,
+            };
+
+            let reader = AnvilChunkReader::new();
+            let info = reader
+                .read_world_info(&save_file)
+                .expect("Unable to get world info!");
+            let seed = Seed(info.seed as u64);
             let world_gen = get_world_gen(seed).into(); // TODO Read Seed from config.
 
             Self {
                 seed,
                 world_gen,
-                save_file: Some(SaveFile {
-                    root_folder,
-                    region_folder,
-                }),
+                save_file: Some(save_file),
                 chunk_reader: Arc::new(AnvilChunkReader::new()),
                 loaded_chunks: Arc::new(DashMap::new()),
                 chunk_watchers: Arc::new(DashMap::new()),
+                world_info: Some(info),
             }
         } else {
             let seed = get_or_create_seed();
@@ -80,6 +88,7 @@ impl Level {
                 chunk_reader: Arc::new(AnvilChunkReader::new()),
                 loaded_chunks: Arc::new(DashMap::new()),
                 chunk_watchers: Arc::new(DashMap::new()),
+                world_info: None,
             }
         }
     }