Add Litematica exporter and integrate serde for serialization

- Introduced Litematica exporter with necessary data structures for Minecraft text generation.
- Added serde dependency for serialization support in multiple crates.
- Updated Cargo.toml files to include new dependencies and features.
- Created palette module for block palette management.

crates/exporters/src/lib.rs

@@ -1,3 +1,4 @@
+mod litematica;
 mod mcfunction;
 
 pub use mcfunction::McFunctionExporter;

crates/exporters/src/litematica.rs

@@ -0,0 +1,181 @@
+use std::{
+    collections::HashMap,
+    io::Write,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use anyhow::Context;
+use flate2::Compression;
+use flate2::write::GzEncoder;
+use lib::{StructureExporter, VoxelType};
+use serde::Serialize;
+
+#[derive(Serialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct Litematic {
+    pub metadata: Metadata,
+    pub minecraft_data_version: i32,
+    pub version: i32,
+    pub regions: std::collections::HashMap<String, Region>,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct Metadata {
+    pub author: String,
+    pub description: String,
+    pub enclosing_size: Vector3,
+    pub name: String,
+    pub region_count: i32,
+    pub time_created: i64,
+    pub time_modified: i64,
+    pub total_blocks: i32,
+    pub total_volume: i32,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct Region {
+    pub block_state_palette: Vec<BlockState>,
+    pub block_states: Vec<i64>,
+    pub position: Vector3,
+    pub size: Vector3,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct BlockState {
+    pub name: String,
+    // Optional properties like facing=north would go here,
+}
+
+#[derive(Serialize, Clone, Copy)]
+pub struct Vector3 {
+    pub x: i32,
+    pub y: i32,
+    pub z: i32,
+}
+
+pub struct LitematicaExporter {
+    palette_map: HashMap<VoxelType, String>,
+}
+
+impl LitematicaExporter {
+    pub fn new(body_block: &str, outline_block: &str) -> Self {
+        let mut palette_map = HashMap::new();
+        palette_map.insert(VoxelType::Body, body_block.to_string());
+        palette_map.insert(VoxelType::Outline, outline_block.to_string());
+        Self { palette_map }
+    }
+
+    fn pack_bits(indicies: &[usize], bits_per_entry: usize) -> Vec<i64> {
+        let entries_per_long = 64 / bits_per_entry;
+        let mut packed = Vec::new();
+        let mut current_long: i64 = 0;
+        let mut current_idx = 0;
+
+        for &index in indicies {
+            current_long |= (index as i64) << (current_idx * bits_per_entry);
+            current_idx += 1;
+
+            if current_idx >= entries_per_long {
+                packed.push(current_long as i64);
+                current_long = 0;
+                current_idx = 0;
+            }
+        }
+
+        if current_idx > 0 {
+            packed.push(current_long as i64);
+        }
+
+        packed
+    }
+}
+
+impl StructureExporter for LitematicaExporter {
+    fn export(&self, grid: &lib::VoxelGrid) -> anyhow::Result<Vec<u8>> {
+        let mut palette_list = vec![BlockState {
+            name: "minecraft:air".to_string(),
+        }];
+        let mut type_to_index = HashMap::new();
+
+        for (voxel_type, block_id) in &self.palette_map {
+            type_to_index.insert(*voxel_type, palette_list.len());
+            palette_list.push(BlockState {
+                name: block_id.clone(),
+            });
+        }
+
+        let bits_per_entry =
+            std::cmp::max(2, (palette_list.len() as f64 - 1.0).log2().ceil() as usize);
+
+        let mut indices = Vec::with_capacity((grid.width * grid.height * grid.depth) as usize);
+        let mut total_blocks = 0;
+
+        for y in 0..grid.height {
+            for z in 0..grid.depth {
+                for x in 0..grid.width {
+                    if let Some(voxel) = grid.get(x, y, z) {
+                        indices.push(*type_to_index.get(&voxel).unwrap());
+                        total_blocks += 1;
+                    } else {
+                        indices.push(0); // Index 0 is Air
+                    }
+                }
+            }
+        }
+
+        let packed_states = Self::pack_bits(&indices, bits_per_entry);
+
+        let timestamp = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap()
+            .as_millis() as i64;
+        let dimensions = Vector3 {
+            x: grid.width as i32,
+            y: grid.height as i32,
+            z: grid.depth as i32,
+        };
+
+        let mut regions = HashMap::new();
+        regions.insert(
+            "TextRegion".to_string(),
+            Region {
+                block_state_palette: palette_list,
+                block_states: packed_states,
+                position: Vector3 { x: 0, y: 0, z: 0 },
+                size: dimensions,
+            },
+        );
+
+        let litematic = Litematic {
+            minecraft_data_version: 3465, // 1.20+ Data Version
+            version: 6,                   // Litematica format version
+            metadata: Metadata {
+                author: "Minecraft Text Builder".to_string(),
+                description: "Generated 3D Text".to_string(),
+                name: "Text_Structure".to_string(),
+                enclosing_size: dimensions,
+                region_count: 1,
+                total_blocks,
+                total_volume: (grid.width * grid.height * grid.depth) as i32,
+                time_created: timestamp,
+                time_modified: timestamp,
+            },
+            regions,
+        };
+
+        let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
+
+        let nbt_bytes = fastnbt::to_bytes(&litematic).context("NBT serialization failed")?;
+
+        encoder.write_all(&nbt_bytes)?;
+
+        Ok(encoder.finish()?)
+    }
+
+    fn file_extension(&self) -> &'static str {
+        "litematic"
+    }
+}