Restructure crates

Get rid of the arbitrary bin/lib split and instead move as much as
possible into the bin crate, which becomes the main crate again.

The types and NBT handling are moved into separate crates, so they can
be reused by nbtdump and regiondump.

src/core/metadata_writer.rs

@@ -0,0 +1,129 @@
+//! The [MetadataWriter] and related types
+
+use anyhow::{Context, Result};
+use serde::Serialize;
+
+use crate::{core::common::*, io::fs, world::de};
+
+/// Minimum and maximum X and Z tile coordinates for a mipmap level
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "camelCase")]
+struct Bounds {
+	/// Minimum X coordinate
+	min_x: i32,
+	/// Maximum X coordinate
+	max_x: i32,
+	/// Minimum Z coordinate
+	min_z: i32,
+	/// Maximum Z coordinate
+	max_z: i32,
+}
+
+/// Mipmap level information in viewer metadata file
+#[derive(Debug, Serialize)]
+struct Mipmap<'t> {
+	/// Minimum and maximum tile coordinates of the mipmap level
+	bounds: Bounds,
+	/// Map of populated tiles for the mipmap level
+	regions: &'t TileCoordMap,
+}
+
+/// Initial spawn point for new players
+#[derive(Debug, Serialize)]
+struct Spawn {
+	/// Spawn X coordinate
+	x: i32,
+	/// Spawn Z coordinate
+	z: i32,
+}
+
+/// Viewer metadata JSON data structure
+#[derive(Debug, Serialize)]
+struct Metadata<'t> {
+	/// Tile information for each mipmap level
+	mipmaps: Vec<Mipmap<'t>>,
+	/// Initial spawn point for new players
+	spawn: Spawn,
+}
+
+/// The MetadataWriter is used to generate the viewer metadata file
+pub struct MetadataWriter<'a> {
+	/// Common MinedMap configuration from command line
+	config: &'a Config,
+	/// Map of generated tiles for each mipmap level
+	tiles: &'a [TileCoordMap],
+}
+
+impl<'a> MetadataWriter<'a> {
+	/// Creates a new MetadataWriter
+	pub fn new(config: &'a Config, tiles: &'a [TileCoordMap]) -> Self {
+		MetadataWriter { config, tiles }
+	}
+
+	/// Helper to construct a [Mipmap] data structure from a [TileCoordMap]
+	fn mipmap_entry(regions: &TileCoordMap) -> Mipmap {
+		let mut min_x = i32::MAX;
+		let mut max_x = i32::MIN;
+		let mut min_z = i32::MAX;
+		let mut max_z = i32::MIN;
+
+		for (&z, xs) in &regions.0 {
+			if z < min_z {
+				min_z = z;
+			}
+			if z > max_z {
+				max_z = z;
+			}
+
+			for &x in xs {
+				if x < min_x {
+					min_x = x;
+				}
+				if x > max_x {
+					max_x = x;
+				}
+			}
+		}
+
+		Mipmap {
+			bounds: Bounds {
+				min_x,
+				max_x,
+				min_z,
+				max_z,
+			},
+			regions,
+		}
+	}
+
+	/// Reads and deserializes the `level.dat` of the Minecraft save data
+	fn read_level_dat(&self) -> Result<de::LevelDat> {
+		crate::nbt::data::from_file(&self.config.level_dat_path).context("Failed to read level.dat")
+	}
+
+	/// Generates [Spawn] data from a [de::LevelDat]
+	fn spawn(level_dat: &de::LevelDat) -> Spawn {
+		Spawn {
+			x: level_dat.data.spawn_x,
+			z: level_dat.data.spawn_z,
+		}
+	}
+
+	/// Runs the viewer metadata file generation
+	pub fn run(self) -> Result<()> {
+		let level_dat = self.read_level_dat()?;
+
+		let mut metadata = Metadata {
+			mipmaps: Vec::new(),
+			spawn: Self::spawn(&level_dat),
+		};
+
+		for tile_map in self.tiles.iter() {
+			metadata.mipmaps.push(Self::mipmap_entry(tile_map));
+		}
+
+		fs::create_with_tmpfile(&self.config.metadata_path, |file| {
+			serde_json::to_writer(file, &metadata).context("Failed to write metadata")
+		})
+	}
+}