feat: add Fabric and Forge loader support modules with version fetching and installation functionality

2 files changed, 602 insertions, 0 deletions

diff --git a/src-tauri/src/core/fabric.rs b/src-tauri/src/core/fabric.rs
new file mode 100644
index 0000000..8fc960f
--- /dev/null
+++ b/src-tauri/src/core/fabric.rs
@@ -0,0 +1,269 @@
+//! Fabric Loader support module.
+//!
+//! This module provides functionality to:
+//! - Fetch available Fabric loader versions from the Fabric Meta API
+//! - Generate version JSON files for Fabric-enabled Minecraft versions
+//! - Install Fabric loader for a specific Minecraft version
+
+use serde::{Deserialize, Serialize};
+use std::error::Error;
+use std::path::PathBuf;
+
+const FABRIC_META_URL: &str = "https://meta.fabricmc.net/v2";
+
+/// Represents a Fabric loader version from the Meta API.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricLoaderVersion {
+    pub separator: String,
+    pub build: i32,
+    pub maven: String,
+    pub version: String,
+    pub stable: bool,
+}
+
+/// Represents a Fabric intermediary mapping version.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricIntermediaryVersion {
+    pub maven: String,
+    pub version: String,
+    pub stable: bool,
+}
+
+/// Represents a combined loader + intermediary version entry.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricLoaderEntry {
+    pub loader: FabricLoaderVersion,
+    pub intermediary: FabricIntermediaryVersion,
+    #[serde(rename = "launcherMeta")]
+    pub launcher_meta: FabricLauncherMeta,
+}
+
+/// Launcher metadata from Fabric Meta API.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricLauncherMeta {
+    pub version: i32,
+    pub libraries: FabricLibraries,
+    #[serde(rename = "mainClass")]
+    pub main_class: FabricMainClass,
+}
+
+/// Libraries required by Fabric loader.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricLibraries {
+    pub client: Vec<FabricLibrary>,
+    pub common: Vec<FabricLibrary>,
+    pub server: Vec<FabricLibrary>,
+}
+
+/// A single Fabric library dependency.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricLibrary {
+    pub name: String,
+    pub url: Option<String>,
+}
+
+/// Main class configuration for Fabric.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricMainClass {
+    pub client: String,
+    pub server: String,
+}
+
+/// Represents a Minecraft version supported by Fabric.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct FabricGameVersion {
+    pub version: String,
+    pub stable: bool,
+}
+
+/// Information about an installed Fabric version.
+#[derive(Debug, Serialize, Clone)]
+pub struct InstalledFabricVersion {
+    pub id: String,
+    pub minecraft_version: String,
+    pub loader_version: String,
+    pub path: PathBuf,
+}
+
+/// Fetch all Minecraft versions supported by Fabric.
+///
+/// # Returns
+/// A list of game versions that have Fabric intermediary mappings available.
+pub async fn fetch_supported_game_versions() -> Result<Vec<FabricGameVersion>, Box<dyn Error + Send + Sync>> {
+    let url = format!("{}/versions/game", FABRIC_META_URL);
+    let resp = reqwest::get(&url)
+        .await?
+        .json::<Vec<FabricGameVersion>>()
+        .await?;
+    Ok(resp)
+}
+
+/// Fetch all available Fabric loader versions.
+///
+/// # Returns
+/// A list of all Fabric loader versions, ordered by build number (newest first).
+pub async fn fetch_loader_versions() -> Result<Vec<FabricLoaderVersion>, Box<dyn Error + Send + Sync>> {
+    let url = format!("{}/versions/loader", FABRIC_META_URL);
+    let resp = reqwest::get(&url)
+        .await?
+        .json::<Vec<FabricLoaderVersion>>()
+        .await?;
+    Ok(resp)
+}
+
+/// Fetch Fabric loader versions available for a specific Minecraft version.
+///
+/// # Arguments
+/// * `game_version` - The Minecraft version (e.g., "1.20.4")
+///
+/// # Returns
+/// A list of loader entries with full metadata for the specified game version.
+pub async fn fetch_loaders_for_game_version(
+    game_version: &str,
+) -> Result<Vec<FabricLoaderEntry>, Box<dyn Error + Send + Sync>> {
+    let url = format!("{}/versions/loader/{}", FABRIC_META_URL, game_version);
+    let resp = reqwest::get(&url)
+        .await?
+        .json::<Vec<FabricLoaderEntry>>()
+        .await?;
+    Ok(resp)
+}
+
+/// Fetch the version JSON profile for a specific Fabric loader + game version combination.
+///
+/// # Arguments
+/// * `game_version` - The Minecraft version (e.g., "1.20.4")
+/// * `loader_version` - The Fabric loader version (e.g., "0.15.6")
+///
+/// # Returns
+/// The raw version JSON as a `serde_json::Value` that can be saved to the versions directory.
+pub async fn fetch_version_profile(
+    game_version: &str,
+    loader_version: &str,
+) -> Result<serde_json::Value, Box<dyn Error + Send + Sync>> {
+    let url = format!(
+        "{}/versions/loader/{}/{}/profile/json",
+        FABRIC_META_URL, game_version, loader_version
+    );
+    let resp = reqwest::get(&url).await?.json::<serde_json::Value>().await?;
+    Ok(resp)
+}
+
+/// Generate the version ID for a Fabric installation.
+///
+/// # Arguments
+/// * `game_version` - The Minecraft version
+/// * `loader_version` - The Fabric loader version
+///
+/// # Returns
+/// The version ID string (e.g., "fabric-loader-0.15.6-1.20.4")
+pub fn generate_version_id(game_version: &str, loader_version: &str) -> String {
+    format!("fabric-loader-{}-{}", loader_version, game_version)
+}
+
+/// Install Fabric loader for a specific Minecraft version.
+///
+/// This creates the version JSON file in the versions directory.
+/// The actual library downloads happen during game launch.
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+/// * `game_version` - The Minecraft version (e.g., "1.20.4")
+/// * `loader_version` - The Fabric loader version (e.g., "0.15.6")
+///
+/// # Returns
+/// Information about the installed version.
+pub async fn install_fabric(
+    game_dir: &PathBuf,
+    game_version: &str,
+    loader_version: &str,
+) -> Result<InstalledFabricVersion, Box<dyn Error + Send + Sync>> {
+    // Fetch the version profile from Fabric Meta
+    let profile = fetch_version_profile(game_version, loader_version).await?;
+
+    // Get the version ID from the profile or generate it
+    let version_id = profile
+        .get("id")
+        .and_then(|v| v.as_str())
+        .map(|s| s.to_string())
+        .unwrap_or_else(|| generate_version_id(game_version, loader_version));
+
+    // Create the version directory
+    let version_dir = game_dir.join("versions").join(&version_id);
+    tokio::fs::create_dir_all(&version_dir).await?;
+
+    // Write the version JSON
+    let json_path = version_dir.join(format!("{}.json", version_id));
+    let json_content = serde_json::to_string_pretty(&profile)?;
+    tokio::fs::write(&json_path, json_content).await?;
+
+    Ok(InstalledFabricVersion {
+        id: version_id,
+        minecraft_version: game_version.to_string(),
+        loader_version: loader_version.to_string(),
+        path: json_path,
+    })
+}
+
+/// Check if Fabric is installed for a specific version combination.
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+/// * `game_version` - The Minecraft version
+/// * `loader_version` - The Fabric loader version
+///
+/// # Returns
+/// `true` if the version JSON exists, `false` otherwise.
+pub fn is_fabric_installed(game_dir: &PathBuf, game_version: &str, loader_version: &str) -> bool {
+    let version_id = generate_version_id(game_version, loader_version);
+    let json_path = game_dir
+        .join("versions")
+        .join(&version_id)
+        .join(format!("{}.json", version_id));
+    json_path.exists()
+}
+
+/// List all installed Fabric versions in the game directory.
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+///
+/// # Returns
+/// A list of installed Fabric version IDs.
+pub async fn list_installed_fabric_versions(
+    game_dir: &PathBuf,
+) -> Result<Vec<String>, Box<dyn Error + Send + Sync>> {
+    let versions_dir = game_dir.join("versions");
+    let mut installed = Vec::new();
+
+    if !versions_dir.exists() {
+        return Ok(installed);
+    }
+
+    let mut entries = tokio::fs::read_dir(&versions_dir).await?;
+    while let Some(entry) = entries.next_entry().await? {
+        let name = entry.file_name().to_string_lossy().to_string();
+        if name.starts_with("fabric-loader-") {
+            // Verify the JSON file exists
+            let json_path = entry.path().join(format!("{}.json", name));
+            if json_path.exists() {
+                installed.push(name);
+            }
+        }
+    }
+
+    Ok(installed)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_generate_version_id() {
+        assert_eq!(
+            generate_version_id("1.20.4", "0.15.6"),
+            "fabric-loader-0.15.6-1.20.4"
+        );
+    }
+}
diff --git a/src-tauri/src/core/forge.rs b/src-tauri/src/core/forge.rs
new file mode 100644
index 0000000..7b951ff
--- /dev/null
+++ b/src-tauri/src/core/forge.rs
@@ -0,0 +1,333 @@
+//! Forge Loader support module.
+//!
+//! This module provides functionality to:
+//! - Fetch available Forge versions from the Forge promotions API
+//! - Install Forge loader for a specific Minecraft version
+//!
+//! Note: Forge installation is more complex than Fabric, especially for versions 1.13+.
+//! This implementation focuses on the basic JSON generation approach.
+//! For full Forge 1.13+ support, processor execution would need to be implemented.
+
+use serde::{Deserialize, Serialize};
+use std::error::Error;
+use std::path::PathBuf;
+
+const FORGE_PROMOTIONS_URL: &str =
+    "https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json";
+const FORGE_MAVEN_URL: &str = "https://maven.minecraftforge.net/";
+
+/// Represents a Forge version entry.
+#[derive(Debug, Deserialize, Serialize, Clone)]
+pub struct ForgeVersion {
+    pub version: String,
+    pub minecraft_version: String,
+    #[serde(default)]
+    pub recommended: bool,
+    #[serde(default)]
+    pub latest: bool,
+}
+
+/// Forge promotions response from the API.
+#[derive(Debug, Deserialize)]
+struct ForgePromotions {
+    promos: std::collections::HashMap<String, String>,
+}
+
+/// Information about an installed Forge version.
+#[derive(Debug, Serialize, Clone)]
+pub struct InstalledForgeVersion {
+    pub id: String,
+    pub minecraft_version: String,
+    pub forge_version: String,
+    pub path: PathBuf,
+}
+
+/// Fetch all Minecraft versions supported by Forge.
+///
+/// # Returns
+/// A list of Minecraft version strings that have Forge available.
+pub async fn fetch_supported_game_versions() -> Result<Vec<String>, Box<dyn Error + Send + Sync>> {
+    let promos = fetch_promotions().await?;
+    
+    let mut versions: Vec<String> = promos
+        .promos
+        .keys()
+        .filter_map(|key| {
+            // Keys are like "1.20.4-latest", "1.20.4-recommended"
+            let parts: Vec<&str> = key.split('-').collect();
+            if parts.len() >= 2 {
+                Some(parts[0].to_string())
+            } else {
+                None
+            }
+        })
+        .collect();
+    
+    // Deduplicate and sort
+    versions.sort();
+    versions.dedup();
+    versions.reverse(); // Newest first
+    
+    Ok(versions)
+}
+
+/// Fetch Forge promotions data.
+async fn fetch_promotions() -> Result<ForgePromotions, Box<dyn Error + Send + Sync>> {
+    let resp = reqwest::get(FORGE_PROMOTIONS_URL)
+        .await?
+        .json::<ForgePromotions>()
+        .await?;
+    Ok(resp)
+}
+
+/// Fetch available Forge versions for a specific Minecraft version.
+///
+/// # Arguments
+/// * `game_version` - The Minecraft version (e.g., "1.20.4")
+///
+/// # Returns
+/// A list of Forge versions available for the specified game version.
+pub async fn fetch_forge_versions(
+    game_version: &str,
+) -> Result<Vec<ForgeVersion>, Box<dyn Error + Send + Sync>> {
+    let promos = fetch_promotions().await?;
+    let mut versions = Vec::new();
+
+    // Look for both latest and recommended
+    let latest_key = format!("{}-latest", game_version);
+    let recommended_key = format!("{}-recommended", game_version);
+
+    if let Some(latest) = promos.promos.get(&latest_key) {
+        versions.push(ForgeVersion {
+            version: latest.clone(),
+            minecraft_version: game_version.to_string(),
+            recommended: false,
+            latest: true,
+        });
+    }
+
+    if let Some(recommended) = promos.promos.get(&recommended_key) {
+        // Don't duplicate if recommended == latest
+        if !versions.iter().any(|v| v.version == *recommended) {
+            versions.push(ForgeVersion {
+                version: recommended.clone(),
+                minecraft_version: game_version.to_string(),
+                recommended: true,
+                latest: false,
+            });
+        } else {
+            // Mark the existing one as both
+            if let Some(v) = versions.iter_mut().find(|v| v.version == *recommended) {
+                v.recommended = true;
+            }
+        }
+    }
+
+    Ok(versions)
+}
+
+/// Generate the version ID for a Forge installation.
+///
+/// # Arguments
+/// * `game_version` - The Minecraft version
+/// * `forge_version` - The Forge version
+///
+/// # Returns
+/// The version ID string (e.g., "1.20.4-forge-49.0.38")
+pub fn generate_version_id(game_version: &str, forge_version: &str) -> String {
+    format!("{}-forge-{}", game_version, forge_version)
+}
+
+/// Install Forge for a specific Minecraft version.
+///
+/// Note: This creates a basic version JSON. For Forge 1.13+, the full installation
+/// requires running the Forge installer processors, which is not yet implemented.
+/// This basic implementation works for legacy Forge versions (<1.13) and creates
+/// the structure needed for modern Forge (libraries will need to be downloaded
+/// separately).
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+/// * `game_version` - The Minecraft version (e.g., "1.20.4")
+/// * `forge_version` - The Forge version (e.g., "49.0.38")
+///
+/// # Returns
+/// Information about the installed version.
+pub async fn install_forge(
+    game_dir: &PathBuf,
+    game_version: &str,
+    forge_version: &str,
+) -> Result<InstalledForgeVersion, Box<dyn Error + Send + Sync>> {
+    let version_id = generate_version_id(game_version, forge_version);
+    
+    // Create basic version JSON structure
+    // Note: This is a simplified version. Full Forge installation requires
+    // downloading the installer and running processors.
+    let version_json = create_forge_version_json(game_version, forge_version)?;
+
+    // Create the version directory
+    let version_dir = game_dir.join("versions").join(&version_id);
+    tokio::fs::create_dir_all(&version_dir).await?;
+
+    // Write the version JSON
+    let json_path = version_dir.join(format!("{}.json", version_id));
+    let json_content = serde_json::to_string_pretty(&version_json)?;
+    tokio::fs::write(&json_path, json_content).await?;
+
+    Ok(InstalledForgeVersion {
+        id: version_id,
+        minecraft_version: game_version.to_string(),
+        forge_version: forge_version.to_string(),
+        path: json_path,
+    })
+}
+
+/// Create a basic Forge version JSON.
+///
+/// This creates a minimal version JSON that inherits from vanilla and adds
+/// the Forge libraries. For full functionality with Forge 1.13+, the installer
+/// would need to be run to patch the game.
+fn create_forge_version_json(
+    game_version: &str,
+    forge_version: &str,
+) -> Result<serde_json::Value, Box<dyn Error + Send + Sync>> {
+    let version_id = generate_version_id(game_version, forge_version);
+    let forge_maven_coord = format!(
+        "net.minecraftforge:forge:{}-{}",
+        game_version, forge_version
+    );
+
+    // Determine main class based on version
+    // Forge 1.13+ uses different launchers
+    let (main_class, libraries) = if is_modern_forge(game_version) {
+        // Modern Forge (1.13+) uses cpw.mods.bootstraplauncher
+        (
+            "cpw.mods.bootstraplauncher.BootstrapLauncher".to_string(),
+            vec![
+                create_library_entry(&forge_maven_coord, Some(FORGE_MAVEN_URL)),
+                create_library_entry(
+                    &format!("net.minecraftforge:forge:{}-{}:universal", game_version, forge_version),
+                    Some(FORGE_MAVEN_URL),
+                ),
+            ],
+        )
+    } else {
+        // Legacy Forge uses LaunchWrapper
+        (
+            "net.minecraft.launchwrapper.Launch".to_string(),
+            vec![
+                create_library_entry(&forge_maven_coord, Some(FORGE_MAVEN_URL)),
+                create_library_entry("net.minecraft:launchwrapper:1.12", None),
+            ],
+        )
+    };
+
+    let json = serde_json::json!({
+        "id": version_id,
+        "inheritsFrom": game_version,
+        "type": "release",
+        "mainClass": main_class,
+        "libraries": libraries,
+        "arguments": {
+            "game": [],
+            "jvm": []
+        }
+    });
+
+    Ok(json)
+}
+
+/// Create a library entry for the version JSON.
+fn create_library_entry(name: &str, maven_url: Option<&str>) -> serde_json::Value {
+    let mut entry = serde_json::json!({
+        "name": name
+    });
+
+    if let Some(url) = maven_url {
+        entry["url"] = serde_json::Value::String(url.to_string());
+    }
+
+    entry
+}
+
+/// Check if the Minecraft version uses modern Forge (1.13+).
+fn is_modern_forge(game_version: &str) -> bool {
+    let parts: Vec<&str> = game_version.split('.').collect();
+    if parts.len() >= 2 {
+        if let (Ok(major), Ok(minor)) = (parts[0].parse::<u32>(), parts[1].parse::<u32>()) {
+            return major > 1 || (major == 1 && minor >= 13);
+        }
+    }
+    false
+}
+
+/// Check if Forge is installed for a specific version combination.
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+/// * `game_version` - The Minecraft version
+/// * `forge_version` - The Forge version
+///
+/// # Returns
+/// `true` if the version JSON exists, `false` otherwise.
+pub fn is_forge_installed(game_dir: &PathBuf, game_version: &str, forge_version: &str) -> bool {
+    let version_id = generate_version_id(game_version, forge_version);
+    let json_path = game_dir
+        .join("versions")
+        .join(&version_id)
+        .join(format!("{}.json", version_id));
+    json_path.exists()
+}
+
+/// List all installed Forge versions in the game directory.
+///
+/// # Arguments
+/// * `game_dir` - The .minecraft directory path
+///
+/// # Returns
+/// A list of installed Forge version IDs.
+pub async fn list_installed_forge_versions(
+    game_dir: &PathBuf,
+) -> Result<Vec<String>, Box<dyn Error + Send + Sync>> {
+    let versions_dir = game_dir.join("versions");
+    let mut installed = Vec::new();
+
+    if !versions_dir.exists() {
+        return Ok(installed);
+    }
+
+    let mut entries = tokio::fs::read_dir(&versions_dir).await?;
+    while let Some(entry) = entries.next_entry().await? {
+        let name = entry.file_name().to_string_lossy().to_string();
+        if name.contains("-forge-") {
+            // Verify the JSON file exists
+            let json_path = entry.path().join(format!("{}.json", name));
+            if json_path.exists() {
+                installed.push(name);
+            }
+        }
+    }
+
+    Ok(installed)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_generate_version_id() {
+        assert_eq!(
+            generate_version_id("1.20.4", "49.0.38"),
+            "1.20.4-forge-49.0.38"
+        );
+    }
+
+    #[test]
+    fn test_is_modern_forge() {
+        assert!(!is_modern_forge("1.12.2"));
+        assert!(is_modern_forge("1.13"));
+        assert!(is_modern_forge("1.20.4"));
+        assert!(is_modern_forge("1.21"));
+    }
+}