// package launch handles Minecraft process launching.
package launch

import (
	"encoding/json"
	"fmt"
	"os"
)

// Manifest describes the contents of a modpack as provided by the backend.
type Manifest struct {
	MinecraftVersion string         `json:"minecraft_version"`
	JavaVersion      int            `json:"java_version"`
	ServerInfo       ServerInfo     `json:"server_info"`
	Files            []ManifestFile `json:"files"`
	Launch            LaunchConfig   `json:"launch"`
}

// ServerInfo is the game server address injected into servers.dat.
type ServerInfo struct {
	Name string `json:"name"`
	IP   string `json:"ip"`
}

// ManifestFile is a single file entry with SHA-1 verification.
type ManifestFile struct {
	Path string `json:"path"`
	Hash string `json:"hash"`
	Size int64  `json:"size"`
	URL  string `json:"url"`
}

// LaunchConfig contains the JVM and game arguments template.
type LaunchConfig struct {
	MainClass       string   `json:"mainClass"`
	JVMArgs         []string `json:"jvmArgs"`
	GameArgs        []string `json:"gameArgs"`
	NativeLibs      []string `json:"nativeLibs"`
	AuthLibInjector string   `json:"authLibInjector"` // URL to authlib-injector.jar
}

// LoadManifest reads and parses a manifest.json from disk.
func LoadManifest(path string) (*Manifest, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading manifest %s: %w", path, err)
	}
	var m Manifest
	if err := json.Unmarshal(data, &m); err != nil {
		return nil, fmt.Errorf("parsing manifest %s: %w", path, err)
	}
	return &m, nil
}

// LibraryFiles returns the subset of Files that are .jar libraries (classpath).
func (m *Manifest) LibraryFiles() []ManifestFile {
	var libs []ManifestFile
	for _, f := range m.Files {
		if len(f.Path) > 4 && f.Path[len(f.Path)-4:] == ".jar" {
			libs = append(libs, f)
		}
	}
	return libs
}

// ModFiles returns the subset of Files that go into the mods/ directory.
func (m *Manifest) ModFiles() []ManifestFile {
	var mods []ManifestFile
	for _, f := range m.Files {
		if len(f.Path) > 5 && f.Path[:5] == "mods/" {
			mods = append(mods, f)
		}
	}
	return mods
}