package emu.nebula.command;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

import org.reflections.Reflections;

import emu.nebula.Nebula;
import emu.nebula.game.player.Player;
import it.unimi.dsi.fastutil.objects.Object2ObjectMap;
import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
import lombok.Getter;

@Getter
public class CommandManager {
    private Object2ObjectMap<String, CommandHandler> labels;
    private Object2ObjectMap<String, CommandHandler> commands;
    
    public CommandManager() {
        this.labels = new Object2ObjectOpenHashMap<>();
        this.commands = new Object2ObjectOpenHashMap<>();
        
        // Scan for commands
        var commandClasses = new Reflections(CommandManager.class.getPackageName()).getTypesAnnotatedWith(Command.class);
        
        for (var cls : commandClasses) {
            if (!CommandHandler.class.isAssignableFrom(cls)) {
                continue;
            }
            
            try {
                CommandHandler handler = (CommandHandler) cls.getDeclaredConstructor().newInstance();
                this.registerCommand(handler);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    
    /**
     * Adds a command that players and server console users can use. Command handlers must have the proper command annotation attached to them.
     */
    public CommandManager registerCommand(CommandHandler handler) {
        Command command = handler.getClass().getAnnotation(Command.class);
        if (command == null) return this;
        
        this.getLabels().put(command.label(), handler);
        this.getCommands().put(command.label(), handler);
        
        for (String alias : command.aliases()) {
            this.getCommands().put(alias, handler);
        }
        
        return this;
    }
    
    /**
     * Removes a command from use.
     * @param label The command name
     * @return
     */
    public CommandManager unregisterCommand(String label) {
        CommandHandler handler = this.getLabels().get(label);
        if (handler == null) return this;
        
        Command command = handler.getClass().getAnnotation(Command.class);
        if (command == null) {
            return this;
        }
        
        this.getLabels().remove(command.label());
        this.getCommands().remove(command.label());
        
        for (String alias : command.aliases()) {
            this.getCommands().remove(alias);
        }
        
        return this;
    }
    
    /**
     * Checks if the sender has permission to use this command. Will always return true if the sender is the server console.
     * @param sender The sender of the command.
     * @param command
     * @return true if the sender has permission to use this command
     */
    public boolean checkPermission(Player sender, Command command) {
        if (sender == null || command.permission().isEmpty()) {
            return true;
        }
        
        return sender.getAccount().hasPermission(command.permission());
    }
    
    /**
     * Checks if the sender has permission to use this command on other players. Will always return true if the sender is the server console.
     * @param sender The sender of the command.
     * @param command
     * @return true if the sender has permission to use this command
     */
    private boolean checkTargetPermission(Player sender, Command command) {
        if (sender == null || command.permission().isEmpty()) {
            return true;
        }
        
        return sender.getAccount().hasPermission("target." + command.permission());
    }
    
    public CommandResult invoke(Player sender, String message) {
        // Parse message into arguments
        List<String> args = Arrays.stream(message.split(" ")).collect(Collectors.toCollection(ArrayList::new));
        
        // Get command label
        String label = args.remove(0).toLowerCase();
        
        // Filter out command prefixes
        if (label.startsWith("/") || label.startsWith("!")) {
            label = label.substring(1);
        }
        
        // Get command handler
        CommandHandler handler = this.commands.get(label);
        
        // Create result object
        var result = CommandResult.builder();

        // Execute command
        if (handler != null) {
            // Get command annotation data
            Command command = handler.getData();
            
            // Check if sender has permission to run the command.
            if (sender != null && !this.checkPermission(sender, command)) {
                // We have a double null check here just in case
                result.message("Error - You do not have permission to use this command");
                return result.build();
            }
            
            // Build command arguments
            CommandArgs cmdArgs = new CommandArgs(sender, args);
            
            // Check targeted permission
            if (sender != cmdArgs.getTarget() && !this.checkTargetPermission(sender, command)) {
                result.message("Error - You do not have permission to use this command on another player");
                return result.build();
            }
            
            // Make sure our command has a target
            if (command.requireTarget() && cmdArgs.getTarget() == null) {
                result.message("Error - Targeted player not found or offline");
                return result.build();
            }
            
            // Log
            if (sender != null && Nebula.getConfig().getLogOptions().commands) {
                Nebula.getLogger().info("[UID: " + sender.getUid() + "] " + sender.getName() + " used command: " + message);
            }
            
            // Run command
            String commandMessage = handler.execute(cmdArgs);
            
            // Parse out last newline
            if (commandMessage.endsWith("\n")) {
                commandMessage = commandMessage.substring(0, commandMessage.length() - 1);
            }
            
            // Set result data
            result.command(handler);
            result.message(commandMessage);
        } else {
            result.message("Invalid Command!");
        }
        
        return result.build();
    }
}