<?php

/*
 * This file is part of Psy Shell.
 *
 * (c) 2012-2017 Justin Hileman
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Psy;

/**
 * The Shell execution context.
 *
 * This class encapsulates the current variables, most recent return value and
 * exception, and the current namespace.
 */
class Context
{
    private static $specialNames = array('_', '_e', '__psysh__', 'this');

    // Whitelist a very limited number of command-scope magic variable names.
    // This might be a bad idea, but future me can sort it out.
    private static $commandScopeNames = array(
        '__function', '__method', '__class', '__namespace', '__file', '__line', '__dir',
    );

    private $scopeVariables = array();
    private $commandScopeVariables = array();
    private $lastException;
    private $returnValue;
    private $boundObject;

    /**
     * Get a context variable.
     *
     * @throws InvalidArgumentException If the variable is not found in the current context
     *
     * @param string $name
     *
     * @return mixed
     */
    public function get($name)
    {
        switch ($name) {
            case '_':
                return $this->returnValue;

            case '_e':
                if (isset($this->lastException)) {
                    return $this->lastException;
                }
                break;

            case 'this':
                if (isset($this->boundObject)) {
                    return $this->boundObject;
                }
                break;

            case '__function':
            case '__method':
            case '__class':
            case '__namespace':
            case '__file':
            case '__line':
            case '__dir':
                if (array_key_exists($name, $this->commandScopeVariables)) {
                    return $this->commandScopeVariables[$name];
                }
                break;

            default:
                if (array_key_exists($name, $this->scopeVariables)) {
                    return $this->scopeVariables[$name];
                }
                break;
        }

        throw new \InvalidArgumentException('Unknown variable: $' . $name);
    }

    /**
     * Get all defined variables.
     *
     * @return array
     */
    public function getAll()
    {
        return array_merge($this->scopeVariables, $this->getSpecialVariables());
    }

    /**
     * Get all defined magic variables: $_, $_e, $__class, $__file, etc.
     *
     * @return array
     */
    public function getSpecialVariables()
    {
        $vars = array(
            '_' => $this->returnValue,
        );

        if (isset($this->lastException)) {
            $vars['_e'] = $this->lastException;
        }

        if (isset($this->boundObject)) {
            $vars['this'] = $this->boundObject;
        }

        return array_merge($vars, $this->commandScopeVariables);
    }

    /**
     * Set all scope variables.
     *
     * This method does *not* set any of the magic variables: $_, $_e, $__class, $__file, etc.
     *
     * @param array $vars
     */
    public function setAll(array $vars)
    {
        foreach (self::$specialNames as $key) {
            unset($vars[$key]);
        }

        foreach (self::$commandScopeNames as $key) {
            unset($vars[$key]);
        }

        $this->scopeVariables = $vars;
    }

    /**
     * Set the most recent return value.
     *
     * @param mixed $value
     */
    public function setReturnValue($value)
    {
        $this->returnValue = $value;
    }

    /**
     * Get the most recent return value.
     *
     * @return mixed
     */
    public function getReturnValue()
    {
        return $this->returnValue;
    }

    /**
     * Set the most recent Exception.
     *
     * @param \Exception $e
     */
    public function setLastException(\Exception $e)
    {
        $this->lastException = $e;
    }

    /**
     * Get the most recent Exception.
     *
     * @throws InvalidArgumentException If no Exception has been caught
     *
     * @return null|Exception
     */
    public function getLastException()
    {
        if (!isset($this->lastException)) {
            throw new \InvalidArgumentException('No most-recent exception');
        }

        return $this->lastException;
    }

    /**
     * Set the bound object ($this variable) for the interactive shell.
     *
     * @param object|null $boundObject
     */
    public function setBoundObject($boundObject)
    {
        $this->boundObject = is_object($boundObject) ? $boundObject : null;
    }

    /**
     * Get the bound object ($this variable) for the interactive shell.
     *
     * @return object|null
     */
    public function getBoundObject()
    {
        return $this->boundObject;
    }

    /**
     * Set command-scope magic variables: $__class, $__file, etc.
     *
     * @param array $commandScopeVariables
     */
    public function setCommandScopeVariables(array $commandScopeVariables)
    {
        $vars = array();
        foreach ($commandScopeVariables as $key => $value) {
            // kind of type check
            if (is_scalar($value) && in_array($key, self::$commandScopeNames)) {
                $vars[$key] = $value;
            }
        }

        $this->commandScopeVariables = $vars;
    }

    /**
     * Get command-scope magic variables: $__class, $__file, etc.
     *
     * @return array
     */
    public function getCommandScopeVariables()
    {
        return $this->commandScopeVariables;
    }

    /**
     * Get unused command-scope magic variables names: __class, __file, etc.
     *
     * This is used by the shell to unset old command-scope variables after a
     * new batch is set.
     *
     * @return array Array of unused variable names
     */
    public function getUnusedCommandScopeVariableNames()
    {
        return array_diff(self::$commandScopeNames, array_keys($this->commandScopeVariables));
    }

    /**
     * Check whether a variable name is a magic variable.
     *
     * @param string $name
     *
     * @return bool
     */
    public static function isSpecialVariableName($name)
    {
        return in_array($name, self::$specialNames) || in_array($name, self::$commandScopeNames);
    }
}