<?php

namespace SilverStripe\View;

use InvalidArgumentException;
use SilverStripe\Core\ClassInfo;
use SilverStripe\ORM\FieldType\DBField;

/**
 * This extends SSViewer_Scope to mix in data on top of what the item provides. This can be "global"
 * data that is scope-independant (like BaseURL), or type-specific data that is layered on top cross-cut like
 * (like $FirstLast etc).
 *
 * It's separate from SSViewer_Scope to keep that fairly complex code as clean as possible.
 */
class SSViewer_DataPresenter extends SSViewer_Scope
{
    /**
     * List of global property providers
     *
     * @internal
     * @var TemplateGlobalProvider[]|null
     */
    private static $globalProperties = null;

    /**
     * List of global iterator providers
     *
     * @internal
     * @var TemplateIteratorProvider[]|null
     */
    private static $iteratorProperties = null;

    /**
     * Overlay variables. Take precedence over anything from the current scope
     *
     * @var array|null
     */
    protected $overlay;

    /**
     * Underlay variables. Concede precedence to overlay variables or anything from the current scope
     * @var array|null
     */
    protected $underlay;

    public function __construct($item, $overlay = null, $underlay = null, $inheritedScope = null)
    {
        parent::__construct($item, $inheritedScope);

        // Build up global property providers array only once per request
        if (self::$globalProperties === null) {
            self::$globalProperties = array();
            // Get all the exposed variables from all classes that implement the TemplateGlobalProvider interface
            $this->createCallableArray(
                self::$globalProperties,
                TemplateGlobalProvider::class,
                "get_template_global_variables"
            );
        }

        // Build up iterator property providers array only once per request
        if (self::$iteratorProperties === null) {
            self::$iteratorProperties = array();
            // Get all the exposed variables from all classes that implement the TemplateIteratorProvider interface
            // //call non-statically
            $this->createCallableArray(
                self::$iteratorProperties,
                TemplateIteratorProvider::class,
                "get_template_iterator_variables",
                true
            );
        }

        $this->overlay = $overlay ? $overlay : array();
        $this->underlay = $underlay ? $underlay : array();
    }

    protected function createCallableArray(&$extraArray, $interfaceToQuery, $variableMethod, $createObject = false)
    {
        $implementers = ClassInfo::implementorsOf($interfaceToQuery);
        if ($implementers) {
            foreach ($implementers as $implementer) {
                // Create a new instance of the object for method calls
                if ($createObject) {
                    $implementer = new $implementer();
                }

                // Get the exposed variables
                $exposedVariables = call_user_func(array($implementer, $variableMethod));

                foreach ($exposedVariables as $varName => $details) {
                    if (!is_array($details)) {
                        $details = array(
                            'method' => $details,
                            'casting' => ViewableData::config()->uninherited('default_cast')
                        );
                    }

                    // If just a value (and not a key => value pair), use it for both key and value
                    if (is_numeric($varName)) {
                        $varName = $details['method'];
                    }

                    // Add in a reference to the implementing class (might be a string class name or an instance)
                    $details['implementer'] = $implementer;

                    // And a callable array
                    if (isset($details['method'])) {
                        $details['callable'] = array($implementer, $details['method']);
                    }

                    // Save with both uppercase & lowercase first letter, so either works
                    $lcFirst = strtolower($varName[0]) . substr($varName, 1);
                    $extraArray[$lcFirst] = $details;
                    $extraArray[ucfirst($varName)] = $details;
                }
            }
        }
    }

    /**
     * Get the injected value
     *
     * @param string $property Name of property
     * @param array $params
     * @param bool $cast If true, an object is always returned even if not an object.
     * @return array Result array with the keys 'value' for raw value, or 'obj' if contained in an object
     * @throws InvalidArgumentException
     */
    public function getInjectedValue($property, $params, $cast = true)
    {
        // Get source for this value
        $source = $this->getValueSource($property);
        if (!$source) {
            return null;
        }

        // Look up the value - either from a callable, or from a directly provided value
        $res = [];
        if (isset($source['callable'])) {
            $res['value'] = call_user_func_array($source['callable'], $params);
        } elseif (isset($source['value'])) {
            $res['value'] = $source['value'];
        } else {
            throw new InvalidArgumentException(
                "Injected property $property does't have a value or callable value source provided"
            );
        }

        // If we want to provide a casted object, look up what type object to use
        if ($cast) {
            $res['obj'] = $this->castValue($res['value'], $source);
        }
        return $res;
    }

    /**
     * Store the current overlay (as it doesn't directly apply to the new scope
     * that's being pushed). We want to store the overlay against the next item
     * "up" in the stack (hence upIndex), rather than the current item, because
     * SSViewer_Scope::obj() has already been called and pushed the new item to
     * the stack by this point
     *
     * @return SSViewer_Scope
     */
    public function pushScope()
    {
        $scope = parent::pushScope();
        $upIndex = $this->getUpIndex();

        if ($upIndex !== null) {
            $itemStack = $this->getItemStack();
            $itemStack[$upIndex][SSViewer_Scope::ITEM_OVERLAY] = $this->overlay;

            $this->setItemStack($itemStack);
            $this->overlay = array();
        }

        return $scope;
    }

    /**
     * Now that we're going to jump up an item in the item stack, we need to
     * restore the overlay that was previously stored against the next item "up"
     * in the stack from the current one
     *
     * @return SSViewer_Scope
     */
    public function popScope()
    {
        $upIndex = $this->getUpIndex();

        if ($upIndex !== null) {
            $itemStack = $this->getItemStack();
            $this->overlay = $itemStack[$this->getUpIndex()][SSViewer_Scope::ITEM_OVERLAY];
        }

        return parent::popScope();
    }

    /**
     * $Up and $Top need to restore the overlay from the parent and top-level
     * scope respectively.
     *
     * @param string $name
     * @param array $arguments
     * @param bool $cache
     * @param string $cacheName
     * @return $this
     */
    public function obj($name, $arguments = [], $cache = false, $cacheName = null)
    {
        $overlayIndex = false;

        switch ($name) {
            case 'Up':
                $upIndex = $this->getUpIndex();
                if ($upIndex === null) {
                    user_error('Up called when we\'re already at the top of the scope', E_USER_ERROR);
                }

                $overlayIndex = $upIndex; // Parent scope
                break;
            case 'Top':
                $overlayIndex = 0; // Top-level scope
                break;
        }

        if ($overlayIndex !== false) {
            $itemStack = $this->getItemStack();
            if (!$this->overlay && isset($itemStack[$overlayIndex][SSViewer_Scope::ITEM_OVERLAY])) {
                $this->overlay = $itemStack[$overlayIndex][SSViewer_Scope::ITEM_OVERLAY];
            }
        }

        parent::obj($name, $arguments, $cache, $cacheName);
        return $this;
    }

    public function getObj($name, $arguments = [], $cache = false, $cacheName = null)
    {
        $result = $this->getInjectedValue($name, (array)$arguments);
        if ($result) {
            return $result['obj'];
        }
        return parent::getObj($name, $arguments, $cache, $cacheName);
    }

    public function __call($name, $arguments)
    {
        //extract the method name and parameters
        $property = $arguments[0];  //the name of the public function being called

        //the public function parameters in an array
        if (isset($arguments[1]) && $arguments[1] != null) {
            $params = $arguments[1];
        } else {
            $params = array();
        }

        $val = $this->getInjectedValue($property, $params);
        if ($val) {
            $obj = $val['obj'];
            if ($name === 'hasValue') {
                $res = $obj instanceof ViewableData
                    ? $obj->exists()
                    : (bool)$obj;
            } else {
                // XML_val
                $res = $obj->forTemplate();
            }
            $this->resetLocalScope();
            return $res;
        } else {
            return parent::__call($name, $arguments);
        }
    }

    /**
     * Evaluate a template override
     *
     * @param string $property Name of override requested
     * @param array $overrides List of overrides available
     * @return null|array Null if not provided, or array with 'value' or 'callable' key
     */
    protected function processTemplateOverride($property, $overrides)
    {
        if (!isset($overrides[$property])) {
            return null;
        }

        // Detect override type
        $override = $overrides[$property];

        // Late-evaluate this value
        if (is_callable($override)) {
            $override = $override();

            // Late override may yet return null
            if (!isset($override)) {
                return null;
            }
        }

        return [ 'value' => $override ];
    }

    /**
     * Determine source to use for getInjectedValue
     *
     * @param string $property
     * @return array|null
     */
    protected function getValueSource($property)
    {
        // Check for a presenter-specific override
        $overlay = $this->processTemplateOverride($property, $this->overlay);
        if (isset($overlay)) {
            return $overlay;
        }

        // Check if the method to-be-called exists on the target object - if so, don't check any further
        // injection locations
        $on = $this->itemIterator ? $this->itemIterator->current() : $this->item;
        if (isset($on->$property) || method_exists($on, $property)) {
            return null;
        }

        // Check for a presenter-specific override
        $underlay = $this->processTemplateOverride($property, $this->underlay);
        if (isset($underlay)) {
            return $underlay;
        }

        // Then for iterator-specific overrides
        if (array_key_exists($property, self::$iteratorProperties)) {
            $source = self::$iteratorProperties[$property];
            /** @var TemplateIteratorProvider $implementer */
            $implementer = $source['implementer'];
            if ($this->itemIterator) {
                // Set the current iterator position and total (the object instance is the first item in
                // the callable array)
                $implementer->iteratorProperties(
                    $this->itemIterator->key(),
                    $this->itemIteratorTotal
                );
            } else {
                // If we don't actually have an iterator at the moment, act like a list of length 1
                $implementer->iteratorProperties(0, 1);
            }
            return $source;
        }

        // And finally for global overrides
        if (array_key_exists($property, self::$globalProperties)) {
            return self::$globalProperties[$property];  //get the method call
        }

        // No value
        return null;
    }

    /**
     * Ensure the value is cast safely
     *
     * @param mixed $value
     * @param array $source
     * @return DBField
     */
    protected function castValue($value, $source)
    {
        // Already cast
        if (is_object($value)) {
            return $value;
        }

        // Get provided or default cast
        $casting = empty($source['casting'])
            ? ViewableData::config()->uninherited('default_cast')
            : $source['casting'];

        return DBField::create_field($casting, $value);
    }
}