<?php
// $Id$

require('context.core.inc');

define('CONTEXT_GET', 0);
define('CONTEXT_SET', 1);
define('CONTEXT_ISSET', 2);
define('CONTEXT_CLEAR', 3);

define('CONTEXT_STORAGE_DEFAULT', 0);
define('CONTEXT_STORAGE_OVERRIDDEN', 1);
define('CONTEXT_STORAGE_NORMAL', 2);

define('CONTEXT_STATUS_DISABLED', 0);
define('CONTEXT_STATUS_ENABLED', 1);

/**
 * Master context function. Avoid calling this directly -- use one of the helper functions below.
 *
 * @param $op
 *   The operation to perform - handled by the context helper functions. Use them.
 * @param $namespace
 *   A string to be used as the namespace for the context information.
 * @param $attribute
 *   Usually a string to be used as a key to set/retrieve context information. An array can
 *   also be used when setting context to establish an entire context namespace at once.
 *   (At some point objects may also be accepted, but currently functionaliy isn't complete.)
 * @param $value
 *   A value to set for the provided key. If omitted the value will be set to true.
 *
 * @return
 *   Either the requested value, or false if the operation fails.
 */
function context_context($op = CONTEXT_GET, $namespace = null, $attribute = null, $value = null) {
  static $context;
  $context = !$context ? array() : $context;
  switch ($op) {
    case CONTEXT_GET:
      // return entire context
      if (!$namespace) {
        return $context;
      }
      // return entire space if set
      else if (isset($context[(string) $namespace])) {
        // return val of key from space
        if (is_array($context[(string) $namespace]) && isset($context[(string) $namespace][(string) $attribute])) {
          return $context[(string) $namespace][(string) $attribute];
        }
        elseif (!$attribute){
          return $context[(string) $namespace];
        }
      }
      break;
    case CONTEXT_SET:
      // bail if invalid space is specified or context is already set
      if (is_string($namespace) || is_int($namespace)) {
        // initialize namespace if no key is specified
        if (!$attribute) {
          $context[(string) $namespace] = array();
          return true;
        }
        // set to true if key is a usable identifier. otherwise, allow a key or object to be inserted
        if (!$value) {
          if (is_string($attribute) || is_int($attribute)) {
            $context[(string) $namespace][(string) $attribute] = true;
            return true;
          }
          elseif (is_array($attribute) || is_object($attribute)) {
            $context[(string) $namespace] = $attribute;
            return true;
          }
        }
        // set value if key is valid
        if ((is_string($attribute) || is_int($attribute)) && $value) {
          $context[$namespace][$attribute] = $value;
          return true;
        }
      }
      break;
    case CONTEXT_ISSET:
      // return entire context
      if (!$namespace) return false;
      if (!$attribute) {
        // return entire space if set
        return isset($context[$namespace]);
      }
      // return val of key from space
      return isset($context[$namespace][$attribute]);
    case CONTEXT_CLEAR:
      $context = array();
      return true;
  }
  return false;
}

/**
 * Sets a context by namespace + attribute.
 */
function context_set($namespace, $attribute = null, $value = null) {
  return context_context(CONTEXT_SET, $namespace, $attribute, $value);
}

/**
 * Retrieves a context by namespace + (optional) attribute.
 */
function context_get($namespace = null, $attribute = null) {
  return context_context(CONTEXT_GET, $namespace, $attribute, null);
}

/**
 * Returns a boolean for whether a context namespace + attribute have been set.
 */
function context_isset($namespace = null, $attribute = null) {
  return context_context(CONTEXT_ISSET, $namespace, $attribute, null);
}

/**
 * Deprecated context_exists() function. Retained for backwards
 * compatibility -- please use context_isset() instead.
 */
function context_exists($namespace = null, $attribute = null) {
  return context_context(CONTEXT_ISSET, $namespace, $attribute, null);
}

/**
 * Clears static context array() -- meant only for testing
 */
function context_clear() {
  return context_context(CONTEXT_CLEAR);
}

/**
 * Implemented hooks ==================================================
 */

/**
 * Implementation of hook_init().
 */
function context_init() {
  // In general it is advisable to avoid using context_set_by_condition() at
  // this stage of the Drupal page load as it caches the condition map.
  $current_path = drupal_get_path_alias($_GET['q']);
  foreach (context_enabled_contexts() as $identifier => $context) {
    // context integration against paths
    if (!empty($context->path) && is_array($context->path)) {
      $paths = implode("\n", $context->path);
      if (drupal_match_path($current_path, $paths)) {
        context_set($context->namespace, $context->attribute, $context->value);
      }
    }
    // context integration for sitewide context
    if (!empty($context->sitewide)) {
      context_set($context->namespace, $context->attribute, $context->value);
    }
  }
}

/**
 * Implementation of hook_flush_caches().
 */
function context_flush_caches() {
  context_invalidate_cache();
  return array();
}

/**
 * L'CRUD FUNCTIONS ===================================================
 */

/**
 * Context loader.
 *
 * @param $context
 *   The parameters to use for loading this context. Can be an integer
 *   cid or partial context object.
 *
 * @return
 *   Returns a fully-loaded context definition.
 */
function context_load_context($context, $reset = FALSE) {
  static $cache = array();
  // Argument is a cid
  if (is_numeric($context)) {
    $cid = $context;
    if (!isset($cache[$cid])) {
      $context = db_fetch_object(db_query("SELECT * FROM {context} WHERE cid = %d", $cid));
    }
    else {
      return $cache[$cid];
    }
  }
  // Context object has an associated cid
  else if (is_object($context) && isset($context->cid)) {
    $context = db_fetch_object(db_query("SELECT * FROM {context} WHERE cid = %d", $context->cid));
  }
  // Context object has no cid -- we'll try to load by ns/attr/val
  else if (is_object($context) && $context->namespace && $context->attribute && $context->value) {
    $args = array($context->namespace, $context->attribute, $context->value);
    $context = db_fetch_object(db_query("SELECT * FROM {context} WHERE namespace = '%s' AND attribute = '%s' AND value = '%s'", $args));
  }

  // Unserialize and populate associations
  if (!empty($context->data)) {
    $context = context_unpack_context($context);
    $cache[$context->cid] = $context;
    return $context;
  }

  return false;
}

/**
 * Inserts or updates a context object into the database.
 * @TODO: should probably return the new cid on success -- make sure
 * this doesn't break any checks elsewhere.
 *
 * @param $context
 *   The context object to be inserted.
 *
 * @return
 *   Returns true on success, false on failure.
 */
function context_save_context($context) {
  // Insert or update the core context definition
  if (!isset($context->cid)) {
    $existing = context_load_context($context, TRUE);
    if ($existing && $existing->cid) {
      return false;
    }
    else {
      $context = context_pack_context($context);
      drupal_write_record('context', $context);
    }
  }
  else {
    $context = context_pack_context($context);
    drupal_write_record('context', $context, 'cid'); 
  }

  // Invalidate context cache
  cache_clear_all('context', 'cache');
  return TRUE;
}

/**
 * Deletes an existing context.
 *
 * @param $context
 *   The context object to be deleted. The $context->cid property is
 *   necessary for this operation.
 *
 * @return
 *   Returns true on success, false on failure.
 */
function context_delete_context($context) {
  if ($context = context_load_context($context, TRUE)) {
    db_query("DELETE FROM {context} WHERE cid = %d", $context->cid);

    // Invalidate context cache
    cache_clear_all('context', 'cache');

    return true;
  }
  return false;
}

/**
 * Helper function to pack a context object to be stored in the database.
 */
function context_pack_context($context) {
  $packed = new StdClass();

  $packed->cid = $context->cid;
  $packed->namespace = $context->namespace;
  $packed->attribute = $context->attribute;
  $packed->value = $context->value;

  unset($context->cid);
  unset($context->namespace);
  unset($context->attribute);
  unset($context->value);

  // Clear out storage and status information
  unset($context->type);
  unset($context->status);

  // Serialize associations as data array
  $context = (array) $context;
  $packed->data = serialize($context);

  return $packed;
}

/**
 * Helper function to unpack a context object that has been retrieved from the database.
 * @TODO: Remove this once ->conditions and ->reactions issue has been resolved.
 */
function context_unpack_context($context) {
  if (!empty($context->data)) {
    $data = unserialize($context->data);
    foreach ($data as $k => $v) {
      $context->{$k} = $v;
    }
    unset($context->data);
  }
  return $context;
}

/**
 * API FUNCTIONS ======================================================
 */

/**
 * Provides an array of all contexts provided by modules and in the database.
 *
 * @param $reset
 *   Boolean to clear the static cached array of contexts.
 *
 * @return
 *   An array of context objects.
 */
function context_contexts($reset = FALSE) {
  static $contexts;
  if (!$contexts || $reset) {
    $contexts = array();
    foreach (module_implements('context_default_contexts') as $module) {
      $function = $module .'_context_default_contexts';
      $c = call_user_func($function);
      if (!empty($c)) {
        foreach ($c as $context) {
          $context = (object) $context;
          $context->type = CONTEXT_STORAGE_DEFAULT;
          $identifier = "{$context->namespace}-{$context->attribute}-{$context->value}";
          $contexts[$identifier] = $context;
        }
      }
    }
    // Allow other modules to alter contexts
    drupal_alter('context_default_contexts', $contexts);

    // Collect normal & overridden contexts
    $result = db_query("SELECT * FROM {context} ORDER BY namespace ASC, attribute ASC, value ASC");
    while ($context = db_fetch_object($result)) {
      $context = context_unpack_context($context);
      $key = "{$context->namespace}-{$context->attribute}-{$context->value}";
      if (isset($contexts[$key])) {
        $contexts[$key] = $context;
        $contexts[$key]->type = CONTEXT_STORAGE_OVERRIDDEN;
      }
      else {
        $contexts[$key] = $context;
        $contexts[$key]->type = CONTEXT_STORAGE_NORMAL;
      }
    }

    // Mark the status of each context
    foreach ($contexts as $key => $context) {
      $contexts[$key]->status = context_status($context);
    }
  }
  return $contexts;
}

/**
 * Wrapper around cache_get() to make it easier for context to pull different
 * datastores from a single cache row.
 */
function context_cache_get($key, $reset = FALSE) {
  static $cache;
  if (!isset($cache) || $reset) {
    $cache = cache_get('context', 'cache');
    $cache = $cache ? $cache->data : array();
  }
  return !empty($cache[$key]) ? $cache[$key] : FALSE;
}

/**
 * Wrapper around cache_set() to make it easier for context to write different
 * datastores to a single cache row.
 */
function context_cache_set($key, $value) {
  $cache = cache_get('context', 'cache');
  $cache = $cache ? $cache->data : array();
  $cache[$key] = $value;
  cache_set('context', $cache);
}

/**
 * Retrieves all enabled contexts from the cache.
 */
function context_enabled_contexts($namespace = NULL, $reset = FALSE) {
  static $enabled;
  static $namespaces;
  if (!isset($enabled) || $reset) {
    $enabled = array();
    $cache = context_cache_get('enabled');
    if ($cache && !$reset) {
      $enabled = $cache;
    }
    else {
      $contexts = context_contexts(TRUE);

      foreach ($contexts as $context) {
        if (context_status($context) == CONTEXT_STATUS_ENABLED) {
          $identifier = "{$context->namespace}-{$context->attribute}-{$context->value}";
          $enabled[$identifier] = $context;
        }
      }

      // Set the cache
      context_cache_set('enabled', $enabled);
    }
    foreach ($enabled as $identifier => $context) {
      if (!isset($namespaces[$context->namespace])) {
        $namespaces[$context->namespace] = array();
      }
      $namespaces[$context->namespace][$identifier] = $context;
    }
  }

  if (!empty($namespace)) {
    return !empty($namespaces[$namespace]) ? $namespaces[$namespace] : array();
  }
  return $enabled;
}

/**
 * Loads any active contexts with associated reactions. This should be run
 * at a late stage of the page load to ensure that relevant contexts have been set.
 */
function context_active_contexts($reset = FALSE) {
  static $contexts;
  if (!isset($contexts) || $reset) {
    $contexts = array();
    $cache = context_enabled_contexts();
    foreach ($cache as $context) {
      if (context_get($context->namespace, $context->attribute) == $context->value) {
        $identifier = "{$context->namespace}-{$context->attribute}-{$context->value}";
        $contexts[$identifier] = $context;
      }
    }
    drupal_alter('context_active_contexts', $contexts);
  }
  return $contexts;
}

/**
 * Loads an associative array of conditions => context identifiers to allow
 * contexts to be set by different conditions. Called by context_set_by_condition().
 */
function context_condition_map($reset = FALSE) {
  static $condition_map;
  if (!isset($condition_map) || $reset) {
    $cache = context_cache_get('condition_map');
    if ($cache && !$reset) {
      $condition_map = $cache;
    }
    else {
      $enabled = context_enabled_contexts();
      foreach (array_keys(context_conditions()) as $condition) {
        $condition_map[$condition] = array();
        foreach ($enabled as $identifier => $context) {
          if (!empty($context->{$condition})) {
            if (is_array($context->{$condition})) {
              foreach ($context->{$condition} as $value) {
                if (!isset($condition_map[$condition][$value])) {
                  $condition_map[$condition][$value] = array();
                }
                $condition_map[$condition][$value][] = $identifier;
              }
            }
            else if (is_string($context->{$condition})) {
              $value = $context->{$condition};
              if (!isset($condition_map[$condition][$value])) {
                $condition_map[$condition][$value] = array();
              }
              $condition_map[$condition][$value][] = $identifier;
            }
          }
        }
      }
      context_cache_set('condition_map', $condition_map);
    }
  }
  return $condition_map;
}

/**
 * Builds an array of values based on the current active contexts and group
 * by conditions/reactions.
 *
 * @param $type
 *   The condition or reaction type to pull values for.
 * @param $reset
 *   Boolean value for resetting the static cache.
 *
 * @return
 *   Returns a keyed array of reactions and values.
 */
function context_active_values($type = NULL, $reset = FALSE) {
  static $value_map;
  if (!isset($value_map) || $reset) {
    $value_map = array();

    // This sucks... @TODO: fix it!!!
    $keys = array_merge(array_keys(context_reactions()), array_keys(context_conditions()));
    $keys[] = 'block';

    foreach ($keys as $key) {
      foreach (context_active_contexts() as $identifier => $context) {
        if (!empty($context->{$key})) {
          if (!isset($value_map[$key])) {
            $value_map[$key] = array();
          }
          if (is_array($context->{$key})) {
            $value_map[$key] = array_merge($value_map[$key], $context->{$key});
          }
          else {
            $value_map[$key][] = $context->{$key};
          }
        }
      }
    }
  }
  if (!empty($type)) {
    return !empty($value_map[$type]) ? $value_map[$type] : array();
  }
  return $value_map;
}

/**
 * Returns status for whether a given context definition is enabled.
 */
function context_status($context) {
  $status = variable_get('context_status', array());
  $identifier = "{$context->namespace}-{$context->attribute}-{$context->value}";
  if (isset($status[$identifier]) && !$status[$identifier]) {
    return CONTEXT_STATUS_DISABLED;
  }
  return CONTEXT_STATUS_ENABLED;
}

/**
 * Invalidates all context caches().
 */
function context_invalidate_cache() {
  cache_clear_all('context', 'cache');
}

/**
 * Invokes hook_context_conditions() to provide an array of conditions that may be associated with a context.
 */
function context_conditions($reset = FALSE) {
  static $conditions;
  if (!isset($conditions) || $reset) {
    $cache = context_cache_get('conditions');
    if ($cache && !$reset) {
      $conditions = $cache;
    }
    else {
      $conditions = module_invoke_all('context_conditions');
      context_cache_set('conditions', $conditions);
    }
  }
  return $conditions;
}

/**
 * Invokes hook_context_reactions() to provide an array of reactions that may be associated with a context.
 */
function context_reactions($reset = FALSE) {
  static $reactions;
  if (!isset($reactions) || $reset) {
    $cache = context_cache_get('reactions');
    if ($cache && !$reset) {
      $reactions = $cache;
    }
    else {
      $reactions = module_invoke_all('context_reactions');
      context_cache_set('reactions', $reactions);
    }
  }
  return $reactions;
}

/**
 * Sets a namespace-attribute-value context that has been associated with the provided condition.
 *
 * @param $type
 *   The condition type to be matched.
 * @param $id
 *   A value to match against.
 * @param $force
 *   Boolean param to force the setting of a context value even if a value for
 *   the found namespace/attribute is already set. Defaults to FALSE.
 *
 * @return
 *   True if one or more contexts were set. False if no items/contexts matched.
 */
function context_set_by_condition($type, $id, $force = FALSE) {
  $map = context_condition_map();
  $set = FALSE;
  if (!empty($map[$type]) && !empty($map[$type][$id])) {
    $contexts = context_enabled_contexts();

    $identifiers = $map[$type][$id];
    foreach ($identifiers as $identifier) {
      $context = !empty($contexts[$identifier]) ? $contexts[$identifier] : FALSE;

      if ($context) {
        // If this context already has a value, don't alter it.
        if (!context_isset($context->namespace, $context->attribute) || $force) {
          context_set($context->namespace, $context->attribute, $context->value);
          $set = TRUE;
        }
      }
    }
  }
  return $set;
}

/**
 * Recursive helper function to determine whether an array and its
 * children are entirely empty.
 */
function context_empty($element) {
  $empty = TRUE;
  if (is_array($element)) {
    foreach ($element as $child) {
      $empty = $empty && context_empty($child);
    }
  }
  else {
    $empty = $empty && empty($element);
  }
  return $empty;
}

/**
 * Export a variable.
 */
function context_var_export($var, $prefix = '', $multiple = TRUE) {
  if (is_array($var)) {
    if (empty($var)) {
      $output = 'array()';
    }
    else {
      $output = "array(\n";
      foreach ($var as $key => $value) {
        $output .= "  '$key' => ". context_var_export($value, $prefix . ($multiple? '' : '  ')) .",\n";
      }
      $output .= ')';
    }
  }
  else if (is_bool($var)) {
    $output = $var ? 'TRUE' : 'FALSE';
  }
  else {
    $output = var_export($var, TRUE);
  }

  if ($prefix) {
    $output = str_replace("\n", "\n$prefix", $output);
  }

  return $output;
}