<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * This class represent one XMLDB table
 *
 * @package    core_xmldb
 * @copyright  1999 onwards Martin Dougiamas     http://dougiamas.com
 *             2001-3001 Eloy Lafuente (stronk7) http://contiento.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();


class xmldb_table extends xmldb_object {

    /** @var xmldb_field[] table columns */
    protected $fields;

    /** @var xmldb_key[] keys */
    protected $keys;

    /** @var xmldb_index[] indexes */
    protected $indexes;

    /** @var int max length of table name prefixes */
    const PREFIX_MAX_LENGTH = 10;

    /**
     * Note:
     *  - PostgreSQL has a limit of 63 ascii chars (bytes) for table names. Others have greater limits.
     *    Up to PREFIX_MAX_LENGTH ascii chars (bytes) are reserved for table prefixes.
     *
     * @var int max length of table names (without prefix).
     */
    const NAME_MAX_LENGTH = 63 - self::PREFIX_MAX_LENGTH;

    /**
     * Creates one new xmldb_table
     * @param string $name
     */
    public function __construct($name) {
        parent::__construct($name);
        $this->fields = array();
        $this->keys = array();
        $this->indexes = array();
    }

    /**
     * Add one field to the table, allowing to specify the desired  order
     * If it's not specified, then the field is added at the end
     * @param xmldb_field $field
     * @param xmldb_object $after
     * @return xmldb_field
     */
    public function addField($field, $after=null) {

        // Detect duplicates first
        if ($this->getField($field->getName())) {
            throw new coding_exception('Duplicate field '.$field->getName().' specified in table '.$this->getName());
        }

        // Calculate the previous and next fields
        $prevfield = null;
        $nextfield = null;

        if (!$after) {
            $allfields = $this->getFields();
            if (!empty($allfields)) {
                end($allfields);
                $prevfield = $allfields[key($allfields)];
            }
        } else {
            $prevfield = $this->getField($after);
        }
        if ($prevfield && $prevfield->getNext()) {
            $nextfield = $this->getField($prevfield->getNext());
        }

        // Set current field previous and next attributes
        if ($prevfield) {
            $field->setPrevious($prevfield->getName());
            $prevfield->setNext($field->getName());
        }
        if ($nextfield) {
            $field->setNext($nextfield->getName());
            $nextfield->setPrevious($field->getName());
        }
        // Some more attributes
        $field->setLoaded(true);
        $field->setChanged(true);
        // Add the new field
        $this->fields[] = $field;
        // Reorder the field
        $this->orderFields($this->fields);
        // Recalculate the hash
        $this->calculateHash(true);
        // We have one new field, so the table has changed
        $this->setChanged(true);

        return $field;
    }

    /**
     * Add one key to the table, allowing to specify the desired  order
     * If it's not specified, then the key is added at the end
     * @param xmldb_key $key
     * @param xmldb_object $after
     */
    public function addKey($key, $after=null) {

        // Detect duplicates first
        if ($this->getKey($key->getName())) {
            throw new coding_exception('Duplicate key '.$key->getName().' specified in table '.$this->getName());
        }

        // Make sure there are no indexes with the key column specs because they would collide.
        $newfields = $key->getFields();
        $allindexes = $this->getIndexes();
        foreach ($allindexes as $index) {
            $fields = $index->getFields();
            if ($fields === $newfields) {
                throw new coding_exception('Index '.$index->getName().' collides with key'.$key->getName().' specified in table '.$this->getName());
            }
        }

        // Calculate the previous and next keys
        $prevkey = null;
        $nextkey = null;

        if (!$after) {
            $allkeys = $this->getKeys();
            if (!empty($allkeys)) {
                end($allkeys);
                $prevkey = $allkeys[key($allkeys)];
            }
        } else {
            $prevkey = $this->getKey($after);
        }
        if ($prevkey && $prevkey->getNext()) {
            $nextkey = $this->getKey($prevkey->getNext());
        }

        // Set current key previous and next attributes
        if ($prevkey) {
            $key->setPrevious($prevkey->getName());
            $prevkey->setNext($key->getName());
        }
        if ($nextkey) {
            $key->setNext($nextkey->getName());
            $nextkey->setPrevious($key->getName());
        }
        // Some more attributes
        $key->setLoaded(true);
        $key->setChanged(true);
        // Add the new key
        $this->keys[] = $key;
        // Reorder the keys
        $this->orderKeys($this->keys);
        // Recalculate the hash
        $this->calculateHash(true);
        // We have one new field, so the table has changed
        $this->setChanged(true);
    }

    /**
     * Add one index to the table, allowing to specify the desired  order
     * If it's not specified, then the index is added at the end
     * @param xmldb_index $index
     * @param xmldb_object $after
     */
    public function addIndex($index, $after=null) {

        // Detect duplicates first
        if ($this->getIndex($index->getName())) {
            throw new coding_exception('Duplicate index '.$index->getName().' specified in table '.$this->getName());
        }

        // Make sure there are no keys with the index column specs because they would collide.
        $newfields = $index->getFields();
        $allkeys = $this->getKeys();
        foreach ($allkeys as $key) {
            $fields = $key->getFields();
            if ($fields === $newfields) {
                throw new coding_exception('Key '.$key->getName().' collides with index'.$index->getName().' specified in table '.$this->getName());
            }
        }

        // Calculate the previous and next indexes
        $previndex = null;
        $nextindex = null;

        if (!$after) {
            $allindexes = $this->getIndexes();
            if (!empty($allindexes)) {
                end($allindexes);
                $previndex = $allindexes[key($allindexes)];
            }
        } else {
            $previndex = $this->getIndex($after);
        }
        if ($previndex && $previndex->getNext()) {
            $nextindex = $this->getIndex($previndex->getNext());
        }

        // Set current index previous and next attributes
        if ($previndex) {
            $index->setPrevious($previndex->getName());
            $previndex->setNext($index->getName());
        }
        if ($nextindex) {
            $index->setNext($nextindex->getName());
            $nextindex->setPrevious($index->getName());
        }

        // Some more attributes
        $index->setLoaded(true);
        $index->setChanged(true);
        // Add the new index
        $this->indexes[] = $index;
        // Reorder the indexes
        $this->orderIndexes($this->indexes);
        // Recalculate the hash
        $this->calculateHash(true);
        // We have one new index, so the table has changed
        $this->setChanged(true);
    }

    /**
     * This function will return the array of fields in the table
     * @return xmldb_field[]
     */
    public function getFields() {
        return $this->fields;
    }

    /**
     * This function will return the array of keys in the table
     * @return xmldb_key[]
     */
    public function getKeys() {
        return $this->keys;
    }

    /**
     * This function will return the array of indexes in the table
     * @return xmldb_index[]
     */
    public function getIndexes() {
        return $this->indexes;
    }

    /**
     * Returns one xmldb_field
     * @param string $fieldname
     * @return xmldb_field|null
     */
    public function getField($fieldname) {
        $i = $this->findFieldInArray($fieldname);
        if ($i !== null) {
            return $this->fields[$i];
        }
        return null;
    }

    /**
     * Returns the position of one field in the array.
     * @param string $fieldname
     * @return int|null index of the field, or null if not found.
     */
    public function findFieldInArray($fieldname) {
        foreach ($this->fields as $i => $field) {
            if ($fieldname == $field->getName()) {
                return $i;
            }
        }
        return null;
    }

    /**
     * This function will reorder the array of fields
     * @return bool whether the reordering succeeded.
     */
    public function orderFields() {
        $result = $this->orderElements($this->fields);
        if ($result) {
            $this->setFields($result);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Returns one xmldb_key
     * @param string $keyname
     * @return xmldb_key|null
     */
    public function getKey($keyname) {
        $i = $this->findKeyInArray($keyname);
        if ($i !== null) {
            return $this->keys[$i];
        }
        return null;
    }

    /**
     * Returns the position of one key in the array.
     * @param string $keyname
     * @return int|null index of the key, or null if not found.
     */
    public function findKeyInArray($keyname) {
        foreach ($this->keys as $i => $key) {
            if ($keyname == $key->getName()) {
                return $i;
            }
        }
        return null;
    }

    /**
     * This function will reorder the array of keys
     * @return bool whether the reordering succeeded.
     */
    public function orderKeys() {
        $result = $this->orderElements($this->keys);
        if ($result) {
            $this->setKeys($result);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Returns one xmldb_index
     * @param string $indexname
     * @return xmldb_index|null
     */
    public function getIndex($indexname) {
        $i = $this->findIndexInArray($indexname);
        if ($i !== null) {
            return $this->indexes[$i];
        }
        return null;
    }

    /**
     * Returns the position of one index in the array.
     * @param string $indexname
     * @return int|null index of the index, or null if not found.
     */
    public function findIndexInArray($indexname) {
        foreach ($this->indexes as $i => $index) {
            if ($indexname == $index->getName()) {
                return $i;
            }
        }
        return null;
    }

    /**
     * This function will reorder the array of indexes
     * @return bool whether the reordering succeeded.
     */
    public function orderIndexes() {
        $result = $this->orderElements($this->indexes);
        if ($result) {
            $this->setIndexes($result);
            return true;
        } else {
            return false;
        }
    }

    /**
     * This function will set the array of fields in the table
     * @param xmldb_field[] $fields
     */
    public function setFields($fields) {
        $this->fields = $fields;
    }

    /**
     * This function will set the array of keys in the table
     * @param xmldb_key[] $keys
     */
    public function setKeys($keys) {
        $this->keys = $keys;
    }

    /**
     * This function will set the array of indexes in the table
     * @param xmldb_index[] $indexes
     */
    public function setIndexes($indexes) {
        $this->indexes = $indexes;
    }

    /**
     * Delete one field from the table
     * @param string $fieldname
     */
    public function deleteField($fieldname) {

        $field = $this->getField($fieldname);
        if ($field) {
            $i = $this->findFieldInArray($fieldname);
            // Look for prev and next field
            $prevfield = $this->getField($field->getPrevious());
            $nextfield = $this->getField($field->getNext());
            // Change their previous and next attributes
            if ($prevfield) {
                $prevfield->setNext($field->getNext());
            }
            if ($nextfield) {
                $nextfield->setPrevious($field->getPrevious());
            }
            // Delete the field
            unset($this->fields[$i]);
            // Reorder the whole structure
            $this->orderFields($this->fields);
            // Recalculate the hash
            $this->calculateHash(true);
            // We have one deleted field, so the table has changed
            $this->setChanged(true);
        }
    }

    /**
     * Delete one key from the table
     * @param string $keyname
     */
    public function deleteKey($keyname) {

        $key = $this->getKey($keyname);
        if ($key) {
            $i = $this->findKeyInArray($keyname);
            // Look for prev and next key
            $prevkey = $this->getKey($key->getPrevious());
            $nextkey = $this->getKey($key->getNext());
            // Change their previous and next attributes
            if ($prevkey) {
                $prevkey->setNext($key->getNext());
            }
            if ($nextkey) {
                $nextkey->setPrevious($key->getPrevious());
            }
            // Delete the key
            unset($this->keys[$i]);
            // Reorder the Keys
            $this->orderKeys($this->keys);
            // Recalculate the hash
            $this->calculateHash(true);
            // We have one deleted key, so the table has changed
            $this->setChanged(true);
        }
    }

    /**
     * Delete one index from the table
     * @param string $indexname
     */
    public function deleteIndex($indexname) {

        $index = $this->getIndex($indexname);
        if ($index) {
            $i = $this->findIndexInArray($indexname);
            // Look for prev and next index
            $previndex = $this->getIndex($index->getPrevious());
            $nextindex = $this->getIndex($index->getNext());
            // Change their previous and next attributes
            if ($previndex) {
                $previndex->setNext($index->getNext());
            }
            if ($nextindex) {
                $nextindex->setPrevious($index->getPrevious());
            }
            // Delete the index
            unset($this->indexes[$i]);
            // Reorder the indexes
            $this->orderIndexes($this->indexes);
            // Recalculate the hash
            $this->calculateHash(true);
            // We have one deleted index, so the table has changed
            $this->setChanged(true);
        }
    }

    /**
     * Load data from XML to the table
     * @param array $xmlarr
     * @return bool success
     */
    public function arr2xmldb_table($xmlarr) {

        global $CFG;

        $result = true;

        // Debug the table
        // traverse_xmlize($xmlarr);                   //Debug
        // print_object ($GLOBALS['traverse_array']);  //Debug
        // $GLOBALS['traverse_array']="";              //Debug

        // Process table attributes (name, comment, previoustable and nexttable)
        if (isset($xmlarr['@']['NAME'])) {
            $this->name = trim($xmlarr['@']['NAME']);
        } else {
            $this->errormsg = 'Missing NAME attribute';
            $this->debug($this->errormsg);
            $result = false;
        }
        if (isset($xmlarr['@']['COMMENT'])) {
            $this->comment = trim($xmlarr['@']['COMMENT']);
        } else if (!empty($CFG->xmldbdisablecommentchecking)) {
            $this->comment = '';
        } else {
            $this->errormsg = 'Missing COMMENT attribute';
            $this->debug($this->errormsg);
            $result = false;
        }

        // Iterate over fields
        if (isset($xmlarr['#']['FIELDS']['0']['#']['FIELD'])) {
            foreach ($xmlarr['#']['FIELDS']['0']['#']['FIELD'] as $xmlfield) {
                if (!$result) { //Skip on error
                    continue;
                }
                $name = trim($xmlfield['@']['NAME']);
                $field = new xmldb_field($name);
                $field->arr2xmldb_field($xmlfield);
                $this->fields[] = $field;
                if (!$field->isLoaded()) {
                    $this->errormsg = 'Problem loading field ' . $name;
                    $this->debug($this->errormsg);
                    $result = false;
                }
            }
        } else {
            $this->errormsg = 'Missing FIELDS section';
            $this->debug($this->errormsg);
            $result = false;
        }

        // Perform some general checks over fields
        if ($result && $this->fields) {
            // Check field names are ok (lowercase, a-z _-)
            if (!$this->checkNameValues($this->fields)) {
                $this->errormsg = 'Some FIELDS name values are incorrect';
                $this->debug($this->errormsg);
                $result = false;
            }
            // Compute prev/next.
            $this->fixPrevNext($this->fields);
            // Order fields
            if ($result && !$this->orderFields($this->fields)) {
                $this->errormsg = 'Error ordering the fields';
                $this->debug($this->errormsg);
                $result = false;
            }
        }

        // Iterate over keys
        if (isset($xmlarr['#']['KEYS']['0']['#']['KEY'])) {
            foreach ($xmlarr['#']['KEYS']['0']['#']['KEY'] as $xmlkey) {
                if (!$result) { //Skip on error
                    continue;
                }
                $name = trim($xmlkey['@']['NAME']);
                $key = new xmldb_key($name);
                $key->arr2xmldb_key($xmlkey);
                $this->keys[] = $key;
                if (!$key->isLoaded()) {
                    $this->errormsg = 'Problem loading key ' . $name;
                    $this->debug($this->errormsg);
                    $result = false;
                }
            }
        } else {
            $this->errormsg = 'Missing KEYS section (at least one PK must exist)';
            $this->debug($this->errormsg);
            $result = false;
        }

        // Perform some general checks over keys
        if ($result && $this->keys) {
            // Check keys names are ok (lowercase, a-z _-)
            if (!$this->checkNameValues($this->keys)) {
                $this->errormsg = 'Some KEYS name values are incorrect';
                $this->debug($this->errormsg);
                $result = false;
            }
            // Compute prev/next.
            $this->fixPrevNext($this->keys);
            // Order keys
            if ($result && !$this->orderKeys($this->keys)) {
                $this->errormsg = 'Error ordering the keys';
                $this->debug($this->errormsg);
                $result = false;
            }
            // TODO: Only one PK
            // TODO: Not keys with repeated fields
            // TODO: Check fields and reffieds exist in table
        }

        // Iterate over indexes
        if (isset($xmlarr['#']['INDEXES']['0']['#']['INDEX'])) {
            foreach ($xmlarr['#']['INDEXES']['0']['#']['INDEX'] as $xmlindex) {
                if (!$result) { //Skip on error
                    continue;
                }
                $name = trim($xmlindex['@']['NAME']);
                $index = new xmldb_index($name);
                $index->arr2xmldb_index($xmlindex);
                $this->indexes[] = $index;
                if (!$index->isLoaded()) {
                    $this->errormsg = 'Problem loading index ' . $name;
                    $this->debug($this->errormsg);
                    $result = false;
                }
            }
        }

        // Perform some general checks over indexes
        if ($result && $this->indexes) {
            // Check field names are ok (lowercase, a-z _-)
            if (!$this->checkNameValues($this->indexes)) {
                $this->errormsg = 'Some INDEXES name values are incorrect';
                $this->debug($this->errormsg);
                $result = false;
            }
            // Compute prev/next.
            $this->fixPrevNext($this->indexes);
            // Order indexes
            if ($result && !$this->orderIndexes($this->indexes)) {
                $this->errormsg = 'Error ordering the indexes';
                $this->debug($this->errormsg);
                $result = false;
            }
            // TODO: Not indexes with repeated fields
            // TODO: Check fields exist in table
        }

        // Set some attributes
        if ($result) {
            $this->loaded = true;
        }
        $this->calculateHash();
        return $result;
    }

    /**
     * This function calculate and set the hash of one xmldb_table
     * @param bool $recursive
     */
     public function calculateHash($recursive = false) {
        if (!$this->loaded) {
            $this->hash = null;
        } else {
            $key = $this->name . $this->comment;
            if ($this->fields) {
                foreach ($this->fields as $fie) {
                    $field = $this->getField($fie->getName());
                    if ($recursive) {
                        $field->calculateHash($recursive);
                    }
                    $key .= $field->getHash();
                }
            }
            if ($this->keys) {
                foreach ($this->keys as $ke) {
                    $k = $this->getKey($ke->getName());
                    if ($recursive) {
                        $k->calculateHash($recursive);
                    }
                    $key .= $k->getHash();
                }
            }
            if ($this->indexes) {
                foreach ($this->indexes as $in) {
                    $index = $this->getIndex($in->getName());
                    if ($recursive) {
                        $index->calculateHash($recursive);
                    }
                    $key .= $index->getHash();
                }
            }
            $this->hash = md5($key);
        }
    }

    /**
     * Validates the table restrictions (does not validate child elements).
     *
     * The error message should not be localised because it is intended for developers,
     * end users and admins should never see these problems!
     *
     * @param xmldb_table $xmldb_table optional when object is table
     * @return string null if ok, error message if problem found
     */
    public function validateDefinition(?xmldb_table $xmldb_table=null) {
        // table parameter is ignored
        $name = $this->getName();
        if (strlen($name) > self::NAME_MAX_LENGTH) {
            return 'Invalid table name {'.$name.'}: name is too long. Limit is '.self::NAME_MAX_LENGTH.' chars.';
        }
        if (!preg_match('/^[a-z][a-z0-9_]*$/', $name)) {
            return 'Invalid table name {'.$name.'}: name includes invalid characters.';
        }

        return null;
    }

    /**
     * This function will output the XML text for one table
     * @return string
     */
    public function xmlOutput() {
        $o = '';
        $o.= '    <TABLE NAME="' . $this->name . '"';
        if ($this->comment) {
            $o.= ' COMMENT="' . htmlspecialchars($this->comment, ENT_COMPAT) . '"';
        }
        $o.= '>' . "\n";
        // Now the fields
        if ($this->fields) {
            $o.= '      <FIELDS>' . "\n";
            foreach ($this->fields as $field) {
                $o.= $field->xmlOutput();
            }
            $o.= '      </FIELDS>' . "\n";
        }
        // Now the keys
        if ($this->keys) {
            $o.= '      <KEYS>' . "\n";
            foreach ($this->keys as $key) {
                $o.= $key->xmlOutput();
            }
            $o.= '      </KEYS>' . "\n";
        }
        // Now the indexes
        if ($this->indexes) {
            $o.= '      <INDEXES>' . "\n";
            foreach ($this->indexes as $index) {
                $o.= $index->xmlOutput();
            }
            $o.= '      </INDEXES>' . "\n";
        }
        $o.= '    </TABLE>' . "\n";

        return $o;
    }

    /**
     * This function will add one new field to the table with all
     * its attributes defined
     *
     * @param string $name name of the field
     * @param int $type XMLDB_TYPE_INTEGER, XMLDB_TYPE_NUMBER, XMLDB_TYPE_CHAR, XMLDB_TYPE_TEXT, XMLDB_TYPE_BINARY
     * @param string $precision length for integers and chars, two-comma separated numbers for numbers
     * @param bool $unsigned XMLDB_UNSIGNED or null (or false)
     * @param bool $notnull XMLDB_NOTNULL or null (or false)
     * @param bool $sequence XMLDB_SEQUENCE or null (or false)
     * @param mixed $default meaningful default o null (or false)
     * @param xmldb_object $previous name of the previous field in the table or null (or false)
     * @return xmlddb_field
     */
    public function add_field($name, $type, $precision=null, $unsigned=null, $notnull=null, $sequence=null, $default=null, $previous=null) {
        $field = new xmldb_field($name, $type, $precision, $unsigned, $notnull, $sequence, $default);
        $this->addField($field, $previous);

        return $field;
    }

    /**
     * This function will add one new key to the table with all
     * its attributes defined
     *
     * @param string $name name of the key
     * @param int $type XMLDB_KEY_PRIMARY, XMLDB_KEY_UNIQUE, XMLDB_KEY_FOREIGN
     * @param array $fields an array of fieldnames to build the key over
     * @param string $reftable name of the table the FK points to or null
     * @param array $reffields an array of fieldnames in the FK table or null
     */
    public function add_key($name, $type, $fields, $reftable=null, $reffields=null) {
        $key = new xmldb_key($name, $type, $fields, $reftable, $reffields);
        $this->addKey($key);
    }

    /**
     * This function will add one new index to the table with all
     * its attributes defined
     *
     * @param string $name name of the index
     * @param int $type XMLDB_INDEX_UNIQUE, XMLDB_INDEX_NOTUNIQUE
     * @param array $fields an array of fieldnames to build the index over
     * @param array $hints optional index type hints
     */
    public function add_index($name, $type, $fields, $hints = array()) {
        $index = new xmldb_index($name, $type, $fields, $hints);
        $this->addIndex($index);
    }

    /**
     * This function will return all the errors found in one table
     * looking recursively inside each field/key/index. Returns
     * an array of errors or false
     */
    public function getAllErrors() {

        $errors = array();
        // First the table itself
        if ($this->getError()) {
            $errors[] = $this->getError();
        }
        // Delegate to fields
        if ($fields = $this->getFields()) {
            foreach ($fields as $field) {
                if ($field->getError()) {
                    $errors[] = $field->getError();
                }
            }
        }
        // Delegate to keys
        if ($keys = $this->getKeys()) {
            foreach ($keys as $key) {
                if ($key->getError()) {
                    $errors[] = $key->getError();
                }
            }
        }
        // Delegate to indexes
        if ($indexes = $this->getIndexes()) {
            foreach ($indexes as $index) {
                if ($index->getError()) {
                    $errors[] = $index->getError();
                }
            }
        }
        // Return decision
        if (count($errors)) {
            return $errors;
        } else {
            return false;
        }
    }
}
