<?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/>.

declare(strict_types=1);

namespace core_reportbuilder\local\report;

use coding_exception;
use lang_string;
use core_reportbuilder\local\helpers\database;

/**
 * Class to represent a report column
 *
 * @package     core_reportbuilder
 * @copyright   2020 Paul Holden <paulh@moodle.com>
 * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
final class column {

    /** @var int Column type is integer */
    public const TYPE_INTEGER = 1;

    /** @var int Column type is text */
    public const TYPE_TEXT = 2;

    /** @var int Column type is timestamp */
    public const TYPE_TIMESTAMP = 3;

    /** @var int Column type is boolean */
    public const TYPE_BOOLEAN = 4;

    /** @var int Column type is float */
    public const TYPE_FLOAT = 5;

    /** @var int Column type is long text */
    public const TYPE_LONGTEXT = 6;

    /** @var int $index Column index within a report */
    private $index;

    /** @var string $columnname Internal reference to name of column */
    private $columnname;

    /** @var lang_string $columntitle Used as a title for the column in reports */
    private $columntitle;

    /** @var string $entityname Name of the entity this column belongs to */
    private $entityname;

    /** @var int $type Column data type (one of the TYPE_* class constants) */
    private $type = null;

    /** @var string[] $joins List of SQL joins for this column */
    private $joins = [];

    /** @var array $fields */
    private $fields = [];

    /** @var array $params  */
    private $params = [];

    /** @var array[] $callbacks Array of [callable, additionalarguments] */
    private $callbacks = [];

    /** @var bool $issortable Used to indicate if a column is sortable */
    private $issortable = false;

    /** @var array $attributes */
    private $attributes = [];

    /** @var bool $available Used to know if column is available to the current user or not */
    protected $available = true;

    /**
     * Column constructor
     *
     * For better readability use chainable methods, for example:
     *
     * $report->add_column(
     *    (new column('name', new lang_string('name'), 'user'))
     *    ->add_join('left join {table} t on t.id = p.tableid')
     *    ->add_field('t.name')
     *    ->add_callback([format::class, 'format_string']));
     *
     * @param string $name Internal name of the column
     * @param lang_string|null $title Title of the column used in reports (null for blank)
     * @param string $entityname Name of the entity this column belongs to. Typically when creating columns within entities
     *      this value should be the result of calling {@see get_entity_name}, however if creating columns inside reports directly
     *      it should be the name of the entity as passed to {@see \core_reportbuilder\local\report\base::annotate_entity}
     */
    public function __construct(string $name, ?lang_string $title, string $entityname) {
        $this->columnname = $name;
        $this->columntitle = $title;
        $this->entityname = $entityname;
    }

    /**
     * Set column name
     *
     * @param string $name
     * @return self
     */
    public function set_name(string $name): self {
        $this->columnname = $name;
        return $this;
    }

    /**
     * Return column name
     *
     * @return mixed
     */
    public function get_name(): string {
        return $this->columnname;
    }

    /**
     * Set column title
     *
     * @param lang_string|null $title
     * @return self
     */
    public function set_title(?lang_string $title): self {
        $this->columntitle = $title;
        return $this;
    }

    /**
     * Return column title
     *
     * @return string
     */
    public function get_title(): string {
        return $this->columntitle ? (string) $this->columntitle : '';
    }

    /**
     * Get column entity name
     *
     * @return string
     */
    public function get_entity_name(): string {
        return $this->entityname;
    }


    /**
     * Return unique identifier for this column
     *
     * @return string
     */
    public function get_unique_identifier(): string {
        return $this->get_entity_name() . ':' . $this->get_name();
    }

    /**
     * Set the column index within the current report
     *
     * @param int $index
     * @return column
     */
    public function set_index(int $index): self {
        $this->index = $index;
        return $this;
    }

    /**
     * Set the column type
     *
     * @param int $type
     * @return column
     * @throws coding_exception
     */
    public function set_type(int $type): self {
        $allowedtypes = [
            self::TYPE_INTEGER,
            self::TYPE_TEXT,
            self::TYPE_TIMESTAMP,
            self::TYPE_BOOLEAN,
            self::TYPE_FLOAT,
            self::TYPE_LONGTEXT,
        ];
        if (!in_array($type, $allowedtypes)) {
            throw new coding_exception('Invalid column type', $type);
        }

        $this->type = $type;
        return $this;
    }

    /**
     * Return column type
     *
     * @return int|null
     */
    public function get_type(): ?int {
        return $this->type;
    }

    /**
     * Add join clause required for this column to join to existing tables/entities
     *
     * This is necessary in the case where {@see add_field} is selecting data from a table that isn't otherwise queried
     *
     * @param string $join
     * @return self
     */
    public function add_join(string $join): self {
        $this->joins[trim($join)] = trim($join);
        return $this;
    }

    /**
     * Add multiple join clauses required for this column, passing each to {@see add_join}
     *
     * Typically when defining columns in entities, you should pass {@see \core_reportbuilder\local\report\base::get_joins} to
     * this method, so that all entity joins are included in the report when your column is added to it
     *
     * @param string[] $joins
     * @return self
     */
    public function add_joins(array $joins): self {
        foreach ($joins as $join) {
            $this->add_join($join);
        }
        return $this;
    }

    /**
     * Return column joins
     *
     * @return string[]
     */
    public function get_joins(): array {
        return array_values($this->joins);
    }

    /**
     * Adds a field to be queried from the database that is necessary for this column
     *
     * Multiple fields can be added per column, this method may be called several times. Field aliases must be unique inside
     * any given column, but there will be no conflicts if the same aliases are used in other columns in the same report
     *
     * @param string $sql SQL query, this may be a simple "tablealias.fieldname" or a complex sub-query that returns only one field
     * @param string $alias
     * @param array $params
     * @return self
     * @throws coding_exception
     */
    public function add_field(string $sql, string $alias = '', array $params = []): self {
        database::validate_params($params);

        // SQL ends with a space and a word - this looks like an alias was passed as part of the field.
        if (preg_match('/ \w+$/', $sql) && empty($alias)) {
            throw new coding_exception('Column alias must be passed as a separate argument', $sql);
        }

        // If no alias was specified, auto-detect it based on common patterns ("table.column" or just "column").
        if (empty($alias) && preg_match('/^(\w+\.)?(?<fieldname>\w+)$/', $sql, $matches)) {
            $alias = $matches['fieldname'];
        }

        if (empty($alias)) {
            throw new coding_exception('Complex columns must have an alias', $sql);
        }

        $this->fields[$alias] = $sql;
        $this->params += $params;

        return $this;
    }

    /**
     * Add a list of comma-separated fields
     *
     * @param string $sql
     * @param array $params
     * @return self
     */
    public function add_fields(string $sql, array $params = []): self {
        database::validate_params($params);

        // Split SQL into separate fields (separated by comma).
        $fields = preg_split('/\s*,\s*/', $sql);
        foreach ($fields as $field) {
            // Split each field into expression, <field> <as> <alias> where "as" and "alias" are optional.
            $fieldparts = preg_split('/\s+/', $field);

            if (count($fieldparts) == 2 || (count($fieldparts) == 3 && strtolower($fieldparts[1]) === 'as')) {
                $sql = reset($fieldparts);
                $alias = array_pop($fieldparts);
                $this->add_field($sql, $alias);
            } else {
                $this->add_field($field);
            }
        }

        $this->params += $params;

        return $this;
    }

    /**
     * Given a param name, add a unique prefix to ensure that the same column with params can be added multiple times to a report
     *
     * @param string $name
     * @return string
     */
    private function unique_param_name(string $name): string {
        return "p{$this->index}_{$name}";
    }

    /**
     * Helper method to take all fields added to the column, and return appropriate SQL and alias
     *
     * @return array[]
     */
    private function get_fields_sql_alias(): array {
        $fields = [];

        foreach ($this->fields as $alias => $sql) {
            // Ensure params within SQL are prefixed with column index.
            foreach ($this->params as $name => $value) {
                $sql = preg_replace_callback('/:(?<param>' . preg_quote($name, '\b/') . ')/', function(array $matches): string {
                    return ':' . $this->unique_param_name($matches['param']);
                }, $sql);
            }

            $fields[$alias] = [
                'sql' => $sql,
                'alias' => substr("c{$this->index}_{$alias}", 0, 30),
            ];
        }

        return $fields;
    }

    /**
     * Return array of SQL expressions for each field of this column
     *
     * @return array
     */
    public function get_fields(): array {
        $fields = array_map(static function(array $field): string {
            return "{$field['sql']} AS {$field['alias']}";
        }, $this->get_fields_sql_alias());

        return array_values($fields);
    }

    /**
     * Return column parameters, prefixed by the current index to allow the column to be added multiple times to a report
     *
     * @return array
     */
    public function get_params(): array {
        $params = [];

        foreach ($this->params as $name => $value) {
            $paramname = $this->unique_param_name($name);
            $params[$paramname] = $value;
        }

        return $params;
    }

    /**
     * Return an alias for this column (the generated alias of it's first field)
     *
     * @return string
     * @throws coding_exception
     */
    public function get_column_alias(): string {
        if (!$fields = $this->get_fields_sql_alias()) {
            throw new coding_exception('Column ' . $this->get_unique_identifier() . ' contains no fields');
        }

        return reset($fields)['alias'];
    }

    /**
     * Adds column callback (in the case there are multiple, they will be applied one after another)
     *
     * The callback should implement the following signature (where $value is the first column field, $row is all column
     * fields, and $additionalarguments are those passed on from this method):
     *
     * function($value, stdClass $row[, $additionalarguments]): string
     *
     * @param callable $callable function that takes arguments ($value, \stdClass $row, $additionalarguments)
     * @param mixed $additionalarguments
     * @return self
     */
    public function add_callback(callable $callable, $additionalarguments = null): self {
        $this->callbacks[] = [$callable, $additionalarguments];
        return $this;
    }

    /**
     * Sets column callback. This will overwrite any previously added callbacks {@see add_callback}
     *
     * @param callable $callable
     * @param mixed $additionalarguments
     * @return self
     */
    public function set_callback(callable $callable, $additionalarguments = null): self {
        $this->callbacks = [];
        return $this->add_callback($callable, $additionalarguments);
    }

    /**
     * Sets the column as sortable
     *
     * @param bool $issortable
     * @return self
     */
    public function set_is_sortable(bool $issortable): self {
        $this->issortable = $issortable;
        return $this;
    }

    /**
     * Return sortable status of column
     *
     * @return bool
     */
    public function get_is_sortable(): bool {
        return $this->issortable;
    }

    /**
     * Extract all values from given row for this column
     *
     * @param array $row
     * @return array
     */
    private function get_values(array $row): array {
        $values = [];

        foreach ($this->get_fields_sql_alias() as $alias => $field) {
            $values[$alias] = $row[$field['alias']];
        }

        return $values;
    }

    /**
     * Return the default column value, that being the value of it's first field
     *
     * @param array $values
     * @return mixed
     */
    private function get_default_value(array $values) {
        $value = reset($values);

        // Ensure default value is cast to it's strict type.
        switch ($this->get_type()) {
            case self::TYPE_INTEGER:
            case self::TYPE_TIMESTAMP:
                $value = (int) $value;
                break;
            case self::TYPE_FLOAT:
                $value = (float) $value;
                break;
            case self::TYPE_BOOLEAN:
                $value = (bool) $value;
                break;
        }

        return $value;
    }

    /**
     * Return column value based on complete table row
     *
     * @param array $row
     * @return mixed
     */
    public function format_value(array $row) {
        $values = $this->get_values($row);
        $value = $this->get_default_value($values);

        // Loop through, and apply any defined callbacks.
        foreach ($this->callbacks as $callback) {
            $value = ($callback[0])($value, (object) $values, $callback[1]);
        }

        return $value;
    }

    /**
     * Add column attributes (data-, class, etc.) that will be included in HTML when column is displayed
     *
     * @param array $attributes
     * @return self
     */
    public function add_attributes(array $attributes): self {
        $this->attributes = $attributes + $this->attributes;
        return $this;
    }

    /**
     * Returns the column HTML attributes
     *
     * @return array
     */
    public function get_attributes(): array {
        return $this->attributes;
    }

    /**
     * Return available state of the column for the current user. For instance the column may be added to a report with the
     * expectation that only some users are able to see it
     *
     * @return bool
     */
    public function get_is_available(): bool {
        return $this->available;
    }

    /**
     * Conditionally set whether the column is available.
     *
     * @param bool $available
     * @return self
     */
    public function set_is_available(bool $available): self {
        $this->available = $available;
        return $this;
    }
}