<?php

namespace Kanboard\Plugin\QualKard\Helper;

use Kanboard\Core\Base;
use Kanboard\Model\TaskModel;

/**
 * QualKard helper: the qualcard grading math (ported from Ruben's C program) plus the per-board gates.
 *
 * Scores per grade column: hairy=0.0, hard=1.3, medium=3.0, easy=5.0. The running average is
 * M1 = (M0 + N)/2, with a new (unread) card seeded at N - 23%. The average maps to a review interval
 * (qualcard grades G..A, 1..11 days). qualcard's H/same-day and the overdue decay are intentionally
 * NOT ported: there is no "again now", and the Study column is itself the overdue backlog.
 */
class QualKardHelper extends Base
{
    const SCORE = array('hairy' => 0.0, 'hard' => 1.3, 'medium' => 3.0, 'easy' => 5.0);

    // Stored qualkard_avg value for an unread card. A literal, non-empty marker: it survives PHP's
    // empty() -- which drops the numeric string "0" on save -- and stays distinct from a real average
    // of 0 (a card graded hairy from new). Graded averages are stored with decimals for the same reason.
    const UNREAD = 'new';

    /**
     * Running average. New card (unread, $old === null) seeds at N - 23%; otherwise the qualcard mean.
     */
    public static function nextAverage($old, $score)
    {
        return $old === null ? ($score - 0.23 * $score) : (($old + $score) / 2.0);
    }

    /**
     * Average -> review interval in days (qualcard grades G..A).
     */
    public static function intervalDays($avg)
    {
        if ($avg <= 0.60) {
            return 1; // G
        }
        if ($avg <= 1.35) {
            return 2; // F
        }
        if ($avg <= 2.20) {
            return 3; // E
        }
        if ($avg <= 3.05) {
            return 5; // D
        }
        if ($avg <= 3.90) {
            return 7; // C
        }
        if ($avg <= 4.92) {
            return 9; // B
        }

        return 11; // A
    }

    /**
     * Next due timestamp: midnight, intervalDays() out.
     */
    public static function dueFrom($avg, $now = null)
    {
        $now = $now ?: time();

        return strtotime('+'.self::intervalDays($avg).' days', strtotime('today', $now));
    }

    /**
     * Mastery badge for a card's average: label + CSS class. null (unread) = "new" (yellow); otherwise
     * a percent of 5, coloured red (<50) / green (<90) / blue (>=90).
     *
     * @param  float|null $avg
     * @return array{label:string,class:string}
     */
    public static function badge($avg)
    {
        if ($avg === null) {
            return array('label' => t('new'), 'class' => 'qk-new');
        }

        $pct = (int) round($avg / 5.0 * 100);
        $class = $pct < 50 ? 'qk-low' : ($pct < 90 ? 'qk-mid' : 'qk-high');

        return array('label' => $pct.'%', 'class' => $class);
    }

    /**
     * A stored qualkard_avg -> float, or null when the card is unread. The unread marker is the
     * literal self::UNREAD; '' and null are also treated as unread for any card written before it.
     *
     * @param  string|null $raw
     * @return float|null
     */
    private static function parseAvg($raw)
    {
        return ($raw === '' || $raw === null || $raw === self::UNREAD) ? null : (float) $raw;
    }

    /**
     * Is QualKard enabled for this board?
     *
     * @param  int $project_id
     * @return bool
     */
    public function isEnabled($project_id)
    {
        return (int) $this->projectMetadataModel->get($project_id, 'qualkard_enabled', 0) === 1;
    }

    /**
     * Is the RecoReco plugin installed? (QualKard needs its move engine.)
     *
     * @return bool
     */
    public function hasRecoReco()
    {
        foreach ($this->container['pluginLoader']->getPlugins() as $plugin) {
            if ($plugin->getPluginName() === 'RecoReco') {
                return true;
            }
        }

        return false;
    }

    /**
     * The column id stored for a board role ('draft', 'study', 'hairy', ... , 'done').
     *
     * @param  int    $project_id
     * @param  string $role
     * @return int
     */
    public function col($project_id, $role)
    {
        return (int) $this->projectMetadataModel->get($project_id, 'qualkard_col_'.$role, 0);
    }

    /**
     * Is FinanceBuddy enabled on this board? QualKard refuses to convert a FinanceBuddy board (its
     * restructure would wreck the finance columns).
     *
     * @param  int $project_id
     * @return bool
     */
    public function fbEnabled($project_id)
    {
        return (int) $this->projectMetadataModel->get($project_id, 'financebuddy_enabled', 0) === 1;
    }

    /**
     * Write the inert RecoReco config for a card: move-mode to Study, fire from anywhere but Done,
     * daily (innocuous -- QualKard sets the due date on each grade), anchor 0 so RecoReco skips it
     * until the first grade arms it. QualKard never toggles recoreco_enabled again.
     *
     * @param int $task_id
     * @param int $project_id
     */
    public function arm($task_id, $project_id)
    {
        $this->taskMetadataModel->save($task_id, array(
            'recoreco_enabled' => 1,
            'recoreco_move' => 1,
            'recoreco_target_column' => $this->col($project_id, 'study'),
            'recoreco_trigger_column' => $this->col($project_id, 'done'),
            'recoreco_trigger_invert' => 1,
            'recoreco_frequency' => 'daily',
            'recoreco_anchor' => 0,
        ));

        // QualKard adopts the card as a fresh flashcard, so wipe any stale RecoReco copy lineage. A
        // card that was a RecoReco duplicate carries recoreco_clone/recoreco_source; left in place it
        // makes an armed QualKard card look like a copy (yellow icon, "cannot be made recurring"
        // modal) while the cron still moves it. Removing them makes it a clean move-mode template.
        $this->taskMetadataModel->remove($task_id, 'recoreco_clone');
        $this->taskMetadataModel->remove($task_id, 'recoreco_source');
    }

    /**
     * Reset one card: move to Drafts, mark unread, arm inert, clear the due date.
     *
     * @param int $task_id
     * @param int $project_id
     */
    public function resetCard($task_id, $project_id)
    {
        $task = $this->taskFinderModel->getById($task_id);

        if (empty($task)) {
            return;
        }

        $this->taskPositionModel->movePosition($project_id, $task_id, $this->col($project_id, 'draft'), 1, (int) $task['swimlane_id'], false);
        $this->taskMetadataModel->save($task_id, array('qualkard_avg' => self::UNREAD)); // brand-new card
        $this->arm($task_id, $project_id);
        $this->db->table(TaskModel::TABLE)->eq('id', $task_id)->update(array('date_due' => 0));
    }

    /**
     * Reset every card on a board.
     *
     * @param int $project_id
     */
    public function resetAll($project_id)
    {
        foreach ($this->taskFinderModel->getAll($project_id) as $task) {
            $this->resetCard($task['id'], $project_id);
        }
    }

    /**
     * Grade a card by a score (a grade column's value): update the running average, compute the next
     * due date, and arm the anchor. RecoReco moves the card from here.
     *
     * @param int   $task_id
     * @param float $score
     */
    public function grade($task_id, $score)
    {
        $raw = $this->taskMetadataModel->get($task_id, 'qualkard_avg', self::UNREAD);
        $old = self::parseAvg($raw);
        $avg = self::nextAverage($old, $score);
        $due = self::dueFrom($avg);

        // Store with decimals so an exact 0 is "0.0000", never the empty()-dropped "0".
        $this->taskMetadataModel->save($task_id, array(
            'qualkard_avg' => sprintf('%.4f', $avg),
            'recoreco_anchor' => $due,
        ));
        $this->db->table(TaskModel::TABLE)->eq('id', $task_id)->update(array('date_due' => $due));
    }

    /**
     * The mastery badge (label + CSS class) for a card, from its stored average.
     *
     * @param  int $task_id
     * @return array
     */
    public function cardBadge($task_id)
    {
        $raw = $this->taskMetadataModel->get($task_id, 'qualkard_avg', self::UNREAD);

        return self::badge(self::parseAvg($raw));
    }
}