<?php

declare(strict_types=1);

namespace App\Repository;

use PDO;

/**
 * Data access for the `cards` table.
 *
 * A card either sits in its owner's inbox (project_id AND status_id both
 * NULL) or belongs to exactly one project with a status in it (both set) --
 * enforced by a CHECK constraint. `position` is a dense 0..n-1 rank within a
 * "column": the cards sharing an (owner_id, project_id, status_id).
 *
 * @phpstan-type CardStatus array{id: int, name: string}
 * @phpstan-type CardRow array{
 *     id: int, owner_id: int, project_id: int|null, text: string, complete: bool, position: int,
 *     status_id: int|null, status: CardStatus|null,
 *     created_at: string, updated_at: string
 * }
 */
final class CardRepository
{
    private const SELECT = <<<'SQL'
        SELECT c.id, c.owner_id, c.project_id, c.text, c.complete, c.position, c.status_id,
               c.created_at, c.updated_at,
               s.name AS status_name
        FROM cards c
        LEFT JOIN card_statuses s ON s.id = c.status_id
        SQL;

    public function __construct(private readonly PDO $pdo)
    {
    }

    /**
     * @return CardRow[]
     */
    public function allForProject(int $projectId): array
    {
        $stmt = $this->pdo->prepare(
            self::SELECT . ' WHERE c.project_id = :project ORDER BY c.status_id, c.position ASC, c.id ASC'
        );
        $stmt->execute(['project' => $projectId]);

        return array_map($this->cast(...), $stmt->fetchAll());
    }

    /**
     * The owner's global inbox, in position order.
     *
     * @return CardRow[]
     */
    public function allInInbox(int $ownerId): array
    {
        return $this->columnCards($ownerId, null, null);
    }

    /**
     * A card owned by the caller, wherever it is (inbox or a project).
     *
     * @return CardRow|null
     */
    public function findOwnedBy(int $id, int $ownerId): ?array
    {
        $stmt = $this->pdo->prepare(self::SELECT . ' WHERE c.id = :id AND c.owner_id = :owner');
        $stmt->execute(['id' => $id, 'owner' => $ownerId]);

        $row = $stmt->fetch();

        return $row === false ? null : $this->cast($row);
    }

    /**
     * Create a card directly in a project, at the end of the given status.
     *
     * @return CardRow
     */
    public function createInProject(
        int $ownerId,
        int $projectId,
        int $statusId,
        string $text,
        bool $complete,
        ?int $position,
    ): array {
        $position ??= $this->nextPositionInColumn($ownerId, $projectId, $statusId);

        return $this->insert($ownerId, $projectId, $statusId, $text, $complete, $position);
    }

    /**
     * Create a card in the owner's inbox.
     *
     * @return CardRow
     */
    public function createInInbox(int $ownerId, string $text, bool $complete, ?int $position): array
    {
        $position ??= $this->nextPositionInColumn($ownerId, null, null);

        return $this->insert($ownerId, null, null, $text, $complete, $position);
    }

    /**
     * Update text/complete. Moving a card between columns -- including in or
     * out of the inbox -- is done via orderColumn(), not here.
     *
     * @param array{text?: string, complete?: bool} $fields
     * @return CardRow
     */
    public function update(int $id, array $fields): array
    {
        $sets = ['updated_at = ' . $this->nowExpr()];
        $params = ['id' => $id];

        if (array_key_exists('text', $fields)) {
            $sets[] = 'text = :text';
            $params['text'] = $fields['text'];
        }
        if (array_key_exists('complete', $fields)) {
            $sets[] = 'complete = :complete';
            $params['complete'] = $fields['complete'] ? 1 : 0;
        }

        $this->pdo->prepare('UPDATE cards SET ' . implode(', ', $sets) . ' WHERE id = :id')->execute($params);

        /** @var CardRow $card */
        $card = $this->find($id);

        return $card;
    }

    public function delete(int $id): void
    {
        $this->pdo->prepare('DELETE FROM cards WHERE id = :id')->execute(['id' => $id]);
    }

    /**
     * Every card id owned by this user, wherever it is.
     *
     * @return int[]
     */
    public function idsOwnedBy(int $ownerId): array
    {
        $stmt = $this->pdo->prepare('SELECT id FROM cards WHERE owner_id = :owner');
        $stmt->execute(['owner' => $ownerId]);

        return array_map(intval(...), $stmt->fetchAll(PDO::FETCH_COLUMN));
    }

    /**
     * IDs of the cards currently in one column, in position order.
     *
     * @return int[]
     */
    public function idsInColumn(int $ownerId, ?int $projectId, ?int $statusId): array
    {
        [$match, $params] = $this->columnMatch($projectId, $statusId);
        $stmt = $this->pdo->prepare(
            "SELECT id FROM cards WHERE owner_id = :owner AND {$match} ORDER BY position ASC, id ASC"
        );
        $stmt->execute(['owner' => $ownerId] + $params);

        return array_map(intval(...), $stmt->fetchAll(PDO::FETCH_COLUMN));
    }

    /**
     * Set the contents and order of one column -- the inbox (both null) or a
     * project's status (both set). Every id in $orderedIds is moved there at
     * positions 0..n-1; any other column those cards came from (another
     * project's status, the inbox, ...) is re-packed. One transaction.
     *
     * @param int[] $orderedIds
     * @return CardRow[] the column's cards, in their new order
     */
    public function orderColumn(int $ownerId, ?int $projectId, ?int $statusId, array $orderedIds): array
    {
        $orderedIds = array_values($orderedIds);

        $this->pdo->beginTransaction();
        try {
            $sources = $this->columnsOf($ownerId, $orderedIds);

            $place = $this->pdo->prepare(
                'UPDATE cards SET project_id = :project, status_id = :status, position = :position,
                        updated_at = ' . $this->nowExpr() . '
                 WHERE id = :id AND owner_id = :owner'
            );
            foreach ($orderedIds as $position => $id) {
                $place->execute([
                    'project' => $projectId,
                    'status' => $statusId,
                    'position' => $position,
                    'id' => $id,
                    'owner' => $ownerId,
                ]);
            }

            foreach ($sources as [$sourceProject, $sourceStatus]) {
                if ($sourceProject === $projectId && $sourceStatus === $statusId) {
                    continue;
                }
                $this->repack($ownerId, $sourceProject, $sourceStatus);
            }

            $this->pdo->commit();
        } catch (\Throwable $e) {
            $this->pdo->rollBack();
            throw $e;
        }

        return $this->columnCards($ownerId, $projectId, $statusId);
    }

    /**
     * Move every card in one project status to another status in the same
     * project -- used when a status is deleted out from under them. Appended
     * after the destination's existing cards, so both columns stay a dense
     * 0..n-1 with no repack needed.
     */
    public function reassignStatus(int $ownerId, int $projectId, int $fromStatusId, int $toStatusId): void
    {
        $ids = $this->idsInColumn($ownerId, $projectId, $fromStatusId);
        if ($ids === []) {
            return;
        }

        $next = $this->nextPositionInColumn($ownerId, $projectId, $toStatusId);
        $stmt = $this->pdo->prepare(
            'UPDATE cards SET status_id = :status, position = :position, updated_at = ' . $this->nowExpr() . '
             WHERE id = :id AND owner_id = :owner'
        );
        foreach ($ids as $i => $id) {
            $stmt->execute(['status' => $toStatusId, 'position' => $next + $i, 'id' => $id, 'owner' => $ownerId]);
        }
    }

    private function insert(
        int $ownerId,
        ?int $projectId,
        ?int $statusId,
        string $text,
        bool $complete,
        int $position,
    ): array {
        $stmt = $this->pdo->prepare(
            'INSERT INTO cards (owner_id, project_id, status_id, text, complete, position)
             VALUES (:owner, :project, :status, :text, :complete, :position)'
        );
        $stmt->execute([
            'owner' => $ownerId,
            'project' => $projectId,
            'status' => $statusId,
            'text' => $text,
            'complete' => $complete ? 1 : 0,
            'position' => $position,
        ]);

        /** @var CardRow $card */
        $card = $this->find((int) $this->pdo->lastInsertId());

        return $card;
    }

    /**
     * @return CardRow[]
     */
    private function columnCards(int $ownerId, ?int $projectId, ?int $statusId): array
    {
        // Qualified with c. -- self::SELECT joins card_statuses, which also
        // has a project_id, so the bare column name is ambiguous here.
        [$match, $params] = $this->columnMatch($projectId, $statusId, 'c.');
        $stmt = $this->pdo->prepare(
            self::SELECT . " WHERE c.owner_id = :owner AND {$match} ORDER BY c.position ASC, c.id ASC"
        );
        $stmt->execute(['owner' => $ownerId] + $params);

        return array_map($this->cast(...), $stmt->fetchAll());
    }

    /**
     * The distinct (project_id, status_id) columns the given cards currently
     * sit in.
     *
     * @param int[] $ids
     * @return list<array{0: int|null, 1: int|null}>
     */
    private function columnsOf(int $ownerId, array $ids): array
    {
        if ($ids === []) {
            return [];
        }

        $placeholders = implode(',', array_fill(0, count($ids), '?'));
        $stmt = $this->pdo->prepare(
            "SELECT DISTINCT project_id, status_id FROM cards WHERE owner_id = ? AND id IN ($placeholders)"
        );
        $stmt->execute([$ownerId, ...$ids]);

        return array_map(
            static fn (array $row): array => [
                $row['project_id'] === null ? null : (int) $row['project_id'],
                $row['status_id'] === null ? null : (int) $row['status_id'],
            ],
            $stmt->fetchAll(PDO::FETCH_ASSOC),
        );
    }

    /** Rewrite one column's positions to a dense 0..n-1 in current order. */
    private function repack(int $ownerId, ?int $projectId, ?int $statusId): void
    {
        $ids = $this->idsInColumn($ownerId, $projectId, $statusId);

        $update = $this->pdo->prepare('UPDATE cards SET position = :position WHERE id = :id');
        foreach ($ids as $position => $id) {
            $update->execute(['position' => $position, 'id' => $id]);
        }
    }

    private function nextPositionInColumn(int $ownerId, ?int $projectId, ?int $statusId): int
    {
        [$match, $params] = $this->columnMatch($projectId, $statusId);
        $stmt = $this->pdo->prepare(
            "SELECT COALESCE(MAX(position), -1) + 1 FROM cards WHERE owner_id = :owner AND {$match}"
        );
        $stmt->execute(['owner' => $ownerId] + $params);

        return (int) $stmt->fetchColumn();
    }

    /**
     * A WHERE fragment matching one column. The inbox is (project_id IS NULL
     * AND status_id IS NULL); a project column is an exact pair -- the CHECK
     * constraint guarantees they're never mismatched. $prefix qualifies the
     * column names (e.g. "c.") for queries that join card_statuses, which
     * also has a project_id.
     *
     * @return array{0: string, 1: array<string, int>}
     */
    private function columnMatch(?int $projectId, ?int $statusId, string $prefix = ''): array
    {
        return $projectId === null
            ? ["{$prefix}project_id IS NULL AND {$prefix}status_id IS NULL", []]
            : [
                "{$prefix}project_id = :project AND {$prefix}status_id = :status",
                ['project' => $projectId, 'status' => $statusId],
            ];
    }

    /**
     * @return CardRow|null
     */
    private function find(int $id): ?array
    {
        $stmt = $this->pdo->prepare(self::SELECT . ' WHERE c.id = :id');
        $stmt->execute(['id' => $id]);

        $row = $stmt->fetch();

        return $row === false ? null : $this->cast($row);
    }

    private function nowExpr(): string
    {
        return "strftime('%Y-%m-%dT%H:%M:%SZ', 'now')";
    }

    /**
     * @param array<string, mixed> $row
     * @return CardRow
     */
    private function cast(array $row): array
    {
        $row['id'] = (int) $row['id'];
        $row['owner_id'] = (int) $row['owner_id'];
        $row['project_id'] = $row['project_id'] === null ? null : (int) $row['project_id'];
        $row['complete'] = (bool) $row['complete'];
        $row['position'] = (int) $row['position'];

        $statusId = $row['status_id'] === null ? null : (int) $row['status_id'];
        $row['status_id'] = $statusId;
        $row['status'] = $statusId === null
            ? null
            : ['id' => $statusId, 'name' => (string) $row['status_name']];
        unset($row['status_name']);

        /** @var CardRow $row */
        return $row;
    }
}