<?php

declare(strict_types=1);

namespace GitContributionGraph\Service;

use GitContributionGraph\Entity\Contribution;
use GitContributionGraph\Entity\ContributionCollection;
use PDO;

class ContributionStore
{
    private PDO $pdo;
    private const int DAY_IN_SECONDS = 86400;

    /**
     * Opens (creating if needed) the SQLite store at $dbPath and ensures the schema exists.
     *
     * @param string $dbPath        filesystem path to the SQLite database file
     * @param ?int   $retentionDays days of history to keep; null or 0 keeps rows forever
     */
    public function __construct(
        private readonly string $dbPath = "%kernel.project_dir%/var/data/contributions.db",
        private readonly ?int $retentionDays = null,
    ) {
        $dir = \dirname($this->dbPath);
        if (!is_dir($dir)) {
            mkdir($dir, 0755, recursive: true);
        }
        $this->pdo = new PDO('sqlite:' . $this->dbPath);
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->prepareSchema();
    }

    private function prepareSchema(): void
    {
        $this->pdo->exec('
            CREATE TABLE IF NOT EXISTS contributions (
                provider TEXT NOT NULL,
                date     INTEGER NOT NULL,
                count    INTEGER NOT NULL CHECK (count >= 0),
                PRIMARY KEY (provider, date)
            ) WITHOUT ROWID, STRICT
        ');
    }

    /**
     * Inserts a contribution count, overwriting any existing count for the same provider/date.
     *
     * @param string $provider provider identifier, e.g. "github"
     * @param int    $unixtime day of the contribution, as a unix timestamp
     * @param int    $count    contribution count for that day
     */
    public function add(string $provider, int $unixtime, int $count): void
    {
        $stmt = $this->pdo->prepare('
            INSERT INTO contributions (provider, date, count)
            VALUES (?, ?, ?)
            ON CONFLICT(provider, date) DO UPDATE SET count = excluded.count
        ');
        $stmt->execute([$provider, $unixtime, $count]);
    }

    /**
     * Deletes the contribution row for the given provider/date, if any.
     *
     * @param string $provider provider identifier, e.g. "github"
     * @param int    $unixtime day to delete, as a unix timestamp
     */
    public function remove(string $provider, int $unixtime): void
    {
        $stmt = $this->pdo->prepare('
            DELETE FROM contributions
            WHERE provider = ? AND date = ?
        ');
        $stmt->execute([$provider, $unixtime]);
    }

    /**
     * Upserts a batch of date => count pairs for a provider via repeated add() calls.
     *
     * @param string           $provider   provider identifier, e.g. "github"
     * @param array<int, int>  $dateCounts unix timestamp => count
     */
    public function merge(string $provider, array $dateCounts): void
    {
        foreach ($dateCounts as $unixtime => $count) {
            $this->add($provider, $unixtime, $count);
        }
    }

    /**
     * Returns the most recent stored unix timestamp for a provider, or null if it has no rows.
     *
     * @param  string $provider provider identifier, e.g. "github"
     * @return ?int   unix timestamp of the latest stored day, or null if none stored yet
     */
    public function latestDate(string $provider): ?int
    {
        $stmt = $this->pdo->prepare('SELECT MAX(date) FROM contributions WHERE provider = ?');
        $stmt->execute([$provider]);
        $result = $stmt->fetchColumn();

        return $result !== null ? (int) $result : null;
    }

    /**
     * Returns all stored contributions for a provider, optionally limited to the last $sinceDays days.
     *
     * @param  string $provider  provider identifier, e.g. "github"
     * @param  ?int   $sinceDays if set, only rows from the last N days are returned
     * @return ContributionCollection
     */
    public function all(string $provider, ?int $sinceDays = null): ContributionCollection
    {
        $sql = 'SELECT provider, date, count FROM contributions WHERE provider = ?';
        $params = [$provider];

        if ($sinceDays !== null) {
            $sql .= ' AND date >= ?';
            $params[] = time() - $sinceDays * self::DAY_IN_SECONDS;
        }

        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($params);

        /** @var array<int, array{provider: string, date: int|string, count: int|string}> $rows */
        $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

        $contributions = array_map(
            static fn(array $row): Contribution => new Contribution($row['provider'], (int) $row['date'], (int) $row['count']),
            $rows,
        );

        return new ContributionCollection(...$contributions);
    }

    /**
     * Deletes rows older than the configured retention window; a no-op if retention is unset or 0.
     */
    public function prune(): void
    {
        if ($this->retentionDays === null || $this->retentionDays === 0) {
            return;
        }

        $cutoff = time() - $this->retentionDays * self::DAY_IN_SECONDS;

        $stmt = $this->pdo->prepare('DELETE FROM contributions WHERE date < ?');
        $stmt->execute([$cutoff]);
    }
}