<?php

declare(strict_types=1);

const DB_DIR = __DIR__ . '/data';
const DB_FILE = DB_DIR . '/go.sqlite';

header('Content-Type: application/json; charset=utf-8');

try {
    $db = db();
    migrate($db);

    $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
    $action = $_GET['action'] ?? null;

    if ($method === 'GET') {
        if ($action === null || $action === 'state') {
            respond([
                'settings' => get_settings($db),
                'entries' => get_entries($db),
                'corrections' => get_corrections($db),
                'feriefridage_overrides' => get_feriefridage_overrides($db),
                'flex_overrides' => get_flex_overrides($db),
            ]);
        }
        fail('Unknown GET action', 404);
    }

    if ($method === 'POST') {
        $payload = json_decode(file_get_contents('php://input') ?: '{}', true);
        if (!is_array($payload)) {
            fail('Invalid JSON payload', 400);
        }
        $action = $payload['action'] ?? $action;

        switch ($action) {
            case 'saveSettings':
                save_settings($db, $payload['settings'] ?? []);
                respond(['ok' => true, 'settings' => get_settings($db)]);
                break;

            case 'saveCorrection':
                save_correction($db, (int)($payload['year'] ?? 0), (int)($payload['month'] ?? 0), $payload['value'] ?? null);
                respond(['ok' => true, 'corrections' => get_corrections($db)]);
                break;

            case 'saveFeriefridageOverride':
                save_feriefridage_override($db, (int)($payload['year'] ?? 0), (int)($payload['month'] ?? 0), $payload['value'] ?? null);
                respond(['ok' => true, 'feriefridage_overrides' => get_feriefridage_overrides($db)]);
                break;

            case 'saveFlexOverride':
                save_flex_override($db, (int)($payload['year'] ?? 0), (int)($payload['month'] ?? 0), $payload['value'] ?? null);
                respond(['ok' => true, 'flex_overrides' => get_flex_overrides($db)]);
                break;

            case 'createEntry':
                $id = save_entry($db, $payload['entry'] ?? []);
                respond(['ok' => true, 'id' => $id, 'entries' => get_entries($db)]);
                break;

            case 'updateEntry':
                $id = (int)($payload['id'] ?? 0);
                if ($id <= 0) {
                    fail('Missing entry id', 400);
                }
                save_entry($db, $payload['entry'] ?? [], $id);
                respond(['ok' => true, 'entries' => get_entries($db)]);
                break;

            case 'deleteEntry':
                $id = (int)($payload['id'] ?? 0);
                if ($id <= 0) {
                    fail('Missing entry id', 400);
                }
                $stmt = $db->prepare('DELETE FROM entries WHERE id = :id');
                $stmt->execute([':id' => $id]);
                respond(['ok' => true, 'entries' => get_entries($db)]);
                break;

            default:
                fail('Unknown POST action', 404);
        }
    }

    fail('Unsupported method', 405);
} catch (Throwable $e) {
    fail($e->getMessage(), 500);
}

function db(): PDO
{
    if (!is_dir(DB_DIR) && !mkdir(DB_DIR, 0775, true) && !is_dir(DB_DIR)) {
        throw new RuntimeException('Could not create data directory');
    }

    $db = new PDO('sqlite:' . DB_FILE);
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
    $db->exec('PRAGMA foreign_keys = ON');
    return $db;
}

function migrate(PDO $db): void
{
    $db->exec("CREATE TABLE IF NOT EXISTS settings (
        key TEXT PRIMARY KEY,
        value TEXT NOT NULL
    )");

    $db->exec("CREATE TABLE IF NOT EXISTS entries (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        title TEXT NOT NULL,
        start_date TEXT NOT NULL,
        end_date TEXT NOT NULL,
        source TEXT NOT NULL DEFAULT 'auto',
        status TEXT NOT NULL DEFAULT 'planned',
        allow_unpaid INTEGER NOT NULL DEFAULT 0,
        note TEXT NOT NULL DEFAULT '',
        created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
        updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
    )");

    $db->exec("CREATE TABLE IF NOT EXISTS monthly_corrections (
        year INTEGER NOT NULL,
        month INTEGER NOT NULL,
        vacation_days REAL NOT NULL DEFAULT 0,
        PRIMARY KEY (year, month)
    )");

    $db->exec("CREATE TABLE IF NOT EXISTS monthly_feriefridage_overrides (
        year INTEGER NOT NULL,
        month INTEGER NOT NULL,
        feriefridage_days REAL NOT NULL DEFAULT 0,
        PRIMARY KEY (year, month)
    )");

    $db->exec("CREATE TABLE IF NOT EXISTS monthly_flex_overrides (
        year INTEGER NOT NULL,
        month INTEGER NOT NULL,
        flex_hours REAL NOT NULL DEFAULT 0,
        PRIMARY KEY (year, month)
    )");

    $defaults = [
        'planning_start_year' => '2026',
        'planning_start_month' => '1',
        'planning_years' => '3',
        'planning_months' => '36',
        'previous_months' => '5',
        'future_months' => '30',
        'vacation_days_per_month' => '2.08',
        'feriefridage_per_year' => '5',
        'feriefridage_expiry_month' => '8',
        'normal_day_hours' => '7.5',
        'friday_hours' => '7',
        'opening_vacation_days' => '-1.97',
        'opening_feriefridage_days' => '0',
        'opening_flex_hours' => '0',
        'current_flex_hours' => '46.5',
    ];

    $stmt = $db->prepare('INSERT OR IGNORE INTO settings (key, value) VALUES (:key, :value)');
    foreach ($defaults as $key => $value) {
        $stmt->execute([':key' => $key, ':value' => $value]);
    }
}

function get_settings(PDO $db): array
{
    $rows = $db->query('SELECT key, value FROM settings')->fetchAll();
    $settings = [];
    foreach ($rows as $row) {
        $settings[$row['key']] = numeric_value($row['value']);
    }
    return $settings;
}

function save_settings(PDO $db, array $settings): void
{
    $allowed = [
        'planning_start_year',
        'planning_start_month',
        'planning_years',
        'planning_months',
        'previous_months',
        'future_months',
        'vacation_days_per_month',
        'feriefridage_per_year',
        'feriefridage_expiry_month',
        'normal_day_hours',
        'friday_hours',
        'opening_vacation_days',
        'opening_feriefridage_days',
        'opening_flex_hours',
        'current_flex_hours',
    ];

    $stmt = $db->prepare('INSERT INTO settings (key, value) VALUES (:key, :value)
        ON CONFLICT(key) DO UPDATE SET value = excluded.value');

    foreach ($allowed as $key) {
        if (array_key_exists($key, $settings)) {
            $stmt->execute([':key' => $key, ':value' => (string)$settings[$key]]);
        }
    }
}

function get_corrections(PDO $db): array
{
    $rows = $db->query('SELECT year, month, vacation_days FROM monthly_corrections ORDER BY year, month')->fetchAll();
    $corrections = [];
    foreach ($rows as $row) {
        $corrections[$row['year'] . '-' . str_pad((string)$row['month'], 2, '0', STR_PAD_LEFT)] = (float)$row['vacation_days'];
    }
    return $corrections;
}

function save_correction(PDO $db, int $year, int $month, mixed $value): void
{
    if ($year < 1900 || $year > 2200 || $month < 1 || $month > 12) {
        fail('Invalid correction year/month', 400);
    }

    if ($value === null || $value === '') {
        $stmt = $db->prepare('DELETE FROM monthly_corrections WHERE year = :year AND month = :month');
        $stmt->execute([':year' => $year, ':month' => $month]);
        return;
    }

    $stmt = $db->prepare('INSERT INTO monthly_corrections (year, month, vacation_days)
        VALUES (:year, :month, :value)
        ON CONFLICT(year, month) DO UPDATE SET vacation_days = excluded.vacation_days');
    $stmt->execute([':year' => $year, ':month' => $month, ':value' => (float)$value]);
}

function get_feriefridage_overrides(PDO $db): array
{
    $rows = $db->query('SELECT year, month, feriefridage_days FROM monthly_feriefridage_overrides ORDER BY year, month')->fetchAll();
    $overrides = [];
    foreach ($rows as $row) {
        $overrides[$row['year'] . '-' . str_pad((string)$row['month'], 2, '0', STR_PAD_LEFT)] = (float)$row['feriefridage_days'];
    }
    return $overrides;
}

function save_feriefridage_override(PDO $db, int $year, int $month, mixed $value): void
{
    if ($year < 1900 || $year > 2200 || $month < 1 || $month > 12) {
        fail('Invalid feriefridage override year/month', 400);
    }

    if ($value === null || $value === '') {
        $stmt = $db->prepare('DELETE FROM monthly_feriefridage_overrides WHERE year = :year AND month = :month');
        $stmt->execute([':year' => $year, ':month' => $month]);
        return;
    }

    $stmt = $db->prepare('INSERT INTO monthly_feriefridage_overrides (year, month, feriefridage_days)
        VALUES (:year, :month, :value)
        ON CONFLICT(year, month) DO UPDATE SET feriefridage_days = excluded.feriefridage_days');
    $stmt->execute([':year' => $year, ':month' => $month, ':value' => (float)$value]);
}

function get_flex_overrides(PDO $db): array
{
    $rows = $db->query('SELECT year, month, flex_hours FROM monthly_flex_overrides ORDER BY year, month')->fetchAll();
    $overrides = [];
    foreach ($rows as $row) {
        $overrides[$row['year'] . '-' . str_pad((string)$row['month'], 2, '0', STR_PAD_LEFT)] = (float)$row['flex_hours'];
    }
    return $overrides;
}

function save_flex_override(PDO $db, int $year, int $month, mixed $value): void
{
    if ($year < 1900 || $year > 2200 || $month < 1 || $month > 12) {
        fail('Invalid FLEX override year/month', 400);
    }

    if ($value === null || $value === '') {
        $stmt = $db->prepare('DELETE FROM monthly_flex_overrides WHERE year = :year AND month = :month');
        $stmt->execute([':year' => $year, ':month' => $month]);
        return;
    }

    $stmt = $db->prepare('INSERT INTO monthly_flex_overrides (year, month, flex_hours)
        VALUES (:year, :month, :value)
        ON CONFLICT(year, month) DO UPDATE SET flex_hours = excluded.flex_hours');
    $stmt->execute([':year' => $year, ':month' => $month, ':value' => (float)$value]);
}

function get_entries(PDO $db): array
{
    return $db->query('SELECT id, title, start_date, end_date, source, status, allow_unpaid, note
        FROM entries ORDER BY start_date, end_date, id')->fetchAll();
}

function save_entry(PDO $db, array $entry, ?int $id = null): int
{
    $title = trim((string)($entry['title'] ?? ''));
    $start = trim((string)($entry['start_date'] ?? ''));
    $end = trim((string)($entry['end_date'] ?? ''));
    $source = (string)($entry['source'] ?? 'auto');
    $status = (string)($entry['status'] ?? 'planned');
    $allowUnpaid = !empty($entry['allow_unpaid']) ? 1 : 0;
    $note = trim((string)($entry['note'] ?? ''));

    if ($title === '') {
        fail('Title is required', 400);
    }
    if (!valid_date($start) || !valid_date($end)) {
        fail('Start/end date must be YYYY-MM-DD', 400);
    }
    if ($start > $end) {
        fail('Start date must be before end date', 400);
    }
    if (!in_array($source, ['auto', 'vacation', 'feriefridag', 'flex', 'unpaid'], true)) {
        fail('Invalid source', 400);
    }
    if ($status === 'confirmed') {
        $status = 'approved';
    }
    if (!in_array($status, ['planned', 'approved'], true)) {
        fail('Invalid status', 400);
    }

    $params = [
        ':title' => $title,
        ':start_date' => $start,
        ':end_date' => $end,
        ':source' => $source,
        ':status' => $status,
        ':allow_unpaid' => $allowUnpaid,
        ':note' => $note,
    ];

    if ($id === null) {
        $stmt = $db->prepare('INSERT INTO entries
            (title, start_date, end_date, source, status, allow_unpaid, note)
            VALUES (:title, :start_date, :end_date, :source, :status, :allow_unpaid, :note)');
        $stmt->execute($params);
        return (int)$db->lastInsertId();
    }

    $params[':id'] = $id;
    $stmt = $db->prepare('UPDATE entries SET
        title = :title,
        start_date = :start_date,
        end_date = :end_date,
        source = :source,
        status = :status,
        allow_unpaid = :allow_unpaid,
        note = :note,
        updated_at = CURRENT_TIMESTAMP
        WHERE id = :id');
    $stmt->execute($params);
    return $id;
}

function valid_date(string $date): bool
{
    $d = DateTime::createFromFormat('Y-m-d', $date);
    return $d && $d->format('Y-m-d') === $date;
}

function numeric_value(string $value): int|float|string
{
    if (is_numeric($value)) {
        return str_contains($value, '.') ? (float)$value : (int)$value;
    }
    return $value;
}

function respond(array $data): never
{
    echo json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
    exit;
}

function fail(string $message, int $status): never
{
    http_response_code($status);
    echo json_encode(['error' => $message], JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
    exit;
}