<?php
// ─── DB migrations runner ────────────────────────────────────────────────────
//
// Lightweight, dependency-free runner over the `database/migration_*.sql`
// files in the host repo. State is tracked in `applied_migrations` (auto-created
// on first call). Files are matched by basename only — path traversal is
// blocked by an explicit regex.
//
// Public API:
//   db_ensure_migrations_table(PDO $pdo): void
//   migrations_dir(): string                        — host repo migrations dir
//   migrations_list_files(): array                  — basenames, sorted
//   migrations_status(PDO $pdo): array              — [{filename, applied_at|null}]
//   migrations_apply_file(PDO, string $filename, ?int $userId): array
//   migrations_mark_all_applied(PDO, ?int $userId): int
//   migrations_split_sql(string $sql): array        — string/comment-aware splitter
//
// Migrations directory resolution:
//   1. $GLOBALS['MIGRATIONS_DIR'] if set (set this in the stub for non-standard layouts)
//   2. Otherwise: dirname(__DIR__, 2) . '/database'
//      Assumes this file lives at <host_repo>/shared/platform-tools/functions_migrations.php
//      → resolves to <host_repo>/database.

function migrations_dir(): string {
    $dir = $GLOBALS['MIGRATIONS_DIR'] ?? (dirname(__DIR__, 2) . '/database');
    return rtrim($dir, '/');
}

function db_ensure_migrations_table(PDO $pdo): void {
    // FK on applied_by is intentionally omitted: tenants vary in whether
    // they have a `users` table by this name. The application enforces
    // referential semantics already (we only ever insert the caller's
    // user_id; deletion of that user is rare and orphan rows are harmless).
    $pdo->exec(
        "CREATE TABLE IF NOT EXISTS `applied_migrations` (
            `filename`   VARCHAR(150) NOT NULL,
            `applied_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            `applied_by` INT DEFAULT NULL,
            PRIMARY KEY (`filename`)
         ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci"
    );
}

function migrations_list_files(): array {
    $files = glob(migrations_dir() . '/migration_*.sql') ?: [];
    sort($files);
    return array_map('basename', $files);
}

function migrations_status(PDO $pdo): array {
    db_ensure_migrations_table($pdo);
    $applied = $pdo->query("SELECT filename, applied_at FROM applied_migrations")
                   ->fetchAll(PDO::FETCH_KEY_PAIR);
    $applied = $applied ?: [];
    $rows = [];
    foreach (migrations_list_files() as $file) {
        $rows[] = [
            'filename'   => $file,
            'applied_at' => $applied[$file] ?? null,
        ];
    }
    return $rows;
}

// Split a SQL blob into individual statements, respecting strings, escapes,
// line comments (-- … and # …) and block comments (/* … */). Comments are
// recognised inside the same state machine that tracks string literals, so a
// value like 'use -- with care' or 'a /* b */ c' passes through untouched.
// DELIMITER changes are not supported (project migrations don't use stored
// procedures).
function migrations_split_sql(string $sql): array {
    $statements = [];
    $current    = '';
    $in_string  = false;
    $quote      = null;
    $len        = strlen($sql);

    for ($i = 0; $i < $len; $i++) {
        $ch = $sql[$i];

        if ($in_string) {
            // Backslash escapes apply inside '…' and "…", never inside `…`.
            if ($ch === '\\' && $quote !== '`' && $i + 1 < $len) {
                $current .= $ch . $sql[$i + 1];
                $i++;
                continue;
            }
            if ($ch === $quote) {
                if ($i + 1 < $len && $sql[$i + 1] === $quote) {
                    $current .= $ch . $sql[$i + 1];
                    $i++;
                    continue;
                }
                $in_string = false;
                $quote = null;
            }
            $current .= $ch;
            continue;
        }

        // Block comment /* … */ — dropped (including /*! … */ version hints).
        if ($ch === '/' && $i + 1 < $len && $sql[$i + 1] === '*') {
            $end = strpos($sql, '*/', $i + 2);
            $i   = ($end === false) ? $len : $end + 1;
            continue;
        }

        // Line comment: `#`, or `--` followed by whitespace/EOL (MySQL rule —
        // `a--b` is arithmetic, not a comment).
        if ($ch === '#'
            || ($ch === '-' && $i + 1 < $len && $sql[$i + 1] === '-'
                && ($i + 2 >= $len || strpbrk($sql[$i + 2], " \t\r\n") !== false))) {
            $nl = strpos($sql, "\n", $i);
            if ($nl === false) break;      // comment runs to end of input
            $i = $nl - 1;                  // keep the \n as statement whitespace
            continue;
        }

        if ($ch === "'" || $ch === '"' || $ch === '`') {
            $in_string = true;
            $quote = $ch;
            $current .= $ch;
            continue;
        }

        if ($ch === ';') {
            $stmt = trim($current);
            if ($stmt !== '') $statements[] = $stmt;
            $current = '';
            continue;
        }

        $current .= $ch;
    }

    $stmt = trim($current);
    if ($stmt !== '') $statements[] = $stmt;

    return $statements;
}

function migrations_apply_file(PDO $pdo, string $filename, ?int $userId = null): array {
    if (!preg_match('/^migration_[a-z0-9_]+\.sql$/i', $filename)) {
        return ['ok' => false, 'error' => 'Nome de migration inválido.'];
    }
    $path = migrations_dir() . '/' . $filename;
    if (!is_file($path)) {
        return ['ok' => false, 'error' => "Ficheiro não encontrado: {$filename}"];
    }

    db_ensure_migrations_table($pdo);

    $stmt = $pdo->prepare("SELECT 1 FROM applied_migrations WHERE filename = ?");
    $stmt->execute([$filename]);
    if ($stmt->fetchColumn()) {
        return ['ok' => false, 'error' => 'Já aplicada anteriormente.'];
    }

    $sql = file_get_contents($path);
    if ($sql === false) {
        return ['ok' => false, 'error' => 'Não foi possível ler o ficheiro.'];
    }

    $statements = migrations_split_sql($sql);
    if (!$statements) {
        return ['ok' => false, 'error' => 'O ficheiro não contém statements SQL.'];
    }

    $applied = 0;
    foreach ($statements as $statement) {
        try {
            $pdo->exec($statement);
            $applied++;
        } catch (PDOException $e) {
            return [
                'ok'      => false,
                'error'   => 'Erro no statement #' . ($applied + 1) . ': ' . $e->getMessage(),
                'applied' => $applied,
                'total'   => count($statements),
            ];
        }
    }

    $stmt = $pdo->prepare(
        "INSERT INTO applied_migrations (filename, applied_by) VALUES (?, ?)"
    );
    $stmt->execute([$filename, $userId]);

    return ['ok' => true, 'applied' => $applied, 'total' => count($statements)];
}

function migrations_mark_all_applied(PDO $pdo, ?int $userId = null): int {
    db_ensure_migrations_table($pdo);
    $existing = $pdo->query("SELECT filename FROM applied_migrations")
                    ->fetchAll(PDO::FETCH_COLUMN);
    $existing = array_flip($existing ?: []);
    $stmt = $pdo->prepare(
        "INSERT INTO applied_migrations (filename, applied_by) VALUES (?, ?)"
    );
    $count = 0;
    foreach (migrations_list_files() as $file) {
        if (!isset($existing[$file])) {
            $stmt->execute([$file, $userId]);
            $count++;
        }
    }
    return $count;
}