<?php

namespace App\Services\Hosting;

use App\Models\HostingAccount;
use Illuminate\Support\Facades\Process;
use Illuminate\Support\Str;

class BrowserTerminalSessionManager
{
    private const IDLE_TIMEOUT_SECONDS = 120;

    // How long createSession() waits for the worker to cold-boot the framework
    // and open the shell before returning. Generous so a slow/loaded boot isn't
    // mistaken for a failure; the wait returns early once the status is known.
    private const STARTUP_TIMEOUT_SECONDS = 8.0;

    public function createSession(HostingAccount $account, int $userId, string $relativePath = '/public_html', int $cols = 120, int $rows = 30): array
    {
        $sessionId = (string) Str::uuid();
        $directory = $this->sessionDirectory($sessionId);

        if (! is_dir($directory) && ! mkdir($directory, 0775, true) && ! is_dir($directory)) {
            throw new \RuntimeException('Unable to create browser terminal session directory.');
        }

        touch($this->eventLogPath($sessionId));
        touch($this->outputLogPath($sessionId));
        touch($this->heartbeatPath($sessionId));

        $metadata = [
            'session_id' => $sessionId,
            'account_id' => $account->id,
            'user_id' => $userId,
            'username' => $account->username,
            'relative_path' => $relativePath,
            'cols' => $this->normalizeColumns($cols),
            'rows' => $this->normalizeRows($rows),
            'status' => 'starting',
            'created_at' => now()->toIso8601String(),
            'last_seen_at' => now()->toIso8601String(),
            'pid' => null,
            'exit_code' => null,
            'error' => null,
        ];

        $this->writeMetadata($sessionId, $metadata);

        $workerCommand = $this->buildWorkerCommand($sessionId);

        $result = Process::timeout(10)->run(['bash', '-lc', $workerCommand]);
        $pid = trim($result->output());

        if ($result->failed() || $pid === '' || ! ctype_digit($pid)) {
            $metadata['status'] = 'failed';
            $metadata['error'] = 'Unable to start the browser terminal worker.';
            $this->writeMetadata($sessionId, $metadata);

            throw new \RuntimeException($metadata['error']);
        }

        $metadata['pid'] = (int) $pid;
        $this->writeMetadata($sessionId, $metadata);

        $metadata = $this->waitForWorkerStartup($sessionId, $metadata);

        return $metadata;
    }

    public function readOutput(HostingAccount $account, int $userId, string $sessionId, int $offset = 0): array
    {
        $metadata = $this->sessionMetadataFor($account, $userId, $sessionId);
        $offset = max(0, $offset);
        $outputPath = $this->outputLogPath($sessionId);
        $size = is_file($outputPath) ? filesize($outputPath) : 0;
        $chunk = '';

        if ($size > $offset) {
            $stream = fopen($outputPath, 'rb');

            if ($stream !== false) {
                fseek($stream, $offset);
                $chunk = (string) stream_get_contents($stream);
                fclose($stream);
            }
        }

        $this->touchHeartbeat($sessionId);

        return [
            'output' => $chunk,
            'offset' => $size,
            'status' => $metadata['status'] ?? 'closed',
            'exit_code' => $metadata['exit_code'] ?? null,
            'error' => $metadata['error'] ?? null,
        ];
    }

    public function appendInput(HostingAccount $account, int $userId, string $sessionId, string $input): void
    {
        $this->sessionMetadataFor($account, $userId, $sessionId);
        $this->touchHeartbeat($sessionId);

        $this->appendEvent($sessionId, [
            'type' => 'input',
            'data' => $input,
        ]);
    }

    public function resizeSession(HostingAccount $account, int $userId, string $sessionId, int $cols, int $rows): void
    {
        $this->sessionMetadataFor($account, $userId, $sessionId);
        $this->touchHeartbeat($sessionId);

        $this->appendEvent($sessionId, [
            'type' => 'resize',
            'cols' => $this->normalizeColumns($cols),
            'rows' => $this->normalizeRows($rows),
        ]);
    }

    public function closeSession(HostingAccount $account, int $userId, string $sessionId): void
    {
        $this->sessionMetadataFor($account, $userId, $sessionId);
        $this->touchHeartbeat($sessionId);

        $this->appendEvent($sessionId, [
            'type' => 'close',
        ]);
    }

    public function readWorkerMetadata(string $sessionId): array
    {
        $metadata = $this->readMetadata($sessionId);

        if ($metadata === null) {
            throw new \RuntimeException('Browser terminal session not found.');
        }

        return $metadata;
    }

    public function writeWorkerMetadata(string $sessionId, array $metadata): void
    {
        $this->writeMetadata($sessionId, $metadata);
    }

    public function appendWorkerOutput(string $sessionId, string $output): void
    {
        if ($output === '') {
            return;
        }

        file_put_contents($this->outputLogPath($sessionId), $output, FILE_APPEND | LOCK_EX);
    }

    public function readWorkerEvents(string $sessionId, int &$offset): array
    {
        $path = $this->eventLogPath($sessionId);

        if (! is_file($path)) {
            return [];
        }

        $stream = fopen($path, 'rb');

        if ($stream === false) {
            return [];
        }

        fseek($stream, $offset);
        $payload = (string) stream_get_contents($stream);
        $offset = ftell($stream) ?: $offset;
        fclose($stream);

        $events = [];
        foreach (preg_split("/\r\n|\n|\r/", $payload) as $line) {
            $line = trim($line);
            if ($line === '') {
                continue;
            }

            $decoded = json_decode($line, true);
            if (is_array($decoded)) {
                $events[] = $decoded;
            }
        }

        return $events;
    }

    public function isSessionIdle(array $metadata): bool
    {
        $heartbeatTime = @filemtime($this->heartbeatPath((string) ($metadata['session_id'] ?? '')));

        if ($heartbeatTime === false) {
            return false;
        }

        return (time() - $heartbeatTime) >= self::IDLE_TIMEOUT_SECONDS;
    }

    private function sessionMetadataFor(HostingAccount $account, int $userId, string $sessionId): array
    {
        $metadata = $this->readMetadata($sessionId);

        if ($metadata === null) {
            throw new \RuntimeException('Browser terminal session not found.');
        }

        if (($metadata['account_id'] ?? null) !== $account->id || ($metadata['user_id'] ?? null) !== $userId) {
            throw new \RuntimeException('Browser terminal session not found.');
        }

        return $metadata;
    }

    private function appendEvent(string $sessionId, array $payload): void
    {
        file_put_contents(
            $this->eventLogPath($sessionId),
            json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES).PHP_EOL,
            FILE_APPEND | LOCK_EX
        );
    }

    private function readMetadata(string $sessionId): ?array
    {
        $path = $this->metadataPath($sessionId);

        if (! is_file($path)) {
            return null;
        }

        $decoded = json_decode((string) file_get_contents($path), true);

        return is_array($decoded) ? $decoded : null;
    }

    private function writeMetadata(string $sessionId, array $metadata): void
    {
        file_put_contents(
            $this->metadataPath($sessionId),
            json_encode($metadata, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES),
            LOCK_EX
        );
    }

    private function metadataPath(string $sessionId): string
    {
        return $this->sessionDirectory($sessionId).'/meta.json';
    }

    private function eventLogPath(string $sessionId): string
    {
        return $this->sessionDirectory($sessionId).'/events.ndjson';
    }

    private function outputLogPath(string $sessionId): string
    {
        return $this->sessionDirectory($sessionId).'/output.log';
    }

    private function heartbeatPath(string $sessionId): string
    {
        return $this->sessionDirectory($sessionId).'/heartbeat';
    }

    private function sessionDirectory(string $sessionId): string
    {
        return storage_path('app/browser-terminal-sessions/'.$sessionId);
    }

    private function normalizeColumns(int $cols): int
    {
        return max(40, min($cols, 240));
    }

    private function normalizeRows(int $rows): int
    {
        return max(10, min($rows, 80));
    }

    private function touchHeartbeat(string $sessionId): void
    {
        touch($this->heartbeatPath($sessionId));
    }

    private function buildWorkerCommand(string $sessionId): string
    {
        return sprintf(
            'cd %s && nohup %s artisan hosting:terminal-worker %s >> %s 2>&1 < /dev/null & echo $!',
            escapeshellarg(base_path()),
            escapeshellarg($this->resolvePhpCliBinary()),
            escapeshellarg($sessionId),
            escapeshellarg($this->outputLogPath($sessionId))
        );
    }

    private function resolvePhpCliBinary(): string
    {
        $candidates = array_filter([
            env('LADILL_PHP_CLI_BINARY'),
            $this->isCliBinary(PHP_BINARY) ? PHP_BINARY : null,
            $this->joinBinaryPath(PHP_BINDIR, 'php'),
            $this->joinBinaryPath(PHP_BINDIR, 'php-cli'),
            '/usr/bin/php',
            '/usr/local/bin/php',
        ]);

        foreach ($candidates as $candidate) {
            if ($this->isCliBinary($candidate)) {
                return $candidate;
            }
        }

        return PHP_BINARY;
    }

    private function joinBinaryPath(string $directory, string $binary): string
    {
        return rtrim($directory, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR.$binary;
    }

    private function isCliBinary(?string $path): bool
    {
        if (! is_string($path) || trim($path) === '') {
            return false;
        }

        $basename = strtolower(basename($path));

        if (str_contains($basename, 'fpm') || str_contains($basename, 'cgi')) {
            return false;
        }

        return is_file($path) && is_executable($path);
    }

    private function waitForWorkerStartup(string $sessionId, array $metadata): array
    {
        // The loop returns the moment status leaves "starting" (running OR a
        // genuine error the worker recorded), so a fast boot still returns fast.
        $deadline = microtime(true) + self::STARTUP_TIMEOUT_SECONDS;

        while (microtime(true) < $deadline) {
            usleep(100000);

            $current = $this->readWorkerMetadata($sessionId);

            if (($current['status'] ?? 'starting') !== 'starting') {
                return $current;
            }
        }

        // Still starting after the wait: do NOT fabricate a failure — that also
        // clobbered workers that were about to come up, which is exactly what made
        // healthy terminals report "failed to start". Return current metadata; the
        // browser keeps polling and the worker writes a real error itself if boot
        // ultimately fails.
        return $this->readWorkerMetadata($sessionId);
    }
}