<?php
declare(strict_types=1);

namespace app\common\service;

/** Request-local numeric telemetry. Raw events, prompts, titles, URLs and IDs never leave it. */
final class DifyStreamTiming
{
    private const EVENTS = ['workflow_started', 'workflow_finished', 'node_started', 'node_finished',
        'message', 'agent_message', 'agent_thought', 'message_end', 'error', 'ping', 'choices'];
    private const TYPES = ['start', 'llm', 'knowledge-retrieval', 'tool', 'code', 'template-transform',
        'if-else', 'answer', 'end', 'agent', 'http-request', 'iteration', 'question-classifier',
        'variable-aggregator', 'parameter-extractor'];
    private \Closure $clock;
    private float $started;
    private array $metrics = [];
    private array $events = [];
    private array $nodes = [];
    private array $nodePositions = [];

    public function __construct(?callable $clock = null)
    {
        $this->clock = $clock === null ? static fn (): float => hrtime(true) / 1e6 : \Closure::fromCallable($clock);
        $this->started = ($this->clock)();
    }

    private function elapsed(): int { return max(0, (int) floor(($this->clock)() - $this->started)); }

    public function headers(int $status): void
    {
        $this->metrics['first_header_ms'] ??= $this->elapsed();
        if ($status >= 200 && $status <= 599) $this->metrics['final_header_ms'] ??= $this->elapsed();
    }

    public function body(int $bytes): void
    {
        if ($bytes <= 0) return;
        $this->metrics['first_body_ms'] ??= $this->elapsed();
    }

    public function frame(array $decoded, string $protocol): void
    {
        $this->metrics['first_frame_ms'] ??= $this->elapsed();
        $name = $protocol === 'dify' ? ($decoded['event'] ?? 'other') : (isset($decoded['choices']) ? 'choices' : 'other');
        if (!is_string($name) || !in_array($name, self::EVENTS, true)) $name = 'other';
        $now = $this->elapsed();
        $this->events[$name] ??= ['first_ms' => $now, 'last_ms' => $now, 'count' => 0];
        ++$this->events[$name]['count']; $this->events[$name]['last_ms'] = $now;
        if (in_array($name, ['message', 'agent_message', 'choices'], true)) {
            $answer = $protocol === 'dify' ? ($decoded['answer'] ?? '') : ($decoded['choices'][0]['delta']['content'] ?? '');
            $visible = is_string($answer) && $answer !== '';
            // Chat Completions also supports text-part arrays. Match the parser's
            // accepted shape without retaining or concatenating clinical content.
            if ($protocol !== 'dify' && is_array($answer)) {
                foreach ($answer as $part) {
                    if (is_array($part) && ($part['type'] ?? '') === 'text'
                        && is_string($part['text'] ?? null) && $part['text'] !== '') { $visible = true; break; }
                }
            }
            if ($visible) $this->metrics['first_answer_ms'] ??= $now;
        }
        if (in_array($name, ['node_started', 'node_finished'], true)) {
            $data = is_array($decoded['data'] ?? null) ? $decoded['data'] : [];
            $id = $data['id'] ?? $data['node_id'] ?? '';
            if (is_string($id) && $id !== '' && strlen($id) <= 512) {
                $key = hash('sha256', $id);
                if (!isset($this->nodePositions[$key]) && count($this->nodes) >= 128) return;
                if (!isset($this->nodePositions[$key])) {
                    $this->nodePositions[$key] = count($this->nodes);
                    $type = $data['node_type'] ?? 'other';
                    $this->nodes[] = ['type' => is_string($type) && in_array($type, self::TYPES, true) ? $type : 'other'];
                }
                $position = $this->nodePositions[$key];
                $field = $name === 'node_started' ? 'start_ms' : 'finish_ms';
                $this->nodes[$position][$field] ??= $now;
                $elapsed = $data['elapsed_time'] ?? null;
                if (is_numeric($elapsed) && is_finite((float) $elapsed) && (float) $elapsed >= 0) {
                    $this->nodes[$position]['provider_elapsed_ms'] = (int) min(3600000, (float) $elapsed * 1000);
                }
            }
        }
        $usage = $name === 'message_end' ? ($decoded['metadata']['usage'] ?? []) : ($decoded['usage'] ?? []);
        foreach (['prompt_tokens', 'completion_tokens', 'total_tokens', 'reasoning_tokens'] as $key) {
            $value = is_array($usage) ? ($usage[$key] ?? null) : null;
            if (is_numeric($value) && is_finite((float) $value) && (float) $value >= 0) {
                $this->metrics[$key] = (int) min(1000000000, (float) $value);
            }
        }
    }

    public function delivered(): void { $this->metrics['first_delivered_ms'] ??= $this->elapsed(); }

    public function transport(array $values): void
    {
        foreach (['connect_ms', 'tls_ms', 'header_ttfb_ms', 'transfer_ms', 'http_status', 'curl_errno'] as $key) {
            $value = $values[$key] ?? null;
            if ((is_float($value) || is_int($value)) && is_finite((float) $value) && $value >= 0) {
                $this->metrics[$key] = (int) min(3600000, $value);
            }
        }
    }

    public function snapshot(): array
    {
        return ['duration_ms' => $this->elapsed()] + $this->metrics + ['events' => $this->events, 'nodes' => $this->nodes];
    }
}