<?php

declare(strict_types=1);

namespace Infrastructure\AI;

use RuntimeException;

/**
 * RAG (Retrieval-Augmented Generation) Chat Service.
 *
 * Provides a complete RAG pipeline that:
 * 1. Converts questions to embeddings using Ollama
 * 2. Searches for relevant document chunks in Qdrant
 * 3. Builds context from search results
 * 4. Generates answers using Claude or Ollama
 * 5. Returns structured responses with sources and metadata
 *
 * This service orchestrates the interaction between OllamaService,
 * QdrantService, and ClaudeService to implement a production-ready
 * RAG system for document-based question answering.
 *
 * @package Infrastructure\AI
 * @author  System Generated
 * @version 1.0.0
 */
final readonly class ChatService
{
    /**
     * Constructs a new ChatService instance.
     *
     * @param OllamaService $ollama Ollama service for embeddings and optional LLM
     * @param QdrantService $qdrant Qdrant service for vector search
     * @param ClaudeService $claude Claude service for high-quality LLM responses
     */
    public function __construct(
        private OllamaService $ollama,
        private QdrantService $qdrant,
        private ClaudeService $claude
    ) {
    }

    /**
     * Executes a complete RAG chat pipeline.
     *
     * Performs the following steps:
     * 1. Generates an embedding vector for the question
     * 2. Searches for similar documents in the vector database
     * 3. Builds context from the most relevant chunks
     * 4. Generates an answer using the specified LLM model
     * 5. Extracts source information
     * 6. Assembles a structured response
     *
     * @param string      $question           The user's question to answer
     * @param string      $model              The LLM model (claude-* or ollama:*)
     * @param string      $collection         The Qdrant collection to search in (default: documents)
     * @param int         $limit              Maximum number of document chunks to retrieve (default: 5)
     * @param string|null $stylePrompt        Optional style prompt from author profile
     * @param string|null $customSystemPrompt Optional custom system prompt (replaces default if set)
     * @param float       $temperature        Sampling temperature 0.0-1.0 (default: 0.7)
     * @param int         $maxTokens          Maximum tokens in response (default: 4096)
     *
     * @return array{
     *     question: string,
     *     answer: string,
     *     sources: array<int, array{title: string, score: float, content?: string}>,
     *     model: string,
     *     usage?: array{input_tokens: int, output_tokens: int},
     *     chunks_used: int
     * } Complete chat response with answer, sources, and metadata
     *
     * @throws RuntimeException If embedding generation fails
     * @throws RuntimeException If vector search fails
     * @throws RuntimeException If no relevant documents are found
     * @throws RuntimeException If LLM request fails
     *
     * @example
     * $chat = new ChatService($ollama, $qdrant, $claude);
     * $result = $chat->chat('Was ist systemisches Coaching?', 'claude-opus-4-5-20251101', 'documents', 5, null, null, 0.7, 4096);
     * // Returns: [
     * //   'question' => 'Was ist systemisches Coaching?',
     * //   'answer' => 'Systemisches Coaching ist...',
     * //   'sources' => [
     * //     ['title' => 'Coaching Grundlagen', 'score' => 0.89],
     * //     ['title' => 'Systemische Methoden', 'score' => 0.76]
     * //   ],
     * //   'model' => 'claude-opus-4-5-20251101',
     * //   'usage' => ['input_tokens' => 234, 'output_tokens' => 567],
     * //   'chunks_used' => 5
     * // ]
     */
    public function chat(
        string $question,
        string $model = 'claude-opus-4-5-20251101',
        string $collection = 'documents',
        int $limit = 5,
        ?string $stylePrompt = null,
        ?string $customSystemPrompt = null,
        float $temperature = 0.7,
        int $maxTokens = 4096
    ): array {
        // Step 1: Generate embedding for the question
        try {
            $queryEmbedding = $this->ollama->getEmbedding($question);
        } catch (RuntimeException $e) {
            throw new RuntimeException(
                'Embedding generation failed: ' . $e->getMessage(),
                0,
                $e
            );
        }

        if ($queryEmbedding === []) {
            throw new RuntimeException('Embedding generation returned empty vector');
        }

        // Step 2: Search for relevant document chunks
        try {
            $searchResults = $this->qdrant->search($queryEmbedding, $collection, $limit);
        } catch (RuntimeException $e) {
            throw new RuntimeException(
                'Vector search failed: ' . $e->getMessage(),
                0,
                $e
            );
        }

        if ($searchResults === []) {
            throw new RuntimeException('No relevant documents found for the question');
        }

        // Step 3: Build context from search results
        $context = $this->buildContext($searchResults);

        // Step 4: Parse model string and generate answer
        $isOllama = str_starts_with($model, 'ollama:');
        $isClaude = str_starts_with($model, 'claude-');

        if ($isClaude) {
            try {
                $ragPrompt = $this->claude->buildRagPrompt($question, $context);

                // Build system prompt hierarchy: Default -> Custom -> Style
                if ($customSystemPrompt !== null && $customSystemPrompt !== '') {
                    $systemPrompt = $customSystemPrompt;
                } else {
                    $systemPrompt = $this->claude->getDefaultSystemPrompt();
                }

                // Append style prompt from author profile if provided
                if ($stylePrompt !== null && $stylePrompt !== '') {
                    $systemPrompt .= "\n\n" . $stylePrompt;
                }

                $llmResponse = $this->claude->ask($ragPrompt, $systemPrompt, $model, $maxTokens, $temperature);

                $answer = $llmResponse['text'];
                $usage = $llmResponse['usage'];
            } catch (RuntimeException $e) {
                throw new RuntimeException(
                    'Claude API request failed: ' . $e->getMessage(),
                    0,
                    $e
                );
            }
        } elseif ($isOllama) {
            try {
                // Extract actual model name (remove "ollama:" prefix)
                $ollamaModel = substr($model, 7);

                // Build instruction from custom prompt and style
                $instructions = [];
                if ($customSystemPrompt !== null && $customSystemPrompt !== '') {
                    $instructions[] = $customSystemPrompt;
                }
                if ($stylePrompt !== null && $stylePrompt !== '') {
                    $instructions[] = $stylePrompt;
                }
                $instructionBlock = $instructions !== [] ? implode("\n\n", $instructions) . "\n\n" : '';

                $ragPrompt = sprintf(
                    "%sKontext aus den Dokumenten:\n\n%s\n\n---\n\nFrage: %s",
                    $instructionBlock,
                    $context,
                    $question
                );
                $answer = $this->ollama->generate($ragPrompt, $ollamaModel, $temperature);
                $usage = null;
            } catch (RuntimeException $e) {
                throw new RuntimeException(
                    'Ollama generation failed: ' . $e->getMessage(),
                    0,
                    $e
                );
            }
        } else {
            throw new RuntimeException(
                sprintf('Unknown model "%s". Use claude-* or ollama:* format.', $model)
            );
        }

        // Step 5: Extract source information
        $sources = $this->extractSources($searchResults);

        // Step 6: Assemble response
        $response = [
            'question' => $question,
            'answer' => $answer,
            'sources' => $sources,
            'model' => $model,
            'chunks_used' => count($searchResults),
        ];

        if ($usage !== null) {
            $response['usage'] = $usage;
        }

        return $response;
    }

    /**
     * Builds a context string from search results.
     *
     * Concatenates the content from multiple search results into a single
     * context string, respecting a maximum character limit. Each chunk is
     * labeled with its source document title.
     *
     * @param array<int, array{id: int|string, score: float, payload: array<string, mixed>}> $searchResults Vector search results
     * @param int                                                                             $maxTokens     Maximum tokens to include (default: 3000)
     *
     * @return string The built context string
     */
    private function buildContext(array $searchResults, int $maxTokens = 3000): string
    {
        $contextParts = [];
        $totalChars = 0;
        $maxChars = $maxTokens * 4; // Approximate: 1 token ~ 4 characters

        foreach ($searchResults as $index => $result) {
            $payload = $result['payload'];
            $content = (string) ($payload['content'] ?? '');
            $docTitle = (string) ($payload['document_title'] ?? 'Unbekannt');

            // Check if adding this chunk would exceed the limit
            if ($totalChars + strlen($content) > $maxChars) {
                break;
            }

            $contextParts[] = sprintf('[Quelle %d: %s]%s%s', $index + 1, $docTitle, "\n", $content);
            $totalChars += strlen($content);
        }

        return implode("\n\n---\n\n", $contextParts);
    }

    /**
     * Extracts unique source information from search results.
     *
     * Collects document titles and scores from the search results,
     * deduplicating by title to provide a clean list of sources.
     * Optionally includes content preview if available.
     *
     * @param array<int, array{id: int|string, score: float, payload: array<string, mixed>}> $searchResults Vector search results
     *
     * @return array<int, array{title: string, score: float, content?: string}> Deduplicated source information
     */
    private function extractSources(array $searchResults): array
    {
        $sources = [];
        $seen = [];

        foreach ($searchResults as $result) {
            $payload = $result['payload'];
            $docTitle = (string) ($payload['document_title'] ?? '');

            // Skip empty titles or already seen titles
            if ($docTitle === '' || isset($seen[$docTitle])) {
                continue;
            }

            $source = [
                'title' => $docTitle,
                'score' => round($result['score'], 3),
            ];

            // Optionally include content preview
            if (isset($payload['content']) && is_string($payload['content'])) {
                $source['content'] = $payload['content'];
            }

            $sources[] = $source;
            $seen[$docTitle] = true;
        }

        return $sources;
    }
}