<?php
/**
 * WordPress Native AI Client Service Provider.
 *
 * Integrates with WordPress Core AI Client & Connectors API (WordPress 7.0+).
 *
 * @package AISupportAssistant\Providers
 */

namespace AISupportAssistant\Providers;

use AISupportAssistant\Admin\Settings;
use AISupportAssistant\Helpers\Logger;
use AISupportAssistant\Helpers\ConnectorHelper;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class WordPressAIProvider
 */
class WordPressAIProvider implements EmbeddingProviderInterface, ChatProviderInterface {

	/**
	 * Retrieve settings instance.
	 *
	 * @return Settings
	 */
	private function get_settings(): Settings {
		return Settings::get_instance();
	}

	/**
	 * Check whether WordPress Native AI Client is available on the current site.
	 *
	 * @return bool
	 */
	public static function is_available(): bool {
		return class_exists( '\WordPress\AiClient\AiClient' ) || function_exists( 'wp_ai_client_prompt' );
	}

	/**
	 * Retrieve vector embedding representation of text using configured AI Client connector or plugin API key.
	 *
	 * @param string $text Input text block.
	 * @return array Float vector array.
	 * @throws \Exception If no connector or direct API key is configured or embedding fails.
	 */
	public function get_embedding( string $text ): array {
		Logger::debug( 'Generating embedding via WordPress Native AI Provider' );

		$settings = $this->get_settings();

		// 1. Try Google / Gemini connector from WordPress AI Client registry.
		$google_key = ConnectorHelper::get_connector_api_key( 'google' );
		if ( empty( $google_key ) ) {
			$google_key = ConnectorHelper::get_connector_api_key( 'gemini' );
		}
		if ( ! empty( $google_key ) ) {
			try {
				$gemini_provider = new GeminiProvider( $google_key );
				return $gemini_provider->get_embedding( $text );
			} catch ( \Throwable $e ) {
				Logger::warning( 'Google connector embedding attempt failed: ' . $e->getMessage() );
			}
		}

		// 2. Try OpenAI connector from WordPress AI Client registry.
		$openai_key = ConnectorHelper::get_connector_api_key( 'openai' );
		if ( ! empty( $openai_key ) ) {
			try {
				$openai_provider = new OpenAIProvider( $openai_key );
				return $openai_provider->get_embedding( $text );
			} catch ( \Throwable $e ) {
				Logger::warning( 'OpenAI connector embedding attempt failed: ' . $e->getMessage() );
			}
		}

		// 3. Try direct Gemini key from plugin settings.
		$direct_gemini = $settings->get_secret( 'gemini_api_key' );
		if ( ! empty( $direct_gemini ) ) {
			try {
				$gemini_provider = new GeminiProvider( $direct_gemini );
				return $gemini_provider->get_embedding( $text );
			} catch ( \Throwable $e ) {
				Logger::warning( 'Gemini direct embedding attempt failed: ' . $e->getMessage() );
			}
		}

		// 4. Try direct OpenAI key from plugin settings.
		$direct_openai = $settings->get_secret( 'openai_api_key' );
		if ( ! empty( $direct_openai ) ) {
			try {
				$openai_provider = new OpenAIProvider( $direct_openai );
				return $openai_provider->get_embedding( $text );
			} catch ( \Throwable $e ) {
				Logger::warning( 'OpenAI direct embedding attempt failed: ' . $e->getMessage() );
			}
		}

		Logger::error( 'No API key configured for embedding generation.' );
		throw new \Exception(
			esc_html__(
				'Embedding generation requires an active AI connector or API key. Please configure a connector in WordPress Connectors or enter your API key under AI Support Assistant Settings.',
				'ai-support-assistant'
			)
		);
	}

	/**
	 * Generate a chat completion using the WordPress Native AI Client with context injected.
	 *
	 * @param array  $chunks   Array of relevant document chunks.
	 * @param string $question User query text.
	 * @param array  $history  Recent conversation history.
	 * @return string The generated assistant response.
	 */
	public function generate_response( array $chunks, string $question, array $history = array(), ?callable $on_delta = null ): string {
        $emitted = false;
        if ( $on_delta ) {
            $callback = $on_delta;
            $on_delta = static function ( $text ) use ( $callback, &$emitted ) {
                $emitted = true;
                $callback( $text );
            };
        }
		$settings = $this->get_settings();
		$temp     = (float) $settings->get( 'temperature', 0.2 );
		$max_t    = (int) $settings->get( 'max_tokens', 1000 );

		// Format context documentation blocks.
		$context_str = '';
		foreach ( $chunks as $chunk ) {
			$page_info    = ! empty( $chunk['page_number'] ) ? ' | Page: ' . $chunk['page_number'] : '';
			$context_str .= sprintf(
				"[Document: %s%s]\n%s\n---\n",
				$chunk['filename'] ?? 'Unknown',
				$page_info,
				$chunk['chunk_text']
			);
		}

		// Compile system instruction.
		$custom_instruction = $settings->get(
			'ai_system_instruction',
			"You are a professional customer support assistant.\nAnswer using ONLY the supplied documentation.\nFormat your response cleanly using structured Markdown bullet points (* or -) and bold section titles so it is clean, elegant, and easy to read.\nIf the answer is not found, say:\n\"I couldn't find that information in the uploaded documentation.\"\nDo not invent information."
		);
		$system_prompt      = $custom_instruction . "\n\nDocumentation:\n" . $context_str;

		// Build dialogue context.
		$full_prompt = '';
		if ( ! empty( $history ) ) {
			$full_prompt .= "Recent conversation history:\n";
			foreach ( $history as $turn ) {
				$full_prompt .= 'User: ' . $turn['question'] . "\nAssistant: " . $turn['answer'] . "\n";
			}
			$full_prompt .= "\n";
		}
		$full_prompt .= 'Question: ' . $question;

		Logger::debug( 'Requesting WordPress Native AI Chat response' );
		$last_error = null;

		// 1. Try native wp_ai_client_prompt().
		if ( function_exists( 'wp_ai_client_prompt' ) ) {
			try {
				$builder = wp_ai_client_prompt( $full_prompt );
                foreach ( array(
                    array( 'using_system_instruction', 'usingSystemInstruction', $system_prompt ),
                    array( 'using_temperature', 'usingTemperature', $temp ),
                    array( 'using_max_tokens', 'usingMaxTokens', $max_t ),
                ) as $option ) {
                    $method = self::builder_method( $builder, $option[0], $option[1] );
                    if ( $method ) { $builder->$method( $option[2] ); }
                }

                // Prefer the administrator's selected model instead of an arbitrary registry default.
                $preferences = array();
                if ( ConnectorHelper::get_connector_api_key( 'google' ) ) {
                    $model = trim( (string) $settings->get( 'gemini_chat_model', '' ) );
                    $preferences[] = array( 'google', '' !== $model ? $model : 'gemini-3.1-flash-lite' );
                }
                if ( ConnectorHelper::get_connector_api_key( 'openai' ) ) {
                    $model = trim( (string) $settings->get( 'openai_chat_model', '' ) );
                    $preferences[] = array( 'openai', '' !== $model ? $model : 'gpt-4o-mini' );
                }
                $method = self::builder_method( $builder, 'using_model_preference', 'usingModelPreference' );
                if ( $preferences && $method ) { $builder->$method( ...$preferences ); }

                $method = self::builder_method( $builder, 'generate_text', 'generateText' );
                if ( ! $method ) { throw new \RuntimeException( 'The native AI client does not support text generation.' ); }
                $response_text = $builder->$method();
                if ( is_wp_error( $response_text ) ) {
                    throw new \RuntimeException( esc_html( $response_text->get_error_message() ) );
                }
                if ( ! is_string( $response_text ) || '' === trim( $response_text ) ) {
                    throw new \RuntimeException( 'The native AI client returned an empty answer.' );
                }
                if ( $on_delta ) { $on_delta( trim( $response_text ) ); }
                return trim( $response_text );
			} catch ( \Throwable $e ) {
                if ( $emitted ) { throw $e; }
				$last_error = $e;
				Logger::warning( 'wp_ai_client_prompt failed, attempting connector/plugin fallback: ' . $e->getMessage() );
			}
		}

		// 2. Fallback to Google / Gemini connector key from AI Client registry.
		$google_key = ConnectorHelper::get_connector_api_key( 'google' );
		if ( empty( $google_key ) ) {
			$google_key = ConnectorHelper::get_connector_api_key( 'gemini' );
		}
		if ( ! empty( $google_key ) ) {
			try {
				return ( new GeminiProvider( $google_key ) )->generate_response( $chunks, $question, $history, $on_delta );
			} catch ( \Throwable $e ) {
                if ( $emitted ) { throw $e; }
				$last_error = $e;
				Logger::warning( 'Google connector chat attempt failed: ' . $e->getMessage() );
			}
		}

		// 3. Fallback to OpenAI connector key from AI Client registry.
		$openai_key = ConnectorHelper::get_connector_api_key( 'openai' );
		if ( ! empty( $openai_key ) ) {
			try {
				return ( new OpenAIProvider( $openai_key ) )->generate_response( $chunks, $question, $history, $on_delta );
			} catch ( \Throwable $e ) {
                if ( $emitted ) { throw $e; }
				$last_error = $e;
				Logger::warning( 'OpenAI connector chat attempt failed: ' . $e->getMessage() );
			}
		}

		// 4. Fallback to direct keys in plugin settings.
		$direct_gemini = $settings->get_secret( 'gemini_api_key' );
		if ( ! empty( $direct_gemini ) ) {
			try {
				return ( new GeminiProvider( $direct_gemini ) )->generate_response( $chunks, $question, $history, $on_delta );
			} catch ( \Throwable $e ) {
                if ( $emitted ) { throw $e; }
				$last_error = $e;
				Logger::warning( 'Direct Gemini chat attempt failed: ' . $e->getMessage() );
			}
		}

		$direct_openai = $settings->get_secret( 'openai_api_key' );
		if ( ! empty( $direct_openai ) ) {
			try {
				return ( new OpenAIProvider( $direct_openai ) )->generate_response( $chunks, $question, $history, $on_delta );
			} catch ( \Throwable $e ) {
                if ( $emitted ) { throw $e; }
				$last_error = $e;
				Logger::warning( 'Direct OpenAI chat attempt failed: ' . $e->getMessage() );
			}
		}

		if ( $last_error ) { throw $last_error; }

		throw new \RuntimeException(
			'No available AI provider completed the chat request. Check provider credentials and connection.',
			0,
			$last_error // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Throwable passed as the previous exception, not a message or output.
		);
	}
    /** WordPress forwards snake_case methods through __call; method_exists misses them. */
    private static function builder_method( $builder, string $snake_case, string $camel_case ): string {
        if ( is_callable( array( $builder, $snake_case ) ) ) { return $snake_case; }
        return is_callable( array( $builder, $camel_case ) ) ? $camel_case : '';
    }

}