<?php
/**
 * Custom Search API Integration
 *
 * Handles fetching web search results using generic adapters (9Router, Brave, Tavily, Serper)
 *
 * @package WP_Agentic_Writer
 */

if (!defined("ABSPATH")) {
    exit();
}

class WP_Agentic_Writer_Custom_Search_API
{
    /**
     * Get singleton instance.
     *
     * @since 0.1.0
     * @return WP_Agentic_Writer_Custom_Search_API
     */
    public static function get_instance()
    {
        static $instance = null;

        if (null === $instance) {
            $instance = new self();
        }

        return $instance;
    }

    /**
     * Perform a web search based on configured search engine.
     *
     * @since 0.1.0
     * @param string $query Required. The user's search query.
     * @param int    $count Optional. Number of results to return. Default 3.
     * @return array|WP_Error Array of formatted search results, or WP_Error on failure.
     */
    public function search($query, $count = 3)
    {
        $settings = get_option("wp_agentic_writer_settings", []);
        $api_key = $settings["brave_search_api_key"] ?? "";
        $engine = $settings["search_engine"] ?? "9router";
        $base_url = $settings["custom_search_url"] ?? "";

        // Auto fallback to 9Router if not openrouter/auto
        if ($engine === "auto" || $engine === "openrouter") {
            $engine = "9router";
        }

        if (empty($api_key)) {
            return new WP_Error(
                "search_api_key_missing",
                __(
                    "Search API Key is missing. Please configure it in WP Agentic Writer settings under Tools.",
                    "wp-agentic-writer",
                ),
            );
        }

        // Check cache first to prevent burning API limits
        $cache_key =
            "wpaw_custom_search_" . md5($engine . "_" . $query . "_" . $count);
        $cached_results = get_transient($cache_key);
        if (false !== $cached_results) {
            return $cached_results;
        }

        $results = [];

        // -------------------------------------------------------------
        // ADAPTER ROUTING
        // -------------------------------------------------------------
        switch ($engine) {
            case "brave":
                $results = $this->search_brave(
                    $query,
                    $count,
                    $api_key,
                    $base_url,
                );
                break;
            case "tavily":
                $results = $this->search_tavily(
                    $query,
                    $count,
                    $api_key,
                    $base_url,
                );
                break;
            case "serper":
                $results = $this->search_serper(
                    $query,
                    $count,
                    $api_key,
                    $base_url,
                );
                break;
            case "9router":
            default:
                $results = $this->search_9router(
                    $query,
                    $count,
                    $api_key,
                    $base_url,
                );
                break;
        }

        if (is_wp_error($results)) {
            return $results;
        }

        if (empty($results)) {
            return []; // No results found
        }

        // Cache results for 1 hour to prevent redundant API calls
        set_transient($cache_key, $results, HOUR_IN_SECONDS);

        return $results;
    }

    /**
     * Driver: 9Router Proxy (Generic OpenAI-style search endpoint)
     */
    private function search_9router($query, $count, $api_key, $base_url)
    {
        $url = !empty($base_url)
            ? $base_url
            : "http://localhost:20128/v1/search";

        $body = [
            "model" => "gemini", // generic
            "query" => $query,
            "search_type" => "web",
            "max_results" => absint($count),
        ];

        $response = wp_remote_post($url, [
            "headers" => [
                "Content-Type" => "application/json",
                "Authorization" => "Bearer " . $api_key,
            ],
            "body" => wp_json_encode($body),
            "timeout" => 15,
        ]);

        if (is_wp_error($response)) {
            return $response;
        }

        $http_code = wp_remote_retrieve_response_code($response);
        $body_response = json_decode(wp_remote_retrieve_body($response), true);

        if (200 !== $http_code) {
            return new WP_Error(
                "search_error",
                "9Router Search Error: " .
                    ($body_response["error"]["message"] ?? "Unknown"),
            );
        }

        $formatted = [];
        if (
            !empty($body_response["data"]) &&
            is_array($body_response["data"])
        ) {
            foreach ($body_response["data"] as $result) {
                $formatted[] = [
                    "title" => $result["title"] ?? "",
                    "url" => $result["url"] ?? "",
                    "description" =>
                        $result["content"] ?? ($result["description"] ?? ""),
                ];
            }
        }
        return $formatted;
    }

    /**
     * Driver: Tavily API
     */
    private function search_tavily($query, $count, $api_key, $base_url)
    {
        $url = !empty($base_url) ? $base_url : "https://api.tavily.com/search";

        $body = [
            "api_key" => $api_key,
            "query" => $query,
            "search_depth" => "basic",
            "max_results" => absint($count),
        ];

        $response = wp_remote_post($url, [
            "headers" => ["Content-Type" => "application/json"],
            "body" => wp_json_encode($body),
            "timeout" => 15,
        ]);

        if (is_wp_error($response)) {
            return $response;
        }

        $http_code = wp_remote_retrieve_response_code($response);
        $body_response = json_decode(wp_remote_retrieve_body($response), true);

        if (200 !== $http_code) {
            return new WP_Error(
                "search_error",
                "Tavily Search Error: " .
                    ($body_response["detail"] ?? "Unknown"),
            );
        }

        $formatted = [];
        if (
            !empty($body_response["results"]) &&
            is_array($body_response["results"])
        ) {
            foreach ($body_response["results"] as $result) {
                $formatted[] = [
                    "title" => $result["title"] ?? "",
                    "url" => $result["url"] ?? "",
                    "description" => $result["content"] ?? "",
                ];
            }
        }
        return $formatted;
    }

    /**
     * Driver: Serper.dev
     */
    private function search_serper($query, $count, $api_key, $base_url)
    {
        $url = !empty($base_url)
            ? $base_url
            : "https://google.serper.dev/search";

        $body = [
            "q" => $query,
            "num" => absint($count),
        ];

        $response = wp_remote_post($url, [
            "headers" => [
                "Content-Type" => "application/json",
                "X-API-KEY" => $api_key,
            ],
            "body" => wp_json_encode($body),
            "timeout" => 15,
        ]);

        if (is_wp_error($response)) {
            return $response;
        }

        $http_code = wp_remote_retrieve_response_code($response);
        $body_response = json_decode(wp_remote_retrieve_body($response), true);

        if (200 !== $http_code) {
            return new WP_Error(
                "search_error",
                "Serper Search Error: " .
                    ($body_response["message"] ?? "Unknown"),
            );
        }

        $formatted = [];
        if (
            !empty($body_response["organic"]) &&
            is_array($body_response["organic"])
        ) {
            foreach ($body_response["organic"] as $result) {
                $formatted[] = [
                    "title" => $result["title"] ?? "",
                    "url" => $result["link"] ?? "",
                    "description" => $result["snippet"] ?? "",
                ];
            }
        }
        return $formatted;
    }

    /**
     * Driver: Brave Search API
     */
    private function search_brave($query, $count, $api_key, $base_url)
    {
        $base = !empty($base_url)
            ? $base_url
            : "https://api.search.brave.com/res/v1/web/search";
        $url = add_query_arg(
            [
                "q" => urlencode($query),
                "count" => absint($count),
                "text_decorations" => 0,
                "spellcheck" => 1,
            ],
            $base,
        );

        $response = wp_remote_get($url, [
            "headers" => [
                "Accept" => "application/json",
                "Accept-Encoding" => "gzip",
                "X-Subscription-Token" => $api_key,
            ],
            "timeout" => 15,
        ]);

        if (is_wp_error($response)) {
            return $response;
        }

        $http_code = wp_remote_retrieve_response_code($response);
        $body_response = json_decode(wp_remote_retrieve_body($response), true);

        if (200 !== $http_code) {
            return new WP_Error(
                "search_error",
                "Brave Search Error: " .
                    ($body_response["message"] ?? "Unknown"),
            );
        }

        $formatted = [];
        if (
            !empty($body_response["web"]["results"]) &&
            is_array($body_response["web"]["results"])
        ) {
            foreach ($body_response["web"]["results"] as $result) {
                $formatted[] = [
                    "title" => $result["title"] ?? "",
                    "url" => $result["url"] ?? "",
                    "description" => $result["description"] ?? "",
                ];
            }
        }
        return $formatted;
    }

    /**
     * Formats search results into a markdown context block for LLM System Prompt injection.
     *
     * @since 0.1.0
     * @param array  $results Search results array.
     * @param string $query   Original query.
     * @return string Formatted markdown context string.
     */
    public function format_results_for_llm($results, $query)
    {
        if (empty($results) || is_wp_error($results)) {
            return "No reliable web search results found for: {$query}";
        }

        $markdown = "## LIVE WEB SEARCH CONTEXT\n";
        $markdown .= "> You successfully searched the internet for: \"{$query}\"\n";
        $markdown .=
            "> Please incorporate the following real-time data into your answer:\n\n";

        $counter = 1;
        foreach ($results as $item) {
            $markdown .= "{$counter}. **{$item["title"]}**\n";
            $markdown .= "   URL: {$item["url"]}\n";
            $markdown .= "   Summary: {$item["description"]}\n\n";
            $counter++;
        }

        $markdown .= "---------------------------\n";

        return $markdown;
    }
}