<?php
/**
 * MLS Grid API Client
 *
 * Handles all communication with the MLS Grid API including:
 * - Authentication (Bearer token)
 * - Gzip compression (required)
 * - Pagination via @odata.nextLink
 * - Rate limit compliance
 * - Error handling and retries
 */

if (!defined('ABSPATH')) {
    exit;
}

class MLS_API_Client {

    /**
     * Default records per page (max 5000 without expand, 1000 with expand)
     */
    const DEFAULT_TOP = 1000;
    const MAX_TOP_WITH_EXPAND = 1000;
    const MAX_TOP_NO_EXPAND = 5000;

    /**
     * Request timeout in seconds
     */
    const TIMEOUT = 60;

    /**
     * Max retry attempts
     */
    const MAX_RETRIES = 3;

    /**
     * Options instance
     */
    private $options;

    /**
     * Rate limiter instance
     */
    private $rate_limiter;

    /**
     * Logger instance
     */
    private $logger;

    /**
     * Constructor
     *
     * @param MLS_Options $options Options instance
     * @param MLS_Rate_Limiter $rate_limiter Rate limiter instance
     * @param MLS_Logger $logger Logger instance
     */
    public function __construct(MLS_Options $options, MLS_Rate_Limiter $rate_limiter, MLS_Logger $logger) {
        $this->options = $options;
        $this->rate_limiter = $rate_limiter;
        $this->logger = $logger;
    }

    /**
     * Test API connection
     *
     * @return array Result with success status and message
     */
    public function test_connection() {
        $start_time = microtime(true);

        $response = $this->request('');

        $elapsed = round((microtime(true) - $start_time) * 1000);

        if (is_wp_error($response)) {
            return array(
                'success' => false,
                'error' => $response->get_error_message(),
                'response_time' => $elapsed,
            );
        }

        return array(
            'success' => true,
            'message' => 'Connection successful',
            'response_time' => $elapsed,
            'endpoints' => isset($response['value']) ? array_column($response['value'], 'name') : array(),
        );
    }

    /**
     * Test API authentication
     *
     * @return array Result with success status
     */
    public function test_auth() {
        // Try to fetch a single property to verify auth
        $response = $this->get_properties(null, null, 1);

        if (is_wp_error($response)) {
            $error_code = $response->get_error_code();
            $error_message = $response->get_error_message();

            if (strpos($error_message, '401') !== false || strpos($error_message, 'Unauthorized') !== false) {
                return array(
                    'success' => false,
                    'error' => 'Authentication failed. Please check your API token.',
                );
            }

            return array(
                'success' => false,
                'error' => $error_message,
            );
        }

        return array(
            'success' => true,
            'message' => 'Authentication successful',
            'originating_system' => $this->options->get_originating_system(),
        );
    }

    /**
     * Make an API request
     *
     * @param string $endpoint API endpoint (relative to base URL)
     * @param array $params Query parameters
     * @param int $retry Current retry attempt
     * @param string $channel Rate limit channel ('general' or 'image')
     * @return array|WP_Error Response data or error
     */
    public function request($endpoint, $params = array(), $retry = 0, $channel = 'general') {
        // Check and wait for rate limits (uses global advisory lock coordination)
        $this->rate_limiter->check_and_wait(true, $channel);

        $url = $this->build_url($endpoint, $params);

        $this->logger->debug('API Request', array(
            'url' => $url,
            'retry' => $retry,
        ));

        $args = array(
            'method' => 'GET',
            'timeout' => self::TIMEOUT,
            'headers' => array(
                'Authorization' => 'Bearer ' . $this->options->get_api_token(),
                'Accept' => 'application/json',
                'Accept-Encoding' => 'gzip',
                'User-Agent' => 'MLS-by-HansonXyz/' . MLS_PLUGIN_VERSION . ' WordPress/' . get_bloginfo('version'),
            ),
        );

        $response = wp_remote_get($url, $args);

        // Track the request
        $bytes = 0;
        if (!is_wp_error($response)) {
            $body = wp_remote_retrieve_body($response);
            $bytes = strlen($body);
        }
        $this->rate_limiter->record_request($bytes);

        // Handle errors
        if (is_wp_error($response)) {
            $this->logger->error('API Request Failed', array(
                'error' => $response->get_error_message(),
                'url' => $url,
            ));

            // Retry on transient errors
            if ($retry < self::MAX_RETRIES) {
                sleep(pow(2, $retry)); // Exponential backoff
                return $this->request($endpoint, $params, $retry + 1, $channel);
            }

            return $response;
        }

        $status_code = wp_remote_retrieve_response_code($response);
        $body = wp_remote_retrieve_body($response);

        // Handle HTTP errors
        if ($status_code >= 400) {
            $error_message = $this->parse_error_response($body, $status_code);

            $this->logger->error('API HTTP Error', array(
                'status' => $status_code,
                'error' => $error_message,
                'url' => $url,
            ));

            // Retry on 429 (rate limit) or 5xx errors
            if (($status_code === 429 || $status_code >= 500) && $retry < self::MAX_RETRIES) {
                $wait = $status_code === 429 ? 60 : pow(2, $retry);
                sleep($wait);
                return $this->request($endpoint, $params, $retry + 1, $channel);
            }

            return new WP_Error('api_error', $error_message, array('status' => $status_code));
        }

        // Parse JSON response
        $data = json_decode($body, true);

        if (json_last_error() !== JSON_ERROR_NONE) {
            $this->logger->error('API JSON Parse Error', array(
                'error' => json_last_error_msg(),
                'body_preview' => substr($body, 0, 500),
            ));
            return new WP_Error('json_error', 'Failed to parse API response: ' . json_last_error_msg());
        }

        $this->logger->debug('API Response', array(
            'status' => $status_code,
            'record_count' => isset($data['value']) ? count($data['value']) : 0,
            'has_next' => isset($data['@odata.nextLink']),
        ));

        return $data;
    }

    /**
     * Build full URL with parameters
     *
     * @param string $endpoint Endpoint
     * @param array $params Parameters
     * @return string Full URL
     */
    private function build_url($endpoint, $params = array()) {
        $base_url = rtrim($this->options->get_api_url(), '/');

        if (!empty($endpoint)) {
            $url = $base_url . '/' . ltrim($endpoint, '/');
        } else {
            $url = $base_url . '/';
        }

        if (!empty($params)) {
            $query_string = http_build_query($params, '', '&', PHP_QUERY_RFC3986);
            // OData uses $ prefix which gets encoded, decode it
            $query_string = str_replace('%24', '$', $query_string);
            $url .= '?' . $query_string;
        }

        return $url;
    }

    /**
     * Parse error response
     *
     * @param string $body Response body
     * @param int $status_code HTTP status code
     * @return string Error message
     */
    private function parse_error_response($body, $status_code) {
        $data = json_decode($body, true);

        if (isset($data['error']['message'])) {
            return $data['error']['message'];
        }

        if (isset($data['message'])) {
            return $data['message'];
        }

        return "HTTP Error {$status_code}";
    }

    /**
     * Get properties from API
     *
     * @param string|null $filter OData filter
     * @param string|null $expand Expand parameter (Media, Rooms, UnitTypes)
     * @param int|null $top Number of records to fetch
     * @return array|WP_Error Response data or error
     */
    public function get_properties($filter = null, $expand = null, $top = null) {
        $params = array();

        // Build filter - always include originating system
        $system = $this->options->get_originating_system();
        $base_filter = "OriginatingSystemName eq '{$system}'";

        if ($filter) {
            $params['$filter'] = $base_filter . ' and ' . $filter;
        } else {
            $params['$filter'] = $base_filter . ' and MlgCanView eq true';
        }

        // Expand for media
        if ($expand) {
            $params['$expand'] = $expand;
        }

        // Records per page
        if ($top) {
            $params['$top'] = min($top, $expand ? self::MAX_TOP_WITH_EXPAND : self::MAX_TOP_NO_EXPAND);
        } else {
            $params['$top'] = $expand ? self::MAX_TOP_WITH_EXPAND : self::DEFAULT_TOP;
        }

        return $this->request('Property', $params);
    }

    /**
     * Get properties modified since timestamp
     *
     * @param string $timestamp ISO 8601 timestamp
     * @param string|null $expand Expand parameter
     * @param int|null $top Number of records
     * @return array|WP_Error Response data or error
     */
    public function get_properties_since($timestamp, $expand = null, $top = null) {
        $filter = "ModificationTimestamp gt {$timestamp}";
        return $this->get_properties($filter, $expand, $top);
    }

    /**
     * Get properties for initial sync (Active/Pending only)
     *
     * @param string|null $expand Expand parameter
     * @param int|null $top Number of records
     * @return array|WP_Error Response data or error
     */
    public function get_properties_for_initial_sync($expand = null, $top = null) {
        $params = array();

        $system = $this->options->get_originating_system();

        // Initial sync: only Active/Pending with MlgCanView=true
        $params['$filter'] = "OriginatingSystemName eq '{$system}' and MlgCanView eq true and (StandardStatus eq 'Active' or StandardStatus eq 'Pending')";

        if ($expand) {
            $params['$expand'] = $expand;
        }

        if ($top) {
            $params['$top'] = min($top, $expand ? self::MAX_TOP_WITH_EXPAND : self::MAX_TOP_NO_EXPAND);
        } else {
            $params['$top'] = $expand ? self::MAX_TOP_WITH_EXPAND : self::DEFAULT_TOP;
        }

        return $this->request('Property', $params);
    }

    /**
     * Get properties modified since timestamp (for replication)
     *
     * Does NOT filter by MlgCanView or StandardStatus so we can detect:
     * - Records that became unavailable (MlgCanView=false)
     * - Records that changed status (Active -> Sold)
     *
     * @param string $timestamp ISO 8601 modification timestamp
     * @param string|null $expand Expand parameter
     * @param int|null $top Number of records
     * @return array|WP_Error Response data or error
     */
    public function get_properties_for_replication($timestamp, $expand = null, $top = null) {
        $params = array();

        $system = $this->options->get_originating_system();

        // Replication: get ALL changes since timestamp (no MlgCanView or Status filter)
        $params['$filter'] = "OriginatingSystemName eq '{$system}' and ModificationTimestamp gt {$timestamp}";

        if ($expand) {
            $params['$expand'] = $expand;
        }

        if ($top) {
            $params['$top'] = min($top, $expand ? self::MAX_TOP_WITH_EXPAND : self::MAX_TOP_NO_EXPAND);
        } else {
            $params['$top'] = $expand ? self::MAX_TOP_WITH_EXPAND : self::DEFAULT_TOP;
        }

        return $this->request('Property', $params);
    }

    /**
     * Get a single property by listing ID with media
     *
     * Used to refresh media URLs for a specific listing without
     * fetching the entire dataset. Uses the 'image' rate limit channel
     * with a 2-second interval for on-demand image requests.
     *
     * Note: MLS Grid only allows filtering by ListingId (not ListingKey)
     * for the Property resource. The caller must provide the listing_id.
     *
     * @param string $listing_id The MLS listing ID (not listing_key)
     * @return array|WP_Error Property data with Media or error
     */
    public function get_property_media($listing_id) {
        $params = array();

        $system = $this->options->get_originating_system();

        // Filter by ListingId (MLS Grid only allows certain fields for filtering)
        $params['$filter'] = "OriginatingSystemName eq '{$system}' and ListingId eq '{$listing_id}'";
        $params['$expand'] = 'Media';
        $params['$top'] = 1;

        // Use 'image' channel with 2-second rate limiting for on-demand media fetches
        $response = $this->request('Property', $params, 0, 'image');

        if (is_wp_error($response)) {
            return $response;
        }

        // Return first result or null
        if (isset($response['value']) && !empty($response['value'])) {
            return $response['value'][0];
        }

        return null;
    }

    /**
     * Get multiple properties by listing IDs with media (batched)
     *
     * Fetches up to 25 properties in a single API request using OData 'in' filter.
     * Used for efficient media URL refresh without making individual API calls.
     * Uses the 'image' rate limit channel with 2-second interval.
     *
     * @param array $listing_ids Array of MLS listing IDs (max 25)
     * @return array|WP_Error Array of property data with Media, or error
     */
    public function get_properties_by_ids($listing_ids) {
        if (empty($listing_ids)) {
            return array('value' => array());
        }

        // Limit to 25 (MLS Grid's max with $expand)
        $listing_ids = array_slice($listing_ids, 0, 25);

        $params = array();
        $system = $this->options->get_originating_system();

        // Build 'in' filter: ListingId in ('ID1', 'ID2', 'ID3')
        $escaped_ids = array_map(function($id) {
            return "'" . addslashes($id) . "'";
        }, $listing_ids);
        $in_list = implode(',', $escaped_ids);

        $params['$filter'] = "OriginatingSystemName eq '{$system}' and ListingId in ({$in_list})";
        $params['$expand'] = 'Media';
        $params['$top'] = 25;

        // Use 'image' channel with 2-second rate limiting for media fetches
        return $this->request('Property', $params, 0, 'image');
    }

    /**
     * Get next page of results
     *
     * @param string $next_link The @odata.nextLink URL
     * @return array|WP_Error Response data or error
     */
    public function get_next_page($next_link) {
        // Check and wait for rate limits
        $this->rate_limiter->check_and_wait(true);

        $this->logger->debug('API Next Page Request', array(
            'url' => $next_link,
        ));

        $args = array(
            'method' => 'GET',
            'timeout' => self::TIMEOUT,
            'headers' => array(
                'Authorization' => 'Bearer ' . $this->options->get_api_token(),
                'Accept' => 'application/json',
                'Accept-Encoding' => 'gzip',
                'User-Agent' => 'MLS-by-HansonXyz/' . MLS_PLUGIN_VERSION . ' WordPress/' . get_bloginfo('version'),
            ),
        );

        $response = wp_remote_get($next_link, $args);

        // Track the request
        $bytes = 0;
        if (!is_wp_error($response)) {
            $body = wp_remote_retrieve_body($response);
            $bytes = strlen($body);
        }
        $this->rate_limiter->record_request($bytes);

        if (is_wp_error($response)) {
            $this->logger->error('API Next Page Failed', array(
                'error' => $response->get_error_message(),
            ));
            return $response;
        }

        $status_code = wp_remote_retrieve_response_code($response);
        $body = wp_remote_retrieve_body($response);

        if ($status_code >= 400) {
            $error_message = $this->parse_error_response($body, $status_code);
            return new WP_Error('api_error', $error_message, array('status' => $status_code));
        }

        $data = json_decode($body, true);

        if (json_last_error() !== JSON_ERROR_NONE) {
            return new WP_Error('json_error', 'Failed to parse API response');
        }

        return $data;
    }

    /**
     * Get members (agents) from API
     *
     * @param string|null $filter OData filter
     * @return array|WP_Error Response data or error
     */
    public function get_members($filter = null) {
        $params = array();

        $system = $this->options->get_originating_system();
        $base_filter = "OriginatingSystemName eq '{$system}'";

        if ($filter) {
            $params['$filter'] = $base_filter . ' and ' . $filter;
        } else {
            $params['$filter'] = $base_filter;
        }

        return $this->request('Member', $params);
    }

    /**
     * Get offices from API
     *
     * @param string|null $filter OData filter
     * @return array|WP_Error Response data or error
     */
    public function get_offices($filter = null) {
        $params = array();

        $system = $this->options->get_originating_system();
        $base_filter = "OriginatingSystemName eq '{$system}'";

        if ($filter) {
            $params['$filter'] = $base_filter . ' and ' . $filter;
        } else {
            $params['$filter'] = $base_filter;
        }

        return $this->request('Office', $params);
    }

    /**
     * Get lookup values (field definitions)
     * Note: Should not be called more than once per day
     *
     * @return array|WP_Error Response data or error
     */
    public function get_lookups() {
        $system = $this->options->get_originating_system();
        $params = array(
            '$filter' => "OriginatingSystemName eq '{$system}'",
        );

        return $this->request('Lookup', $params);
    }
}