<?php
/**
 * Adds the "Link Profile" column to WordPress post-list screens.
 *
 * @package Postlinkly
 * @since   1.2.3
 */

declare( strict_types=1 );

namespace Postlinkly\Admin;

use Postlinkly\Database\TableNames;
use Postlinkly\Hooks\ServiceProvider;
use Postlinkly\Indexing\IndexedMarker;
use Postlinkly\Settings\GeneralSettings;
use Postlinkly\Settings\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Adds a "Link Profile" column to the WP admin post-list table.
 *
 * The column shows four pill badges per post:
 *
 *   - Inbound internal links  (blue, arrow-in icon)
 *   - Outbound internal links (green, arrow-out icon)
 *   - External links          (red, diagonal-arrow icon)
 *   - Orphan warning          (amber, triangle icon — only when inbound = 0)
 *
 * Stats are batch-loaded via the `the_posts` filter so the column
 * renderer never issues a query — the whole page costs exactly two
 * GROUP-BY queries regardless of how many posts are listed.
 *
 * The column is added only to the post types the user has configured
 * in Settings → General (default: `post`). Attachment is always
 * excluded.
 *
 * @since 1.2.3
 */
final class PostColumns implements ServiceProvider {

	/**
	 * Column key used in the WP list-table column array.
	 *
	 * @since 1.2.3
	 */
	public const COLUMN_KEY = 'postlinkly_link_profile';

	/**
	 * CSS stylesheet handle.
	 *
	 * @since 1.2.3
	 */
	public const HANDLE_CSS = 'postlinkly-post-columns';

	/**
	 * Runtime cache of per-post link stats for the current page load.
	 *
	 * Populated by `preload_stats()` and read by `render_column()`.
	 * Structure: `[ post_id => [ 'inbound' => int, 'outbound' => int, 'external' => int ] ]`.
	 *
	 * @since 1.2.3
	 *
	 * @var array<int, array{inbound:int, outbound:int, external:int}>
	 */
	private array $stats = array();

	/**
	 * Tracks whether the batch preload has already run for the current
	 * `the_posts` call, preventing duplicate queries on screens that
	 * fire the filter more than once.
	 *
	 * @since 1.2.3
	 *
	 * @var bool
	 */
	private bool $preloaded = false;

	/**
	 * General settings, loaded on first use. See {@see general()}.
	 *
	 * @since 1.18.4
	 *
	 * @var GeneralSettings|null
	 */
	private ?GeneralSettings $general = null;

	/**
	 * Returns the WordPress hooks this service registers.
	 *
	 * @since 1.2.3
	 *
	 * @return array<int, array<int, mixed>>
	 */
	public function get_hooks(): array {
		return array(
			array( 'init', array( $this, 'register_column_hooks' ), 999 ),
			array( 'the_posts', array( $this, 'preload_stats' ) ),
			array( 'admin_enqueue_scripts', array( $this, 'maybe_enqueue_assets' ) ),
		);
	}

	/**
	 * Registers the column-add and column-render callbacks for each
	 * configured post type.
	 *
	 * Runs on `init` at priority 999 so custom post types registered by
	 * other plugins/themes on the default `init` priority are already
	 * available.
	 *
	 * @since 1.2.3
	 * @hook  init
	 *
	 * @return void
	 */
	public function register_column_hooks(): void {
		$post_types = $this->get_configured_post_types();

		foreach ( $post_types as $post_type ) {
			if ( 'attachment' === $post_type ) {
				continue;
			}

			add_filter( "manage_{$post_type}_posts_columns", array( $this, 'add_column' ) );
			add_action( "manage_{$post_type}_posts_custom_column", array( $this, 'render_column' ), 10, 2 );
		}
	}

	/**
	 * Adds the Link Profile column to the end of the column list.
	 *
	 * @since 1.2.3
	 * @hook  manage_{$post_type}_posts_columns
	 *
	 * @param array<string, string> $columns Existing columns.
	 *
	 * @return array<string, string> Modified columns.
	 */
	public function add_column( array $columns ): array {
		$columns[ self::COLUMN_KEY ] = __( 'Link Profile', 'postlinkly' );

		return $columns;
	}

	/**
	 * Renders the Link Profile column content for a single post.
	 *
	 * Reads from the runtime cache populated by `preload_stats()`. If
	 * the post has no cached entry it has not been scanned yet — a
	 * "Not scanned" placeholder is shown.
	 *
	 * @since 1.2.3
	 * @hook  manage_{$post_type}_posts_custom_column
	 *
	 * @param string $column_name Column key being rendered.
	 * @param int    $post_id     Post ID for the current row.
	 *
	 * @return void
	 */
	public function render_column( string $column_name, int $post_id ): void {
		if ( self::COLUMN_KEY !== $column_name ) {
			return;
		}

		if ( ! isset( $this->stats[ $post_id ] ) ) {
			// A draft or scheduled post under the default settings is never
			// scanned, so "Scan" would point at a button that cannot help.
			$post = get_post( $post_id );
			if ( $post instanceof \WP_Post && ! in_array( $post->post_status, $this->general()->post_statuses, true ) ) {
				$this->render_excluded();
				return;
			}

			$this->render_unscanned();
			return;
		}

		$stats = $this->stats[ $post_id ];

		$this->render_badges(
			$post_id,
			$stats['inbound'],
			$stats['outbound'],
			$stats['external']
		);
	}

	/**
	 * Batch-loads link stats for every post on the current list page.
	 *
	 * Fires on the `the_posts` filter. Runs two GROUP-BY queries
	 * (outbound/external by source post, inbound by target post) and
	 * merges the results into the runtime cache. The filter value is
	 * returned unchanged.
	 *
	 * @since 1.2.3
	 * @hook  the_posts
	 *
	 * @param array<int, \WP_Post> $posts Posts about to be displayed.
	 *
	 * @return array<int, \WP_Post> Posts, unchanged.
	 */
	public function preload_stats( array $posts ): array {
		if ( $this->preloaded || array() === $posts ) {
			return $posts;
		}

		$this->preloaded = true;

		global $wpdb;

		if ( ! isset( $wpdb ) ) {
			return $posts;
		}

		$table = TableNames::report_links();

		// Bail silently if the table doesn't exist yet (pre-migration).
		if ( ! $this->table_exists( $table ) ) {
			return $posts;
		}

		$ids = array();
		foreach ( $posts as $post ) {
			$ids[] = (int) $post->ID;
		}

		$placeholders = implode( ',', array_fill( 0, count( $ids ), '%d' ) );

		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Batch load for admin list table; IN-clause placeholders are built from sanitised integers.

		// Outbound internal + external, grouped by source post.
		$outbound_rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT post_id,
				        SUM(CASE WHEN is_internal = 1 THEN 1 ELSE 0 END) AS outbound,
				        SUM(CASE WHEN is_internal = 0 THEN 1 ELSE 0 END) AS external
				 FROM %i
				 WHERE post_id IN ({$placeholders})
				 GROUP BY post_id",
				array_merge( array( $table ), $ids )
			),
			ARRAY_A
		);

		// Inbound internal, grouped by target post.
		$inbound_rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT target_id, COUNT(*) AS inbound
				 FROM %i
				 WHERE is_internal = 1
				   AND target_id IN ({$placeholders})
				 GROUP BY target_id",
				array_merge( array( $table ), $ids )
			),
			ARRAY_A
		);

		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared

		// Build lookup maps.
		$outbound_map = array();
		if ( is_array( $outbound_rows ) ) {
			foreach ( $outbound_rows as $row ) {
				if ( ! is_array( $row ) ) {
					continue;
				}
				$pid = (int) ( $row['post_id'] ?? 0 );
				if ( $pid <= 0 ) {
					continue;
				}
				$outbound_map[ $pid ] = array(
					'outbound' => (int) ( $row['outbound'] ?? 0 ),
					'external' => (int) ( $row['external'] ?? 0 ),
				);
			}
		}

		$inbound_map = array();
		if ( is_array( $inbound_rows ) ) {
			foreach ( $inbound_rows as $row ) {
				if ( ! is_array( $row ) ) {
					continue;
				}
				$pid = (int) ( $row['target_id'] ?? 0 );
				if ( $pid <= 0 ) {
					continue;
				}
				$inbound_map[ $pid ] = (int) ( $row['inbound'] ?? 0 );
			}
		}

		// Merge into the runtime cache. A post has been scanned when it has
		// outgoing links or carries the index marker: a scanned post with no
		// links, or with only incoming ones, has no outgoing rows, so rows
		// alone cannot tell it from one never scanned. A post that is
		// neither is left out of $this->stats and renders as not scanned.
		foreach ( $ids as $pid ) {
			if ( ! isset( $outbound_map[ $pid ] ) && ! IndexedMarker::is_indexed( $pid ) ) {
				continue;
			}

			$this->stats[ $pid ] = array(
				'inbound'  => $inbound_map[ $pid ] ?? 0,
				'outbound' => $outbound_map[ $pid ]['outbound'] ?? 0,
				'external' => $outbound_map[ $pid ]['external'] ?? 0,
			);
		}

		return $posts;
	}

	/**
	 * Enqueues the column stylesheet on post-list screens only.
	 *
	 * @since 1.2.3
	 * @hook  admin_enqueue_scripts
	 *
	 * @param string $hook_suffix Current admin page hook suffix.
	 *
	 * @return void
	 */
	public function maybe_enqueue_assets( string $hook_suffix ): void {
		if ( 'edit.php' !== $hook_suffix ) {
			return;
		}

		$url     = defined( 'POSTLINKLY_PLUGIN_URL' ) ? (string) POSTLINKLY_PLUGIN_URL : '';
		$version = defined( 'POSTLINKLY_VERSION' ) ? (string) POSTLINKLY_VERSION : '1.0.0';

		wp_enqueue_style(
			self::HANDLE_CSS,
			$url . 'assets/css/admin-post-columns.css',
			array(),
			$version
		);
	}

	// -------------------------------------------------------------------------
	// Render helpers
	// -------------------------------------------------------------------------

	/**
	 * Outputs the badge HTML for a post with known stats.
	 *
	 * @since 1.2.3
	 *
	 * @param int $post_id  Post ID (for the AI-count filter).
	 * @param int $inbound  Inbound internal link count.
	 * @param int $outbound Outbound internal link count.
	 * @param int $external External link count.
	 *
	 * @return void
	 */
	private function render_badges( int $post_id, int $inbound, int $outbound, int $external ): void {
		$is_orphaned = 0 === $inbound;

		echo '<div class="pls-stats">';

		// Health dot.
		$health_class = 'pls-health--good';
		if ( $is_orphaned ) {
			$health_class = 'pls-health--orphan';
		} elseif ( 0 === $inbound && 0 === $outbound && 0 === $external ) {
			$health_class = 'pls-health--warning';
		}
		echo '<span class="pls-health ' . esc_attr( $health_class ) . '" title="' . esc_attr( $this->health_title( $health_class ) ) . '"></span>';

		// Inbound (blue, arrow-in).
		$this->render_badge(
			'inbound',
			$inbound,
			__( 'Inbound internal links', 'postlinkly' ),
			$this->icon_arrow_in()
		);

		// Outbound (green, arrow-out).
		$this->render_badge(
			'outbound',
			$outbound,
			__( 'Outbound internal links', 'postlinkly' ),
			$this->icon_arrow_out()
		);

		// External (red, diagonal-arrow).
		$this->render_badge(
			'external',
			$external,
			__( 'External links', 'postlinkly' ),
			$this->icon_external()
		);

		// AI anchors (purple) — shown only when AI-generated links exist.
		// The count is filterable so future schema additions or cache
		// providers can supply it without changing this class.
		$ai_count = (int) apply_filters( 'postlinkly_link_profile_ai_count', 0, $post_id );

		if ( $ai_count > 0 ) {
			$this->render_badge(
				'ai',
				$ai_count,
				__( 'AI-generated anchor links', 'postlinkly' ),
				$this->icon_ai()
			);
		}

		// Orphan warning.
		if ( $is_orphaned ) {
			echo '<span class="pls-stat pls-stat--orphan" data-tip="' . esc_attr__( 'Orphaned — no inbound internal links point to this post', 'postlinkly' ) . '">';
			echo wp_kses( $this->icon_warning(), Icons::allowed_html() );
			echo '</span>';
		}

		echo '</div>';
	}

	/**
	 * Outputs a single stat badge.
	 *
	 * @since 1.2.3
	 *
	 * @param string $type   Badge type modifier (inbound|outbound|external).
	 * @param int    $count  Link count.
	 * @param string $title  Tooltip text.
	 * @param string $svg    SVG icon markup; escaped against Icons::allowed_html().
	 *
	 * @return void
	 */
	private function render_badge( string $type, int $count, string $title, string $svg ): void {
		$zero_class = 0 === $count ? ' pls-stat--zero' : '';
		$tip        = $title . ( 0 === $count ? ' — none' : '' );

		echo '<span class="pls-stat pls-stat--' . esc_attr( $type ) . esc_attr( $zero_class ) . '" data-tip="' . esc_attr( $tip ) . '">';
		echo wp_kses( $svg, Icons::allowed_html() );
		echo esc_html( (string) $count );
		echo '</span>';
	}

	/**
	 * Outputs the "Not scanned" placeholder.
	 *
	 * @since 1.2.3
	 *
	 * @return void
	 */
	private function render_unscanned(): void {
		echo '<div class="pls-stats">';
		echo '<span class="pls-health pls-health--unscanned" title="' . esc_attr__( 'Not scanned yet', 'postlinkly' ) . '"></span>';
		echo '<span class="pls-stat pls-stat--unscanned" data-tip="' . esc_attr__( 'Not scanned yet — saving the post, or the scan in Postlinkly → Tools, reads it', 'postlinkly' ) . '">';
		echo wp_kses( $this->icon_scan(), Icons::allowed_html() );
		echo esc_html__( 'Scan', 'postlinkly' );
		echo '</span>';
		echo '</div>';
	}

	/**
	 * Outputs the placeholder for a post whose status is not scanned.
	 *
	 * @since 1.18.4
	 *
	 * @return void
	 */
	private function render_excluded(): void {
		echo '<div class="pls-stats">';
		echo '<span class="pls-stat pls-stat--excluded" data-tip="' . esc_attr__( 'Not included — only posts with a status chosen in Postlinkly → Settings are scanned', 'postlinkly' ) . '">';
		echo esc_html__( 'Not included', 'postlinkly' );
		echo '</span>';
		echo '</div>';
	}

	// -------------------------------------------------------------------------
	// SVG icons
	// -------------------------------------------------------------------------

	/**
	 * Returns the arrow-in SVG (mirrored arrow-out).
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_arrow_in(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" transform="translate(16, 0) scale(-1, 1)" d="M3.5 2a.5.5 0 0 1 .5.5v3h5.293L7.146 3.354a.5.5 0 1 1 .708-.708l3 3a.5.5 0 0 1 0 .708l-3 3a.5.5 0 0 1-.708-.708L9.293 6.5H4v6.5a.5.5 0 0 1-1 0v-11A.5.5 0 0 1 3.5 2Z"/></svg>';
	}

	/**
	 * Returns the arrow-out SVG.
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_arrow_out(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" d="M3.5 2a.5.5 0 0 1 .5.5v3h5.293L7.146 3.354a.5.5 0 1 1 .708-.708l3 3a.5.5 0 0 1 0 .708l-3 3a.5.5 0 0 1-.708-.708L9.293 6.5H4v6.5a.5.5 0 0 1-1 0v-11A.5.5 0 0 1 3.5 2Z"/></svg>';
	}

	/**
	 * Returns the external-link SVG — a clean diagonal arrow.
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_external(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" d="M8.5 1a.5.5 0 0 0 0 1h5.293L1.646 14.146a.5.5 0 0 0 .708.708L14.5 2.707V8a.5.5 0 0 0 1 0V1.5a.5.5 0 0 0-.5-.5H8.5Z"/></svg>';
	}

	/**
	 * Returns the warning triangle SVG.
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_warning(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" d="M8.982 1.566a1.13 1.13 0 0 0-1.96 0L.165 13.233a1.13 1.13 0 0 0 .982 1.768h13.706a1.13 1.13 0 0 0 .982-1.768L8.982 1.566ZM8 5a.75.75 0 0 1 .75.75v2.5a.75.75 0 0 1-1.5 0v-2.5A.75.75 0 0 1 8 5Zm0 7a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"/></svg>';
	}

	/**
	 * Returns the scan/refresh SVG.
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_scan(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" d="M8 3a4.99 4.99 0 0 0-3.535 8.535.5.5 0 1 1-.707.707A5.99 5.99 0 1 1 8 3Zm0 1a5 5 0 0 1 4.192 7.727.5.5 0 1 1-.838-.545A4 4 0 1 0 4 8a.5.5 0 0 1-1 0 5 5 0 0 1 5-5Z"/></svg>';
	}

	/**
	 * Returns the AI-anchor SVG (info-circle).
	 *
	 * @since 1.2.3
	 *
	 * @return string
	 */
	private function icon_ai(): string {
		return '<svg viewBox="0 0 16 16"><path fill="currentColor" d="M8 1.5A6.5 6.5 0 1 0 14.5 8 6.507 6.507 0 0 0 8 1.5ZM8 11a.75.75 0 1 1 0-1.5.75.75 0 0 1 0 1.5Zm.75-3.5a.75.75 0 1 1-1.5 0v-3a.75.75 0 0 1 1.5 0v3Z"/></svg>';
	}

	// -------------------------------------------------------------------------
	// Helpers
	// -------------------------------------------------------------------------

	/**
	 * Returns the tooltip title for a given health-dot class.
	 *
	 * @since 1.2.3
	 *
	 * @param string $health_class One of the pls-health--* class names.
	 *
	 * @return string
	 */
	private function health_title( string $health_class ): string {
		return match ( $health_class ) {
			'pls-health--orphan'  => __( 'Orphaned — no inbound links', 'postlinkly' ),
			'pls-health--warning' => __( 'Warning — no links found', 'postlinkly' ),
			default               => __( 'Good — this post has inbound links', 'postlinkly' ),
		};
	}

	/**
	 * Returns the list of post types the column should appear on.
	 *
	 * Reads from the plugin's General settings. Falls back to `['post']`
	 * if settings are unavailable.
	 *
	 * @since 1.2.3
	 *
	 * @return array<int, string>
	 */
	private function get_configured_post_types(): array {
		return $this->general()->post_types;
	}

	/**
	 * Returns the General settings, read once per request.
	 *
	 * The status check runs for every row of the posts list, so the settings
	 * are not re-read per row.
	 *
	 * @since 1.18.4
	 *
	 * @return GeneralSettings
	 */
	private function general(): GeneralSettings {
		if ( null === $this->general ) {
			$this->general = ( new Settings() )->general();
		}

		return $this->general;
	}

	/**
	 * Checks whether a database table exists.
	 *
	 * Uses SHOW TABLES so it never triggers a DB error on a fresh
	 * install before migrations have run.
	 *
	 * @since 1.2.3
	 *
	 * @param string $table Fully-qualified table name.
	 *
	 * @return bool
	 */
	private function table_exists( string $table ): bool {
		global $wpdb;

		if ( ! isset( $wpdb ) ) {
			return false;
		}

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Existence check; result not worth caching separately.
		$found = $wpdb->get_var(
			$wpdb->prepare( 'SHOW TABLES LIKE %s', $table )
		);

		return $found === $table;
	}
}