<?php
/**
 * Comments app — the model: what the rail and the conversation read,
 * and what each dispatched action does to the state.
 *
 * Reads go through the in-process REST proxy against `wp/v2/comments`
 * — the same collection, the same `openstation_*` fields and the same
 * filterable `_fields` projection a browser would fetch — so a row
 * here is byte-identical to a row there. Writes go through the
 * operations in `rest.php`, shared with the public routes.
 *
 * @package OpenStation
 */

namespace OpenStation\Apps\Comments;

use OpenStation\App\Os;
use OpenStation\App\State;

defined( 'ABSPATH' ) || exit;

/**
 * Fields the conversation pane renders for a thread message —
 * narrower than the rail's projection: a thread message needs no
 * post title or link (the head carries them for the root) beyond the
 * root's own row, and no per-row moderation flag (the viewer's cap is
 * a config fact).
 */
const THREAD_FIELDS = 'id,post,parent,author,author_name,author_avatar_urls,date_gmt,content,status,'
	. 'openstation_post_title,openstation_post_link,openstation_can_edit';

/**
 * The most thread pages fetched for one conversation (100 rows each).
 * A post with more replies than that is a forum, not a comment thread;
 * the pane says "showing the first N" rather than paging forever.
 */
const THREAD_MAX_PAGES = 10;

/**
 * `tab` → `wp/v2/comments` `status`. Single values only: the collection
 * declares `status` as a `sanitize_key` string, which silently STRIPS
 * commas, so a comma list reaches `WP_Comment_Query` as one nonsense
 * status and returns an empty list with a 200. `all` is approved AND
 * pending (not spam/trash); `any` is every status.
 *
 * @param string $tab Tab value.
 * @return string
 */
function status_for_tab( $tab ) {
	switch ( (string) $tab ) {
		case 'all':
			return 'all';
		case 'spam':
			return 'spam';
		case 'trash':
			return 'trash';
		case 'mine':
			// Every status the viewer authored on; the author filter
			// is applied by the caller.
			return 'any';
		default:
			return 'hold';
	}
}

/**
 * The rail's query: the filtered default args (`per_page` included —
 * `openstation_comments_window_query_args` is where the page size is
 * set), then the tab, page, search, viewer (Mine), post scope, and
 * `parent=0` — the rail lists conversations, so it asks the server for
 * roots rather than client-filtering a mixed page (a page of nothing
 * but replies used to render an empty rail while the badge still
 * counted them).
 *
 * @param State $state State.
 * @return array<string,mixed>
 */
function rail_query( State $state ) {
	$query = \openstation_comments_window_default_query_args();
	unset( $query['status'] );
	$tab             = (string) $state->get( 'tab' );
	$query['status'] = status_for_tab( $tab );
	$query['page']   = max( 1, (int) $state->get( 'page' ) );
	$search          = trim( (string) $state->get( 'search' ) );
	if ( '' !== $search ) {
		$query['search'] = $search;
	}
	// `author`, `post` and `parent` are array params on the collection
	// (`author__in`, `post__in`, `parent__in`); `parent = [0]` is a
	// non-empty array, so the `comment_parent IN (0)` clause applies.
	if ( 'mine' === $tab && get_current_user_id() > 0 ) {
		$query['author'] = array( get_current_user_id() );
	}
	$post = (int) $state->get( 'post' );
	if ( $post > 0 ) {
		$query['post'] = array( $post );
	}
	$query['parent'] = array( 0 );
	return $query;
}

/**
 * The identity of the rail's result set — what the client's page
 * accumulation is keyed on. `gen` is bumped by every mutation that
 * moves rows between views, so a moderation or a reply starts the
 * accumulation clean from page 1.
 *
 * @param State $state State.
 * @return string
 */
function rail_key( State $state ) {
	return implode(
		'|',
		array(
			(string) $state->get( 'tab' ),
			trim( (string) $state->get( 'search' ) ),
			(string) (int) $state->get( 'post' ),
			(string) (int) $state->get( 'gen' ),
		)
	);
}

/**
 * Direct-reply counts for a set of comment ids in ONE grouped query —
 * the `openstation_replies_count` field costs a COUNT per row, which
 * on a 20-row page is twenty queries for one number each. Counts the
 * approved and pending replies, what `get_comments( status => 'all' )`
 * counts.
 *
 * @param int[] $ids Parent comment ids.
 * @return array<int,int> `id => count`, every id present.
 */
function reply_counts( array $ids ) {
	global $wpdb;
	$ids = array_values( array_unique( array_filter( array_map( 'intval', $ids ) ) ) );
	$out = array_fill_keys( $ids, 0 );
	if ( array() === $ids ) {
		return $out;
	}
	$placeholders = implode( ',', array_fill( 0, count( $ids ), '%d' ) );
	$rows         = $wpdb->get_results(
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- `$placeholders` is a list of `%d`; the values are bound below.
		$wpdb->prepare(
			"SELECT comment_parent, COUNT(*) AS n FROM {$wpdb->comments} WHERE comment_parent IN ( $placeholders ) AND comment_approved IN ( '1', '0' ) GROUP BY comment_parent",
			$ids
		),
		ARRAY_A
	);
	foreach ( (array) $rows as $row ) {
		$out[ (int) $row['comment_parent'] ] = (int) $row['n'];
	}
	return $out;
}

/**
 * The rail page for a state, memoised per dispatch so an action that
 * needs the rows (to auto-select) and `data()` share one query (the
 * memo is dropped when `data()` has read it — a later dispatch in the
 * same process, as in a test, starts clean). The reply counts ride
 * each row as `openstation_replies_count`, from one grouped query
 * rather than the per-row REST field.
 *
 * @param State|null $state State; null forgets the memo.
 * @return array{items:array<int,mixed>,total:int,pages:int,page:int,perPage:int,error:string,code:string}
 */
function rail( ?State $state ) {
	static $memo = array();
	if ( null === $state ) {
		$memo = array();
		return array();
	}
	$query = rail_query( $state );
	$key   = (string) wp_json_encode( $query );
	if ( ! isset( $memo[ $key ] ) ) {
		$page   = \openstation_app_rest_page( 'wp/v2/comments', $query );
		$counts = reply_counts( array_map( 'intval', wp_list_pluck( $page['items'], 'id' ) ) );
		foreach ( $page['items'] as $i => $row ) {
			$page['items'][ $i ]['openstation_replies_count'] = $counts[ (int) ( $row['id'] ?? 0 ) ] ?? 0;
		}
		$memo[ $key ] = $page;
	}
	return $memo[ $key ];
}

/**
 * Every comment on the selected conversation's post (all depths, all
 * statuses), paged in 100s — the conversation pane builds the nested
 * tree from it. `status=any` is the vocabulary for "no status clause
 * at all", so a spam or trashed reply still renders in context; it is
 * a protected collection param requiring `edit_posts`, the cap the app
 * is gated on. Null when nothing is selected or the read failed (the
 * client then paints the root alone).
 *
 * @param int $selected Selected root comment id.
 * @return array{rows:array<int,mixed>,truncated:bool}|null
 */
function thread( $selected ) {
	$selected = (int) $selected;
	if ( $selected <= 0 ) {
		return null;
	}
	$root = get_comment( $selected );
	if ( ! $root instanceof \WP_Comment ) {
		return null;
	}
	$query = \openstation_comments_window_default_query_args();
	unset( $query['status'], $query['parent'], $query['_fields'] );
	$query['post']     = array( (int) $root->comment_post_ID );
	$query['per_page'] = 100;
	$query['orderby']  = 'date';
	$query['order']    = 'asc';
	$query['status']   = 'any';
	$query['_fields']  = THREAD_FIELDS;

	$rows  = array();
	$pages = 1;
	for ( $page = 1; $page <= $pages && $page <= THREAD_MAX_PAGES; $page++ ) {
		$query['page'] = $page;
		$result        = \openstation_app_rest( 'GET', 'wp/v2/comments', $query );
		if ( ! $result['ok'] || ! is_array( $result['data'] ) ) {
			return 1 === $page
				? null
				: array(
					'rows'      => $rows,
					'truncated' => true,
				);
		}
		$rows  = array_merge( $rows, array_values( $result['data'] ) );
		$pages = max( 1, (int) $result['pages'] );
	}
	// The tree build relies on sibling order being chronological —
	// make that a property of this function rather than of the query.
	usort(
		$rows,
		static function ( $a, $b ) {
			return strcmp( (string) ( $a['date_gmt'] ?? '' ), (string) ( $b['date_gmt'] ?? '' ) );
		}
	);
	return array(
		'rows'      => $rows,
		'truncated' => $pages > THREAD_MAX_PAGES,
	);
}

/**
 * The halves of `data()` an action knows it left untouched — `select`
 * changes the thread but not the rail, Load more the rail but not the
 * thread. A skipped half is omitted from the response and the client
 * keeps what it has. Scoped to one dispatch: `data()`, which runs at
 * the end of every dispatch, reads the marks and clears them.
 *
 * @param string|null $half `rail` | `thread` to mark, `'take'` to read and clear.
 * @return array<string,bool>
 */
function skipped( $half = null ) {
	static $skip = array();
	if ( 'take' === $half ) {
		$taken = $skip;
		$skip  = array();
		return $taken;
	}
	if ( null !== $half ) {
		$skip[ $half ] = true;
	}
	return $skip;
}

/**
 * Everything the client view paints from.
 *
 * @param State $state State.
 * @return array<string,mixed>
 */
function data( State $state ) {
	$skip = skipped( 'take' );
	$out  = array( 'counts' => \openstation_comments_window_counts() );
	if ( empty( $skip['rail'] ) ) {
		$out['rail']    = rail( $state );
		$out['railKey'] = rail_key( $state );
	}
	if ( empty( $skip['thread'] ) ) {
		$out['thread'] = thread( (int) $state->get( 'selected' ) );
	}
	rail( null );
	return $out;
}

// ---------------------------------------------------------------- actions

/**
 * Start a fresh result set: page 1, a new accumulation key.
 *
 * @param State $state State.
 */
function restart( State $state ) {
	$state->set( 'page', 1 );
	$state->set( 'gen', (int) $state->get( 'gen' ) + 1 );
}

/**
 * Keep the selection honest against page 1: a conversation that left
 * the view gives way to the first one still in it, and an empty view
 * clears it.
 *
 * @param State $state State.
 */
function auto_select( State $state ) {
	if ( 1 !== (int) $state->get( 'page' ) ) {
		return;
	}
	$items    = rail( $state )['items'];
	$selected = (int) $state->get( 'selected' );
	foreach ( $items as $row ) {
		if ( isset( $row['id'] ) && (int) $row['id'] === $selected ) {
			return;
		}
	}
	$first = isset( $items[0]['id'] ) ? (int) $items[0]['id'] : 0;
	$state->set( 'selected', $first );
}

/**
 * Scope the rail to the `post` open-time param — the
 * `edit-comments.php?p=<id>` deep link. A scoped open starts on "All"
 * so the post's whole thread is visible, not just its pending
 * comments; `0` (a plain open) clears the scope.
 *
 * @param State $state State.
 * @param Os    $os    Host handle.
 */
function scope_from_params( State $state, Os $os ) {
	$post = max( 0, (int) $os->param( 'post', 0 ) );
	$state->set( 'post', $post );
	if ( $post > 0 ) {
		$state->set( 'tab', 'all' );
	}
	restart( $state );
	auto_select( $state );
}

/**
 * `mount` — the first render.
 *
 * @param State $state State.
 * @param Os    $os    Host handle.
 */
function mount( State $state, Os $os ) {
	scope_from_params( $state, $os );
}

/**
 * `reopen` — a live window asked to open again. Only a CHANGED scope
 * re-scopes: a dock click, which reopens with the scope the window
 * already has, keeps its pages and its selection.
 *
 * @param State $state State.
 * @param Os    $os    Host handle.
 */
function reopen_action( State $state, Os $os ) {
	if ( max( 0, (int) $os->param( 'post', 0 ) ) === (int) $state->get( 'post' ) ) {
		return;
	}
	scope_from_params( $state, $os );
}

/**
 * `filter` — the tab, the search or the post scope changed (the bound
 * value already rode up with the state; `post` may also arrive as an
 * argument, from the scope banner's Show all).
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  Args.
 */
function filter_action( State $state, Os $os, array $args ) {
	if ( array_key_exists( 'post', $args ) ) {
		$state->set( 'post', max( 0, (int) $args['post'] ) );
	}
	restart( $state );
	auto_select( $state );
}

/**
 * `page` — Load more: the next rail page joins the accumulation. The
 * thread on screen did not change; it is left out of the response.
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  `page`.
 */
function page_action( State $state, Os $os, array $args ) {
	$state->set( 'page', max( 1, (int) ( $args['page'] ?? 1 ) ) );
	skipped( 'thread' );
}

/**
 * `select` — read this conversation. The rail did not change; it is
 * left out of the response.
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  `id`.
 */
function select_action( State $state, Os $os, array $args ) {
	$state->set( 'selected', max( 0, (int) ( $args['id'] ?? 0 ) ) );
	skipped( 'rail' );
}

/**
 * `moderate` — approve / unapprove / spam / unspam / trash / untrash.
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  `ids`, `action`.
 * @throws \RuntimeException When refused or nothing could be processed.
 */
function moderate_action( State $state, Os $os, array $args ) {
	if ( ! $os->can( 'moderate_comments' ) ) {
		throw new \RuntimeException( esc_html__( 'You are not allowed to moderate comments.', 'desktop-mode' ) );
	}
	$verb   = (string) ( $args['action'] ?? '' );
	$result = \openstation_comments_window_moderate( (array) ( $args['ids'] ?? array() ), $verb );
	if ( is_wp_error( $result ) ) {
		throw new \RuntimeException( esc_html( $result->get_error_message() ) );
	}
	if ( array() === $result['processed'] ) {
		throw new \RuntimeException( esc_html__( 'Action failed.', 'desktop-mode' ) );
	}
	$changes = array(
		'trash'   => 'trashed',
		'spam'    => 'trashed',
		'untrash' => 'untrashed',
		'unspam'  => 'untrashed',
	);
	$os->announce( 'comment', $changes[ $verb ] ?? 'updated', $result['processed'] );
	restart( $state );
	auto_select( $state );
}

/**
 * `reply` — post a reply under a comment.
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  `parent`, `content`.
 * @throws \RuntimeException When refused.
 */
function reply_action( State $state, Os $os, array $args ) {
	if ( ! $os->can( 'edit_posts' ) ) {
		throw new \RuntimeException( esc_html__( 'You are not allowed to reply.', 'desktop-mode' ) );
	}
	$result = \openstation_comments_window_create_reply( (int) ( $args['parent'] ?? 0 ), (string) ( $args['content'] ?? '' ) );
	if ( is_wp_error( $result ) ) {
		throw new \RuntimeException( esc_html( $result->get_error_message() ) );
	}
	$os->announce( 'comment', 'created', array( (int) $result['id'] ) );
	restart( $state );
	auto_select( $state );
}

/**
 * `edit` — rewrite a comment's body, through the core controller so
 * its sanitisation and its per-target permission stay the truth. The
 * rows keep their places (a rewrite moves nothing between views), so
 * the accumulation is left alone: the thread and the current rail
 * page come back fresh, the pages before it keep their text until the
 * next reload.
 *
 * @param State               $state State.
 * @param Os                  $os    Host handle.
 * @param array<string,mixed> $args  `id`, `content`.
 * @throws \RuntimeException When refused or the write failed.
 */
function edit_action( State $state, Os $os, array $args ) {
	$id      = (int) ( $args['id'] ?? 0 );
	$content = (string) ( $args['content'] ?? '' );
	if ( $id <= 0 || ! $os->can( 'edit_comment', $id ) ) {
		throw new \RuntimeException( esc_html__( 'You are not allowed to edit this comment.', 'desktop-mode' ) );
	}
	if ( \openstation_comments_window_is_blank( $content ) ) {
		throw new \RuntimeException( esc_html__( 'A comment cannot be empty.', 'desktop-mode' ) );
	}
	$result = \openstation_app_rest( 'POST', 'wp/v2/comments/' . $id, array(), array( 'content' => $content ) );
	if ( ! $result['ok'] ) {
		throw new \RuntimeException( esc_html( '' !== $result['error'] ? $result['error'] : __( 'Edit failed.', 'desktop-mode' ) ) );
	}
	$os->announce( 'comment', 'updated', array( $id ) );
}