<?php
/**
 * The week in plain words.
 *
 * @package Dealroot
 */

namespace Dealroot;

defined( 'ABSPATH' ) || exit;

/**
 * A few sentences about the last seven days compared with the seven before: how many leads came,
 * which channel brought most and which changed, where visitors turn into leads most often, a
 * form that many people give up, and leads that still wait for an answer. Shown on the overview
 * and sent with the weekly summary, by email and on Telegram.
 */
class Insights {

	/**
	 * Fewest leads of a channel before it is named as the one that brought most.
	 */
	const MIN_LEADS = 2;

	/**
	 * Fewest visits of a channel before its conversion rate is compared.
	 */
	const MIN_VISITS = 30;

	/**
	 * Fewest form starts before a form is named as given up often.
	 */
	const MIN_STARTS = 10;

	/**
	 * Sentences about the week, most useful first.
	 *
	 * @param bool $waiting Include the leads that wait for an answer, which the overview shows
	 *                      elsewhere.
	 * @return array<int, array{key: string, tone: string, text: string, url: string}>
	 */
	public static function week( $waiting = true ) {
		$now      = time();
		$current  = array( gmdate( 'Y-m-d H:i:s', $now - 7 * DAY_IN_SECONDS ), gmdate( 'Y-m-d H:i:s', $now ) );
		$previous = array( gmdate( 'Y-m-d H:i:s', $now - 14 * DAY_IN_SECONDS ), $current[0] );
		$this_wk  = self::leads_by_channel( $current[0], $current[1] );
		$last_wk  = self::leads_by_channel( $previous[0], $previous[1] );
		$leads    = array_sum( $this_wk );
		$before   = array_sum( $last_wk );
		$items    = array();

		if ( $waiting ) {
			$open = self::waiting();
			if ( $open ) {
				$items[] = self::item(
					'waiting',
					'todo',
					/* translators: %s: number of leads */
					sprintf( _n( '%s new lead has waited more than a day for an answer.', '%s new leads have waited more than a day for an answer.', $open, 'dealroot' ), number_format_i18n( $open ) ),
					admin_url( 'admin.php?page=dealroot-leads&status=new' )
				);
			}
		}

		if ( 0 === $leads && 0 === $before ) {
			return $items;
		}

		$items[] = self::leads_sentence( $leads, $before );

		$won = self::won( $current[0], $current[1] );
		if ( $won['count'] ) {
			$items[] = self::item(
				'won',
				'good',
				sprintf(
					/* translators: 1: number of customers, 2: amount such as €2,400 */
					_n( '%1$s lead became a customer, worth %2$s.', '%1$s leads became customers, worth %2$s.', $won['count'], 'dealroot' ),
					number_format_i18n( $won['count'] ),
					Admin\Format::money_list( $won['revenue'] )
				)
			);
		}

		// The channel that brought most, then the one that changed most.
		arsort( $this_wk );
		$top = (string) key( $this_wk );

		if ( $this_wk && $this_wk[ $top ] >= self::MIN_LEADS && $leads > $this_wk[ $top ] ) {
			$items[] = self::item(
				'top',
				'info',
				sprintf(
					/* translators: 1: channel such as Organic search, 2: leads of the channel, 3: all leads */
					__( 'Most enquiries came from %1$s: %2$s of %3$s.', 'dealroot' ),
					Attribution::channel_label( $top ),
					number_format_i18n( $this_wk[ $top ] ),
					number_format_i18n( $leads )
				)
			);
		}

		$asked = Ai::topics( $current[0], $current[1] );
		$topic = (string) key( $asked );

		if ( '' !== $topic && $asked[ $topic ]['leads'] >= self::MIN_LEADS ) {
			$items[] = self::item(
				'topic',
				'info',
				sprintf(
					/* translators: 1: topic of enquiries, 2: number of leads, 3: all leads */
					__( 'Most asked about: %1$s, in %2$s of %3$s enquiries.', 'dealroot' ),
					$topic,
					number_format_i18n( $asked[ $topic ]['leads'] ),
					number_format_i18n( $leads )
				)
			);
		}

		$change = self::biggest_change( $this_wk, $last_wk );
		if ( $change ) {
			$items[] = self::item(
				'change',
				$change[1] > 0 ? 'good' : 'bad',
				sprintf(
					/* translators: 1: channel such as Paid search, 2: number of leads */
					$change[1] > 0 ? _n( '%1$s brought %2$s more lead than the week before.', '%1$s brought %2$s more leads than the week before.', abs( $change[1] ), 'dealroot' ) : _n( '%1$s brought %2$s lead fewer than the week before.', '%1$s brought %2$s leads fewer than the week before.', abs( $change[1] ), 'dealroot' ),
					Attribution::channel_label( $change[0] ),
					number_format_i18n( abs( $change[1] ) )
				)
			);
		}

		$best = self::best_rate( $this_wk, $current[0], $current[1] );
		if ( $best ) {
			$items[] = self::item(
				'rate',
				'info',
				sprintf(
					/* translators: 1: channel such as Organic search, 2: percentage, 3: number of visits */
					__( 'Visitors from %1$s turn into leads most often: %2$s of %3$s visits.', 'dealroot' ),
					Attribution::channel_label( $best['channel'] ),
					number_format_i18n( $best['rate'] * 100, $best['rate'] < 0.1 ? 1 : 0 ) . '%',
					number_format_i18n( $best['visits'] )
				)
			);
		}

		$form = self::given_up( $current[0], $current[1] );
		if ( $form ) {
			$text = sprintf(
				/* translators: 1: number of people, 2: name of the form, 3: number who sent it */
				__( '%1$s people started “%2$s”, but only %3$s sent it.', 'dealroot' ),
				number_format_i18n( $form['starts'] ),
				$form['name'],
				number_format_i18n( $form['sent'] )
			);

			if ( '' !== $form['field'] ) {
				/* translators: %s: label of a form field */
				$text .= ' ' . sprintf( __( 'Most stopped at “%s”.', 'dealroot' ), $form['field'] );
			}

			$items[] = self::item( 'form', 'bad', $text );
		}

		$city = self::top_city( $current[0], $current[1] );
		if ( $city ) {
			$items[] = self::item(
				'city',
				'info',
				sprintf(
					/* translators: 1: city, 2: number of leads */
					__( 'Most leads came from %1$s (%2$s).', 'dealroot' ),
					$city['name'],
					number_format_i18n( $city['leads'] )
				)
			);
		}

		/**
		 * Filters the sentences about the week.
		 *
		 * @param array $items Items with key, tone (good, bad, info or todo), text and url.
		 */
		return array_slice( (array) apply_filters( 'dealroot_insights', $items ), 0, 8 );
	}

	/**
	 * One sentence.
	 *
	 * @param string $key  Kind.
	 * @param string $tone good, bad, info or todo.
	 * @param string $text Text.
	 * @param string $url  Link, optional.
	 * @return array
	 */
	private static function item( $key, $tone, $text, $url = '' ) {
		return array(
			'key'  => $key,
			'tone' => $tone,
			'text' => $text,
			'url'  => $url,
		);
	}

	/**
	 * The number of leads compared with the week before.
	 *
	 * @param int $leads  This week.
	 * @param int $before The week before.
	 * @return array
	 */
	private static function leads_sentence( $leads, $before ) {
		/* translators: %s: number of leads */
		$count = sprintf( _n( '%s lead in the last 7 days', '%s leads in the last 7 days', $leads, 'dealroot' ), number_format_i18n( $leads ) );
		$diff  = $leads - $before;

		if ( 0 === $before ) {
			return self::item( 'leads', 'good', $count . '.' );
		}

		if ( 0 === $diff ) {
			return self::item( 'leads', 'info', $count . ', ' . __( 'as many as the week before.', 'dealroot' ) );
		}

		return self::item(
			'leads',
			$diff > 0 ? 'good' : 'bad',
			$count . ', ' . sprintf(
				/* translators: %s: number of leads */
				$diff > 0 ? _n( '%s more than the week before.', '%s more than the week before.', abs( $diff ), 'dealroot' ) : _n( '%s fewer than the week before.', '%s fewer than the week before.', abs( $diff ), 'dealroot' ),
				number_format_i18n( abs( $diff ) )
			)
		);
	}

	/**
	 * Leads per channel of a period, without spam.
	 *
	 * @param string $from UTC start.
	 * @param string $to   UTC end.
	 * @return array<string, int>
	 */
	private static function leads_by_channel( $from, $to ) {
		global $wpdb;

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT channel, COUNT(*) AS total FROM %i WHERE status <> 'spam' AND created_at >= %s AND created_at < %s GROUP BY channel",
				Installer::table(),
				$from,
				$to
			)
		);

		$counts = array();
		foreach ( (array) $rows as $row ) {
			$counts[ (string) $row->channel ] = (int) $row->total;
		}

		return $counts;
	}

	/**
	 * Deals won in a period, with their value per currency.
	 *
	 * @param string $from UTC start.
	 * @param string $to   UTC end.
	 * @return array{count: int, revenue: array<string, float>}
	 */
	private static function won( $from, $to ) {
		global $wpdb;

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT currency, COUNT(*) AS total, SUM(COALESCE(value, 0)) AS revenue FROM %i WHERE status = 'won' AND won_at >= %s AND won_at < %s GROUP BY currency",
				Installer::table(),
				$from,
				$to
			)
		);

		$won = array(
			'count'   => 0,
			'revenue' => array(),
		);

		foreach ( (array) $rows as $row ) {
			$won['count'] += (int) $row->total;
			if ( (float) $row->revenue > 0 ) {
				$currency                    = '' !== (string) $row->currency ? (string) $row->currency : (string) Settings::get( 'currency' );
				$won['revenue'][ $currency ] = ( $won['revenue'][ $currency ] ?? 0 ) + (float) $row->revenue;
			}
		}

		return $won;
	}

	/**
	 * New leads of the last 30 days that wait more than a day for an answer.
	 *
	 * @return int
	 */
	private static function waiting() {
		global $wpdb;

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		return (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(*) FROM %i WHERE status = 'new' AND form_plugin <> 'manual' AND created_at >= %s AND created_at < %s",
				Installer::table(),
				gmdate( 'Y-m-d H:i:s', time() - 30 * DAY_IN_SECONDS ),
				gmdate( 'Y-m-d H:i:s', time() - DAY_IN_SECONDS )
			)
		);
	}

	/**
	 * The channel whose leads changed most, when the change is worth a sentence.
	 *
	 * @param array $now    Leads per channel this week.
	 * @param array $before Leads per channel the week before.
	 * @return array{0: string, 1: int}|null Channel and change.
	 */
	private static function biggest_change( array $now, array $before ) {
		$best = null;

		foreach ( array_unique( array_merge( array_keys( $now ), array_keys( $before ) ) ) as $channel ) {
			$diff = ( $now[ $channel ] ?? 0 ) - ( $before[ $channel ] ?? 0 );

			if ( abs( $diff ) >= 3 && ( ! $best || abs( $diff ) > abs( $best[1] ) ) ) {
				$best = array( (string) $channel, $diff );
			}
		}

		return $best;
	}

	/**
	 * The channel whose visitors send an enquiry most often.
	 *
	 * @param array  $leads Leads per channel.
	 * @param string $from  UTC start.
	 * @param string $to    UTC end.
	 * @return array{channel: string, rate: float, visits: int}|null
	 */
	private static function best_rate( array $leads, $from, $to ) {
		if ( ! Settings::get( 'count_visits' ) ) {
			return null;
		}

		$visits = (array) Visits::counts( $from, $to, 'channel' );
		$best   = null;
		$ranked = 0;

		foreach ( $visits as $channel => $count ) {
			$count = (int) $count;
			$sent  = (int) ( $leads[ $channel ] ?? 0 );

			if ( $count < self::MIN_VISITS || $sent < self::MIN_LEADS ) {
				continue;
			}

			++$ranked;
			$rate = min( 1, $sent / $count );

			if ( ! $best || $rate > $best['rate'] ) {
				$best = array(
					'channel' => (string) $channel,
					'rate'    => $rate,
					'visits'  => $count,
				);
			}
		}

		// With a single channel to compare there is nothing to tell.
		return $ranked > 1 ? $best : null;
	}

	/**
	 * The form that most people start and then leave, when fewer than half send it.
	 *
	 * @param string $from UTC start.
	 * @param string $to   UTC end.
	 * @return array{name: string, starts: int, sent: int, field: string}|null
	 */
	private static function given_up( $from, $to ) {
		if ( ! Settings::get( 'form_stats' ) ) {
			return null;
		}

		foreach ( Form_Stats::report( $from, $to, 5 ) as $name => $form ) {
			if ( $form['starts'] >= self::MIN_STARTS && $form['sent'] < $form['starts'] / 2 ) {
				return array(
					'name'   => (string) $name,
					'starts' => $form['starts'],
					'sent'   => $form['sent'],
					'field'  => $form['field_left'] >= 2 ? $form['field'] : '',
				);
			}
		}

		return null;
	}

	/**
	 * The city most leads came from, when it brought at least three.
	 *
	 * @param string $from UTC start.
	 * @param string $to   UTC end.
	 * @return array{name: string, leads: int}|null
	 */
	private static function top_city( $from, $to ) {
		global $wpdb;

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$row = $wpdb->get_row(
			$wpdb->prepare(
				"SELECT country, city, COUNT(*) AS total FROM %i WHERE status <> 'spam' AND city <> '' AND created_at >= %s AND created_at < %s GROUP BY country, city ORDER BY total DESC LIMIT 1",
				Installer::table(),
				$from,
				$to
			)
		);

		if ( ! $row || (int) $row->total < 3 ) {
			return null;
		}

		return array(
			'name'  => Geo::clean_city( (string) $row->city ),
			'leads' => (int) $row->total,
		);
	}

	/**
	 * The sentences as a Telegram message.
	 *
	 * @param array      $items Items of week().
	 * @param array|null $coach Advice of the AI assistant, optional.
	 * @return string HTML subset of Telegram.
	 */
	public static function telegram( array $items, $coach = null ) {
		$esc   = static function ( $text ) {
			return htmlspecialchars( (string) $text, ENT_NOQUOTES, 'UTF-8' );
		};
		$lines = array(
			/* translators: %s: site name */
			'<b>' . $esc( sprintf( __( 'Your week – %s', 'dealroot' ), wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES ) ) ) . '</b>',
			'',
		);

		if ( ! empty( $coach['advice'] ) ) {
			$lines[] = $esc( $coach['advice'] );

			if ( '' !== (string) ( $coach['focus'] ?? '' ) ) {
				$lines[] = '<b>' . $esc( __( 'Worth doing next', 'dealroot' ) ) . ':</b> ' . $esc( $coach['focus'] );
			}

			$lines[] = '';
		}

		foreach ( $items as $item ) {
			$lines[] = '• ' . $esc( $item['text'] );
		}

		$lines[] = '';
		$lines[] = '<a href="' . esc_url( admin_url( 'admin.php?page=dealroot' ) ) . '">' . $esc( __( 'Open the overview', 'dealroot' ) ) . '</a>';

		return implode( "\n", $lines );
	}
}