<?php

namespace App\Services;

use DateTime;
use DateTimeZone;

final class TimezoneList
{
    /**
     * HTML entities.
     */
    private const MINUS = '&#8722;';
    private const PLUS = '&#43;';
    private const WHITESPACE = '&#160;';

    /**
     * General timezones.
     *
     * @var array<string>
     */
    protected array $generalTimezones = [
        'GMT',
        'UTC',
    ];

    /**
     * All continents of the world.
     *
     * @var array<string, string>
     */
    protected array $continents = [
        'Africa' => DateTimeZone::AFRICA,
        'America' => DateTimeZone::AMERICA,
        'Antarctica' => DateTimeZone::ANTARCTICA,
        'Arctic' => DateTimeZone::ARCTIC,
        'Asia' => DateTimeZone::ASIA,
        'Atlantic' => DateTimeZone::ATLANTIC,
        'Australia' => DateTimeZone::AUSTRALIA,
        'Europe' => DateTimeZone::EUROPE,
        'Indian' => DateTimeZone::INDIAN,
        'Pacific' => DateTimeZone::PACIFIC,
    ];

    /**
     * The filter of the groups to get.
     */
    protected array $groupsFilter = [];

    /**
     * Status of grouping the return list.
     */
    protected bool $splitGroup = true;

    /**
     * Status of showing timezone offset.
     */
    protected bool $showOffset = true;

    /**
     * The offset prefix in list.
     */
    protected string $offsetPrefix = 'GMT/UTC';

    /**
     * Set the filter of the groups want to get.
     *
     * @return $this
     */
    public function onlyGroups(array $groups = []): static
    {
        $this->groupsFilter = $groups;

        return $this;
    }

    /**
     * Set the filter of the groups do not want to get.
     *
     * @return $this
     */
    public function excludeGroups(array $groups = []): static
    {
        if (empty($groups)) {
            $this->groupsFilter = [];

            return $this;
        }

        $this->groupsFilter = array_values(array_diff(array_keys($this->continents), $groups));

        if (! in_array('General', $groups)) {
            $this->groupsFilter[] = 'General';
        }

        return $this;
    }

    /**
     * Decide whether to split group or not.
     *
     * @return $this
     */
    public function splitGroup(bool $status = true): static
    {
        $this->splitGroup = (bool) $status;

        return $this;
    }

    /**
     * Decide whether to show the offset or not.
     *
     * @return $this
     */
    public function showOffset(bool $status = true): static
    {
        $this->showOffset = (bool) $status;

        return $this;
    }

    /**
     * Return new static to reset all config.
     *
     * @return $this
     */
    public function reset(): static
    {
        return new self;
    }

    /**
     * Create an array of timezones.
     */
    public function toArray(bool $htmlEncode = true): mixed
    {
        $list = [];

        // If do not split group
        if (! $this->splitGroup) {
            if ($this->includeGeneral()) {
                foreach ($this->generalTimezones as $timezone) {
                    $list[$timezone] = $this->formatTimezone($timezone, null, $htmlEncode);
                }
            }

            foreach ($this->loadContinents() as $continent => $mask) {
                $timezones = DateTimeZone::listIdentifiers($mask);

                foreach ($timezones as $timezone) {
                    $list[$timezone] = $this->formatTimezone($timezone, null, $htmlEncode);
                }
            }

            return $list;
        }

        // If split group
        if ($this->includeGeneral()) {
            foreach ($this->generalTimezones as $timezone) {
                $list['General'][$timezone] = $this->formatTimezone($timezone, null, $htmlEncode);
            }
        }

        foreach ($this->loadContinents() as $continent => $mask) {
            $timezones = DateTimeZone::listIdentifiers($mask);

            foreach ($timezones as $timezone) {
                $list[$continent][$timezone] = $this->formatTimezone($timezone, $continent, $htmlEncode);
            }
        }

        return $list;
    }

    /**
     * Alias of the `toSelectBox()` method.
     *
     * @param  string  $name  The name of the select tag
     * @param  string|null  $selected  The selected value
     * @param  array|string|null  $attrs  The HTML attributes of select tag
     * @param  bool  $htmlEncode  Use HTML entities for values of select tag
     *
     *@deprecated 6.0.0 This method name no longer matches the semantics
     */
    public function create(string $name, ?string $selected = null, array|string|null $attrs = null, bool $htmlEncode = true): string
    {
        return $this->toSelectBox($name, $selected, $attrs, $htmlEncode);
    }

    /**
     * Create a select box of timezones.
     *
     * @param  string  $name  The name of the select tag
     * @param  string|null  $selected  The selected value
     * @param  array|string|null  $attrs  The HTML attributes of select tag
     * @param  bool  $htmlEncode  Use HTML entities for values of select tag
     * @return string
     */
    public function toSelectBox(string $name, ?string $selected = null, array|string|null $attrs = null, bool $htmlEncode = true)
    {
        // Attributes for select element
        $attrString = null;

        if (! empty($attrs)) {
            if (is_array($attrs)) {
                foreach ($attrs as $attr_name => $attr_value) {
                    $attrString .= ' ' . $attr_name . '="' . $attr_value . '"';
                }
            } else {
                $attrString = $attrs;
            }
        }

        if ($this->splitGroup) {
            return $this->makeSelectTagWithGroup($name, $selected, $attrString, $htmlEncode);
        }

        return $this->makeSelectTagWithoutGroup($name, $selected, $attrString, $htmlEncode);
    }

    /**
     * Generate select element with the optgroup tag.
     *
     * @param  string  $name  The name of the select tag
     * @param  null|string  $selected  The selected value
     * @param  null|string  $attrs  The HTML attributes of select tag
     * @param  bool  $htmlEncode  Use HTML entities for values of select tag
     * @return string
     */
    protected function makeSelectTagWithGroup(string $name, ?string $selected = null, ?string $attrs = null, bool $htmlEncode = true)
    {
        $attrs = ! empty($attrs) ? ' ' . trim((string) $attrs) : '';
        $output = '<select name="' . (string) $name . '"' . $attrs . '>';

        if ($this->includeGeneral()) {
            $output .= '<optgroup label="General">';

            foreach ($this->generalTimezones as $timezone) {
                $output .= $this->makeOptionTag($this->formatTimezone($timezone, null, $htmlEncode), $timezone, ($selected == $timezone));
            }

            $output .= '</optgroup>';
        }

        foreach ($this->loadContinents() as $continent => $mask) {
            $timezones = DateTimeZone::listIdentifiers($mask);
            $output .= '<optgroup label="' . $continent . '">';

            foreach ($timezones as $timezone) {
                $output .= $this->makeOptionTag($this->formatTimezone($timezone, $continent, $htmlEncode), $timezone, ($selected == $timezone));
            }

            $output .= '</optgroup>';
        }

        $output .= '</select>';

        return $output;
    }

    /**
     * Generate select element without the optgroup tag.
     *
     * @param  string  $name  The name of the select tag
     * @param  null|string  $selected  The selected value
     * @param  null|string  $attrs  The HTML attributes of select tag
     * @param  bool  $htmlEncode  Use HTML entities for values of select tag
     * @return string
     */
    protected function makeSelectTagWithoutGroup(string $name, ?string $selected = null, ?string $attrs = null, bool $htmlEncode = true)
    {
        $attrs = ! empty($attrs) ? ' ' . trim((string) $attrs) : '';
        $output = '<select name="' . (string) $name . '"' . $attrs . '>';

        if ($this->includeGeneral()) {
            foreach ($this->generalTimezones as $timezone) {
                $output .= $this->makeOptionTag($this->formatTimezone($timezone, null, $htmlEncode), $timezone, ($selected == $timezone));
            }
        }

        foreach ($this->loadContinents() as $continent => $mask) {
            $timezones = DateTimeZone::listIdentifiers($mask);

            foreach ($timezones as $timezone) {
                $output .= $this->makeOptionTag($this->formatTimezone($timezone, null, $htmlEncode), $timezone, ($selected == $timezone));
            }
        }

        $output .= '</select>';

        return $output;
    }

    /**
     * Generate the option HTML tag.
     */
    protected function makeOptionTag(string $display, string $value, bool $selected = false): string
    {
        $attrs = (bool) $selected ? ' selected="selected"' : '';

        return '<option value="' . $value . '"' . $attrs . '>' . $display . '</option>';
    }

    /**
     * DetermineCheck if the general timezones is loaded in the returned result.
     */
    protected function includeGeneral(): bool
    {
        return empty($this->groupsFilter) || in_array('General', $this->groupsFilter);
    }

    /**
     * Load filtered continents.
     */
    protected function loadContinents(): array
    {
        if (empty($this->groupsFilter)) {
            return $this->continents;
        }

        return array_filter($this->continents, function ($key) {
            return in_array($key, $this->groupsFilter);
        }, ARRAY_FILTER_USE_KEY);
    }

    /**
     * Format to display timezones.
     */
    protected function formatTimezone(string $timezone, ?string $cutOffContinent = null, bool $htmlEncode = true): string
    {
        $displayedTimezone = empty($cutOffContinent) ? $timezone : substr($timezone, strlen($cutOffContinent) + 1);
        $normalizedTimezone = $this->normalizeTimezone($displayedTimezone, $htmlEncode);

        if (! $this->showOffset) {
            return $normalizedTimezone;
        }

        $offset = $this->normalizeOffset($this->getOffset($timezone), $htmlEncode);
        $separator = $this->normalizeSeparator($htmlEncode);

        return '(' . $this->offsetPrefix . $offset . ')' . $separator . $normalizedTimezone;
    }

    /**
     * Normalize the offset.
     */
    protected function normalizeOffset(string $offset, bool $htmlEncode = true): string
    {
        $search = ['-', '+'];
        $replace = $htmlEncode ? [' ' . self::MINUS . ' ', ' ' . self::PLUS . ' '] : [' - ', ' + '];

        return str_replace($search, $replace, $offset);
    }

    /**
     * Normalize the timezone.
     */
    protected function normalizeTimezone(string $timezone, bool $htmlEncode = true): string
    {
        $search = ['St_', '/', '_'];
        $replace = ['St. ', ' / ', ' '];

        return str_replace($search, $replace, $timezone);
    }

    /**
     * Normalize the separator between the timezone and offset.
     */
    protected function normalizeSeparator(bool $htmlEncode = true): string
    {
        return $htmlEncode ? str_repeat(self::WHITESPACE, 5) : ' ';
    }

    /**
     * Get the timezone offset.
     */
    protected function getOffset(string $timezone): string
    {
        $time = new DateTime('', new DateTimeZone($timezone));

        return $time->format('P');
    }

    /**
     * Get the difference of timezone to Coordinated Universal Time (UTC).
     */
    protected function getUTCOffset(string $timezone): string
    {
        $dateTimeZone = new DateTimeZone($timezone);
        $utcTime = new DateTime('', new DateTimeZone('UTC'));
        $offset = $dateTimeZone->getOffset($utcTime);
        $format = gmdate('H:i', abs($offset));

        return $offset >= 0 ? "+{$format}" : "-{$format}";
    }
}