<?php

namespace App\Models;

class ChatLib {

	public function addMessage($msg) {
		$tokens = array_values(array_filter(preg_split('/\b/', $msg->text_content)));
		if (empty($tokens)) return;
		$tokens [] = '';
		foreach ($tokens as $num => $token) {
			if ($num === 0) {
				$this->addStart($token);
			} else if ($num === 1) {
				$this->addOne($tokens[0], $token);
			} else if ($num === 2) {
				$this->addOne($tokens[1], $token);
				$this->addTwo($tokens[0], $tokens[1], $token);
			} else {
				$this->addOne($tokens[$num - 1], $token);
				$this->addTwo($tokens[$num - 2], $tokens[$num - 1], $token);
				$this->addThree($tokens[$num - 3], $tokens[$num - 2], $tokens[$num - 1], $token);
			}
		}
	}

	public function compile() {
		$this->start = $this->index($this->start);
		foreach ($this->one as $key => $value) {
			$this->one[$key] = $this->index($this->one[$key]);
		}
		foreach ($this->two as $key => $value) {
			$this->two[$key] = $this->index($this->two[$key]);
		}
		foreach ($this->three as $key => $value) {
			$this->three[$key] = $this->index($this->three[$key]);
		}
	}

	public function generate($limit = 50) {
		$tokens = [];
		$start = $this->randomStart();
		$tokens[] = $start;
		$generated = $start;
		while (strlen($generated) < $limit) {
			$next = $this->randomNext($tokens);
			if (empty($next)) break;
			$tokens[] = $next;
			$generated .= $next;
		}
		return $generated;
	}

	private function index($arr) {
		$result = [];
		$sum = 0;
		asort($arr);
		foreach ($arr as $key => $weight) {
			$lower = $sum;
			$sum += $weight;
			$result[] = [$key, $lower, $sum];
		}
		return $result;
	}

	private function randomStart() {
		return $this->pick($this->start);
	}

	private function randomNext($tokens) {
		$cnt = count($tokens);
		if ($cnt >= 3) {
			$cmb = $tokens[$cnt - 3].$tokens[$cnt - 2].$tokens[$cnt - 1];
			if (isset($this->three[$cmb])) {
				return $this->pick($this->three[$cmb]);
			}
		}
		if ($cnt >= 2) {
			$cmb = $tokens[$cnt - 2].$tokens[$cnt - 1];
			if (isset($this->two[$cmb])) {
				return $this->pick($this->two[$cmb]);
			}
		}
		if ($cnt >= 1) {
			$cmb = $tokens[$cnt - 1];
			if (isset($this->one[$cmb])) {
				return $this->pick($this->one[$cmb]);
			}
		}
		return '';
	}

	private function pick($options) {
		$max = end($options)[2];
		$num = random_int(0, $max);
		$min_index = 0;
		$max_index = count($options) - 1;
		while ($min_index < $max_index) {
			$cur_index = intval(($min_index + $max_index) / 2);
			$cur_low = $options[$cur_index][1];
			$cur_high = $options[$cur_index][2];
			if ($cur_low > $num) {
				$max_index = $cur_index;
			} else if ($cur_high < $num) {
				$min_index = $cur_index + 1;
			} else {
				$min_index = $cur_index;
				break;
			}
		}
		return $options[$min_index][0];
	}

	private function addStart($token) {
		if (empty($token)) return;
		if (!isset($this->start[$token])) {
			$this->start[$token] = 1;
		} else {
			++$this->start[$token];
		}
	}

	private function addOne($one, $token) {
		if (!isset($this->one[$one])) {
			$this->one[$one] = [];
		}
		if (!isset($this->one[$one][$token])) {
			$this->one[$one][$token] = 1;
		} else {
			++$this->one[$one][$token];
		}
	}

	private function addTwo($one, $two, $token) {
		$cmb = $one.$two;
		if (!isset($this->two[$cmb])) {
			$this->two[$cmb] = [];
		}
		if (!isset($this->two[$cmb][$token])) {
			$this->two[$cmb][$token] = 1;
		} else {
			++$this->two[$cmb][$token];
		}
	}

	private function addThree($one, $two, $three, $token) {
		$cmb = $one.$two.$three;
		if (!isset($this->three[$cmb])) {
			$this->three[$cmb] = [];
		}
		if (!isset($this->three[$cmb][$token])) {
			$this->three[$cmb][$token] = 1;
		} else {
			++$this->three[$cmb][$token];
		}
	}

	private $start = [];
	private $one = [];
	private $two = [];
	private $three = [];

}