<?php

namespace App\Models;

class ChatLib {

	public function addMessage($msg) {
		$tokens = array_values(array_filter(preg_split('/\s+/u', $msg->text_content)));
		if (empty($tokens)) return;
		$tokens [] = '';
		foreach ($tokens as $num => $token) {
			if ($num === 0) {
				$this->addStart($token);
			}
			if ($num > 0) {
				$this->addOne($tokens[$num - 1], $token);
			}
			if ($num > 1) {
				$this->addTwo($tokens[$num - 2], $tokens[$num - 1], $token);
			}
			if ($num > 2) {
				$this->addThree($tokens[$num - 3], $tokens[$num - 2], $tokens[$num - 1], $token);
			}
			if ($num > 3) {
				$this->addFour($tokens[$num - 4], $tokens[$num - 3], $tokens[$num - 2], $tokens[$num - 1], $token);
			}
			if ($num > 4) {
				$this->addFive($tokens[$num - 5], $tokens[$num - 4], $tokens[$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[$key]);
			if (empty($this->one[$key])) {
				unset($this->one[$key]);
			}
		}
		foreach ($this->two as $key => $value) {
			$this->two[$key] = $this->index($this->two[$key]);
			if (empty($this->two[$key])) {
				unset($this->two[$key]);
			}
		}
		foreach ($this->three as $key => $value) {
			$this->three[$key] = $this->index($this->three[$key]);
			if (empty($this->three[$key])) {
				unset($this->three[$key]);
			}
		}
		foreach ($this->four as $key => $value) {
			$this->four[$key] = $this->index($this->four[$key]);
			if (empty($this->four[$key])) {
				unset($this->four[$key]);
			}
		}
		foreach ($this->five as $key => $value) {
			$this->five[$key] = $this->index($this->five[$key]);
			if (empty($this->five[$key])) {
				unset($this->five[$key]);
			}
		}
	}

	public function generate($limit = 75) {
		$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 = [];
		$sum = 0;
		foreach ($arr as $key => $entry) {
			$weight = $entry['count'];
			if ($weight == 1) continue;
			$lower = $sum;
			$sum += intval(pow($weight, 1.4));
			$examples = [];
			if (is_array(end($entry['examples']))) {
				// already processed
				$examples = $entry['examples'];
			} else {
				$subsum = 0;
				foreach ($entry['examples'] as $example => $subweight) {
					$sublower = $subsum;
					$subsum += $subweight * $subweight;
					$examples[] = [$example, $sublower, $subsum];
				}
			}
			$result[] = [$key, $lower, $sum, $examples];
		}
		return $result;
	}

	private function randomStart() {
		$pick = $this->pick($this->start);
		if (is_null($pick)) return '';
		return $this->exampleOf($pick);
	}

	private function randomNext($tokens) {
		$cnt = count($tokens);
		$picks = [];
		if ($cnt >= 5) {
			$cmb = $this->generalize(array_slice($tokens, $cnt - 5, 5));
			if (isset($this->five[$cmb])) {
				$pick = $this->pick($this->five[$cmb]);
				if (!is_null($pick)) {
					$picks[$pick[0]] = [
						'count' => 10,
						'examples' => $pick[3],
					];
				}
			}
		}
		if ($cnt >= 4) {
			$cmb = $this->generalize(array_slice($tokens, $cnt - 4, 4));
			if (isset($this->four[$cmb])) {
				$pick = $this->pick($this->four[$cmb]);
				if (!is_null($pick)) {
					$picks[$pick[0]] = [
						'count' => 12,
						'examples' => $pick[3],
					];
				}
			}
		}
		if ($cnt >= 3) {
			$cmb = $this->generalize(array_slice($tokens, $cnt - 3, 3));
			if (isset($this->three[$cmb])) {
				$pick = $this->pick($this->three[$cmb]);
				if (!is_null($pick)) {
					$picks[$pick[0]] = [
						'count' => 14,
						'examples' => $pick[3],
					];
				}
			}
		}
		if ($cnt >= 2) {
			$cmb = $this->generalize(array_slice($tokens, $cnt - 2, 2));
			if (isset($this->two[$cmb])) {
				$pick = $this->pick($this->two[$cmb]);
				if (!is_null($pick)) {
					$picks[$pick[0]] = [
						'count' => 4,
						'examples' => $pick[3],
					];
				}
			}
		}
		if ($cnt >= 1) {
			$cmb = $this->generalize(array_slice($tokens, $cnt - 1, 1));
			if (isset($this->one[$cmb])) {
				$pick = $this->pick($this->one[$cmb]);
				if (!is_null($pick)) {
					$picks[$pick[0]] = [
						'count' => 2,
						'examples' => $pick[3],
					];
				}
			}
		}
		if (empty($picks)) return '';
		$picks = $this->index($picks);
		$pick = $this->pick($picks);
		return $this->exampleOf($pick);
	}

	private function pick($options) {
		if (empty($options)) return null;
		$max = end($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];
	}

	private function addStart($token) {
		if (empty($token)) return;
		$this->increment($this->start, $token);
	}

	private function addOne($one, $token) {
		$cmb = $this->generalize([$one]);
		if (!isset($this->one[$cmb])) {
			$this->one[$cmb] = [];
		}
		$this->increment($this->one[$cmb], $token);
	}

	private function addTwo($one, $two, $token) {
		$cmb = $this->generalize([$one, $two]);
		if (!isset($this->two[$cmb])) {
			$this->two[$cmb] = [];
		}
		$this->increment($this->two[$cmb], $token);
	}

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

	private function addFour($one, $two, $three, $four, $token) {
		$cmb = $this->generalize([$one, $two, $three, $four]);
		if (!isset($this->four[$cmb])) {
			$this->four[$cmb] = [];
		}
		$this->increment($this->four[$cmb], $token);
	}

	private function addFive($one, $two, $three, $four, $five, $token) {
		$cmb = $this->generalize([$one, $two, $three, $four, $five]);
		if (!isset($this->five[$cmb])) {
			$this->five[$cmb] = [];
		}
		$this->increment($this->five[$cmb], $token);
	}

	private function increment(&$which, $token) {
		$generalized = $this->generalize([$token]);
		if (!isset($which[$generalized])) {
			$which[$generalized] = [
				'count' => 1,
				'examples' => [],
			];
			$which[$generalized]['examples'][$token] = 1;
		} else {
			++$which[$generalized]['count'];
			if (!isset($which[$generalized]['examples'][$token])) {
				$which[$generalized]['examples'][$token] = 1;
			} else {
				++$which[$generalized]['examples'][$token];
			}
		}
	}

	private function generalize($tokens) {
		$str = '';
		foreach ($tokens as $token) {
			$replaced = preg_replace('/\W/u', '', $token);
			$replaced = preg_replace('/\d+/', '0', $replaced);
			$replaced = strtolower(trim($replaced));
			$str .= empty($replaced) ? $token : $replaced;
		}
		return $str;
	}

	private function exampleOf($pick) {
		$example = $this->pick($pick[3]);
		return $example[0];
	}

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

}