add structure for `Oracles' (special answers depending on queries + a few implementations (#10)

incl. a calculator, a hash encoder + rot13 and b64!, and a "what time is it" with timezone selection

frontend injected in $payload["left"] in web.php

you can see this live [on my instance](https://4get.silly.computer/web?s=7%2B8(9%5E2)&scraper=brave&nsfw=yes) (there are some issues that aren't related to this PR. favicons, etc. I'll fix them later.)

Reviewed-on: https://git.lolcat.ca/lolcat/4get/pulls/10
Co-authored-by: cynic <admin@cynic.moe>
Co-committed-by: cynic <admin@cynic.moe>

1 files changed, 158 insertions, 0 deletions

diff --git a/oracles/calc.php b/oracles/calc.php
new file mode 100644
index 0000000..4888b95
--- /dev/null
+++ b/oracles/calc.php
@@ -0,0 +1,158 @@
+<?php
+include_once("oracles/base.php");
+class calculator extends oracle {
+	public $info = [
+		"name" => "calculator"
+	];
+	public function check_query($q) {
+		// straight numerics should go to that oracle
+		if (is_numeric($q)) {
+			return false;
+		}
+		// all chars should be number-y or operator-y
+		$char_whitelist = str_split("1234567890.+-/*^%() ");
+		foreach (str_split($q) as $char) {
+			if (!in_array($char, $char_whitelist)) {
+				return false;
+			}
+		}
+		return true;
+	}
+	// a custom parser and calculator because FUCK YUO, libraries are
+	//  gay.
+	public function generate_response($q)
+	{
+		$nums = str_split("1234567890.");
+		$ops = str_split("+-/*^%;");
+		$grouping = str_split("()");
+
+		$q = str_replace(" ", "", $q);
+
+		// backstop for the parser so it catches the last
+		//  numeric token
+		$q .= ";"; 
+
+		// the following comments refer to this example input:
+		//  21+9*(3+2^9)+1
+
+		// 2-length lists of the following patterns:
+		//  ["n" (umeric), <some number>]
+		//  ["o" (perator), "<some operator>"]
+		//  ["g" (roup explicit), <"(" or ")">]
+		// e.g. [["n", 21], ["o", "+"], ["n", 9], ["o", *],
+		//       ["g", "("], ["n", 3], ["o", "+"], ["n", 2],
+		//       ["o", "^"], ["n", 9], ["g", ")"], ["o", "+"],
+		//       ["n", "1"]]
+		$tokens = array();
+		$dragline = 0;
+		foreach(str_split($q) as $i=>$char) {
+			if (in_array($char, $nums)) {
+				continue;
+			}
+			elseif (in_array($char, $ops) || in_array($char, $grouping)) {
+				// hitting a non-numeric implies everything since the
+				//  last hit has been part of a number
+				$capture = substr($q, $dragline, $i - $dragline);
+				// prevent the int cast from creating imaginary
+				//  ["n", 0] tokens
+				if ($capture != "") {
+					if (substr_count($capture, ".") > 1) {
+						return "";
+					}
+					array_push($tokens, ["n", (float)$capture]);
+				}
+				// reset to one past the current (non-numeric) char
+				$dragline = $i + 1; 
+				// the `;' backstop is not a real token and this should
+				//  never be present in the token list
+				if ($char != ";") {
+					array_push($tokens, [
+						($char == "(" || $char == ")") ? "g" : "o",
+						$char
+					]);
+				}
+			}
+			else {
+				return "";
+			}
+		}
+
+		// two operators back to back should fail
+		for ($i = 1; $i < count($tokens); $i++) {
+			if ($tokens[$i][0] == "o" && $tokens[$i-1][0] == "o") {
+				return "";
+			}
+		}
+
+		//strategy:
+		// traverse to group open (if there is one)
+		//  - return to start with the internals
+		// traverse to ^, attack token previous and after
+		// same but for *, then / then + then -
+		// poppers all teh way down
+		try {
+			return [
+				substr($q, 0, strlen($q)-1)." = " => $this->executeBlock($tokens)[0][1]
+			];
+		}   
+		catch (\Throwable $e) {
+			if (get_class($e) == "DivisionByZeroError") {
+				return [
+					$q." = " => "Division by Zero Error!!"
+				];
+			}
+			return "";
+		}
+	}
+	public function executeBlock($tokens) {
+		if (count($tokens) >= 2 && $tokens[0][0] == "o" && $tokens[0][1] == "-" && $tokens[1][0] == "n") {
+			array_splice($tokens, 0, 2, [["n", -1 * (float)$tokens[1][1]]]);
+		}
+		if (count($tokens) > 0 && $tokens[0][0] == "o" || $tokens[count($tokens)-1][0] == "o") {
+			throw new Exception("Error Processing Request", 1);
+		}
+		if (in_array(["g", "("], $tokens)) {
+			$first_open = array_search(["g", "("], $tokens);
+			$enclosedality = 1;
+			for ($i = $first_open+1; $i < count($tokens); $i++) {
+				if ($tokens[$i][0] == "g") {
+					$enclosedality += ($tokens[$i][1] == "(") ? 1 : -1;
+				}
+				if ($enclosedality == 0) {
+					array_splice($tokens, 
+						$first_open, 
+						$i+1 - $first_open, 
+						$this->executeBlock(
+							array_slice($tokens, $first_open+1, $i-1 - $first_open)
+						)
+					);
+					break;
+				}
+			}
+		}
+		$operators_in_pemdas_order = [
+			"^" => (fn($x, $y) => $x ** $y),
+			"*" => (fn($x, $y) => $x * $y),
+			"/" => (fn($x, $y) => $x / $y), 
+			"%" => (fn($x, $y) => $x % $y),
+			"+" => (fn($x, $y) => $x + $y), 
+			"-" => (fn($x, $y) => $x - $y)
+		];
+		foreach ($operators_in_pemdas_order as $op=>$func) {
+			while (in_array(["o", $op], $tokens)) {
+				for ($i = 0; $i < count($tokens); $i++) {
+					if ($tokens[$i] == ["o", $op]) {
+						array_splice(
+							$tokens,
+							$i-1,
+							3,
+							[["n", (string)($func((float)$tokens[$i-1][1], (float)$tokens[$i+1][1]))]]
+						);
+					}
+				}
+			}
+		}
+		return $tokens;
+	}
+}
+?>
\ No newline at end of file