From 40d211e8d81fe788af6af25aec0e7fdf68f2d498 Mon Sep 17 00:00:00 2001
From: Joshua Seigler <joshua@seigler.net>
Date: Thu, 16 Dec 2021 10:18:34 -0500
Subject: [PATCH] day 16 aborting

---
 src/day16/README.md |  9 +++++
 src/day16/index.js  | 87 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 src/day16/README.md
 create mode 100644 src/day16/index.js

diff --git a/src/day16/README.md b/src/day16/README.md
new file mode 100644
index 0000000..ef10068
--- /dev/null
+++ b/src/day16/README.md
@@ -0,0 +1,9 @@
+# 🎄 Advent of Code 2021 - day 16 🎄
+
+## Info
+
+Task description: [link](https://adventofcode.com/2021/day/16)
+
+## Notes
+
+...
\ No newline at end of file
diff --git a/src/day16/index.js b/src/day16/index.js
new file mode 100644
index 0000000..fbf670b
--- /dev/null
+++ b/src/day16/index.js
@@ -0,0 +1,87 @@
+import run from "aocrunner"
+
+const parseInput = (rawInput) =>
+  rawInput
+    .trim()
+    .split("")
+    .map((c) => ("0000" + parseInt(c, 16).toString(2)).substr(-4))
+    .join("")
+
+function b2d(binaryString) {
+  return parseInt(binaryString, 2)
+}
+
+const part1 = (rawInput) => {
+  const input = parseInput(rawInput)
+  let cursor = 0,
+    ans = 0
+  function read(n) {
+    cursor += n
+    return input.substr(cursor - n, n)
+  }
+  const stack = [{ count: 1 }]
+  while (stack.length) {
+    const thisLimit = stack[0]
+    if (thisLimit.count !== undefined) {
+      --thisLimit.count
+      if (thisLimit.count == 0) {
+        stack.shift()
+      }
+    }
+    if (thisLimit.cursor !== undefined) {
+      if (cursor >= thisLimit.cursor) {
+        stack.shift()
+      }
+    }
+    const version = b2d(read(3))
+    const typeId = b2d(read(3))
+    if (typeId === 4) {
+      // literal value
+      ans += version
+      let acc = ""
+      for (let more = 1; more; ) {
+        more = +read(1)
+        acc += read(4)
+      }
+    } else {
+      // operator type
+      const lengthTypeId = +read(1)
+      if (lengthTypeId == 0) {
+        const subpacketLength = b2d(read(15))
+        ans += version
+        stack.unshift({ cursor: cursor + subpacketLength })
+      } else {
+        const subpacketCount = b2d(read(11))
+        ans += version
+        stack.unshift({ count: subpacketCount })
+      }
+    }
+  }
+  return ans
+}
+
+const part2 = (rawInput) => {
+  const input = parseInput(rawInput)
+
+  return
+}
+
+run({
+  part1: {
+    tests: [
+      { input: `D2FE28`, expected: 6 },
+      // { input: `8A004A801A8002F478`, expected: 16 },
+      // { input: `620080001611562C8802118E34`, expected: 12 },
+      // { input: `C0015000016115A2E0802F182340`, expected: 23 },
+      // { input: `A0016C880162017C3686B18A3D4780`, expected: 31 },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      // { input: ``, expected: "" },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+})