From 9017e242041b51939c88e7e99221923965e919e1 Mon Sep 17 00:00:00 2001
From: Brett Parker <iDunno@sommitrealweird.co.uk>
Date: Thu, 16 Dec 2021 16:07:04 +0000
Subject: [PATCH] Day 16 pt 1 - doesn't actually stack packets hierarchically -
 just parses the headers

---
 day16/decoder.sh | 106 +++++++++++++++++++++++++++++++++++++++++++++++
 day16/input.txt  |   1 +
 day16/p1_12.txt  |   1 +
 day16/p1_16.txt  |   1 +
 day16/p1_23.txt  |   1 +
 day16/p1_31.txt  |   1 +
 6 files changed, 111 insertions(+)
 create mode 100755 day16/decoder.sh
 create mode 100644 day16/input.txt
 create mode 100644 day16/p1_12.txt
 create mode 100644 day16/p1_16.txt
 create mode 100644 day16/p1_23.txt
 create mode 100644 day16/p1_31.txt

diff --git a/day16/decoder.sh b/day16/decoder.sh
new file mode 100755
index 0000000..fe67cbd
--- /dev/null
+++ b/day16/decoder.sh
@@ -0,0 +1,106 @@
+#!/bin/bash
+
+set -u
+
+filename=${1:-p1_16.txt}
+debug=${2:-0}
+
+exec 3<"${filename}"
+
+declare -A hex_to_binary=( [0]="0000" [1]="0001" [2]="0010" [3]="0011" [4]="0100" [5]="0101" [6]="0110" [7]="0111" [8]="1000" [9]="1001" [A]="1010" [B]="1011" [C]="1100" [D]="1101" [E]="1110" [F]="1111" )
+
+read -u 3 hex_string
+
+declare -g __packets=""
+for (( a=0; a<${#hex_string}; a++ )); do
+    __packets+=${hex_to_binary[${hex_string:$a:1}]}
+done
+
+declare -g __versions_total=0
+
+declare __packet_offset=0
+
+if [ $debug == "0"  ]; then
+    echo_verbose() { true; }
+else
+    echo_verbose() { echo "$@" >&2; }
+fi
+
+parse_version() {
+    declare -g __packet_version=$((2#${__packets:$__packet_offset:3}))
+    ((__packet_offset+=3))
+    echo_verbose "Packet version: $__packet_version"
+}
+
+parse_type() {
+    declare -g __packet_type=$((2#${__packets:$__packet_offset:3}))
+    ((__packet_offset+=3))
+    echo_verbose "Packet type: $__packet_type"
+}
+
+parse_literal() {
+    local keep_going=${__packets:$__packet_offset:1}
+    local binary_value=""
+    ((__packet_offset+=1))
+    while [ $keep_going -eq 1 ]; do
+        binary_value+=${__packets:$__packet_offset:4}
+        ((__packet_offset+=4))
+        keep_going=${__packets:$__packet_offset:1}
+        ((__packet_offset+=1))
+    done
+    # if we're here, we're on to the last group
+    binary_value+=${__packets:$__packet_offset:4}
+    ((__packet_offset+=4))
+    declare -g __packet_literal=$((2#$binary_value))
+    echo_verbose "Packet literal: $__packet_literal"
+}
+
+parse_operator() {
+    local len_type=$((2#${__packets:$__packet_offset:1}))
+    ((__packet_offset+=1))
+
+    case $len_type in
+        0)
+            __packets_length=$((2#${__packets:$__packet_offset:15}))
+            ((__packet_offset+=15))
+            ;;
+        1)
+            __packets_count=$((2#${__packets:$__packet_offset:11}))
+            ((__packet_offset+=11))
+            ;;
+    esac
+}
+
+parse_packets() {
+    # we'll first need the version and the type, so grab those
+    local pversion
+    local ptype
+
+    while [ $__packet_offset -lt ${#__packets} ]; do
+        parse_version
+        parse_type
+        version=$__packet_version
+        ptype=$__packet_type
+
+        ((__versions_total+=$version))
+
+        echo_verbose "Remaining: ${__packets:$__packet_offset}"
+
+        case $ptype in
+            4)
+                parse_literal
+                ;;
+            *)
+                parse_operator
+                ;;
+        esac
+
+        if [ $(($__packet_offset+7)) -ge ${#__packets} ]; then
+            break
+        fi
+    done
+}
+
+parse_packets
+
+echo "Total: $__versions_total"
diff --git a/day16/input.txt b/day16/input.txt
new file mode 100644
index 0000000..159f371
--- /dev/null
+++ b/day16/input.txt
@@ -0,0 +1 @@
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
diff --git a/day16/p1_12.txt b/day16/p1_12.txt
new file mode 100644
index 0000000..ed3b78a
--- /dev/null
+++ b/day16/p1_12.txt
@@ -0,0 +1 @@
+620080001611562C8802118E34
diff --git a/day16/p1_16.txt b/day16/p1_16.txt
new file mode 100644
index 0000000..0d2cbff
--- /dev/null
+++ b/day16/p1_16.txt
@@ -0,0 +1 @@
+8A004A801A8002F478
diff --git a/day16/p1_23.txt b/day16/p1_23.txt
new file mode 100644
index 0000000..827e51b
--- /dev/null
+++ b/day16/p1_23.txt
@@ -0,0 +1 @@
+C0015000016115A2E0802F182340
diff --git a/day16/p1_31.txt b/day16/p1_31.txt
new file mode 100644
index 0000000..0a1278e
--- /dev/null
+++ b/day16/p1_31.txt
@@ -0,0 +1 @@
+A0016C880162017C3686B18A3D4780
-- 
2.39.5