1 files changed, 124 insertions, 1 deletions
diff --git a/aoc2023/src/day20/solve.gleam b/aoc2023/src/day20/solve.gleam
index e589379..449cdeb 100644
--- a/aoc2023/src/day20/solve.gleam
+++ b/aoc2023/src/day20/solve.gleam
@@ -1,8 +1,131 @@
 import adglent.{First, Second}
 import gleam/io
+import gleam/dict.{type Dict}
+import gleam/queue.{type Queue}
+import gleam/string
+import gleam/list
+import gleam/bool
+
+type Node {
+  Broadcaster(children: List(String))
+  Flipflop(children: List(String), state: Power)
+  Conjunction(children: List(String), state: Dict(String, TonePitch))
+  Ground(children: List(String))
+}
+
+type Tone {
+  Tone(from: String, to: String, pitch: TonePitch)
+}
+
+type Power {
+  On
+  Off
+}
+
+type TonePitch {
+  Low
+  High
+}
+
+fn flip_power(p: Power) -> Power {
+  case p {
+    On -> Off
+    Off -> On
+  }
+}
+
+fn flip_flop_pitch(p: Power) -> TonePitch {
+  case p {
+    Off -> High
+    On -> Low
+  }
+}
+
+fn parse_node(input: String) -> #(String, Node) {
+  let assert [full_name, children_str] = string.split(input, on: " -> ")
+  let children = string.split(children_str, on: ", ")
+
+  case full_name {
+    "%" <> name -> #(name, Flipflop(children: children, state: Off))
+    "&" <> name -> #(name, Conjunction(children: children, state: dict.new()))
+    "broadcaster" -> #("broadcaster", Broadcaster(children: children))
+    name -> #(name, Ground([]))
+  }
+}
+
+fn to_initial_state(nodes: List(#(String, Node))) -> Dict(String, Node) {
+  let node_dict = dict.from_list(nodes)
+  let node_names = dict.keys(node_dict)
+
+  use name, node <- dict.map_values(node_dict)
+  case node {
+    Conjunction(state: _, children: chs) ->
+      node_names
+      |> list.filter(fn(n) {
+        let assert Ok(node) = dict.get(node_dict, n)
+        list.contains(node.children, any: name)
+      })
+      |> list.map(fn(n) { #(n, Low) })
+      |> dict.from_list()
+      |> fn(dict) { Conjunction(state: dict, children: chs) }
+    other -> other
+  }
+}
+
+fn press_button_once(
+  initial: #(Dict(String, Node), Int, Int),
+  queue: Queue(Tone),
+) {
+  let #(nodes, high, low) = initial
+  use <- bool.guard(queue.is_empty(queue), initial)
+  let assert Ok(#(Tone(from_name, to_name, pitch) as tone, rest)) =
+    queue.pop_front(queue)
+  io.debug(tone)
+  let assert Ok(to_node) = dict.get(nodes, to_name)
+  case to_node {
+    Broadcaster(children) ->
+      list.fold(children, rest, fn(acc, c) {
+        queue.push_back(acc, Tone(from: to_name, to: c, pitch: pitch))
+      })
+      |> press_button_once(initial, _)
+      
+    Conjunction(state: state, children: children) -> todo
+
+    Flipflop(..) if pitch == High -> press_button_once(initial, rest)
+    Flipflop(state: state, children: children) -> {
+      let updated_nodes =
+        dict.insert(
+          nodes,
+          to_name,
+          Flipflop(state: flip_power(state), children: children),
+        )
+      let updated_queue =
+        list.fold(children, rest, fn(acc, c) {
+          queue.push_back(
+            acc,
+            Tone(from: to_name, to: c, pitch: flip_flop_pitch(state)),
+          )
+        })
+      press_button_once(#(updated_nodes, 0, 0), updated_queue)
+    }
+    Ground(..) -> press_button_once(initial, rest)
+  }
+}
 
 pub fn part1(input: String) {
-  todo as "Implement solution to part 1"
+  let initial_state =
+    input
+    |> string.split(on: "\n")
+    |> list.map(parse_node)
+    |> to_initial_state()
+
+  press_button_once(
+    #(initial_state, 0, 1),
+    [Tone("button", "broadcaster", Low)]
+    |> queue.from_list,
+  )
+
+  "1"
 }
 
 pub fn part2(input: String) {