Very rough day 2 implementation

1 files changed, 86 insertions, 0 deletions

diff --git a/aoc-2020-gleam/src/days/day02.gleam b/aoc-2020-gleam/src/days/day02.gleam
new file mode 100644
index 0000000..a56e0e1
--- /dev/null
+++ b/aoc-2020-gleam/src/days/day02.gleam
@@ -0,0 +1,86 @@
+import gleam/io
+import gleam/list
+import gleam/string
+import gleam/pair
+import gleam/bool
+import ext/resultx
+import util/input_util
+import util/parser as p
+
+type Policy {
+  Policy(min: Int, max: Int, grapheme: String)
+}
+
+type Line {
+  Line(policy: Policy, password: String)
+}
+
+fn is_line_valid1(line: Line) -> Bool {
+  line.password
+  |> string.to_graphemes
+  |> list.filter(for: fn(g) { g == line.policy.grapheme })
+  |> list.length
+  |> fn(l) { line.policy.min <= l && l <= line.policy.max }
+}
+
+fn is_line_valid2(line: Line) -> Bool {
+  let graphemes = string.to_graphemes(line.password)
+  let grapheme_matches = fn(idx) {
+    list.at(in: graphemes, get: idx - 1)
+    |> resultx.force_unwrap == line.policy.grapheme
+  }
+  bool.exclusive_or(
+    grapheme_matches(line.policy.min),
+    grapheme_matches(line.policy.max),
+  )
+}
+
+fn parse_policy() -> p.Parser(Policy) {
+  p.int()
+  |> p.then_skip(p.grapheme("-"))
+  |> p.and_then(p.int())
+  |> p.then_skip(p.grapheme(" "))
+  |> p.and_then(p.any_grapheme())
+  |> p.then_skip(p.grapheme(":"))
+  |> p.then_skip(p.grapheme(" "))
+  |> p.map(with: fn(x) {
+    let #(#(min, max), grapheme) = x
+    Policy(min, max, grapheme)
+  })
+}
+
+fn parse_line(string: String) -> Line {
+  let line_parser =
+    parse_policy()
+    |> p.and_then(p.all_remaining())
+    |> p.map(fn(t) { Line(pair.first(t), pair.second(t)) })
+
+  assert Ok(#(policy, _)) = p.run(line_parser, on: string)
+  policy
+}
+
+fn part1(lines: List(String)) -> Int {
+  lines
+  |> list.map(with: parse_line)
+  |> list.filter(for: is_line_valid1)
+  |> list.length
+}
+
+fn part2(lines: List(String)) -> Int {
+  lines
+  |> list.map(with: parse_line)
+  |> list.filter(for: is_line_valid2)
+  |> list.length
+}
+
+pub fn run() -> Nil {
+  let test = input_util.read_lines("test02")
+  assert 2 = part1(test)
+  assert 1 = part2(test)
+
+  let input = input_util.read_lines("day02")
+  io.debug(part1(input))
+  io.debug(part2(input))
+
+  Nil
+}