Add 2020 for nim stuff

2020/.gitignore

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+/build
+*.log

2020/aoc2020.nimble

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+# Package
+
+version     = "0.1.0"
+author      = "Daniel Flanagan"
+description = "@lytedev's Advent of Code 2020 code"
+license     = "MIT"
+srcDir      = "src"
+bin         = @["aoc2020"]
+binDir      = "build"
+
+# Dependencies
+
+requires "nim >= 1.4.0"
+

2020/config.nims

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+switch "define", "ssl"
+switch "path", "src/"
+

2020/makefile

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+run:
+	nimble run

2020/readme.md

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+# Advent of Code 2020
+
+This year, I've decided to tinker around with [`nim`][nim].
+
+Enjoy the mess!

2020/src/aoc2020.nim

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+import day_loader, tables
+
+proc solve_all() {.used.} =
+  for (_, solver) in solvers.pairs():
+    echo solver()
+
+proc solve_for_day(n: int) {.used.} =
+  echo solvers[n]()
+
+when isMainModule:
+  solve_for_day(2)

2020/src/day1.nim

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+import sets, streams, strutils, options
+
+# Day 1
+
+let day1TargetSum = 2020
+
+proc part1*(strm: Stream): Option[int] =
+  var targets = initHashSet[int]()
+  for line in strm.lines():
+    let n = parseInt line
+    if targets.contains(day1TargetSum - n):
+      return some((day1TargetSum - n) * n)
+    else:
+      targets.incl n
+
+proc part2*(strm: Stream): Option[int] =
+  # this works exactly the same as the previous algorithm, except we simply
+  # permute once more
+  # TODO: if I was really cool, I could split the shared functionality into
+  # a shared proc
+  var nums: seq[int]
+  for line in strm.lines():
+    nums.add parseInt line
+  for n in nums:
+    var iset = initHashSet[int]()
+    let nTargetSum = day1TargetSum - n
+    for n2 in nums:
+      if iset.contains(nTargetSum - n2):
+        return some(n * n2 * (nTargetSum - n2))
+      iset.incl n2

2020/src/day2.nim

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+import streams
+
+proc part1*(strm: Stream): string =
+  "ayy"
+
+proc part2*(strm: Stream): string =
+  "ayy"

2020/src/day_loader.nim

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+import input_requestor, os, macros, strformat, tables
+
+macro loadDays(): untyped =
+  var solver_str = "var solvers = {\n"
+  result = newStmtList()
+  for day in 1..2:
+    let module = fmt"day{day}"
+    if fileExists joinPath("src/", &"{module}.nim"):
+      result.add parseStmt fmt"from {module} import nil"
+      solver_str = solver_str & &"""
+      {day}: proc(): (string, string) = (
+        $(day{day}.part1(getInputFileStreamForDay({day}))),
+        $(day{day}.part2(getInputFileStreamForDay({day})))
+      ),
+      """
+  result.add parseStmt (solver_str & "\n}.newTable()\nexport solvers")
+
+loadDays()

2020/src/input_requestor.nim

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+import httpclient, strformat, os, logging, streams
+
+var fileLog = newFileLogger("aoc2020.log")
+var consoleLog = newConsoleLogger()
+addHandler(consoleLog)
+addHandler(fileLog)
+
+let cacheDir = joinPath(getEnv("XDG_CACHE_HOME", expandTilde("~/.cache")), "/aoc2020-cache")
+createDir(cacheDir)
+
+# TODO: add login capabilities via `pass` for auto-cookie-retrieval?
+
+proc requestAocContentAuthed(url: string): TaintedString =
+  let cookie = getEnv("ADVENT_OF_CODE_AUTH_COOKIE", readFile(expandTilde("~/.advent-of-code-auth-cookie")))
+  let client = newHttpClient()
+  client.headers = newHttpHeaders({"cookie": cookie})
+  client.getContent(url)
+
+proc getInputFileStreamForDay*(day: int): FileStream =
+  # retrieve the input and dump it to a file if we don't have it yet
+  let cacheFile = joinPath(cacheDir, fmt"/day-{day}.aoc-input")
+  if not fileExists(cacheFile):
+    let url = fmt"https://adventofcode.com/2020/day/{day}/input"
+    writeFile(cacheFile, requestAocContentAuthed(url).string)
+  openFileStream(cacheFile)
+
+proc getInputForDay*(day: int): string =
+  getInputFileStreamForDay(day).readAll()