Day Four

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+# Day Four: Passport Processing
+import os, strutils
+
+let input: string = paramStr(1)
+var fieldedPassports, validPassports: int = 0
+
+for passport in split(readFile(input), "\n\n"):
+  var fields, valid: int = 0
+  for pairs in split(strip(replace(passport, "\n", " ")), " "):
+    let
+      key: string = split(pairs, ":")[0]
+      value: string = split(pairs, ":")[1]
+    case key
+    of "byr":
+      if parseInt(value) >= 1920 and parseInt(value) <= 2002:
+        inc(valid)
+      inc(fields)
+    of "iyr":
+      if parseInt(value) >= 2010 and parseInt(value) <= 2020:
+        inc(valid)
+      inc(fields)
+    of "eyr":
+      if parseInt(value) >= 2020 and parseInt(value) <= 2030:
+        inc(valid)
+      inc(fields)
+    of "hgt":
+      let
+        units: string = value[len(value)-2..len(value)-1]
+        height: string = value[0..len(value)-3]
+      if units == "cm" and parseInt(height) >= 150 and parseInt(height) <= 193:
+        inc(valid)
+      elif units == "in" and parseInt(height) >= 59 and parseInt(height) <= 76:
+        inc(valid)
+      inc(fields)
+    of "hcl":
+      block hex:
+        if value[0] == '#':
+          for char in value[1..len(value)-1]:
+            if char notin {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'}:
+              break hex
+          inc(valid)
+      inc(fields)
+    of "ecl":
+      if value in ["amb", "blu", "brn", "gry", "grn", "hzl", "oth"]:
+        inc(valid)
+      inc(fields)
+    of "pid":
+      if len(value) == 9:
+        inc(valid)
+      inc(fields)
+  if fields >= 7:
+    inc(fieldedPassports)
+  if valid >= 7:
+    inc(validPassports)
+
+echo fieldedPassports
+echo validPassports