module npr_sundaypuzzle_20120422

open common
open System.IO
open System.Text.RegularExpressions

let puzzle =

    let loadNames fn =
        File.ReadAllLines(fn) 
        |> Seq.map (fun l -> Regex.Replace(l, "(\w+).*", "$1").ToLower() )
        |> Seq.filter (fun n -> n.Length = 4)
       
    let maleNames = 
        loadNames @"dist.male.first.txt"

    let femaleNames = 
        loadNames @"dist.female.first.txt"

    let rotateChar (c:char) =
        c |> int |> (fun n -> (n + 13 - 97) % 26 + 97) |> char

    let rotateName name =
        name
        |> mapChars rotateChar
        |> Array.map string
        |> Array.fold (fun acc i -> acc + i) ""

    maleNames
    |> Seq.map (fun n -> (n, rotateName n))
    |> Seq.filter (fun (_,mn) -> Seq.exists ((=) mn) femaleNames)
    |> Seq.toArray