{-# LANGUAGE OverloadedStrings #-}
-- | Mnemonic keys (BIP-39). Only the English dictionary in the BIP is
-- supported.
module Network.Haskoin.Crypto.Mnemonic
  -- * Data types
, Mnemonic
, Passphrase
, Seed

  -- * Entropy encoding and decoding
, toMnemonic
, fromMnemonic

  -- * Generating 512-bit seeds
, mnemonicToSeed

  -- * Helper functions
, getBits
) where

import Control.Monad (when)
import qualified Crypto.Hash.SHA256 as SHA256
import Crypto.PBKDF.ByteString (sha512PBKDF2)
import Data.Bits ((.&.), shiftL, shiftR)
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as B8
import Data.Char (isAscii)
import Data.List
import Data.Maybe
import Network.Haskoin.Util (bsToInteger, integerToBS)

type Entropy = ByteString
type Mnemonic = String
type Passphrase = String
type Seed = ByteString
type Checksum = ByteString

-- | Provide intial entropy as a 'ByteString' of length multiple of 4 bytes.
-- Output a mnemonic sentence.
toMnemonic :: Entropy -> Either String Mnemonic
toMnemonic ent = do
    when (remainder /= 0) $ 
        Left "toMnemonic: entropy must be multiples of 4 bytes"
    when (cs_len > 16) $ 
        Left "toMnemonic: maximum entropy is 64 bytes (512 bits)"
    when (isJust $ find (not . isAscii) ms) $
        Left "fromMnemonic: non-ASCII characters not supported"
    return ms
    (cs_len, remainder) = BS.length ent `quotRem` 4
    cs = calcCS cs_len ent
    indices = bsToIndices $ ent `BS.append` cs
    ms = unwords $ map (wl !!) indices

-- | Revert 'toMnemonic'. Do not use this to generate seeds. Instead use
-- 'mnemonicToSeed'. This outputs the original entropy used to generate a
-- mnemonic.
fromMnemonic :: Mnemonic -> Either String Entropy
fromMnemonic ms = do
    when (isJust $ find (not . isAscii) ms) $
        Left "fromMnemonic: non-ASCII characters not supported"
    when (word_count > 48) $ 
        Left $ "fromMnemonic: too many words: " ++ show word_count
    when (word_count `mod` 3 /= 0) $ 
        Left $ "fromMnemonic: wrong number of words: " ++ show word_count
    ms_bs <- indicesToBS =<< getIndices ms_words
    let (ms_ent, ms_cs) = BS.splitAt (ent_len * 4) ms_bs
        ms_cs_num = numCS cs_len ms_cs
        ent_cs_num = numCS cs_len $ calcCS cs_len ms_ent
    when (ent_cs_num /= ms_cs_num) $ 
        Left $ "fromMnemonic: checksum failed: " ++ sh ent_cs_num ms_cs_num
    return ms_ent
    ms_words = words ms
    word_count = length ms_words
    (ent_len, cs_len) = (word_count * 11) `quotRem` 32
    sh cs_a cs_b = show cs_a ++ " /= " ++ show cs_b

calcCS :: Int -> Entropy -> Checksum
calcCS len = getBits len . SHA256.hash

numCS :: Int -> Entropy -> Integer
numCS len = shiftCS . bsToInteger
    shiftCS = case 8 - len `mod` 8 of
        0 -> id
        x -> flip shiftR x

-- | Turn any sequence of characters into a 512-bit seed.  Does not have to be
-- a mnemonic sentence generated from 'toMnemonic'.  Use 'mnemonicToSeed' to
-- get a seed from a mnemonic sentence.  Warning: Does not perform NFKD
-- normalization.
anyToSeed :: Passphrase -> Mnemonic -> Seed
anyToSeed pf ms = sha512PBKDF2 (B8.pack ms) (B8.pack $ "mnemonic" ++ pf) 2048 64

-- | Get a 512-bit seed from a mnemonic sentence.  Will calculate checksum.
-- Passphrase can be used to protect the mnemonic.  Use an empty string as
-- passphrase if none is required.
mnemonicToSeed :: Passphrase -> Mnemonic -> Either String Seed
mnemonicToSeed pf ms = do
    ent <- fromMnemonic ms
    mnm <- toMnemonic ent
    return $ anyToSeed pf mnm

-- | Obtain 'Int' bits from beginning of 'ByteString'. Resulting 'ByteString'
-- will be smallest required to hold that many bits, padded with zeroes to the
-- right.
getBits :: Int -> ByteString -> ByteString
getBits b bs
    | r == 0 = BS.take q bs
    | otherwise = i `BS.snoc` l
    (q, r) = b `quotRem` 8
    s = (BS.take (q + 1) bs)
    i = BS.init s
    l = BS.last s .&. (0xff `shiftL` (8 - r))    -- zero unneeded bits

-- | Get indices of words in word list.
getIndices :: [String] -> Either String [Int]
getIndices ws
    | null n = return $ catMaybes i
    | otherwise = Left $ "getIndices: words not found: " ++ w
    i = map (flip elemIndex wl) ws
    n = elemIndices Nothing i
    w = unwords $ map (ws !!) n

indicesToBS :: [Int] -> Either String ByteString
indicesToBS is = do
    when lrg $ Left "indicesToBS: index larger or equal than 2048"
    return . pad . integerToBS $ (foldl' f 0 is) `shiftL` shift_width
    lrg = not . isNothing $ find (>= 2048) is
    (q, r) = (length is * 11) `quotRem` 8
    shift_width = if r == 0 then 0 else 8 - r
    bl = if r == 0 then q else q + 1   -- length of resulting ByteString
    pad bs = BS.append (BS.replicate (bl - BS.length bs) 0x00) bs
    f acc x = (acc `shiftL` 11) + fromIntegral x

bsToIndices :: ByteString -> [Int]
bsToIndices bs = reverse . go q $ bsToInteger bs `shiftR` r
    (q, r) = (BS.length bs * 8) `quotRem` 11
    go 0 _ = []
    go n i = (fromIntegral $ i `mod` 2048) : go (n - 1) (i `shiftR` 11)

-- | Standard English dictionary from BIP-39 specification.
wl :: [String]
wl =
    [ "abandon", "ability", "able", "about", "above", "absent"
    , "absorb", "abstract", "absurd", "abuse", "access", "accident"
    , "account", "accuse", "achieve", "acid", "acoustic", "acquire"
    , "across", "act", "action", "actor", "actress", "actual"
    , "adapt", "add", "addict", "address", "adjust", "admit"
    , "adult", "advance", "advice", "aerobic", "affair", "afford"
    , "afraid", "again", "age", "agent", "agree", "ahead"
    , "aim", "air", "airport", "aisle", "alarm", "album"
    , "alcohol", "alert", "alien", "all", "alley", "allow"
    , "almost", "alone", "alpha", "already", "also", "alter"
    , "always", "amateur", "amazing", "among", "amount", "amused"
    , "analyst", "anchor", "ancient", "anger", "angle", "angry"
    , "animal", "ankle", "announce", "annual", "another", "answer"
    , "antenna", "antique", "anxiety", "any", "apart", "apology"
    , "appear", "apple", "approve", "april", "arch", "arctic"
    , "area", "arena", "argue", "arm", "armed", "armor"
    , "army", "around", "arrange", "arrest", "arrive", "arrow"
    , "art", "artefact", "artist", "artwork", "ask", "aspect"
    , "assault", "asset", "assist", "assume", "asthma", "athlete"
    , "atom", "attack", "attend", "attitude", "attract", "auction"
    , "audit", "august", "aunt", "author", "auto", "autumn"
    , "average", "avocado", "avoid", "awake", "aware", "away"
    , "awesome", "awful", "awkward", "axis", "baby", "bachelor"
    , "bacon", "badge", "bag", "balance", "balcony", "ball"
    , "bamboo", "banana", "banner", "bar", "barely", "bargain"
    , "barrel", "base", "basic", "basket", "battle", "beach"
    , "bean", "beauty", "because", "become", "beef", "before"
    , "begin", "behave", "behind", "believe", "below", "belt"
    , "bench", "benefit", "best", "betray", "better", "between"
    , "beyond", "bicycle", "bid", "bike", "bind", "biology"
    , "bird", "birth", "bitter", "black", "blade", "blame"
    , "blanket", "blast", "bleak", "bless", "blind", "blood"
    , "blossom", "blouse", "blue", "blur", "blush", "board"
    , "boat", "body", "boil", "bomb", "bone", "bonus"
    , "book", "boost", "border", "boring", "borrow", "boss"
    , "bottom", "bounce", "box", "boy", "bracket", "brain"
    , "brand", "brass", "brave", "bread", "breeze", "brick"
    , "bridge", "brief", "bright", "bring", "brisk", "broccoli"
    , "broken", "bronze", "broom", "brother", "brown", "brush"
    , "bubble", "buddy", "budget", "buffalo", "build", "bulb"
    , "bulk", "bullet", "bundle", "bunker", "burden", "burger"
    , "burst", "bus", "business", "busy", "butter", "buyer"
    , "buzz", "cabbage", "cabin", "cable", "cactus", "cage"
    , "cake", "call", "calm", "camera", "camp", "can"
    , "canal", "cancel", "candy", "cannon", "canoe", "canvas"
    , "canyon", "capable", "capital", "captain", "car", "carbon"
    , "card", "cargo", "carpet", "carry", "cart", "case"
    , "cash", "casino", "castle", "casual", "cat", "catalog"
    , "catch", "category", "cattle", "caught", "cause", "caution"
    , "cave", "ceiling", "celery", "cement", "census", "century"
    , "cereal", "certain", "chair", "chalk", "champion", "change"
    , "chaos", "chapter", "charge", "chase", "chat", "cheap"
    , "check", "cheese", "chef", "cherry", "chest", "chicken"
    , "chief", "child", "chimney", "choice", "choose", "chronic"
    , "chuckle", "chunk", "churn", "cigar", "cinnamon", "circle"
    , "citizen", "city", "civil", "claim", "clap", "clarify"
    , "claw", "clay", "clean", "clerk", "clever", "click"
    , "client", "cliff", "climb", "clinic", "clip", "clock"
    , "clog", "close", "cloth", "cloud", "clown", "club"
    , "clump", "cluster", "clutch", "coach", "coast", "coconut"
    , "code", "coffee", "coil", "coin", "collect", "color"
    , "column", "combine", "come", "comfort", "comic", "common"
    , "company", "concert", "conduct", "confirm", "congress", "connect"
    , "consider", "control", "convince", "cook", "cool", "copper"
    , "copy", "coral", "core", "corn", "correct", "cost"
    , "cotton", "couch", "country", "couple", "course", "cousin"
    , "cover", "coyote", "crack", "cradle", "craft", "cram"
    , "crane", "crash", "crater", "crawl", "crazy", "cream"
    , "credit", "creek", "crew", "cricket", "crime", "crisp"
    , "critic", "crop", "cross", "crouch", "crowd", "crucial"
    , "cruel", "cruise", "crumble", "crunch", "crush", "cry"
    , "crystal", "cube", "culture", "cup", "cupboard", "curious"
    , "current", "curtain", "curve", "cushion", "custom", "cute"
    , "cycle", "dad", "damage", "damp", "dance", "danger"
    , "daring", "dash", "daughter", "dawn", "day", "deal"
    , "debate", "debris", "decade", "december", "decide", "decline"
    , "decorate", "decrease", "deer", "defense", "define", "defy"
    , "degree", "delay", "deliver", "demand", "demise", "denial"
    , "dentist", "deny", "depart", "depend", "deposit", "depth"
    , "deputy", "derive", "describe", "desert", "design", "desk"
    , "despair", "destroy", "detail", "detect", "develop", "device"
    , "devote", "diagram", "dial", "diamond", "diary", "dice"
    , "diesel", "diet", "differ", "digital", "dignity", "dilemma"
    , "dinner", "dinosaur", "direct", "dirt", "disagree", "discover"
    , "disease", "dish", "dismiss", "disorder", "display", "distance"
    , "divert", "divide", "divorce", "dizzy", "doctor", "document"
    , "dog", "doll", "dolphin", "domain", "donate", "donkey"
    , "donor", "door", "dose", "double", "dove", "draft"
    , "dragon", "drama", "drastic", "draw", "dream", "dress"
    , "drift", "drill", "drink", "drip", "drive", "drop"
    , "drum", "dry", "duck", "dumb", "dune", "during"
    , "dust", "dutch", "duty", "dwarf", "dynamic", "eager"
    , "eagle", "early", "earn", "earth", "easily", "east"
    , "easy", "echo", "ecology", "economy", "edge", "edit"
    , "educate", "effort", "egg", "eight", "either", "elbow"
    , "elder", "electric", "elegant", "element", "elephant", "elevator"
    , "elite", "else", "embark", "embody", "embrace", "emerge"
    , "emotion", "employ", "empower", "empty", "enable", "enact"
    , "end", "endless", "endorse", "enemy", "energy", "enforce"
    , "engage", "engine", "enhance", "enjoy", "enlist", "enough"
    , "enrich", "enroll", "ensure", "enter", "entire", "entry"
    , "envelope", "episode", "equal", "equip", "era", "erase"
    , "erode", "erosion", "error", "erupt", "escape", "essay"
    , "essence", "estate", "eternal", "ethics", "evidence", "evil"
    , "evoke", "evolve", "exact", "example", "excess", "exchange"
    , "excite", "exclude", "excuse", "execute", "exercise", "exhaust"
    , "exhibit", "exile", "exist", "exit", "exotic", "expand"
    , "expect", "expire", "explain", "expose", "express", "extend"
    , "extra", "eye", "eyebrow", "fabric", "face", "faculty"
    , "fade", "faint", "faith", "fall", "false", "fame"
    , "family", "famous", "fan", "fancy", "fantasy", "farm"
    , "fashion", "fat", "fatal", "father", "fatigue", "fault"
    , "favorite", "feature", "february", "federal", "fee", "feed"
    , "feel", "female", "fence", "festival", "fetch", "fever"
    , "few", "fiber", "fiction", "field", "figure", "file"
    , "film", "filter", "final", "find", "fine", "finger"
    , "finish", "fire", "firm", "first", "fiscal", "fish"
    , "fit", "fitness", "fix", "flag", "flame", "flash"
    , "flat", "flavor", "flee", "flight", "flip", "float"
    , "flock", "floor", "flower", "fluid", "flush", "fly"
    , "foam", "focus", "fog", "foil", "fold", "follow"
    , "food", "foot", "force", "forest", "forget", "fork"
    , "fortune", "forum", "forward", "fossil", "foster", "found"
    , "fox", "fragile", "frame", "frequent", "fresh", "friend"
    , "fringe", "frog", "front", "frost", "frown", "frozen"
    , "fruit", "fuel", "fun", "funny", "furnace", "fury"
    , "future", "gadget", "gain", "galaxy", "gallery", "game"
    , "gap", "garage", "garbage", "garden", "garlic", "garment"
    , "gas", "gasp", "gate", "gather", "gauge", "gaze"
    , "general", "genius", "genre", "gentle", "genuine", "gesture"
    , "ghost", "giant", "gift", "giggle", "ginger", "giraffe"
    , "girl", "give", "glad", "glance", "glare", "glass"
    , "glide", "glimpse", "globe", "gloom", "glory", "glove"
    , "glow", "glue", "goat", "goddess", "gold", "good"
    , "goose", "gorilla", "gospel", "gossip", "govern", "gown"
    , "grab", "grace", "grain", "grant", "grape", "grass"
    , "gravity", "great", "green", "grid", "grief", "grit"
    , "grocery", "group", "grow", "grunt", "guard", "guess"
    , "guide", "guilt", "guitar", "gun", "gym", "habit"
    , "hair", "half", "hammer", "hamster", "hand", "happy"
    , "harbor", "hard", "harsh", "harvest", "hat", "have"
    , "hawk", "hazard", "head", "health", "heart", "heavy"
    , "hedgehog", "height", "hello", "helmet", "help", "hen"
    , "hero", "hidden", "high", "hill", "hint", "hip"
    , "hire", "history", "hobby", "hockey", "hold", "hole"
    , "holiday", "hollow", "home", "honey", "hood", "hope"
    , "horn", "horror", "horse", "hospital", "host", "hotel"
    , "hour", "hover", "hub", "huge", "human", "humble"
    , "humor", "hundred", "hungry", "hunt", "hurdle", "hurry"
    , "hurt", "husband", "hybrid", "ice", "icon", "idea"
    , "identify", "idle", "ignore", "ill", "illegal", "illness"
    , "image", "imitate", "immense", "immune", "impact", "impose"
    , "improve", "impulse", "inch", "include", "income", "increase"
    , "index", "indicate", "indoor", "industry", "infant", "inflict"
    , "inform", "inhale", "inherit", "initial", "inject", "injury"
    , "inmate", "inner", "innocent", "input", "inquiry", "insane"
    , "insect", "inside", "inspire", "install", "intact", "interest"
    , "into", "invest", "invite", "involve", "iron", "island"
    , "isolate", "issue", "item", "ivory", "jacket", "jaguar"
    , "jar", "jazz", "jealous", "jeans", "jelly", "jewel"
    , "job", "join", "joke", "journey", "joy", "judge"
    , "juice", "jump", "jungle", "junior", "junk", "just"
    , "kangaroo", "keen", "keep", "ketchup", "key", "kick"
    , "kid", "kidney", "kind", "kingdom", "kiss", "kit"
    , "kitchen", "kite", "kitten", "kiwi", "knee", "knife"
    , "knock", "know", "lab", "label", "labor", "ladder"
    , "lady", "lake", "lamp", "language", "laptop", "large"
    , "later", "latin", "laugh", "laundry", "lava", "law"
    , "lawn", "lawsuit", "layer", "lazy", "leader", "leaf"
    , "learn", "leave", "lecture", "left", "leg", "legal"
    , "legend", "leisure", "lemon", "lend", "length", "lens"
    , "leopard", "lesson", "letter", "level", "liar", "liberty"
    , "library", "license", "life", "lift", "light", "like"
    , "limb", "limit", "link", "lion", "liquid", "list"
    , "little", "live", "lizard", "load", "loan", "lobster"
    , "local", "lock", "logic", "lonely", "long", "loop"
    , "lottery", "loud", "lounge", "love", "loyal", "lucky"
    , "luggage", "lumber", "lunar", "lunch", "luxury", "lyrics"
    , "machine", "mad", "magic", "magnet", "maid", "mail"
    , "main", "major", "make", "mammal", "man", "manage"
    , "mandate", "mango", "mansion", "manual", "maple", "marble"
    , "march", "margin", "marine", "market", "marriage", "mask"
    , "mass", "master", "match", "material", "math", "matrix"
    , "matter", "maximum", "maze", "meadow", "mean", "measure"
    , "meat", "mechanic", "medal", "media", "melody", "melt"
    , "member", "memory", "mention", "menu", "mercy", "merge"
    , "merit", "merry", "mesh", "message", "metal", "method"
    , "middle", "midnight", "milk", "million", "mimic", "mind"
    , "minimum", "minor", "minute", "miracle", "mirror", "misery"
    , "miss", "mistake", "mix", "mixed", "mixture", "mobile"
    , "model", "modify", "mom", "moment", "monitor", "monkey"
    , "monster", "month", "moon", "moral", "more", "morning"
    , "mosquito", "mother", "motion", "motor", "mountain", "mouse"
    , "move", "movie", "much", "muffin", "mule", "multiply"
    , "muscle", "museum", "mushroom", "music", "must", "mutual"
    , "myself", "mystery", "myth", "naive", "name", "napkin"
    , "narrow", "nasty", "nation", "nature", "near", "neck"
    , "need", "negative", "neglect", "neither", "nephew", "nerve"
    , "nest", "net", "network", "neutral", "never", "news"
    , "next", "nice", "night", "noble", "noise", "nominee"
    , "noodle", "normal", "north", "nose", "notable", "note"
    , "nothing", "notice", "novel", "now", "nuclear", "number"
    , "nurse", "nut", "oak", "obey", "object", "oblige"
    , "obscure", "observe", "obtain", "obvious", "occur", "ocean"
    , "october", "odor", "off", "offer", "office", "often"
    , "oil", "okay", "old", "olive", "olympic", "omit"
    , "once", "one", "onion", "online", "only", "open"
    , "opera", "opinion", "oppose", "option", "orange", "orbit"
    , "orchard", "order", "ordinary", "organ", "orient", "original"
    , "orphan", "ostrich", "other", "outdoor", "outer", "output"
    , "outside", "oval", "oven", "over", "own", "owner"
    , "oxygen", "oyster", "ozone", "pact", "paddle", "page"
    , "pair", "palace", "palm", "panda", "panel", "panic"
    , "panther", "paper", "parade", "parent", "park", "parrot"
    , "party", "pass", "patch", "path", "patient", "patrol"
    , "pattern", "pause", "pave", "payment", "peace", "peanut"
    , "pear", "peasant", "pelican", "pen", "penalty", "pencil"
    , "people", "pepper", "perfect", "permit", "person", "pet"
    , "phone", "photo", "phrase", "physical", "piano", "picnic"
    , "picture", "piece", "pig", "pigeon", "pill", "pilot"
    , "pink", "pioneer", "pipe", "pistol", "pitch", "pizza"
    , "place", "planet", "plastic", "plate", "play", "please"
    , "pledge", "pluck", "plug", "plunge", "poem", "poet"
    , "point", "polar", "pole", "police", "pond", "pony"
    , "pool", "popular", "portion", "position", "possible", "post"
    , "potato", "pottery", "poverty", "powder", "power", "practice"
    , "praise", "predict", "prefer", "prepare", "present", "pretty"
    , "prevent", "price", "pride", "primary", "print", "priority"
    , "prison", "private", "prize", "problem", "process", "produce"
    , "profit", "program", "project", "promote", "proof", "property"
    , "prosper", "protect", "proud", "provide", "public", "pudding"
    , "pull", "pulp", "pulse", "pumpkin", "punch", "pupil"
    , "puppy", "purchase", "purity", "purpose", "purse", "push"
    , "put", "puzzle", "pyramid", "quality", "quantum", "quarter"
    , "question", "quick", "quit", "quiz", "quote", "rabbit"
    , "raccoon", "race", "rack", "radar", "radio", "rail"
    , "rain", "raise", "rally", "ramp", "ranch", "random"
    , "range", "rapid", "rare", "rate", "rather", "raven"
    , "raw", "razor", "ready", "real", "reason", "rebel"
    , "rebuild", "recall", "receive", "recipe", "record", "recycle"
    , "reduce", "reflect", "reform", "refuse", "region", "regret"
    , "regular", "reject", "relax", "release", "relief", "rely"
    , "remain", "remember", "remind", "remove", "render", "renew"
    , "rent", "reopen", "repair", "repeat", "replace", "report"
    , "require", "rescue", "resemble", "resist", "resource", "response"
    , "result", "retire", "retreat", "return", "reunion", "reveal"
    , "review", "reward", "rhythm", "rib", "ribbon", "rice"
    , "rich", "ride", "ridge", "rifle", "right", "rigid"
    , "ring", "riot", "ripple", "risk", "ritual", "rival"
    , "river", "road", "roast", "robot", "robust", "rocket"
    , "romance", "roof", "rookie", "room", "rose", "rotate"
    , "rough", "round", "route", "royal", "rubber", "rude"
    , "rug", "rule", "run", "runway", "rural", "sad"
    , "saddle", "sadness", "safe", "sail", "salad", "salmon"
    , "salon", "salt", "salute", "same", "sample", "sand"
    , "satisfy", "satoshi", "sauce", "sausage", "save", "say"
    , "scale", "scan", "scare", "scatter", "scene", "scheme"
    , "school", "science", "scissors", "scorpion", "scout", "scrap"
    , "screen", "script", "scrub", "sea", "search", "season"
    , "seat", "second", "secret", "section", "security", "seed"
    , "seek", "segment", "select", "sell", "seminar", "senior"
    , "sense", "sentence", "series", "service", "session", "settle"
    , "setup", "seven", "shadow", "shaft", "shallow", "share"
    , "shed", "shell", "sheriff", "shield", "shift", "shine"
    , "ship", "shiver", "shock", "shoe", "shoot", "shop"
    , "short", "shoulder", "shove", "shrimp", "shrug", "shuffle"
    , "shy", "sibling", "sick", "side", "siege", "sight"
    , "sign", "silent", "silk", "silly", "silver", "similar"
    , "simple", "since", "sing", "siren", "sister", "situate"
    , "six", "size", "skate", "sketch", "ski", "skill"
    , "skin", "skirt", "skull", "slab", "slam", "sleep"
    , "slender", "slice", "slide", "slight", "slim", "slogan"
    , "slot", "slow", "slush", "small", "smart", "smile"
    , "smoke", "smooth", "snack", "snake", "snap", "sniff"
    , "snow", "soap", "soccer", "social", "sock", "soda"
    , "soft", "solar", "soldier", "solid", "solution", "solve"
    , "someone", "song", "soon", "sorry", "sort", "soul"
    , "sound", "soup", "source", "south", "space", "spare"
    , "spatial", "spawn", "speak", "special", "speed", "spell"
    , "spend", "sphere", "spice", "spider", "spike", "spin"
    , "spirit", "split", "spoil", "sponsor", "spoon", "sport"
    , "spot", "spray", "spread", "spring", "spy", "square"
    , "squeeze", "squirrel", "stable", "stadium", "staff", "stage"
    , "stairs", "stamp", "stand", "start", "state", "stay"
    , "steak", "steel", "stem", "step", "stereo", "stick"
    , "still", "sting", "stock", "stomach", "stone", "stool"
    , "story", "stove", "strategy", "street", "strike", "strong"
    , "struggle", "student", "stuff", "stumble", "style", "subject"
    , "submit", "subway", "success", "such", "sudden", "suffer"
    , "sugar", "suggest", "suit", "summer", "sun", "sunny"
    , "sunset", "super", "supply", "supreme", "sure", "surface"
    , "surge", "surprise", "surround", "survey", "suspect", "sustain"
    , "swallow", "swamp", "swap", "swarm", "swear", "sweet"
    , "swift", "swim", "swing", "switch", "sword", "symbol"
    , "symptom", "syrup", "system", "table", "tackle", "tag"
    , "tail", "talent", "talk", "tank", "tape", "target"
    , "task", "taste", "tattoo", "taxi", "teach", "team"
    , "tell", "ten", "tenant", "tennis", "tent", "term"
    , "test", "text", "thank", "that", "theme", "then"
    , "theory", "there", "they", "thing", "this", "thought"
    , "three", "thrive", "throw", "thumb", "thunder", "ticket"
    , "tide", "tiger", "tilt", "timber", "time", "tiny"
    , "tip", "tired", "tissue", "title", "toast", "tobacco"
    , "today", "toddler", "toe", "together", "toilet", "token"
    , "tomato", "tomorrow", "tone", "tongue", "tonight", "tool"
    , "tooth", "top", "topic", "topple", "torch", "tornado"
    , "tortoise", "toss", "total", "tourist", "toward", "tower"
    , "town", "toy", "track", "trade", "traffic", "tragic"
    , "train", "transfer", "trap", "trash", "travel", "tray"
    , "treat", "tree", "trend", "trial", "tribe", "trick"
    , "trigger", "trim", "trip", "trophy", "trouble", "truck"
    , "true", "truly", "trumpet", "trust", "truth", "try"
    , "tube", "tuition", "tumble", "tuna", "tunnel", "turkey"
    , "turn", "turtle", "twelve", "twenty", "twice", "twin"
    , "twist", "two", "type", "typical", "ugly", "umbrella"
    , "unable", "unaware", "uncle", "uncover", "under", "undo"
    , "unfair", "unfold", "unhappy", "uniform", "unique", "unit"
    , "universe", "unknown", "unlock", "until", "unusual", "unveil"
    , "update", "upgrade", "uphold", "upon", "upper", "upset"
    , "urban", "urge", "usage", "use", "used", "useful"
    , "useless", "usual", "utility", "vacant", "vacuum", "vague"
    , "valid", "valley", "valve", "van", "vanish", "vapor"
    , "various", "vast", "vault", "vehicle", "velvet", "vendor"
    , "venture", "venue", "verb", "verify", "version", "very"
    , "vessel", "veteran", "viable", "vibrant", "vicious", "victory"
    , "video", "view", "village", "vintage", "violin", "virtual"
    , "virus", "visa", "visit", "visual", "vital", "vivid"
    , "vocal", "voice", "void", "volcano", "volume", "vote"
    , "voyage", "wage", "wagon", "wait", "walk", "wall"
    , "walnut", "want", "warfare", "warm", "warrior", "wash"
    , "wasp", "waste", "water", "wave", "way", "wealth"
    , "weapon", "wear", "weasel", "weather", "web", "wedding"
    , "weekend", "weird", "welcome", "west", "wet", "whale"
    , "what", "wheat", "wheel", "when", "where", "whip"
    , "whisper", "wide", "width", "wife", "wild", "will"
    , "win", "window", "wine", "wing", "wink", "winner"
    , "winter", "wire", "wisdom", "wise", "wish", "witness"
    , "wolf", "woman", "wonder", "wood", "wool", "word"
    , "work", "world", "worry", "worth", "wrap", "wreck"
    , "wrestle", "wrist", "write", "wrong", "yard", "year"
    , "yellow", "you", "young", "youth", "zebra", "zero"
    , "zone", "zoo"