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+#!/usr/bin/env runhaskell
+-- | Calculations for FIRE (financial independence, retire early)
+module Main where
+import Hledger
+import Data.Decimal (DecimalRaw, roundTo)
+import Data.Either (fromRight)
+import Data.Time.Calendar (Day)
+import Data.Time.Clock (UTCTime(utctDay), getCurrentTime)
+import Data.Text (pack)
+
+main = do
+  j <- getJournal
+  today <- getCurrentTime >>= return . utctDay
+  say ["savings rate:", show $ savingsRate j today]
+  say ["target fund:", show $ targetFund j today]
+  say ["when free:", show $ whenFreedom j today]
+
+say = putStrLn . unwords
+
+getJournal :: IO Journal
+getJournal = do
+  jp <- defaultJournalPath
+  let opts = definputopts { auto_ = True }
+  ej <- readJournalFile opts jp
+  return $ fromRight undefined ej
+
+-- | Helper for getting the total out of a balance report.
+getTotal :: Journal -> Day -> String -> Quantity
+getTotal j d q = head $ map aquantity $ total
+  where
+    opts = defreportopts { balancetype_ = CumulativeChange }
+    (query, _) = parseQuery d $ pack q
+    (_, (Mixed total)) = balanceReport opts query j
+
+-- | These are the accounts that I consider a part of my savings and not my
+-- cash-spending accounts.
+savingsAccounts :: [String]
+savingsAccounts =
+  [ "as:me:save", "as:me:vest" ]
+
+-- | Savings rate is a FIRE staple. Basically take your savings and divide it by
+-- your income on a monthly basis.
+--
+savingsRate :: Journal -> Day -> Quantity
+savingsRate j d = roundTo 2 $ monthlySavings / monthlyIncome
+  where
+    monthlySavings = sum $ map (getTotal j d) $ map appendMonthly savingsAccounts
+    appendMonthly s = s ++ " --monthly"
+    monthlyIncome = getTotal j d "^in --monthly"
+
+-- | The target fund is simply 25x your annual expenditure.
+--
+-- This is going to be incomplete until I have a full year of
+-- expenses.. currently, I just use my most recent quarter times 4 as a proxy
+-- for the yearly expenses.
+--
+-- Assumptions: 4% withdrawal rate, 3-5% return on investments.
+--
+targetFund :: Journal -> Day -> Quantity
+targetFund j d = 25 * yearlyExpenses
+  where
+    yearlyExpenses = 4 * quarterlyExpenses
+    quarterlyExpenses = sum $ map aquantity $ total
+    (query, _) = parseQuery d $ pack "^ex -p thisquarter --forecast cur:USD"
+    (_, (Mixed total)) = balanceReport opts query j
+    opts = defreportopts
+
+-- | How long until I can live off of my savings and investment returns?
+--
+-- Return integer is number of months until I'm free.
+--
+whenFreedom :: Journal -> Day -> Quantity
+whenFreedom j d = roundTo 1 $ targetFund j d / monthlySavings
+  where
+    monthlySavings = sum $ map (getTotal j d) $ map appendMonthly savingsAccounts
+    appendMonthly s = s ++ " --monthly"