hledger-overview fixing calculations

Turns out my monthsSinceBeginning was wrong, and this was throwing off my
runway and fire freedom. Bad news is my runway is shorter, good news is my time
until freedom is also shorter.

1 files changed, 40 insertions, 28 deletions

diff --git a/hledger-overview.hs b/hledger-overview.hs
index 701492a..1cb8c93 100755
--- a/hledger-overview.hs
+++ b/hledger-overview.hs
@@ -12,8 +12,8 @@ import qualified Data.List as List
 import Data.Text (Text, pack)
 import qualified Data.Text as T
 import qualified Data.Text.IO as IO
-import Data.Time.Calendar (Day, toGregorian)
-import Data.Time.Clock (UTCTime (utctDay), getCurrentTime)
+import Data.Time.Calendar (Day, toGregorian, fromGregorian)
+import Data.Time.Clock (UTCTime (..), getCurrentTime, diffUTCTime, diffTimeToPicoseconds)
 import Hledger
 
 today :: IO Day
@@ -41,11 +41,15 @@ main = do
   let btcBalUSD q = sum . map aquantity $ getTotalAmounts j t (defreportopts {value_ = inUsdNow}) q
   row "   btc" (prn $ btcBal "^as cur:BTC") (Just $ prn $ btcBalUSD "^as cur:BTC")
 
+  -- TODO: these metrics should have targets. if >target, print red, else print
+  -- green. Or limit: if <limit, print green, else print red
   sec "metrics"
   let netCash = bal "^as:me:cash ^li:me:cred cur:USD"
   let netWorth = balVal "^as ^li"
   row "  in - ex" (prn $ bal "^in ^ex" / monthsSinceBeginning t) $ Just "keep this negative to make progress"
   row "cred load" (prn netCash) $ Just "net cash: credit spending minus USD cash assets. keep it positive"
+  -- TODO: current month expenses should be lower than average month expenses
+  row "month exp" ("hledger bal ^ex:me -p thismonth") Nothing
   row "net worth" (prn netWorth) Nothing
   row "    level" (pr $ level netWorth) (Just $ "+" <> (prn $ netWorth - (unlevel $ roundTo' floor 1 $ level netWorth)))
   let levelup n = level netWorth & (+n) & roundTo' floor 1 & unlevel & \target -> target - netWorth
@@ -152,18 +156,19 @@ 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.
---
--- I think this is wronge because I need to take the monthly ammounts, but this
--- gives total amounts
+-- | Savings rate is a FIRE staple: (Income - Expenses) / Income * 100
 savingsRate :: Journal -> Day -> Quantity
-savingsRate j d = roundTo 2 $ allSavings / allIncome
+savingsRate j d =  roundTo 2 $ 100 * (income - expenses) / income
+  -- I used to do just savings/income, but this is wrong because it also
+  -- includes capital gains, which are not technically part of the savings rate.
+  --roundTo 2 $ savings / income
   where
-    allSavings = getTotal j d (defreportopts {value_ = inUsdNow}) query
+    opts = defreportopts {value_ = inUsdNow}
+    savings = getTotal j d opts query
     query = List.intercalate " " $ savingsAccounts
     -- gotta flip the sign because income is negative
-    allIncome = - getTotal j d (defreportopts {value_ = inUsdNow}) "^in"
+    income = - getTotal j d opts "^in"
+    expenses = getTotal j d opts "^ex"
 
 -- | The target fund is simply 25x your annual expenditure.
 --
@@ -175,43 +180,50 @@ savingsRate j d = roundTo 2 $ allSavings / allIncome
 targetFund :: Journal -> Day -> Quantity
 targetFund j d = 25 * yearlyExpenses
   where
-    yearlyExpenses = sum $ map aquantity $ total
+    yearlyExpenses = expenses / yearsSinceBeginning d
+    expenses = sum $ map aquantity $ total
     Right (query, _) = parseQuery d $ pack "^ex"
     (_, (Mixed total)) = balanceReport opts query j
     opts =
       defreportopts
-        { -- idk what the '2020 4' is for, but this actually results in the yearly
-          -- report for some reason
-          period_ = QuarterPeriod 2020 4,
-          value_ = Just $ AtNow $ Just "USD",
+        { value_ = inUsdNow,
           today_ = Just d
         }
 
--- | I have data going back to 2018.12. Use this for calculating averages per
--- month.
+-- | I have expense data going back to 2019.10. Use this for calculating
+-- averages per month.
 monthsSinceBeginning :: Day -> Quantity
-monthsSinceBeginning d = fromInteger $ (year - 2019) * 12 + toInteger month + 1
+monthsSinceBeginning d =
+  diffUTCTime (UTCTime d 0) start
+  & secondsToMonths
+  & mkDecimal
   where
-    (year, month, _) = toGregorian d
+    mkDecimal n = fromRational $ toRational n :: Decimal
+    secondsToMonths s = s / 60 / 60 / 24 / 7 / 4
+    start = UTCTime (fromGregorian 2019 10 1) 0
+
+yearsSinceBeginning :: Day -> Quantity
+yearsSinceBeginning d = monthsSinceBeginning d / 12
 
 -- | 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 =
-      savingsAccounts
-        & map (getTotal j d (defreportopts {value_ = inUsdNow, period_ = MonthPeriod 2020 10}))
-        & sum
-        & \n -> (n / monthsSinceBeginning d)
+whenFreedom j d = roundTo 1 $ targetFund j d / monthlySavings j d
+
+monthlySavings :: Journal -> Day -> Quantity
+monthlySavings j d =
+  savingsAccounts
+    & map (getTotal j d (defreportopts {value_ = inUsdNow}))
+    & sum
+    & \n -> (n / monthsSinceBeginning d)
 
 -- | How many months I could sustain myself with my cash and savings, given my
 -- current expenses.
 runway :: Journal -> Day -> (Quantity, Quantity, Quantity)
 runway j d = (nut, cash, cash / nut)
   where
-    nut = (sum $ map aquantity total) / monthsSinceBeginning d
+    nut = (sum $ map aquantity $ filter (\a -> acommodity a == "USD") total) / monthsSinceBeginning d
     (_, (Mixed total)) = monthlyBalance j d "^ex:me"
 
     cash =
@@ -223,7 +235,7 @@ runway j d = (nut, cash, cash / nut)
 ramen :: Journal -> Day -> (Quantity, Quantity, Quantity)
 ramen j d = (nut, cash, cash / nut)
   where
-    nut = (sum $ map aquantity total) / monthsSinceBeginning d
+    nut = (sum $ map aquantity $ filter (\a -> acommodity a == "USD") total) / monthsSinceBeginning d
     (_, (Mixed total)) = monthlyBalance j d "^ex:me:need"
     cash = getTotal j d (defreportopts {value_ = inUsdNow}) "^as:me:cash ^li:me:cred"