A ledger-compatible @balance@ command.

ledger's balance command is easy to use but not easy to describe
precisely.  In the examples below we'll use sample.ledger, which has the
following account tree:


The balance command shows accounts with their aggregate balances.
Subaccounts are displayed indented below their parent. Each balance is the
sum of any transactions in that account plus any balances from

 $ hledger -f sample.ledger balance
                 $-1  assets
                  $1    bank:saving
                 $-2    cash
                  $2  expenses
                  $1    food
                  $1    supplies
                 $-2  income
                 $-1    gifts
                 $-1    salary
                  $1  liabilities:debts

Usually, the non-interesting accounts are elided or omitted. Above,
@checking@ is omitted because it has no subaccounts and a zero balance.
@bank@ is elided because it has only a single displayed subaccount
(@saving@) and it would be showing the same balance as that ($1). Ditto
for @liabilities@. We will return to this in a moment.

The --depth argument can be used to limit the depth of the balance report.
So, to see just the top level accounts:

$ hledger -f sample.ledger balance --depth 1
                 $-1  assets
                  $2  expenses
                 $-2  income
                  $1  liabilities

This time liabilities has no displayed subaccounts (due to --depth) and
is not elided.

With one or more account pattern arguments, the balance command shows
accounts whose name matches one of the patterns, plus their parents
(elided) and subaccounts. So with the pattern o we get:

 $ hledger -f sample.ledger balance o
                  $1  expenses:food
                 $-2  income
                 $-1    gifts
                 $-1    salary

The o pattern matched @food@ and @income@, so they are shown. Unmatched
parents of matched accounts are also shown (elided) for context (@expenses@).

Also, the balance report shows the total of all displayed accounts, when
that is non-zero. Here, it is displayed because the accounts shown add up
to $-1.

Here is a more precise definition of \"interesting\" accounts in ledger's
balance report:

- an account which has just one interesting subaccount branch, and which
  is not at the report's maximum depth, is interesting if the balance is
  different from the subaccount's, and otherwise boring.

- any other account is interesting if it has a non-zero balance, or the -E
  flag is used.


module Hledger.Cli.Commands.Balance
import Hledger.Data.Utils
import Hledger.Data.Types
import Hledger.Data.Amount
import Hledger.Data.AccountName
import Hledger.Data.Posting
import Hledger.Data.Ledger
import Hledger.Cli.Options
#if __GLASGOW_HASKELL__ <= 610
import Prelude hiding ( putStr )
import System.IO.UTF8

-- | Print a balance report.
balance :: [Opt] -> [String] -> Journal -> IO ()
balance opts args j = do
  t <- getCurrentLocalTime
  putStr $ showBalanceReport opts (optsToFilterSpec opts args t) j

-- | Generate a balance report with the specified options for this ledger.
showBalanceReport :: [Opt] -> FilterSpec -> Journal -> String
showBalanceReport opts filterspec j = acctsstr ++ totalstr
      l = journalToLedger filterspec j
      acctsstr = unlines $ map showacct interestingaccts
            showacct = showInterestingAccount l interestingaccts
            interestingaccts = filter (isInteresting opts l) acctnames
            acctnames = sort $ tail $ flatten $ treemap aname accttree
            accttree = ledgerAccountTree (fromMaybe 99999 $ depthFromOpts opts) l
      totalstr | NoTotal `elem` opts = ""
               | notElem Empty opts && isZeroMixedAmount total = ""
               | otherwise = printf "--------------------\n%s\n" $ padleft 20 $ showMixedAmountWithoutPrice total
            total = sum $ map abalance $ ledgerTopAccounts l

-- | Display one line of the balance report with appropriate indenting and eliding.
showInterestingAccount :: Ledger -> [AccountName] -> AccountName -> String
showInterestingAccount l interestingaccts a = concatTopPadded [amt, "  ", depthspacer ++ partialname]
      amt = padleft 20 $ showMixedAmountWithoutPrice $ abalance $ ledgerAccount l a
      parents = parentAccountNames a
      interestingparents = filter (`elem` interestingaccts) parents
      depthspacer = replicate (indentperlevel * length interestingparents) ' '
      indentperlevel = 2
      -- the partial name is the account's leaf name, prefixed by the
      -- names of any boring parents immediately above
      partialname = accountNameFromComponents $ reverse (map accountLeafName ps) ++ [accountLeafName a]
          where ps = takeWhile boring parents where boring = not . (`elem` interestingparents)

-- | Is the named account considered interesting for this ledger's balance report ?
isInteresting :: [Opt] -> Ledger -> AccountName -> Bool
isInteresting opts l a
    | numinterestingsubs==1 && not atmaxdepth = notlikesub
    | otherwise = notzero || emptyflag
      atmaxdepth = isJust d && Just (accountNameLevel a) == d where d = depthFromOpts opts
      emptyflag = Empty `elem` opts
      acct = ledgerAccount l a
      notzero = not $ isZeroMixedAmount inclbalance where inclbalance = abalance acct
      notlikesub = not $ isZeroMixedAmount exclbalance where exclbalance = sumPostings $ apostings acct
      numinterestingsubs = length $ filter isInterestingTree subtrees
            isInterestingTree = treeany (isInteresting opts l . aname)
            subtrees = map (fromJust . ledgerAccountTreeAt l) $ ledgerSubAccounts l $ ledgerAccount l a