From ceb193f85edba6e56ccc9b0ef7a40d8455490a13 Mon Sep 17 00:00:00 2001
From: Gabriel Ebner <gebner@gebner.org>
Date: Sun, 3 Mar 2019 10:16:33 +0100
Subject: [PATCH] cli: add diff command

This merges the external hledger-diff addon, which is now deprecated.
https://github.com/gebner/hledger-diff/
---
 hledger/Hledger/Cli/Commands.hs       |   2 +
 hledger/Hledger/Cli/Commands/Diff.hs  | 126 ++++++++++++++++++++++++++
 hledger/Hledger/Cli/Commands/Diff.md  |  35 +++++++
 hledger/Hledger/Cli/Commands/Diff.txt |  35 +++++++
 hledger/hledger.cabal                 |   4 +-
 hledger/package.yaml                  |   2 +
 6 files changed, 203 insertions(+), 1 deletion(-)
 create mode 100644 hledger/Hledger/Cli/Commands/Diff.hs
 create mode 100644 hledger/Hledger/Cli/Commands/Diff.md
 create mode 100644 hledger/Hledger/Cli/Commands/Diff.txt

diff --git a/hledger/Hledger/Cli/Commands.hs b/hledger/Hledger/Cli/Commands.hs
index 41bfb624b..ad3a5bf76 100644
--- a/hledger/Hledger/Cli/Commands.hs
+++ b/hledger/Hledger/Cli/Commands.hs
@@ -69,6 +69,7 @@ import Hledger.Cli.Commands.Checkdates
 import Hledger.Cli.Commands.Checkdupes
 import Hledger.Cli.Commands.Close
 import Hledger.Cli.Commands.Commodities
+import Hledger.Cli.Commands.Diff
 import Hledger.Cli.Commands.Files
 import Hledger.Cli.Commands.Help
 import Hledger.Cli.Commands.Import
@@ -102,6 +103,7 @@ builtinCommands = [
   ,(helpmode               , help')
   ,(importmode             , importcmd)
   ,(filesmode              , files)
+  ,(diffmode               , diff)
   ,(incomestatementmode    , incomestatement)
   ,(pricesmode             , prices)
   ,(printmode              , print')
diff --git a/hledger/Hledger/Cli/Commands/Diff.hs b/hledger/Hledger/Cli/Commands/Diff.hs
new file mode 100644
index 000000000..852ab6205
--- /dev/null
+++ b/hledger/Hledger/Cli/Commands/Diff.hs
@@ -0,0 +1,126 @@
+{-|
+
+The @diff@ command compares two diff.
+
+-}
+
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+module Hledger.Cli.Commands.Diff (
+  diffmode
+ ,diff
+) where
+
+import Data.List
+import Data.Function
+import Data.Ord
+import Data.Maybe
+import Data.Time
+import Data.Either
+import qualified Data.Text as T
+import System.Exit
+
+import Hledger
+import Prelude hiding (putStrLn)
+import Hledger.Utils.UTF8IOCompat (putStrLn)
+import Hledger.Cli.CliOptions
+
+-- | Command line options for this command.
+diffmode = hledgerCommandMode
+  $(embedFileRelative "Hledger/Cli/Commands/Diff.txt")
+  []
+  [generalflagsgroup2]
+  []
+  ([], Just $ argsFlag "[ACCOUNT] -f [JOURNAL1] -f [JOURNAL2]")
+
+data PostingWithPath = PostingWithPath {
+                     ppposting :: Posting,
+                     pptxnidx :: Int,
+                     pppidx :: Int }
+                 deriving (Show)
+
+instance Eq PostingWithPath where
+    a == b = pptxnidx a == pptxnidx b
+          && pppidx a == pppidx b
+
+pptxn :: PostingWithPath -> Transaction
+pptxn = fromJust . ptransaction . ppposting
+
+ppamountqty :: PostingWithPath -> Quantity
+ppamountqty = aquantity . head . amounts . pamount . ppposting
+
+allPostingsWithPath :: Journal -> [PostingWithPath]
+allPostingsWithPath j = do
+    (txnidx, txn) <- zip [0..] $ jtxns j
+    (pidx, p) <- zip [0..] $ tpostings txn
+    return PostingWithPath { ppposting = p, pptxnidx = txnidx, pppidx = pidx }
+
+binBy :: Ord b => (a -> b) -> [a] -> [[a]]
+binBy f = groupBy ((==) `on` f) . sortBy (comparing f)
+
+combine :: ([a], [b]) -> [Either a b]
+combine (ls, rs) = map Left ls ++ map Right rs
+
+combinedBinBy :: Ord b => (a -> b) -> ([a], [a]) -> [([a], [a])]
+combinedBinBy f = map partitionEithers . binBy (either f f) . combine
+
+greedyMaxMatching :: (Eq a, Eq b) => [(a,b)] -> [(a,b)]
+greedyMaxMatching = greedyMaxMatching' []
+
+greedyMaxMatching' :: (Eq a, Eq b) => [Either a b] -> [(a,b)] -> [(a,b)]
+greedyMaxMatching' alreadyUsed ((l,r):rest)
+  | Left l `elem` alreadyUsed || Right r `elem` alreadyUsed
+      = greedyMaxMatching' alreadyUsed rest
+  | otherwise = (l,r) : greedyMaxMatching' (Left l : Right r : alreadyUsed) rest
+greedyMaxMatching' _ [] = []
+
+dateCloseness :: (PostingWithPath, PostingWithPath) -> Integer
+dateCloseness = negate . uncurry (diffDays `on` tdate.pptxn)
+
+type Matching = [(PostingWithPath, PostingWithPath)]
+
+matching :: [PostingWithPath] -> [PostingWithPath] -> Matching
+matching ppl ppr = do
+    (left, right) <- combinedBinBy ppamountqty (ppl, ppr) -- TODO: probably not a correct choice of bins
+    greedyMaxMatching $ sortBy (comparing dateCloseness) [ (l,r) | l <- left, r <- right ]
+
+readJournalFile' :: FilePath -> IO Journal
+readJournalFile' fn =
+    readJournalFile definputopts {ignore_assertions_ = True} fn >>= either error' return
+
+matchingPostings :: AccountName -> Journal -> [PostingWithPath]
+matchingPostings acct j = filter ((== acct) . paccount . ppposting) $ allPostingsWithPath j
+
+pickSide :: Side -> (a,a) -> a
+pickSide L (l,_) = l
+pickSide R (_,r) = r
+
+unmatchedtxns :: Side -> [PostingWithPath] -> Matching -> [Transaction]
+unmatchedtxns s pp m =
+    map pptxn $ nubBy ((==) `on` pptxnidx) $ pp \\ map (pickSide s) m
+
+-- | The diff command.
+diff :: CliOpts -> Journal -> IO ()
+diff CliOpts{file_=[f1, f2], reportopts_=ReportOpts{query_=acctName}} _ = do
+  j1 <- readJournalFile' f1
+  j2 <- readJournalFile' f2
+
+  let acct = T.pack acctName
+  let pp1 = matchingPostings acct j1
+  let pp2 = matchingPostings acct j2
+
+  let m = matching pp1 pp2
+
+  let unmatchedtxn1 = unmatchedtxns L pp1 m
+  let unmatchedtxn2 = unmatchedtxns R pp2 m
+
+  putStrLn "Unmatched transactions in the first journal:\n"
+  mapM_ (putStr . showTransaction) unmatchedtxn1
+
+  putStrLn "Unmatched transactions in the second journal:\n"
+  mapM_ (putStr . showTransaction) unmatchedtxn2
+
+diff _ _ = do
+  putStrLn "Specifiy exactly two journal files"
+  exitFailure
diff --git a/hledger/Hledger/Cli/Commands/Diff.md b/hledger/Hledger/Cli/Commands/Diff.md
new file mode 100644
index 000000000..0aa868afb
--- /dev/null
+++ b/hledger/Hledger/Cli/Commands/Diff.md
@@ -0,0 +1,35 @@
+diff\
+Compares two journal files.  It looks at the transactions of a single
+account and prints out the transactions which are in one journal file but not
+in the other.
+
+This is particularly useful for reconciling existing journals with bank
+statements.  Many banks provide a way to export the transactions between two
+given dates, which can be converted to ledger files using custom scripts or
+read directly as CSV files.  With the diff command you can make sure that these
+transactions from bank match up exactly with the transactions in your ledger
+file, and that the resulting balance is correct.  (One possible concrete
+workflow is to have one ledger file per year and export the transactions for
+the current year, starting on January 1.)
+
+This command compares the postings of a single account (which needs to have the
+same name in both files), and only checks the amount of the postings (not the
+name or the date of the transactions).  Postings are compared (instead of
+transactions) so that you can combine multiple transactions from the bank
+statement in a single transaction in the ledger file.
+
+_FLAGS_
+
+Examples:
+
+```shell
+$ hledger diff assets:bank:giro -f 2014.journal -f bank.journal
+Unmatched transactions in the first journal:
+
+2014/01/01 Opening Balances
+    assets:bank:giro              EUR ...
+    ...
+    equity:opening balances       EUR -...
+
+Unmatched transactions in the second journal:
+```
diff --git a/hledger/Hledger/Cli/Commands/Diff.txt b/hledger/Hledger/Cli/Commands/Diff.txt
new file mode 100644
index 000000000..7faffc760
--- /dev/null
+++ b/hledger/Hledger/Cli/Commands/Diff.txt
@@ -0,0 +1,35 @@
+diff
+Compares two journal files. It looks at the transactions of a single
+account and prints out the transactions which are in one journal file
+but not in the other.
+
+This is particularly useful for reconciling existing journals with bank
+statements. Many banks provide a way to export the transactions between
+two given dates, which can be converted to ledger files using custom
+scripts or read directly as CSV files. With the diff command you can
+make sure that these transactions from bank match up exactly with the
+transactions in your ledger file, and that the resulting balance is
+correct. (One possible concrete workflow is to have one ledger file per
+year and export the transactions for the current year, starting on
+January 1.)
+
+This command compares the postings of a single account (which needs to
+have the same name in both files), and only checks the amount of the
+postings (not the name or the date of the transactions). Postings are
+compared (instead of transactions) so that you can combine multiple
+transactions from the bank statement in a single transaction in the
+ledger file.
+
+_FLAGS_
+
+Examples:
+
+$ hledger diff assets:bank:giro -f 2014.journal -f bank.journal
+Unmatched transactions in the first journal:
+
+2014/01/01 Opening Balances
+    assets:bank:giro              EUR ...
+    ...
+    equity:opening balances       EUR -...
+
+Unmatched transactions in the second journal:
diff --git a/hledger/hledger.cabal b/hledger/hledger.cabal
index 635dc40e7..b5b43eefa 100644
--- a/hledger/hledger.cabal
+++ b/hledger/hledger.cabal
@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 0682613dd00c2d6d52d5a9079bb63755cc25a0a09be9c996f55a0c0ad60fbafa
+-- hash: c936fb07d9099bcceeb59ad6e75b91aae6928718a53608affb3d9e7b6c4fe89d
 
 name:           hledger
 version:        1.14.1
@@ -72,6 +72,7 @@ extra-source-files:
     Hledger/Cli/Commands/Checkdupes.txt
     Hledger/Cli/Commands/Close.txt
     Hledger/Cli/Commands/Commodities.txt
+    Hledger/Cli/Commands/Diff.txt
     Hledger/Cli/Commands/Files.txt
     Hledger/Cli/Commands/Help.txt
     Hledger/Cli/Commands/Import.txt
@@ -121,6 +122,7 @@ library
       Hledger.Cli.Commands.Checkdupes
       Hledger.Cli.Commands.Close
       Hledger.Cli.Commands.Commodities
+      Hledger.Cli.Commands.Diff
       Hledger.Cli.Commands.Help
       Hledger.Cli.Commands.Files
       Hledger.Cli.Commands.Import
diff --git a/hledger/package.yaml b/hledger/package.yaml
index e657820a8..8c6c6982a 100644
--- a/hledger/package.yaml
+++ b/hledger/package.yaml
@@ -65,6 +65,7 @@ extra-source-files:
 - Hledger/Cli/Commands/Checkdupes.txt
 - Hledger/Cli/Commands/Close.txt
 - Hledger/Cli/Commands/Commodities.txt
+- Hledger/Cli/Commands/Diff.txt
 - Hledger/Cli/Commands/Files.txt
 - Hledger/Cli/Commands/Help.txt
 - Hledger/Cli/Commands/Import.txt
@@ -165,6 +166,7 @@ library:
   - Hledger.Cli.Commands.Checkdupes
   - Hledger.Cli.Commands.Close
   - Hledger.Cli.Commands.Commodities
+  - Hledger.Cli.Commands.Diff
   - Hledger.Cli.Commands.Help
   - Hledger.Cli.Commands.Files
   - Hledger.Cli.Commands.Import