{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE NoImplicitPrelude #-}

-- CLI frontend for running and submitting analyses to the Dragons.dev web
-- service.
--
-- : out dragons-analyze
module Biz.Dragons.Analysis
  ( Analysis (..),
    Commit (..),
    run,
    main,
    test,
    git,
  )
where

import Alpha
import qualified Biz.Cli as Cli
import Biz.Test ((@=?))
import qualified Biz.Test as Test
import qualified Control.Concurrent.Async as Async
import qualified Data.Aeson as Aeson
import Data.Data (Data)
import qualified Data.List as List
import qualified Data.Map as Map
import qualified Data.String as String
import qualified Data.Text as Text
import qualified Data.Time.Clock as Time
import qualified Data.Time.Format as Time
import qualified System.Directory as Directory
import qualified System.Process as Process

main :: IO ()
main = Cli.main <| Cli.Plan help move test tidy

move :: Cli.Arguments -> IO ()
move args = gitDir +> run authors /> Aeson.encode +> putStrLn
  where
    gitDir =
      Cli.argument "git-dir"
        |> Cli.getArgWithDefault args ".git"
        |> Directory.makeAbsolute
    authors =
      -- i think this is not working? do i need optparse-applicative?
      -- see: https://github.com/docopt/docopt.hs/issues/25
      Cli.shortOption 'a'
        |> Cli.getAllArgs args
        |> map Text.pack

tidy :: cfg -> IO ()
tidy _ = pure ()

test :: Test.Tree
test = Test.group "Biz.Dragons.Analysis" [test_calculateScore]

help :: Cli.Docopt
help =
  [Cli.docopt|
dragons-analyze

Usage:
  dragons-analyze test
  dragons-analyze [--author=<email>]... <git-dir>

Options:
  -a, --author  List of active authors' emails.
|]

newtype Commit = Sha Text
  deriving (Eq, Data, Typeable, Ord, Generic, Show)

instance Aeson.ToJSON Commit

-- | The result of analyzing a git repo.
data Analysis = Analysis
  { -- | Where the repo is stored on the local disk.
    gitDir :: FilePath,
    -- | A path with no active contributors
    blackholes :: [Text],
    -- | A path with < 3 active contributors
    liabilities :: [Text],
    -- | Map of path to number of commits, for detecting paths that continually
    -- get rewritten.
    hotspotMap :: Map FilePath Integer,
    -- | Files that have not been touched in 6 months
    stale :: Map FilePath Integer,
    -- | Total score for the repo
    score :: Integer,
    -- | Total number of files
    totalFiles :: Integer,
    -- | The total number of commits
    totalCommits :: Integer,
    -- | List of all the active users we care about
    activeAuthors :: [Text],
    -- | Which commit this analysis was run against.
    commit :: Commit
  }
  deriving (Eq, Ord, Generic, Show, Data, Typeable)

instance Aeson.ToJSON Analysis

run :: [Text] -> FilePath -> IO Analysis
run activeAuthors bareRepo = do
  commit <- git bareRepo ["rev-parse", "HEAD"] /> Text.pack /> chomp /> Sha
  tree <-
    git
      bareRepo
      [ "ls-tree",
        "--full-tree",
        "--name-only",
        "-r", -- recurse into subtrees
        "HEAD"
      ]
      /> String.lines
  authors <- traverse (authorsFor bareRepo) tree :: IO [[(Text, Text, Text)]]
  let authorMap = zip tree authors :: [(FilePath, [(Text, Text, Text)])]
  stalenessMap <- traverse (lastTouched bareRepo) tree
  let blackholes =
        [ Text.pack path
          | (path, authors_) <- authorMap,
            null (map third authors_ `List.intersect` activeAuthors)
        ]
  let liabilities =
        [ Text.pack path
          | (path, authors_) <- authorMap,
            length (map third authors_ `List.intersect` activeAuthors) < 3
        ]
  let numBlackholes = realToFrac <| length blackholes
  let numLiabilities = realToFrac <| length liabilities
  let numTotal = realToFrac <| length tree
  hotspotMap <-
    Map.fromList </ Async.mapConcurrently getChangeCount tree
  totalCommits <-
    git bareRepo ["rev-list", "--count", "HEAD"]
      /> filter (/= '\n')
      /> readMaybe
      /> fromMaybe 0
  pure
    <| Analysis
      { gitDir = bareRepo,
        stale =
          Map.fromList
            <| [ (path, days)
                 | (path, Just days) <- stalenessMap,
                   days > 180
               ],
        score = calculateScore numTotal numBlackholes numLiabilities,
        totalFiles = toInteger <| length tree,
        ..
      }
  where
    third :: (a, b, c) -> c
    third (_, _, a) = a
    getChangeCount :: FilePath -> IO (FilePath, Integer)
    getChangeCount path =
      git bareRepo ["rev-list", "--count", "HEAD", "--", path]
        /> filter (/= '\n')
        /> readMaybe
        /> fromMaybe 0
        /> (path,)

-- | Given a git dir and a path inside the git repo, get information about the
-- authors.
authorsFor ::
  FilePath ->
  FilePath ->
  -- | returns (number of commits, author name, author email)
  IO [(Text, Text, Text)]
authorsFor gitDir path =
  Process.readProcess
    "git"
    [ "--git-dir",
      gitDir,
      "shortlog",
      "--numbered",
      "--summary",
      "--email",
      "HEAD",
      "--",
      path
    ]
    ""
    /> Text.pack
    /> Text.lines
    /> map (Text.break (== '\t'))
    /> map parseAuthor
  where
    parseAuthor (commits, author) =
      ( Text.strip commits,
        Text.strip <| Text.takeWhile (/= '<') author,
        Text.strip <| Text.dropAround (`elem` ['<', '>']) <| Text.dropWhile (/= '<') author
      )

-- | Run a git command on a repo
git ::
  -- | path to the git dir (bare repo)
  String ->
  -- | args to `git`
  [String] ->
  IO String
git bareRepo args = Process.readProcess "git" (["--git-dir", bareRepo] ++ args) ""

lastTouched :: FilePath -> FilePath -> IO (FilePath, Maybe Integer)
lastTouched bareRepo path = do
  now <- Time.getCurrentTime
  timestamp <-
    Process.readProcess
      "git"
      [ "--git-dir",
        bareRepo,
        "log",
        "-n1",
        "--pretty=%aI",
        "--",
        path
      ]
      ""
      /> filter (/= '\n')
      /> Time.parseTimeM True Time.defaultTimeLocale "%Y-%m-%dT%H:%M:%S%z"
  pure (path, calculateAge now </ timestamp)
  where
    calculateAge now n = round <| Time.diffUTCTime now n / Time.nominalDay

-- | Does the aggregate score calculation given number of files found to be
-- blackholes, liabilities, etc.
calculateScore :: Double -> Double -> Double -> Integer
calculateScore 0 _ _ = 0
calculateScore a 0 0 | a > 0 = 100
calculateScore a b c | a < 0 || b < 0 || c < 0 = 0
calculateScore numTotal numBlackholes numLiabilities =
  max 0 <. round
    <| maxScore
    * (weightedBlackholes + weightedLiabilities + numGood)
    / numTotal
  where
    weightedBlackholes = numBlackholes * (5 / 10)
    weightedLiabilities = numLiabilities * (7 / 10)
    numGood = numTotal - numBlackholes - numLiabilities
    maxScore = 100.0

test_calculateScore :: Test.Tree
test_calculateScore =
  Test.group
    "calculateScore"
    [ Test.unit "perfect score" <| 100 @=? calculateScore 100 0 0,
      Test.unit "all blackholes" <| 50 @=? calculateScore 100 100 0,
      Test.unit "all liabilities" <| 70 @=? calculateScore 100 0 100,
      Test.prop "never > 100" <| \t b l -> calculateScore t b l <= 100,
      Test.prop "never < 0" <| \t b l -> calculateScore t b l >= 0
    ]