{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

-- Developer allocation
--
-- : out devalloc
-- : dep clay
-- dep cmark
-- sys cmark
-- : dep envy
-- : dep github
-- : dep lucid
-- : dep protolude
-- : dep req
-- : dep servant
-- : dep servant-lucid
-- : dep servant-server
-- : dep uuid
-- : dep vector
-- : dep warp
module Biz.Devalloc
  ( main,
    test,
  )
where

import Alpha hiding ((<.>))
import Biz.App (CSS (..), HtmlApp (..))
import qualified Biz.Look
import qualified Clay
import qualified Control.Exception as Exception
import qualified Data.Aeson as Aeson
import qualified Data.ByteString.Lazy as LBS
import qualified Data.List as List
import qualified Data.String as String
import qualified Data.Text as Text
import qualified Data.Text.Encoding as Encoding
import qualified Data.Time.Clock as Clock
import qualified Data.Time.Format as Time
import Data.Vector (Vector)
import qualified Data.Vector as Vector
import qualified GitHub
import qualified Lucid
import qualified Lucid.Base as Lucid
import qualified Lucid.Servant as Lucid
import Network.HTTP.Req ((/:), (=:))
import qualified Network.HTTP.Req as Req
import qualified Network.Wai as Wai
import qualified Network.Wai.Handler.Warp as Warp
import Network.Wai.Middleware.RequestLogger (logStdout)
import Servant
import Servant.API.Generic (ToServantApi, genericApi, toServant, (:-))
import Servant.HTML.Lucid
import Servant.Server.Generic (AsServer)
import qualified System.Directory as Directory
import qualified System.Envy as Envy
import System.FilePath ((<.>), (</>))
import qualified System.Process as Process
import qualified Web.FormUrlEncoded

main :: IO ()
main = Exception.bracket startup shutdown run
  where
    startup = do
      cfg <- Envy.decodeWithDefaults Envy.defConfig
      oAuthArgs <- Envy.decodeWithDefaults Envy.defConfig
      putText "@"
      putText "devalloc"
      putText <| "port: " <> (show <| port cfg)
      putText <| "depo: " <> (Text.pack <| depo cfg)
      return (cfg, serve paths (toServant <| htmlApp cfg oAuthArgs))
    shutdown :: (Config, Application) -> IO ()
    shutdown _ = pure ()
    run :: (Config, Wai.Application) -> IO ()
    run (cfg, app) = Warp.run (port cfg) (logStdout app)

test :: IO Analysis
test = test_analyzeGitHub

data Config = Config
  { port :: Warp.Port,
    -- | The repo depo! Depository of repositories!
    depo :: FilePath
  }
  deriving (Generic, Show)

instance Envy.DefConfig Config where
  defConfig =
    Config
      { port = 8005,
        depo = "_/var/devalloc/depo"
      }

instance Envy.FromEnv Config

-- | These are arguments that a 3rd-party OAuth provider needs in order for us
-- to authenticate a user.
data OAuthArgs = OAuthArgs
  { githubClientSecret :: Text,
    githubClientId :: Text,
    githubState :: Text
  }
  deriving (Generic, Show)

instance Envy.DefConfig OAuthArgs where
  defConfig =
    OAuthArgs
      { githubClientSecret = mempty,
        githubClientId = mempty,
        githubState = mempty
      }

instance Envy.FromEnv OAuthArgs

-- | Wraps pages in default HTML
instance Lucid.ToHtml a => Lucid.ToHtml (HtmlApp a) where
  toHtmlRaw = Lucid.toHtml
  toHtml (HtmlApp x) =
    Lucid.doctypehtml_ <| do
      Lucid.head_ <| do
        Lucid.meta_ [Lucid.charset_ "utf-8"]
        jsRef "//unpkg.com/turbolinks@5.2.0/dist/turbolinks.js"
        cssRef "/css/main.css"
      Lucid.body_ (Lucid.toHtml x)
    where
      jsRef _href =
        Lucid.with
          (Lucid.script_ mempty)
          [ Lucid.makeAttribute "src" _href,
            Lucid.makeAttribute "async" mempty,
            Lucid.makeAttribute "defer" mempty
          ]
      cssRef _href =
        Lucid.with
          (Lucid.link_ mempty)
          [ Lucid.rel_ "stylesheet",
            Lucid.type_ "text/css",
            Lucid.href_ _href
          ]

-- * paths and pages

data Paths path = Paths
  { home :: path :- Get '[HTML] (HtmlApp Home),
    githubAuth ::
      path :- "auth" :> "github" :> "callback"
        :> QueryParam "code" Text
        :> Get '[HTML] (HtmlApp SelectRepo),
    githubAnalysis ::
      path :- "analysis" :> "github"
        :> Capture "user" Text
        :> Capture "repo" Text
        :> Get '[HTML] (HtmlApp Analysis),
    css :: path :- "css" :> "main.css" :> Get '[CSS] Text
  }
  deriving (Generic)

paths :: Proxy (ToServantApi Paths)
paths = genericApi (Proxy :: Proxy Paths)

-- | Main HTML handlers for all paths.
htmlApp :: Config -> OAuthArgs -> Paths AsServer
htmlApp cfg oAuthArgs =
  Paths
    { home = page (Home oAuthArgs),
      githubAuth = auth oAuthArgs,
      githubAnalysis = \user repo ->
        liftIO <| analyzeGitHub cfg user repo >>= HtmlApp .> pure,
      css = look
    }
  where
    page = HtmlApp .> pure
    look =
      return <. toStrict <. Clay.render <| do
        Biz.Look.fuckingStyle
        "body" Clay.? Biz.Look.fontStack

-- | The front page pitch. Eventually I'd like to load the content from markdown
-- files or some other store of data so I can A/B test.
newtype Home = Home OAuthArgs

instance Lucid.ToHtml Home where
  toHtmlRaw = Lucid.toHtml
  toHtml (Home oAuthArgs) = do
    Lucid.h1_ "Devalloc"
    Lucid.p_
      "Devalloc analyzes your codebase trends, finds patterns \
      \ in how your developers work, and protects against tech debt."
    Lucid.p_ "Just hook it up to your CI system - it will warn you when it finds a problem."
    Lucid.toHtml <| loginButton oAuthArgs
    Lucid.h2_ "Identify blackholes in your codebase"
    Lucid.p_
      "What if none of your active employees have touched some part of the codebase? \
      \ This happens too often with legacy code, and then it turns into a huge source of tech debt. \
      \ Devalloc finds these \"blackholes\" and warns you about them so you can be proactive in eliminating tech debt."
    Lucid.toHtml <| loginButton oAuthArgs
    Lucid.h2_ "Protect against lost knowledge"
    Lucid.p_ "Not everyone can know every part of a codebase. By finding pieces of code that only 1 or 2 people have touched, devalloc identifes siloed knowledge. This allows you to protect against the risk of this knowledge leaving the company if an employee leaves."
    Lucid.toHtml <| loginButton oAuthArgs
    Lucid.h2_ "Don't just measure code coverage - also know your dev coverage"
    Lucid.p_ "No matter how smart your employees are, if you are under- or over-utilizing your developers then you will never get optimal performance from your team."
    Lucid.ul_ <| do
      Lucid.li_ "Find developer hot spots in your code: which pieces of code get continually rewritten, taking up valuable dev time?"
      Lucid.li_ "Know how your devs work best: which ones have depth of knowledge, and which ones have breadth?"

    Lucid.p_ "(Paid only)"
    Lucid.toHtml <| loginButton oAuthArgs
    Lucid.h2_ "See how your teams *actually* organize themselves with cluster analysis"
    Lucid.p_ "Does your team feel splintered or not cohesive? Which developers work best together? Devalloc analyzes the collaboration patterns between devs and helps you form optimal pairings and teams based on shared code and mindspace."
    Lucid.p_ "(Paid only)"
    Lucid.toHtml <| loginButton oAuthArgs

-- | A type for parsing JSON auth responses, used in 'getAccessToken' below.
-- Should be moved to Biz.Auth with others.
data OAuthResponse = OAuthResponse
  { access_token :: Text,
    scope :: Text,
    token_type :: Text
  }
  deriving (Generic, Aeson.FromJSON)

auth :: OAuthArgs -> Maybe Text -> Handler (HtmlApp SelectRepo)
auth _ Nothing = panic "no code from github api"
auth OAuthArgs {..} (Just code) =
  liftIO <| getAccessToken
    >>= getRepos
    >>= \case
      Left err -> panic <| show err
      Right repos -> pure <. HtmlApp <| SelectRepo repos
  where
    getRepos oAuthToken =
      GitHub.github
        (GitHub.OAuth <| Encoding.encodeUtf8 oAuthToken)
        (GitHub.currentUserReposR GitHub.RepoPublicityAll GitHub.FetchAll)
    getAccessToken =
      accessTokenRequest
        >>= Req.responseBody
        /> access_token
        /> return
        |> Req.runReq Req.defaultHttpConfig
    accessTokenRequest =
      Req.req
        Req.POST
        (Req.https "github.com" /: "login" /: "oauth" /: "access_token")
        Req.NoReqBody
        Req.jsonResponse
        <| "client_id" =: githubClientId
        <> "client_secret" =: githubClientSecret
        <> "code" =: code
        <> "state" =: githubState

-- | This view presents a list of repos to select for analysis.
newtype SelectRepo = SelectRepo (Vector GitHub.Repo)

instance Lucid.ToHtml SelectRepo where
  toHtmlRaw = Lucid.toHtml
  toHtml (SelectRepo repos) = do
    Lucid.h1_ "Select a repo to analyze"
    Lucid.ul_ <| forM_ (Vector.toList repos) <| \repo ->
      Lucid.li_
        <. Lucid.a_
          [ Lucid.linkHref_ "/"
              <| fieldLink
                githubAnalysis
                (GitHub.untagName <| GitHub.simpleOwnerLogin <| GitHub.repoOwner repo)
                (GitHub.untagName <| GitHub.repoName repo)
          ]
        <. Lucid.toHtml
        <. GitHub.untagName
        <| GitHub.repoName repo

-- * parts

-- | Utility for turning a list of tuples into a URL querystring.
encodeParams :: [(Text, Text)] -> Text
encodeParams =
  Encoding.decodeUtf8
    <. LBS.toStrict
    <. Web.FormUrlEncoded.urlEncodeParams

-- | Login button for GitHub.
loginButton :: OAuthArgs -> Lucid.Html ()
loginButton OAuthArgs {..} =
  Lucid.a_
    [ Lucid.href_
        <| "https://github.com/login/oauth/authorize?"
        <> encodeParams
          [ ("client_id", githubClientId),
            ("state", githubState)
          ]
    ]
    "Get Started with GitHub"

-- * analysis

-- | The result of analyzing a git repo.
data Analysis = Analysis
  { -- | Where the repo is stored on the local disk.
    bareRepo :: FilePath,
    -- | A path with no active contributors
    blackholes :: [Text],
    -- | A path with < 3 active contributors
    liabilities :: [Text],
    -- | Files that have not been touched in 6 months
    stale :: [(FilePath, Int)],
    -- | Total score for the repo
    score :: Int,
    -- | List of all the active users we care about
    activeAuthors :: [Text]
  }
  deriving (Show)

instance Lucid.ToHtml Analysis where
  toHtmlRaw = Lucid.toHtml
  toHtml = render .> Lucid.toHtml
    where
      render :: Analysis -> Lucid.Html ()
      render Analysis {..} =
        Lucid.div_ <| do
          Lucid.h1_ "Analysis Results"
          Lucid.h3_ "score:"
          Lucid.p_ <| Lucid.toHtml <| Text.pack <| show score
          Lucid.h3_ "blackholes:"
          Lucid.ul_ <| do
            mapM_ (Lucid.toHtml .> Lucid.li_) blackholes
          Lucid.h3_ "stale files:"
          Lucid.ul_ <| do
            forM_ stale <| \(path, days) ->
              Lucid.li_ <| Lucid.toHtml <| path <> " (" <> show days <> " days)"

-- | Takes a list of active authors and a path to a bare git repo and runs a
-- regular analysis
analyze :: [Text] -> FilePath -> IO Analysis
analyze activeAuthors bareRepo = do
  tree <-
    Process.readProcess
      "git"
      [ "--git-dir",
        bareRepo,
        "ls-tree",
        "--full-tree",
        "--name-only",
        "-r", -- recurse into subtrees
        "HEAD"
      ]
      ""
      /> String.lines
  authors <- mapM (authorsFor bareRepo) tree :: IO [[(Text, Text, Text)]]
  let authorMap =
        zipWith
          ( \path authors_ ->
              (path, authors_)
          )
          tree
          authors ::
          [(FilePath, [(Text, Text, Text)])]
  stalenessMap <- mapM (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 = frac <| length blackholes
  let numLiabilities = frac <| length liabilities
  let numTotal = length tree
  return
    Analysis
      { stale =
          [ (path, days)
            | (path, days) <- stalenessMap,
              days > 180
          ],
        score =
          maxScore
            * ( (numBlackholes * frac (5 // 10)) * (numLiabilities * frac (7 // 10))
                  * (numTotal - numBlackholes - numLiabilities)
              )
            `div` numTotal,
        ..
      }
  where
    (//) = div
    frac = fromIntegral :: Num a => Int -> a
    maxScore = 10
    third :: (a, b, c) -> c
    third (_, _, a) = a

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

-- | Given a git dir and a path inside the git repo, return a list of tuples
-- with number of commits and author.
authorsFor ::
  FilePath ->
  FilePath ->
  -- | Returns (number of commits, author name, author email)
  IO [(Text, Text, Text)]
authorsFor gitDir path =
  -- git shortlog writes to stderr for some reason, so we can't just use
  -- Process.readProcess
  Process.readProcess
    "git"
    [ "--git-dir",
      gitDir,
      "shortlog",
      "--numbered",
      "--summary",
      "--email",
      "HEAD",
      "--",
      path
    ]
    ""
    /> Text.pack
    /> Text.lines
    /> map (Text.break (== '\t'))
    /> map
      ( \(commits, author) ->
          ( Text.strip commits,
            Text.strip <| Text.takeWhile (/= '<') author,
            Text.strip <| Text.dropAround (`elem` ['<', '>']) <| Text.dropWhile (/= '<') author
          )
      )

-- | Clones a repo from GitHub and does the analysis.
-- TODO: break this up into fetchGitHub and analyze functions.
analyzeGitHub ::
  Config ->
  -- | GitHub owner
  Text ->
  -- | GitHub repo
  Text ->
  IO Analysis
analyzeGitHub cfg o r = do
  -- I currently have no way of getting active users... getting a list of
  -- collaborators on a repo requires authentication for some reason.
  --
  -- If the owner is an organization, then we can just use org members, which is
  -- public too. And if the auth'ed user is a member of the org, then it returns
  -- all of the members, not just public ones, so that will work just fine.
  --
  -- In the meantime, what do? Maybe get the number of commits, and consider
  -- "active users" as the top 10% in terms of number of commits? Or ask for a
  -- list explicitly? If it is a personal repo, then I can assume that the owner
  -- is the only regular contributor, at least for now.
  --
  -- Right activeUsers <- GitHub.github () (GitHub.collaboratorsOnR ghOwner ghRepo GitHub.FetchAll)
  Right user <-
    GitHub.github
      ()
      ( GitHub.userInfoForR
          <| GitHub.mkName (Proxy :: Proxy GitHub.User) o
      )
  -- assume the only active author is the owner, for now
  -- TODO: should be userEmail but that requires authentication?
  let activeAuthors = [require "user email" <| GitHub.userName user]
  Right repo <- GitHub.github () (GitHub.repositoryR ghOwner ghRepo)
  bareRepo <- fetchBareRepo cfg <. GitHub.getUrl <| GitHub.repoHtmlUrl repo
  analyze activeAuthors bareRepo
  where
    ghOwner = GitHub.mkName (Proxy :: Proxy GitHub.Owner) o
    ghRepo = GitHub.mkName (Proxy :: Proxy GitHub.Repo) r

test_analyzeGitHub :: IO Analysis
test_analyzeGitHub = analyzeGitHub Envy.defConfig "bsima" "bin"

-- | Clone the repo to @<Config.depo>/<url>@. If repo already exists, just do a
-- @git fetch@. Returns the full path to the local repo.
fetchBareRepo :: Config -> Text -> IO FilePath
fetchBareRepo Config {depo} url =
  Directory.doesPathExist worktree
    >>= fetchOrClone
    >> return worktree
  where
    fetchOrClone True =
      Process.callProcess "git" ["--git-dir", worktree, "fetch", "origin"]
    fetchOrClone False =
      Process.callProcess "git" ["clone", "--bare", "--", Text.unpack url, worktree]
    removeScheme :: Text -> FilePath
    removeScheme u = Text.unpack <. Text.dropWhile (== '/') <. snd <| Text.breakOn "//" u
    worktree = depo </> removeScheme url <.> "git"