{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE ViewPatterns #-}

module Krank.Checkers.IssueTracker
  ( GitIssueRef (..),
    GitServer (..),
    Localized (..),
    checkText,
    extractIssues,
    gitRepoRe,
    serverDomain,
    extractIssuesOnALine,
  )
where

import Control.Exception.Safe (catch)
import Data.Aeson (Value, (.:))
import qualified Data.Aeson.Types as AesonT
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as ByteString
import qualified Data.Map as Map
import Data.Text (Text, pack)
import qualified Data.Text.Encoding as Text.Encoding
import Krank.Types
import qualified Network.HTTP.Req as Req
import PyF (fmt)
import qualified Text.Regex.PCRE.Heavy as RE
import Utils.Github (showGithubException)
import Utils.Gitlab (showGitlabException)

data GitServer = Github | Gitlab GitlabHost
  deriving (Eq, Show)

data IssueStatus = Open | Closed deriving (Eq, Show)

data GitIssueRef = GitIssueRef
  { server :: GitServer,
    owner :: Text,
    repo :: Text,
    issueNum :: Int
  }
  deriving (Eq, Show)

data GitIssueData = GitIssueData
  { gitIssue :: Localized GitIssueRef,
    issueStatus :: IssueStatus,
    issueTitle :: Text
  }
  deriving (Eq, Show)

serverDomain ::
  GitServer ->
  Text
serverDomain Github = "github.com"
serverDomain (Gitlab (GitlabHost h)) = h

-- | This regex represents a github/gitlab issue URL
gitRepoRe :: RE.Regex
-- NOTE: \b at the beginning is really import for performances
-- because it dramatically reduces the number of backtracks
gitRepoRe = [RE.re|\b(?>https?://)?(?>www\.)?([^/ ]+)/([^ ]+)/([^- ][^/ ]*)(?>/-)?/issues/([0-9]+)|]

-- | Extract all issues on one line and returns a list of the raw text associated with an issue
extractIssuesOnALine :: ByteString -> [(Int, GitIssueRef)]
extractIssuesOnALine lineContent = map f (RE.scan gitRepoRe lineContent)
  where
    f (match, [domain, owner, repo, ByteString.readInt -> Just (issueNo, _)]) = (colNo, GitIssueRef provider (Text.Encoding.decodeUtf8 owner) (Text.Encoding.decodeUtf8 repo) issueNo)
      where
        colNo = 1 + ByteString.length (fst $ ByteString.breakSubstring match lineContent)
        provider
          | domain == "github.com" = Github
          -- TODO: We suppose that all other cases are gitlab
          -- The only thing we risk here is a query with the wrong
          -- API to an irrelevant host.
          | otherwise = Gitlab (GitlabHost $ Text.Encoding.decodeUtf8 domain)
    -- This case seems impossible, the reasons for pattern match issues are:
    --  A number of items different than 4 in the list: there is only 4 matching groups in the regex
    --  An invalid `decimal` conversion. That's impossible either
    --  because the pattern for the issue number is `[0-9]+`
    f res = error ("Error: impossible match" <> show res)

-- | Extract all issues correctly localized
-- Note: we use 'ByteString' internally. This way we do not have to
-- care about the possible encoding of the input files.
-- In programming world, we mostly use ascii variants. This gives a
-- few performance improvement compared to initially converting
-- everything to 'Text' and search on it.
extractIssues ::
  -- | Path of the file
  FilePath ->
  -- | Content of the file
  ByteString ->
  [Localized GitIssueRef]
extractIssues filePath toCheck = concat (zipWith extract [1 ..] (ByteString.lines toCheck))
  where
    extract lineNo lineContent = map f (extractIssuesOnALine lineContent)
      where
        f (colNo, gitIssue) = Localized (SourcePos filePath lineNo colNo) gitIssue

-- Supports only github for the moment
issueUrl ::
  GitIssueRef ->
  Req.Url 'Req.Https
issueUrl issue = case server issue of
  Github -> Req.https "api.github.com" Req./: "repos" Req./: owner issue Req./: repo issue Req./: "issues" Req./~ issueNum issue
  Gitlab (GitlabHost host) -> Req.https host Req./: "api" Req./: "v4" Req./: "projects" Req./: [fmt|{owner issue}/{repo issue}|] Req./: "issues" Req./~ issueNum issue

-- try Issue can fail, on non-2xx HTTP response
tryRestIssue ::
  MonadKrank m =>
  Localized GitIssueRef ->
  m Value
tryRestIssue locIssue = do
  let issue = unLocalized locIssue
  let url = issueUrl issue
  headers <- headersFor issue
  krankRunRESTRequest url headers

headersFor ::
  MonadKrank m =>
  GitIssueRef ->
  m (Req.Option 'Req.Https)
headersFor issue = do
  mGithubKey <- krankAsks githubKey
  mGitlabKeys <- krankAsks gitlabKeys
  case server issue of
    Github -> case mGithubKey of
      Just (GithubKey token) -> pure $ Req.oAuth2Token (Text.Encoding.encodeUtf8 token)
      Nothing -> pure mempty
    Gitlab host -> case Map.lookup host mGitlabKeys of
      Just (GitlabKey token) -> pure $ Req.header "PRIVATE-TOKEN" (Text.Encoding.encodeUtf8 token)
      Nothing -> pure mempty

httpExcHandler ::
  MonadKrank m =>
  GitServer ->
  Req.HttpException ->
  m Value
httpExcHandler gitServer exc =
  pure . AesonT.object $ [("error", AesonT.String . pack $ [fmt|{(showGitServerException gitServer exc)}|])]

showGitServerException ::
  GitServer ->
  Req.HttpException ->
  Text
showGitServerException Github exc = showGithubException exc
showGitServerException (Gitlab _) exc = showGitlabException exc

restIssue ::
  MonadKrank m =>
  Localized GitIssueRef ->
  m Value
restIssue issue = catch (tryRestIssue issue) (httpExcHandler . server . unLocalized $ issue)

statusParser ::
  Value ->
  Either Text IssueStatus
statusParser (AesonT.Object o) = do
  let state :: AesonT.Result String = AesonT.parse (.: "state") o
  readState state
  where
    readState (AesonT.Success status) = case status of
      "closed" -> Right Closed -- Both Gitlab and Github use the same keyword for closed
      "open" -> Right Open -- Github uses the 'open' status
      "opened" -> Right Open -- Gitlab uses the 'opened' status
      _ -> Left [fmt|Could not parse status '{status}'|]
    readState (AesonT.Error _) = Left $ errorParser o
statusParser _ = Left "invalid JSON"

titleParser ::
  Value ->
  Either Text Text
titleParser (AesonT.Object o) = do
  let title :: AesonT.Result String = AesonT.parse (.: "title") o
  Right $ readTitle title
  where
    readTitle (AesonT.Success title) = pack title
    readTitle (AesonT.Error _) = "invalid JSON"
titleParser _ = Left "invalid JSON"

errorParser ::
  AesonT.Object ->
  Text
errorParser o = do
  let err = AesonT.parse (.: "error") o
  readErr err
  where
    readErr (AesonT.Success errText) = pack errText
    readErr (AesonT.Error _) = "invalid JSON"

gitIssuesWithStatus ::
  MonadKrank m =>
  [Localized GitIssueRef] ->
  m [Either (Text, Localized GitIssueRef) GitIssueData]
gitIssuesWithStatus issues = do
  jsonData <- krankMapConcurrently restIssue issues
  let statuses = fmap statusParser jsonData
  let titles = fmap titleParser jsonData
  pure $ zipWith3 f issues statuses titles
  where
    f issue (Left err) _ = Left (err, issue)
    f issue _ (Left err) = Left (err, issue)
    f issue (Right status) (Right title) = Right $ GitIssueData issue status title

issueToLevel ::
  GitIssueData ->
  ViolationLevel
issueToLevel i = case issueStatus i of
  Open -> Info
  Closed -> Error

issueToMessage ::
  GitIssueData ->
  Text
issueToMessage i =
  case issueStatus i of
    Open -> [fmt|the issue is still Open\ntitle: {title}|]
    Closed -> [fmt|the issue is now Closed - You can remove the workaround you used there\ntitle: {title}|]
  where
    title = issueTitle i

issuePrintUrl :: GitIssueRef -> Text
issuePrintUrl GitIssueRef {owner, repo, server, issueNum} = [fmt|IssueTracker check for https://{serverDomain server}/{owner}/{repo}/issues/{issueNum}|]

checkText ::
  MonadKrank m =>
  FilePath ->
  ByteString ->
  m [Violation]
checkText path t = do
  let issues = extractIssues path t
  isDryRun <- krankAsks dryRun
  if isDryRun
    then
      pure $
        fmap
          ( \issue ->
              Violation
                { checker = issuePrintUrl . unLocalized $ issue,
                  level = Info,
                  message = "Dry run",
                  location = getLocation (issue :: Localized GitIssueRef)
                }
          )
          issues
    else do
      issuesWithStatus <- gitIssuesWithStatus issues
      pure $ fmap f issuesWithStatus
  where
    f (Left (err, issue)) =
      Violation
        { checker = issuePrintUrl . unLocalized $ issue,
          level = Warning,
          message = "Error when calling the API:\n" <> err,
          location = getLocation (issue :: Localized GitIssueRef)
        }
    f (Right issue) =
      Violation
        { checker = issuePrintUrl (unLocalized . gitIssue $ issue),
          level = issueToLevel issue,
          message = issueToMessage issue,
          location = getLocation (gitIssue issue :: Localized GitIssueRef)
        }