diff --git a/ChangeLog.md b/ChangeLog.md
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+# Changelog for slack-progressbar
+
+## Unreleased changes
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright Author name here (c) 2020
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Author name here nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# slack-progressbar
diff --git a/Setup.hs b/Setup.hs
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+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/app/Main.hs b/app/Main.hs
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+++ b/app/Main.hs
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+{-# LANGUAGE OverloadedStrings, QuasiQuotes #-}
+
+module Main where
+
+import Control.Concurrent
+import Control.Monad.Except
+import Data.Maybe
+import Data.String.Interpolate.IsString
+import Web.Slack.ProgressBar
+
+mySlackConfig :: SlackConfig
+mySlackConfig = SlackConfig { slackApiToken = "TODO" }
+
+main :: IO ()
+main = void $ runExceptT $ do
+  let progressBarInfo = ProgressBarInfo {
+        progressBarInfoTopMessage = Just "Top message"
+        , progressBarInfoBottomMessage = Just "Bottom message"
+        , progressBarInfoSize = Just 0
+        , progressBarInfoAttachments = Just []
+        }
+
+  progressBar <- ExceptT $ createProgressBar mySlackConfig "test-channel" progressBarInfo
+
+  forM_ [10, 20, 30, 40, 50, 60, 70, 80, 90, 100] $ \size -> do
+    liftIO $ threadDelay 1000000
+    ExceptT $ updateProgressBar mySlackConfig progressBar (
+      progressBarInfo {
+          progressBarInfoSize = Just size
+          , progressBarInfoAttachments = Just $
+              (ProgressBarAttachment [i|Hello there #{size}|] "#ff4136")
+              : (fromMaybe [] (progressBarInfoAttachments progressBarInfo))
+          })
diff --git a/slack-progressbar.cabal b/slack-progressbar.cabal
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--- /dev/null
+++ b/slack-progressbar.cabal
@@ -0,0 +1,92 @@
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.31.2.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: e02cced5857da29a9cf41726beda4002ad8659cc67ab309b5badc64895ed004a
+
+name:           slack-progressbar
+version:        0.1.0.0
+description:    Please see the README on GitHub at <https://github.com/githubuser/slack-progressbar#readme>
+homepage:       https://github.com/githubuser/slack-progressbar#readme
+bug-reports:    https://github.com/githubuser/slack-progressbar/issues
+author:         Tom McLaughlin
+maintainer:     tom@codedown.io
+copyright:      2020 CodeDown
+license:        MIT
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+    ChangeLog.md
+
+source-repository head
+  type: git
+  location: https://github.com/githubuser/slack-progressbar
+
+library
+  exposed-modules:
+      Web.Slack.ProgressBar
+  other-modules:
+      Paths_slack_progressbar
+  hs-source-dirs:
+      src
+  build-depends:
+      aeson
+    , base >=4.7 && <5
+    , bytestring
+    , interpolate
+    , lens
+    , lens-aeson
+    , mtl
+    , network-uri
+    , text
+    , transformers
+    , wreq
+  default-language: Haskell2010
+
+executable slack-progressbar-exe
+  main-is: Main.hs
+  other-modules:
+      Paths_slack_progressbar
+  hs-source-dirs:
+      app
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      aeson
+    , base >=4.7 && <5
+    , bytestring
+    , interpolate
+    , lens
+    , lens-aeson
+    , mtl
+    , network-uri
+    , slack-progressbar
+    , text
+    , transformers
+    , wreq
+  default-language: Haskell2010
+
+test-suite slack-progressbar-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Paths_slack_progressbar
+  hs-source-dirs:
+      test
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      aeson
+    , base >=4.7 && <5
+    , bytestring
+    , interpolate
+    , lens
+    , lens-aeson
+    , mtl
+    , network-uri
+    , slack-progressbar
+    , text
+    , transformers
+    , wreq
+  default-language: Haskell2010
diff --git a/src/Web/Slack/ProgressBar.hs b/src/Web/Slack/ProgressBar.hs
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--- /dev/null
+++ b/src/Web/Slack/ProgressBar.hs
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+{-# LANGUAGE ScopedTypeVariables, OverloadedStrings, QuasiQuotes, FlexibleContexts, LambdaCase, RecordWildCards #-}
+
+{-|
+Module:      Web.Slack.ProgressBar
+Copyright:   (c) 2020 Tom McLaughlin
+License:     MIT
+Stability:   experimental
+Portability: portable
+
+This is a simple library for creating and updating Slack messages that contain progressbars.
+It can be used to display the progress of a long-running task in a Slack channel, for example as part of CI tooling.
+
+@
+main :: IO ()
+main = do
+  let mySlackConfig = SlackConfig { slackApiToken = "my-slack-api-token" }
+
+  let progressBarInfo = def { progressBarInfoTopMessage = Just "Top message"
+                            , progressBarInfoSize = Just 0 }
+
+  result <- runExceptT $ do
+    progressBar <- ExceptT $ createProgressBar mySlackConfig "test-channel" progressBarInfo
+
+    forM_ [10, 20, 30, 40, 50, 60, 70, 80, 90, 100] $ \\size -> do
+      threadDelay 1000000
+      ExceptT $ updateProgressBar mySlackConfig progressBar (progressBarInfo { progressBarInfoSize = Just size })
+
+  putStrLn [i|Result: '#{result}'|]
+@
+
+-}
+
+module Web.Slack.ProgressBar (
+  createProgressBar
+  , updateProgressBar
+  , ProgressBarInfo (..)
+  , ProgressBarAttachment (..)
+  , ProgressBar
+  , ChannelName
+
+  -- * Re-exports
+  , SlackConfig (..)
+  ) where
+
+import Control.Lens hiding ((??))
+import Control.Monad.Except
+import Data.Aeson
+import qualified Data.Aeson as A
+import Data.Aeson.Lens
+import qualified Data.ByteString.Lazy as BL
+import Data.Char
+import Data.Maybe
+import Data.String.Interpolate.IsString
+import qualified Data.Text as T
+import qualified Data.Text.Encoding as T
+import qualified Network.Wreq as W
+
+
+-- | The state of a progress bar message.
+data ProgressBarInfo = ProgressBarInfo { progressBarInfoTopMessage :: Maybe T.Text
+                                       -- ^ Message to show above the progress bar
+                                       , progressBarInfoBottomMessage :: Maybe T.Text
+                                       -- ^ Message to show below the progress bar
+                                       , progressBarInfoSize :: Maybe Double
+                                       -- ^ Size of the progress bar, a 'Double' from 0 to 100
+                                       , progressBarInfoAttachments :: Maybe [ProgressBarAttachment]
+                                       -- ^ Slack attachments for the message
+                                       }
+
+-- | A Slack attachment.
+data ProgressBarAttachment = ProgressBarAttachment { progressBarAttachmentText :: T.Text
+                                                   -- ^ Attachment text
+                                                   , progressBarAttachmentColor :: T.Text
+                                                   -- ^ Attachment color
+                                                   }
+instance ToJSON ProgressBarAttachment
+  where toJSON (ProgressBarAttachment {..}) = A.object [("text", A.String progressBarAttachmentText)
+                                                       , ("color", A.String progressBarAttachmentColor)]
+
+-- | An opaque type representing an existing Slack message.
+data ProgressBar = ProgressBar { progressBarTs :: T.Text
+                               , progressBarChannel :: T.Text }
+
+type ChannelName = T.Text
+
+-- * Exported
+
+-- | Create a progress bar message on the given channel.
+-- Returns a 'ProgressBar' which can be used to update the message by calling 'updateProgressBar'.
+createProgressBar :: SlackConfig -> ChannelName -> ProgressBarInfo -> IO (Either T.Text ProgressBar)
+createProgressBar slackConfig channel pbi =
+  (runExceptT $ postMessage slackConfig channel (getMessage pbi) (getAttachments pbi)) >>= \case
+    Left err -> return $ Left [i|Failed to send initial result: '#{err}'|]
+    Right resp -> case (resp ^? key "ts" . _String, resp ^? key "channel" . _String) of
+      (Just ts, Just chan) -> return $ Right $ ProgressBar ts chan
+      _ -> return $ Left [i|Couldn't find timestamp and/or channel in response|]
+
+-- | Update an existing progress bar.
+updateProgressBar :: SlackConfig -> ProgressBar -> ProgressBarInfo -> IO (Either T.Text ())
+updateProgressBar slackConfig (ProgressBar {..}) pbi@(ProgressBarInfo {..}) =
+  (runExceptT $ updateMessage slackConfig progressBarChannel progressBarTs (getMessage pbi) (getAttachments pbi)) >>= \case
+    Left err -> return $ Left [i|Failed to update progress bar: '#{err}'|]
+    Right _ -> return $ Right ()
+
+-- * Internal
+
+getMessage :: ProgressBarInfo -> T.Text
+getMessage (ProgressBarInfo {..}) =
+  T.intercalate "\n" $ catMaybes [progressBarInfoTopMessage
+                                 , barSized <$> progressBarInfoSize
+                                 , progressBarInfoBottomMessage]
+
+getAttachments :: ProgressBarInfo -> [A.Value]
+getAttachments (ProgressBarInfo {..}) = maybe [] (fmap A.toJSON) progressBarInfoAttachments
+
+barSized :: Double -> T.Text
+barSized n = (T.replicate darkBlocks $ T.singleton $ chr 9608)
+             <> (T.replicate lightBlocks $ T.singleton $ chr 9617)
+             <> [i| #{roundTo 2 n}%|]
+  where darkBlocks = round $ n * multiplier
+        lightBlocks = round $ (100 - n) * multiplier
+        multiplier = 0.5
+
+        roundTo :: (Fractional a, RealFrac a) => Integer -> a -> a
+        roundTo places num = (fromInteger $ round $ num * (10^places)) / (10.0^^places)
+
+postMessage :: (MonadError T.Text m, MonadIO m) => SlackConfig -> ChannelName -> T.Text -> [A.Value] -> m Value
+postMessage conf cid msg as =
+  makeSlackCall conf "chat.postMessage" $
+    (W.param "channel"     .~ [cid])
+    . (W.param "text"        .~ [msg])
+    . (W.param "attachments" .~ [encode' as])
+    . (W.param "as_user"     .~ ["true"])
+
+updateMessage :: (MonadError T.Text m, MonadIO m) => SlackConfig -> ChannelName -> T.Text -> T.Text -> [A.Value] -> m ()
+updateMessage conf cid ts msg as =
+  void $ makeSlackCall conf "chat.update" $
+    (W.param "channel"     .~ [cid]) .
+    (W.param "text"        .~ [msg]) .
+    (W.param "attachments" .~ [encode' as]) .
+    (W.param "as_user"     .~ ["true"]) .
+    (W.param "ts"          .~ [ts])
+
+encode' :: ToJSON a => a -> T.Text
+encode' = T.decodeUtf8 . BL.toStrict . encode
+
+-- Inlined and modified slightly from slack-api
+-- Didn't seem worth it to add that entire library as a dependency just for these
+
+-- | Configuration options needed to connect to the Slack API
+newtype SlackConfig = SlackConfig { slackApiToken :: String
+                                  -- ^ Slack API token
+                                  } deriving (Show)
+
+makeSlackCall :: (MonadError T.Text m, MonadIO m) => SlackConfig -> String -> (W.Options -> W.Options) -> m Value
+makeSlackCall conf method setArgs = do
+  let url = "https://slack.com/api/" ++ method
+  let setToken = W.param "token" .~ [T.pack (slackApiToken conf)]
+  let opts = W.defaults & setToken & setArgs
+  rawResp <- liftIO $ W.getWith opts url
+  resp <- rawResp ^? W.responseBody . _Value ?? "Couldn't parse response"
+  case resp ^? key "ok" . _Bool of
+    Just True -> return resp
+    Just False -> throwError $ resp ^. key "error" . _String
+    Nothing -> throwError "Couldn't parse key 'ok' from response"
+
+infixl 7 ??
+(??) :: MonadError e m => Maybe a -> e -> m a
+x ?? e = maybe (throwError e) return x
diff --git a/test/Spec.hs b/test/Spec.hs
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+main :: IO ()
+main = putStrLn "Test suite not yet implemented"