add these old posts from greedo (#31)

* add these old posts from greedo

* Update textile-to-markdown-literate-haskell-2017-02-08.markdown

2 files changed, 243 insertions, 0 deletions

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+---
+title: textile-conversion Main
+date: 2017-02-08
+---
+
+# textile-conversion Main
+
+Author's Note: this was intended to be documentation for a service that never ended
+up being implemented. It was going to help [Derpibooru](https://derpibooru.org)
+convert its existing markup to [Markdown](https://github.github.com/gfm/). This
+never happened.
+
+This program listens on port 5000 and serves an unchecked-path web handler that
+converts Derpibooru Textile via HTML into Markdown, using a two-step process.
+
+The first step is to have SimpleTextile emit a HTML AST of the comment.
+The second is to have Pandoc turn that HTML into Markdown.
+
+This is intended to be helpful during Derpi's migration from Textile.
+
+## Pragmas
+
+The following pragma tells the compiler to automagically tease string literals
+into whatever type they need to be. For more information on this, see [this page][hs-ovs].
+
+```haskell
+{-# LANGUAGE OverloadedStrings #-}
+module Main where
+```
+
+## Imports
+
+In order to accomplish our task, we need to import some libraries.
+
+```haskell
+import Data.String.Conv (toS)
+import Network.Wai
+import Network.HTTP.Simple
+import Network.HTTP.Types
+import Network.Wai.Handler.Warp (run)
+import System.Environment (lookupEnv)
+import Text.Pandoc
+import Text.Pandoc.Error (PandocError, handleError)
+```
+
+## Helper Functions
+
+getEnvDefault queries an environment variable, returning a default value if it
+is unset.
+
+```haskell
+getEnvDefault :: String -> String -> IO String
+getEnvDefault name default' = do
+    envvar <- lookupEnv name
+    case envvar of
+      Nothing -> pure default'
+      Just x  -> pure x
+```
+
+---
+
+htmlToMarkdown uses Pandoc to convert a HTML input string into the equivalent
+Markdown. The `Either` type is used here in place of raising an exception.
+
+```haskell
+htmlToMarkdown :: String -> Either PandocError String
+htmlToMarkdown inp = do
+    let
+        corpus = readHtml def inp
+
+    case corpus of
+        Left x ->  Left x
+        Right x -> pure $ writeMarkdown def x
+```
+
+## Web Application
+
+Now we are getting into the meat of the situation. This is the main
+[Application][wai-application].
+
+```haskell
+toMarkdown :: Application
+```
+
+First, let's use a [guard][guards] to ensure that we are only accepting `POST`
+requests. If the request is not a `POST` request, return [HTTP error code 405][http-4xx].
+
+```haskell
+toMarkdown req respond
+    | requestMethod req /= methodPost =
+        respond $ responseLBS
+            status405
+            [("Content-Type", "text/plain")]
+            "Not allowed"
+```
+
+Otherwise, this is a `POST` request, so we should:
+
+1. Unpack the data from the post body of the HTTP request
+2. Send the data to the Sinatra app for conversion from Textile to HTML
+3. Take the resulting HTML and feed it to `htmlToMarkdown`
+4. Respond with the resulting Markdown.
+
+We use [http-conduit][http-conduit] to contact the Sinatra app.
+
+```haskell
+    | otherwise = do
+        body <- requestBody req
+        targetHost <- getEnvDefault "TARGET_SERVER" "http://127.0.0.1:9292"
+        remoteRequest' <- parseRequest ("POST " ++ targetHost ++ "/textile/html")
+```
+
+The `($)` operator is a synonym for calling functions. It is defined in the [Prelude][dolla]
+as `f $ x = f x` and is mainly used for omitting parentheses. Here it is used
+to combine HTTP request settings into one big request.
+
+Additionally we use a custom [Manager][manager] to avoid any issues with
+request timeouts, as those are not important for the scope of this tool.
+
+```haskell
+        let settings = defaultManagerSettings { managerResponseTimeout = Nothing }
+        manager <- newManager settings
+
+        let remoteRequest = setRequestBodyLBS (toS body)
+                          $ setRequestManager manager
+                          $ remoteRequest'
+```
+
+Now it is time to send off the request and unpack the response.
+
+```haskell
+        response <- httpLBS remoteRequest
+```
+
+If the sinatra app failed to deal with this properly for some reason, report
+its error as `text/plain` and return `400`.
+
+```haskell
+        if getResponseStatusCode response /= 200
+        then respond $ responseLBS
+            status400
+            [("Content-Type", "text/plain")]
+            $ toS $ getResponseBody response
+        else do
+            let rbody = toS $ getResponseBody response
+```
+
+Convert the result body into Markdown. If there is an error, respond with a `400`
+and the contents of that error.
+
+```haskell
+            let mbody = htmlToMarkdown rbody
+
+            case mbody of
+                Left x ->
+                    respond $ responseLBS
+                        status400
+                        [("Content-Type", "text/plain")]
+                        $ toS $ show x
+                Right x -> do
+                    respond $ responseLBS
+                        status200
+                        [("Content-Type", "text/markdown")]
+                        $ toS x
+```
+
+Now we bootstrap it all by running the `toMarkdown` Application on port `5000`.
+No other code is needed.
+
+```haskell
+main :: IO ()
+main =
+    run 5000 toMarkdown
+```
+
+[hs-ovs]: https://ocharles.org.uk/blog/posts/2014-12-17-overloaded-strings.html
+[wai-application]: https://hackage.haskell.org/package/wai
+[guards]: https://en.wikibooks.org/wiki/Haskell/Control_structures
+[http-4xx]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#4xx_Client_Error
+[http-conduit]: https://www.stackage.org/haddock/lts-6.6/http-conduit-2.1.11/Network-HTTP-Simple.html
+[dolla]: https://hackage.haskell.org/package/base-4.9.0.0/docs/Prelude.html#v:-36-
+[manger]: https://www.stackage.org/haddock/lts-6.5/http-client-0.4.29/Network-HTTP-Client.html#g:3
diff --git a/blog/webirc-protocol-2017-04-12.markdown b/blog/webirc-protocol-2017-04-12.markdown
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+---
+title: "IRCv3.2 `webirc` Extension"
+date: 2017-04-12
+---
+
+# IRCv3.1 `webirc` Extension
+
+This document does not describe a new IRCv3 standard. It is designed to 
+document how the existing `WEBIRC` mechanism works so there is a specification 
+to test things against. This is known to be implemented by all major IRC 
+daemons as of the time of this writing.
+
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+"SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this document are to be
+interpreted as described in RFC 2119.
+
+Summary
+-------
+
+The `WEBIRC` verb allows a connecting IRC client to spoof its origin IP address 
+so that a user connecting via a gateway of some kind may have accountability 
+for their actions and bans against them do not affect unintended users of said 
+gateway.
+
+This protocol verb must be sent before the initial `NICK` and `USER` handshake 
+and may be advertised as the client capability `webirc`. The remote server may 
+send a pre-connection `NOTICE` clarifying that the user has their specified IP 
+address and reverse DNS. Gateway implementors must not let the user set their 
+own IP address as part of connection negotiations.
+
+Formatting
+----------
+
+The `WEBIRC` verb must be used as such:
+
+    WEBIRC <password> <client ident> <client reverse DNS> <client IP address>
+
+Access to `WEBIRC` must be protected by a password to prevent abuse. If the 
+password the client gives fails, the IRC daemon should disconnect the client 
+with an appropriate error message. IRC daemon authors should also restruct the
+use of the `WEBIRC` verb to a specific IP address and may force the use of
+a specific identd reply.
+
+Example Session
+---------------
+
+    >> WEBIRC snowflower Mibbit anonyhash.mibbit.com 127.0.0.1
+    >> NICK mib_4002
+    >> USER Mibbit x x :http://mibbit.com AJAX IRC Client
+    << :hostname.domain.tld 001 mib_4002 :Welcome to ShadowNET mib_4002!
+
+Limitations
+-----------
+
+In order for this to be secure, the relay server must be trusted by the IRC
+server. A remote server may kill off clients that fail the password and host
+check, but this is not required.
+
+---
+
+This was recovered from an old backup of my site data on 2019-04-12.