-- pulling heavily from https://abhinavsarkar.net/posts/static-site-generator-using-shake/
-- docs:
-- https://hackage.haskell.org/package/shake-0.19.8/docs/doc-index-All.html
-- https://hackage.haskell.org/package/pandoc-3.2.1/docs/doc-index-All.html
-- https://hackage.haskell.org/package/mustache-2.4.2/docs/doc-index.html
--

module Main where

import Config
import Control.Monad (forM, when)
import qualified Data.HashMap.Strict as HM
import Data.List (sortOn)
import qualified Data.Ord as Ord
import qualified Data.Text as T
import Data.Time
import Development.Shake (Action, Rules, (%>), (|%>), (~>))
import qualified Development.Shake as Shake
import Development.Shake.FilePath ((</>))
import qualified Development.Shake.FilePath as FP
import Templates
import Types
import Utilities

-- target = thing we want
-- Rule = pattern of thing being made + actions to produce the thing
-- Action = actions to produce a thing

main :: IO ()
main = do
  Shake.shakeArgs Shake.shakeOptions $ do
    Shake.withTargetDocs "Build the site" $
      "build" ~> buildSite
    Shake.withTargetDocs "Clean the built site" $
      "clean" ~> Shake.removeFilesAfter outputDir ["//*"]
    Shake.withoutTargets buildRules

buildSite :: Action ()
buildSite = do
  -- static files
  assetPaths <- Shake.getDirectoryFiles "" assetGlobs
  --  path concat each asset path so it's output into the outputDir
  Shake.need $ map (outputDir </>) assetPaths

  -- take the misc pages which aren't blog posts and make their html files
  Shake.need $ map indexHtmlOutputPath pagePaths

  -- handle posts
  postPaths <- Shake.getDirectoryFiles "" postGlobs
  Shake.need $ map indexHtmlOutputPath postPaths

  -- posts list
  Shake.need [indexHtmlOutputPath "posts"]

  -- remaining pages, index.xml = rss feed
  Shake.need $ map (outputDir </>) ["index.html", "index.xml"]

buildRules :: Rules ()
buildRules = do
  home
  assets
  pages
  postsRule
  postList
  rss

-- make a rule of the pattern outputDir/asset_name which copes from outputDir/../pages
assets :: Rules ()
assets =
  map (outputDir </>) assetGlobs |%> \target -> do
    let src = FP.dropDirectory1 target
    Shake.copyFileChanged src target
    Shake.putInfo $ "Copied " <> target <> " from " <> src

-- handling typst only because pages should only be typst no reason for backwards compat on that
pages :: Rules ()
pages =
  map indexHtmlOutputPath pagePaths |%> \target -> do
    let src = indexHtmlTypstSourcePath target
    let metaSrc = indexHtmlTypstMetaPath target
    html <- typstToHtml src
    meta <- yamlToPost metaSrc
    let page = Page (postTitle meta) html
    applyTemplateAndWrite "default.html" page target
    Shake.putInfo $ "Built " <> target <> " from " <> src

-- there's probably a better way of doing this that allows for the target's origin file extension to get passed in but for now we're doing brute force
postsRule :: Rules ()
postsRule =
  map indexHtmlOutputPath postGlobs |%> \target -> do
    let potentials = indexHtmlSourcePaths target
    Shake.forP
      potentials
      ( \path -> do
          exists <- Shake.doesFileExist path
          when
            exists
            ( case FP.takeExtension path of
                ".typ" -> typstPost path
                ".md" -> markdownPost path
                _ -> error $ "invalid file extension for post " <> target
            )
      )
    return ()

typstPost :: FP.FilePath -> Action ()
typstPost src = do
  Shake.need [src]
  let target = indexHtmlOutputPath src

  post <- readTypstPost src
  let rPost = fromPost post
  postHtml <- applyTemplate "post.html" rPost

  let page = Page (postTitle post) postHtml
  applyTemplateAndWrite "default.html" page target
  Shake.putInfo $ "Built " <> target <> " from " <> src

markdownPost :: FP.FilePath -> Action ()
markdownPost src = do
  Shake.need [src]
  let target = indexHtmlOutputPath src

  post <- readMarkdownPost src
  let rPost = fromPost post
  -- Shake.putInfo $ show . toJSON $ rPost
  postHtml <- applyTemplate "post.html" rPost

  let page = Page (postTitle post) postHtml
  applyTemplateAndWrite "default.html" page target
  Shake.putInfo $ "Built " <> target <> " from " <> src

home :: Rules ()
home =
  outputDir </> "index.html" %> \target -> do
    postPaths <- Shake.getDirectoryFiles "" postGlobs
    posts <-
      take 3
        . sortOn (Ord.Down . postDate)
        <$> forM postPaths readPost
    html <- applyTemplate "home.html" $ HM.singleton "posts" posts

    let page = Page (T.pack "Home") html
    applyTemplateAndWrite "default.html" page target
    Shake.putInfo $ "Built " <> target

postList :: Rules ()
postList =
  outputDir </> "posts/index.html" %> \target -> do
    postPaths <- Shake.getDirectoryFiles "" postGlobs
    posts <- sortOn (Ord.Down . postDate) <$> forM postPaths readPost
    html <- applyTemplate "posts.html" $ HM.singleton "posts" posts
    let page = Page (T.pack "Blog Posts") html
    applyTemplateAndWrite "default.html" page target
    Shake.putInfo $ "Built " <> target

rss :: Rules ()
rss =
  outputDir </> "index.xml" %> \target -> do
    postPaths <- Shake.getDirectoryFiles "" postGlobs
    posts <- sortOn (Ord.Down . postDate) <$> forM postPaths readPost
    applyTemplateAndWrite "feed.xml" (HM.singleton "posts" posts) target

    Shake.putInfo $ "Built " <> target

readPost :: FilePath -> Action Post
readPost postPath = do
  case FP.takeExtension postPath of
    ".typ" -> readTypstPost postPath
    ".md" -> readMarkdownPost postPath
    _ -> error $ "unknown file extension for file" <> postPath

readTypstPost :: FilePath -> Action Post
readTypstPost postPath = do
  html <- typstToHtml postPath
  post <- yamlToPost $ typstMetaPath postPath
  Shake.putInfo $ "Read " <> postPath
  return $
    post
      { postContent = Just html,
        postLink = Just . T.pack $ "/" <> FP.dropExtension postPath <> "/"
      }

readMarkdownPost :: FilePath -> Action Post
readMarkdownPost postPath = do
  (post, html) <- markdownToHtml postPath
  Shake.putInfo $ "Read " <> postPath
  return $
    post
      { postContent = Just html,
        postLink = Just . T.pack $ "/" <> FP.dropExtension postPath <> "/"
      }