use {
  super::{
    config::{BlogCategory, BlogPost},
    post::Post,
  },
  crate::{
    notion,
    response::success,
    route::track_mount,
    url::ROOT_GEMINI_URL,
    xml::{Item as XmlItem, Writer as XmlWriter},
  },
  std::sync::{LazyLock, Mutex, RwLock},
};

pub static POSTS: LazyLock<Mutex<Vec<Post>>> =
  LazyLock::new(|| Mutex::new(Vec::new()));
static BLOG_CATEGORIES: LazyLock<RwLock<Vec<BlogCategory>>> =
  LazyLock::new(|| RwLock::new(Vec::new()));
static BLOG_POSTS: LazyLock<RwLock<Vec<BlogPost>>> =
  LazyLock::new(|| RwLock::new(Vec::new()));

#[allow(clippy::too_many_lines)]
pub fn module(router: &mut windmark::router::Router) {
  std::thread::spawn(fetch_from_notion)
    .join()
    .expect("initial Notion fetch failed");
  track_mount(router, "/blog", "Fuwn's blogs", |context| {
    let categories = BLOG_CATEGORIES.read().unwrap();
    let listing = categories
      .iter()
      .map(|category| {
        let slug = slugify(&category.title);

        format!(
          "=> /blog/{} {}{}",
          slug,
          category.title,
          category
            .description
            .as_ref()
            .map_or_else(String::new, |description_text| format!(
              " ― {description_text}"
            ))
        )
      })
      .collect::<Vec<_>>()
      .join("\n");

    success(&format!("# Blogs ({})\n\n{}", categories.len(), listing), &context)
  });
  track_mount(
    router,
    "/blog/:blog_name",
    "-A blog on Fuwn's capsule",
    |context| {
      let raw_blog_name =
        context.parameters.get("blog_name").cloned().unwrap_or_default();

      if let Some(blog_slug) = raw_blog_name.strip_suffix(".xml") {
        return build_rss_feed(blog_slug);
      }

      let blog_slug = raw_blog_name;
      let categories = BLOG_CATEGORIES.read().unwrap();
      let posts = BLOG_POSTS.read().unwrap();
      let matched_category = categories
        .iter()
        .find(|category| slugify(&category.title) == blog_slug);
      let Some(category) = matched_category else {
        return windmark::response::Response::not_found(
          "This blog could not be found.",
        );
      };
      let category_posts: Vec<_> = posts
        .iter()
        .filter(|post| post.blog_id == category.notion_id)
        .collect();
      let post_listing = category_posts
        .iter()
        .map(|post| {
          let post_slug = slugify(&post.title);

          format!(
            "=> /blog/{}/{} {}{}",
            blog_slug,
            post_slug,
            post.title,
            post
              .description
              .as_ref()
              .filter(|description_text| !description_text.is_empty())
              .map_or_else(String::new, |description_text| format!(
                " ― {description_text}"
              ))
          )
        })
        .collect::<Vec<_>>()
        .join("\n");

      success(
        &format!(
          "# {} ({})\n\n{}\n\n{}\n\n## Really Simple Syndication\n\nAccess \
           {0}'s RSS feed\n\n=> /blog/{}.xml here!",
          category.title,
          category_posts.len(),
          category.description.as_deref().unwrap_or(""),
          post_listing,
          blog_slug,
        ),
        &context,
      )
    },
  );
  track_mount(
    router,
    "/blog/:blog_name/:post_title",
    "-An entry to one of Fuwn's blogs",
    |context| {
      let blog_slug =
        context.parameters.get("blog_name").cloned().unwrap_or_default();
      let post_slug =
        context.parameters.get("post_title").cloned().unwrap_or_default();
      let categories = BLOG_CATEGORIES.read().unwrap();
      let posts = BLOG_POSTS.read().unwrap();
      let matched_category = categories
        .iter()
        .find(|category| slugify(&category.title) == blog_slug);
      let Some(category) = matched_category else {
        return windmark::response::Response::not_found(
          "This blog could not be found.",
        );
      };
      let matched_post = posts.iter().find(|post| {
        post.blog_id == category.notion_id && slugify(&post.title) == post_slug
      });
      let Some(post) = matched_post else {
        return windmark::response::Response::not_found(
          "This post could not be found.",
        );
      };
      let header = construct_header(post);

      success(&format!("{}\n{}", header, post.content), &context)
    },
  );
}

fn construct_header(post: &BlogPost) -> String {
  let title_line = format!("# {}", post.title);
  let has_metadata = post.author.is_some()
    || post.created.is_some()
    || post.last_modified.is_some()
    || post.description.is_some();

  if !has_metadata {
    return title_line;
  }

  let author_fragment =
    post.author.as_ref().map_or_else(String::new, |author_name| {
      format!("Written by {author_name}")
    });
  let created_fragment = post
    .created
    .as_ref()
    .map_or_else(String::new, |created_date| format!(" on {created_date}"));
  let modified_fragment =
    post.last_modified.as_ref().map_or_else(String::new, |modified_date| {
      format!(" (last modified on {modified_date})\n")
    });
  let description_fragment = post
    .description
    .as_ref()
    .filter(|description_text| !description_text.is_empty())
    .map_or_else(String::new, |description_text| {
      format!("\n{description_text}\n")
    });

  format!(
    "{title_line}\n\n{author_fragment}{created_fragment}{modified_fragment}{description_fragment}"
  )
}

fn slugify(text: &str) -> String { text.replace(' ', "_").to_lowercase() }

fn build_rss_feed(blog_slug: &str) -> windmark::response::Response {
  let categories = BLOG_CATEGORIES.read().unwrap();
  let posts = BLOG_POSTS.read().unwrap();
  let matched_category =
    categories.iter().find(|category| slugify(&category.title) == blog_slug);
  let Some(category) = matched_category else {
    return windmark::response::Response::not_found(
      "This blog could not be found.",
    );
  };
  let mut xml = XmlWriter::builder();

  xml.add_field("title", &category.title);
  xml.add_field("link", &format!("{ROOT_GEMINI_URL}/blog/{blog_slug}"));

  if let Some(ref description_text) = category.description {
    xml.add_field("description", description_text);
  }

  xml.add_field("generator", "locus");
  xml.add_field("lastBuildDate", &chrono::Local::now().to_rfc2822());
  xml.add_link(&format!("{ROOT_GEMINI_URL}/blog/{blog_slug}.xml"));

  for post in posts.iter().filter(|post| post.blog_id == category.notion_id) {
    let post_slug = slugify(&post.title);

    xml.add_item(&{
      let mut builder = XmlItem::builder();

      builder.add_field(
        "link",
        &format!("{ROOT_GEMINI_URL}/blog/{blog_slug}/{post_slug}"),
      );
      builder.add_field("description", &post.content);
      builder.add_field(
        "guid",
        &format!("{ROOT_GEMINI_URL}/blog/{blog_slug}/{post_slug}"),
      );
      builder.add_field("title", &post.title);

      if let Some(ref created_date) = post.created {
        builder.add_field("pubDate", created_date);
      }

      builder
    });
  }

  windmark::response::Response::success(xml.to_string())
    .with_mime("text/rss+xml")
    .clone()
}

fn fetch_from_notion() {
  let api_key = std::env::var("NOTION_API_KEY")
    .expect("NOTION_API_KEY environment variable is required");
  let blogs_database_identifier = std::env::var("NOTION_BLOGS_DATABASE_ID")
    .expect("NOTION_BLOGS_DATABASE_ID environment variable is required");
  let posts_database_identifier = std::env::var("NOTION_POSTS_DATABASE_ID")
    .expect("NOTION_POSTS_DATABASE_ID environment variable is required");
  let http_client = reqwest::blocking::Client::new();
  let blog_pages =
    notion::query_database(&http_client, &api_key, &blogs_database_identifier)
      .expect("failed to query Notion blogs database");
  let mut categories: Vec<BlogCategory> = blog_pages
    .iter()
    .map(|page| {
      let description_text =
        notion::extract_rich_text(&page.properties, "Description");

      BlogCategory {
        title:       notion::extract_title(&page.properties, "Title"),
        description: if description_text.is_empty() {
          None
        } else {
          Some(description_text)
        },
        priority:    notion::extract_number(&page.properties, "Priority")
          .unwrap_or(0),
        notion_id:   page.id.clone(),
      }
    })
    .collect();

  categories.sort_by(|first, second| second.priority.cmp(&first.priority));

  let post_pages =
    notion::query_database(&http_client, &api_key, &posts_database_identifier)
      .expect("failed to query Notion posts database");
  let fetched_posts: Vec<BlogPost> = post_pages
    .iter()
    .map(|page| {
      let page_content =
        notion::fetch_page_content(&http_client, &api_key, &page.id)
          .unwrap_or_default();
      let blog_relation_ids =
        notion::extract_relation_ids(&page.properties, "Blog");
      let blog_identifier =
        blog_relation_ids.first().cloned().unwrap_or_default();
      let created_raw = notion::extract_date(&page.properties, "Created");
      let last_modified_raw =
        notion::extract_date(&page.properties, "Last Modified");
      let description_text =
        notion::extract_rich_text(&page.properties, "Description");
      let author_text = notion::extract_rich_text(&page.properties, "Author");

      BlogPost {
        title:         notion::extract_title(&page.properties, "Title"),
        description:   if description_text.is_empty() {
          None
        } else {
          Some(description_text)
        },
        author:        if author_text.is_empty() {
          None
        } else {
          Some(author_text)
        },
        created:       if created_raw.is_empty() {
          None
        } else {
          Some(notion::format_notion_date(&created_raw))
        },
        last_modified: if last_modified_raw.is_empty() {
          None
        } else {
          Some(notion::format_notion_date(&last_modified_raw))
        },
        content:       page_content,
        blog_id:       blog_identifier,
      }
    })
    .collect();

  {
    let mut global_posts = POSTS.lock().unwrap();

    global_posts.clear();

    for post in &fetched_posts {
      let blog_title = categories
        .iter()
        .find(|category| category.notion_id == post.blog_id)
        .map(|category| category.title.clone())
        .unwrap_or_default();

      global_posts.push(Post::new(
        format!("{}, {}", blog_title, post.title),
        format!("/blog/{}/{}", slugify(&blog_title), slugify(&post.title)),
        post.created.clone().unwrap_or_default(),
      ));
    }
  }

  *BLOG_CATEGORIES.write().unwrap() = categories;
  *BLOG_POSTS.write().unwrap() = fetched_posts;

  info!("fetched blog data from Notion");
}

pub fn refresh_loop() {
  let refresh_interval_seconds = std::env::var("NOTION_REFRESH_INTERVAL")
    .ok()
    .and_then(|value| value.parse::<u64>().ok())
    .unwrap_or(300);

  info!("spawned Notion blog refresh loop ({refresh_interval_seconds}s interval)");

  loop {
    std::thread::sleep(std::time::Duration::from_secs(refresh_interval_seconds));

    match std::panic::catch_unwind(fetch_from_notion) {
      Ok(()) => info!("refreshed blog data from Notion"),
      Err(_) => warn!("failed to refresh blog data from Notion"),
    }
  }
}