use reqwest::Url;
use chrono::{DateTime, Utc};
use crate::{
  Result,
  AdapterPool,
  db::{
    ChannelId,
    Item,
    FeedChannel,
    feed_channel::UnparsedFeedChannel,
    item::UnparsedItem,
  },
  fetch::FetchedRSSChannel,
};

pub struct UnparsedChannel {
  pub id: i64,
  pub title: String,
  pub link: String,
  pub description: Option<String>,
  pub last_fetched: Option<String>,
}
impl UnparsedChannel {
  pub fn parse(self) -> Result<Channel> {
    Ok(Channel {
      id: ChannelId(self.id),
      title: self.title,
      link: Url::parse(&self.link)?,
      description: self.description,
      last_fetched: self.last_fetched.as_deref()
        .map(DateTime::parse_from_rfc2822)
        .transpose()?
        .map(|dt| dt.with_timezone(&Utc)),
    })
  }
}

pub struct Channel {
  id: ChannelId,
  title: String,
  link: Url,
  description: Option<String>,
  last_fetched: Option<DateTime<Utc>>,
}

impl Channel {
  pub fn id(&self) -> ChannelId { self.id }
  pub fn title(&self) -> &str { &self.title }
  pub fn link(&self) -> &Url { &self.link }
  pub fn description(&self) -> Option<&str> { self.description.as_deref() }
  pub fn last_fetched(&self) -> Option<DateTime<Utc>> { self.last_fetched }

  pub async fn get_all(pool: &AdapterPool) -> Result<Vec<Self>> {
    let channels: Result<Vec<Channel>> = sqlx::query_as!(
      UnparsedChannel,
      "SELECT id, title, link, description, last_fetched FROM channels"
    ).fetch_all(&pool.0).await?.into_iter().map(UnparsedChannel::parse).collect();

    channels
  }

  pub async fn get(pool: &AdapterPool, id: ChannelId) -> Result<Self> {
    let channel: Result<Self> = sqlx::query_as!(
      UnparsedChannel,
      "SELECT id, title, link, description, last_fetched
       FROM channels
       WHERE id = ?",
      id.0
    ).fetch_one(&pool.0).await?.parse();

    channel
  }

  pub async fn get_or_create(
    pool: &AdapterPool, link: Url
  ) -> Result<Self> {
    let link_str = link.as_str();

    let channel = sqlx::query_as!(
      UnparsedChannel,
      "INSERT INTO channels (title, link)
       VALUES(?, ?)
       ON CONFLICT(link) DO UPDATE SET link = link
       RETURNING id, title, link, description, last_fetched",
      link_str, link_str // We use the url as a placeholder title
    ).fetch_one(&pool.0).await?.parse();

    channel
  }

  // TODO implement fetch skipping
  pub fn should_skip_fetch(&self) -> bool { false }

  pub async fn update_metadata(
    &self, pool: &AdapterPool, fetched: FetchedRSSChannel
  ) -> Result<()> {
    let title = fetched.title();
    let description = fetched.description();
    let link = fetched.link().as_str();
    let fetched_at = fetched.fetched_at().to_rfc2822();
    sqlx::query!(
      "UPDATE channels
       SET title = ?, link = ?, description = ?, 
        last_fetched = ?
       WHERE id = ?",
      title, link, description, fetched_at,
      self.id.0
    ).execute(&pool.0).await?;

    Ok(())
  }

  async fn get_feed_channels(
    &self, pool: &AdapterPool
  ) -> Result<Vec<FeedChannel>> {
    let feeds: Result<Vec<FeedChannel>> = sqlx::query_as!(
      UnparsedFeedChannel,
      "SELECT channel_id, feed_id
       FROM feed_channels
       WHERE channel_id = ?",
      self.id.0
    ).fetch_all(&pool.0).await?.into_iter()
      .map(UnparsedFeedChannel::parse).collect();

    feeds
  }

  pub async fn update_items(
    &self, pool: &AdapterPool, fetched: FetchedRSSChannel
  ) -> Result<()> {
    let fetched_at = fetched.fetched_at();

    let feed_channels = self.get_feed_channels(pool).await?;

    for rss_item in fetched.items() {
      let new_item = Item::get_or_create(pool, self.id, rss_item.guid()).await?;
      new_item.update_content(pool, rss_item, &fetched_at).await?;
      for feed_channel in &feed_channels {
        feed_channel.add_item(pool, &new_item).await?;
      }
    }

    Ok(())
  }

  pub async fn get_items(&self, pool: &AdapterPool) -> Result<Vec<Item>> {
    let items: Result<Vec<Item>> = sqlx::query_as!(
      UnparsedItem,
      "SELECT id as `id!`, channel_id, fetched_at, title, description,
         content
       FROM items
       WHERE channel_id = ?",
      self.id.0
    ).fetch_all(&pool.0).await?.into_iter().map(UnparsedItem::parse).collect();

    items
  }
}

#[cfg(test)]
mod tests {
  use super::*;
  use crate::{Adapter, AdapterBuilder};

  const FEED1: &str = "https://example.com/feed";
  const FEED2: &str = "https://example2.com/feed";

  async fn setup_adapter() -> Adapter {
    AdapterBuilder::new()
      .database_url("sqlite::memory:")
      .create().await.unwrap()
  }

  #[tokio::test]
  async fn create_channel() {
    let adapter = setup_adapter().await;
		let pool = adapter.get_pool();
    let url_feed = Url::parse(FEED1).unwrap();

    let channel = Channel::get_or_create(pool, url_feed).await.unwrap();

    assert!(channel.id().0 > 0);
    assert_eq!(channel.link().as_str(), FEED1);
    assert!(channel.title().len() > 0);
  }

  #[tokio::test]
  async fn create_duplicate_returns_existing() {
    let adapter = setup_adapter().await;
		let pool = adapter.get_pool();
    let url_feed = Url::parse(FEED1).unwrap();

    let channel1 = Channel::get_or_create(pool, url_feed.clone()).await.unwrap();
    let channel2 = Channel::get_or_create(pool, url_feed).await.unwrap();

    assert_eq!(
      i64::from(channel1.id()),
      i64::from(channel2.id())
    );
  }

  #[tokio::test]
  async fn get_all_channels() {
    let adapter = setup_adapter().await;
		let pool = adapter.get_pool();
    let url_feed1 = Url::parse(FEED1).unwrap();
    let url_feed2 = Url::parse(FEED2).unwrap();

    Channel::get_or_create(pool, url_feed1).await.unwrap();
    Channel::get_or_create(pool, url_feed2).await.unwrap();

    let channels = Channel::get_all(pool).await.unwrap();

    assert_eq!(channels.len(), 2);
  }
}