mod link;

use chrono::{DateTime, Utc};
use link::Link;
use url::Url;

/// Export crawl index to the RSS file
pub struct Feed {
    buffer: String,
    canonical: Link,
}

impl Feed {
    pub fn new(
        title: &str,
        description: Option<&str>,
        canonical: Option<Url>,
        capacity: usize,
    ) -> Self {
        let t = chrono::Utc::now().to_rfc2822();
        let mut buffer = String::with_capacity(capacity);

        buffer.push_str("<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss version=\"2.0\"><channel>");

        buffer.push_str("<pubDate>");
        buffer.push_str(&t);
        buffer.push_str("</pubDate>");

        buffer.push_str("<lastBuildDate>");
        buffer.push_str(&t);
        buffer.push_str("</lastBuildDate>");

        buffer.push_str("<title>");
        buffer.push_str(title);
        buffer.push_str("</title>");

        if let Some(d) = description {
            buffer.push_str("<description>");
            buffer.push_str(d);
            buffer.push_str("</description>")
        }

        if let Some(ref c) = canonical {
            // @TODO required the RSS specification!
            buffer.push_str("<link>");
            buffer.push_str(c.as_str());
            buffer.push_str("</link>")
        }

        Self {
            buffer,
            canonical: Link::from_url(canonical),
        }
    }

    /// Append `item` to the feed `channel`
    pub fn push(&mut self, guid: i64, time: DateTime<Utc>, title: String, message: &str) {
        self.buffer.push_str(&format!(
            "<item><guid>{guid}</guid><title>{title}</title><link>{}</link>",
            self.canonical.link(guid)
        ));

        self.buffer.push_str("<description>");
        self.buffer.push_str(&escape(message));
        self.buffer.push_str("</description>");

        self.buffer.push_str("<pubDate>");
        self.buffer.push_str(&time.to_rfc2822());
        self.buffer.push_str("</pubDate>");

        self.buffer.push_str("</item>")
    }

    /// Write final bytes
    pub fn commit(mut self) -> String {
        self.buffer.push_str("</channel></rss>");
        self.buffer
    }
}

fn escape(value: &str) -> String {
    value
        .replace('&', "&amp;")
        .replace('<', "&lt;")
        .replace('>', "&gt;")
        .replace('"', "&quot;")
        .replace("'", "&apos;")
}