use crate::feed_store::FeedStore;
use crate::to_checked_pathbuf;
use crate::Config;
use anyhow::Result;
use camino::Utf8Path;
use feed_rs::model::Feed;
use std::collections::{BTreeMap, HashMap};
use std::fs::{copy, create_dir_all, File};
use tera::{from_value, Tera};
use url::Url;

pub fn build(config: &Config, feed_store: &mut FeedStore) -> Result<()> {
    let mut tera = if let Some(theme) = &config.theme {
        create_tera(&config.templates_dir.join(theme))?
    } else {
        create_tera(&config.templates_dir)?
    };
    let out_dir = to_checked_pathbuf(&config.out_dir);

    let mut context = tera::Context::new();
    let (feeds, entries): (HashMap<String, Feed>, _) = feed_store.collect(config.max_entries);
    context.insert("config", config);
    context.insert("feeds", &feeds);
    context.insert("entries", &entries);
    context.insert("lang", &config.lang);
    context.insert("PKG_AUTHORS", env!("CARGO_PKG_AUTHORS"));
    context.insert("PKG_HOMEPAGE", env!("CARGO_PKG_HOMEPAGE"));
    context.insert("PKG_NAME", env!("CARGO_PKG_NAME"));
    context.insert("PKG_VERSION", env!("CARGO_PKG_VERSION"));
    tera.register_function("get_author", GetAuthorFunction { feeds });
    tera.register_function("get_feed_config", GetFeedConfigFunction {
        feeds: config.feeds.iter().map(|feed| (feed.url.clone(), feed.clone())).collect()
    });

    for name in tera.get_template_names() {
        debug!("Processing template {name}");
        let file = File::create(format!("{out_dir}/{name}"))?;
        tera.render_to(name, &context, file)?;
    }

    // Copy static assets from theme, if any
    if let Some(theme) = &config.theme {
        let assets_dir = config.templates_dir.join(theme).join("assets");
        if assets_dir.is_dir() {
            copy_assets(&assets_dir, &out_dir)?;
        }
    }

    Ok(())
}

/// Recursively copy assets from one dir to another
///
/// Symlinks are ignored.
fn copy_assets(orig: &Utf8Path, dest: &Utf8Path) -> Result<()> {
    if orig.is_dir() {
        if !dest.is_dir() {
            create_dir_all(dest)?;
        }

        for entry in orig.read_dir_utf8()? {
            let entry = entry?;
            copy_assets(entry.path(), &dest.join(entry.file_name()))?;
        }
    } else if orig.is_file() {
        copy(orig, dest)?;
    }

    Ok(())
}

fn create_tera(templates_dir: &Utf8Path) -> Result<Tera> {
    let dir = to_checked_pathbuf(templates_dir);
    let mut tera = tera::Tera::new(&format!("{dir}/*"))?;
    // disable autoescape as this would corrupt urls or the entriy contents. todo check this!
    tera.autoescape_on(vec![]);
    Ok(tera)
}

struct GetFeedConfigFunction {
    feeds: BTreeMap<Url, super::FeedConfig>,
}

impl tera::Function for GetFeedConfigFunction {
    fn call(&self, args: &HashMap<String, tera::Value>) -> Result<tera::Value, tera::Error> {
        let feed: Url = match args.get("feed") {
            None => {
                return Err(tera::Error::msg(
                    "No argument of name 'feed' given to function.",
                ))
            }
            Some(val) => from_value(val.clone())?,
        };

        if let Some(feed_config) = self.feeds.get(&feed) {
            Ok(tera::to_value(feed_config)?)
        } else {
            Err(tera::Error::msg(
                format!("Invalid feed URL: {}", feed),
            ))
        }
    }
}

struct GetAuthorFunction {
    feeds: HashMap<String, Feed>,
}

impl tera::Function for GetAuthorFunction {
    fn call(&self, args: &HashMap<String, tera::Value>) -> Result<tera::Value, tera::Error> {
        let entry_val: tera::Map<_, _> = match args.get("entry") {
            None => {
                return Err(tera::Error::msg(
                    "No argument of name 'entry' given to function.",
                ))
            }
            Some(val) => from_value(val.clone())?,
        };

        let feed_url: String = from_value(entry_val.get("source").unwrap().clone())?;
        let authors_val: Vec<tera::Map<_, _>> =
            from_value(entry_val.get("authors").unwrap().clone())?;

        let mut authors: Vec<String> = Vec::new();
        for author_val in authors_val {
            let name: String = from_value(author_val.get("name").unwrap().clone())?;
            if is_valid_name(&name) {
                authors.push(name.clone());
            }
        }

        if authors.is_empty() {
            authors.append(&mut self.find_authors_from_feed(&feed_url));
        }
        Ok(tera::Value::String(authors.join(", ")))
    }
}

impl GetAuthorFunction {
    fn find_authors_from_feed(&self, feed_url: &str) -> Vec<String> {
        let feed = self.feeds.get(feed_url).unwrap();

        feed.authors
            .clone()
            .into_iter()
            .map(|x| x.name)
            .filter(is_valid_name)
            .collect()
    }
}

fn is_valid_name(n: &String) -> bool {
    !n.is_empty() && n != "unknown" && n != "author"
}