mod atom;
mod dir_helper;
mod include_static_helper;
mod simple_template;
mod tree;

use std::{collections::HashMap, fmt, ops::ControlFlow, sync::Arc};

use atom::FeedDir;
use dir_helper::DirHelper;
use handlebars::{handlebars_helper, Handlebars};
use include_static_helper::IncludeStaticHelper;
use serde::Serialize;
use tracing::{error, info_span, instrument};

use crate::{
    config::Config,
    dirs::Dirs,
    fun::seasons::Season,
    sources::Sources,
    vfs::{
        self, AnchoredAtExt, Cd, Content, ContentCache, Dir, DynDir, Entries, HtmlCanonicalize,
        MemDir, Overlay, ToDynDir, VPath, VPathBuf,
    },
};

#[derive(Serialize)]
struct BaseTemplateData<'a> {
    config: &'a Config,
    import_map: String,
    season: Option<Season>,
    dev: bool,
    feeds: Vec<String>,
}

impl<'a> BaseTemplateData<'a> {
    fn new(sources: &'a Sources) -> Self {
        Self {
            config: &sources.config,
            import_map: serde_json::to_string_pretty(&sources.import_map)
                .expect("import map should be serializable to JSON"),
            season: Season::current(),
            dev: cfg!(debug_assertions),
            feeds: sources.treehouse.feeds_by_name.keys().cloned().collect(),
        }
    }
}

fn create_handlebars(site: &str, static_: DynDir) -> Handlebars<'static> {
    let mut handlebars = Handlebars::new();

    handlebars_helper!(cat: |a: String, b: String| a + &b);

    handlebars.register_helper("cat", Box::new(cat));
    handlebars.register_helper("asset", Box::new(DirHelper::new(site, static_.clone())));
    handlebars.register_helper(
        "include_static",
        Box::new(IncludeStaticHelper::new(static_)),
    );

    handlebars
}

#[instrument(skip(handlebars))]
fn load_templates(handlebars: &mut Handlebars, dir: &dyn Dir) {
    vfs::walk_dir_rec(dir, VPath::ROOT, &mut |path| {
        if path.extension() == Some("hbs") {
            if let Some(content) = vfs::query::<Content>(dir, path).and_then(|c| c.string().ok()) {
                let _span = info_span!("register_template", ?path).entered();
                if let Err(err) = handlebars.register_template_string(path.as_str(), content) {
                    error!("in template: {err}");
                }
            }
        }
        ControlFlow::Continue(())
    });
}

struct TreehouseDir {
    dirs: Arc<Dirs>,
    sources: Arc<Sources>,
    handlebars: Arc<Handlebars<'static>>,
    dir_index: DirIndex,
}

impl TreehouseDir {
    fn new(
        dirs: Arc<Dirs>,
        sources: Arc<Sources>,
        handlebars: Arc<Handlebars<'static>>,
        dir_index: DirIndex,
    ) -> Self {
        Self {
            dirs,
            sources,
            handlebars,
            dir_index,
        }
    }

    #[instrument("TreehouseDir::dir", skip(self))]
    fn dir(&self, path: &VPath) -> Vec<VPathBuf> {
        // NOTE: This does not include simple templates, because that's not really needed right now.

        let mut index = &self.dir_index;
        for component in path.segments() {
            if let Some(child) = index.children.get(component) {
                index = child;
            } else {
                // There cannot possibly be any entries under an invalid path.
                // Bail early.
                return vec![];
            }
        }

        index
            .children
            .values()
            .map(|child| child.full_path.clone())
            .collect()
    }

    #[instrument("TreehouseDir::content", skip(self))]
    fn content(&self, path: &VPath) -> Option<Content> {
        let path = if path.is_root() {
            VPath::new_const("index")
        } else {
            path
        };

        self.sources
            .treehouse
            .files_by_tree_path
            .get(path)
            .map(|&file_id| {
                Content::new(
                    "text/html",
                    tree::generate_or_error(&self.sources, &self.dirs, &self.handlebars, file_id)
                        .into(),
                )
            })
            .or_else(|| {
                if path.file_name().is_some_and(|s| !s.starts_with('_')) {
                    let template_name = path.with_extension("hbs");
                    if self.handlebars.has_template(template_name.as_str()) {
                        return Some(Content::new(
                            "text/html",
                            simple_template::generate_or_error(
                                &self.sources,
                                &self.handlebars,
                                template_name.as_str(),
                            )
                            .into(),
                        ));
                    }
                }
                None
            })
    }
}

impl Dir for TreehouseDir {
    fn query(&self, path: &VPath, query: &mut vfs::Query) {
        query.provide(|| Entries(self.dir(path)));
        query.try_provide(|| self.content(path));
    }
}

impl fmt::Debug for TreehouseDir {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("TreehouseDir")
    }
}

/// Acceleration structure for `dir` operations on [`TreehouseDir`]s.
#[derive(Debug, Default)]
struct DirIndex {
    full_path: VPathBuf,
    children: HashMap<VPathBuf, DirIndex>,
}

impl DirIndex {
    #[instrument(name = "DirIndex::new", skip(paths))]
    pub fn new<'a>(paths: impl Iterator<Item = &'a VPath>) -> Self {
        let mut root = DirIndex::default();

        for path in paths {
            let mut parent = &mut root;
            let mut full_path = VPath::ROOT.to_owned();
            for segment in path.segments() {
                full_path.push(segment);
                let child = parent
                    .children
                    .entry(segment.to_owned())
                    .or_insert_with(|| DirIndex {
                        full_path: full_path.clone(),
                        children: HashMap::new(),
                    });
                parent = child;
            }
        }

        root
    }
}

pub fn target(dirs: Arc<Dirs>, sources: Arc<Sources>) -> DynDir {
    let mut handlebars = create_handlebars(&sources.config.site, dirs.static_.clone());
    load_templates(&mut handlebars, &dirs.template);
    let handlebars = Arc::new(handlebars);

    let mut root = MemDir::new();
    root.add(
        VPath::new("feed"),
        ContentCache::new(FeedDir::new(
            dirs.clone(),
            sources.clone(),
            handlebars.clone(),
        ))
        .to_dyn(),
    );
    root.add(VPath::new("static"), dirs.static_.clone());
    root.add(
        VPath::new("robots.txt"),
        Cd::new(dirs.static_.clone(), VPathBuf::new("robots.txt")).to_dyn(),
    );

    let dir_index = DirIndex::new(sources.treehouse.files_by_tree_path.keys().map(|x| &**x));
    let tree_view = TreehouseDir::new(dirs, sources, handlebars, dir_index);

    let tree_view = ContentCache::new(tree_view);
    tree_view.warm_up();
    let tree_view = HtmlCanonicalize::new(tree_view);

    Overlay::new(tree_view.to_dyn(), root.to_dyn())
        .anchored_at(VPath::ROOT.to_owned())
        .to_dyn()
}