use std::sync::Arc;

use axum::{
    extract::{Path, State},
    http::{header, HeaderMap, StatusCode},
    response::{Html, IntoResponse, Redirect, Response},
    routing::get,
    Router,
};

use serde_derive::Serialize;
use tracing::instrument;

use crate::{post::Post, AppState, WebsiteError};

use super::should_return_304;

pub fn router() -> Router<Arc<AppState>> {
    Router::new()
        .route("/tags", get(|| async { Redirect::permanent("/") }))
        .route("/tags/", get(index))
        .route("/tags/:tag", get(redirect))
        .route("/tags/:tag/", get(view))
        .route("/tags/:tag/atom.xml", get(feed))
}

#[derive(Serialize, Debug)]
struct TagContext<'a> {
    title: &'a str,
}

#[instrument(skip(state))]
pub async fn index(State(state): State<Arc<AppState>>) -> Result<Response, WebsiteError> {
    let tags: Vec<_> = state.tags.values().collect();
    let ctx = TagContext { title: "Tags" };

    let mut c = tera::Context::new();
    c.insert("page", &ctx);
    c.insert("tags", &tags);

    let res = state.tera.render("tags_index.html", &c)?;

    Ok((
        StatusCode::OK,
        [(header::LAST_MODIFIED, state.startup_time.to_rfc2822())],
        Html(res),
    )
        .into_response())
}

#[instrument(skip(state))]
pub async fn view(
    Path(tag): Path<String>,
    State(state): State<Arc<AppState>>,
    headers: HeaderMap,
) -> Result<Response, WebsiteError> {
    let mut posts: Vec<&Post> = state
        .posts
        .values()
        .filter(|p| !p.draft && p.is_published() && p.tags.contains(&tag))
        .collect();

    let last_changed = posts.iter().filter_map(|p| p.last_modified()).max();

    if should_return_304(&headers, last_changed) {
        return Ok(StatusCode::NOT_MODIFIED.into_response());
    }

    posts.sort_by_key(|p| &p.date);
    posts.reverse();

    let title = format!("Posts tagged with #{tag}");

    let ctx = TagContext { title: &title };

    let mut c = tera::Context::new();
    c.insert("base_url", &state.base_url.to_string());
    c.insert("tag_slug", &tag);
    c.insert("page", &ctx);
    c.insert("posts", &posts);

    let res = state.tera.render("tag.html", &c)?;

    Ok((
        StatusCode::OK,
        [(
            header::LAST_MODIFIED,
            &last_changed.map_or_else(|| state.startup_time.to_rfc2822(), |d| d.to_rfc2822()),
        )],
        Html(res),
    )
        .into_response())
}

#[instrument(skip(state))]
pub async fn feed(
    Path(slug): Path<String>,
    State(state): State<Arc<AppState>>,
    headers: HeaderMap,
) -> Result<Response, WebsiteError> {
    let tag = state.tags.get(&slug).ok_or(WebsiteError::NotFound)?;

    let mut posts: Vec<&Post> = state
        .posts
        .values()
        .filter(|p| p.is_published() && p.tags.contains(&slug))
        .collect();

    let last_changed = posts.iter().filter_map(|p| p.last_modified()).max();

    if should_return_304(&headers, last_changed) {
        return Ok(StatusCode::NOT_MODIFIED.into_response());
    }

    posts.sort_by_key(|p| &p.date);
    posts.reverse();
    posts.truncate(10);

    Ok((
        StatusCode::OK,
        [
            (header::CONTENT_TYPE, "application/atom+xml"),
            (
                header::LAST_MODIFIED,
                &last_changed.map_or_else(|| state.startup_time.to_rfc2822(), |d| d.to_rfc2822()),
            ),
        ],
        crate::feed::render_atom_tag_feed(tag, &state)?,
    )
        .into_response())
}

#[instrument(skip(state))]
pub async fn redirect(
    Path(slug): Path<String>,
    State(state): State<Arc<AppState>>,
) -> Result<Redirect, WebsiteError> {
    if state.tags.contains_key(&slug) {
        Ok(Redirect::permanent(&format!("/tags/{slug}/")))
    } else {
        Err(WebsiteError::NotFound)
    }
}