use actix_files::NamedFile;
use actix_web::error::ErrorInternalServerError;
use actix_web::{error, get, http, middleware, web, App, Error, HttpResponse, HttpServer};
use anyhow::anyhow;
use chrono::{DateTime, Local};
use clap::{App as ClapApp, Arg};
use linkify::LinkFinder;
use log::{info, trace};
use percent_encoding::{percent_decode_str, utf8_percent_encode};
use pulldown_cmark::{html, Event, Options, Parser, Tag};
use regex::{Captures, Regex};
use std::collections::HashMap;
use std::fs::File;
use std::io::Read;
use std::net::SocketAddr;
use std::path::{Path, PathBuf};
use std::sync::Mutex;
use std::time::SystemTime;
use std::{env, fs};
use tera::{Context, Tera};

#[derive(Clone)]
struct State {
    garden_dir: PathBuf,
    index_file: Option<String>,
    title: Option<String>,
    server_name: String,
    tera: Tera,
}

struct MutableState {
    garden_cache: Mutex<GardenCache>,
}

#[derive(Clone, Debug)]
struct GardenCache {
    pages: HashMap<String, ParsedPage>,
    files: Vec<PathBuf>,
}

impl Default for GardenCache {
    fn default() -> Self {
        GardenCache {
            pages: HashMap::new(),
            files: vec![],
        }
    }
}

#[derive(Clone, Debug)]
struct ParsedPage {
    timestamp: Option<SystemTime>,
    title: String,
    html: String,
    links: Vec<String>,
}

const VERSION: &str = env!("CARGO_PKG_VERSION");

fn main() -> anyhow::Result<()> {
    let env = env_logger::Env::default().filter_or(env_logger::DEFAULT_FILTER_ENV, "info");
    env_logger::init_from_env(env);

    let app = ClapApp::new("gardenserver")
        .version(VERSION)
        .author("Tomáš Mládek <t@mldk.cz>")
        .arg(Arg::with_name("DIRECTORY").required(true).index(1))
        .arg(
            Arg::with_name("BIND")
                .long("bind")
                .default_value("127.0.0.1:8642")
                .help("address and port to bind the Web interface on")
                .required(true),
        )
        .arg(
            Arg::with_name("INDEX_FILE")
                .takes_value(true)
                .short("i")
                .long("index")
                .help("File to be served at the root."),
        )
        .arg(
            Arg::with_name("TITLE")
                .takes_value(true)
                .short("t")
                .long("title")
                .help("Title of this digital garden."),
        )
        .arg(
            Arg::with_name("SERVER_NAME")
                .takes_value(true)
                .short("u")
                .long("garden-url")
                .help("Hostname of the server of this digital garden (for metadata)."),
        );

    let matches = app.get_matches();

    let directory = Path::new(matches.value_of("DIRECTORY").unwrap());

    info!(
        "Starting GardenServer {} of {}...",
        VERSION,
        directory.display()
    );

    let tera = Tera::new("templates/**/*.html")?;

    let sys = actix::System::new("gardenserver");

    let bind: SocketAddr = matches
        .value_of("BIND")
        .unwrap()
        .parse()
        .expect("Incorrect bind format.");
    info!("Starting server at: {}", &bind);

    let mutable_state = web::Data::new(MutableState {
        garden_cache: Mutex::new(update_garden(directory, GardenCache::default())?),
    });

    let state = State {
        garden_dir: directory.to_path_buf(),
        index_file: matches.value_of("INDEX_FILE").map(|s| s.to_string()),
        title: matches.value_of("TITLE").map(|s| s.to_string()),
        server_name: matches
            .value_of("SERVER_NAME")
            .map_or(matches.value_of("BIND").unwrap().to_string(), |s| {
                s.to_string()
            }),
        tera,
    };

    // Start HTTP server
    HttpServer::new(move || {
        App::new()
            .wrap(middleware::Logger::default())
            .data(state.clone())
            .app_data(mutable_state.clone())
            .service(actix_files::Files::new("/static", "templates"))
            .service(render)
    })
    .bind(&bind)?
    .run();

    Ok(sys.run()?)
}

#[get("{path:.*}")]
async fn render(
    request: web::HttpRequest,
    data: web::Data<State>,
    state: web::Data<MutableState>,
    path: web::Path<String>,
) -> Result<HttpResponse, Error> {
    let mut cache = state.garden_cache.lock().unwrap();
    *cache = update_garden(&data.garden_dir, (*cache).clone())
        .map_err(error::ErrorInternalServerError)?;

    // Redirect to index if path is empty.
    if path.is_empty() {
        let location = match data.index_file.as_ref() {
            Some(index_file) => index_file.clone(),
            None => cache
                .files
                .iter()
                .filter(|f| f.to_str().unwrap().ends_with(".md"))
                .collect::<Vec<&PathBuf>>()
                .first()
                .unwrap_or(&cache.files.first().unwrap())
                .display()
                .to_string(),
        };

        return Ok(HttpResponse::Found()
            .header(http::header::LOCATION, location.as_str())
            .finish());
    }

    let full_path = data.garden_dir.join(path.as_str());

    // Redirect to ".md" version if requested path matches a .md file without the extension
    if !full_path.exists() && Path::new(&format!("{}.md", full_path.to_str().unwrap())).exists() {
        return Ok(HttpResponse::Found()
            .header(http::header::LOCATION, format!("{}.md", path.to_string()))
            .finish());
    }

    if full_path.exists() && !path.ends_with(".md") {
        return Ok(NamedFile::open(full_path)?.into_response(&request)?);
    }

    let filename = full_path
        .components()
        .last()
        .unwrap()
        .as_os_str()
        .to_str()
        .unwrap();

    let normalized_name = normalize_name(filename);

    let mut backlinks: Vec<String> = vec![];
    for (path, page) in cache.pages.iter() {
        if page
            .links
            .iter()
            .any(|link| normalize_name(link.as_str()) == normalized_name)
        {
            backlinks.push(normalize_name(path));
        }
    }

    let page = cache.pages.get(path.as_ref());

    let mut context = Context::new();
    context.insert("version", VERSION);
    context.insert(
        "garden_title",
        data.title.as_ref().unwrap_or(&"Digital Garden".to_string()),
    );
    context.insert("files", &cache.files);
    context.insert(
        "page_title",
        &match page {
            Some(page) => page.title.clone(),
            None => filename.to_string(),
        },
    );
    context.insert(
        "content",
        &match page {
            Some(page) => page.html.clone(),
            None => data
                .tera
                .render("_not_found.html", &Context::new())
                .map_err(ErrorInternalServerError)?,
        },
    );
    context.insert("backlinks", &backlinks);
    context.insert(
        "mtime",
        &match page {
            Some(page) => {
                if let Some(timestamp) = page.timestamp {
                    let mtime: DateTime<Local> = timestamp.into();
                    Some(mtime.format("%c").to_string())
                } else {
                    None
                }
            }
            None => None,
        },
    );
    context.insert("server_name", &data.server_name);
    context.insert("path", &path.to_string());

    Ok(HttpResponse::Ok().body(
        data.tera
            .render("main.html", &context)
            .map_err(ErrorInternalServerError)?,
    ))
}

fn update_garden<P: AsRef<Path>>(
    garden_path: P,
    current: GardenCache,
) -> anyhow::Result<GardenCache> {
    let garden_path = garden_path.as_ref();

    let mut files: Vec<PathBuf> = fs::read_dir(&garden_path)?
        .filter_map(|entry| {
            if let Ok(entry) = entry {
                let path = entry.path();
                if path.is_file() {
                    let stripped_path = path.strip_prefix(&garden_path).unwrap().to_path_buf();
                    if !stripped_path.to_str().unwrap().starts_with('.') {
                        return Some(stripped_path);
                    }
                }
            }
            None
        })
        .collect();
    files.sort();
    files.sort_by_key(|p| {
        println!("{:?}", p);
        match p.extension() {
            None => -1,
            Some(ext) => {
                if ext == "md" {
                    0
                } else {
                    1
                }
            }
        }
    });

    if files.is_empty() {
        return Err(anyhow!("Garden is empty."));
    }

    let mut pages = current.pages;

    let markdown_paths = files
        .iter()
        .filter(|p| p.to_str().unwrap_or("").ends_with(".md"));
    for path in markdown_paths {
        trace!("Loading {} into cache...", path.display());
        let full_path = garden_path.join(path);
        let mtime = full_path.metadata().unwrap().modified().ok();
        if let Some(page) = pages.get(path.to_str().unwrap()) {
            if let (Some(fs_time), Some(last_time)) = (mtime, page.timestamp) {
                if fs_time == last_time {
                    continue;
                }
            }
        }

        let mut file = File::open(&full_path)?;
        let mut file_string = String::new();
        file.read_to_string(&mut file_string)?;
        let markdown_source = preprocess_markdown(file_string);
        let result = GardenParser::parse(&markdown_source);

        pages.insert(
            String::from(path.to_str().unwrap()),
            ParsedPage {
                timestamp: mtime,
                html: result.html,
                links: result.links,
                title: match result.title {
                    Some(title) => title,
                    _ => String::from(
                        path.components()
                            .last()
                            .unwrap()
                            .as_os_str()
                            .to_str()
                            .unwrap_or("???"),
                    ),
                },
            },
        );
    }

    let result = GardenCache { files, pages };
    trace!("{:#?}", result);
    Ok(result)
}

struct GardenParser<'a> {
    parser: Parser<'a>,
    last_nontext_event: Option<Event<'a>>,
    current_top_heading: u32,
    top_heading_text: &'a mut Option<String>,
    links: &'a mut Vec<String>,
}

struct ParseResult {
    html: String,
    title: Option<String>,
    links: Vec<String>,
}

impl<'a> GardenParser<'a> {
    fn parse<S: AsRef<str>>(text: &'a S) -> ParseResult {
        let mut title: Option<String> = None;
        let mut links: Vec<String> = vec![];

        let parser = GardenParser {
            parser: Parser::new_ext(text.as_ref(), Options::all()),
            last_nontext_event: None,
            current_top_heading: 999,
            top_heading_text: &mut title,
            links: &mut links,
        };

        let mut html = String::new();
        html::push_html(&mut html, parser);

        ParseResult { html, title, links }
    }
}

impl<'a> Iterator for GardenParser<'a> {
    type Item = Event<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        let event = self.parser.next();

        if let Some(event) = &event {
            if let Event::Start(Tag::Link(_, str, _)) = &event {
                self.links.push(str.to_string());
            }

            if let Some(Event::Start(Tag::Heading(hl))) = self.last_nontext_event {
                if hl < self.current_top_heading {
                    self.current_top_heading = hl;
                    if let Event::Text(str) = &event {
                        *self.top_heading_text = Some(str.clone().into_string());
                    }
                }
            }

            self.last_nontext_event = Some(event.clone());
        }

        event
    }
}

fn preprocess_markdown(string: String) -> String {
    let double_brackets = Regex::new(r"\[\[(?P<inner>[\w\- .]+)\]\]").unwrap();
    let finder = LinkFinder::new();

    let result = double_brackets
        .replace_all(string.as_str(), |caps: &Captures| {
            format!(
                "[{}]({})",
                &caps[1],
                utf8_percent_encode(&caps[1], percent_encoding::NON_ALPHANUMERIC)
            )
        })
        .to_string();

    let result_vec = Vec::from(result.as_str());
    let start_delims = vec![b'(', b'<'];
    let end_delims = vec![b')', b'>'];
    // link.end() is the first char AFTER the link!
    let links = finder.links(result.as_str()).filter(|link| {
        link.start() == 0
            || link.end() == result.len()
            || !start_delims.contains(&result_vec[link.start() - 1])
            || !end_delims.contains(&result_vec[link.end()])
    });

    let mut offset = 0;
    let mut result_string = result.to_string();
    for link in links {
        let orig = link.as_str();
        let new = format!("<{}>", orig);
        result_string.replace_range((link.start() + offset)..(link.end() + offset), new.as_str());
        offset += new.len() - orig.len();
    }

    result_string
}

fn normalize_name(filename: &str) -> String {
    let decoded = percent_decode_str(filename).decode_utf8_lossy();
    let result = decoded.strip_suffix(".md");
    String::from(result.unwrap_or(filename))
}