use std::{collections::HashMap, path::Path};

use chrono::{DateTime, FixedOffset};
use glob::glob;

use lazy_static::lazy_static;
use pulldown_cmark::{html, Options, Parser};
use regex::Regex;
use serde_derive::{Deserialize, Serialize};
use tokio::fs;

use tracing::{instrument, log::*};

use crate::WebsiteError;

#[derive(Deserialize, Debug, Default)]
pub struct TomlFrontMatter {
    pub title: String,
    pub date: Option<toml::value::Datetime>,
    pub draft: Option<bool>,
    pub aliases: Option<Vec<String>>,
    pub tags: Option<Vec<String>>,
}

#[derive(Serialize, Clone, Debug, Default)]
pub struct Post {
    pub title: String,
    pub date: Option<DateTime<FixedOffset>>,
    pub aliases: Vec<String>,
    pub tags: Vec<String>,
    pub content: String,
    pub slug: String,
    pub absolute_path: String,
}

impl Post {
    pub fn new(slug: String, content: String, fm: TomlFrontMatter) -> Post {
        Post {
            absolute_path: format!("/posts/{}/", slug),
            slug,
            content,
            title: fm.title,
            date: fm
                .date
                .map(|d| DateTime::parse_from_rfc3339(&d.to_string()).expect("bad toml datetime")),
            aliases: fm.aliases.unwrap_or_default(),
            tags: fm.tags.unwrap_or_default(),
        }
    }

    pub fn is_published(&self) -> bool {
        let now = chrono::offset::Local::now();
        if let Some(date) = self.date {
            return date.timestamp() - now.timestamp() <= 0;
        }
        true
    }
}

#[instrument]
pub async fn load_all() -> color_eyre::eyre::Result<HashMap<String, Post>> {
    let mut res = HashMap::<String, Post>::new();
    for path in glob("posts/**/*.md")? {
        let path = path.unwrap();
        debug!("found page: {}", path.display());

        let path = path.to_string_lossy().replace('\\', "/");
        let slug = path
            .trim_start_matches("posts")
            .trim_start_matches('/')
            .trim_start_matches('\\')
            .trim_end_matches(".html")
            .trim_end_matches(".md")
            .trim_end_matches("index")
            .trim_end_matches('\\')
            .trim_end_matches('/');

        let post = load_post(slug).await?;

        res.insert(slug.to_string(), post);
    }
    Ok(res)
}

#[instrument]
pub async fn load_post(slug: &str) -> color_eyre::eyre::Result<Post> {
    debug!("loading post: {slug}");

    let file_path = Path::new("posts").join(slug);

    let content = if let Ok(content) = fs::read_to_string(file_path.with_extension("md")).await {
        content
    } else {
        fs::read_to_string(file_path.join("index.md")).await?
    };

    let (tomlfm, content) = parse_frontmatter(content)?;
    let tomlfm = tomlfm.expect("Missing frontmatter");

    let content = content.map(|c| {
        let options = Options::all();
        let mut content_html = String::new();
        let parser = Parser::new_ext(&c, options);
        html::push_html(&mut content_html, parser);
        content_html
    });

    Ok(Post::new(
        slug.to_string(),
        content.unwrap_or_default(),
        tomlfm,
    ))
}

#[instrument(skip(src))]
fn parse_frontmatter(
    src: String,
) -> color_eyre::eyre::Result<(Option<TomlFrontMatter>, Option<String>)> {
    lazy_static! {
        static ref FRONTMATTER_REGEX: Regex = regex::Regex::new(
            r"^[\s]*\+{3}(\r?\n(?s).*?(?-s))\+{3}[\s]*(?:$|(?:\r?\n((?s).*(?-s))$))"
        )
        .unwrap();
    };

    Ok(if let Some(captures) = FRONTMATTER_REGEX.captures(&src) {
        (
            Some(toml::from_str(captures.get(1).unwrap().as_str())?),
            captures.get(2).map(|m| m.as_str().to_owned()),
        )
    } else {
        (None, Some(src))
    })
}

#[instrument(skip(tera, post))]
pub async fn render_post(tera: &tera::Tera, post: &Post) -> Result<String, WebsiteError> {
    let mut ctx = tera::Context::new();
    ctx.insert("page", &post);

    tera.render("post.html", &ctx).map_err(|e| e.into())
}

#[cfg(test)]
mod tests {
    use tera::Tera;

    #[tokio::test]
    async fn render_all_posts() {
        let tera = Tera::new("templates/**/*").unwrap();
        let posts = super::load_all().await.unwrap();

        for (_slug, post) in posts {
            super::render_post(&tera, &post).await.unwrap();
        }
    }
}