use std::path::PathBuf;

use chrono::NaiveDateTime;
use lazy_static::lazy_static;
use pulldown_cmark::{html, Parser};
use regex::Regex;
use serde::{Deserialize, Deserializer, Serializer};
use serde_derive::{Deserialize, Serialize};

#[derive(Clone, Default, Deserialize, Serialize)]
#[serde(default)]
pub struct Page {
    pub permalink: String,
    pub title: String,
    pub author: String,
    pub description: String,
    pub draft: bool,
    #[serde(deserialize_with = "parse_datetime", serialize_with = "date_to_string")]
    pub date: Option<NaiveDateTime>,

    #[serde(skip_deserializing)]
    pub content: String,
    #[serde(skip_deserializing)]
    pub prev: Option<Box<Page>>,
    #[serde(skip_deserializing)]
    pub next: Option<Box<Page>>,

    #[serde(skip)]
    pub input: PathBuf,
    #[serde(skip)]
    pub output: Option<PathBuf>,
}

impl Page {
    pub fn from(path: PathBuf, content: &[u8]) -> Page {
        let content = String::from_utf8_lossy(&content);
        if !FRONTMATTER_REGEX.is_match(&content) {
            return Page {
                content: markdown_to_html(&content),
                input: path,
                ..Default::default()
            };
        }

        let captures = FRONTMATTER_REGEX.captures(&content).unwrap();

        let mut page: Page = match toml::from_str(&captures[1]) {
            Ok(page) => page,
            Err(e) => {
                warn!("failed to parse frontmatter in `{}`: {}", path.display(), e);
                Page::default()
            }
        };

        if page.permalink == "" {
            page.permalink = "/".to_string() + &path.with_extension("").to_string_lossy();
        } else {
            page.output = Some(PathBuf::from(page.permalink.trim_start_matches('/')));
        }

        page.content = markdown_to_html(&captures[2]);
        page.input = path;
        page
    }
}

lazy_static! {
    static ref FRONTMATTER_REGEX: Regex =
        Regex::new(r"^[[:space:]]*\-\-\-\r?\n((?s).*?(?-s))\-\-\-\r?\n?((?s).*(?-s))$").unwrap();
}

fn markdown_to_html(content: &str) -> String {
    let mut result = String::new();
    html::push_html(&mut result, Parser::new(content));
    result
}

fn parse_datetime<'de, D>(deserializer: D) -> Result<Option<NaiveDateTime>, D::Error>
where
    D: Deserializer<'de>,
{
    let date = if let Ok(date) = toml::value::Datetime::deserialize(deserializer) {
        let date = date.to_string();
        if date.contains('T') {
            chrono::DateTime::parse_from_rfc3339(&date)
                .ok()
                .map(|date| date.naive_local())
        } else {
            chrono::NaiveDate::parse_from_str(&date, "%Y-%m-%d")
                .ok()
                .map(|date| date.and_hms(0, 0, 0))
        }
    } else {
        None
    };
    Ok(date)
}

fn date_to_string<S>(date: &Option<NaiveDateTime>, serializer: S) -> Result<S::Ok, S::Error>
where
    S: Serializer,
{
    if let Some(date) = date {
        serializer.serialize_some(&date.format("%Y-%m-%dT%H:%M:%S").to_string())
    } else {
        serializer.serialize_none()
    }
}